Reasonable Exposure Time Research Articles

A high-accuracy single-frame 3D reconstruction method with color speckle projection for pantograph sliders

The carbon slider of the pantograph is a crucial component in the high-speed rail power system, and regular maintenance is of great significance. 2D-based approach is susceptible to inaccuracies caused by defects, rainwater, stains, and other factors. Due to the weak texture and uneven reflectance of the slider, it is difficult to obtain accurate 3D information through a single-frame approach. To address this issue, this paper proposes a high-accuracy 3D imaging method for sliders, successfully resolving the long-standing problem of low reconstruction accuracy and limited generalization in pantograph reconstruction. Firstly, high-precision disparity maps of industrial component are generated using the binocular Gray Code phase-shifting method as the Ground Truth, and the color speckle pattern is subsequently utilized as the input for the model. Secondly, we propose a split-cost volume approach that achieves cost aggregation using only 2D decoding-encoding operations. Furthermore, disparity regression is utilized to provide the initial disparity for the GRU(Gated Recurrent Unit), thereby accelerating the convergence speed of the model. Quantitative experiments of optical standard sphere validated that the proposed method could achieve 3D reconstruction with a radius error of no more than 0.07 mm. The pantograph reconstruction results showed that the average absolute error of the carbon slider did not exceed 0.21 mm under reasonable exposure time and the working distance at which focus has been achieved, which meets the requirements of industrial inspection.

Research on piston error sensing for segmented mirrors under atmospheric turbulence.

Large aperture ground-based segmented telescopes typically use electrical edge sensors to detect co-phase errors. However, complex observing environments can lead to zero-point drift of the edge sensors, making it challenging to maintain the long-term co-phase of the segmented primary mirror using only edge sensors. Therefore, employing optical piston error detection methods for short-term calibration of edge sensors can address the issue of zero-point drift in the sensors. However, atmospheric turbulence can affect calibration accuracy based on the observational target. To achieve high-precision calibration of electrical edge sensors, this study investigates the impact of atmospheric turbulence on optical piston error detection. Based on simulated results, it is found that the actual measured piston error in the presence of atmospheric turbulence is the difference between the average phases of the two segments. Subsequently, optical piston error detection experiments were conducted in a segmented mirror system under simulated turbulent conditions with varying turbulence intensities. Experimental studies have shown that the detection accuracy of the optical method is almost the same as without turbulence when using a detection aperture size that is 0.82 times the atmospheric coherence length and an exposure time of at least 40 ms. The root mean square of the cross-calibration is better than 3nm. These experimental results indicate that under conditions of good atmospheric seeing, the optical piston error detection method can meet the short-term calibration requirements of edge sensors by setting reasonable detection area size and exposure time. It may even be possible to directly use optical detection methods to replace edge sensors for real-time detection of piston errors.

A Concept of 2U Spaceborne Multichannel Heterodyne Spectroradiometer for Greenhouse Gases Remote Sensing

We present the project of a 2U CubeSat format spaceborne multichannel laser heterodyne spectroradiometer (MLHS) for studies of the Earth’s atmosphere upper layers in the near-infrared (NIR) spectral range (1258, 1528, and 1640 nm). A spaceborne MLHS operating in the solar occultation mode onboard CubeSat platform, is capable of simultaneous vertical profiling of CO2, H2O, CH4, and O2, as well as Doppler wind measurements, in the tangent heights range of 5–50 km. We considered the low Earth orbit for the MLHS deployment and analyzed the expected surface coverage and spatial resolution during one year of operations. A ground-based prototype of the MLHS for CO2 and CH4 molecular absorption measurements with an ultra-high spectral resolution of 0.0013 cm−1 is presented along with the detailed description of its analytical characteristics and capabilities. Implementation of a multichannel configuration of the heterodyne receiver (four receivers per one spectral channel) provides a significant improvement of the signal-to-noise ratio with the reasonable exposure time typical for observations in the solar occultation mode. Finally, the capability of building up a tomographic picture of sounded gas concentration distributions provided by high spectral resolution is discussed.

