多面棱体角分度误差分离技术--多次转位法

介绍了多面棱体角分度误差分离技术－－多次转位法。采用该技术可以分离多面棱体角分度误差和测量仪器的系统误差，满足多面棱体角分度误差的测量要求。     

基于准确转角的齿轮间歇机构设计

齿轮间歇机构中,主动轮转过一周时,要求从动轮准确转过一定角度。直接采用渐开线直齿圆柱齿轮的设计方法无法满足要求,必须对渐开线直齿圆柱齿轮进行修正。文章通过具体设计例子,阐述了具有准确转角的齿轮间歇机构设计方法．     

自动换刀装置中弧面分度凸轮啮合运动的力学分析

自动换刀装置中弧面分度凸轮和转动盘的滚子在啮合运动中传递较大的载荷,其大小和方向在不断发生变化,以啮合运动时转动盘的滚子为研究对象建立其受力分析的数学模型。用啮合原理及微分几何知识对数学模型中各个参数进行求解,并用VC++软件为工具对实际算例进行编程求解。得出凸轮转角与滚子所受法向载荷的变化规律曲线图,并生成载荷大小的数据文件,通过对变化规律曲线图进行分析,找出影响滚子所受法向力大小的主要因素,为设计弧面分度凸轮时转动盘滚子的选型提供理论依据。     

某型高速加工用ISO20刀柄焊缝疲劳性能试验研究

刀柄是高速工具系统的核心部件,其性能的优劣直接影响到刀具系统的可靠性.刀体与变幅杆之间的焊缝是刀柄的薄弱环节,容易发生疲劳失效.为了研究某型高速加工用ISO20刀柄焊缝的疲劳性能,通过常规试验方法对ISO20刀柄焊接试样进行了拉压疲劳试验.结果表明:随着最大加载载荷的降低,ISO20刀柄焊接处的疲劳寿命明显增长;当最大...     

Incidence and Enumeration of Vibrio parahaemolyticus in Shellfish from Two Retail Sources and the Genetic Diversity of Isolates as Determined by RAPD-PCR Analysis

A total of 83 shellfish samples from two local retail sources (A and B) yielded 38 samples positive for the presence of Vibrio parahaemolyticus based on 3 tube MPN enrichments and isolation from thiosulfate-citrate-bile salts-sucrose agar (TCBS) and biochemical tests. The 38 positive samples yielded 133 biochemically presumptive isolates of V. parahaemolyticus. Among these 133 presumptive isolates, 104 were confirmed by the polymerase chain reaction (PCR), which yielded more reliable identification results than the biochemical tests. The 38 biochemically presumptive samples yielded 29 samples that were confirmed by PCR to be positive for the presence of V. parahaemolyticus. RAPD analysis with three random primers was performed to examine the genetic diversity of 64 strains among the PCR confirmed V. parahaemolyticus isolates from both retail sources. 52 of 56 composite RAPD types consisted of single strains, indicating that most of the V. parahaemolyticus isolates were genetically quite heterogeneous. No strains representing the same RAPD type occurred in both retail outlets, implying that contamination of the shellfish by V. parahaemolyticus from the 2 retail sources was from different environmental locals and shellfish harvesting areas. Eight genomic clusters were generated at the 25% similarity level in a dendrogram based on RAPD profiles. With few exception, isolates with close genetic relationships grouping into an individual cluster tended to be derived from the same retail source.     

