绿色城市中心概念在南方丘陵地区的研究与应用——以湖南省安仁县行政中心区规划设计为例

本文针对大多数南方丘陵城市中心区规划建设中出现的自然生态环境破坏和空间形态特色的丧失等问题,提出建设绿色城市中心的设想,从规划原则、规划方法、规划效益三个层面分析绿色城市中心区和传统城市中心区的区别。并以湖南省安仁县行政中心区规划设计为例,遵循"规划结合自然"的原则,从规划思路、自然生态环境、空间框架构建等方面进行分析,最终实现"创造绿色城市中心"的目标。     

合成试验方法在VSC-HVDC换流阀短路电流试验中的应用

合成试验方法是用多套电源分别提供试品在试验中所需应力的试验方法。为检验由模块化多电平换流器(modular multi-level converter,MMC)构成的电压源换流器高压直流输电(voltage source converter based high voltage direct current,VSC-HVDC)换流阀设计的正确性及其对暂态工况应力的耐受性,研究了MMC阀暂态运行试验的试验方法,分析了与过电流关断试验和短路电流试验相关工况的应力,提出了2种等效试验方法,并将合成试验方法应用于试验电路的设计中,给出了试验电路与实际工况下阀的应力波形,结合关键应力等效性分析,验证了上述试验方法和试验电路的正确性和有效性。     

女性运动内衣穿着舒适性测试评价

为研究女性运动内衣面料和款式对其舒适性的影响,以9种不同面料成分和不同款式组合,制作9款160/84A号型的运动内衣试样,并以160/84A体型的年轻女性为试验对象,测试试验对象分别穿着9款运动内衣在运动前、运动中、运动后3种状态下的心率、血压以及主观感受。结果表明:运动内衣的面料、款式和人体运动状态是影响运动内衣穿着舒适性的重要因素;面料方面,采用莫代尔、氨纶面料的运动内衣舒适性最好;款式方面,粗带、工字形款式的运动内衣穿着舒适性最好。     

串联二调速阀两工进速度换接新回路及其在动力滑台双泵供油液压系统中的应用

在分析教材中典型现有基本回路的基础上,提出了一种二调速阀串联两工进速度换接新回路,本文对其来源、组成、原理、特点及其应用进行了阐述。新回路具有各调速阀可独自调节及能耗低等新特点（而现有回路则刚好相反）。     

供水管网中空气阀优选及水锤模拟

针对现阶段空气阀选型的随意性和盲目性,依据不同类型空气阀的工作原理及功能,给出了空气阀型式优选的方法。空气阀主要满足功能包括管道正常运行的微量排气量及其正常工作压力、水泵失电或爆管后由重力流产生负压的吸气量、管线初次充水的排气量、管线放空的吸气量、特殊情况下的防水锤要求。以吉县东城提黄灌溉二级站为例进行空气阀选型及水锤模拟,结果表明,采用蝶阀加空气阀联合防护,系统能安全运行。研究成果可为工程安全稳定运行及空气阀选型提供理论依据。     

Mechanism for cavitation phenomenon in mechanical heart valves

Recently, cavitation on the surface of mechanical heart valve has been studied as a cause of fractures occurring in implanted Mechanical Heart Valves (MHVs). It has been conceived that the MHVs mounted in an artificial heart close much faster than in vivo sue, resulting in cavitation bubbles formation. In this study, six different kinds of monoleaflet and bileaflet valves were mounted in the mitral position in an Electro-Hydraulic Total Artificial Heart (EHTAH), and we investigated the mechanisms for MHV cavitation. The valve closing velocity and a high speed video camera were employed to investigate the mechanism for MHV cavitation. The closing velocity of the bileaflet valves was slower than that of the monoleaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop areas is better able to prevent blood cell damage than the monoleaflet valves.     