3-D Measurement Method for Nonuniform Reflective Objects

For 3-D measurement of nonuniform reflective objects, it is necessary to ensure measurement accuracy, reduce the number of additional images, and improve measurement efficiency. To satisfy these requirements, we first present a pixel matching method for projected and captured images. Second, we obtain the optimal projected image from two additional images. Finally, we propose a method to estimate reasonable exposure time. Experimental results show that the method can reconstruct 3-D shape of the metal, plastic, and colored objects with minimum of root mean square error (RMSE) 0.095, 0.068, and 0.079, respectively.

Study on the Allowable Exposure Time of Temporary Goaf in the Open Stope and Backfill Mining Method with Large Structure Parameters

Based on the uniaxial rheological experiment data of iron ore rock mass and filling body in large‐scale stope obtained by using the rock servo controlling creep equipment, the characteristics of the creep curve were analyzed. The creep models of iron ore and filling body which can show the attenuation creep of rock were constructed. And a nonlinear creep model was obtained. According to the rheological data of the iron ore and the filling body, the parameters of the new nonlinear creep model were identified to obtain the material parameters of the creep model. Then, the creep model parameters were fitted and reduced to calculate the reasonable exposure time of temporary goaf in the large‐scale stope. The results show that the reasonable exposure time of stope is 520 ～ 650 days, and the reasonable exposure time of filling body is 410 ～ 520 days. The model can well describe the initial attenuation creep stage and steady creep stage in the creep curve, which proves the correctness and rationality of the model. The study provides a reference for mining design and safety production of similar mines with large‐scale stope structure.

A novel and fast three-dimensional measurement technology for the objects surface with non-uniform reflection

Optical three-dimensional (3D) measurement of non-diffuse objects is challenging. At present, a common used method is to adjust the camera’s sensitivity several times to get fringe sequences with different brightness, and then extract the appropriate pixels for 3D shape reconstruction. However, the disadvantages of this method are obvious, including the large number of fringes needed, many useless redundant images, large amount of computation and time-consuming. In this paper, a novel method is proposed, which includes four major steps. Firstly, we set the intensity of the projected fringes to be maximum to ensure that the captured fringes have a good signal-to-noise ratio (SNR). Secondly, two sets of additional fringes are pre-captured to estimate the reasonable exposure time interval. Thirdly, appropriate exposure time is selected and the high-speed projection technology is used. Finally, appropriate pixels are extracted from the fringe sequences for 3D reconstruction, and then multiple phases are calculated and fused. Compared with the existing methods, the proposed method does not capture useless fringe patterns, and greatly improves the measurement efficiency while guaranteeing satisfactory 3D measurement results.

