热处理TiAl(W,Si)合金的拉伸性能及裂纹扩展

对铸态Ti-46Al-0.5W-0.5Si合金进行淬火回火热处理,获得了近层片组织和双态组织。对两种不同组织的合金进行室温拉伸试验,并对试样断口和断口附近的组织进行分析,研究了拉伸断裂机制。结果表明:双态组织比近层片组织具有更好的室温塑性和抗拉强度。双态组织中的裂纹可以绕过较小的γ相颗粒,沿γ相和α2/γ片层团的界面扩展,也会以穿越层片的方式扩展。而近层片组织中的裂纹则是以沿片层和穿越片层的混合方式扩展。     

3-氯-2,6-二硝基喹喔啉的合成工艺研究

喹喔啉为一类重要的苯并吡嗪类杂环化合物,喹喔啉衍生物在医药及化工合成领域具有重要的作用。3-氯-2,6-二硝基喹喔啉是一种重要医药化工中间体。本文以2-羟基喹喔啉为原料,经硝化反应和氯代反应两步反应得到目标化合物。该合成方法操作简便、后处理操作简便,花费时间少且产物纯度高、收率也较高,产品收率为58.2%,适合工业化生产。     

Highly Flexible Graphene Oxide Nanosuspension Liquid‐Based Microfluidic Tactile Sensor

A novel graphene oxide (GO) nanosuspension liquid‐based microfluidic tactile sensor is developed. It comprises a UV ozone‐bonded Ecoflex–polydimethylsiloxane microfluidic assembly filled with GO nanosuspension, which serves as the working fluid of the tactile sensor. This device is highly flexible and able to withstand numerous modes of deformation as well as distinguish various user‐applied mechanical forces it is subjected to, including pressing, stretching, and bending. This tactile sensor is also highly deformable and wearable, and capable of recognizing and differentiating distinct hand muscle‐induced motions, such as finger flexing and fist clenching. Moreover, subtle differences in the handgrip strength derived from the first clenching gesture can be identified based on the electrical response of our device. This work highlights the potential application of the GO nanosuspension liquid‐based flexible microfluidic tactile sensing platform as a wearable diagnostic and prognostic device for real‐time health monitoring. Also importantly, this work can further facilitate the exploration and potential realization of a functional liquid‐state device technology with superior mechanical flexibility and conformability.     

Groundwater Exploitation and Its Impact on the Environment in the North China Plain

Abstract

The North China Plain (NCP) is one of China's most important social, economic, and agricultural regions. Currently, the Plain has 17,950 thousand ha of cultivated land, 71.1 percent of which is irrigated, consuming more than 70 percent of the total water supply. Increasing water demands associated with rapid urban and industrial development and expansion of irrigated land have led to overexploitation of both surface and the ratio of groundwater resources, particularly north of the Yellow River. In 1993, the ratio of groundwater exploitation to recharge in many parts of the NCP exceeded 1.0; in some areas, the ratio exceeded 1.5. Consequently, about 1.06 million ha of water-short irrigated areas in the NCP also have poor water quality. Persistent groundwater overexploitation in the northern parts of the NCP has resulted in water-level declines in both shallow and deep aquifers. According to data from 600 shallow groundwater observation wells in the Hebei Plain, the average depth to water increased from 7.23 m in 1983 to 11.52 m in 1993, indicating an average water-table decline of 0.425 m/year. Water table declines are not uniformly distributed throughout the area. Depletion rates are generally greatest beneath cities and intensively groundwater-irrigated areas. Water-table declines have also varied over time. With the continued decline of groundwater levels, large depression cones have formed both in unconfined and confined aquifers beneath the Hebei Plain. Groundwater depletion in the NCP has severely impacted the environment. Large tracts of land that overlie cones of depression have subsided, seawater has intruded into previously freshwater aquifers in coastal plains, and ground-water quality has deteriorated due to salinization, seawater intrusion, and untreated urban and industrial wastewater discharge. In order to balance groundwater exploitation with recharge, the major remedial measures suggested are to strengthen groundwater management, to raise water use efficiency, to adjust the water-consumed structure, and to increase water supply     

AlxCrFeNiCuVTi系高熵合金的组织和力学性能研究

采用真空电弧熔炼制备AlxCrFeNiCuVTi(摩尔比x=0,0.5,1,1.5)高熵合金.利用XRD、SEM和万能材料试验机等方法对该合金进行研究.结果表明:铸态合金由枝晶相,菊花状共晶组织以及枝晶间富Cu相共同组成;随着Al元素的增加,合金的组织结构逐渐由多种bcc相和fcc相共存逐渐变为单一的bcc相,合金硬度和抗压缩性能整体呈上升趋势;Al1CrFeNiCuVTi合金的最高抗压缩强度达到1810.4 MPa,压缩率为23％.     

