Structure and determination apparatus

Abstract

A structure (10) according to the present disclosure is a structure (10) arranged relative to an object (S), the structure including a first layer (11) having a reflection property or a transmission property, with respect to an electromagnetic wave (L1), that changes irreversibly according to a state of the object (S) and a second layer (12) configured to reduce an intensity of the electromagnetic wave (L1) that is transmitted through the first layer (11) and is incident on the second layer (12).

Description

STRUCTURE AND DETERMINATION APPARATUSCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to Japanese Patent Application No. 2023-030444 filed on February 28, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a structure and a determination apparatus.Background

[0003] Conventional technologies for nondestructively measuring the corrosion state of structures with walls and the like are known. For example, Patent Literature (PTL) 1 discloses an apparatus for detecting corrosion induced by a medium in a structure. The apparatus uses a closing disk made of a material that becomes permeable to the medium once the disk is corroded by the medium.

[0004] PTL 1: JP 2006-511812 ASummary

[0005] (Technical Problem) However, it is not easy to determine the state of an object at a difficult-to-access location, such as the interior of the object. In addition, the detection structure including the disk is complex.

[0006] It is an aim of the present disclosure to provide a structure and a determination apparatus that can improve the degree of freedom of the location of state determination with a simple structure. (Solution to Problem)

[0007] A structure according to several embodiments is a structure arranged relative to an object, the structure including a first layer having a reflection property or a transmission property, with respect to an electromagnetic wave, that changes irreversibly according to a state of the object, and a second layer configured to reduce an intensity of the electromagnetic wave that is transmitted through the first layer and is incident on the second layer.

[0008] With this configuration, the degree of freedom of the location of state determination can be improved with a simple structure. This improves the degree of freedom of the target location where the existence of the state of the object is determined. The determination system can, for example, make the determination of the existence of the state of an object even in locations that are environmentally difficult to access or locations where it is difficult to install an electronic device, such as the interior of an object. Wiring and the like for the object thus becomes unnecessary, and nondestructive determination using electromagnetic waves becomes possible.

[0009] In the structure according to an embodiment, the first layer may be configured so that a reflectance of the electromagnetic wave is irreversibly reduced according to the state of the object. This configuration makes it possible for the reflection property of the first layer itself to change before and after the object is submerged, thereby contributing to the process by the determination system to determine the existence of the state of the object. The change in the reflection property of the first layer itself makes it possible for the spectral intensity of electromagnetic waves received by a receiver to change before and after the object is submerged. Therefore, the determination system can easily distinguish whether the object is in a state before or after submersion based on the difference in the spectral intensity.

[0010] In the structure according to an embodiment, the second layer may be configured so that a phase difference between the electromagnetic wave reflected at a first surface on the first layer side and the electromagnetic wave reflected at a second surface opposite the first surface is 180°.

[0011] This configuration enables the second layer to reduce the intensity of the electromagnetic waves transmitted through the first layer and incident on the second layer after the object has been submerged. The second layer thus makes it possible for the spectral intensity of electromagnetic waves received by a receiver to change before and after the object is submerged. Therefore, the determination system can easily distinguish whether the object is in a state before or after submersion based on the difference in the spectral intensity.

[0012] In the structure according to an embodiment, the second layer may be configured to absorb the electromagnetic wave that is incident on the second layer. This configuration enables the second layer more reliably to reduce the intensity of the electromagnetic waves transmitted through the first layer and incident on the second layer after the object has been submerged. The second layer thus more reliably makes it possible for the spectral intensity of electromagnetic waves received by a receiver to change before and after the object is submerged. Therefore, the determination system can more easily distinguish whether the object is in a state before or after submersion based on the difference in the spectral intensity.

[0013] In the structure according to an embodiment, the first layer and the second layer may be stacked adjacent to each other. This further simplifies the sensor structure for detecting the state of the object. The sensor structure is further simplified by the structure being such a simple two-layer structure. Therefore, there is no need to build a complicated structure, and it becomes easier to achieve the determination function by the determination apparatus using the structure.

[0014] In the structure according to an embodiment, the first layer may be formed of a material that corrodes according to the state of the object. This configuration makes it possible for the optical properties, such as the reflection property and the transmission property, of the first layer itself to change before and after the object is submerged, thereby contributing to the process by the determination system to determine the existence of the state of the object. The change in the optical properties of the first layer itself makes it possible for the spectral intensity of electromagnetic waves received by a receiver to change before and after the object is submerged. Therefore, the determination system can easily distinguish whether the object is in a state before or after submersion based on the difference in the spectral intensity.

[0015] In the structure according to an embodiment, the state of the object may include a past submerged state of the object, and the material may include a metal material that corrodes in water. This configuration enables the determination system to determine whether a location where the structure is arranged in the object has been submerged in the past due to water entering the location. By the material forming the first layer including a metal material that corrodes in water, rust can be generated in the first layer after the object is submerged, thereby changing the optical properties of the first layer. Therefore, based on the change in the optical properties in the first layer of the structure, the determination system can indirectly determine whether the object is deteriorating due to moisture at the location where the structure is arranged.

[0016] In the structure according to an embodiment, the structure may be embedded inside the object. This configuration enables the determination system to make the determination of the existence of the state of the object even in locations that are environmentally difficult to access or locations where it is difficult to install an electronic device. Wiring and the like for the object thus becomes unnecessary, and nondestructive determination using electromagnetic waves becomes possible.

[0017] A determination apparatus according to several embodiments includes a controller configured to control transmission of the electromagnetic wave directed towards any one of the aforementioned structures and reception of the electromagnetic wave reflected by the structure, and a determiner configured to compare acquired data obtained from a received electromagnetic wave with reference data to determine existence of the state of the object.

[0018] This enables the determination system to improve the accuracy of the determination process based on a threshold determination regarding the difference between these data. Therefore, based on the difference between the data, the determination system can accurately determine whether the object is deteriorating due to moisture at the location where the structure is arranged.

