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356 results about "Refraction angle" patented technology

The angle of incidence in the water is approximately 39°. At this angle, the light refracts out of the water into the surrounding air bending away from the normal. The angle of refraction in the air is approximately 57°. These values for the angle of incidence and refraction are consistent with Snell's Law.

System and method for phase-contrast imaging by use of X-ray gratings

ActiveCN101532969AReduce production difficulty requirementsLower application thresholdComputerised tomographsTomographyGratingRefractive index
The application relates to a system and a method for the phase-contrast imaging by use of X-ray gratings. The system comprises an X-ray device, a first absorption grating, a second absorption grating, a detection unit, a data processing unit and an imaging unit, wherein the X-ray device transmits an X-ray bundle to a detected object; the first and second absorption gratings are positioned in the direction of the X-ray bundle; the X-ray refracted by the detected object forms an X-ray signal with variable intensity through the first absorption grating and/or the second absorption grating; the detection unit receives and converts the X-ray with variable intensity into an electrical signal; the data processing unit processes and extracts refraction-angle information in the electrical signal, and utilizes the refraction-angle information to figure out pixel information; and the imaging unit constructs images of the object. In addition, the system and the method can also realize CT imaging by using a rotating structure to rotate the object so as to obtain refraction angles in a plurality of projection directions and the corresponding images, and use CT reconstruction algorithm to figureout refraction-index fault images of the detected object. According to the invention, the phase-contrast imaging of approximate decimeter-magnitude viewing fields under incoherent conditions can be realized by use of common X-ray machines or multi-seam collimator such as source gratings, as well as two absorption gratings.
Owner:NUCTECH CO LTD +1

Ultrasonic wave nondestructive apparatus and method for measuring residual stress of welded structure

The invention relates to a welding structure residual stress ultrasonic lossless measurement device and a method, in particular to a device and a method using ultrasonic for measuring the residual stress of a welding structure, belonging to the residual stress measurement field. The method aims at overcoming the problems of a traditional stress measurement method that work pieces are destroyed, time is consumed and the residual stress measurement can not be satisfied under the service condition of the welding structure. The two ends of a probe group of the invention are respectively connected with an impulse signal source and a signal receiving processing device which is connected with a display. And a microcontroller is embedded in the signal receiving processing device. In said method, the coordinate of a measured point is determined; the probe group emits impulse signals sent out from the impulse signal source into a work piece through a first critical refraction angle to generate critically refracted longitudinal waves, wherein, enveloping data are read by the signal receiving processing device and are discretized into digital signals and FIR filtering waves; total enveloping weight eigenvalue Mn is worked out; abnormal data are removed according to Brubbs criterion after one measured point is measured for a plurality of times, measuring position is changed for measuring again, and Mn and Mn+1 are worked out according to two measuring points to calculate the residual stress Delta of the work piece.
Owner:HARBIN INST OF TECH

X ray phase contrast tomography

ActiveCN101726503AAddressing organizational cascadingFix low contrastMaterial analysis by transmitting radiationPhase contrast tomographySoft x ray
The invention relates to an X ray phase contrast imaging system and an X ray phase contrast imaging method. The system comprises an X ray device, a grating system, a detection unit, a data processing unit and a relative shifting device, wherein the X ray device emits X ray bundles to a detected object; the grating system comprises a first absorption grating and a second absorption grating and is positioned on a direction of an X ray, and the X ray refracted by the detected object forms a variable-intensity X ray signal through the first absorption grating and the second absorption grating; the detection unit receives the variable-intensity X ray signal and converts the variable-intensity X ray signal into an electrical signal; the data processing unit processes and extracts the refraction angle information in the electrical signal and computes pixel information by utilizing the refraction angle information; and the relative shifting device is used for enabling the detected object to relatively shift relative to the imaging system. The imaging system carries out phase contrast imaging for the detected object within a certain relative shifting range of the imaging system and the detected object at a plurality of positions so as to obtain a plurality of images of the detected object. The images are converted into the images on the same reconstruction plane so as to carry out three-dimensional image reconstruction.
Owner:TSINGHUA UNIV +1

Star light refraction satellite autonomous navigation method based on single star sensor

The invention discloses a star light refraction satellite autonomous navigation method based on a single star sensor. The star light refraction satellite autonomous navigation method comprises the following steps: 1, installing the star sensor on a satellite according to an optimal installation angle; 2, after the star sensor shoots a star map, identifying normal stars in the star map by using a triangle algorithm; 3, calculating an optical axis direction and a satellite gesture of the star sensor by using the identified star sensors; 4, selecting a star from the star map according to the optical axis direction of the star sensor to generate a stimulation refraction star map; 5, identifying a refraction star by using the stimulation refraction star map, and calculating a star light refraction angle according to an identification result; and 6, substituting the star light refraction angle into a system model, and obtaining navigation information of the satellite by using an optimum estimation method by a spaceborne computer. According to the star light refraction satellite autonomous navigation method, the precision of autonomous navigation of a star light refraction satellite is improved, and the design cost is lowered.
Owner:HARBIN ENG UNIV

Satellite starlight refraction navigation error determination and compensation method

