Thickness Compensation Research Articles

The Finite Element Analysis for Dimensional Accuracy in Roll Bending of Aluminum-Polymer Laminated Sheet

The padding assisted roll bending technology is the main method to manufacture the cylinder structure with variable thickness. In order to study the deformation behavior of the padding assisted roll bending process, a numerical simulation model of the aluminum-polymer laminated sheet three-roll bending is established based on the finite element method. In the numerical simulation model, the sheet material Al2024-T3 is selected elasto-plastic model, and the padding material nylon PA6-G is elastic model. Based on the simulation results, the following conclusions are drawn: the cylinder radius of the sheet Al2024-T3 decreases with decreasing of the ratio of the nylon PA6-G or increasing of the stroke of the upper roller; And in the direction of bend line, an appropriate thickness compensation of the nylon PA6-G can improve the consistency of the curvature of the sheet Al2024-T3.

Optimized Yield Curve Determination Using Bulge Test Combined with Optical Measurement and Material Thickness Compensation

Axisymmetric die and binder are typically used in the bulge test, where the test specimen is formed by increasing the level of oil pressure (Fig. 1). With this experimental setup a biaxial stress state is induced at the specimen dome, assuming that it is not influenced by friction. The increasing oil pressure in the region of the top of the dome is recorded and the deformation field measured during the forming process. The optical measurement system determines the coordinates, the deformations and the curvature on the outer surface. Based on the forthcoming ISO 16808 these results are directly used for the calculation of the flow curve. In order to determine the flow curve based on the bulge test, an analytical approach is needed for the computation of the stress state at the top of the dome.

Survey of compliance with European acceptability criteria for HVL and AEC

Half value layer (HVL) was measured for 226 general radiographic X-ray tube assemblies at 80 kV and for 53 dental X-ray tube assemblies at 70 kV, and evaluated by the previous (1997) and the new draft of European acceptability criteria (2009) for HVL as adopted from the IEC collateral standards. Fourteen per cent of the tested general radiography X-ray tube assemblies were subject to readjustment by the new criteria. In routine quality control tests, receptor entrance dose was estimated for 54 AEC systems by using post-exposure mAs values, taking into account the measured tube output at different tube potentials, HVL and estimated scattering for 10, 15 and 21 cm PMMA phantom. Receptor dose (third quartile) varied from 6.4 μGy at 60 kV to 3.8 μGy at 125 kV. The results correspond well to the draft criteria for maximum receptor dose of 10 μGy and for the patient thickness compensation.

Electricity generation from thermal irradiation governed by GaSb active layer

Abstract Electricity generation from thermal irradiation governed by GaSb diode has been systematically investigated in its normal and inverted configuration. It is demonstrated here that there is a critical base doping, 3 × 1017 cm−3, for the normal structure, and the superior output performance of p+/n structure with low base-doping would completely be switched to the n+/p structure when base doping larger than this critical one. Moreover, a spectrum-independent optimal doping concentration, Na = 1.5 × 1017 cm−3, is also observed for n+/p structure, and no doping-dependent thickness compensation between emitter and base layer can be observed for the inverted structure. To save the material consumption and device cost, the reasonable active layer can be constructed by 100–200 nm emitter and 5–7 μm base, offering the useful guideline to fabricate the GaSb cell on the economical but lattice-mismatched hetero-substrate.

Theoretical analysis of comparative patient skin dose and exposure technique approaches in planar radiography

AbstractA theoretical analysis of patient skin dose changes with manipulation of technique factors (mAs and kV) was carried out in order to obtain a description of the relationship between patient dose and the exposure technique approach employed. The standard exposure technique approaches in variable part thickness radiography of “fixed kVp” and “variable kVp” and the “15% rule” in constant part thickness radiography were analysed in terms of the changes in patient skin dose. Analytical expressions describing the variation of dose change ratios have been developed in respect of each approach and also in comparison between the two standard approaches. The resultant model is limited to essentially qualitative predictions due to its inherent limitation of neglecting secondary radiation at the entrance site of the beam, but nevertheless indicates some non intuitive benefits in utilisation of mAs (only) changes in compensating for the thinner part and for lower image densities, as well as indicating that most gain is to be had (in terms of lower skin dose), where only modest part thickness compensation is required. The model also describes the influence of the chosen voltage in a “reference technique” (upon which further compensatory changes in exposure factors are based) on the patient skin dose, when the variable kV approach is utilised.

Fundamental parameters analysis of RoHS elements in plastics

European Community Directive 2002∕95∕EC restricts the use of certain hazardous substances in electrical and electronic equipment. In particular, restrictions are placed on lead, mercury, cadmium, hexavalent chromium, and bromine (in polybrominated biphenyls or polybrominated diphenyl ethers). XRF is a convenient method for detecting the presence and measuring the amounts of these elements. Reliably quantifying all of these elements in plastics typically requires a large number of standards that are not yet readily available. Because of the light element matrix, using a “standardless” fundamental parameters method requires some reliance on the primary beam scatter, complicating the analysis algorithm and increasing the uncertainty. We have tested a simplified fundamental parameters method that determines the matrix via difference, requiring only one standard. The method was tested on a series of reference materials containing all of the regulated elements in a variety of plastic resins. One multi-element reference standard was used. It was necessary to include all of the additives in the specimens to achieve good quantitative accuracy. In addition, the scattered primary intensity was used in one set of tests to compensate for variations in specimen thickness. This thickness compensation was necessary to get acceptable results for Cd. Results were very promising, with average relative errors and relative standard deviations of about 10%.

