Micro-Sized Pinhole Inspection with Segmented Time Reversal and High-Order Modes Cluster Lamb Waves Based on EMATs

Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.

Novel mechanism for boring non-cylinder piston pinhole based on giant magnetostrictive materials

To bear more loads for heavy truck pistons, the shape of heavy truck piston pinhole is often designed as noncylinder form. Current methods cannot meet the needs for precision machining on non-cylinder piston pinhole （NCPPH）. A novel mechanism based on giant magnetostrictive materials （GMM） is presented. New models are established for the servo mechanism, GMM, and magnetizing force of the control solenoid to characterize the relationship between the control current of the solenoid and the displacement of the giant magnetostrictive actuator （GMA）. Experiments show that the novel mechanism can meet the needs to perform fine machining on NCPPH effectively.

Detailed characterization of polycapillary focusing x-ray lenses by a charge-coupled device detector and a pinhole

A method to measure the detailed performance of polycapillary x-ray optics by a pinhole and charge coupled device(CCD)detector was proposed in this study.The pinhole was located between the x-ray source and the polycapillary x-ray optics to determine the illuminating region of the incident x-ray beam on the input side of the optics.The CCD detector placed downstream of the polycapillary x-ray optics ensured that the incident x-ray beam controlled by the pinhole irradiated a specific region of the input surface of the optics.The intensity of the output beam of the polycapillary x-ray optics was obtained from the far-field image of the output beam of the optics captured by CCD detector.As an application example,the focal spot size,gain in power density,transmission efficiency,and beam divergence of different parts of a polycapillary focusing x-ray lenses(PFXRL)were measured by a pinhole and CCD detector.Three pinholes with diameters of 500,1000,and 2000μm were used to adjust the diameter of the incident x-ray beam illuminating the PFXRL from 500μm to the entire surface of the input side of the PFXRL.The focal spot size of the PFXRL,gain in power density,transmission efficiency,and beam divergence ranged from 27.1μm to 34.6μm,400 to 3460,26.70%to 5.38%,and 16.8 mrad to 84.86 mrad,respectively.

Spatial resolution and image processing for pinhole camera-based X-ray fluorescence imaging: a simulation study

Spatial resolution and image-processing methods for full-field X-ray fluorescence(FF-XRF)imaging using X-ray pinhole cameras were studied using Geant4simulations with different geometries and algorithms for image reconstruction.The main objectives were:(1)calculating the quantum efficiency curves of specific cameras,(2)studying the relationships between the spatial resolution and the pinhole diameter,magnification,and camera binning value,and(3)comparing image-processing methods for pinhole camera systems.Several results were obtained using a point and plane source as the X-ray fluorescence emitter and an array of 100×100 silicon pixel detectors as the X-ray camera.The quantum efficiency of a back-illuminated deep depletion(BI-DD)structure was above 30%for the XRF energies in the 0.8–9 keV range,with the maximum of 93.7%at 4 keV.The best spatial resolution of the pinhole camera was 24.7μm and 31.3 lp/mm when measured using the profile function of the point source,with the diameter of 20μm,magnification of 3.16,and camera bin of 1.A blind deconvolution algorithm with Gaussian filtering performed better than the Wiener filter and Richardson iterative methods on FF-XRF images,with the signal-to-noise ratio of 7.81 dB and improved signalto-noise ratio of 7.24 dB at the diameter of 120μm,magnification of 1.0,and camera bin of 1.

Development and application of an online pinhole detector for cold-rolled strips

An online pinhole detector based on the photoelectric inspection of cold-rolled steel strips was introduced. Pinhole detection is important to guarantee the quality of cold-rolled steel strips. The detector here was developed independently by Baosteel,and is designed based on the principle of photoelectric transfer. Typically, an inspection light source is installed above the steel strip to be inspected, and a photoelectric receiver is installed beneath the steel strip. The pinhole detector consists of a super-bright LED light source and a photoelectric receiver, which is composed primarily of photomultipliers. The super-bright LED light source illuminates the strip surface, and the light that permeates from pinholes is detected and amplified by a photoelectric receiver. The photomultiplier transforms the detected light into an electrical signal ,which is later recognized and classified by a signal-processing circuit and collected by a data-acquisition card. The detector can accurately track the strip edge and shield the strip edge from outside light. As a result,this system can detect a pinhole in the strip edge with a small blind zone on the edge. Most importantly, the detector exhibits good inspection accuracy and can accurately detect a pinhole with a diameter of 15 μm.

