2231 results about "Wave crest" patented technology

An article of footwear including an upper and a sole assembly secured to the upper and including a support assembly having an upper member and a lower member spaced from the upper member. A first layer is positioned beneath and in contact with the upper member and has a wave shaped profile with a plurality of first wave crests and first wave troughs. A second layer is positioned above the lower member and has a wave shaped profile with a plurality of second wave crests and second wave troughs.

An article of footwear including an upper and a sole assembly secured to the upper and including a support assembly having an upper member and a lower member spaced from the upper member. A first layer is positioned beneath and in contact with the upper member and has a wave shaped profile with a plurality of first wave crests and first wave troughs. A second layer is positioned above the lower member and has a wave shaped profile with a plurality of second wave crests and second wave troughs.

The invention discloses a prediction and evaluation technology of 3D seismic optimum time window river channel sand body reservoirs, belongs to the technical field of the prediction and evaluation of the 3D seismic reservoirs, and aims at solving technical problem that the river channel predictive resolution of the traditional methods is not enough. The technical proposal is as follows: the 3D visualization scanning is performed on each reservoir at the interval of 1-2ms, the optimum time window is determined according to the scope shown by the target river channel, the corresponding subfield is cut out, clairvoyance and scanning are carried out on the time window properties, such as root-mean-square amplitude, wave impedance and the like, auto-tracing is performed, top surface and bottom surface are picked up, a time isopach map is calculated and converted into a sand body isopach map, a top surface structure diagram is formed by time-depth conversion, and the reservoir physical properties are evaluated by curve reconstruction, thus realizing the prediction and evaluation of the plane morphology, longitudinal thickness and the reservoir physical properties of the river channel sand body. The method adopts the optimum time window to effectively inhibit interference, is applicable to various data volumes, and can effectively predict and evaluate a thin river channel sand body with the thickness far less than 1 / 4 of a wavelength under the condition of frequent interbedding of sand and mudstone, the thin river channel sand body comprises the river channel sand body which is not corresponding to wave crest or wave trough, and the method has good application effect in petroleum exploration and development.

The invention provides a fingerprint identification apparatus, a display panel and a fingerprint identification method belonging to the technical field of displaying, and can solve the problem that the fingerprint identification apparatuses of the existing organic light emitting diode display products occupy the frame areas and are not conducive to the narrow bezel design. In the fingerprint identification apparatus of the invention, a collimator transmits the collimated light reflected through a fingerprint and blocks the scattered light, which is equivalent to that the light emitted by a light-emitting layer is reflected by a finger and the approximately collimated reflected light can pass through the collimator area, and the tilted light will be blocked by the collimator. A sensor identifies the wave crest and the wave ridge according to the light transmission area of the collimator. The fingerprint identification apparatus is simple in making process, high in practicality, and is suitable for fingerprint acquisition and identification in an organic light-emitting diode display area.

A flexible stent with excellent trackability and expandability comprises a plurality of radially expandable annular members 1 arranged in an axial direction thereof, and connecting elements 2 for connecting adjoining two annular members 1, adjoining annular members 1, 1 being connected by one or more of the connecting elements 2. The annular members 1 are radially expandable and each annular member 1 comprises two waved elements 11, 12 that repeatedly meander in parallel with or substantially parallel with each other and are coupled by coupling elements 13 at intermediate portions between wave crests and wave troughs of the waved elements 11, 12. The stent is excellent in trackability, which in turn makes it possible to pass through three-dimensionally meandering lumens. The stent is excellent in radial strength, substantially free from shortening and easy to provide a lateral hole.

The invention discloses a spiral waveform cutting metal wire as well as a manufacturing method and equipment thereof. The metal wire is a spiral waveform metal wire formed by rotating a periodic waveform metal wire along an axial center line, a wave crest and a wave trough of the metal wire are distributed along the axial center line, and a spiral diameter of the metal wire is equal to a wave height. The spiral waveform cutting metal wire disclosed by the invention can provide better mortar abrasive carrying capability in the process of cutting a rigid material through a stereostructure of the spiral waveform cutting metal wire, and the abrasive is not easily stripped from a cutting wire, therefore, the production speed and efficiency of technical processing of cutting and slicing silicon materials, precious stones and the like are greatly improved, and the surface quality of the sliced materials can be also improved.

