Numeric Simulation of Single Passage Ternary Turbulence Model in Hydraulic Torque Converter

Based on the renormalization group theory, a hydraulic torque converter 3 D turbulent single flow passage model is constructed and boundary condition is determined for analyzing the influence of the fluid field characteristic and parameters on the macroscopic model. Numerical simulation of the single fluid path is processed by computational fluid dynamics and the calculated results approach to experimental data well, and especially in low transmission ratio the torque and head results are more close to experimental data than the calculated results of beam theory. This shows that the appropriate ternary analysis method and reasonable assumption of boundary condition may analyze the flow field more precisely and predict the performance of torque converter more accurately.

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (I center dot 4.6 mm x 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 mu m. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

A survey of high-speed high-resolution current steering DACs

Digital to analog converters(DAC)play an important role as a bridge connecting the analog world and the digital world.With the rapid development of wireless communication,wideband digital radar,and other emerging technologies,better performing high-speed high-resolution DACs are required.In those applications,signal bandwidth and high-frequency linearity often limited by data converters are the bottleneck of the system.This article reviews the state-of-the-art technologies of high-speed and high-resolution DACs reported in recent years.Comparisons are made between different architectures,circuit implementations and calibration techniques along with the figure of merit(FoM)results.

Numerical simulation of the flow field of a flat torque converter

A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.

血清GSDMD、ACE2在小儿川崎病中的表达水平及临床意义研究

目的 探索血清焦孔素蛋白D(GSDMD)、血管紧张素转化酶2(ACE2)在小儿川崎病(KD)患儿中的表达水平及临床意义。方法 收集2020年1月至2022年1月该院诊治的90例KD患儿为KD组,根据KD患儿是否发生冠状动脉损伤(CAL),将KD组分为CAL组(32例)和非CAL组(58例),选取同期因急性呼吸道感染发热住该院的患儿50例为发热对照组,另选取同期该院儿外科行择期手术的腹股沟斜疝患儿50例为对照组。采用酶联免疫吸附试验检测血清GSDMD、ACE2水平。Pearson相关分析血清GSDMD、ACE2与临床指标的相关性。多因素Logisitic回归分析KD患者发生CAL的影响因素。受试者工作特征(ROC)曲线分析血清GSDMD、ACE2对KD患儿发生CAL的诊断价值。结果 KD组血清GSDMD、ACE2水平高于发热对照组和对照组,差异有统计学意义(均P<0.05)。相比于非CAL组,CAL组KD患儿发热持续时间、丙种球蛋白治疗时间、红细胞沉降率、血小板计数、C反应蛋白、GSDMD、ACE2水平均明显较高,而血钠、白蛋白明显较低,差异有统计学意义(均P<0.05)。Pearson相关分析结果,KD组患儿血清GSDMD、ACE2水平与发热持续时间、丙种球蛋白治疗时间、红细胞沉降率、血小板计数、C反应蛋白呈正相关(均P<0.05),与血钠、白蛋白呈负相关(均P<0.05)。多因素Logistic回归分析结果显示,血清GSDMD、ACE2升高是影响KD患儿发生CAL的独立危险因素。ROC曲线分析结果显示,血清GSDMD、ACE2两项联合检测KD患儿发生CAL的曲线下面积(AUC)及其95%CI为0.918(0.868~0.949),明显大于血清GSDMD、ACE2单项检测的AUC及其95%CI[依次为0.838(0.789~0.887)、0.865(0.811~0.912)],差异有统计学意义(Z=5.116、4.217,均P<0.05)。结论 血清GSDMD、ACE2两项联合检测对于KD患儿发生CAL具有较高的诊断价值。

Virtual Anatomy: The Dissecting Theatre of the Future—Implementation of Cinematic Rendering in a Large 8 K High-Resolution Projection Environment

Modern computer techniques have been in use for several years to generate three-dimensional visualizations of human anatomy. Very good 3-D computer models of the human body are now available and used routinely in anatomy instruction. These techniques are subsumed under the heading “virtual anatomy” to distinguish them from the conventional study of anatomy entailing cadavers and anatomy textbooks. Moreover, other imaging procedures (X-ray, angiography, CT and MR) are also used in virtual anatomy instruction. A recently introduced three-dimensional post-processing technique named Cinematic Rendering now makes it possible to use the output of routine CT and MR examinations as the basis for highly photo-realistic 3-D depictions of human anatomy. We have installed Cinematic Rendering (enabled for stereoscopy) in a high-definition 8K 3-D projection space that accommodates an audience of 150. The space’s projection surface measures 16 × 9 meters;images can be projected on both the front wall and the floor. A game controller can be used to operate Cinematic Rendering software so that it can generate interactive real-time depictions of human anatomy on the basis of CT and MR data sets. This prototype installation was implemented without technical problems;in day-to-day, real-world use over a period of 22 months, there were no impairments of service due to software crashes or other technical problems. We are already employing this installation routinely for educational offerings open to the public, courses for students in the health professions, and (continuing) professional education units for medical interns, residents and specialists—in, so to speak, the dissecting theater of the future.