[0019] In the determination apparatus according to an embodiment, the determiner may be configured to determine the existence of the state of the object by comparing a reflection spectrum of the electromagnetic wave at the structure obtained as the acquired data with a reference spectrum as the reference data. This enables the determination system to improve the accuracy of the determination process based on a threshold determination regarding the difference between these spectra. Therefore, based on the difference between the spectra, the determination system can accurately determine whether the object is deteriorating due to moisture at the location where the structure is arranged. (Advantageous Effect)

[0020] According to the present disclosure, a structure and a determination apparatus that can improve the degree of freedom of the location of state determination with a simple structure can be provided.

[0021] In the accompanying drawings: FIG. 1 is a schematic diagram illustrating an example configuration of a determination system including a structure and a determination apparatus according to an embodiment of the present disclosure; FIG. 2 is a schematic diagram illustrating the configuration and functions of the structure illustrated in FIG. 1; FIG. 3 is a block diagram illustrating an example configuration of the determination apparatus illustrated in FIG. 1; and FIG. 4 is a flowchart illustrating an example of operations of the determination apparatus illustrated in FIG. 1.DETAILED DESCRIPTION

[0022] Embodiments of the present disclosure are mainly described below with reference to the drawings.

[0023] FIG. 1 is a schematic diagram illustrating an example configuration of a determination system 1 including a structure 10 and a determination apparatus 20 according to an embodiment of the present disclosure. The structure 10 is, for example, embedded inside an object S. The determination system 1 determines the existence of a state of the object S while using the structure 10 and the determination apparatus 20. In the present disclosure, the “state of the object S” includes, for example, a past submerged state of the object S. The determination system 1 determines whether a location where the structure 10 is arranged in the object S has been submerged in the past due to water entering the location.

[0024] In the present disclosure, the “object S” includes, for example, objects that transmit electromagnetic waves to some extent, as described below. The object S may be a solid, a liquid, or a gas. Examples of the object S include resin, concrete, and adhesives.

[0025] The determination system 1 includes the structure 10 and the determination apparatus 20. The determination system 1 further includes a transmitter 30 connected to the determination apparatus 20 and a receiver 40 connected to the determination apparatus 20. In the determination system 1 according to an embodiment, the transmitter 30 and the receiver 40 are other constituent elements different from the determination apparatus 20. As illustrated in FIG. 1, the transmitter 30 and the receiver 40 are both arranged facing the structure 10, which is embedded inside the object S. The transmitter 30 and the receiver 40 are positioned symmetrically to each other with respect to the structure 10.

[0026] The transmitter 30 includes, for example, an electromagnetic wave generation source capable of irradiating electromagnetic waves onto the structure 10. The transmitter 30 transmits electromagnetic waves toward the structure 10 so that the structure 10 embedded inside the object S is irradiated by the electromagnetic waves. In the present disclosure, the “electromagnetic waves” include, for example, electromagnetic waves in the frequency range of approximately 100 GHz to several THz. For example, the electromagnetic waves have a frequency in the sub-terahertz band of approximately several hundred GHz. The transmitter 30 includes, for example, an antenna that emits a high-frequency signal as electromagnetic waves and circuitry for generating, amplifying, and filtering the high-frequency signal.

[0027] The receiver 40 receives the electromagnetic waves transmitted by the transmitter 30 and reflected by the structure 10. The electromagnetic waves reflected by the structure 10 include, for example, information on a reflection spectrum indicating the frequency dependence of the reflectance of the electromagnetic waves with respect to the structure 10. The receiver 40 includes, for example, an antenna that receives the electromagnetic waves as a high-frequency signal and circuitry for amplifying and filtering the high-frequency signal.

[0028] FIG. 2 is a schematic diagram illustrating the configuration and functions of the structure 10 illustrated in FIG. 1. Referring primarily to FIG. 2, the configuration and functions of the structure 10 are now described.

[0029] As also illustrated in FIG. 1, the structure 10 is arranged relative to the object S. For example, the structure 10 is embedded inside the object S. The structure 10 has a stacked structure including a plurality of layers. The structure 10 includes, for example, a first layer 11 and a second layer 12 that are stacked adjacent to each other. The first layer 11 is formed on the side of the structure 10 closest to the transmitter 30 and the receiver 40. The first layer 11 is located uppermost in the structure 10 in the arrangement illustrated in FIGS. 1 and 2. The first layer 11 faces the transmitter 30 and the receiver 40 through the object S. The second layer 12 is stacked relative to the first layer 11 on the underside of the first layer 11. The second layer 12 is located lowermost in the structure 10 in the arrangement illustrated in FIGS. 1 and 2.

[0030] The first layer 11 is configured so that the reflection property or the transmission property, with respect to an electromagnetic wave L1 from the transmitter 30, changes irreversibly according to the state of the object S. For example, the first layer 11 is configured so that the reflectance of the electromagnetic wave L1 irreversibly decreases according to the state of the object S. The first layer 11 is, for example, formed of a material that corrodes according to the state of the object S. In the present disclosure, “the material” includes, for example, a metal material that corrodes in water. Examples of metal materials include iron.

[0031] Before the object S is submerged, no rust has been generated on the metal material in the first layer 11, and the metal material maintains its properties as an electrical conductor. In this state, the metal material reflects substantially all of the electromagnetic wave L1, from the transmitter 30, that is incident on a first surface A11 corresponding, for example, to the top surface of the first layer 11. As illustrated in FIG. 2A, the electromagnetic wave L1 transmitted from the transmitter 30 is reflected with a reflectance of substantially 100% upon being incident on the first surface A11 of the first layer 11. An electromagnetic wave L2 as the reflected wave of the electromagnetic wave L1 propagates towards the receiver 40.

[0032] At this time, a second reflection spectrum S2 as a reference spectrum, described below, exhibits a constant spectral intensity independent of frequency. As indicated by the second reflection spectrum S2, before the corrosion of the metal material in the first layer 11, a high reflection intensity is obtained for the electromagnetic wave L1 in the entire frequency band of interest. In the present disclosure, the “second reflection spectrum S2” indicates the frequency dependence of the reflectance of the electromagnetic wave L1 with respect to the structure 10 in the initial state before the reflection property with respect to the electromagnetic wave L1 is irreversibly changed according to the state of the object S. In the graph in FIG. 2, the horizontal axis indicates frequency. The vertical axis indicates the reflectance of the electromagnetic wave L1.