Microperforate (Pinhole) hymen and infertility;a rare case report

Inroduction Female genital tract anomalies may have a devastating impact on the potential for sexual activity and fertility. Microperforate (pinhole) hymen is one of them. Microperforate hymen can lead to infertility, primary amenorrhea, acute or chronic pelvic pain, abnormal vaginal bleeding, dysuria, pollakiuria or a foul-smelling vaginal discharge. Aim We aim to report a patient who had intercourse problems and infertility complaints later found to have a microper-forate hymen. Discussion Pinhole opening of hymen may permit passage of fluids. Consequently spontaneous pregnancy can occur rarely. A few reports showed pregnancies with intact hymen without penetration of penis. But in general patients have fertility problems. Conclusion The results of the surgery are similar in all techniques and the particular surgical centre will have its own preference of which technique it prefers since after diagnosis definitive treatment is surgical and effective. Failure to manage these patients correctly may have long-term sequelae for their psychological, sexual and reproductive health.

Study of Supper Resolution Processing Methods for Thick Pinhole Image

An image super resolution reconstruction method was used to improve the spatial resolution of the thick pinhole imaging system and to mitigate the limitations of the image spatial resolution of the hardware of the image diagnostic system. The thick pinhole is usually applied into the diagnostics of the high energy neutron radiation image. Due to the impacts among its energy flux, spatial resolution and effective field of view, in dealing with the large area radiation source, the spatial resolution of the thick pinhole neutron image cannot meet the requirements for high precision modeling of the radiation source image. In this paper, the Lucy-Richardson image super resolution reconstruction method was used to simulate the thick pinhole imaging and super resolution image reconstruction. And the spatial resolution of the image could be increased by over three times after the image super resolution reconstruction. Besides, in dealing with the pseudo-noise, plum blossom shape appeared in the image super resolution reconstruction. The analysis of the source of the pseudo-noise was made based on the simulation of the image reconstruction under various conditions according to the characteristics of the thick pinhole image configuration.

Performance Evaluation of the Thick Pinhole Gamma Rays Diagnostic System

The diagnostic methods for the profile of the radiation source were estab-lished at first based on the pinhole imaging principle. In this paper, the relationships among various parameters of the gamma-rays crammer such as the modulation transfer function (MTF), the noise power spectrum (NPS), the signal-noise ratio (SNR) and the detective quantum efficiency (DQE) are developed and studied experimentally on the cobalt radiation source. The image diagnostic system is consisting with rays-fluorescence convertor (YAG crystal), optical imaging system, MCP image intensifier, CCD camera and other devices. The spatial resolution of the modulation transfer function (MTF) at 10% intensity was measured as 1 lp/mm by knife-edge method. The quantum of the measurement system is about 150 under weak radiation condition due to the single particle detection efficiency of the system. The dynamic range was inferred preliminarily as about 437. The required radiation intensity was calculated using the experiment result for the (SNR) = 1, 5, 10, respectively. The theoretical investigation results show that the radiation image with (SNR) = 1 can be only obtained when the pinhole diameter is 0.7 mm, object distance and image distance are both 200 cm, and the radiation intensity is about 1.0 × 1012 Sr-1·cm-2.

THEORETICAL TOOTH PROFILE AND ITS SUBSTITUTE CURVE OF THE PINION CUTTER FOR PINHOLES

The formula for the engaging curve of the pinion cutter with pitholes and the formula forthe theoretical tooth profile of the tinion cutter for the generating gearing of pinhoes are developedbased on the engaging theory. The substitute curve of the theoretical tooth profile of the pinion cut-ter is determined by the least square method.

