南非黄金矿山设计中的某些财政问题

尽管南非的黄金开采工业历史悠久，但当今南非的采金业却面临着严重的挑战，威胁到它的持续存在。尤其影响到采金业卓有成效的商业活动的３个因素是：黄金价格、现行的矿业税收准则和政策和生产成本。为了试图指明为达到持续赢利的经营途径，要明确确认各种问题和提出解决这些问题的方法。这些方法包括利用较少的竖井提升系统和较长的平巷运输系统、更多地利用循环致冷的通负气流、将制冷设备更有效的定位、使用拖挂矿车辆数更多的矿     

不锈钢汽车

在2004年年底,主要的不锈钢生产企业和汽车原始设备制造商共同发起了一个“下一代汽车”项目,旨在确定在汽车生产中使用不锈钢的潜力。作为该研究的一部分,为新的用途开发试验了新的材料,取得了突破性的进展。参与该项目的汽车原始设备制造商有奥迪,宝马,戴姆勒克莱斯勒,菲亚特,通用汽车／萨博和福特、沃尔沃,不锈钢生产企业有蒂森克虏伯不锈钢公司,     

本钢汽车板通过北京现代汽车认证

一月初,本钢汽车板一次性通过了北京现代汽车有限公司的认证,这是本钢汽车板进入现代汽车的供应商平台,拥有供货通行证,提高竞争力的标志。     

汽车钢板

烘烤硬化高强度钢板 汽车大型覆盖件,由于零件中间变形量小,加工硬化作用不明显,汽车在行驶中,零件经常受沙石或者重物的碰击,在零件表面产生凹陷,为避免这种情况,希望钢板有较高的“抗凹陷性能”,一般认为,屈眼强度越高,抗凹陷能力越强。但屈服强度越高,钢板的冲压     

汽车不锈钢板

1,汽车的现状 日本汽车1980年生产量超过1000万辆,超越美国变成世界第1位,表1是5年来的生产统计,保有台数约4000万辆。顾客对车的考虑,最好是多样化,价格合适;不易发生故障,长时间拥有车辆,长寿命的汽车时代。     

汽车钢板

序言 汽车工业是国家的支柱产业,汽车是使用薄钢板最多的交通工具。近百年来汽车工业发展很快。从1955年起,世界汽车产量以年3.5％的速度递增,1994年直到现在,汽车总产量最高的一年,为5000万辆。如今,世界汽车保有量约5亿辆,预计今后25年还要翻一翻。     

浦项与雷诺汽车共同开发汽车用镁合金板

韩国浦项制铁集团11月24日宣布,已与法国雷诺汽车集团于11月23日签署合作协议,双方今后将共同开发使用镁合金板取代部分钢板的汽车轻量化技术。雷诺汽车从今年开始启动与汽车用原材料供应商共同展开的研究计划,与浦项制铁的合作是该计划的第一步。双方约定,正式的研究工作将从2012年开始,目的是研究出可以量产的镁合金汽车板材。浦项制铁早在数年前就已经展开相关的研究,     

商用汽车市场调研及安钢汽车用钢分析

阐述了汽车分类、汽车工业发展特点及商用汽车发展趋势,通过对汽车市场进行调研分析,掌握汽车市场用钢需求量、不同车型单车用钢量、用钢品种和规格,并结合安钢1780mm热连轧机组研发汽车用钢品种、结构、规模,提出了安钢商用汽车研发推进方案。     

攀长钢公司汽车运输改用CNG汽车可行性分析

目前我国CNG汽车仅仅局限于城市公交车辆,随着天然气汽车技术的成熟和加气站网络化建设的完善,实现天然气汽车应用于冶金企业的时机已经到来。分析攀长钢公司使用CNG汽车的优势,提出了相关建议。     

汽车服务工程专业汽车商务课程群框架构建

论述了汽车服务工程专业汽车商务课程群建设的必要性,对汽车商务课程进行划分并构建课程群,提出了汽车服务工程专业汽车商务课程群建设的研究思路。     

Modeling the Effect of Water Diversion on the Temperature of Mountain Streams

Water diversion for hydroelectric power generation impacts the temperature of mountain streams. Such changes are estimated by using a coupled one-dimensional dead-zone heat balance model. In very steep river sections, the dissipation of kinetic energy is the dominant heat source. For such streams, water diversion has only a minor effect on water temperature, because dissipation-induced temperature changes are independent of discharge. In contrast, in river sections of gradual slope, the influence by solar radiation, long-wave radiation, and heat exchange with the streambed is stronger. In such cases, a discharge reduction can lead to significant temperature changes. For a small stream in the southern Swiss Alps, model results show that diversion increases temperature by about 3.7 (±0.9)°C in a 21 km long river section under high solar radiation during summer. During a cold winter episode, water temperature is estimated to be about 1.8 (±0.8)°C lower compared to natural conditions. This heat balance model can also be used to simulate the effect of different measures to reduce water temperature changes in affected streams.     