[0033] On the other hand, the metal material configuring the first layer 11 gradually corrodes and rusts when water penetrates to the location where the structure 10 is arranged in the object S, submerging the location. When the metal material in the first layer 11 changes into corrosion products such as ferric oxide and iron oxyhydroxide, the transmission with respect to the electromagnetic wave L1 increases. Upon the metal material in the first layer 11 gradually rusting due to submersion, the metal material begins to exhibit insulating properties and transmits a portion of the electromagnetic wave L1, from the transmitter 30, that is incident on the first surface A11 of the first layer 11.

[0034] As illustrated in FIG. 2B, upon the electromagnetic wave L1 emitted from the transmitter 30 being incident on the first surface A11 of the first layer 11, a portion is transmitted through the first layer 11 to be incident on the second layer 12 formed on the second surface A12 side. The remainder is reflected by the first surface A11 of the first layer 11. An electromagnetic wave L21 as the reflected wave of the electromagnetic wave L1 propagates towards the receiver 40.

[0035] The second layer 12 decreases the intensity of the electromagnetic wave L1 transmitted through the first layer 11 and incident on the second layer 12. The second layer 12 is configured so that the phase difference between the electromagnetic wave L22 reflected at the first surface A21 on the first layer 11 side and the electromagnetic wave L23 reflected at the second surface A22 on the opposite side from the first surface A21 is 180°. The second layer 12 functions like a l / 4 reflective electromagnetic wave absorber. As a result, the electromagnetic wave L22 reflected at the first surface A21 and the electromagnetic wave L23 reflected at the second surface A22 have opposite phase and cancel each other out. In FIG. 2B, arrows are conceptually illustrated for the electromagnetic waves L22 and L23, but in reality, the electromagnetic waves L22 and L23 cancel each other out and do not contribute to the intensity of the reflected wave.

[0036] The second layer 12 functions to irreversibly reduce the reflectance of the electromagnetic wave L1 in a predetermined frequency band throughout the structure 10, according to the state of the object S. The second layer 12 causes the phase to be opposite between the electromagnetic wave L22 and the electromagnetic wave L23 in the predetermined frequency band within the electromagnetic wave L1 transmitted through the first layer 11 due to corrosion caused by submersion of the object S. The second layer 12 causes the electromagnetic wave L22 and the electromagnetic wave L23 to cancel each other out in the predetermined frequency band so as not to contribute to the intensity of the reflected wave. Therefore, the first reflection spectrum S1, which is included as data in the acquired data D1 described below, exhibits a dip in the predetermined frequency band. As indicated by the first reflection spectrum S1, upon corrosion of the metal material in the first layer 11 becoming sufficiently advanced, the reflection intensity of the electromagnetic wave L1 is extremely reduced in the predetermined frequency band. In the present disclosure, the “first reflection spectrum S1” indicates the frequency dependence of the reflectance of the electromagnetic wave L1 with respect to the structure 10.

[0037] Several feature values appear in the first reflection spectrum S1. In the present disclosure, the “feature values” include, for example, parameters that appear in a spectrum such as the first reflection spectrum S1. The feature values include, for example, peak intensity, peak frequency, dip depth, dip frequency, and baseline intensity. The peak intensity is the intensity of the spectrum at the peak frequency. The dip depth is the difference between the baseline intensity and the intensity of the spectrum at the dip frequency. The baseline intensity is the intensity of the baseline of the spectrum and corresponds to the intensity of the spectrum at frequencies other than the peak and its base portion, and the dip and its base portion. Taking the first reflection spectrum S1 illustrated in FIG. 2 as an example, the feature values include the depth of the dip Ld, the dip frequency fd, and the baseline intensity Lb.

[0038] FIG. 3 is a block diagram illustrating an example configuration of the determination apparatus 20 illustrated in FIG. 1. Referring primarily to FIG. 3, an example of the configuration of the determination apparatus 20 illustrated in FIG. 1 is now described.

[0039] The determination apparatus 20 includes, for example, a general purpose electronic device such as a personal computer (PC) or a smartphone. These examples are not limiting, however, and the determination apparatus 20 may be one server apparatus or a plurality of server apparatuses that can communicate with each other, or any other electronic device dedicated to the determination system 1. The determination apparatus 20 includes a controller 21, a calculator 22, a determiner 23, an input / output interface 24, and a memory 25.

[0040] The controller 21 includes one or more processors. In the present disclosure, the “processor” is a general purpose processor or a dedicated processor specialized for particular processing, but these examples are not limiting. The controller 21 is communicably connected with each component of the determination apparatus 20 and controls operations of the determination apparatus 20 overall.

[0041] Additionally, the controller 21 is connected to both the transmitter 30 and the receiver 40. The controller 21 controls the transmission of electromagnetic waves directed at the structure 10 and the reception of electromagnetic waves reflected by the structure 10. The controller 21 controls the transmission of electromagnetic waves towards the structure 10 by controlling the transmitter 30. For example, the frequency and intensity of the electromagnetic waves transmitted by the transmitter 30, the timing of transmission to be on or off, and the turning on or off of the power supply to the transmitter 30 are controlled. The controller 21 controls the reception of electromagnetic waves reflected by the structure 10 by controlling the receiver 40. For example, by turning the receiver 40 on or off, the controller 21 controls the reception timing and the like of the electromagnetic waves received by the receiver 40. For example, the controller 21 controls the power supply to the receiver 40 to be on or off.

[0042] The controller 21 automatically adjusts the position and angle of the transmitter 30, for example, so that predetermined transmission conditions are satisfied. In the present disclosure, the “predetermined transmission conditions” include, for example, a condition such that the electromagnetic wave transmitted by the transmitter 30 is incident at a freely selected angle of incidence with respect to a predetermined reflective surface in the structure 10. For example, the angle of incidence may be a small angle close to zero degrees or may be zero degrees. The transmitter 30 may be set to a position and angle that enable measurement under conditions such that the electromagnetic wave can be considered to be incident on the structure 10 in a perpendicular or substantially perpendicular manner. This configuration is not limiting, and the controller 21 may adjust the position and angle of the transmitter 30 based on setting values inputted by the user using the determination apparatus 20.