High-resolution portable lens-free on-chip microscopy with RGB LED via pinhole array

Lens-free on-chip microscopy with RGB LEDs(LFOCM-RGB)provides a portable,cost-effective,and high-throughput imaging tool for resource-limited environments.However,the weak coherence of LEDs limits the high-resolution imaging,and the luminous surfaces of the LED chips on the RGB LED do not overlap,making the coherence-enhanced executions tend to undermine the portable and cost-effective implementation.Here,we propose a specially designed pinhole array to enhance coherence in a portable and cost-effective implementation.It modulates the three-color beams from the RGB LED separately so that the three-color beams effectively overlap on the sample plane while reducing the effective light-emitting area for better spatial coherence.The separate modulation of the spatial coherence allows the temporal coherence to be modulated separately by single spectral filters rather than by expensive triple spectral filters.Based on the pinhole array,the LFOCM-RGB simply and effectively realizes the high-resolution imaging in a portable and cost-effective implementation,offering much flexibility for various applications in resource-limited environments.

Drainage design combining drain holes and pinholes for tunnel boring machine segments subject to high water pressure

Balance of the groundwater and ecology is crucial for controlled discharge.However,regarding the segments of tunnel boring machines(TBMs)under high water pressure,the stability of the lining structure is often reduced by excessive drain holes required to achieve this balance.The large discharge of pinholes can easily have severe consequences,such as the lowering of the groundwater table,drying of springs,and vegetation wilting.Thus,in this study,according to the fluid-structure coupling theory,a new drainage design for TBM segments was developed by considering a mountain tunnel subject to a high water pressure as a case study.The evolution characteristics,including the external water pressure of the lining,discharge volume of the segment,and groundwater-table drawdown,were investigated via numerical modeling with drain holes and pinholes.The results indicated that the optimal design parameters of drainage segments for the project case were as follows:a circumferential spacing angle and longitudinal number on one side of a single ring of 51°and 2,respectively,for the drain holes and an inclination angle and length of 46.41°and 0.25 times the grouting thickness,respectively,for the pin holes.

Cross-talk-free integral imaging three-dimensional display based on a pyramid pinhole array

We propose a cross-talk-free integral imaging 3D display based on a pyramid pinhole array. The pyramid pinhole array is used to provide a point light source array. Since the generated point light source array is behind a transmission-type display panel that displays an elemental image array, the pseudoscopic problem can be resolved. By setting the appropriate parameters for the pyramid pinhole array, the cross talk can be eliminated.We experimentally verify the reconstruction of the orthoscopic and cross-talk-free 3D images using the proposed 3D display.

Noniterative spatially partially coherent diffractive imaging using pinhole array mask

We propose and experimentally demonstrate a noniterative diffractive imaging method for reconstructing the complex-valued transmission function of an object illuminated by spatially partially coherent light from the far-field diffraction pattern.Our method is based on a pinhole array mask,which is specially designed such that the correlation function in the mask plane can be obtained directly by inverse Fourier transforming the diffraction pattern.Compared to the traditional iterative diffractive imaging methods using spatially partially coherent illumination,our method is noniterative and robust to the degradation of the spatial coherence of the illumination.In addition to diffractive imaging,the proposed method can also be applied to spatial coherence property characterization,e.g.,free-space optical communication and optical coherence singularity measurement.

Spot size measurement of a flash-radiography source using the pinhole imaging method

The spot size of the X-ray source is a key parameter of a flash-radiography facility, and is usually quoted as an evaluation of the resolving power. The pinhole imaging technique is applied to measure the spot size of the Dragon-I linear induction accelerator, by which a two-dimensional spatial distribution of the source spot is obtained. Experimental measurements are performed to measure the spot image when the transportation and focusing of the electron beam are tuned by adjusting the currents of solenoids in the downstream section. The spot size of full-width at half maximum and that defined from the spatial frequency at half peak value of the modulation transfer function are calculated and discussed.

The beam-based calibration of an X-ray pinhole camera at SSRF

A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility （SSRF） storage ring.The electron beam size is derived by unfolding the radiation image and the point spread function （PSF） with deconvolution techniques.The performance of the pinhole is determined by the accuracy of the PSF measurement.This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes.Applying this method at SSRF,the PSF value of the pinhole is revised from 37 to 44μm.The deviation in beam size between the theoretical value and the measured value isminimized to 4% after calibration.This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5μm.