Sensory shelf life determination of a processed meat product ‘rullepølse’ and microbial metabolites as potential indicators

Sensory profiling was performed for a Danish lightly fermented heat-processed cold cut pork product termed ‘rullepølse’. Product samples were stored under modified atmosphere (MAP, 30% CO₂/70% N₂) for 0, 28 and 34 days and with subsequent aerobic storage for 4 days (MAP–OPEN) at temperatures of 4 °C and 8 °C. Microbial growth and metabolism was also measured with a focus on lactic acid bacteria (LAB) and their organic acid metabolites including lactic acid, acetic acid and α-ketoisocaproic acid. These acids were examined for sensory shelf life indexing potential for the ‘rullepølse’. Storage temperature exerted distinct impacts on the sensory characterised shelf life of ‘rullepølse’ stored under MAP and MAP–OPEN conditions. The MAP stored ‘rullepølse’ with subsequent 4 days storage in air (MAP–OPEN) could be stored for at least 28 days at 4 °C without a decrease in the sensory quality when opened. Whilst MAP stored ‘rullepølse’ at 8 °C with subsequent open storage (MAP–OPEN), compared to the lower temperature displayed a reduced shelf life of less than 28 days if sensory quality of the ‘rullepølse’ was to be maintained. The stage of sensory deterioration was correlated with high bacterial counts exceeding 10⁶ CFU g⁻¹. With respect to indexing ability of the examined organic acids none were found to have clear potential for prediction of the sensory deterioration.     

Privacy-preserving indexing of documents on the network

With the ubiquitous collection of data and creation of large distributed repositories, enabling search over this data while respecting access control is critical. A related problem is that of ensuring privacy of the content owners while still maintaining an efficient index of distributed content. We address the problem of providing privacy-preserving search over distributed access-controlled content. Indexed documents can be easily reconstructed from conventional (inverted) indexes used in search. Currently, the need to avoid breaches of access-control through the index requires the index hosting site to be fully secured and trusted by all participating content providers. This level of trust is impractical in the increasingly common case where multiple competing organizations or individuals wish to selectively share content. We propose a solution that eliminates the need of such a trusted authority. The solution builds a centralized privacy-preserving index in conjunction with a distributed access-control enforcing search protocol. Two alternative methods to build the centralized index are proposed, allowing trade offs of efficiency and security. The new index provides strong and quantifiable privacy guarantees that hold even if the entire index is made public. Experiments on a real-life dataset validate performance of the scheme. The appeal of our solution is twofold: (a) content providers maintain complete control in defining access groups and ensuring its compliance, and (b) system implementors retain tunable knobs to balance privacy and efficiency concerns for their particular domains. Dr. Vaidya’s work was supported by the National Science Foundation under grant CNS-0746943 and by a research resources grant from Rutgers Business School, Newark and New Brunswick.     

某锡铜共生硫化矿选矿试验研究

某锡铜共生硫化矿是以黄铜矿和锡石为主要有价矿物的多金属硫化矿石,同时含有大量的硅酸盐、碳酸盐及钙、铁脉石矿物。根据矿石性质特点,进行了多种选矿工艺流程和药剂制度试验,确定了最佳选矿工艺及参数,对锡铜等有价金属进行了充分回收。矿石含铜1.05%、锡0.34%、硫7.19%,采用强选择性硫化铜捕收剂和锡石组合捕收剂,经过铜硫混浮—铜硫分离—粗粒锡石重选、细粒锡石浮选—摇床精选的联合工艺流程选别,获得了铜精矿中铜品位25.05%、回收率91.78%;锡精矿中锡品位42.20%、回收率64.32%较好的选别指标。     

多自由度刨煤机动力学模型的建立与仿真

在单自由度刨煤机动力学模型的基础上,根据刨煤机的实际运行工况,建立了刨煤机多自由度非线性动力学模型,其中考虑了随机的煤壁作用力、刨链预紧力、链轮多边形效应因素的影响。并采用MATLAB/Simulink进行数值求解和仿真,得到了在各因素影响下刨头速度和刨链张力的变化状态。结果表明随机煤壁作用力和刨链预紧力对刨头速度和刨链张力变化的影响较大,链轮多边形效应影响较小,并且随机的煤壁作用力弱化了链轮多边形效应的影响。对多自由度和单自由度刨煤机动力学模型进行了比较分析,得出各种因素的影响规律是一致的,多自由度动力学模型更符合实际工况。为分析刨煤机动力学问题以及提高刨链可靠性提供理论基础。