[0043] The controller 21 automatically adjusts the position and angle of the receiver 40, for example, so that predetermined reception conditions are satisfied. In the present disclosure, the “predetermined reception conditions” include, for example, a condition such that the electromagnetic wave reflected at a predetermined reflection angle at the aforementioned predetermined reflective surface of the structure 10 is incident on the receiver 40. For example, the reflection angle may match the aforementioned angle of incidence, may be a small angle close to zero degrees, or may be zero degrees. The receiver 40 may be set to a position and angle that enable measurement under conditions such that the electromagnetic wave can be considered to be reflected at the structure 10 in a perpendicular or substantially perpendicular manner. This configuration is not limiting, and the controller 21 may adjust the position and angle of the receiver 40 based on setting values inputted by the user using the determination apparatus 20.

[0044] The controller 21 controls the transmitter 30 to transmit electromagnetic waves in the sub-terahertz band towards the structure 10. For example, the controller 21 causes the transmitter 30 to emit a short pulse of electromagnetic waves of 10 ps to several 10 ps using Time-Domain Spectroscopy (TDS). At this time, the transmitter 30 may emit electromagnetic waves with a predetermined polarization. For example, the transmitter 30 may transmit linearly polarized electromagnetic waves having a P-polarized component or linearly polarized electromagnetic waves having an S-polarized component.

[0045] The controller 21 controls the receiver 40 to acquire pulse signals arranged in a time series from the receiver 40 as a received signal. For example, the controller 21 controls the receiver 40 to receive the aforementioned short pulses of electromagnetic waves, which are in the sub-terahertz band and are reflected by the structure 10, using TDS. The receiver 40 may receive electromagnetic waves with a predetermined polarization in accordance with the electromagnetic waves transmitted from the transmitter 30. For example, the receiver 40 may receive linearly polarized electromagnetic waves having a P-polarized component or linearly polarized electromagnetic waves having an S-polarized component. The controller 21 outputs the received signals acquired from the receiver 40 to the calculator 22.

[0046] The calculator 22 includes one or more processors. The processor may be the same as or different from the processor functioning as the controller 21. The calculator 22 acquires, from the controller 21, the received signals of the electromagnetic waves received by the receiver 40 and performs arithmetic processing based on the received signals.

[0047] The calculator 22 generates various data, as acquired data D1, from the received signals of electromagnetic waves received by the receiver 40. In the present disclosure, the “acquired data D1” includes, for example, the data of the first reflection spectrum S1 illustrated in FIG. 2. The calculator 22 calculates the first reflection spectrum S1 in the frequency domain by, for example, performing Fourier transform processing on a time waveform on the basis of the pulse signal acquired from the receiver 40. The Fourier transform includes, for example, a discrete Fourier transform.

[0048] The determiner 23 includes one or more processors. The processor may be the same as or different from the processor functioning as at least one of the controller 21 and the calculator 22. The determiner 23 determines the existence of a state of the object S by comparing the acquired data D1 obtained from the electromagnetic waves received by the receiver 40 with the reference data D2. The determiner 23 determines the existence of a past submerged state of the object S based on the acquired data D1 and the reference data D2. The determiner 23 acquires the acquired data D1 from the calculator 22. The determiner 23 acquires the reference data D2 from the memory 25.

[0049] The determiner 23 determines the existence of the state of the object S by comparing the first reflection spectrum S1 of the electromagnetic wave at the structure 10, obtained as the acquired data D1, with the reference spectrum as the reference data D2. In the present disclosure, the “reference data D2” includes, for example, the data of the second reflection spectrum S2 illustrated in FIG. 2. The second reflection spectrum S2 corresponds to an example of the reference spectrum.

[0050] The data of the second reflection spectrum S2 is constructed in advance, based on design data, simulation data, measured data, and the like for the transmitter 30, the receiver 40, and the structure 10, and is stored in the memory 25. The measured data is, for example, the data actually measured at the stage when the structure 10 is arranged relative to the object S and the determination apparatus 20, the transmitter 30, and the receiver 40 are arranged relative to the structure 10 and the object S. This yields accurate data for the second reflection spectrum S2, even when accurate prediction or the like from design data and simulation data is difficult.

[0051] The determiner 23 compares the data for the first reflection spectrum S1 obtained by the calculator 22 with the data for the second reflection spectrum S2, stored in the memory 25, as the reference spectrum. The determiner 23 determines the existence of a state of the object S based on the difference between the first reflection spectrum S1 and the second reflection spectrum S2.

[0052] The difference used in the determination includes the difference between feature values. The difference between feature values corresponds to the amount of change in the first reflection spectrum S1 with respect to the second reflection spectrum S2 as a reference spectrum. For example, the determiner 23 determines the existence of the state of the object S based on the difference between at least one of the dip depth Ld, dip frequency fd, and baseline intensity Lb of the first reflection spectrum S1 and the corresponding feature value of the second reflection spectrum S2. For example, the determiner 23 determines the existence of the state of the object S based on the difference between the dip depth Ld of the first reflection spectrum S1 and the corresponding feature value of the second reflection spectrum S2.

[0053] In a case in which the difference is greater than a threshold, the determiner 23 determines that the location where the structure 10 is arranged in the object S has been submerged in the past due to water entering the location. In a case in which the difference is equal to or less than the threshold, the determiner 23 determines that water has not entered the location where the structure 10 is arranged in the object S, and that the location has not been submerged in the past. The threshold is appropriately set by the user, for example, according to the design conditions and the like of the determination system 1, and is stored in advance in the memory 25. For example, the threshold is set in consideration of variation due to the reproducibility of output including the electromagnetic wave intensity and transmission frequency of the transmitter 30 and the reproducibility of reception including the reception intensity and reception frequency of the receiver 40. The aforementioned difference exceeding the threshold means that the difference is larger than this variation and is significant in determining the existence of a past submerged state of the object S.

