Initial testing of ohmic heating through double flux swing during electron cyclotron start-up in the QUEST spherical tokamak

A power-supply system was developed for Ohmic heating(OH)to double×10^(18)the amount of change magnetic flux in the primary central solenoid(CS)on the QUEST spherical tokamak.Two power supplies are connected with stacks of insulated-gate bipolar transistors,and sequentially operated to generate positive and negative CS currents.This bipolar power-supply system is controlled via a field-programmable gate array,which guarantees the safety of the entire system operation.The new OH system,assisted by electron cyclotron heating,enables the stable generation of plasma currents exceeding 100 k A.Moreover,the achieved electron density over the wide range in the major radial direction exceeds the cut-off density for one of the highpower microwave sources in QUEST.This strategy yields target plasmas for future experiments with the electron Bernstein wave.

Induction heating for desorption of surface contamination for high-repetition laser-driven carbon-ion acceleration

This study reports the first experimental demonstration of surface contamination cleaning from a high-repetition supply of thin-tape targets for laser-driven carbon-ion acceleration.The adsorption of contaminants containing protons,mainly water vapor and hydrocarbons,on the surface of materials exposed to low vacuum(>10^(−3)Pa)suppresses carbon-ion acceleration.The newly developed contamination cleaner heats a 5-μm-thick nickel tape to over 400℃in 100 ms by induction heating.In the future,this heating method could be scaled to laserdriven carbon-ion acceleration at rates beyond 10 Hz.The contaminant hydrogen is eliminated from the heated nickel surface,and a carbon source layer—derived from the contaminant carbon—is spontaneously formed by the catalytic effect of nickel.The species of ions accelerated from the nickel film heated to various temperatures have been observed experimentally.When the nickel film is heated beyond∼150℃,the proton signal considerably decreases,with a remarkable increase in the number and energy of carbon ions.The Langmuir adsorption model adequately explains the temperature dependence of desorption and re-adsorption of the adsorbed molecules on a heated target surface,and the temperature required for proton-free carbon-ion acceleration can be estimated.

Coupled simulation of BES-CFD and performance assessment of energy recovery ventilation system for office model

Thermal comfort and indoor air quality as well as the energy efficiency have been recognized as essential parts of sustainable building assessment.This work aims to analyze the energy conservation of the heat recovery ventilator and to investigate the effect of the air supply arrangement.Three types of mixing ventilation are chosen for the analysis of coupling ANSYS/FLUENT(a computational fluid dynamics(CFD) program) with TRNSYS(a building energy simulation(BES) software).The adoption of mutual complementary boundary conditions for CFD and BES provides more accurate and complete information of indoor air distribution and thermal performance in buildings.A typical office-space situated in a middle storey is chosen for the analysis.The office-space is equipped with air-conditioners on the ceiling.A heat recovery ventilation system directly supplies fresh air to the office space.Its thermal performance and indoor air distribution predicted by the coupled method are compared under three types of ventilation system.When the supply and return openings for ventilation are arranged on the ceiling,there is no critical difference between the predictions of the coupled method and BES on the energy consumption of HVAC because PID control is adopted for the supply air temperature of the occupied zone.On the other hand,approximately 21% discrepancy for the heat recovery estimation in the maximum between the simulated results of coupled method and BES-only can be obviously found in the floor air supply ventilation case.The discrepancy emphasizes the necessity of coupling CFD with BES when vertical air temperature gradient exists.Our future target is to estimate the optimum design of heat recovery ventilation system to control CO2 concentration by adjusting flow rate of fresh air.