Photoneutrons for Radiation Therapy and Radionuclide Production

The possibility of organizing neutron therapy with a photoneutron beam produced by the electron accelerator target, and ensuring the required dose at the tumor at a reasonable exposure time and with minimal impact on patients investigated. Generation of neutrons from the target of electron accelerator takes place in two stages: e- ® γ ® n, and in the selected electron energy range of 20-100 MeV, the bremsstrahlung gamma radiation in many times (~ 3 orders of magnitude) offers more than “useful” neutron yield. This raises the problem of the selective control of the “harmful” for radiotherapy secondary gamma radiation while providing the minimum attenuation of the neutron flux in the output beam. In order to solve the general problem of the formation of a neutron beam with necessary spectral characteristics having sufficient intensity, there has been resolved a number of computational tasks of the selection of the optimal configuration of the output beam unit and its composition. The matter of high importance is to minimize additional irradiation of the patient from the bremsstrahlung (generated by electrons) and secondary gamma radiation (generated by neutrons) from the accelerator target as well as from output unit’s materials. On the other hand, at a generation stage e- ® γ the bremsstrahlung beam could be applied for effective radionuclide production by reactions (γ,n) and (γ,p) due to high leak intensity ~ 1.3·1017 photon/s. By the Mo100(γ,n)99Mo reaction the main diagnostic nuclide 99Tc could be produced sufficiently for the clinical needs. The resulting configuration of the output unit provides the required beam quality for the neutron capture therapy (NCT), which commonly assumed to be the only competitive technology of neutron therapy on the background of the massive invasion of proton therapy and other highly selective techniques that ultimately damage the target sparing the surrounding tissues and organs. For the accessible accelerator (average current 4 mA and electron energy 35 MeV) the flux density of epithermal photoneutrons (they required for NCT) in the beam at the output is of the order of magnitude or more higher than the typical yield from existing and planned reactors' beams. The proposed scheme of generation and extraction of photoneutrons for NCT has a number of strong advantages over traditional techniques: a) the applying of electron accelerators for neutron production is much safer and cheaper than conventional reactor beams in use; b) accelerator with the target, the beam output unit with the necessary equipment can be placed on the territory of the clinic without any problems of radiation safety; c) the proposed target – liquid gallium, which also serves as a cooler, is an “environmentally friendly” material due to low activation which rapidly (in ~ 4 days) falls to the background level.

Cone-Beam CT Virtual Navigation-Guided Percutaneous Needle Biopsy of Suspicious Pleural Metastasis: A Pilot Study.

ObjectiveTo evaluate the diagnostic performance of cone-beam computed tomography (CBCT) virtual navigation-guided percutaneous pleural biopsy for suspected malignant pleural disease.Materials and MethodsThis study enrolled 59 patients (31 males and 28 females; mean age, 63.4 years) with suspected malignant pleural disease diagnosed with CBCT from December 2010 to December 2016. Sixty-three CBCT-guided biopsies were performed using a coaxial system with 18- or 20-gauge cutting needles. Procedural details, diagnostic performance, radiation exposure, and complication rates were investigated.ResultsThe mean diameter perpendicular to the pleura of 51 focal and 12 diffuse pleural lesions was 1.53 ± 0.76 cm. The mean distance from the skin to the target was 3.40 ± 1.51 cm. Mean numbers of CT acquisitions and biopsies were 3.21 ± 0.57 and 3.05 ± 1.54. Total procedure time and coaxial introducer indwelling time were 11.87 ± 5.59 min and 8.78 ± 4.95 min, respectively. The mean dose area product was 12013.61 ± 7969.59 mGym2. There were 48 malignant, 10 benign, and 5 indeterminate lesions. Sensitivity, specificity, and diagnostic accuracy were 93.8% (45/48), 100% (10/10), and 94.8% (55/58), respectively. Positive and negative predictive values for malignancy were 100% (45/45) and 76.9% (10/13), respectively. Four patients (6.8%) with benign pathology during initial biopsy but still showing a high suspicion of malignancy underwent repeat biopsy and three of them were finally diagnosed with malignant pleural disease. There were three cases of minimal pneumothorax and no grave procedure-related complications.ConclusionCone-beam computed tomography-guided biopsy is an accurate and safe diagnostic technique for suspected malignant pleural lesion with reasonable radiation exposure and procedure time.

Slit identification for a uranium slab using a binary classifier based on cosmic-ray muon scattering

Traditional muon tomographic method has been fraught with difficulty when it is applied to identify some defective high-Z objects or other complicated structures, since it usually gets into trouble when attempting to produce a precise three-dimensional image for such objects. In this paper, we present a binary classifier based on cosmic-ray muon scattering to identify the slit potentially located in a uranium slab. The superiority of this classifier is established by steering clear of the stubborn imaging procedure necessary for the conventional methods. Simulation results demonstrate its capability to spot a horizontal or vertical slit with a reasonable exposure time. The minimum width of a spotted slit is on the level of millimeters or even sub-millimeters. Therefore, this technique will be prospective in terms of monitoring the long-term status of nuclear storage and facilities in real life.

