火花塞间隙对发动机点火波形影响的研究

发动机点火系统工作性能的好坏,直接影响到汽车的动力性、经济性、安全性、噪声和废气排放。本文从点火波形分析入手,研究发动机火花塞间隙变化对点火波形的影响,通过定性定量分析,找出点火次级波形各参数的变化规律,为点火系统故障诊断提供理论依据。     

设计

设计无界环保无限smart与Colette共同打造精品系列自2009年4月smart fortwo在中国上市以来,越来越多的都市潮人爱上了这款设计独特极具个性的灵活小车,而标配mhd微型混合驱动的smart也以低油耗、低排放的绿色理念唤起驾车一族的环保意识。从2009年6月中旬起,smart与法国时尚概念店Colette携手合作,打造了一组以"设     

时尚激情一见倾心全新Lexus雷克萨斯IS300高级运动型轿车

秉承Lexus雷克萨斯豪华不凡、优雅舒适的传统,注入时尚激情的运动元素所打造的全新Lexus雷克萨斯IS300高级运动型轿车就是Lexus雷克萨斯为进入中国市场而专为中国客户度身订制的,无论从车身外形、内饰到内部装备都渗透着运动的激情元素,务求令IS系列成为“能令你一见倾心的车。”     

Application of dual reciprocity boundary element method to predict acoustic attenuation characteristics of marine engine exhaust silencers

In marine engine exhaust silencing systems, the presence of exhaust gas flow influences the sound propagation inside the systems and the acoustic attenuation performance of silencers. In order to investigate the effects of three-dimensional gas flow and acoustic damping on the acoustic attenuation characteristics of marine engine exhaust silencers, a dual reciprocity boundary element method （DRBEM） was developed. The acoustic governing equation in three-dimensional potential flow was derived first, and then the DRBEM numerical procedure is given. Compared to the conventional boundary element method （CBEM）, the DRBEM considers the second order terms of flow Mach number in the acoustic governing equation, so it is suitable for the cases with higher Mach number subsonic flow. For complex exhaust silencers, it is difficult to apply the single-domain boundary element method, so a substructure approach based on the dual reciprocity boundary element method is presented. The experiments for measuring transmission loss of silencers are conducted, and the experimental setup and measurements are explained. The transmission loss of a single expansion chamber silencer with extended inlet and outlet were predicted by DRBEM and compared with the measurements. The good agreements between predictions and measurements are observed, which demonstrated that the derived acoustic governing equation and the DRBEM numerical procedure in the present study are correct.     

Numerical Simulation of Projection Welding Processes for Door Hinge of Automobile Based on Coupled Fields Analysis

Projection welding is a variation of electric resistance welding with the dynamic changes of the flow paths for heat and electrical properties with changing temperature caused by the large plastic deformation collapse of projection. As the joint type between the auto door hinge and the inner plate, projection welding may bring welding distortions and would affect the assembly quality of auto body. A comprehensive electric-thermal-mechanical numerical simulation was performed to quantitatively simulate the processes of projection welding by using a coupled finite element method. The mechanism of projection collapse and the formation process of nugget were discussed and good conclusions have been achieved comparing with the test results.     

慢性肾脏病患者血清硒元素水平及其与临床指标的相关性

目的探究血浆硒含量在我国慢性肾脏病(CKD)患者各个阶段的严重程度及与临床指标相关性。方法检测107名研究对象(包括23名健康对照、10名CKD3期、11名CKD4期、45名CKD5期、6名腹膜透析及12名血液透析患者)的基本临床指标和硒、铁、铜、钙、钾、磷6项元素的血浆含量。结果随着患者肾功能不全的进展,患者血浆中的硒元素不断下降,尤其在终末期接受血液净化治疗的患者中,以腹膜透析患者血浆中硒含量最低;CKD患者血浆硒含量与血白蛋白、血总胆固醇、血三酰甘油呈正相关,与甲状旁腺素、血尿素氮及血肌酐水平呈负相关;CKD不同分期患者的血浆硒含量与钙元素呈正相关。结论 CKD患者普遍存在低血硒,且与病情严重程度及临床指标相关,应深入研究,以期为低硒地区人群精确补硒及CKD发病率的防治提供坚实的理论依据。     

舰船复杂网络大数据安全隐私保护系统

基于RSA算法的大数据安全隐私保护系统性能差,为了解决这一问题,提出复杂网络大数据安全隐私保护系统设计。系统硬件选择西门子PLC S7-300 U型总线、双端口存储器、CPU、ARM微处理器实现大数据安全隐私保护。系统软件采用全同态加密算法,获取大数据中任意元素地完整信息。软、硬件结合,完成基于复杂网络大数据安全隐私保护系统的设计。最后,进入实验部分,分别测试基于RSA算法的大数据安全隐私保护系统与复杂网络大数据安全隐私保护系统在不同测试时长下,测试用例是否能够全部通过。测试结果显示,本文系统测试结果皆显示成功,说明该系统性能更优。     

不锈钢中多元素光电光谱测定研究

制定仪器测量条件,以合金的主体元素为内标作工作曲线,用PDA-7000光电直读光谱仪测定C、Si、Mn、P、S、Cu、Ni、Cr、Mo、Al、Ti等元素,分析结果与标准值相吻合,其相对标准偏差(RSD)均小于5%,满足了日常分析要求。     

山区建筑边坡稳定性分析

门头沟采空棚户区改造石泉砖厂地块边坡支护工程位于门头沟区龙泉镇东龙门村。石泉砖厂地块安置房工程属浅山地建设,北侧临近九龙山,整体地势为北高南低,南北高差可达60m,地块内起伏较大。工程建设开始后,根据工程的总体规划,工程有大量的挖方区和部分填方区,随着土方开挖与回填,将形成高低不等的边坡,因此,需要根据相关规范与要求,对边坡进行永久性支护设计,本文叙述的