Effect of fiber volume fraction on longitudinal tensile properties of SiC<Subscript>f</Subscript>/Ti-6Al-4V composites

The longitudinal tensile properties of SiC_f/Ti-6Al-4V composites with different fiber volume fractions were simulated by the Monte Carlo 2-D finite element model. The random distribution of fiber strength was expressed by the two-parameter Weibull function. Meanwhile, contact elements and birth-death elements were used to describe the interfacial sliding process after debonding and fiber breakage (or matrix cracking) respectively, which was realized by subroutine complied in ANSYS-APDL (ANSYS Parametric Design Language). The experimental results show that the yield stress and ultimate tensile strength of SiC_f/Ti-6Al-4V composites increase with increasing fiber volume fraction, while the corresponding strain of them is just on the contrary. In addition, almost the same failure mode is obtained in SiC_f/Ti-6Al-4V composites with various fiber volume fractions when the interfacial shear strength is fixed. Finally, the tensile strength predicted by finite element analysis is compared with that predicted by Global load-sharing model, Local load-sharing model and conventional rule of mixtures, thus drawing the conclusion that Local load-sharing model is very perfect for the prediction of the ultimate tensile strength.     

基于GSM高速公路管理系统设计

本文所研究的高速公路管理系统是基于GSM模块的。本系统中的GSM模块是一款高性能模块,主控制芯片采用STC12C5A32S2系列单片机可以实现上位机控制GSM模块接、打电话及收发信息等功能。而且可以对收到的信息进行解析,并根据信息内容进行相关操作,从而实现远程控制。该系统可以将高速公路上的各个分站与主控制中心连接起来,便于控制中心对下辖的各管理所进行高速、有效、实时的管理。     

知识开源化背景下信息安全类课程教学改革初探

本文针对当前知识开源化的现状,结合信息安全类相关课程在北京电子科技学院授课的实际情况,以利用知识开源化所带来的优势,改善课程的教学效果、提高学生的动手实践能力为目的,研究和探讨了信息安全类部分课程的教学模式改革方式和所取得的效果。     

EFFECTS OF NUCLEATION AGENTS ON EFFICIENCY OF BORON EXTRACTION FROM MgO－B_2O_3－SiO_2 SLAGS

ＥＦＦＥＣＴＳＯＦＮＵＣＬＥＡＴＩＯＮＡＧＥＮＴＳＯＮＥＦＦＩＣＩＥＮＣＹＯＦＢＯＲＯＮＥＸＴＲＡＣＴＩＯＮＦＲＯＭＭｇＯ－Ｂ_２Ｏ_３－ＳｉＯ_２ＳＬＡＧＳ￥Ｚｈａｎｇ，Ｐｅｉｘｉｎ；Ｌｏｕ，Ｈａｉｌｉｎｇ；Ｓｕｉ，Ｚｈｉｔｏｎｇ（Ｄｅｐａｒｔｍｅｎ?..     

Oxidation behavior of TiAl coated with a fine-grain Co-30Cr-4Al film

The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale.     

Mn对Fe_3Al合金室温力学性能的影响

Ｍｎ对Ｆｅ_３Ａｌ合金室温力学性能的影响楼白杨，刘茂森，毛志远，涂江平，肖延龄，钟映宏（浙江大学）Ｆｅ３Ａｌ金属间化合物具有抗氧化耐腐蚀性良、比强度高和成本低等特点［１，２］，从而具有可观的工程应用前景。对这种材料目前国内研究的热点之一是改善其室温塑?..     

Suppression of carbon monoxide formation in oxide-coated TZM molybdenum X-ray rotating anodes

Higher performance designs for rotating anode X-ray tubes have increased the average rotating anode temperature from below 1100 °C to well above 1300 °C. This temperature increase has accelerated the formation of carbon monoxide by reaction of carbon from the alloy substrate with oxygen from the emissive coating. The dominant carbon source is thought to be Mo₂C grain boundary precipitates in the TZM molybdenum alloy substrate. The dominant oxygen source is thought to be TiO in the emissive coating. Placement of a monocarbide-forming reactive layer between the alloy substrate and the emissive coating has been demonstrated to lower the thermodynamic activity of the carbon source and dramatically reduce the rate of formation of carbon monoxide.     

钢铬钛共渗工艺的研究

对工业纯铁、45钢和3Cr2W8V钢的低真空铬钛共渗进行了研究,探讨了共渗层的组织结构、生长过程以及温度、时间等工艺因素的影响。     

Secure three-party computational protocols for triangle area

In this work, we have put forth two different protocols to address a concrete secure multi-party computational (MPC) problem related to a triangle, of which the coordinates of the three vertices are confidentially kept by the three participants, respectively. The three parties wish to collaboratively compute the area of this triangle while preserving their own coordinate privacy. As one of the merits, our protocols employ weaker assumptions of the existence of pseudorandom generators. In particular, unlike massive secure MPC protocols that rely a lot on oblivious transfer, ours utilize a new computing idea called “pseudorandom-then-rounding” method to avoid this burdensome obstacle. The two protocols are based on different theorems, while they both make use of the same underlying idea. At last, we provide a detailed proof for the first protocol by a series of security reductions of our newly defined games, which seems somewhat stronger than the previous simulation-based proofs and a proof sketch for the second one. Analysis and discussion about the reasons are provided as well to round off our work.     

模块主成分分析在人脸重建中的应用

模块主成分分析是人脸重建中一种重要的子空间学习方法,鲁棒性不足是传统的基于L2范数的模块主成分分析(BPCA-L2)的主要问题。为此,提出了一种新的基于L1范数的模块主成分分析(BPCA-L1)方法。该方法使用了对奇异值不太敏感的L1范数。基于L1范数的模块主成分分析方法简单并易于实现,在一些人脸数据集上的重建实验验证了其有效性。