Performance Optimization of Torque Converters Based on Modified 1D Flow Model

A methodology for performance optimization of torque converters is put forward based on the one-dimensional (1D) flow model. It is found that the inaccuracy of 1D flow model for predicting hydraulic performance at the low speed ratio is mainly caused by the separation phenomenon at the stator cascade which is induced by large flow impinging at the pressure side of the stator blades. A semi-empirical separation model is presented and incorporated to the original 1D flow model. It is illustrated that the improved model is able to predict the circumferential velocity components accurately, which can be applied to performance optimization. Then, the Pareto front is obtained by using the genetic algorithm (GA) in order to inspect the coupled relationship among stalling impeller torque capacity, stalling torque ratio and efficiency. The efficiency is maximized on the premise that a target stalling impeller torque capacity and torque ratio are achieved. Finally, the optimized result is verified by the computational fluid dynamics(CFD) simulation, which indicates that the maximal efficiency is increased by 0.96%.

Deep-large faults controlling on the distribution of the venting gas hydrate system in the middle of the Qiongdongnan Basin, South China Sea

Many locations with concentrated hydrates at vents have confirmed the presence of abundant thermogenic gas in the middle of the Qiongdongnan Basin(QDNB).However,the impact of deep structures on gasbearing fluids migration and gas hydrates distribution in tectonically inactive regions is still unclear.In this study,the authors apply high-resolution 3D seismic and logging while drilling(LWD)data from the middle of the QDNB to investigate the influence of deep-large faults on gas chimneys and preferred gasescape pipes.The findings reveal the following:(1)Two significant deep-large faults,F1 and F2,developed on the edge of the Songnan Low Uplift,control the dominant migration of thermogenic hydrocarbons and determine the initial locations of gas chimneys.(2)The formation of gas chimneys is likely related to fault activation and reactivation.Gas chimney 1 is primarily arises from convergent fluid migration resulting from the intersection of the two faults,while the gas chimney 2 benefits from a steeper fault plane and shorter migration distance of fault F2.(3)Most gas-escape pipes are situated near the apex of the two faults.Their reactivations facilitate free gas flow into the GHSZ and contribute to the formation of fracture‐filling hydrates.

Analytical Modelling and Experiment of Novel Rotary Electro-Mechanical Converter with Negative Feedback Mechanism for 2D Valve

The manufacturing of spiral groove structure of two-dimensional valve(2D valve)feedback mechanism has shortcomings of both high cost and time-consuming.This paper presents a novel configuration of rotary electro-mechanical converter with negative feedback mechanism(REMC-NFM)in order to replace the feedback mechanism of spiral groove and thus reduce cost of valve manufacturing.In order to rapidly and quantitative evaluate the driving and feedback performance of the REMC-NFM,an analytical model taking leakage flux,edge effect and permeability nonlinearity into account is formulated based on the equivalent magnetic circuit approach.Then the model is properly simplified in order to obtain the optimal pitch angle.FEM simulation is used to study the influence of crucial parameters on the performance of REMC-NFM.A prototype of REMC-NFM is designed and machined,and an exclusive experimental platform is built.The torque-angle characteristics,torque-displacement characteristics,and magnetic flux density in the working air gap with different excitation currents are measured.The experimental results are in good agreement with the analytical and FEM simulated results,which verifies the correctness of the analytical model.For torque-angle characteristics,the overall torque increases with both current and rotation angle,which reaches about 0.48 N·m with 1.5 A and 1.5°.While for torque-displacement characteristics,the overall torque increases with current yet decrease with armature displacement due to the negative feedback mechanism,which is about 0.16 N·m with 1.5 A and 0.8 mm.Besides,experimental results of conventional torque motor are compared with counterparts of REMC-NFM in order to validate the simplified model.The research indicates that the REMC-NFM can be potentially used as the electro-mechanical converter for 2D valves in civil servo areas.

The Design of A/D Converter Circuit Adopting the Technology of PWM

This text has expounded the working principle of realizing A/D conversion that utilizes the timer within MCU and combinesthe technology of PWM. The design of hardware circuit, improved gradual approached trial arithmetic and relevant program design arediscussed in detail. And it has analyzed the resolution of A/D converter based on the technology of PWM, etc.