Effect of lower bainite/martensite/retained austenite triplex microstructure on the mechanical properties of a low-carbon steel with quenching and partitioning process

We present a study concerning Fe-0. 176C-1.31Si-1.58Mn-0.26Al-0.3Cr （wt%） steel subjected to a quenching and partitioning （Q＆P） process. The results of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tensile tests demon- strate that the microstructures primarily consist of lath martensite, retained austenite, lower bainite （LB）, and a small amount of tempered martensite; moreover, few twin austenite grains were observed. In the microstrucmre, three types of retained austenite with different sizes and morphologies were observed： blocky retained austenite （-300 nm in width）, film-like retained austenite （80-120 nm in width）, and ul- tra-fine film-like retained austenite （30-40 nm in width）. Because of the effect of the retained austenite/martensite/LB triplex microstructure, the specimens prepared using different quenching temperatures exhibit high ultimate tensile strength and yield strength. Furthermore, the strength effect of LB can partially counteract the decreasing strength effect of martensite. The formation of LB substantially reduces the amount of retained austenite. Analyses of the retained austenite and the amount of blocky retained austenite indicated that the carbon content is critical to the total elongation of Q＆P steel.

Effects of topography on the sub-tidal circulation in the southwestern Huanghai Sea(Yellow Sea)in summer

A nested circulation model system based on the Princeton ocean model （POM） is set up to simulate the currentmeter data from a bottom-mounted Acoustic Doppler Profiler （ADP） deployed at the 30 m depth in the Lunan（South Shandong Province, China） Trough south of the Shandong Peninsula in the summer of 2008, and to study the dynamics of the circulation in the southwestern Huanghai Sea （Yellow Sea）. The model has reproduced well the observed subtidal current at the mooring site. The results of the model simulation suggest that the bottom topography has strong steering effects on the regional circulation in summer. The model simulation shows that the Subei （North Jiangsu Province, China）coastal current flows north- ward in summer, in contrast to the southeastward current in the center of the Lunan Trough measured by the moored currentmeter. The analyses of the model results suggest that the southeastward current at the mooring site in the Lunan Trough is forced by the westward wind-driven current along the Lunan coast, which meets the northward Subei coastal current at the head of the Haizhou Bay to flow along an offshore path in the southeastward direction in the Lunan Trough. Analysis suggests that the Subei coastal current, the Lunan coastal current, and the circulation in the Lunan Trough are independent current systems con- trolled by different dynamics. Therefore, the current measurements in the Lunan Trough cannot be used to represent the Subei coastal current in general.

Overview of wall probes for erosion and deposition studies in the TEXTOR tokamak

An overview of diagnostic tools e test limiters and collector probes e used over the years for material migration studies in the TEXTOR tokamak is presented.Probe transfer systems are shown and their technical capabilities are described.This is accompanied by a brief pre-sentation of selected results and conclusions from the research on material erosion e deposition processes including tests of candidate materials(e.g.W,Mo,carbon-based composites)for plasma-facing components in controlled fusion devices.The use of tracer techniques and methods for analysis of materials retrieved from the tokamak are summarized.The impact of research on the reactor wall technology is addressed.

Biomechanical Study of Vertebral Compression Fracture Using Finite Element Analysis

This research aimed to mechanically analyze vertebral stress concentration in one healthy subject and one subject with osteoporotic first lumbar (L1) vertebral compression fracture by using finite element analysis (FEA). We constructed three-dimensional image-based finite element (FE) models (Th12L2) by using computed tomographic (CT) digital imaging and communications in medicine (DICOM) for each patient and then conducted exercise stress simulations on the spine models. The loadings on the 12th thoracic vertebra (Th12) due to compression, flexion, extension, lateral bending, and axial rotation were examined within the virtual space for both spine models. The healthy and vertebral compression fracture models were then compared based on the application of equivalent vertebral stress. The comparison showed that vertebral stress concentration increased with all stresses in the vertebral compression fracture models. In particular, compression and axial rotation caused remarkable increases in stress concentration in the vertebral compression fracture models. These results suggest that secondary vertebral compression fractures are caused not only by bone fragility but possibly also by the increase in vertebral stress concentration around the site of the initial

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN's Xuan Long-50(EXL-50)