To honor Fechner and obey Stevens: Relationships between psychophysical and neural nonlinearities.

G. T. Fechner (1860/1966) famously described two kinds of psychophysics: Outer psychophysics captures the black box relationship between sensory inputs and perceptual magnitudes, whereas inner psychophysics contains the neural transformations that Fechner's outer psychophysics elided. The relationship between the two has never been clear. Moreover, psychophysical power laws are found in almost every sensory system, yet the vast majority of neurons show sigmoid nonlinearities. Here, we selectively review the literatures on psychophysical and physiological nonlinearities and show how they can be placed within a framework for understanding the relationship between inner and outer psychophysics: a neural organization with a logical structure commensurate to outer psychophysical theory. In theoretical treatments of Stevens's law, the power law is a consequence of combining a Weber's law scaling of inputs with a Weber's law–like scaling of sensation magnitudes, yielding an exponent that is the ratio of the Weber constants. A neural derivation using physiological sigmoid nonlinearities should be commensurate to this internal logic. There is a class of models in which two nonlinear neural mechanisms (e.g., a sensory channel and the cortical numerosity mechanism tapped by magnitude estimation) are coupled through feedback, yielding power law behavior as an emergent property of the system, with an exponent that is a ratio of neural coupling strengths. Rather than a discrepancy between psychophysics and physiology, these models suggest complementarity between inner and outer psychophysics, because the Weber constants required for outer psychophysics modeling can be derived from the sigmoid nonlinearities of inner psychophysics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种四极质谱仪射频电源控制与数据采集系统的研制

四极杆射频电源是四极质谱仪的核心部件,传统的四极杆射频电源控制与数据采集一般采用模数转换器(ADC)与主控芯片搭配来实现,先将信号进行预分频,再用ADC采集,处理速度慢、功能单一。本文基于微控制器(ARM)和现场可编程门阵列(FPGA),研制了一种新型的射频电源控制与数据采集系统。ARM用于与上位机通讯及模块间的级联控制,FPGA负责交直流控制电压的输出、扫描时序产生及数据采集,进而实现仪器的质量数扫描、跳峰扫描等功能。选用基于上述设计的电感耦合等离子体质谱仪(ICP-MS)样机,依照四极杆电感耦合等离子体质谱仪校准规范JJF 1159—2006进行了分辨率、灵敏度、质量轴稳定性和线性测定试验,测定结果符合该规范要求。     

面向风电消纳的铝电解槽瞬态温度场的波动特性研究

针对铝电解系列消纳风电过程中电流波动对热场作用过程不明确的现状,应用电热场瞬态强耦合模型对某420kA大型铝电解槽在一个完整消纳周期内的热场进行研究。分别针对消纳电流为设计电流的2%、5%和10%三种情况,消纳持续周期为2h,恢复周期为6h,计算铝电解槽温度场的瞬态变化特性。结果表明,槽内各区域的温度均随着强化幅度的增加而增加,变化最大的区域为熔体区;越靠近熔体区域的部分,温度的变化幅度越大;而除导杆、钢爪外,越靠近槽壳表面部分,温度的变化幅度越小。在电流恢复至正常值期间,电解槽温度下降速度缓慢,需要比较长的时间才能恢复到正常值,故铝电解槽电流波动幅度不宜太大。     

矿热炉低压无功补偿利弊分析

介绍了提高矿热炉功率因数的途径,论述了低压无功补偿关键技术参数,分析了矿热炉低压无功补偿方式的优缺点,指出合理选用低压无功补偿装置后,产品质量、产量、功率因数、单耗等指标均有明显的改善和提高,取得较好的经济效益。     

Semiactive Connected Control Method for Adjacent Multidegree-of-Freedom Buildings

The connected control method (CCM) has been shown previously to be a viable means to protect adjacent flexible structures. The CCM works by using an auxiliary structure to provide a reaction force for control. The CCM can be applied to a variety of structural systems including civil, mechanical, or aerospace structures, and can incorporate various types of control strategies including passive, active, or semiactive control. This paper focuses on the application of the CCM to seismically excited adjacent buildings employing semiactive control and extends the previous research in semiactive coupled building control to examine the effects of relative building height and coupling link location on the semiactive performance. The optimal semiactive coupled building configuration is shown to follow two guidelines: (1) The dominant frequencies of the two coupled buildings do not coincide and (2) the coupling link is not placed at the node of a dominant vibratory mode. Additionally, it is shown that semiactive control is able to achieve performance similar to the optimal passive control at a fraction of the required control device force.     