The invention discloses a micro-fluidic chip for multi-index detection. The micro-fluidic chip comprises a substrate and a cover plate which is matched with the substrate in a sealed mode, wherein a through hole is formed in the center of the micro-fluidic chip; one or more wave-shaped main channels are formed in the substrate; one end of each main channel is communicated with a sample introduction hole formed in the substrate, and the other end of each main channel is communicated with an air outlet in the substrate; wave troughs of the main channels are arranged away from the direction of the through hole; wave crests of the main channels are arranged close to the direction of the through hole; any one wave trough of the main channel is communicated with a reaction pool through a connecting pipeline; a buffer pool is arranged on the connecting pipeline. The micro-fluidic chip can be detected by instruments through fluorescence, turbidity and development or is directly observed by naked eyes, can be detected in the reaction process in real time and also can be detected after the reaction is ended.

The invention relates to a worm-type plastic corrugated pipe grooving machine. Function of conveying plastic corrugated pipes is completed by a worm curve fixed on a cutter bar of a grooving cutter; the functions of cutting and grooving are realized by one alloy cutter head arranged at the terminal of the worm curve, the worm curve is meshed with wave crests of the plastic corrugated pipes, the plastic corrugated pipes advance for one pitch when being pushed by the worm curve once the cutter bar rotates for a circle, namely the plastic corrugated pipes advance to the next wave crest from the current wave crest, the alloy cutter head arranged at the terminal of the worm curve carries out grooving on the current wave crest for once, the alloy cutter head arranged at the terminal of the worm curve is vertical to axes of the plastic corrugated pipes to ensure that a blade is in a cutting interval while the plastic corrugated pipes do not axially move, the plastic corrugated pipes continuously axially move along with rotation of the cutter bar, and the blade carries out grooving on the wave crest one by one. The grooving machine provided by the invention has simple mechanical structure, no independent pipe conveying device or electronic and electrical inductive control system is required, grooving position is accurate, grooving quality is greatly improved, and rejection rate is greatly reduced while grooving efficiency is greatly improved.

The invention provides a method for detecting an R wave crest of an electrocardiosignal. The method takes point to point difference vector as a base characteristic. The base characteristic has translational and rotational invariance and can overcome influences of baseline drift of the electrocardiosignal. Meanwhile, logarithm polar coordinate conversion is carried out on the difference vector to measure similarity of waveforms. The measurement is sensitive to morphological characteristics of the adjacent waveforms, can capture the whole contour information of the waveforms at the same time, and has robustness on waveform swing. In addition, the method can effectively eliminate influences of interference signals by setting appropriate thresholds. The method for converting the point to point similarity measurement into measurement of waveforms of the points accurately identifies and detects the R wave crest of the electrocardiosignal. The method is applied to related electrocardiogram analytical instruments, can accurately identify the R wave crest in the electrocardiosignal, and is favorable for improving detection and analysis capabilities of electrocardiogram analytical equipment.

The invention belongs to the field of image processing, and discloses a video monitoring method of an electric transmission line. The video monitoring method of the electric transmission line comprises the steps of greasy weather grade recognition, ice covering / snow covering recognition, conductor galloping recognition and periphery alarm. In the step of greasy weather grade recognition, vector included angle characteristics are extracted, and a support vector machine is selected and used for classification. In the step of ice covering / snow covering recognition, the ice covering / snow covering thickness is measured through image processing technologies such as image segmentation, edge detection and improved Hough conversion. In the step of conductor galloping recognition, multiple wave trough points and wave crest points in a conductor are detected, the lowest point and the highest point of conductor galloping are obtained by comparing all the wave trough points and all the wave crest points, and then amplitude and frequency of conductor galloping are computed. In the step of periphery alarm, a method of updating backgrounds automatically is adopted, influence of noise is greatly reduced in the process of judging foreign matter, and whether the foreign matter enters a monitoring area or not is judged in a percentage mode. The video monitoring method achieves video monitoring on the electric transmission line under the atrocious weather environment.

The present invention relates to a wave energy conversion device (1), for use in relatively shallow water, which has a base portion (2) for anchoring to the bed of a body of water (6) and an upstanding flap portion (8) pivotally connected (12) to the base portion. The flap portion is biased to the vertical and oscillates, backwards and forwards about the vertical in response to wave motion acting on its faces. Power extraction means extract energy from the movement of the flap portion. When the base portion (2) is anchored to the bed of a body of water (6) with the flap portion (8) facing the wave motion, the base portion (2) and the flap portion (8) extend vertically through at least the entire depth of the water, to present a substantially continuous surface to the wave motion throughout the full depth of water from the wave crest to the sea bed. A plurality of devices can be interconnected to form one system. The distance between the plurality of flaps is dependent on the wavelength.

