Changes In Surface Shape Research Articles

Thermoelectric coefficient of nanoscale transition metals films

We study the thermoelectric coefficient of island transition metal films as a function of temperature and film thickness. We show that the thermoelectric coefficient value is determined by the properties of the film metal element and is different for different metals at dimensionless conductance value g>1 and g<1. The main factor in the behavior difference of the thermoelectric coefficient as a function of temperature is the individual characteristics of the Fermi surface of each metal. Dependence of the thermoelectric coefficient on the film thickness is also determined by the Fermi surface shape change. Keywords: Island film, Thin film, Thermopower, Thermoelectric coefficient, Conductivity.

Термоэдс наноразмерных пленок переходных металлов

We study the thermoelectric coefficient of island transition metal films as a function of temperature and film thickness. We show that the thermoelectric coefficient value is determined by the properties of the film metal element and is different for different metals at dimensionless conductance value g>1 and g<1. The main factor in the behavior difference of the thermoelectric coefficient as a function of temperature is the individual characteristics of the Fermi surface of each metal. Dependence of the thermoelectric coefficient on the film thickness is also determined by the Fermi surface shape change.

Calculation of barrier potential height using fraction parameter

Nucleus deformation refers to a change in the nucleus surface shape. The expression of the radius of the nucleus can represent this deformation. Generally, these radii are expansions involving spherical harmonics. In addition, some divide the nucleus shape into three parts. The left and right ends are spherical, while the middle or neck uses the hyperbolic function. The deformation shape does not contain the fraction of the nucleus fragments. In fact, including all possible fraction values will provide all the probability that occurs. These probabilities can be accumulated to determine the value of the potential barrier height. Based on this reason, a technique was developed to include the fragment fraction as part of the input variable. This technique is intended to be able to use experimental data from fission products. Namely, as input to get a potential barrier height. By changing the function expression for the radius of the nucleus, the fragment fraction can insert into the function. For this purpose, the method is to form the three parts of the nuclear radius. The first part is the head in the form of spherical harmonics. The second part is the neck which has a shape like hyperbolic cosines. By applying the continuity condition between the neck and the head, the fraction parameter becomes the expansion coefficient of the spherical harmonics. This technique shows fairly good calculation results. The figure of the potential barrier height shows the results of these calculations. It is through comparisons between this work and several other works that two main conclusions are drawn. First, the insertion of fraction parameters at the nucleus radius was successfully carried out. Second, the fission yield data can be used as input for calculating the fission barrier height.

Kinetics and mechanisms of stress relaxation in sputtered silver thin films

The post-growth stress relaxation in thin polycrystalline Ag films, deposited by direct-current magnetron sputtering under different growth conditions, was explored through wafer curvature measurements. It exhibits exponential behaviour with three distinct characteristic time components τ. The slowest one, namely τth≃200 s, is ascribed to thermal stress inherent to the deposition method. In fact, the performed temperature measurements match perfectly with an exponential stress variation with heating or cooling, as predicted by a thermal exchange model detailed in this work. Based on a comparison between different deposition conditions (continuous/interrupted sputter deposition and evaporation), the case of Mo deposition and stress relaxation modelling, the remaining components are assigned to the out-diffusion of atoms from grain boundaries (τgb≃3 s) and to changes in the grain surface shape induced by grain boundary grooving (τsurf≃20 s). The relaxation amplitude of the first mechanism varies linearly with the steady-state stress at the end of growth in agreement with theoretical expectations. Yet, that of the second one does not. However, clues point to a kinetic limitation of atomic diffusion mechanism along grain boundaries. This study provides proofs of the simultaneous occurrence of several mechanisms of stress relaxation in thin metallic films.

Patterns of Sulcal depth and cortical thickness in Parkinson's disease.