口环密封对多级离心泵湿转子横--轴双向耦合动特性的影响

为探究口环密封对多级离心泵转子横-轴双向耦合振动的影响,基于空间欧拉角变换及有限元法,建立了多级离心泵转子系统叶轮和轴系的微分运动方程,在此基础上,充分考虑口环流体激振力和多种轴向力的耦合作用,利用矩阵运算方法建立了多级离心泵湿转子的横-轴双向耦合振动模型,并采用Newmark法对双向耦合系统的瞬态动力学特性进行求解,重点研究了口环密封长度、压差和间隙对系统耦合振动特性的变化规律,计算了不同密封参数下的流体激振力.计算结果表明,口环密封对转子系统横向振动的洛马金效应随着密封长度和压差的增大以及间隙的减小愈发明显,转子系统的横向稳态振动收敛速度快于轴向稳态振动的收敛速度,两向瞬态振动的振动频率呈现出完全不同的特性.此外,密封的流体激振力与密封长度呈现非线性变化关系,而与密封压差和间隙呈现线性变化关系.      

Inverse First-Order Reliability Method for Probabilistic Fatigue Life Prediction of Composite Laminates under Multiaxial Loading

A new methodology for concurrent dynamic analysis and structural fatigue prognosis is proposed in this paper. The proposed methodology is based on a novel small timescale formulation of material fatigue crack growth that calculates the incremental crack growth at any arbitrary time within a loading cycle. It defines the fatigue crack kinetics based on the geometric relationship between the crack-tip opening displacement and the instantaneous crack growth rate. The proposed crack growth model can be expressed as a set of first-order differential equations. The structural dynamics analysis and fatigue crack growth model can be expressed as a coupled hierarchical state-space model. The dynamic response (structural level) and the fatigue crack growth (material level) can be solved simultaneously. Several numerical problems with single-degree-of-freedom and multiple-degree-of-freedom cases are used to show the proposed methodology. Model predictions are validated by using coupon testing data from open literature. Following this, the methodology is demonstrated by using a steel girder bridge. The proposed methodology shows that concurrent structural dynamics and material fatigue crack growth analysis can be achieved. Cycle-counting method in the conventional fatigue analysis can be avoided. Comparison with experimental data for structural steels shows a satisfactory accuracy by using the proposed coupled state-space model.     

Dendritic and synaptic effects in systems of coupled cortical oscillators

We explore the influence of synaptic location and form on the behavior of networks of coupled cortical oscillators. First, we develop a model of two coupled somatic oscillators that includes passive dendritic cables. Using a phase model approach, we show that the synchronous solution can change from a stable solution to an unstable one as the cable lengthens and the synaptic position moves further from the soma. We confirm this prediction using a system of coupled compartmental models. We also demonstrate that when the synchronous solution becomes unstable, a bifurcation occurs and a pair of asynchronous stable solutions appear, causing a phase lag between the cells in the system. Then using a variety of coupling functions and different synaptic positions, we show that distal connections and broad synaptic time courses encourage phase lags that can be reduced, eliminated, or enhanced by the presence of active currents in the dendrite. This mechanism may appear in neural systems where proximal connections could be used to encourage synchrony, and distal connections and broad synaptic time courses could be used to produce phase lags that can be modulated by active currents.     

Modification of Canal Flow due to Stream-Aquifer Interaction

Unsteady canal flow in an integrated canal-flow–groundwater-flow system is analyzed by solving the coupled equations governing canal flow, groundwater flow and the seepage between them. Analytical solutions are obtained for the coupled system for small water-level disturbances using Fourier analysis methods and complex variables. Dimensionless parameter groups characterizing the aquifer, the canal, and the sediment layer are identified using the governing equations and the solution. The influence in the aquifer and the semipermeable bottom sediment layer due to disturbances in canal flow is studied. The analytical solutions are compared to numerical solutions obtained using the MODFLOW model and the Hydrologic Simulation Engine of the South Florida Regional Simulation Model. Results of the analysis are useful in determining the range of aquifer, sediment, and canal characteristics for which stream-aquifer interaction is important. The results can be used to determine the conditions for which the canal is hydraulically disconnected from the aquifer because of the sediment layer. The analytical solution is useful to understand the propagation characteristics of small-amplitude water-level disturbances in the canal and the aquifer. The characteristics studied include the amplitude decay constant and the speed. The solution can be used to design benchmark problems that can be used to evaluate integrated canal-flow–groundwater-flow models. The results of the study can be used to estimate the space and time steps needed in the canal and the aquifer when simulating stream-aquifer interaction.