Comparison of various balance systems for energy conservation in a vertically articulated manipulator with three joints

It is important to conserve dissipated energy from machines in order to reduce global warming. This paper discusses energy conservation in a vertically articulated three-joint manipulator with a rotation–pivot–pivot structure. The amount of dissipated energy can be decreased by canceling out the gravity on the second and the third links of the manipulator using a mass balancer or a spring balancer. Mass balancers are designed optimally by diminishing the inertia matrix so that the amount of dissipated energy can be minimized. Three kinds of counterbalancer systems, which include a mass–mass balancer, a spring–mass balancer and a spring–spring balancer, are designed optimally. Energy is compared among the three types of counterbalancers mounted on a three-link manipulator in simulation. The simulation indicates that a spring–mass balancer is more practical because of the considerable energy conservation effect and simplicity in implementation. In order to confirm the simulation results, the dissipated energy is measured experimentally using a practical system of a directly-driven manipulator on which a suboptimal mass–mass balancer or a spring–mass balancer is mounted. As a result, the measured dissipated energy is approximately the same as the result obtained by simulation.     

Synthesis and characterisation of Si3N4p/Cu nanocomposite powders by high energy ball milling

Abstract

The present work reported the preparation of Cu–25 wt-%Si₃N₄ nanocomposite powders via high energy ball milling (HEBM). The phases and morphologies of as-milled powders with various milling times were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results showed that with increasing the milling time, the irregularly shaped Cu powder became flattened, and, subsequently, refined and near spherical. After 12 h milling, the particle size of Cu–Si₃N₄ composite powders was in the range of 200–300 nm, while the grain size of Si₃N₄ particulates, 10–25 nm, was well within a nanometre scale. A uniform distribution of the nanosized Si₃N₄ reinforcing phase throughout the Cu matrix was successfully obtained. A reasonable mechanism for the formation of Cu–Si₃N₄ nanocomposite powders during HEBM was also proposed.     

Control of silicon in high carbon ferrochromium produced in submerged arc furnace through redistribution of quartzite in the charge bed

Abstract

High carbon ferrochromium produced in a submerged arc furnace may contain as much as 4%Si. A high level of silicon in this alloy is not desired. In addition to bringing down the value of the alloy, a high level of silicon increases the specific energy consumption during production of the alloy. Controlling the proportion of silica and coke in the charge can help in bringing down the level of silicon in the hot metal. This strategy is adopted by some ferrochromium manufacturers. However, these practices lead to difficulties in tapping, and to reduced recovery of chromium. A thermochemical analysis of the process showed that silicon in the hot metal was at equilibrium with the slag only at high temperatures, which usually prevailed in regions close to the electrodes. Based on this analysis, a strategy was devised to control silicon in the hot metal by appropriate redistribution of quartzite at the top of the charge bed. Trials were carried out at an industrial plant to control the silicon level using this strategy. Results showed that the silicon level in the hot metal was drastically reduced on redistribution of quartzite. This method can result in a reduction of specific energy and specific coke consumption.     

“能源之星”实验室认可最新政策

针对EPA的最新政策和CNAS在＂能源之星＂实验室认可的实施要求,分析了＂能源之星＂实验室认可关注要点：认可评审、认可评定、认可报告等要求,为实验室通过该项目认可、获得EPA注册资格提供参考。     

Dynamic compressive flow behaviour of S15C low carbon steel over wide temperature range

Abstract

The present study utilises the compressive split Hopkinson pressure bar to investigate the dynamic flow behaviour of S15C low carbon steel at temperatures ranging from 25 to 800°C. The effects of strain rate and temperature on the mechanical response and microstructure of the metal are evaluated. The flow stress of S15C low carbon steel is found to increase with increasing strain rate and to decrease with increasing temperature. Furthermore, the material temperature sensitivity is enhanced at higher strain rates. The study determines the strain rate sensitivity parameter and the activation volume under various strain rates and temperatures. It is found that the activation energy ΔG^* varies as a function of strain rate and temperature and attains a maximum value of 62 kJ mol^?1 under the current test conditions. A Zerilli–Armstrong bcc constitutive model is applied to describe the high strain rate plastic behaviour of S15C and is shown to produce acceptable results. Microstructural examination by TEM reveals that the dislocation density and degree of dislocation tangling both increase with increasing strain rate. Additionally, TEM observations indicate that a higher strain rate reduces the size of dislocation cells. Furthermore, it is shown that the annihilation of dislocations occurs more readily at elevated temperatures. The current results provide a valuable reference for the application of S15C low carbon steel in high speed plastic forming processes.     