A millimeter wave solid state source—far infrared laser combined interferometer system(MFCI)consisting of a three-channel 890 GHz hydrogen cyanide(HCN)laser interferometer and a threechannel 340 GHz solid state source interferometer(SSI)is developed for real-time line-integrated electron density feedback and electron density profile of the EXL-50 spherical tokamak device.The interferometer system is a Mach–Zehnder type,with all probe-channels measured vertically,covering the plasma magnetic axis to the outermost closed magnetic plane.The HCN laser interferometer uses an HCN laser with a frequency of 890 GHz as a light source and modulates a100 k Hz beat signal by a rotating grating,giving a temporal resolution of 10μs.The SSI uses two independent 340 GHz solid-state diode sources as the light source,the frequency of the two sources is adjustable,and the temporal resolution of SSI can reach 1μs by setting the frequency difference of the two lasers at 1 MHz.The main optical path of the two interferometers is compactly installed on a set of double-layer optical platform directly below EXL-50.Dual optical path design using corner cube reflectors avoids the large support structures.Collinear the probebeams of two wavelengths,then the phase error caused by vibration can be compensated.At present,the phase noise of the HCN Interferometer is 0.08 rad,corresponding to a line-integrated electron density of 0.88×10^(17)m^(-2),one channel of measuring result was obtained by the MFCI system,and the highest density measured is about 0.7×10^(19)m^(-2).

Microstructural evolution and mechanical properties of a low-carbon quenching and partitioning steel after partial and full austenitization

In this work, low-carbon steel specimens were subjected to the quenching and partitioning process after being partially or fully austenitized to investigate their microstructural evolution and mechanical properties. According to the results of scanning electron microscopy and transmission electron microscopy observations, X-ray diffraction analysis, and tensile tests, upper bainite or tempered martensite appears successively in the microstructure with increasing austenitization temperature or increasing partitioning time. In the partially austenitized specimens, the retained austenite grains are carbon-enriched twice during the heat treatment, which can significantly stabilize the phases at room temperature. Furthermore, after partial austenitization, the specimen exhibits excellent elongation, with a maximum elongation of 37.1%. By contrast, after full austenitization, the specimens exhibit good ultimate tensile strength and high yield strength. In the case of a specimen with a yield strength of 969 MPa, the maximum value of the ultimate tensile strength reaches 1222 MPa. During the partitioning process, carbon partitioning and carbon homogenization within austenite affect interface migration. In addition, the volume fraction and grain size of retained austenite observed in the final microstructure will also be affected.

Experimental Study of Owl-Like Airfoil Aerodynamics at Low Reynolds Numbers

This study experimentally investigates aerodynamic characteristics and flow fields of a smooth owl-like airfoil without serrations and velvet structures. This biologically inspired airfoil design is intended to serve as the main-wing for low-Reynolds-number aircrafts such as micro air vehicles. Reynolds number dependency on aerodynamics is also evaluated at low Reynolds numbers. The results of the study show that the owl-like airfoil has high lift performance with a nonlinear lift increase due to the presence of a separation bubble on the suction side. A distinctive flow feature of the owl airfoil is a separation bubble on the pressure side at low angles of attack. The separation bubble switches location from the pressure side to the suction side as the angle of attack increases and is continuously present on the surface within a wide range of angles of attack. The Reynolds number dependency on the lift curves is insignificant, although differences in the drag curves are especially pronounced at high angles of attack. Eventually, we obtain the geometric feature of the owl-like airfoil to increase aerodynamic performance at low Reynolds numbers.

Biomechanical Study of the Effects of Balloon Kyphoplasty on the Adjacent Vertebrae