Volumetric breast density estimation from full-field digital mammograms

A method is presented for estimation of dense breast tissue volume from mammograms obtained with full-field digital mammography (FFDM). The thickness of dense tissue mapping to a pixel is determined by using a physical model of image acquisition. This model is based on the assumption that the breast is composed of two types of tissue, fat and parenchyma. Effective linear attenuation coefficients of these tissues are derived from empirical data as a function of tube voltage (kVp), anode material, filtration, and compressed breast thickness. By employing these, tissue composition at a given pixel is computed after performing breast thickness compensation, using a reference value for fatty tissue determined by the maximum pixel value in the breast tissue projection. Validation has been performed using 22 FFDM cases acquired with a GE Senographe 2000D by comparing the volume estimates with volumes obtained by semi-automatic segmentation of breast magnetic resonance imaging (MRI) data. The correlation between MRI and mammography volumes was 0.94 on a per image basis and 0.97 on a per patient basis. Using the dense tissue volumes from MRI data as the gold standard, the average relative error of the volume estimates was 13.6%.

Mammogram registration: a phantom-based evaluation of compressed Breast Thickness variation effects

The temporal comparison of mammograms is complex; a wide variety of factors can cause changes in image appearance. Mammogram registration is proposed as a method to reduce the effects of these changes and potentially to emphasize genuine alterations in breast tissue. Evaluation of such registration techniques is difficult since ground truth regarding breast deformations is not available in clinical mammograms. In this paper, we propose a systematic approach to evaluate sensitivity of registration methods to various types of changes in mammograms using synthetic breast images with known deformations. As a first step, images of the same simulated breasts with various amounts of simulated physical compression have been used to evaluate a previously described nonrigid mammogram registration technique. Registration performance is measured by calculating the average displacement error over a set of evaluation points identified in mammogram pairs. Applying appropriate thickness compensation and using a preferred order of the registered images, we obtained an average displacement error of 1.6 mm for mammograms with compression differences of 1-3 cm. The proposed methodology is applicable to analysis of other sources of mammogram differences and can be extended to the registration of multimodality breast data.

Improvement of the optical coating process by cutting layers with sensitive monitoring wavelengths

For costly optical coatings, a precise monitoring method is necessary. A new monitoring method based on the selection of the most sensitive monitor wavelength is proposed. The most sensitive monitor wavelength is easy to find by a numerical analysis. The equation for the thickness compensation when a layer is over-shot or under-shot was derived. Several examples, including narrow-band pass filters, have been given to demonstrate that this new method is superior to the turning point method in the coating process.

Improvement on the Reliability of Flash EEPROM by Annealing after Self-Aligned Source Dry Etching

This paper describes the effect of annealing on the characteristics of cycling endurance and charge retention in flash electronically erasable programmable read-only memory (EEPROM) fabricated by self-aligned source (SAS) dry etching process which was used for the shrinkage of cell size. The annealing process was used for the recovery and thickness compensation of the tunnel oxide edge at which severe plasma damage was accumulated during the SAS dry etching process. Through the analysis of cycling endurance, it was clarified that charge traps and structural defects were generated at the tunnel oxide edge during the SAS dry etching process and they induced the degradation of cycling endurance of memory cells. The characteristics of charge retention were improved due to the structural recovery and the thickness compensation of the tunnel oxide edge. An analysis of the results from the measurement of charge retention and the examination of the tunnel oxide edge with high resolution transmission electron microscope, indicates that the thickness compensation of the tunnel oxide edge affected more positively the reduction of tail bits than the structural recovery of the tunnel oxide edge. © 2001 The Electrochemical Society. All rights reserved.

Thickness variation compensation in a Fabry–Perot modulator array using a self-tuned Fabry–Perot structure

A method is presented for compensating cavity thickness variations in conventional Fabry–Perot devices through the replacement of the input mirror with a holographic mirror, resulting in a self-tuned Fabry–Perot (STFP) device. The technique is suitable for integrating large arrays of electro-optic Fabry–Perot modulators with silicon circuitry. Experimental results of a STFP modulator are presented showing cavity thickness compensation of an electrooptic 9/65/35 bulk lead lanthanum zirconate titanate crystal having thickness variations corresponding to ~6 Fabry–Perot fringes in a 2.5×2.5mm2 area. The compensated modulator used an in situ recorded Fe-doped LiNbO3 holographic mirror, and had a uniform backreflection over a 2.5×2.5mm2 area.

On: “GRAVITY AND AEROMAGNETIC EXPLORATION IN THE PARADOX BASIN,” BY NELSON C. STEENLAND (GEOPHYSICS, FEBRUARY, 1961, PP. 73–89)

Following are some comments concerning Dr. Steenland’s discussion of gravity data in Professional Papers 316-A and 316-C of the U.S. Geological Survey. Dr. Steenland’s cylinder calculations are entirely dependent upon the regional anomaly removed. He obtained an anomaly of −40 mgal over Paradox Valley, whereas we obtained a residual anomaly of −32 mgal. The bottom 4,000 ft of Dr. Steenland’s cylinder contribute −5 mgal to the anomaly. Dr. Steenland’s analysis supposes that the only effective density contrasts are those attributable to variations in salt thickness or isostatic compensation.