A taut mooring system for use on a mobile offshore jack-up platform while it is in an elevated operating condition. The elevated operating condition is with the hull jacked up a safe distance above the highest anticipated wave crests, on vertically movable legs which extend to the ocean floor. The mooring system consists of: radially spaced mooring line attachment means on the structure of the platform; suction piles that are radially spaced around the platform, consistent with the radial spacing of the mooring line attachment means; and taut mooring lines which radially connect the suction piles to the attachment means. The flexibility of the taut mooring system provides the ability to coact with the platform's free standing storm resistance capabilities, yielding enhanced capabilities that will enable the platform to safely resist storm induced forces that the platform would not normally be capable of withstanding, and to enable the platform to be used with longer legs in deeper water.

The invention relates to a detection and control system for a container corrugated plate welding track based on laser ranging, comprising a laser displacement sensor, a welding torch pose adjusting device and a circuit control device. The laser displacement sensor and the welding torch pose adjusting device are connected with the circuit control device through a circuit; one end of a welding torch space position and pose adjusting mechanism is fixed on a stand; and the laser displacement sensor is arranged at the lower end of the welding torch space position and pose adjusting mechanism. Through the diction of the corrugated plate welding line, the control of the welding torch pose and the automatic control of the welding process, the invention achieves the effect that the thickness of welding lines of a downslope welding section from a wave crest to a wave trough, a upslope welding section from a wave trough to a wave crest, a wave crest tangential path and a wave trough are consistent, remarkably improves the uniformity of welding lines of each welding section, greatly reduces the labor intensity of workers, reduces the manual expense of production and is fast and convenient to adjust parameters. The welding speed is more than three times of general manual welding or profile modeling welding, and automatic control is available in the whole process.

The invention discloses a heart rate variability analyzing method based on an amplitude spectrum and instruments. The method comprises the following steps that a human body autonomic nervous function monitor is installed, after amplification, filtering and analog-digital conversion are carried out on electrocardio signals collected by an electrocardio electrode slice, an RR interval time sequence is built, the QRS waveform of the electrocardio signals has the features of large amplitude, short time limit, steep waveform and easy recognition, the key for obtaining HRV signals is that the R wave of an electrocardiogram is accurately calibrated, and according to the morphological characteristic of an R wave picture, the wave crest of the R wave is the maximum positive value in a single signal period; the instruments included in the method comprise a preamplifier module used for amplifying the electrocardio signals, a filter module, an A / D conversion module, an R crest positioning module, a signal pseudo crest pseudo differential eliminating module, an RR sequence forming module, an interpolation module and a display module which are sequentially connected, the preamplifier module is connected with the electrocardio electrode slice through a guide line, and the electrode slice is arranged on the surface of the human body skin and used for collecting the electrocardio signals of the human body.

The invention discloses a monitoring method for time reversal damage to no-datum Lamb wave of an engineering structure. The monitoring method comprises the following steps of: distributing a group of excitation / sensing arrays on a structure to be monitored; building detection channels, and collecting Lamb wave response signals of all excitation / sensing channels; intercepting the response signals, and then conducting time reversal to obtain time reversal structure response signals; loading the time reversal structure response signals onto corresponding excitation, and collecting time reversal focusing structure response signals on the corresponding sensing; and in the time reversal focusing structure response signals of all the detection channels, extracting the occurrence time difference of focusing main wave crest and sidelobe signals, taking the occurrence time difference as a characteristic parameter, calculating to obtain the position and approximate range of the damage by adopting an ellipse positioning method, and analyzing and judging the health condition of the structure to be detected. With the method, the wave packet extension and signal aliasing caused by frequency dispersion can be eliminated, no-datum active positioning and detection to the Lamb wave can be realized, and the healthy monitoring practicalization of the structure can be benefited.