Previous voxel-based morphometry (VBM) and cortical thickness (CT) studies on Parkinson's disease (PD) have mainly reported the gray matter size reduction, whereas the shape of cortical surface can also change in PD patients. For the first time, we analyzed sulcal depth (SD) patterns in PD patients by using whole brain region of interest (ROI)-based approach. In a cross-sectional study, high-resolution brain structural MRI images were collected from 60 PD patients without dementia and 56 age-and sex-matched healthy controls (HC). SD and CT were estimated using the Computational Anatomy Toolbox (CAT12) and statistically compared between groups on whole brain ROI-based level using statistical parametric mapping 12 (SPM12). Additionally, correlations between regional brain changes and clinical variables were also examined. Compared to HC, PD patients showed lower SD in widespread regions, including temporal (the bilateral transverse temporal, the left inferior temporal, the right middle temporal and the right superior temporal), insular (the left insula), frontal (the left pars triangularis, the left pars opercularis and the left precentral), parietal (the bilateral superior parietal) and occipital (the right cuneus) regions. For CT, only the left pars opercularis showed lower CT in PD patients compared to HC. No regions showed higher SD or CT in PD patients compared to HC. In PD patients, a significant positive correlation was found between SD of the left pars opercularis and MMSE scores, such that lower MMSE scores were related to lower SD of the left pars opercularis. Our results of widespread lower SD, but relatively localized lower CT, indicate that SD seems to be more sensitive to brain changes than CT and may be mainly affected by white matter damage. Hence, SD may be a more promising indicator to investigate the surface shape changes in PD patients. The significant positive correlation between SD of the left pars opercularis and MMSE scores suggests that SD may be prognostic of future cognitive decline.

Three-Dimensional Evaluation of Soft Tissue Malar Modifications after Zygomatic Valgization Osteotomy via Geometrical Descriptors.

Patients with severe facial deformities present serious dysfunctionalities along with an unsatisfactory aesthetic facial appearance. Several methods have been proposed to specifically plan the interventions on the patient’s needs, but none of these seem to achieve a sufficient level of accuracy in predicting the resulting facial appearance. In this context, a deep knowledge of what occurs in the face after bony movements in specific surgeries would give the possibility to develop more reliable systems. This study aims to propose a novel 3D approach for the evaluation of soft tissue zygomatic modifications after zygomatic osteotomy; geometrical descriptors usually involved in face analysis tasks, i.e., face recognition and facial expression recognition, are here applied to soft tissue malar region to detect changes in surface shape. As ground truth for zygomatic changes, a zygomatic openness angular measure is adopted. The results show a high sensibility of geometrical descriptors in detecting shape modification of the facial surface, outperforming the results obtained from the angular evaluation.

Evaluation of Grinding Wheel Surface Shape on Difference Multiple Helical Dressing Condition

In the grinding process, a grinding wheel surface is a tool that is directly applied to the workpiece. As the condition of the grinding wheel surface is determined by its dressing conditions, the ability to accurately measure the grinding wheel surface with an applied dressing would enable the prediction of the ground surface characteristics of the workpiece as well as the determination of optimum dressing conditions. Recently, a new dressing method called the multiple helical dressing was proposed, which has led to improvements in the grinding performance. However, there is still no method to quantitatively evaluate the changes in the grinding wheel surface condition caused by multiple helical dressings. In this study, we measured the grinding wheel surface applied with multiple helical dressings using a so-called measured focus position recalculation method to determine whether we can quantitatively evaluate the measured dressing grooves generated on the grinding wheel surface by multiple helical dressings, and the resultant undulated grinding wheel surface shapes. We ground an actual workpiece to demonstrate the effects of changes in the grinding wheel surface shape due to multiple helical dressings on the ground surface of the workpiece. The experimental results show that our proposed measuring method can accurately measure the changes in the grinding wheel surface condition due to multiple helical dressings. We also proposed a method to evaluate the dressing grooves to prove that we can quantitatively evaluate the measurement results of dressing grooves generated by multiple helical dressings. In addition, we evaluated undulated grinding wheel surface shapes as its cylindricities by extracting only the undulation shapes generated by multiple helical dressings. Finally, we performed groove grinding with a grinding wheel applied with multiple helical dressings to reveal the relationship between the ground surface of the workpiece and the grinding wheel surface condition, which demonstrated the effectiveness of multiple helical dressings.

