温压法制备铜铅轴承合金的研究

通过温压工艺制备了铜铅轴承合金材料 ,研究了温压成形温度和压力等因素对压坯致密化和烧结体性能的影响。结果表明 ,温压成形时可用经典的压制方程来描述粉末体的压形规律。温压温度的选择对压坯及烧结体的性能都有明显的影响 ,在合适的工艺条件下 ,温压法较冷压烧结法可制得更高密度和性能的铜铅轴承合金材料。

温压法制备碱矿渣复合摩擦材料性能研究

以硅酸钠碱激发矿渣为黏结剂,粉碎处理的钢纤维为增强纤维,石墨作为减摩材料,采用温压法制备碱矿渣复合摩擦材料。使用AG-10万能材料试验机、定速摩擦试验机、X射线衍射(XRD)仪、扫描电镜(SEM)等对碱矿渣复合摩擦材料的力学性能与摩擦性能进行研究。结果表明,当钢纤维体积掺量为3%时,碱矿渣摩擦材料的力学性能提高效果最佳,抗压强度提升至119.25 MPa,抗折强度提升至35.75 MPa,抗压强度、抗折强度分别提升400%和95%;加入石墨有效降低了碱矿渣复合摩擦材料的摩擦因数及磨损率,使摩擦材料符合GB/T 5763-2008中FF级陶瓷前片要求。

基于温压法的LED结温测试方法研究

LED照明产品的发光效率和使用寿命与LED结温紧密相关,因此对LED结温的控制和检测是必不可少的。目前结温测试大部分使用管脚法,该方法准确率难以得到保证。基于此,文章采用温压法对LED结温进行测试,可以简化结温计算过程,提高测试的准确性。温压法通过改变环境温度测量两次以上的正向电压,计算压降差和温度差的比值,可以获得电压温度线性关系K曲线,利用K曲线可以计算出LED在正常工作条件下的结温。测试证明,文章所使用的结温测试方法在LED应用和LED照明中有着很好的应用前景。

温压-原位反应法制备C/C-SiC材料过程中裂纹的形成机制

以短切炭纤维、石墨粉、硅粉、树脂和粘结剂为原料，采用温压一原位反应法制备C／C-SiC制动材料，研究C／C-SiC制动材料裂纹的形成机制。研究结果表明：树脂炭化裂解产生大量的气体产物，一部分气体产物碰到裂纹壁时受阻凝聚成含C，P，O和H等元素或自由基团的液滴，炭化后液滴转变成直径为2-4μm的高含碳量碳球；另一部分气体产物沿着裂纹试图从试样中排出，当裂纹为封闭状态时便促使微裂纹向前扩展，直至材料开裂；在高温热处理过程中，硅粉熔化后与就近碳源反应生成连续的网络状SiC基体，它对裂纹的扩展有一定的抑制作用，并能愈合试样中的微裂纹。

温压-原位反应法制备C/C-SiC复合材料及其显微结构分析

采用温压-原位反应法制备炭纤维增强炭和碳化硅双基体(C/C-SiC)复合材料,利用X线衍射分析材料组成,并通过扫描电子和透射电子显微镜从不同尺度观察复合材料的微观结构。研究结果表明:硅炭原位反应生成的SiC是面心立方β-SiC,并以多种形态分布在C/C-SiC复合材料中,主要有小颗粒状、圆弧状、多面体形状和不规则形状等;树脂炭基体和SiC基体之间存在非晶界面相,SiC基体的晶面间距约为0.4 nm,并存在大量孪晶,呈现平行分层生长的形貌。

温压-原位反应法制备C/C-SiC材料的压缩性能及其破坏机理

以短炭纤维、炭粉、Si粉、树脂和粘结剂为原料,采用温压-原位反应法(WC-ISR)制备C/C-SiC制动材料,研究该材料的压缩性能及其破坏机理。结果表明:C/C-SiC制动材料的纵向压缩强度可达118.2 MPa,纵向压缩破坏表现为韧性断裂,以对角剪切破坏方式为主;横向压缩强度可达86.9 MPa,横向压缩破坏主要表现为脆性断裂,以多层复合剪切破坏方式为主。C/C-SiC制动材料的压缩性能分别随炭纤维和SiC含量的增加而增大,且炭纤维含量的影响更加显著;但随基体炭含量的增加而降低。

一种抗高过冷度水合物动力学抑制剂的合成与评价

天然气在高压低温并具有游离水的环境条件下极有可能在井下和地面管道中生成天然气水合物,造成井筒的堵塞以及其他安全问题。注入动力学抑制剂是目前最环保高效的方法,但在高过冷度的环境下,抑制性能微弱,因此有必要研制具有抗高过冷度的新型动力学抑制剂。制备了含多重氢键的功能单体UpMA,将N-乙烯基吡咯烷酮(NVP)作为主单体,含多重氢键结构的UpMA单体作为功能单体,二者共聚制备出新型动力学水合物抑制剂PVP-UpMA,采用温压扭矩法综合评价水合物抑制剂的抑制成核性能以及抑制生长性能,并通过考察耐用过冷度、诱导时间以及气体消耗量等参数评价该抑制剂在水合物生成过程中的抑制性能。结果表明,PVP-UpMA的耐用过冷度随着质量分数的增大而小幅度增大,且1%PVP-UpMA的耐用过冷度(6.45℃)明显优于商业PVPk90(4.11℃)以及Luvicap EG(3.36℃);1%PVP-UpMA抑制性能随着过冷度的增加而降低,但在高过冷度(7.5℃)下诱导时间仍超过200 min,气体消耗量同纯水相比降低75%以上;PVP-UpMA在7.5℃过冷度下最佳质量分数应低于1.5%。虽然PVP-UpMA环境效益一般,但经济效益较好,有望替代现场传统热力学抑制剂。

