1246 results about "Attenuation coefficient" patented technology

A system and method for tomographic image reconstruction using truncated limited-angle projection data that allows exact interior reconstruction (interior tomography) of a region of interest (ROI) based on the linear attenuation coefficient distribution of a subregion within the ROI, thereby improving image quality while reducing radiation dosage. In addition, the method includes parallel interior tomography using multiple sources beamed at multiple angles through an ROI and that enables higher temporal resolution.

A device includes source and detector sensors. In a specific implementation, the device has two near detectors, two far detectors, and two sources. The two near detectors are arranged closer to the two sources than the two far detectors. A light-diffusing layer covers the two near detectors. The device may be part of a medical device that is used to monitor or measure oxygen saturation levels in a tissue. In a specific implementation, light is transmitted into the tissue and received by the detectors. An attenuation coefficient is first calculated for a shallow layer of tissue. The attenuation coefficient is then used to calculate an attenuation coefficient for a deep layer of tissue.

Aspects of this invention include a downhole tool having first and second radially offset ultrasonic standoff sensors and a controller including instructions to determine at least one of a drilling fluid acoustic velocity and a drilling fluid attenuation coefficient from the reflected waveforms received at the standoff sensors. The drilling fluid acoustic velocity may be determined via processing the time delay between arrivals of a predetermined wellbore reflection component at the first and second sensors. The drilling fluid attenuation coefficient may be determined via processing amplitudes of the predetermined wellbore reflection coefficients. The invention advantageously enables the acoustic velocity and attenuation coefficient of drilling fluid in the borehole annulus to be determined in substantially real-time.

The invention relates to a low-attenuation single mode optical fiber used in an optical fiber communication system. The single mode optical fiber comprises a core layer and a wrapping layer. The single mode optical fiber is characterized in that the refractive index distribution n (r) of the core layer and the g-type refractive index distribution of the core layer meet the formula: n (r)=n0*[1-2*delta 1*(r/R1)*g]*1/2 (r<=R1), the delta 1 of the core layer ranges from -0.05% to +0.05%, g ranges from 10 to 30, and the radius R1 of the core layer ranges from 4.0 microns to 5.0 microns; the wrapping layer sequentially comprises an inner wrapping layer, a middle wrapping layer and an outer wrapping layer from inner to outer, the delta 2 of the inner wrapping layer ranges from -0.3% to -0.45%, the radius R2 ranges from 20 microns to 30 microns, and the delta 3 of the middle wrapping layer is larger than delta 2, the numerical relationship between the relative refraction difference and the radius of the middle wrapping layer and the relative refraction difference and the radius of the inner wrapping layer is V=(R3-R2)*(delta 3-delta 2), and V ranges from 0.5*10-2-micron% to 7*10-2-micron%. The attenuation coefficient, at the 1550-nanometer position, of the optical fiber is smaller than or equal to 0.180dB/km. The low-attenuation single mode optical fiber is low in optical fiber loss, good in manufacturing technology, low in cost and suitable for scale production.

A diagnostic imaging system includes a high frequency electromagnetic energy source that emits a beam of high frequency electromagnetic energy toward an object to be imaged, a detector that receives high frequency electromagnetic energy emitted by the high frequency electromagnetic energy source, and a data acquisition system (DAS) operably connected to the detector. A computer is operably connected to the DAS and is programmed to generate corresponding sets of projection values for three or more energy spectra through employment of attenuation coefficients of three or more basis materials to simulate responses of the diagnostic imaging system to a plurality of lengths of the three or more basis materials wherein the three or more basis materials comprise two or more non K-edge basis materials and one or more K-edge basis materials.

In one embodiment, a variable attenuator is disclosed having an attenuation circuit and a control circuit. The attenuation circuit may include a first series connected attenuation circuit segment and a shunt connected attenuation circuit segment, as well as additional attenuation circuit segments. Each attenuation circuit segment includes a stack of transistors that are coupled to provide the attenuation circuit segment with a variable impedance level having a continuous impedance range. In this manner, the control circuit may be operably associated with the stack of transistors in each attenuation circuit segment to control the variable attenuation level of the variable attenuator.

The present technique provides for the generation of density maps using one or more basis material decomposition tables or functions. The basis material decomposition tables or functions are generated by simulating the system response to various lengths of basis materials using component characteristics of the CT system as well as the attenuation coefficient for the desired basis material. Measured projection data may be processed using the basis material decomposition tables or functions to provide a set of density line-integral projections that may be reconstructed to form a density map or image.

There is disclosed a damping coefficient switching-type hydraulic damper that may automatically switch a damping coefficient without needing supply of energy from the outside at all, and also may always surely exert an energy absorption capacity greater than that of a typical hydraulic damper. While a piston (3) is moving in a direction A, a mechanical drive means (30) composed of a straight gear (31) and a crank mechanism (31) allows an on-off control operation valve (11), that is, a flow regulating valve (10) to be placed in a closed state, and a damping coefficient is switched to a maximum value Cmax. When a movement of the piston (3) is turned in a direction B at a left-side maximum point of amplitude, the mechanical drive means (30) works to once open the flow regulating valve (10) to perform elimination of a load, so that the damping coefficient is switched to a minimum value (Cmin). When the piston (3) further moves in the direction B, the mechanical drive means (30) works to close the flow regulating valve (10) again, and the damping coefficient is returned to the maximum value (Cmax). Similar working to the above is also applied to a right-side maximum point of amplitude, and seismic response control is attained with repetition of the above operations.