Optical properties of combined dynamic thermal dynamicloading optical window

Aiming at the large aperture optical window working in the complex environment such as pressure difference and temperature gradient, a combination scheme of optical window was proposed, which was composed of optical glass and acrylic plate. Based on the thermal-optical analysis, the overall strength and thermal environment of optical window were analyzed and calculated theoretically, and the minimum thickness of optical window glass was obtained. The pressure field and axial temperature field were mapped to three-dimensional structure model by finite element software. The surface shape change and imaging quality evaluation index of 380 mm diameter optical window under different glass thickness were calculated. The simulation results were verified by corresponding environmental tests. The results show that the thickness of large aperture optical window with K9 optical glass as raw material is not less than 32.5 mm under this working environment; when the thickness of optical window is 35 mm, the thermodynamic effect can be ignored. Therefore, the large aperture combined optical window of 35 mm can not only meet the intensity, but also meet the imaging quality requirements of multi-spectral camera, which provides a basis for the design of this kind of window.

Effect of water spray on degradation of styrene-butadiene-rubber during accelerated weathering tests

Accelerated weathering tests using a xenon lamp were performed on styrene-butadiene rubber (SBR) under two conditions: only photo irradiation (photo-irradiated condition) and the addition of intermittent water spraying to photo irradiation (photo-irradiated/water-sprayed condition). Degradation mechanisms under these conditions were evaluated based on changes in chemical structure, hardness, and morphology of the exposed surface during weathering tests. The morphology of the exposed surfaces differed significantly between the two weathering conditions. Random minute cracks, known as crazes, were clearly observed under the photo-irradiated/water-sprayed condition. To clarify the origin of such craze propagation, the temperature change accompanying water spraying was traced. A combination of temperature decrease during water spraying and subsequent increase due to water evaporation was repeated under the photo-irradiated/water-sprayed condition. Such periodic temperature change caused the sample to expand and contract; however, the exposed surface could not follow this dimensional change, resulting in craze. This result indicates that water spraying is a degradation factor for accelerated weathering tests on SBR, especially change of surface shape.

Fabrication and characterization of a novel silk fibroin film with UV and thermal resistance

Silk fibroin is an excellent material for use in tissue engineering owing to its biocompatibility and biodegradability. For proper sterilization, it is necessary to investigate the properties of the material after irradiation with ultraviolet rays prior to implementation. In this study, grinded silk fibroin (GF) films with an ultraviolet (UV)-resistant property using a grinding method without the application of an organic solvent have been successfully prepared. A regenerated silk fibroin (RF) film using a conventional method was also prepared as a comparative sample. The Fourier transform infrared spectroscopy (FT-IR) and atomic force microscope (AFM) results show that the surface of the RF film was photo-oxidized with UV-C light irradiation and that the fibroin molecular chains were decomposed. Furthermore, the modulus of the RF film decreased. However, almost no oxidation deterioration or shape change of the film surface occurred when UV-C light was irradiated on the developed GF film, indicating that the thermal-decomposition temperature and mechanical properties maintained their initial values. These results strongly suggest that GF films prepared using the novel approach have superior thermal and mechanical properties compared with RF films prepared through a conventional method. In addition, GF films achieve a superior UV-C resistance property.

Design of High-lightweight Space Mirror Component Based on Automatic Optimization

Aiming at the problems of high weight, low cost and extremely short development cycle faced by commercial aerospace space remote sensing cameras, a mathematical model with modal fundamental frequency as the objective function under the constraints of weight and size has been established. Through the automatic optimization method, the lightening rate of the mirror can reach 71.8%. Using the “2 + 2 + 2” quasi-static constraint as the criterion, the flexible support structure of the mirror is optimally designed to realize the high rigidity of the component and ensure the high bearing capacity of the force and thermal environment. Static simulation analysis of the design results of the mirror assembly using hypermesh shows that under the combined influence of gravity field and temperature field, the change of the mirror surface shape (RMS) is within 0.0056λ. At the same time, the modal analysis of the design results shows that the first-order natural frequency of the component can reach 146.52 Hz, which has extremely high dynamic stiffness. It can effectively adapt to the dynamic environment, and the design of the mirror assembly can fully meet the needs of commercial aerospace space remote sensing cameras.