天然气水合物探测技术的模拟实验研究

天然气水合物模拟实验研究的关键就是探测技术的有效性。总结叙述了超声、电阻法以及温压法在天然气水合物模拟实验中的应用效果及存在问题。对今后天然气水合物模拟实验研究工作提出了几点建议。

短炭纤维增强C和SiC双基体材料的力学性能及破坏机理

以短炭纤维为增强纤维,以炭粉、Si粉和树脂为基体来源,采用温压—原位反应法制备C/C-SiC材料,研究该材料的力学性能及破坏机理。结果表明:C/C-SiC制动材料的纵向和横向抗弯强度分别为76 MPa和62 MPa,以韧性断裂为主,弯曲破坏表现为裂纹偏转、纤维桥接、纤维拔出和界面脱粘。纵向抗压强度达112 MPa,纵向压缩破坏表现为韧性断裂,以对角剪切破坏方式为主;横向抗压强度达84 MPa,横向压缩破坏主要表现为脆性断裂,以多层复合剪切破坏方式为主。材料的冲击韧性为3.1 kJ/m2。

关于空气密度的快速测定

本文主要叙述了利用两个物体的表观质量差 ,对空气密度进行快速测定 ,简称“二体表观质量差”法 ,并用“温、湿、压”法于同时同地所测定的结果对其可信度加以评述。

Deformation simulation of low-temperature high-speed extrusion for 6063 Al alloy

The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

Parameters affect foaming and foam stability during foam drilling

The authors presented indoor practice experiments of parameters affect on foaming and foam stability. Experiments were carried out and special equipments were used to determine foaming and foam stability; tests were tabulated and charted. The effects of chemical and physical parameters on foaming and foam stability have been conducted.

A non-invasive method for gastrointestinal parameter monitoring

AIM: To propose a new, non-invasive method for monitoring 24-h pressure, temperature and pH value in gastrointestinal tract.METHODS: The authors developed a miniature, multifunctional gastrointestinal monitoring system, which comprises a set of indigestible biotelemetry capsules and a data recorder.The capsule, after ingested by patients, could measure pressure, temperature and pH value in the gastrointestinal tract and transmit the data to the data recorder outside the body through a 434 MHz radio frequency data link. After the capsule passed out from the body, the data saved in the recorder were downloaded to a workstation via a special software for further analysis and comparison.RESULTS: Clinical experiments showed that the biotelemetry capsules could be swallowed by volunteers without any difficulties. The data recorder could receive the radio frequency signals transmitted by the biotelemetry in the body. The biotelemetry capsule could pass out from the body without difficulties. No discomfort was reported by any volunteer during the experiment. In vivo pressure and temperature data were acquired.CONCLUSION: A non-invasive method for monitoring 24-h gastrointestinal parameters was proposed and tested by the authors. The feasibility and functionality of this method are verified by laboratory tests and clinical experiments.

THERMOLYTIC EFFECT OF MOXIBUSTION AND ITS RELATION TO ACUPOINT RECEPTORS

In the present paper, the effect of moxibustion stimulation (by using a computer automaticallycontrolled condensed light) of Dazhui (GV 14) etc. on auricular temperature changes was observed in the rabbit after intravenous injection of endotoxin. Changes of rabbit’s auricular temperature were sampled and recorded by using a thermistorthermometer (connected with a computer) before and after moxibustion stimulation. Results indicated that moxibustion making the skin temperature reach to 48℃ could inhibit the endotoxininduced lowering reaction of auricular temperature, while moxibustion making the skin temperature of 40℃ had no this effect. It revealed that higherskintemperature moxibustion had a thermolytic effect on bodyfever, which had a close relation mainly with polymodal receptors rather than with temperature receptor. It also demonstrated that endotoxininduced changes of auricular temperature could be used as an index for evaluating the thermolytic effect of moxibustion.

Numerical Simulation and Experimental Verification of Temperature Distribution of Piezoelectric Stack with Heating and Thermal Insulation Device

This paper discusses the temperature field distribution of piezoelectric stack with heating and thermal insulation device in cryogenic temperature environment. Firstly,the model of the piezoelectric damper is simplified and established by using partial-differential heat conduction equation. Secondly,the two-dimensional Du Fort-Frankel finite difference scheme is used to discretize the thermal conduction equation,and the numerical solution of the transient temperature field of piezoelectric stack driven by heating film at different positions is obtained by programming iteration. Then,the cryogenic temperature cabinet is used to simulate the low temperature environment to verify the numerical analysis results of the temperature field. Finally,the finite difference results are compared with the finite results and the experimental data in steady state and transient state,respectively. Comparison shows that the results of the finite difference method are basically consistent with the finite element and the experimental results,but the calculation time is shorter. The temperature field distribution results obtained by the finite difference method can verify the thermal insulation performance of the heating system and provide data basis for the temperature control of piezoelectric stack.