The invention discloses an automatic assembling machine for a door handle. The automatic assembling machine comprises a disc rotation mechanism, wherein the disc rotation mechanism is composed of a turntable and a turntable driving mechanism which is connected with the turntable; a plurality of jigs are uniformly distributed on the periphery outer side of the turntable at equal intervals; a snap spring automatic feeding mechanism, a first gasket feeding mechanism, a second gasket feeding mechanism, a wave crest gasket feeding mechanism, a locking meson feeding mechanism and a torsional spring feeding mechanism are sequentially arranged in the rotation direction of the turntable; a handled square rod feeding mechanism for automatically pressing a handled square rod in the corresponding jig is arranged on one side of the torsional spring feeding mechanism; a belt conveying mechanism is arranged on one side of the square rod feeding mechanism; and a blanking manipulator is arranged between the belt conveying mechanism and the turntable. According to the automatic assembling machine for the door handle, with the adoption of disc rotation, parts of the door handle are sequentially assembled on the corresponding jigs in a disc, so that the working efficiency of door handle assembly and the quality of a product are improved, the automation degree is high with automatic completion of the whole assembling process, and the labor cost is lowered.

The invention discloses a dielectrophoresis demulsification mechanism-based novel crude oil electric dehydration and desalination method and dielectrophoresis demulsification mechanism-based novel crude oil electric dehydration and desalination equipment. The core part of the equipment is an electrode component which may consist of vertically suspended corrugated-plate-shaped electrodes installed with the wave crests and wave troughs of each two adjacent electrodes corresponding one by one respectively, or may consist of corrugated-plate-shaped electrodes and flat-plate-shaped electrodes, which are combined alternately and arranged vertically, wherein the surface of each electrode is coated with a compact insulation layer. When a high-voltage current is applied onto the electrode component, horizontal and non-uniform electric fields are generated between electrode plates to arouse the dielectrophoresis agglomeration of dispersed phase water particles in crude oil emulsion. The method and the equipment disclosed by the invention can meet the dehydration and desalination requirements of crude oil emulsions with different water content, particularly the agglomeration growth and fine dehydration and desalination requirements of dispersed phase small water particles in crude oil emulsion of oil refineries. In addition, the method and the equipment help greatly reduce the use amount of chemical demulsification agent, reduce overall operation cost and improve economic benefit of the oil refineries.

The invention relates to a method for determining the development position of a fractured-vuggy carbonate reservoir, which comprises the following steps: carrying out fine calibration on the fractured-vuggy carbonate reservoir by using the three-dimensional conventional seismic data of great deserts; and carrying out color filling and waveform display on a wave trough and a wave crest by using a seismic-section display method, wherein the color filling is performed according to the vibration amplitudes of the seismic wave trough and the seismic wave crest; and after a wiggle variable area display mode is selected, and determining the transverse development position of the fractured-vuggy carbonate reservoir and the variation situations of the fractured-vuggy carbonate reservoir through observing the waveform changes corresponding to the fractured-vuggy carbonate reservoir calibrated on a seismic profile and the color change relations after the area is changed, wherein same waveform and same filled color after the area is changed instruct a same physical development zone of the reservoir. By using the method of the invention, the development position of the fractured-vuggy carbonate reservoir can effectively be determined, the design on horizontal well paths is guided in actual applications, and all completely-drilled horizontal wells can produce high-capacity oil-gas flows.

The invention relates to a screw fastener comprising a threaded shank having a force application means for torque transmission and a screw fastener point. The threaded shank consists of a shank core and a self-tapping thread, and the thread is designed as a prominence which runs helically over the shank core, is defined by two flanks meeting in an outer thread edge and has a radial height (H). The outer thread edge, at least in a section of the thread, runs in a wavelike manner in the radial direction with an amplitude between wave crests having the height (H) and wave troughs having a height (h) reduced by the amplitude. The thread, at least in the region of one of its flanks, has niches in the region of the wave troughs of the thread edge, which niches interrupt the surface of the flank and their outer boundary is the thread edge, the thread in each case having a certain first apex angle (α), formed between the flanks, in those regions of the wave crests of the thread edge which are not interrupted by niches and a second apex angle (α′) in the deepest regions of the wave troughs of the thread edge. The first apex angle (α) between the flanks is approximately within the range of 30° to 35°, the second apex angle (α′) being 30° up to at most 58°.