Coupled simulation for reentry ablative behavior of hypersonic vehicles

Numerical analyses of hypersonic vehicles ablative behaviors focus on the accurate models of the thermochemical reaction flow field. The assumptions of chemical equilibrium and non-catalytic wall cannot meet the ablative behavior prediction requirements for high Mach number flights with multiphase materials. In this paper, the numerical analysis of hypersonic vehicle reentry involves the nonequilibrium thermochemical flow field and thermodynamic structure with moving boundary. Two surface models, finite rate catalysis model and Park finite rate surface interaction model were applied into the flow field simulation. And the reentry ablative behaviors of two hypersonic vehicles were simulated by the partitioning methods using the computational fluid dynamics code Fluent and the material thermal and structural response code Abaqus with user defined codes. And the two codes were loosely coupled in time to exchange the data. The structural temperature, surface shape change at the wall under different reentry altitudes and various angles of attack were obtained. The validity and reliability of frame work set up were validated with previous work.

Modeling of the worm cutter in the process of cutting the gears

This work offers a new approach to graphical modeling of worm cutter parameters, based on analyses and synthesis of simple kinematic movements, causing its cutting elements a single move and displacement when placing metal into a hollow between spikes of the gear, which is being cut. It is one of the most difficult cutting and shaping processes, combining four kinematic movements – rotation of the cutters, their axial feed, rotation of the billet and a constructive move – displacement of cutting elements, located on the principle worm helix along the cutter axis. The modeling difficulty is that the cutting surface constantly changes its location and form in relation to the spikes. This surface is formed on the billet as a kind of a transition surface between the untreated surface, the partly treated surface and the partly treated hollow between the spikes of the gear, which is being cut. Its formation is participated by all the spikes, which have performed the cutting during all the time before a certain moment. Continuous change of the transition surface shape and size determines the shape and size of the shavings and the cross-sectional parameters of the spikes slices and the tool blades, and its reproduction is a base for a correct quantitative assessment of the cutting parameters of individual blades and spikes of the cutter. In its turn, complete and authentic information about the cross-sections and the shape and size of metal layers cut during the spike milling is a base for calculating and analysis of the cutting power, the friction force, the thermal processes, fluctuations and vibrations. The algorithm of an instant surface formation between the gear spikes and the shavings 3D geometry on all of the active spikes of the tool are realized in AutoCAD graphic system. Here are given the results of computer modeling of the shavings when using the Archimedean cutter with counter feed. Complete information about geometrical structure of the cut off layers creates the base for a detailed and system modeling of this process abreast the separate warm cutter rails, the spikes and the blades. In combination with intensity of the plastic deformation data, the tension and the temperature received in Deform system for a certain spike milling condition, the parameters of the cut layers data referred in this work, create the condition for thermo prognostication and the cutting elements waste, their power load, strength protective coatings, cutting force and temperature transition processes, optimum technological processes of spike milling projecting and its managing.

Analysis according to the change in structure of ultrasonic sensors and the change in pressure inside the tank for measurement of fuel amounts in compressed natural gas (CNG) tank

AbstractThe present study is a fundamental research for precise measurement of fuel amounts in a compressed natural gas (CNG) tank where an analysis of receiving sensitivity was conducted as a result of changes in the contact surface shape in the number of piezoelectric element of the ultrasonic sensor as well as in the internal pressure of the tank. Experiments were conducted as a function of changes in the contact surface shape between the ultrasonic sensor and outside of the aluminum tank and in the number of piezoelectric element as well as in the internal pressure of the tank. According to the experimental results, it could be confirmed that the maximum receiving sensitivity value was increased by about 60 % when the contact surface shape of the transmission and receiving ultrasonic sensors compared with the ultrasonic sensor in the Line‐Line shape selected as the reference model was changed to the surface. As a whole, the highest receiving sensitivity values were observed when the transmission sensor of surface shape produced as multiple piezoelectric elements and the receiving sensor of surface shape produced as a single piezoelectric element were used. It could be confirmed that receiving sensitivities were improved at the same voltage value as a result of changes in the contact surface shape of the ultrasonic sensor and in the number of piezoelectric elements.