We used the finite element method (FEM) to investigate the stress profiles of vertebrae in patients who underwent balloon kyphoplasty (BKP) for vertebral fracture. BKP is often performed for persistent pain after vertebral fractures. However, fractures are frequently reported in the adjacent vertebrae after BKP. The purpose was to clarify the mechanism of fractures that occur in the adjacent vertebrae after BKP. The subjects were two patients (first case: 74-year-old woman;second case: 88-year-old woman) who had BKP for osteoporotic vertebral fractures (L1). A bone analysis software program, Mechanical Finder, was used to construct three-dimensional finite element models (T11-L3) from computed tomographic (CT) digital imaging and communications in medicine (DICOM) data. Moment loadings were examined to evaluate stress concentrations on the vertebrae. Young’s moduli were lower in the second case than in the first case at all vertebral levels. Maximum Drucker-Prager stresses after BKP were larger in the second case than in the first case for compression, flexion, extension, and axial rotation. Strain energy density decreased in L1 and increased in the adjacent ver-tebrae. Our results suggest that post-BKP fractures of the adjacent vertebrae not only are due to bone fragility, but also can be caused by increased rigidity in the vertebrae filled with bone cement, which increases stress concentration on the adjacent verte-brae and raises the likelihood of fracture.

Sensing Characteristics of Mixed-Potential-Type YSZ-Based NO_x Sensor Using Au-Doped NiO Sensing Electrode

The nano-structured NiO powder obtained by sol-gel method was doped with 10 wt% gold in order to modify its morphology as well as its electrochemical catalytic activity.The NO_x sensing characteristics of mixed-potential-type YSZ-based planar sensors attached with each of the nano-NiO and the Au-doped nano-NiO materials as a sensing electrode SE) were examined at temperatures of 700℃～800℃.The Au-doped NiO-SE was found to give a large enhancement in the NO_2 sensitivity as well as the NO_2 selectivity at 800℃under wet condition,in comparison with the pure NiO-SE.The reason for the improvement in the NO_2 sensitivity was examined based on the data of polarization curves,impedance spectra and catalytic activity for the gas-phase NO_2 decomposition.

Two-dimensional Numerical Simulation of an Elastic Wedge Water Entry by a Coupled FDM-FEM Method

影响平静的水表面的有弹性的楔的 Hydroelastic 行为被调查。由联合有限差别方法(频分多路复用) 和有限元素方法的一条划分途径(女性) 被开发分析液体结构相互作用(FSI ) 问题。频分多路复用，限制插值侧面(CIP ) 方法在被使用，被用于在一个固定常规笛卡儿的格子系统解决流动地。免费表面被双曲线的正切为接口与斜坡 Weighting (THINC/SW ) 计划捕获捕获。女性被申请计算结构的变丑。体积加权的方法，它基于沉浸的边界(IB ) 方法，为一起联合 FDM 和 FEM 被采用。一个有弹性的楔水入口问题被联合频分多路复用女性的方法计算。另外在当前的数字结果和出版结果之间的比较显示联合频分多路复用女性的方法在预言影响力量有相当好的精确性。

Magnetic Sensorless Control of Plasma Position and Shape in a Tokamak

Magnetic sensorless sensing and control experiments with the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made to focus on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem with the integrator of wagnetic sensors. Two kinds of control experiments have been carried out： to keep the position constant and swing the position in a triangular waveform, And magnetic sensorless sensing of plasma shape is discussed.

Magnetohydrodynamic effect of internal transport barrier on EAST tokamak

An internal transport barrier(ITB)can be formed on EAST in exploring high-parameter operation.Previous studies show that safety factor(q)profiles,Shafranov shift and magnetohydrodynamic behaviors could be helpful in ITB formation by suppressing anomalous transport.Recently,electron density evolution with high resolution demonstrates that fishbone could be dominant in electron density ITB formation and sustainment.The power threshold is low in the fishbone condition and the electron density profile is determined by traits of fishbone.Simulation shows that the low-k ion mode is suppressed by fishbone.Direct measurement of turbulence in the inner region shows that the internal kink mode could sustain an electron temperature ITB by suppressing the trapped electron mode.The multi-scale interaction between the kink mode and turbulence by current could be key in sustaining high-electron-temperature long-pulse operation.