The invention discloses a full-waveform laser radar echo data gaussian decomposition method based on a genetic algorithm. The method is mainly formed by five steps including echo denoising, initial wave crest extracting, initial parameter estimating, waveform fitting and precision judging; when the precision of initial fitting meets the requirements, second fitting is not carried out, when the precision of the initial fitting does not meet the requirements, iteration fitting is carried out, and in each iteration, the fitting precision is improved by a method of increasing a gaussian component until a stopping condition is met; a gaussian function is used for fitting echo data of a full-waveform laser radar; and a gaussian filter method is adopted to filter noise of the echo data of the full-wave form laser radar, the number of initial gaussian components is confirmed by extracting a peak value point, an initial parameter range is estimated, fitting and precision adjusting are carried out on the echo data of the full-waveform laser through the genetic algorithm, an echo gaussian decomposition software system based on the genetic algorithm is manufactured, and echo decomposition operation is simplified.

The invention provides a display device which can reduce blue light output. The technical proposal is as follows: the display interface of the display device is coated by a photo-absorption material layer which has low transmissivity to the blue light within a specific wavelength section; as for the luminescent display device with a backlight lamp, the blue light output intensity of the backlight lamp on the specific wavelength section is reduced; as for the display device which illuminates by fluorescent powder, the content or composition of the fluorescent powder which generates the blue light is reduced or adjusted, thus realizing reducing the blue light intensity or adjusting the spectral curve and leading the wave crest of the blue light to deviate by a range of 420-455nm. Compared with the prior art, by reducing the blue light output of the display device or changing the spectral curve of the blue light in the display device, the wave crest of the blue light is deviated by the range of 420-455nm where the damage factor to human eyes is largest, thus reducing the damage of the blue light to the human eyes and achieving the purpose of protecting the eyesight.

The invention discloses a detection circuit and method for a zero crossing point of an alternating current power supply. A half-wave shaping circuit is formed by a current limiting resistor and a light-emitting diode, a cathode of a protective diode is connected with the current limiting resistor, and the other end of the current limiting resistor is connected with an input end of the alternating current power supply; and a photistor collector is connected with a singlechip and a direct current power supply through another light-emitting diode. The singlechip firstly detects twice level trip interruption time t1 and t3 of a previous alternating current power supply positive half-wave, calculates a previous wave crest moment t2, then detects the twice level trip interruption time t4 and t6 of a next alternating current power supply positive half-wave and a wave crest time t5 at the time to obtain an alternating current power supply period, and outputs a control signal to control a thyristor to be accurately triggered with a next zero crossing point moment as a benchmark. The detection circuit and method for the zero crossing point of the alternating current power supply enhance the driving capacity of a voltage without other gate circuits, has no requirements on amplitude and frequency of the alternating current power supply and no limits on a working voltage of the light-emitting diode and can allow a voltage value of the alternating current power supply to fluctuate in a large range.

The invention relates to the technical field of computer application, specifically, relates to a heart sign obtaining method and a heart sign obtaining device. The heart sign obtaining method comprises the steps of: obtaining photoplethysmography (PPG) data; performing low-pass filtering processing with cut-off frequency less than or equal to 4 HZ on the PPG value and removing high-frequency noise; performing discrete wavelet filtering processing on the PPG value subjected to high-frequency noise removal and correcting baseline drift; obtaining the wave crest and wave trough positions of PPG waveform according to the PPG data subjected to baseline drift correction, and obtaining the time interval value between the wave crests according to the wave crest and wave trough positions and the sampling rate of the PPG data; obtaining RR interval data according to the time interval value between the wave crests, and calculating the heart sign according to the RR interval data. By adoption of the method and the device, a user can comprehensively obtain the heart sign value.

The invention provides a signal DOA estimation method. The method supposes that an unknown noise covariance matrix has a symmetrical Toeplitz matrix character; according to the difference conception of the traditional covariance matrix, an imaginary number j is introduced so that the newly constructed covariance matrix changes into a central Hermitian matrix, thereby, the character decomposition can obtain the same DOA as the incident signal numbers. The method greatly reduces the number of the antenna array element required by estimating the signal wave arrival direction, and a wave crest is only formed in the wave arrival direction of the real signal. The method can reduce cost greatly in the practical application.