THE FORMATION OF SURFACE NANOSTRUCTURES ON As-S-Ge CHALCOGENIDE FILM AFTER E-BEAM EXPOSURE

Проблематика. Халькогенідні стекла формують унікальний клас матеріалів та є привабливими з точки зору їх різноманітних застосувань, що обумовлені їхніми непересічними властивостями та можливістю утворювати поверхневий рельєф. Взаємодія цих матеріалів з електронним променем становить інтерес через різноманітність фізичних явищ, спричинених у халькогенідних плівках лазерним опроміненням. Мета дослідження. Дослідження прямого (без селективного травлення) формування поверхневого рельєфу періодичних наноструктур на плівці As 3 S 77 Ge 20 товщиною ~8,3 мкм, виготовленій вакуумним термічним випаровуванням, із використанням електронно-променевої літографії. Вивчення зміни висоти і форми поверхневих наноструктур залежно від дози опромінення. Методика реалізації. Хімічний склад плівки визначали за допомогою енергетично-дисперсійного аналізу рентгенівських променів. Плівку опромінювали електронним променем за допомогою скануючого електронного мікроскопа. Було досліджено вплив опромінення електронним пучком на аморфну халькогенідну тонку плівку As 3 S 77 Ge 20 . Поверхневий рельєф плівки сканували атомно-силовим мікроскопом. Результати дослідження. Доза експозиції G варіювалась від 12 мКл·см - 2 до 12 Кл·см - 2 . Було виявлено формування конусів із гаусовим профілем на поверхнях плівок після локального опромінення електронами. Встановлено залежність висоти одержаних поверхневих наноструктур від дози експозиції. Видно, що для G 2400 мКл·см - 2 вона зменшується. Було знайдено початкову та інверсійну дози формування поверхневого рельєфу. Для матриць із відстанню між точками опромінення d = 6,6 мкм початкова доза становила G 0 = 9,60 мКл·см - 2 , а інверсійна – G i = 31,18 Кл·см - 2 . Для d = 10 мкм ці параметри дорівнювали G 0 = 6,98 мКл·см - 2 і G i = 36,19 Кл·см - 2 . Залежності у зростаючому інтервалі дози (від 16 до 1200 мКл·см - 2 ) для d = 6,6 мкм і d = 10 мкм було апроксимовано експоненційними функціями. Висновки. Зміну форми та параметрів отриманого рельєфу поверхні на плівці As 3 S 77 Ge 20 можна пояснити моделлю акумулювання заряду. Наші дослідження показали, що вивчена композиція As 3 S 77 Ge 20 придатна для запису електронним променем та може бути використана для виготовлення оптичних елементів.

空间遥感相机大口径反射镜结构优化设计

In order to satisfy the stringent requirement for high surface shape accuracy and thermal stability of large-aperture mirrors in the complex space environment, a lightweight design for a Φ660 mm-diameter mirror was carried out. A method for creating the initial structure of the mirror using the classical theoretical formula, combining sensitivity analysis and parameter optimization for comprehensive design was proposed. Firstly, the parametric model was established, the influence law of the structure parameters of the mirror on the surface shape change was studied, and then iterations for the structural parameters with high sensitivity to the mirror surface RMS value were optimized through sensitivity analysis. Compared with the traditional mirror design model, this method reduced the optimization design space, saved computational cost and time, could globally optimize in the design space, and converged quickly to the optimal value. The mass of optimized mirror was 13.6 kg and the lightweight rate of the mirror reached 78.4%. The PV value of mirror surface accuracy was less than λ/10 and RMS value was less λ/40(λ=632.8 nm) under gravity load. The first-order frequency 121 Hz of the mirror assembly met the dynamic stiffness requirements of the mirror. Finally, based on the optimized results, the optimal mirror was put into production.