[0054] If, for example, the dip depth Ld in the first reflection spectrum S1 increases to exceed the threshold while the dip depth is zero in the second reflection spectrum S2, the determiner 23 determines that the location where the structure 10 is arranged in the object S has been submerged in the past. For example, if the dip depth Ld in the first reflection spectrum S1 is smaller than the threshold value and does not differ significantly from the dip depth that is zero in the second reflection spectrum S2, the determiner 23 determines that the location where the structure 10 is arranged in the object S has not been submerged in the past.

[0055] The input / output interface 24 includes one or more interfaces for input to detect user input and acquire input information based on user operations. The input / output interface 24 includes, for example, physical keys, capacitive keys, a touchscreen provided integrally with a display, or a microphone that accepts audio input. The input / output interface 24 accepts commands from the user for the determination apparatus 20.

[0056] The input / output interface 24 includes one or more interfaces for output to output information and notify the user. The input / output interface 24 includes, for example, a display that outputs information as images, a speaker that outputs information as audio, and a lamp that communicates information visually. The input / output interface 24 outputs the determination results from the determiner 23. For example, the input / output interface 24 displays to the user, via the display, whether the object S has been submerged in the past, as determined by the determiner 23. This configuration is not limiting, and the input / output interface 24 may, for example, transmit the determination results from the determiner 23 to an external apparatus, not included in the determination system 1, via a network or the like.

[0057] In addition, the input / output interface 24 may trigger an alarm to notify the user of submersion when it is determined that the object S has been submerged in the past. The input / output interface 24 may trigger the alarm by, for example, lighting a lamp or outputting an alarm sound from a speaker. In this way, the input / output interface 24 can reliably inform the user that the object S has been submerged in the past.

[0058] The memory 25 includes any memory module, including a Hard Disk Drive (HDD), Solid State Drive (SSD), Electrically Erasable Programmable Read-Only Memory (EEPROM), Read-Only Memory (ROM), and Random Access Memory (RAM). The memory 25 may, for example, function as a main memory, an auxiliary memory, or a cache memory. The memory 25 stores any information used for operations of the determination apparatus 20, any information resulting from operations of the determination apparatus 20, and the like.

[0059] For example, the memory 25 stores the acquired data D1 obtained by the calculator 22 from the electromagnetic waves received by the receiver 40. The memory 25 stores the reference data D2 constructed in advance. The memory 25 stores the aforementioned threshold set in advance by the user, for example, according to the design conditions and the like of the determination system 1. The memory 25 stores system programs, application programs, and the like. The memory 25 is not limited to being internal to the determination apparatus 20 and may include an external storage module connected through a digital input / output port or the like, such as universal serial bus (USB).

[0060] FIG. 4 is a flowchart illustrating an example of operations of the determination apparatus 20 illustrated in FIG. 1. With reference to FIG. 4, an example of the basic flow of the processing, executed by the determination apparatus 20, related to a determination method is described.

[0061] Before the determination method is executed by the determination apparatus 20, the transmitter 30 and the receiver 40 are first installed with respect to the object S. The transmitter 30 is installed with respect to the object S so that the electromagnetic waves are irradiated onto the structure 10 embedded in the part of the object S to be measured. The receiver 40 is installed with respect to the object S so that the electromagnetic waves reflected by the structure 10 can be received. The transmitter 30 and the receiver 40 may be installed manually by the user of the determination apparatus 20 or automatically by a machine such as a robot.

[0062] Subsequently, the controller 21 of the determination apparatus 20 automatically adjusts the position and angle of the transmitter 30, for example, so that predetermined transmission conditions are satisfied. The controller 21 automatically adjusts the position and angle of the receiver 40, for example, so that predetermined reception conditions are satisfied. Once the above-described installation, adjustment, and the like related to the transmitter 30 and the receiver 40 are completed, the determination method is executed by the determination apparatus 20.

[0063] In step S100, the controller 21 of the determination apparatus 20 controls the transmission of electromagnetic waves towards the structure 10 by controlling the transmitter 30. For example, the controller 21 causes the electromagnetic waves to be transmitted from the transmitter 30 as a pulse waveform containing a wide range of harmonic components.

[0064] In step S101, the controller 21 of the determination apparatus 20 controls the reception of electromagnetic waves reflected by the structure 10 by controlling the receiver 40.

[0065] In step S102, the controller 21 of the determination apparatus 20 stops the transmission of electromagnetic waves towards the structure 10 by controlling the transmitter 30.

[0066] In step S103, the calculator 22 of the determination apparatus 20 generates the acquired data D1 from the received signal of the electromagnetic waves received by the receiver 40 in step S101. For example, the calculator 22 performs a discrete Fourier transform on the time waveform of the electromagnetic wave measured using the receiver 40 in step S101 and generates the acquired data D1 as spectral data in the frequency domain.

[0067] In step S104, the determiner 23 of the determination apparatus 20 compares the acquired data D1 generated in step S103 with the reference data D2 stored in the memory 25. For example, the determiner 23 calculates the difference between the first reflection spectrum S1 obtained in the calculator 22 and the second reflection spectrum S2. The determiner 23 calculates the difference between the dip depth Ld of the first reflection spectrum S1 and the corresponding feature value of the second reflection spectrum S2, for example.

[0068] In step S105, the determiner 23 of the determination apparatus 20 determines whether the difference in the feature value is greater than a threshold based on the comparison process in step S104. In a case in which the difference is greater than the threshold, the determiner 23 executes the process in step S106. In a case in which the difference is equal to or less than the threshold, the determiner 23 ends the process.

[0069] The determiner 23 of the determination apparatus 20 determines the existence of the state of the object S by the process in step S105. More specifically, the determiner 23 determines that there is a past submerged state of the object S when the difference in the feature value is greater than the threshold. The determiner 23 determines that the location where the structure 10 is arranged in the object S has been submerged in the past due to water entering the location. The determiner 23 determines that there is no past submerged state of the object S when the difference in the feature value is equal to or less than the threshold. The determiner 23 determines that water has not entered the location where the structure 10 is arranged in the object S, and that the location not has been submerged in the past.

[0070] When determining that the difference is greater than the threshold in step S105, the determiner 23 of the determination apparatus 20 outputs the determination result to the input / output interface 24 and causes the input / output interface 24 to trigger an alarm in step S106.