Instability measurement of cavitation conditions in a spool valve through the definition of a cavitation instability index

Cavitation phenomenon is commonly known as a cause of deterioration of hydraulic components and a source of noise. In a proportional spool control valve for fluid power applications, the reduction of the cross section area at small openings can lead to the growth of gas bubbles inside the fluid phase. This phenomenon modifies the operating efficiency of the valve and can damage the material over time. The oil flow has been visualised through an experimental activity by using a 2-way 2-position spool valve with a plexiglass case and analysed by a CMOS type camera, with a high sampling rate. The recorded images focus the interaction between gas and liquid phases and highlights how the shape of cavitation bubbles is modified when the surface stress increases. In the present work, the interaction between liquid and gas phase has been studied by applying a non-linear method on the numerical matrices, derived from the acquired images. A cavitation instability index has been proposed, which is able to describe the cavitation behaviour and to define the instability of the equilibrium between the two phases. The trend of this index gives information about the two phase flow conditions, in order to reduce the cavitation phenomenon.     

超声联合sST2在鉴别不同类型心力衰竭的价值研究

目的探讨超声联合可溶性生长刺激表达基因2蛋白(sST2)在不同类型心衰中的应用价值方法以2018年7月—2019年10月本院收治的117例疑似心衰患者为研究对象,患者入院后分别在心脏部位进行超声心动图检查,抽取肘静脉血并采用酶联免疫吸附法测定患者血浆sST2水平。依据临床病史、体格检查及心电图、超声心动图等综合检查结果确诊为心衰的患者为病例组,非心衰患者为对照组,比较单独应用超声、血浆sST2诊断心衰效能;按照左心室射血分数(LVEF)及利钠肽、临床症状等将心衰患者分为降低型心衰组(HF-rEF组)、射血分数保留型心衰组(HF-pEF组)及射血分数中间值型心衰组(HF-mrEF组),比较不同组患者的超声特点及sST2水平,计算二者单独及联合鉴别不同类型心衰的效能。结果超声联合sST2诊断心衰时灵敏度为93.3%,特异度为67.2%,曲线下面积(AUC)为0.967;HF-rEF组的LAVI显著高于HF-pEF组、HF-mrEF组,IVSd值显著低于HF-pEF组、HF-mrEF组(P均<0.05);HF-rEF组的sST2为(95.64±35.23)ng/mL,显著高于HF-pEF组、HF-mrEF组的(54.27±26.85)ng/mL、(83.64±33.41)ng/mL,HF-mrEF组则显著高于HF-pEF组(P均<0.05),三组的LVPWd比较无统计学意义(P>0.05);联合诊断HE-rEF时,其灵敏度为73.7%,特异度为84.9%,曲线下面积(AUC)为0.867;联合鉴别HE-pEF时,其灵敏度为79.6%,特异度为89.5%,曲线下面积(AUC)为0.917。结论超声联合sST2较单一检查不同类型的心衰优势明显,可提高诊断效能,有助于临床进行疾病鉴别。     

Mining Wi-Fi Channel State Information for breathing and heart rate classification

Current vital signs monitoring systems require that the subject wears sensing devices. An alternative approach is using device-free technologies such as the Channel State Information (CSI) of a Wi-Fi signal. However, recent works using CSI for vital signs monitoring rely on complex signal processing techniques to improve its reliability. Considering that breathing and heart rate provide relevant information about the current health status of a subject, in this paper we develop an experimental system that combines signal processing techniques, such as filters and time and frequency domain analysis, with Data Mining techniques for breathing and heart rate monitoring. We also provide a thorough analysis for understanding CSI data as a technology for vital signs monitoring. Using K-Nearest Neighbors, Support Vector Machines, and Quadratic Discriminant Classifier models, our system achieves an accuracy of 99.18% for breathing rate classification while identifying heart rate monitoring challenges that are also stated in this paper.     

Monitoring and Mitigation of Methane Emissions from Pressure Relief Valves of a Biogas Plant

The two-year monitoring (732 days) of operational methane emissions from pressure relief valves of the gasholders from an agriculture biogas plant is presented. The monitoring aimed at the identification of major factors influencing the emissions and the effect of mitigation measures deduced from the results. The determined emission factors from the valves of both gastight covered digesters are 1.8 and 0.6 % CH₄ loss for the first and second year of investigation, respectively. The emission rates strongly depend on seasonal factors like (fast) changes in ambient air temperature as well as the capacity utilization of the combined heat and power and the operation of the gasholders. The implemented mitigation measures significantly reduced the measured methane emissions in the second year of the investigation.