Voice production in a MRI-based subject-specific vocal fold model with parametrically controlled medial surface shape.

The goal of this study was to investigate how realistic changes in medial surface shape, as occur in human phonation, affect voice production. In a parametric magnetic resonance imaging-based three-dimensional vocal fold model, the superior and inferior portions of the medial surface were systematically manipulated to produce different medial surface contours similar to those observed in previous excised larynx and in vivo canine larynx experiments. Voice simulations were performed to investigate the differences in the resulting voice production. The results showed that both superior-medial bulging and inferior-medial bulging of the medial surface, which led to an increased vertical thickness and a more rectangular glottal configuration, increased the closed quotient of vocal fold vibration. Changes in medial surface shape also had significant effects on the phonation threshold pressure. The degree of these effects of changes in medial surface shape was larynx specific, and varied significantly depending on the vocal fold cross-sectional geometry and its variation along the anterior-posterior direction. The results suggest that, in addition to vocal fold approximation, surgical interventions of voice disorders should also aim at restoring a rectangular and sufficiently thick medial surface.

LDeform: Longitudinal deformation analysis for adaptive radiotherapy of lung cancer.

Conventional radiotherapy for large lung tumors is given over several weeks, during which the tumor typically regresses in a highly nonuniform and variable manner. Adaptive radiotherapy would ideally follow these shape changes, but we need an accurate method to extrapolate tumor shape changes. We propose a computationally efficient algorithm to quantitate tumor surface shape changes that makes minimal assumptions, identifies fixed points, and can be used to predict future tumor geometrical response. A novel combination of nonrigid iterative closest point (ICP) and local shape-preserving map algorithms, LDeform, is developed to enable visualization, prediction, and categorization of both diffeomorphic and nondiffeomorphic tumor deformations during an extended course of radiotherapy. We tested and validated our technique on 31 longitudinal CT/MRI subjects, with five to nine time points each. Based on this tumor deformation analysis, regions of local growth, shrinkage, and anchoring are identified and tracked across multiple time points. This categorization in turn represents a rational biomarker of local response. Results demonstrate useful predictive power, with an averaged Dice coefficient and surface mean-squared error of 0.85 and 2.8mm, respectively, over all images. We conclude that the LDeform algorithm can facilitate the adaptive decision-making process during lung cancer radiotherapy.

Effect of changes in medial surface shape on voice production in excised human larynges.

Clinical intervention of glottal insufficiency often focuses on correcting glottal gap as visualized from above. In contrast, changes in medial surface shape due to intervention have received less attention. This study investigated how changes in medial surface shape affect voice production in excised human larynges, by locally medializing the medial surface at different longitudinal and vertical locations. The results showed that localized medialization at a more inferior location yielded better improvement in glottal closure and higher-order harmonic excitation in the produced voice. This study shows that surgical intervention of glottal insufficiency should also aim at restoring desirable medial surface shape.

Effect of medial surface shape on voice production in a MRI-based three-dimensional phonation model

Our previous studies using simplified vocal fold geometry have shown that medial surface shape, particularly the vertical thickness, has an important effect on the closure pattern of vocal fold vibration. The goal of this study is to investigate if similar effect can be observed for medial surface shape that occurs in realistic human phonation, using a parametric MRI-based three-dimensional vocal fold model. Manipulation of medial surface shape is achieved through a two-level control of the superior and inferior portion of the medial surface, based on experimental observations. Simulations show that, in general, both superior-medial bulging and inferior-medial bulging of the medial surface, which leads to an increased vertical thickness and a more rectangular glottal configuration, increase the closed quotient of the vocal fold vibration. Changes in medial surface shape also have significant effect on the phonation threshold pressure. This effect of the medial surface shape varies significantly across larynges, indicating the important effect of subject-specific laryngeal geometry. The results point to the importance of taking into consideration of the medial surface shape in clinical management of voice disorders. [Work supported by NIH.]