In Vitro Bactericidal Effects of 625, 525, and 425 nm Wavelength (Red, Green, and Blue) Light-Emitting Diode Irradiation

The purpose of this study was to evaluate the relationship of 625, 525, and 425 nm wavelengths, providing average power output and effects on three common pathogenic bacteria. Ultraviolet (UV) light kills bacteria, but the bactericidal effects of UV may not be unique, as 425 nm produces a similar effect. The bactericidal effects of light-emitting diode (LED) wavelengths such as 625 and 525 nm have not been described. Before conducting clinical trials, the appropriate wavelength with reasonable dose and exposure time should be established. The bactericidal effects of 625, 525, and 425 nm wavelength LED irradiation were investigated in vitro for the anaerobic bacterium Porphyromonas gingivalis and two aerobes (Staphylococcus aureus and Escherichia coli DH5α). Average power output was 6 mW/cm(2) for 1 h. The bacteria were exposed to LED irradiation for 1, 2, 4, and 8 h (21.6, 43.2, 86.4, and 172.8 J/cm(2), respectively). LED irradiation was performed during growth on agar and in broth. Control bacteria were incubated without LED irradiation. Bacterial growth was expressed in colony-forming units (CFU) and at an optical density at 600 nm in agar and broth. The bactericidal effect of LED phototherapy depended upon wavelength, power density, bacterial viable number, and bacteria species. The bactericidal effect of 425 and 525 nm irradiation varied depending upon the bacterial inoculation, compared with unirradiated samples and samples irradiated with red light. Especially, P. gingivalis and E. coli DH5α were killed by 425 nm, and S. aureus growth was inhibited by 525 nm. However, the wavelength of 625 nm was not bactericidal for P. gingivalis, E. coli DH5α, or S. aureus. Irradiation at 625 nm light was not bactericidal to S. aureus, E. coli, and P. gingivalis, whereas wavelengths of 425 and 525 nm had bactericidal effects. S. aureus was also killed at 525 nm.

High molecular weight polystyrene as very sensitive electron beam resist

Graphical abstractDisplay Omitted Highlights? We studied electron beam exposure properties of high molecular weight polystyrene. ? Its sensitivity increases linearly with molecular weight. ? For 900kg/mol, the sensitivity is 1.1µC/cm2 when exposed at 2keV. ? The sensitivity is one order higher than PMMA and ZEP-520A. ? Line array patterns of 100nm half pitch can be well defined in polystyrene. Previously we demonstrated ultra-dense patterning using 2kg/mol polystyrene negative electron beam resist that has low sensitivity 16]. To drastically improve its sensitivity, here we studied the exposure behavior of polystyrene with molecular weight of 90 and 900kg/mol. Very high sensitivity of 1µC/cm2 was obtained for 900kg/mol when exposed at 2keV. The sensitivity for 90kg/mol polystyrene is about one order lower. The resist has a contrast around 1.5 that is nearly independent of molecular weight for the current range of molecular weight. It can achieve fairly well-defined patterns of 150-200nm period line arrays. Polystyrene is a simple and low-cost resist with easy process control and practically unlimited shelf life. It is also considerably more resistant to drying etching than PMMA. Therefore, the current high molecular weight polystyrene could be employed for applications that need moderate resolution but high sensitivity for a reasonable exposure time.

Hygrothermal aging of composite single lap shear specimens comprised of AF-555M adhesive and T800H/3900-2 adherends