A portable toolkit for supporting end-user personalization and control in context-aware applications

A context-aware application in the pervasive computing environment provides intuitive user centric services using implicit context cues. Personalization and control are important issues for this class of application as they enable end-users to understand and configure the behavior of an application. However most development efforts for building context-aware applications focus on the sensor fusion and machine learning algorithms to generate and distribute context cues that drive the application with little emphasis on user-centric issues. We argue that, to elevate user experiences with context-aware applications, it is very important to address these personalization and control issues at the system interface level in parallel to context centric design. Towards this direction, we present Persona, a toolkit that provides support for extending context-aware applications with end-user personalization and control features. Specifically, Persona exposes a few application programming interfaces that abstract end-user customization and control mechanisms and enables developers to integrate these user-centric aspects with rest of the application seamlessly. There are two primary advantages of Persona. First, it can be used with various existing middlewares as a ready-to-use plug-in to build customizable and controllable context-aware applications. Second, existing context-aware applications can easily be augmented to provide end-user personalization and control support. In this paper, we discuss the design and implementation of Persona and demonstrate its usefulness through the development and augmentation of a range of common context-aware applications.     

液态置氢对TC21合金组织及硬度的影响

在热氢处理(THP)的基础上提出了液态置氢的方法,即合金在含氢气的气氛下进行熔炼,部分氢被合金吸收,并在凝固后保留在合金的内部。由于氢在液态合金中的扩散系数较大,因此液态置氢的速度较快。本研究基于Sievert’t定律推导出了液态置氢时,TC21合金中的氢含量与环境中的氢分压的关系。发现氢细化了TC21合金的晶粒,并且细化作用随着氢含量的增加而增强,随着氢含量的进一步增加,TC21合金中出现了α"相和孪晶结构。合金的显微硬度随氢含量的增加而降低。     

The critical pressure and impeding pressure of Al evaporation during induction skull melting processing of TiAl

In this article, two key pressures, the critical pressure P _crit and the impeding pressure P _impe of elemental evaporation, are defined and studied based on the calculation relationship between the evaporation loss rate N _m and the chamber pressure P during melting of titanium-aluminum alloys. When the chamber pressure is below P _crit or above P _impe, N _m tends to the maximum or the minimum value and remains almost unchanged. However, if P _crit<P<P _impe, with the increase of the chamber pressure, N _m declines sharply. A method has been put forward to calculate P _crit and P _impe of Al evaporation in a Ti-XAl (at pct) (X=25 to 50) melt. The calculation result shows that P _crit or P _impe is a second-order function of the molar percentage of Al and the melt temperature.     

Development of modified stokes expression to model the behavior of expanded beds containing polydisperse resins for protein adsorption

Expanded bed behavior was modeled by using the Richardson-Zaki correlation between the superficial velocity of the feed stream and the void fraction of the bed. A polydisperse material, Chelating excellose® (70-210 Μm in diameter, 1.21 g/cm³ in density), which has Ni²⁺ ions for the selective binding of histidine-tagged proteins, was used as the resin. A method to modify the Stokes expression to express the terminal settling velocity of the resins by introducing two empirical parameters, the effective diameter of the resins and an exponent for(ρ _p -ρ)/Μ term, was developed. Combined use of the Richardson-Zaki correlation and the modified Stokes expression was successful in modeling the bed expansion by incorporating physical properties of feed streams and the resins.     

液态金属双频电磁约束成形过程研究

利用高频－超音频和双高频的电磁场实现了液态金属双频电磁约束成形的工艺过程,达到了固态试样无接触加热熔化、初步约束成形和复杂形状熔体无模壳电磁成形的目的。在双频电磁成形过程中发现,高频－超音频双频电磁成形控制不仅优于单频电磁成形,而且比双高频电磁成形控制容易,2种频率的电磁场不同加热熔化和电磁成形功能都能加以发挥,并可单独加以调节。在试验中利用高频－超音频双频电磁成形工艺过程成功儿得了扁椭圆截面和弯截面复杂形状的双频无模电磁成形样件。