Modeling and simulation of pinhole channels

This article presents a general pinhole channel reference model based on the cause of pinhole effect. On the base of this reference model, a deterministic simulation model is developed by keeping the difference of correlation properties between reference and simulation model as smaller as possible. The correlation properties include temporal autocorrelation fimction （ACF）, two-dimensional （2-D） space cross-correlation function （CCF） and frequency correlation function （FCF）. The results show that although pinhole channel has good correlation properties, the channel capacity is very low because of the low rank of channel transform matrix.

Corrosion Behavior of Epoxy-Coated Rebar with Pinhole Defect in Seawater Concrete

Experiments were carried out to investigate the corrosion behavior of epoxy-coated rebar （ECR） with pinhole defect（diameter in hundreds of microns） immersed in the uncarbonated/carbonated simulated pore solution （SPS） of seawaterconcrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphologyof corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electronmicroscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectronspectroscopy and Mott-Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defectexhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect waspassivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitiveadsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted （thethickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between highhydroxide and chloride activity, while in the carbonated SPS, crevice corrosion happened under the coating around pinhole,because of the different oxygen concentrations cell at the coating/steel interface. In the third stage, localized corrosionoccurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at thenano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCIa.4HaO andFe2（OH）3Cl to Fe2O3.H2O, and the corrosion area was expanded outward in the carbonated SPS.

Ultrafast two-dimensional x-ray imager with temporal fiducial pulses for laser-produced plasmas

It is challenging to make an ultrafast diagnosis of the temporal evolution of small and short-lived plasma in two dimensions. To overcome this difficulty, we have developed a well-timed diagnostic utilizing an x-ray streak camera equipped with a row of multi-pinhole arrays. By processing multiple sets of one-dimensional streaked image data acquired from various pinholes, we are capable of reconstructing high-resolution two-dimensional images with a temporal resolution of 38 ps and a spatial resolution of 18 μm. The temporal fiducial pulses accessed from external sources can advance the precise timing and accurately determine the arrival time of the laser. Moreover, it can correct the nonlinear sweeping speed of the streak camera. The effectiveness of this diagnostic has been successfully verified at the Shenguang-II laser facility,providing an indispensable tool for observing complex physical phenomena, such as the implosion process of laser-fusion experiments.

Dispersion characteristics of clayey soils containing waste rubber particles

The rubber-containing waste materials have been widely used to improve the engineering properties of soils in recent years.Among others,granular rubbers are utilized in various ways to increase the bearing capacity and shear strength and to reduce the settlement and liquefaction potential of soils.The granular rubbers have many advantages such as temperature resistance,flexibility,tear-resistance,non-slip,and thermal and electrical insulation.This study presents the distribution characteristics of five different types of clayey soils with different engineering properties containing waste rubber particles(WRPs).On the other hand,determining and controlling the dispersion characteristics of clayey soils is two significant engineering problems.The study aims to solve these two remarkable and problematic issues in an eco-friendly and safe way.The role of WRP treatment in the investigation of soil dispersion behavior,which can cause dangerous problems such as piping,erosion,and dispersion,reflects the original and different perspectives of this study.Within this scope,geotechnical parameters of the clayey soils were determined.Subsequently,pinhole test,crumb test,double hydrometer test,and scanning electron microscopy(SEM)analysis were performed on the Na-activated bentonite,refined ball clay,Ukrainian kaolin,Avanos kaolin,and Afyon clay samples with different percentages of WRPs(0%,5%,10%,and 15%).Consequently,Avanos and Ukrainian kaolin clays gave the most limited response to the dispersion behavior with the addition of WRP.Also,WRP treatment on the ball clay and bentonite samples showed limited efficiency.Afyon clay,which was defined as dispersive by the three tests that determined its dispersion potential,showed 3 level changes in the pinhole tests and 2 level changes in the crumb tests,and gave the most effective results in terms of WRP efficiency.