基于层次分析法与改进D-S理论的阀水冷系统状态评估

为了及时评估保障换流阀可靠运行的阀水冷系统运行状态,首先,分析了换流站阀水冷系统整体构成,选取主要历史数据和实时数据构建了评估指标体系,通过三角形函数和半梯形函数以及专家调查法确定各个指标的隶属度;其次,基于层次分析法确定各个评估指标权重,改进D-S理论建立阀水冷系统运行状态评估模型;最后,通过采集实际工程阀水冷系统主要指标数据对模型进行了验证,并以阀水冷系统滤芯清洗前后数据为例对评估结果进行了对比。结果表明,所建模型能够对阀水冷系统运行状态做出准确识别和评估,有利于运维人员及时掌控阀水冷系统运行状态,保障其可靠运行。

高精度高摆幅多工位ADC测试系统设计

基于V93000 ATE设计了一种采用外加电源升压变换模块及可变增益仪器仪表运算放大器,以解决大输入摆幅高精度多工位ADC的量产测试需求的测试方案。理论分析和测试验证结果表明,该ADC测试系统可分别产生峰峰值超过29 V的Ramp波和正弦波测试信号,测试信号SNR优于105 dB、THD优于-103 dB,可以满足16 bit、±10 V甚至以上高输入摆幅多工位ADC的大批量量产测试需求。

一种国产化高精度小体积R/D转换器设计

为了满足整机系统的高质量等级、高可靠性、高集成度、小型化和全国产化的需求,采用裸芯片组装及金属全密封封装技术方式,同时利用高精度、低温度系数薄膜电阻网络的优势,解决了R/D转换器产品高精度、高分辨率、高质量等级、小体积等方面的关键技术难题,最终实现了角度模拟信号和数字信号的相互转换,满足系统对角度参量实施量化处理与控制的需求。

COVID-19相关性肌肉减少症发生机制及防治的研究进展

新型冠状病毒感染(COVID-19)已被世界卫生组织宣布为大流行病。研究发现,COVID-19幸存患者患急性肌肉减少症和潜在肌肉功能不全的风险增加。肌肉减少症(肌少症)是一种严重肌肉功能不全的病症,以骨骼肌质量和功能下降为特征,严重影响生活质量,且伴随不良后果风险增加。COVID-19可通过多种机制导致肌少症的发生,包括血管紧张素转化酶2(ACE2)缺失、炎症、长期卧床与体力活动减少、缺氧、食物摄入不足、糖皮质激素应用。COVID-19相关性肌少症的防治方法很多,包括加强运动、补充蛋白质及热量、补充长链ω-3脂肪酸和补充维生素D。

基于D-S的特高压换流站设备故障诊断模型的建立与运用

为了实现特高压换流站的智能化运维管理,基于数据融合和D-S证据理论技术,构建特高压换流站设备故障诊断模型,该模型自上而下包括数据层融合、特征层融合以及决策层融合三层结构,通过对比D-S证据合成算法、逻辑回归分类算法以及集成树分类算法的诊断效果,结果表明本文建立的故障诊断模型的平均召回率较逻辑回归分类算法以及集成树分类算法分别提升2.15%和1.17%,较传统故障分类算法具有一定的优越性,可在电力设备故障诊断中予以应用。

基于FPGA的ADS8686S采样控制器的设计与实现

在某弹载遥测项目开发中,为了实现A/D转换芯片ADS8686S对多路传感器信号的采集,设计了一种基于FPGA的传感器信号采样控制器。首先简单介绍了ADS8686S的指标参数,其次分析了芯片的并行接口控制时序,在此基础上,重点讨论了控制器的软件设计方案。在保证采样精度和速度的同时,控制器可对ADS8686S的工作状态进行实时监测,提高了采样的可靠性。控制器已在多次遥测试验中得到验证。

高精度稳流电源控制系统中ADC、DAC芯片的应用

介绍了由高性能 14位D/A转换芯片MX75 34、2 4位A/D转换芯片AD7714与 89C5 1单片机连接而组成的高精度稳流电源控制系统的原理 ,给出了接口电路和编程方法。

基于FPGA的DDS多路信号源设计

提出了一种基于FPGA的DDS多路信号源的原理方案和实现方法。该信号源以高精度D/A转换器为核心构成波形重构电路,使用电子模拟开关实现多路信号输出切换。设计的信号源可同时输出32路,波形信号可为正弦波、锯齿波、三角波和矩形波,且输出信号的频率、幅值和偏置灵活可调。

逐次逼近A/D转换器综述

从逐次逼近A/D转换器(SA-A/D)的工作原理出发,分别对其核心模块D/A转换器和比较器进行了讨论。SA-A/D转换器中的D/A转换器可分为电压定标、电流定标和电荷定标三种,重点分析了三种目前应用较多的并行电容、分段电容和RC混合结构。SA-A/D转换器中的比较器可分为运放结构比较器和锁存(latch)比较器,实际常常使用这两种结构级联的高速高精度比较器,并配合失调校准技术,达到较高精度。最后,简要总结了SA-A/D转换器的研究现状,阐述了其在精度、速度和功耗三个方面的发展状况。

一种用于ADC电路的高速高精度比较器设计

在分析各种比较器设计失调消除技术基础上,提出了一种用于ADC电路的高速高精度比较器设计技术和失调消除技术.该比较器由主动复位和被动箝位的预放大器和输出锁存器构成,具有失调自动校准功能.仿真结果表明,在Chartered 0.35μm COMS工艺下,电源电压3.3 V,调整后的比较器失调误差为56.8μV,比较器的精度0.1mV,比较速率100 MHz.