[0071] According to the determination system 1 including the structure 10 and the determination apparatus 20 in an embodiment as described above, the degree of freedom of the location of state determination can be improved with a simple structure. This improves the degree of freedom of the target location where the existence of the state of the object S is determined. The determination system 1 can, for example, make the determination of the existence of the state of the object S even in locations that are environmentally difficult to access or locations where it is difficult to install an electronic device, such as the interior of the object S. Wiring and the like for the object S thus becomes unnecessary, and nondestructive determination using electromagnetic waves becomes possible.

[0072] As a result of the structure 10 having a laminated structure including a first layer 11 and a second layer 12, the sensor structure for detecting the state of the object S is further simplified. The sensor structure is further simplified by the structure 10 having a two-layer structure, for example. Therefore, there is no need to build the structure 10 as a complicated structure, and it becomes easier to achieve the determination function by the determination apparatus 20 using the structure 10. In addition, the manufacturing cost of the structure 10 is reduced.

[0073] The determination system 1 can easily detect the history of water entering into the object S. The user can, in a nondestructive and noncontact manner, confirm whether water has entered the object S in the past, even in locations that are environmentally difficult to access, such as inside solids and in gases. This enables detection of deterioration of the object S due to moisture, even if water enters into the object S from outside and subsequently dries out. For example, in a case in which the object S is an adhesive, it is known that there is a mode of irreversible degradation caused by water. Once the adhesive is submerged in water, the adhesive does not return to its former state but remains degraded, even after subsequently drying. Embedding the structure 10 in the adhesive and the adherend or the like also makes it possible to detect, in a nondestructive manner, the strength degradation or the like of the adhesive due to water.

[0074] By the first layer 11 being configured so that the reflectance of the electromagnetic waves irreversibly decreases in accordance with the state of the object S, the reflection property of the first layer 11 itself can be changed before and after the object S is submerged, thereby contributing to the process by which the determination system 1 determines the existence of the state of the object S. The change in the reflection property of the first layer 11 itself makes it possible for the spectral intensity of electromagnetic waves received by the receiver 40 to change before and after the object S is submerged. Therefore, the determination system 1 can easily distinguish whether the object S is in a state before or after submersion based on the difference in the spectral intensity.

[0075] The second layer 12 is configured so that the phase difference between the electromagnetic wave L22 reflected at the first surface A21 on the first layer 11 side and the electromagnetic wave L23 reflected at the second surface A22 on the opposite side from the first surface A21 is 180°. This configuration enables the second layer 12 to reduce the intensity of the electromagnetic wave L1 transmitted through the first layer 11 and incident on the second layer 12 after the object S has been submerged. The second layer 12 thus makes it possible for the spectral intensity of electromagnetic waves received by the receiver 40 to change before and after the object S is submerged. Therefore, the determination system 1 can easily distinguish whether the object S is in a state before or after submersion based on the difference in the spectral intensity.

[0076] The sensor structure for detecting the state of the object S is further simplified by the first layer 11 and the second layer 12 being stacked adjacent to each other. The sensor structure is further simplified by the structure 10 being such a simple two-layer structure. Therefore, there is no need to build the structure 10 as a complicated structure, and it becomes easier to achieve the determination function by the determination apparatus 20 using the structure 10. In addition, the manufacturing cost of the structure 10 is further reduced.

[0077] By the first layer 11 being formed of a material that corrodes in accordance with the state of the object S, the optical properties, such as the reflection property and transmission property, of the first layer 11 itself can be changed before and after the object S is submerged, thereby contributing to the process by which the determination system 1 determines the existence of the state of the object S. The change in the optical properties of the first layer 11 itself makes it possible for the spectral intensity of electromagnetic waves received by the receiver 40 to change before and after the object S is submerged. Therefore, the determination system 1 can easily distinguish whether the object S is in a state before or after submersion based on the difference in the spectral intensity.

[0078] By the state of the object S including a past submerged state of the object S, the determination system 1 can determine whether a location where the structure 10 is arranged in the object S has been submerged in the past due to water entering the location. By the material forming the first layer 11 including a metal material that corrodes in water, rust can be generated in the first layer 11 after the object S is submerged, thereby changing the optical properties of the first layer 11. Therefore, based on the change in the optical properties in the first layer 11 of the structure 10, the determination system 1 can indirectly determine whether the object S is deteriorating due to moisture at the location where the structure 10 is arranged.

[0079] By the structure 10 being embedded inside the object S, the determination system 1 can, for example, make the determination of the existence of the state of the object S even in locations that are environmentally difficult to access or locations where it is difficult to install an electronic device. Wiring and the like for the object S thus becomes unnecessary, and nondestructive determination using electromagnetic waves becomes possible.

[0080] By the determiner 23 of the determination apparatus 20 determining the existence of the state of the object S by comparing the acquired data D1 with the reference data D2, the determination system 1 can improve the accuracy of the determination process based on a threshold determination for the difference between these data. Therefore, based on the difference between the data, the determination system 1 can accurately determine whether the object S is deteriorating due to moisture at the location where the structure 10 is arranged.

[0081] The determiner 23 of the determination apparatus 20 determines the existence of a state of the object S by comparing the first reflection spectrum S1 with the reference spectrum. This enables the determination system 1 to improve the accuracy of the determination process based on a threshold determination regarding the difference between these spectra. Therefore, based on the difference between the spectra, the determination system 1 can accurately determine whether the object S is deteriorating due to moisture at the location where the structure 10 is arranged.

[0082] The structure 10 is configured by stacking the first layer 11, formed of a metal material that severely corrodes in water, on the second layer 12 that functions like a l / 4 reflective electromagnetic wave absorber for frequencies in the sub-terahertz band. This configuration suppresses the influence of a portion of the object S that may form a shield, as a result of the structure 10 being embedded inside the object S, thus enabling the determination system 1 to achieve highly sensitive, nondestructive detection of submersion. The determination system 1 uses the structure 10 as a marker that is sensitive to frequencies in the sub-terahertz band, in which electromagnetic waves are highly transmissible through the object S. This enables the determination system 1 to improve the transmission of electromagnetic waves through the material of the object S, suppress the effect of thick shielding, and easily execute the determination process.