A display device comprises a frame buffer which time-divides a frame displaying one picture into multiple sub-frames, an attenuation signal generating circuit which generates an attenuation signal by dividing the inputted luminosity signal by the designated attenuation coefficient, and a signal switching circuit which inputs luminosity signals before division to the antecedent sub-frame in the relevant frame, at the same time, inputs the above-mentioned attenuation signals after division to the subsequent sub-frame. Consequently, such a hold type display device is realized as is able to control the lowering of the picture brightness, as well as, prevent a moving picture from being unclear, blurred or disordered.

The invention discloses an attenuation filter-based metal artifact removing mixed reconstruction method for CT images. When a CT acquires data, if a scanned object contains a metal object with high absorption coefficients which comprises a tissue attenuation coefficient and a metal attenuation coefficient to cause projection data jump, the scanned object is considered to be destructive and should be corrected; thus, the metal artifact is greatly weakened during FPB reconstruction. The method comprises the following steps: after determining a metal projection area, performing adaptive attenuation adjustment and filter on the determined metal area; reconstructing an entire image through the FBP, performing EM iterative reconstruction on the metal area by using the primary projection data, and correcting the metal area after the adaptive attenuation filter and reconstruction; and compensating the metal projection area. The numerical simulation CT experiments prove that the method can effectively remove metal artifacts and well keep the information of the metal and the surrounding tissue of the metal. Particularly under the condition of multiple metal objects, the method has low calculation complexity and high practical value.

A 3-D graphics accelerator for performing lighting operations using operands within a given fixed point numeric range. The 3-D graphics accelerator includes a first computational unit which is configured to compute a value of an attenuation factor usable for performing said lighting operation for local lights. The attenuation factor is represented in floating point format. The first computational unit is also configured to represent the attenuation factor in an intermediate format including a first intermediate value (a scaled attenuation factor value within the given fixed point numeric range), and a second intermediate value (a shift count usable to convert the scaled attenuation factor value back to the original attenuation factor value). The 3-D graphics accelerator further includes a lighting unit coupled to said first computational unit. The first computational unit is further configured to convey the intermediate representation of the attenuation factor to the lighting unit. The lighting unit performs lighting calculations in fixed point, using operands within the given numeric range (such as the scaled attenuation factors). The lighting unit generates intermediate color values as a result of these lighting calculations. The lighting unit then uses the shift count value to shift the intermediate color values by an appropriate amount, thereby generating a final color value. The lighting unit clamps said final color value to a predetermined maximum color value in response to said final color value exceeding said predetermined maximum color value.

A reflective member is fixedly or movably provided near the pupil plane of a projection optical system with which a projection exposure apparatus is equipped. A collimated measuring beam with an exposure wavelength is incident from the object plane side or image plane side of the projection optical system, and the intensity of the beam reflected by the reflective member is detected photoelectrically to measure a value corresponding to the attenuation factor (transmissivity or reflectivity) of the projection optical system or the variation with time of the attenuation factor (transmissivity or reflectivity) of the projection optical system. In accordance with the measurement results, the exposing conditions when a photosensitive substrate is exposed are corrected to avoid the deterioration of the exposure control precision due to the variation of the attenuation factor (transmissivity variation or reflectivity variation) which is caused in the projection optical system and illumination optical system of a projection exposure apparatus which uses ultraviolet illumination light.

A method is provided for conducting an electromagnetic induction survey of a geological formation penetrated by a borehole lined with a conductive casing. The method includes positioning a transmitter in the borehole, whereby the transmitter generates a transmitter magnetic moment, and positioning a distant receiver external of the borehole to detect a magnetic field induced by the transmitter, whereby the distant receiver is disposed across part of the formation from the borehole. Furthermore, an auxiliary receiver is positioned in the borehole proximate the transmitter to detect a magnetic field induced by the transmitter and attenuated by the conductive casing. Subsequently, a first casing attenuation factor that is applicable to the magnetic field measured by the auxiliary receiver is determined from a ratio of the measured magnetic field at the auxiliary receiver and the transmitter magnetic moment. A second casing attenuation factor applicable to the measurement of the magnetic field at the distant receiver is determined from a non-linear relationship (e.g., a power law relationship) between the first casing attenuation factor and the second attenuation factor, wherein the second attenuation factor is less than the first attenuation factor. Then, a formation attenuation factor applicable to the measured magnetic field at the distant receiver is determined from a relationship between the magnetic moment of the transmitter, the second casing attenuation factor, and the measured magnetic field at the distant receiver. Finally, the method correlates the determined value of the formation attenuation factor to a resistivity characteristic of the formation between the distant receiver and the transmitter.