The invention provides a measuring method for physiological parameters, and belongs to the technical field of physiological signals, and especially relates to a measuring method for physiological parameters. The invention provides a measuring method for physiological parameters, and the method is low in use cost and good in measuring effect. The method comprises the following steps: 1) a user finger covering a mobile phone camera, turning on a mobile phone flash lamp, and taking pictures by an image sensor in the mobile phone camera; 2) a mobile phone performing quantization determining on green ray value of RGB of all pixels in each frame of images, and calculating average gray value, to draw a green ray curve, calculating color variation of each frame, to form a pulse wave curve; performing median filtering on the pulse wave, and removing baseline drift; 3) inputting user body parameters; and finding a main wave crest, a dicrotic crest, the height of the main wave crest, the height of the dicrotic crest in the pulse wave which is processed by filtering, and calculating physiological parameters of a human body through the parameters.

The invention provides atrial fibrillation identification method, device and equipment and a computer-readable storage medium. The method includes the steps: the R wave crest position in an electrocardiogram signal to be identified is obtained, and then heart rate variability characteristics and heart rate segments are determined according to the R wave crest position; the cardiac characteristicsof each cardiac segment are acquired to form a cardiac characteristic group; and finally, the heart rate variability and heart rate characteristics are input into the model of atrial fibrillation recognition, and the results of atrial fibrillation recognition are obtained. The invention can effectively identify atrial fibrillation by inputting heart rate variability characteristics and heart ratecharacteristics of an electrocardiogram signal into a pre-trained atrial fibrillation identification model, thereby realizing the improvement of reliability and accuracy of atrial fibrillation identification.

A corrugate fin of an evaporator includes wave crest portions, wave trough portions, and flat connection portions connecting together the wave crest portions and the wave trough portions. Opposite end portions of a cutout extend to corresponding connection portions located at opposite ends of the wave crest portion and the wave trough portion. A projection projecting inward is formed integrally with end portions of the connection portions, the end portions of the connection portions corresponding to opposite ends of the cutout. The projection extends between the end portions of the connection portions located at the opposite ends of the wave crest portion and the wave trough portion. The projection projects inward in a shape resembling a lying letter V. The evaporator exhibits excellent drainage of condensed water and enables high work efficiency in manufacture thereof.

The invention provides a low-Ag hypo eutectic Sn-Cu-Ag lead-free solder the components of which are 0.5 to 0.65wt percent of Cu, 0.1 to 0.45wt percent of Ag, 0.001 to 0.1wt percent of Ni, 0.001 to 0.3wt percent of Sb, 0.001 to 0.2wt percent of Bi and / or In, 0 to 0.01wt percent of P, 0 to 0.03wt percent of Ge and the rest is Sn. The solder is further characterized in that (1) the content of Ag in the solder of Cu plus Ag is less than 1wt percent is not more than 0.45wt percent; (2) the gross of the microelements like Ni, Sb, Bi, In, P, and Ge, etc., that are added is not more than 0.5wt percent. The solder has the advantages of low cost and excellent oxidation, wettability and overflow resistances, can remarkably reduce the waste of the solder, improve the forming of the welding point, remarkably reduce the connecting defects of braze welding. The solder can replace a Sn-Cu-Ag hypo eutectic material and is suitable for the wave crest welding, dip soldering as well as manual welding and reflow soldering for electric products.

The invention relates to a reluctance brushless multipolar rotational transformer. And the external circular surface of a rotor is uniformly provided with P wave crests and P wave throughs, where these wave crests and wave throughs are smoothly interlinked to compose the wavy external circular surface of the rotor, and excitation, sine and cosine windings are positive phase-to-negative phase connected in series. As a constant voltage alternating current passes through the excitation winding, the sine and cosine windings output voltages whose electromotive force amplitudes make p sine and cosine variations with the rotation angle of the rotor. And the invention has characters of simple structure, convenient to make, and especially applied to the rotor position sensor of a brushless DC motor.

A heat exchanger assembled from multiple heat exchanging tubes. Each of the multiple heat exchanging tubes is formed as a flattened tube of 0.5 mm in thickness by press work or bending work of a stainless steel plate member having a thickness of 0.1 mm. Each of the multiple heat exchanging tubes is structured to have multiple lines of sequential wave crests and multiple lines of sequential wave troughs formed on each of flattened faces of the heat exchanging tube. The multiple lines of the sequential wave crests and the multiple lines of the sequential wave troughs are arranged to have a preset angle γ relative to a main stream of an air flow. The lines of the sequential wave crests and the lines of the sequential wave troughs are symmetrically folded back about folding lines arranged at a preset interval W along the main stream of the air flow.