Fiber reinforced resin matrix composites and structural adhesives have found increased usage on commercial and military aircraft. These structural materials offer weight savings without sacrificing strength and mechanical performance. Since service history and long-term aging performance of these relatively new material systems are not well established, a long-term environmental aging study was undertaken. Adhesive bonds were prepared by secondary bonding of 3M™ Scotch-Weld™ AF-555M between pre-cured, unidirectional composite adherends comprised of Toray™ T800H/3900-2 prepreg. Single lap shear specimens (SLS) were fabricated and subsequently aged in an unstressed configuration at 82°C (180°F) and 85% relative humidity for up to 772 days. The aging conditions are more severe than those expected to occur in service and were selected in order to observe some changes within a reasonable exposure time. The apparent shear strengths were measured periodically at both room temperature and 82°C (180°F), and failure modes were determined and compared to control specimens that had been stored for equal periods of time at room temperature under low humidity. With hygrothermal aging, apparent shear strengths decreased and some changes in the failure mode were observed relative to those of the control specimens. However, in spite of the severe aging conditions, no adhesive failures indicative of interfacial failures were observed. SLS specimens that were hygrothermally aged, subsequently dried, and then tested did not exhibit complete recovery of unaged apparent shear strengths indicating some irreversible changes.

Rest-frame ultraviolet-to-optical spectral characteristics of extremely metal-poor and metal-free galaxies

Finding the first generation of galaxies in the early Universe is the greatest step forward for understanding galaxy formation and evolution. For strategic survey of such galaxies and interpretation of the obtained data, this paper presents an ultraviolet-to-optical spectral model of galaxies with a great care of the nebular emission. In particular, we present a machine-readable table of intensities of 119 nebular emission lines from Ly$\alpha$ to the rest-frame 1 $\mu$m as a function of metallicity from zero to the Solar one. Based on the spectral model, we present criteria of equivalent widths of Ly$\alpha$, He {\sc ii} $\lambda1640$, H$\alpha$, H$\beta$, [O {\sc iii}] $\lambda5007$ to select extremely metal-poor and metal-free galaxies although these criteria have uncertainty caused by the Lyman continuum escape fraction and the star formation duration. We also present criteria of broad-band colours which will be useful to select candidates for spectroscopic follow-up from drop-out galaxies. We propose the line intensity ratio of [O {\sc iii}] $\lambda5007$ to H$\beta$ $<0.1$ as the most robust criterion for $<1/1000$ of the Solar metallicity. This ratio of a galaxy with a few $M_\odot$ yr$^{-1}$ at $z\sim8$ is detectable by spectroscopy with the James Webb Space Telescope within a reasonable exposure time.

Beginning of Open Use of a New Biological Neutron Diffractometer (iBIX) in J-PARC

Ibaraki Prefectural Government together with Ibaraki University and Japan Atomic Energy Agency (JAEA) has almost finished constructing a time-of-flight (TOF) neutron diffractometer for biological macromolecules for industrial use at J-PARC, IBARAKI Biological Crystal Diffractometer (iBIX). Since 2009, Ibaraki University has been asked to operate this machine in order for users to do experiments by Ibaraki Prefecture. The diffractometer is designed to cover sample crystals which have their cell edges up to around 150 A. It is expected to measure more than 100 samples per year if they have 2 mm(3) in crystal volume, and to measure even around 0.1 mm(3) in crystal volume of biological samples. The efficiency of iBIX is also expected about 100 times larger than those of the present high performance diffractometers at JRR-3 in JAEA when 1MW power realizes in J-PARC. Since December 2008, iBIX has been open to users and several proteins and organic compounds were tested under 20 kW proton power of J-PARC. It was found that one of their proteins was diffracted up to 1.4 A in d-spacing, which was nearly comparable resolution to that of BIX-3 in JRR-3 when used the same crystal as at iBIX for reasonable exposure time. In May 2009, 14 detector units were set up. By the end of fiscal year 2009, the basic part of data reduction software will be finished and an equipment blowing low temperature gas to the sample will be installed with the cooperation of JAEA.

Relationship between Sensitivity and Transmittance of Novolac Resist Exposed to Light Emitting Diodes

Sensitivity of the novolac positive resist THMR iP-3300 to violet and blue light emitting diodes with central wavelengths of 404-470 nm was investigated to utilize for developing a new numbering exposure system using a matrix array of such light emitting diodes. In addition, the spectral transmittance of the resist was measured, and the relationship between transmittance and sensitivity was discussed. It was clarified that the sensitivity greatly differed between exposures to violet and blue light rays as much as more than 30 times, and the resist was sensitized only by 3 s exposure to the violet light at minimum. Therefore, reasonable exposure time performance will be obtained if the relevant reduction projection lens is applied.