Non-Inductive Start up of QUEST Plasma by RF Powert

Both start-up and sustainment of plasma were successfully achieved by fully non- inductive current drive using microwave with a frequency of 8.2 GHz. Plasmas current of 15 kA was implemented for 1 s. Magnetic surface reconstruction exhibited a plasma shape with an aspect ratio of below 1.5. The plasma current was dependent significantly on the launched microwave power and vertical magnetic field, while not affected by the mode of launched wave and the toroidal refractive index. Hard X-ray （HXR） emitted from energetic electrons accelerated by the microwave was observed, and the discharge with a plasma current over 4 kA followed the same trend as the number of photons of 10 keV to 12 keV. This suggests that the plasma current may be driven by energetic electrons. Based on the experimental conditions, alternative explanations of how the plasma current could be driven are discussed.

Effects of Hip Arthroplasties on Bone Adaptation in Lower Limbs: A Computational Study

Gait disorders contribute to the risk of falls and successive injuries, especially to elderly populations. The risk of falls becomes higher for hip osteoarthritis (OA) and hip arthroplasties patients due to poor balancing and gait impairment. Bone adaptation and bone loss are fundamental issues in considering the changes of bone behavior and gait pattern. In this study, computational analysis of the lower limbs was conducted to estimate the bone adaptation after hip arthroplasties procedure. 3D inhomogeneous model of lower limb was developed from computed topography (CT- based) data of 79 years old patient with hip osteoarthritis problem in left limb. Two types of arthroplaties were constructed in the left limb, namely total hip arthroplasty and resurfacing hip arthroplasty using commercial biomedical software, Mechanical Finder v6.1. Prosthesis stem and acetabular cup of THA were modelled as titanium alloy material (E = 114 GPa, v = 0.34), femoral ball and bearing insert as alumina properties (E = 370 GPa, v = 0.22). Meanwhile, RHA implant was assigned as Co-Cr-Mo material (E = 230 GPa, v = 0.30). Contact between both implants and bone were considered to be perfectly bonded at the interface. A load case of quiet standing position was conducted in this analysis with 60 kg of the patients’ body weight. The load was applied at the cross sectional lumbar vertebra and fixed at the distal of femoral shafts. Results show different patterns of stress distribution in right and left (operated) limbs for hip OA, THA and RHA models. An indication of stress alteration on both limbs after arthroplasties suggested that the bone adaptation occurred. The higher percentage of change in the left limb projected that the adaptation was more critical in operated limb.

Application of Optical Flow Analysis to Shadowgraph Images of Impinging Jet

In this study, we apply the optical flow method to the time-series shadowgraph images of impinging jets using a high-speed video camera with high spatial and temporal resolution. This image analysis provides quantitative velocity vector fields in the object space without tracer particles. The analysis results clearly capture the details of the coherent vortex structure and its advection from the shear layer of the free jet. Although the results still leave challenges for the quantitative validation, the results show that this analysis method is effective for understanding the details of the physical phenomenon based on the quantitative values extracted from the shadowgraph images.

Analytical Solutions of Fukui-Ishibashi (FI) Model and Quick-Start (QS) Model

Through straightforward deduction procedure, we explicitly show analytical solutions for both Fukui-Ishibashi (FI) model and Quick-Start (QS) model, which are fundamental deterministic Cellular Automaton (CA), applied to traffic flow.

Turbulence Intensity Effects on a Leading-Edge Separation Bubble of Flat Plate Wing at Low-Reynolds Numbers

In this study, we experimentally investigate the effects of mainstream turbulence intensity (Ti) on a leading-edge separation bubble under low-Reynolds number (Rec) conditions range of 2.0 × 104 to 6.0 × 104. We used a flat plate to fix a separation point at the leading edge. Also, we visualized the behavior of the leading-edge separation bubble using the smoke wire technique and Particle Image Velocimetry (PIV) measurement. Furthermore, we measured the effect of Ti on the turbulent transition process in the separated shear layer using a hot-wire anemometer. The results indicate that the bypass transition for large Ti causes the turbulent transition, and so accelerates the reattachment of the separated shear layer. The results show that the bypass transition promotes the reattachment of the separated shear layer to maintain the leading-edge separation bubble on the upper surface even at high angles of attack, increasing the stall angle.