直流电弧炉几种型式炉底电极的比较与评价

从安全、导电、绝缘、搅拌、偏弧、炉子吨位，冷却方式与允许电流密度，砌筑与维修方式，起动方式，炉底电极寿命及费用等十几个方面对直流电弧炉不同型式炉底电极进行了综合比较与评价，指出每种型式炉底电极都各有优点和缺点，绝对肯定或否定哪种型式都不恰当，用户可以根据自己的认识与工厂的实际情况选择合适的炉底电极型式。对我国直流电弧炉的发展提出了几点建议。     

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岩石扩散系数是岩石固有的基本物理量之一，是研究天然气扩散最重要的参数。前人用实验室实测数据求取系数，致使实验时间过长（达千余小时），并存在某些不确定因素；或是在封闭式实验中使用稳定模型处理非稳态的扩散实验过程，导致所求取的扩散系数值产生了大约一个数量级的偏差（误差为１／２～４倍）。在总结了前人经验的基础上，由扩散理论与数学模型相结合的方法，推出了用实测数据求取扩散系数的非稳态模型，并获得了解析解。通过理论分析和大量的实测资料的反复对比计算表明：用该非稳态模型所处理的实测数据，能很好地反映实验中天然气通过岩样的扩散规律。该方法不仅能纠正前人模型所产生的严重偏差，并且可以在不改变原有封闭式实验装置和实验方法的条件下，极大地提高所测岩样的扩散系数精度，同时将原有实验时间缩短至两小时至数小时范围内，从而降低实验成本，提高实验效率，该方法具有较高的推广应用价值。     

数值模拟舰船排气引射装置的红外特性

采用к－з两方程模型和壁面函数法数值模拟舰船排气系统红外抑制装置缩比模型的湍流场和温度场分布。经实验校模后利用自模化原理半数值模拟方法推广到实物装置上去。在建立了观察点与装置有关区域之间看视关系后，利用Ｈｏｔｔｅｌ的区域法就可计算获得装置的红外辐射场分布。     

尖山铁矿矿体地质特征新认识及找矿方向

尖山铁矿床产于下元古界尖山群袁家村组含铁岩系中，矿体受尖山向斜构造控制，同时断裂构造对矿亦有较大的影响，使主矿体向下延伸和错移。     

黄山鲁森林公园白水湖景区及山顶景观工程规划

黄山鲁森林公园位于南沙区的中心城区（小南沙）内,是南沙区中心城区的生态绿色核心,是都市中珍贵的绿色资源。整个公园占地约1200多公顷,主峰海拔295 m是广州南部地区的最高峰,是广州地区最大的开放式森林公园。     

Effects of Mn2+ on the electrical resistance of electrolessly plated Ni–P thin-film and its application as embedded resistor

The effects of manganese sulfate monohydrate (denoted as MSM) on the properties of electroless Ni–P thin-film were investigated. The properties of Ni–P thin-film were examined by means of atomic force microscopy (AFM), cyclic voltammetry, scanning electron microscopy (SEM), X-ray diffraction, energy-dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. AFM and SEM results showed that MSM had significant influences on the morphology, including the formation of smaller nodules, nano-size particles boundaries on both surface and inside of nodules. Due to the specific topologies, the resistance of Ni–P thin-film deposited with MSM was increased. Based on the characterization results, we summarized that the Mn²⁺ or Mn²⁺-compound were primarily confirmed to act as the stabilizer in Ni–P electroless process. Moreover, the verification test for Ni–P thin-film in application as embedded resistor was carried out through electrical, thermal stability examination by means of current–voltage (I–V), temperature coefficient of resistance and thermal shock tests, respectively. Experiment results demonstrated the Ni–P thin-film deposited with MSM is qualified for embedded resistors.     

温度/压力阀在空气源热泵热水器水箱的应用浅析

本文针对仅通过热泵系统加热的空气源热泵热水器水箱,通过对温度/压力阀的使用环境分析,结合热泵加热的自身特点,提出该类产品内胆超压保护不同于电热水器,可以用普通的安全阀进行替代。     

CORDIC-Based Unified Architectures for Computation of DCT/IDCT/DST/IDST

In this paper, CORDIC (coordinate rotation digital computer)-based Cooley-Tukey fast Fourier transform (FFT)-like algorithms for power-of-two point discrete cosine transform/discrete sine transform/inverse discrete cosine transform/inverse discrete sine transform are proposed and their corresponding unified architectures are developed by fully reusing the unique two basic processing elements. The proposed algorithms have some distinguished advantages, such as FFT-like regular data flow, unique post-scaling factor, and arithmetic-sequence rotation angles. The developed unified architectures can compute four different transforms by simple routing the data flow according to the specific transform without feeding different transform coefficients or different transform kernels. The unfolding technique is used to overcome the problem of difficult to realize pipeline that occur in iterative CORDIC algorithms. Compared to existing unified architectures, the proposed architectures have a superior performance in terms of hardware complexity, control complexity, throughput, scalability, modularity, and pipelinability.     

An advanced monolithic digitalized random carrier frequency spread-spectrum clock generator for EMI suppression

A novel monolithic digitalized random carder frequency modulation spread-spectrum clock generator (RCF-SSCG) is proposed. In this design, the output frequency of the proposed RCF-SSCG changes with the inten-sity of the capacitive charge and discharge current. Its analytical model is induced and the effect of the modulation parameters on the spread spectrum is numerically simulated and discussed. Compared with other works, this design has the advantages of small size, low power consumption and good robustness. The circuit has been fabricated in a 0.5 μmCMOS process and applied to a class D amplifier in which the proposed RCF-SSCG occupies an area of 0.112 mm2and consumes 9 mW. The experimental results confirm the theoretical analyses.     

Stabilization And Tracking Of Underactuated Surface Vessels In Random Waves With Fin Based On Adaptive Hierarchical Sliding Mode Technique

Trajectory tracking and roll stabilization are both vital practices in ship motion control. Trajectory tracking is a kind of low‐frequency control, while roll stabilization by means of fins is a kind of high‐frequency control. However, they have been studied separately previously; most tracking control of underactuated surface vessels in the previous studies do not account for roll stabilization by means of fins. In reality, however, they are an integral system. In this paper, a simple control strategy is proposed to achieve trajectory tracking and fin roll stabilization simultaneously. Four degrees of freedom derived from a six degrees of freedom mathematical model of a surface vessel is considered, including surge, sway, roll and yaw. Surge force, roll moment and yaw moment are considered as control inputs, while position, yaw angle and roll angle are controlled. The number of control inputs is fewer than the outputs to be controlled. Therefore, we are dealing with an underactuated problem. An adaptive hierarchical sliding mode control technique is employed to deal with the underactuation. Stabilization of underactuated surface vessels is studied as a special case. Random waves are applied to test the robustness of the designed controllers. Lyapunov stability theory is used to show the stability of closed‐loop system. The simulation results verify the effectiveness of the proposed strategy.