High-pressure x-ray cell for studying the structure of fluids with the energy-dispersive technique

A cell for x-ray diffraction studies of fluids with the energy-dispersive technique at pressures of up to 9–10 kbar has been designed. The main advantages of the apparatus are a simple design, reliable sealing, absence of contribution from the container to the measured intensity of scattering, and high accuracy of intensity measurements achievable in a reasonable exposure time.

Spatial coherence of a repetitive laser-plasma point x-ray source in the water window spectral region

We propose and demonstrate a coherent laser-plasma point x-ray source in the water window spectral region operating at a repetition rate of up to 100 Hz. The emission from the 10-μm-diameter source is filtered to generate monochromatic radiation at a 3.37 nm wavelength. Soft x-ray fringes of the Young’s interference experiment were obtained with a visibility of 0.62±0.1 with a slit pair of 10.5 μm separation at a distance of 31.7 cm from the source. The source can be used to take either a hologram or transmission scanning x-ray micrograph within a reasonable exposure time of several minutes.

Fundamental approach to service life of flexible membrane liner's (FML's)

Predicting the service life of flexible membrane liners (FML's) exposed to chemicals has usually been done by physical or mechanical changes after exposure. The report summarized here presents an alternative approach--that to water for periods up to fifteen months were tested by five different chemicals and transport related measurements. The results indicated that monitoring the transport properties of FML's exposed to particular chemicals over a reasonable exposure time could be considered as one possible method for predicting an FML's lifetime.

Chemical Mass Transport Measurements to Determine Flexible Membrane Liner Lifetime

Abstract The prediction of the service life of flexible membrane liners (FMLs) when exposed to chemicals has usually been by way of testing for physical or mechanical property changes after periodic exposure times. This paper presents an alternate approach by evaluating the chemical properties via five different mass transport related measurements of the exposed FML. These tests are water vapor transmission (WVT), radioactive tracer transmission (RT), water absorption (WA), water vapor absorption (WVA), and benzene absorption (BA). This approach was tested for exposures of up to 15 months. The FMLs used were polyvinyl chloride (PVC), ethylene-propylene-diene monomer (EPDM), chlorinated polyethylene (CPE), and high density polyethylene (HDPE). The chemicals used were 10% sodium hydroxide (NaOH) (in water), 10% sulfuric acid (H2SO4) (in water), 10% phenol (in water), 100% xylene, and water (as a control). The WVT and RT were found to be quite reliable test methods, whereas the WA and WVA techniques experienced serious problems in regard to obeying simple one-dimensional diffusion theory. The BA method worked well for HDPE. The various transport coefficients showed all the expected types of behavior with chemical exposure: (1) constancy with exposure (acids and bases on most all FMLs and all chemicals on HDPE), (2) decrease with exposure (plasticizers leaching from FMLs), and (3) increase with exposure (Phenol-treated CPE). The WVT and RT results were generally complimentary to one another. The transport approach was quite successful in predicting the instability of CPE exposed to phenol. This instability was further verified by differential scanning calorimetry measurements. The work reported herein lends credence to the use of mass transport measurements to determine structural change in FMLs. Thus the monitoring of transport properties, over a reasonable exposure time to particular chemicals, could serve as the basis for a predictive method for FML lifetime.

Optimised tomography for clinical use.

A technique elaborated by the present authors (1974) for the establishment of optimum tomographic movements was applied to ear tomography in order to design a movement that is not too complex, but yielding good tomographic depiction. Such a movement was found to consist of a spiral of 5 revolutions. Modern engineering appears to allow such complex movements to be carried out with satisfactory stability within a reasonable exposure time.