The invention relates to a satellite starlight refraction navigation error determination and compensation method. The method comprises the following steps: firstly, generating data of a satellite orbit by virtue of STK software; establishing a satellite attitude planning model; determining an actual observation visual field, and simulating an observation star map comprising refraction stars and non-refraction stars; calculating to obtain the tangential height h of the refraction stars; calculating to obtain the tangential height h'' of the refraction stars with errors of refraction angles and errors of an atmospheric model, wherein tangential height errors are mainly caused by the measurement precision errors of the refraction angles and the errors of the atmospheric model; calculating to obtain the position of a satellite under a geocentric inertial coordinate system; and performing filtration by an extended Kalman filtration method, and outputting a starlight refraction navigation estimated position and position errors. The method provided by the invention can realize accurate prediction of navigation precision of a satellite starlight refraction navigation system, and is comprehensive in error analysis and accurate and reliable in results.
Owner:CHINA ACADEMY OF SPACE TECHNOLOGY

Ultrasonic time-of-flight diffraction (TOFD) detection method for weld seam

The invention relates to an ultrasonic time-of-flight diffraction (TOFD) detection method for a weld seam. The ultrasonic TOFD detection method comprises the following steps of: respectively taking two probes with different refraction angles as a transmitting probe and a receiving probe; arranging the transmitting probe and the receiving probe at the same side of the weld seam; connecting the transmitting probe and the receiving probe with a TOFD instrument; scanning the weld seam; carrying out interpretation on scanned images; finishing the scanning if no defected signal images are discovered; if defected signal images are discovered, changing probe clearance space (PCS), keeping the other settings and parameters unchanged, and carrying out scanning once again; calculating according to two-time scanned results; and achieving the positioned and quantitative detection of the defects of the weld seam. According to the ultrasonic TOFD detection method, a single-face one-sided scanning manner is adopted, the original advantages of TOFD detection are kept, meanwhile, the TOFD detection for the butt-jointed weld seams between a tube body of a pressure vessel and an end enclosure as well as between a pressure conduit and irregular members, such as an elbow, a pipe reducer or a tee joint and the like, is achieved, and thus, the ultrasonic TOFD detection method is wide in scope of application.
Owner:STATE GRID HEBEI ENERGY TECH SERVICE CO LTD +1

System and method for X-ray optical grating contrast imaging

The invention relates to a system and a method for X-ray grating contrast imaging. The system comprises an X-ray launching device, a first absorption grating, a second absorption, a detecting unit, a data processing unit and an imaging unit, wherein the X-ray launching device is used for launching X-ray beams to a detected article; the first absorption grating and the second absorption grating are positioned in the launching direction of the X-ray beams, and the X-ray refracted by the detected article forms X-ray signals with different intensity by the first absorption grating and the second absorption grating; the detecting unit is used for receiving the X-ray signals with changeable intensity and converting the X-ray signals into electric signals; and the data processing unit is used for processing and extracting the refraction angle information in the electric signals and calculating the pixel information through the refraction angle information; the imaging unit is used for constructing the image of the article. In addition, a rotating structure can also be utilized to rotate the article to realize a CT imaging mode so as to obtain refraction angles in a plurality of projection directions and the corresponding images and calculate the refraction index tomography image of the detected article by CT reconstruction algorithm. The system and the method adopt the common X-ray machine and the grating above a period of ten micron magnitude to realize the contrast imaging of a decimeter magnitude like viewing field.
Owner:NUCTECH CO LTD +1

Sea surface error correction method for measuring submarine topography on basis of airborne laser radar

The invention discloses a sea surface error correction method for measuring the submarine topography on the basis of airborne laser radar. The method comprises the steps that three-dimensional sea surface data is generated according to sea return pulses, a space rectangular coordinate system taking a laser radar launching point M as an original point is established, and coordinates of a sea surface incidence point in the space rectangular coordinate system are calculated; a three-dimensional sea surface coordinate system taking the sea surface incidence point as a coordinate original point, an incidence angle alpha obtained when a laser is incident on sea water and a refraction angle beta are calculated, then the submarine depth h can be calculated according to the incidence angle alpha, the refraction angle beta and the incidence distance L' of refracted rays, the submarine depth h is corrected according to the sea surface height delta h to obtain a submarine depth correction value h1, and then submarine topography data can be formed. According to the sea surface error correction method, errors caused by sea heaving can be effectively corrected, the problem that the precision is poor when the submarine topography is measured by traditional airborne laser radar is solved, and precise measuring of the submarine topography is achieved.
Owner:OCEANOGRAPHIC INSTR RES INST SHANDONG ACAD OF SCI

Ultrasonic inspection method, ultrasonic inspection device and integrated longitudinal wave, transverse wave and creeping wave ultrasonic angle beam probe

ActiveCN103954687ARealize all-round scanningSolve the problems of flaw detectionAnalysing solids using sonic/ultrasonic/infrasonic wavesCreeping waveUltrasonic beam
The invention discloses an ultrasonic inspection method, an ultrasonic inspection device and an integrated longitudinal wave, transverse wave and creeping wave ultrasonic angle beam probe. The ultrasonic inspection method comprises the following steps: preparing an ultrasonic angle beam probe with an incident angle of alpha, a longitudinal wave refraction angle of betaL and a transverse wave refraction angle of betaT; adjusting the ultrasonic angle beam probe; arranging the ultrasonic angle beam probe on the outer surface of a workpiece to be detected; inspecting the workpiece to be detected by ultrasonic beams emitted from the ultrasonic angle beam probe; and judging whether the workpiece to be detected has defects and corresponding defect positions according to reflection echo received by the ultrasonic angle beam probe. Omni-directional scanning of a steel weld to be detected is realized, a detection leakage rate is reduced, the inspection efficiency is improved, the inspection cost is lowered, the probe traveling distance is reduced by 40 percent compared with that of a transverse wave angle beam probe, and the inspection accuracy can be improved to be over 90 percent.
Owner:TEWARE
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