Multiple heat isothermal stress rupture correlations for type 316L(N) stainless steel and their use Part 2 – Applications for nuclear grade type 316L(N) stainless steel base metal and its weld metal

Abstract

The 'reference' multiple heat isothermal stress rupture correlations for stainless steel types 316 and 316L(N) base metals derived in Part 1 are used for establishing those for a specific 316L(N) stainless steel base metal and also its weld, both candidates for the forthcoming prototype fast breeder reactor at Kalpakkam. The phases that form in the weld metal during creep are the same as those in the base metal; however, the uniformly distributed δ ferrite ( ~ 7 ferrite number) in vermicular morphology present in the initial microstructure accelerates their formation and increases their quantities, resulting in poorer stress rupture properties. A simple modification allows for correlating and extrapolating the weld data to long rupture lives using the multiple heat isothermal correlations developed for the base metal.     

Factors affecting mechanical properties of resistance spot welds

Abstract

The present paper addresses the factors governing the mechanical performance of low carbon resistance spot welds. Correlations among the process parameters (welding current, welding time, electrode force and holding time), physical spot weld attributes and mechanical performance are analysed. Peak load and energy absorption of spot welds during the tensile shear test are used to describe spot welds performance. It is shown that weld nugget size, electrode indentation, failure mode and strength/ductility of the failure location are the main factors affecting peak load and energy absorption of spot welds.     

Factors influencing willingness-to-pay for the ENERGY STAR label

In the United States, nearly 17% of greenhouse gas emissions come from residential energy use. Increases in energy efficiency for the residential sector can generate significant energy savings and emissions reductions. Consumer labels, such as the US Environmental Protection Agency's ENERGY STAR, promote conservation by providing consumers with information on energy usage for household appliances. This study examines how the ENERGY STAR label affects consumer preferences for refrigerators. The results of an online survey of a national sample of adults suggest that consumers are, on average, willing to pay an extra $249.82–$349.30 for a refrigerator that has been awarded the ENERGY STAR label. Furthermore, the results provide evidence that respondent willingness-to-pay was motivated by both private (energy cost savings) and public (environmental) benefits.     

实用化精馏塔计算机节能控制系统

论述了基于低成本、高功能小型集散系统实现一典型精馏塔节能改造的系统和控制方案。控制系统采用实用可靠的先进控制策略改善精馏塔灵敏点和塔顶温度特性，目动修正回流量，有效地减少能耗，提高了产品的稳定性，经济效益显著。计算机系统设计合理，配有灵活的组态、控制算法和在线调试功能，人机界面友好，保证了应用和操作的简易性。     

Application of Genetic Algorithms for biped robot gait synthesis optimization during walking and going up-stairs

Selecting an appropriate gait can reduce consumed energy by a biped robot. In this paper, a Genetic Algorithm gait synthesis method is proposed, which generates the angle trajectories based on the minimum consumed energy and minimum torque change. The gait synthesis is considered for two cases: walking and going up-stairs. The proposed method can be applied for a wide range of step lengths and step times during walking; or step lengths, stair heights and step times for going up-stairs. The angle trajectories are generated without neglecting the stability of the biped robot. The angle trajectories can be generated for other tasks to be performed by the biped robot, like going down-stairs, overcoming obstacles, etc. In order to verify the effectiveness of the proposed method, the results for minimum consumed energy and minimum torque change are compared. A Radial Basis Function Neural Network is considered for the real-time application. Simulations are realized based upon the parameters of the 'Bonten-Maru I'humanoid robot, which is under development in our laboratory. The evaluation by simulations shows that the proposed method has a good performance.