[0083] The use of the second layer 12, which functions like a l / 4 reflective electromagnetic wave absorber in a predetermined frequency band, makes it possible to generate a dip within the first reflection spectrum S1 in the predetermined frequency band. Therefore, by acquiring such a first reflection spectrum S1, the determination system 1 can suppress the influence of thickness variation of the object S that acts as a shield.

[0084] The determination system 1 can separate the decrease in electromagnetic wave intensity based on absorption of electromagnetic waves in the object S from the decrease in electromagnetic wave intensity based on the structure 10. The former depends on the thickness of the object S from the surface of the object S to the location where the structure 10 is arranged. The decrease in electromagnetic wave intensity based on absorption of electromagnetic waves caused by the thickness of the object S appears as a decrease in the baseline intensity in the reflection spectrum. The decrease in electromagnetic wave intensity based on the structure 10 appears as an increase in the depth of the dip in the reflection spectrum. Therefore, even if the thickness of the object S acting as a shield varies, only the baseline intensity fluctuates, with little effect on the dip depth. By acquiring the first reflection spectrum S1, which exhibits frequency dependence, instead of performing measurement at a single frequency, the determination system 1 can accurately determine the existence of a state of the object S based on the depth of the dip, even if the baseline intensity fluctuates.

[0085] It will be clear to a person of ordinary skill in the art that the present disclosure may be implemented in certain ways other than the above embodiments without departing from the spirit or essential features thereof. Accordingly, the above explanation merely provides examples that are in no way limiting. The scope of the present disclosure is to be defined by the appended claims, not by the above explanation. Among all changes, various changes that are within the range of equivalents are considered to be included therein.

[0086] For example, the shape, size, arrangement, orientation, and number of the above-described components are not limited to the above explanation or the drawings. The shape, size, arrangement, orientation, and number of each component may be selected freely as long as the functions of the component can be achieved. The constituent elements of the determination system 1 in the drawings are illustrated as functional concepts. The specific form of each constituent element is not limited to the form in the drawings.

[0087] For example, the functions and the like included in the various configurations and steps may be reordered in any logically consistent way. Furthermore, components or steps may be combined into one or divided.

[0088] For example, the present disclosure may also be embodied as a program containing a description of the processing for achieving the functions of the above-described determination apparatus 20 or a storage medium with the program recorded thereon. Such embodiments are also to be understood as falling within the scope of the present disclosure.

[0089] In the above embodiment, the determination apparatus 20 has been described as executing the determination process based on the irreversible decrease in the reflectance of the electromagnetic wave L1 at the first layer 11 according to the state of the object S, but this configuration is not limiting. The determination apparatus 20 may execute the determination process based on the transmittance of the electromagnetic wave L1 with respect to the structure 10 instead of or in addition to the reflectance of the electromagnetic wave L1 with respect to the structure 10. For example, the determination apparatus 20 may execute the determination process based on information on the transmission spectrum indicating the frequency dependence of the transmittance of the electromagnetic waves transmitted through the structure 10, instead of or in addition to the electromagnetic waves reflected by the structure 10.

[0090] In the above embodiment, a decrease in reflectance is provided as an example of the irreversible change in the reflection property in the first layer 11 according to the state of the object S, but this example is not configuration is not limiting. The irreversible change in the reflection property may include an increase in reflectance.

[0091] In the above embodiment, the second layer 12 has been described as being configured so that the phase difference between the electromagnetic wave L22 reflected at the first surface A21 on the first layer 11 side and the electromagnetic wave L23 reflected at the second surface A22 on the opposite side from the first surface A21 is 180°, but this configuration is not limiting. Instead of or in addition to functioning as a l / 4 reflective electromagnetic wave absorber, the second layer 12 may also absorb the incident electromagnetic wave L1. For example, the second layer 12 may absorb the electromagnetic wave L1 while converting the electromagnetic wave L1 into heat in a predetermined frequency band or in the entire frequency band.

[0092] This configuration enables the second layer 12 more reliably to reduce the intensity of the electromagnetic wave L1 transmitted through the first layer 11 and incident on the second layer 12 after the object S has been submerged. The second layer 12 thus more reliably makes it possible for the spectral intensity of electromagnetic waves received by the receiver 40 to change before and after the object S is submerged. Therefore, the determination system 1 can more easily distinguish whether the object S is in a state before or after submersion based on the difference in the spectral intensity.

[0093] In the above embodiment, the second layer 12 has been described as causing the electromagnetic wave L22 and the electromagnetic wave L23 to cancel each other out in the predetermined frequency band so as not to contribute to the intensity of the reflected wave, but this configuration is not limiting. The second layer 12 may cause the electromagnetic wave L22 and the electromagnetic wave L23 to cancel each other out in the entire frequency band so as not to contribute to the intensity of the reflected wave.

[0094] In the above embodiment, the first layer 11 and the second layer 12 have been described as being stacked adjacent to each other, but this configuration is not limiting. The first layer 11 and the second layer 12 need not be stacked adjacent to each other. The structure 10 may have a laminated structure with three or more layers, with an intermediate layer between the first layer 11 and the second layer 12.

[0095] In the above embodiment, the first layer 11 has been described as being formed of a material that corrodes in response to the state of the object S, but this configuration is not limiting. The first layer 11 may be formed of a material that exhibits any other state change different from corrosion, as long as the reflection property or the transmission property with respect to the electromagnetic wave L1 irreversibly changes according to the state of the object S.

[0096] In the above embodiment, the state of the object S has been described as including the past submerged state of the object S, but this configuration is not limiting. The state of the object S may, for example, include a past increased temperature state of the object S. In this case, the material may be a material that exhibits corrosion or other state changes due to increased temperature instead of a metal material that corrodes in water.

[0097] In the above embodiment, the structure 10 has been described as being embedded within the object S, but this configuration is not limiting. The structure 10 may be placed on the surface of the object S or placed in a recess that is recessed from the surface of the object S. In a case in which the object S is adhesive, the structure 10 may be arranged inside the adherend of the adhered member, arranged inside the adhesive itself, or arranged on the adhesive interface.