The invention discloses a model parameter training method and device, a server and a storage medium, which belongs to the technical field of information. The method comprises the steps that an initialparameter value and a sample set of a model parameter of a target model are acquired; the first gradient of the model parameter is calculated according to the initial parameter value and the sample set; iterative quantization processing is carried out on the first gradient to acquire a quantized second gradient, wherein the iterative quantization processing is quantization processing carried outbased on an error cumulative value corresponding to the t-1-th iteration round in the t-th iteration round, and the error cumulative value is a quantization error cumulative value calculated based ona preset time attenuation coefficient; and the quantized second gradient is transmitted to a primary computing node, wherein the quantized second gradient is used to instruct the primary computing node to update the initial parameter value according to the quantized second gradient to acquire an updated parameter value. According to the embodiment of the invention, a quantization error correctionmethod is used to quantize and compress the first gradient of the model parameter, which reduces the communication cost and network overhead of gradient transmission.

The invention discloses a method for iterating and reconstructing a double-energy-spectrum CT image. The method is used for reconstructing a base material density image of a measured object and comprises the following steps of (1) selecting a calibration model body containing tow types of different base materials according to the size of a material of the measured object; measuring the model body through a double-energy-spectrum CT system, and calibrating a double-energy-spectrum multi-color orthographic projection equation presenting a curvilinear relationship between a multi-color projection value and base material thickness combination; (2) collecting double-energy-spectrum multi-color projection data of the measured object by utilizing the double-energy-spectrum CT system; (3) constructing a iterative scheme according to the calibrated multi-color orthographic projection equation, and iterating and reconstructing the double-base-material density image of the measured object through comparison with the practically measured multi-color projection data and addition of a physical constraint condition. Compared with the existing method, the method for iterating and reconstructing the double-energy-spectrum CT image has the advantages that the high energy spectrum and the low energy spectrum of the double-energy-spectrum CT system and an attenuation coefficient of the base materials do not need to be detected in advance, and meanwhile the method is applied to the situation that the high energy spectrum and the low energy spectrum are matched with each other or not in geometry.

Provided is a surface light emitter that supplies light using a light guide method, and ensures transparency by lowering a haze value in a thickness direction at the time when a light source is turned off, and enables highly efficient light emission by using plate-surface transversal radiant emitted light at the time when the light source is on. A surface light emitter (2) including light diffusing particles guides light in a length direction of the light guide while scattering the light in the thickness direction of the light guide while scattering the light in the thickness direction of the light guide, and a calculated value (m⁻¹/%) obtained by dividing a luminance attenuation coefficient E (m⁻¹) by a haze value (%) per 5 (mm) thickness of the light guide is greater than or equal to 0.55 (m⁻¹/%) and less than or equal to 10.0 (m⁻¹/%).

The invention relates to an ocean spilt oil film thickness hyperspectral remote sensing estimation method based on a parameter lookup table and belongs to the field of ocean environment monitoring research. The method includes the steps of obtaining and pre-processing standard oil film thickness continuous change hyperspectral data by designing a simulation experiment; obtaining and pre-processing ocean spilt oil satellite remote sensing data; resampling a standard oil film spectrum based on a satellite sensor performance index; normalizing spectral reflectivity; building an oil film thickness optical calculating model; building an attenuation parameter lookup table; normalizing the reflectivity of satellite data and conducting mask treatment; inquiring and building an optimal wave band of the satellite data and relevant parameters; and calculating the oil film thickness in the satellite data through the parameter lookup table and the optical model. Compared with a traditional observation means, by means of the ocean spilt oil film thickness hyperspectral remote sensing estimation method, field workload is less, the thickness of the spilt oil film can be quantized, the thickness of an oil film in a spilt oil area can be calculated without entering an ocean spilt oil pollution area, and requirements of ocean split oil emergency monitoring and evaluation can be met.

The invention discloses a CT (Computed Tomography) value correcting method for cone-beam CT. The CT value correcting method comprises the following steps: scanning air, a water phantom and a bone tissue body phantom under different scanning conditions to respectively obtain projection data; reestablishing an image; removing noise and artifacts by adopting a polynomial fitting method based on a template image; selecting a plurality of interested regions and calculating a mean value of an attenuation coefficient and a standard deviation of the attenuation coefficient; obtaining the value range of the attenuation coefficient and taking the attenuation coefficient of maximum occurrence probability; fitting the attenuation coefficients of the air, the water phantom and the bone tissue body phantom under the different scanning conditions with corresponding ideal CT values to obtain respective fitting curves; performing CT scanning and image reestablishment on a scanned material; obtaining a CT value image according to a material attenuation coefficient image and a fitting curve and finishing the CT value correction. According to the CT value correcting method disclosed by the invention, image noise and artifact can be effectively reduced, the reestablished image of single material reaches the uniformity to the great degree, the precision of the attenuation coefficient of the material becomes higher and further high accuracy for the fitting of the curve of the CT value and the material attenuation coefficient is realized.