A Climatology of the Southwest Vortex during 1979–2008

Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the SWV are derived from the dataset. In comparison to other seasons, summer yields the least SWVs, but with the highest probability that they will migrate from their region of origin. SWVs mostly emerge in the southwest of the Sichuan Basin and the southeast of the Tibetan Plateau. Migratory SWVs mainly move along either an eastward or southeastward path. Detailed composite analysis of warm-season SWVs shows that the subtropical high is a key factor in determining the direction of migratory SWVs. Furthermore, the steering wind at 700 hPa dominates the moving direction of migratory SWVs. Potential stability diagnosed by pseudo-equivalent potential temperature ? se is of certain significance for the evolution and movement of SWVs. On the other hand, migratory SWVs possess relatively greater strength than stationary SWVs, due to a stronger low-level jet with enhanced baroclinicity and moisture transport providing more energy to support the growth of SWVs along their paths of movement.

Global lateral buckling analysis of idealized subsea pipelines

In order to avoid the curing effects of paraffin on the transport process and reduce the transport difficulty,usually high temperature and high pressure are used in the transportation of oil and gas.The differences of temperature and pressure cause additional stress along the pipeline,due to the constraint of the foundation soil,the additional stress can not release freely,when the additional stress is large enough to motivate the submarine pipelines buckle.In this work,the energy method is introduced to deduce the analytical solution which is suitable for the global buckling modes of idealized subsea pipeline and analyze the relationship between the critical buckling temperature,buckling length and amplitude under different high-order global lateral buckling modes.To obtain a consistent formulation of the problem,the principles of virtual displacements and the variation calculus for variable matching points are applied.The finite element method based on elasto-plastic theory is used to simulate the lateral global buckling of the pipelines under high temperature and pressure.The factors influencing the lateral buckling of pipelines are further studied.Based upon some actual engineering projects,the finite element results are compared with the analytical ones,and then the influence of thermal stress,the section rigidity of pipeline,the soil properties and the trigging force to the high order lateral buckling are discussed.The method of applying the small trigging force on pipeline is reliable in global buckling numerical analysis.In practice,increasing the section rigidity of a pipeline is an effective measure to improve the ability to resist the global buckling.

Leaching of copper from chalcopyrite concentrate by using ammonium persulphate in an autoclave:Determination of most suitable impeller type by using response surface methodology

Some effective parameters on the copper extraction from Kiire chalcopyrite concentrate were optimized by using response surface methodology （RSM）. Experiments designed by RSM were carried out in the presence of ammonium persulfate （APS） and different types of impeller in an autoclave system. Ammonium persulfate concentration and leaching temperature were defined numerically and three types of impellers were defined categorically as independent variables using experimental design software. The optimum condition for copper extraction from the chalcopyrite concentrate is found to be ammonium persulfate concentration of 277.77 kg/m3, leaching temperature of 389.98 K and wheel type of impeller. The proposed model equation using RSM has shown good agreement with the experimental data, with correlation coefficients R2 and RaZaj for the model as 0.89 and 0.84, respectively.

Non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution

Carbonation decomposition of hydrogarnet is a significant reaction of the calcification-carbonation new method for alumina production by using low-grade bauxite.In this work,non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution was studied by high-pressure differential scanning calorimetry(HPDSC) at different heating rates of 2,5,8,10,15 and 20 K·min^(-1),respectively.The activation energy(E_α) was calculated with the help of isoconversional method(model-free),and the reaction mechanism was determined by the differential equation method.The calculated activation energy of this reaction was 115.66 kJ·mol^(-1).Furthermore,the mechanism for decomposition reaction is Avrami-Erofeev(n=1.5),and the decomposition process is diffusion-controlled.

Determination of fermentable sugar in wort made from degermed corn extruded at low temperature as beer adjunct by HPLC

[Objective] To accurately determine the components and content of fermentable sugars in wort. [Method] The components and content of fermentable sugars in wort made from degermed corn extruded at low temperature as beer adjunct were determined by HPLC. [Result] The contents of sugar components were shown as below: fructose was 3.8 g/L, glucose was 7.4 g/L, sucrose was 4.2 g/L, maltose was 53.8 g/L and maltotriose was 10.6 g/L.The content of the five fermentable sugars had good linear relation within their peak area in the determination range, the correlation coefficient was 0.977 6-0.990 7, the recoveries of samples were >96%, the standard deviation was 1.27%-3.26%. [Conclusion] The method is simple and rapid with high sensitivity and good reproducibility, it provides reliable and accurate analytic method for determining the components of fermentable sugars in wort made from degermed corn extruded at low temperature as beer adjunct.