[0098] In the above embodiment, the determiner 23 has been described as determining the existence of a state of the object S by comparing the first reflection spectrum S1 with the reference spectrum, but this configuration is not limiting. The determiner 23 may determine the existence of a state of the object S by detecting a change in the intensity of electromagnetic waves at a single frequency with the receiver 40, instead of or in addition to the spectrum-based determination. The determiner 23 may determine the existence of a state of the object S by comparing the intensity of the electromagnetic wave at two points, i.e., the dip frequency and a frequency on the baseline, instead of or in addition to the spectrum-based determination.

[0099] In the above embodiment, the reference spectrum has been described as the second reflection spectrum S2 in the initial state before the reflection property with respect to the electromagnetic wave L1 irreversibly changes according to the state of the object S, but this configuration is not limiting. The reference spectrum may be a reflection spectrum measured after corrosion of the first layer 11 due to submersion of the structure 10.

[0100] In the above embodiment, the determiner 23 has been described as determining the existence of the state of the object S based on the difference between the dip depth Ld of the first reflection spectrum S1 and the corresponding feature value of the second reflection spectrum S2, but this configuration is not limiting. In a case in which the reflection property varies uniformly over the entire frequency band, the determiner 23 may determine the existence of a state of the object S based on the difference from the baseline intensity Lb.

[0101] In the above embodiment, the controller 21 of the determination apparatus 20 has been described as causing electromagnetic waves to be emitted from the transmitter 30 in pulse form, but this configuration is not limiting. The controller 21 may also cause electromagnetic waves to be emitted from the transmitter 30 continuously with a constant signal strength.

[0102] In the above embodiment, the transmitter 30 and the receiver 40 have been described as other constituent elements different from the determination apparatus 20, but this configuration is not limiting. The transmitter 30 and the receiver 40 may be constituent elements of the determination apparatus 20.

[0103] Some embodiments of the present disclosure are exemplified below. It should be noted that the embodiments of the present disclosure are not, however, limited to these examples. [Appendix 1] A structure arranged relative to an object, the structure comprising: a first layer having a reflection property or a transmission property, with respect to an electromagnetic wave, that changes irreversibly according to a state of the object; and a second layer configured to reduce an intensity of the electromagnetic wave that is transmitted through the first layer and is incident on the second layer. [Appendix 2] The structure according to appendix 1, wherein the first layer is configured so that a reflectance of the electromagnetic wave is irreversibly reduced according to the state of the object. [Appendix 3] The structure according to appendix 1 or 2, wherein the second layer is configured so that a phase difference between the electromagnetic wave reflected at a first surface on the first layer side and the electromagnetic wave reflected at a second surface opposite the first surface is 180°. [Appendix 4] The structure according to any one of appendices 1 to 3, wherein the second layer is configured to absorb the electromagnetic wave that is incident on the second layer. [Appendix 5] The structure according to any one of appendices 1 to 4, wherein the first layer and the second layer are stacked adjacent to each other. [Appendix 6] The structure according to any one of appendices 1 to 5, wherein the first layer is formed of a material that corrodes according to the state of the object. [Appendix 7] The structure according to appendix 6, wherein the state of the object includes a past submerged state of the object, and the material includes a metal material that corrodes in water. [Appendix 8] The structure according to any one of appendices 1 to 7, wherein the structure is embedded inside the object. [Appendix 9] A determination apparatus comprising: a controller configured to control transmission of the electromagnetic wave directed towards the structure according to any one of appendices 1 to 8 and reception of the electromagnetic wave reflected by the structure; and a determiner configured to compare acquired data obtained from a received electromagnetic wave with reference data to determine existence of the state of the object. [Appendix 10] The determination apparatus according to appendix 9, wherein the determiner is configured to determine the existence of the state of the object by comparing a reflection spectrum of the electromagnetic wave at the structure obtained as the acquired data with a reference spectrum as the reference data.

[0104] 1 Determination system 10 Structure 11 First layer 12 Second layer 20 Determination apparatus 21 Controller 22 Calculator 23 Determiner 24 Input / output interface 25 Memory 30 Transmitter 40 Receiver A11 First surface A12 Second surface A21 First surface A22 Second surface D1 Acquired data D2 Reference data fd Dip frequency Lb Baseline intensity Ld Dip depth L1, L2, L21, L22, L23 Electromagnetic wave S Object S1 First reflection spectrum S2 Second reflection spectrum

Claims

1. A structure arranged relative to an object, the structure comprising: a first layer having a reflection property or a transmission property, with respect to an electromagnetic wave, that changes irreversibly according to a state of the object; and a second layer configured to reduce an intensity of the electromagnetic wave that is transmitted through the first layer and is incident on the second layer.

2. The structure according to claim 1, wherein the first layer is configured so that a reflectance of the electromagnetic wave is irreversibly reduced according to the state of the object.

3. The structure according to claim 1 or 2, wherein the second layer is configured so that a phase difference between the electromagnetic wave reflected at a first surface on the first layer side and the electromagnetic wave reflected at a second surface opposite the first surface is 180°.

4. The structure according to claim 1 or 2, wherein the second layer is configured to absorb the electromagnetic wave that is incident on the second layer.

5. The structure according to claim 1 or 2, wherein the first layer and the second layer are stacked adjacent to each other.

6. The structure according to claim 1 or 2, wherein the first layer is formed of a material that corrodes according to the state of the object.

7. The structure according to claim 6, wherein the state of the object includes a past submerged state of the object, and the material includes a metal material that corrodes in water.

8. The structure according to claim 1 or 2, wherein the structure is embedded inside the object.

9. A determination apparatus comprising: a controller configured to control transmission of the electromagnetic wave directed towards the structure according to claim 1 or 2 and reception of the electromagnetic wave reflected by the structure; and a determiner configured to compare acquired data obtained from a received electromagnetic wave with reference data to determine existence of the state of the object.

10. The determination apparatus according to claim 9, wherein the determiner is configured to determine the existence of the state of the object by comparing a reflection spectrum of the electromagnetic wave at the structure obtained as the acquired data with a reference spectrum as the reference data.

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