Influence of radial and axial runouts on surface roughness in face milling with round insert cutting tools

In face milling processes, the surface quality of the machined part depends on many factors, including feed, cutting tool geometry and tool errors. In this work, a numerical model for predicting the surface profile and surface roughness as a function of these factors is presented, incorporating a random values generation algorithm that makes it possible to determine the variation in surface roughness from the values that can be adopted by tool errors. This work is focused on round insert cutting tools and the influence of tool errors such as radial and axial runouts. The results that correspond to a number of teeth equal to 4, insert diameter of 12 mm, depth of cut of 0.5 mm, cutting speed of 120 m/min and feed of 0.4–1.4 mm/rev are analysed. Milling experiments are made to verify the validity of the model and the discrepancies between the experimental and theoretical surface profiles are assumed to be a consequence of different factors such as the variation in undeformed chip thickness along the surface profile.     

存在装配误差时TI蜗杆传动接触分析

利用三维图形和数值分析相结合的方法,研究了存在装配误差时TI蜗杆传动齿面接触的求解问题.借助蜗杆蜗轮齿面接触的三维直观效果,采用数值逼近的方法确定了TI蜗杆传动齿面接触位置,在此基础上分析了装配误差对TI蜗杆传动啮合接触性能的影响.     

氧化还原反应式配平中可能差错的几种情况

本文通过许多实例，指出了氧化还原反应式配平中可能出现的得失电子数不等或电荷数未配平、得失电子关系不对及反应式中酸碱性介质有错误等几种差错，并归纳了在酸碱性水溶液中平衡介质的方法。     

A review of the use of human factors classification frameworks that identify causal factors for adverse events in the hospital setting

Various human factors classification frameworks have been used to identified causal factors for clinical adverse events. A systematic review was conducted to identify human factors classification frameworks that identified the causal factors (including human error) of adverse events in a hospital setting. Six electronic databases were searched, identifying 1997 articles and 38 of these met inclusion criteria. Most studies included causal contributing factors as well as error and error type, but the nature of coding varied considerably between studies. The ability of human factors classification frameworks to provide information on specific causal factors for an adverse event enables the focus of preventive attention on areas where improvements are most needed. This review highlighted some areas needing considerable improvement in order to meet this need, including better definition of terms, more emphasis on assessing reliability of coding and greater sophistication in analysis of results of the classification.

Practitioner Summary: Human factors classification frameworks can be used to identify causal factors of clinical adverse events. However, this review suggests that existing frameworks are diverse, limited in their identification of the context of human error and have poor reliability when used by different individuals.     

Virtual machining considering dimensional,geometrical and tool deflection errors in three-axis CNC milling machines

Virtual manufacturing systems can provide useful means for products to be manufactured without the need of physical testing on the shop floor. As a result, the time and cost of part production can be decreased. There are different error sources in machine tools such as tool deflection, geometrical deviations of moving axis and thermal distortions of machine tool structures. Some of these errors can be decreased by controlling the machining process and environmental parameters. However other errors like tool deflection and geometrical errors which have a big portion of the total error, need more attention. This paper presents a virtual machining system in order to enforce dimensional, geometrical and tool deflection errors in three-axis milling operations. The system receives 21 dimensional and geometrical errors of a machine tool and machining codes of a specific part as input. The output of the system is the modified codes which will produce actual machined part in the virtual environment.     

Oxidative stability of high-fatty acid rice bran oil at different stages of refining

The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude ≥ degummed > bleached = deodorized > alkali-refined oil.     

安全相关控制系统中的安全总线分析和研究

较全面地阐述目前安全相关控制系统中6种主流安全总线的结构和特点,分析信息传输可能发生的错误,研究各总线在信息级应对传输错误所采取的具体防范措施以及为提高通讯安全在结构上所采取的安全机制,从而为深入理解各安全总线不同的安全工作机制、分析和设计安全总线以及安全监控系统总线的选择提供了借鉴和指导.     

风力机的线性变参数主动容错控制

针对风力机具有非线性和参数的不确定性的特征,提出了基于线性变参数(linear parameter varying,LPV)增益调度的风力机主动容错控制方法,降低故障对机组动态特性的影响.基于LPV凸分解方法,将风力机的非线性模型转化为具有凸多面体结构LPV模型,利用线性矩阵不等式(linear matrix inequalities,LMIs)技术对凸多面体各个顶点分别设计满足性能要求的控制器,再利用各顶点设计的反馈控制器得到具有凸多面体结构LPV容错控制器.仿真结果表明,LPV增益调度技术可以成功地应用于风力机系统的容错控制.     

Implicit Bayesian Inference Using Option Prices

Abstract. A Bayesian approach to option pricing is presented in which posterior inference about the underlying returns process is conducted implicitly via observed option prices. A range of models allowing for conditional leptokurtosis, skewness and time‐varying volatility in returns are considered, with posterior parameter distributions and model probabilities backed out from the option prices. Models are ranked according to several criteria, including out‐of‐sample predictive and hedging performance. The methodology accommodates heteroscedasticity and autocorrelation in the option pricing errors, as well as regime shifts across contract groups. The method is applied to intraday option price data on the S&P500 stock index for 1995. While the results provide support for models that accommodate leptokurtosis and skewness, no one model dominates when all criteria are considered.     

超声波传感器深度增益补偿电路设计

为了补偿超声探伤信号在动车组转向架中的传播损耗,利用超声波传感器,根据深度增益补偿的基本原理和微弱信号在不同深度处的衰减规律,设计了基于现场可编程门阵列(FPGA)的数字可控制式的增益放大补偿方法和电路。由XC6SLX16型FPGA的PLL模块产生精确的时钟控制信号,并输出数字量到DA芯片产生补偿电压曲线控制AD8330的放大增益倍数,再使深度补偿增益后的回波模拟信号进入LTC2249芯片内转换成数字信号,以便为下级数字信号再处理使用。实验结果表明:在超声波探伤仪系统的电路输入端加入频率为5 MHz、峰峰值为2 mV的正弦波激励后,通过改变步进值为5 dB的3种不同增益的大小,可以实现不同的放大增益,使衰减得到补偿。