万能轧机轧制H型钢的数值模拟分析

利用显式动力学有限元分析方法，模拟了H型钢在轧制过程中的变形情况，分析了影响金属流动过程的主要因素。研究结果表明，轧件的腿腰延伸比和腿宽对金属的流动趋势有明显的影响。     

基于固定时间扰动观测器的水面无人艇精确编队控制

在水面无人艇(USV)编队控制中,控制效果易受系统初始状态和内外部扰动的影响.为此,研究一类具有复杂干扰下的USV编队控制问题,结合固定时间扰动观测器提出一种领航-跟随编队控制方法.首先,提出一种基于固定时间滑模的跟踪控制(FTSM-TC)策略,在固定时间内保证领航艇快速跟踪期望轨迹;然后,为处理内外部未知干扰设计固定时间扰动观测器(FTDO),从而保证在固定时间内对编队系统中的未建模动态和外部复杂干扰进行精确辨识.所提出的基于FTDO的编队控制(FTDO-FC)策略,使编队控制系统在固定时间内收敛并保持稳定的期望队形,仿真结果表明,所设计控制方法能够有效解决存在复杂未知扰动情况下的USV编队控制问题,且收敛时间与系统初始状态无关.     

白釉还原焰烧成的研究

氧化焰白釉技术已经非常成熟,但对于还原焰来说,单纯通过提高釉中锆的含量,也不一定实现白釉可以完全遮盖住坯体,并呈现较高的白度。所以,研究是否可以通过改变乳浊剂的颗粒粒径来实现白釉的还原焰烧成。乳白釉配方的釉用乳浊剂种类较多,有氧化锡、氧化锌、锆英砂、氧化锆等等。鉴于氧化锆受气氛影响较小,乳浊效果较好,是较稳定的乳浊剂。本次试验选择氧化锆和硅酸锆作为乳浊剂。硅酸锆的粒度不同,可以对釉配方性能产生较大的影响。     

浑河流域沈阳段氨氮污染源核算及水质模拟分析

为研究氨氮污染源的排放情况,根据排污系数法核算了沈阳市浑河流域2015年各类点源、面源污染物情况,并利用QUAL2K模型对该流域氨氮进行模拟,得到氨氮在不同水期的变化趋势。结果表明,浑河沈阳段氨氮2015年入河总量为3 840.1t,氨氮主要来自农村非点源污染(占氨氮入河总量约92%,其中包括畜禽养殖污染67%、农业灌溉20%、农村生活污水4%),点源污染物占比仅8%;另外流域所包含两条河流浑河干流、蒲河支流的氨氮入河量分别为1 774.0、2 066.1t,且均以畜禽养殖污染为主。QUAL2K模型对氨氮的模拟结果与不同水期实测值相对误差在4%~20%之间,氨氮模拟浓度整体水平为枯水期>平水期>丰水期,其中浑河干流中游氨氮污染最为严重,枯水期氨氮浓度最大值3.6mg/L,为丰水期的12倍;而蒲河支流中下游污染情况较为复杂,在不同水期均存在超标风险。     

Facile preparation of Ni,Co - Alloys supported on porous carbon spheres for supercapacitors and hydrogen evolution reaction application

Carbon nanomaterials that are electrochemically bifunctional and active in supercapacitor and hydrogen-evolution-reaction (HER) applications have attracted recent research attention. We have prepared porous carbon spheres - doped Ni, Co - alloys by using a hydrothermal method with melamine and pectin as precursors and with the addition of nickel nitrate and cobalt nitrate. The corresponding materials exhibit good electrochemical performance and excellent electrocatalytic activity for HER. The overpotential (OP) of the as-prepared materials can achieve 240 mV keeping a Tafel slope (TS) of 55 mV dec⁻¹ at 10 mA cm⁻² in an acid (0.5 M H₂SO₄) solution. The corresponding samples maintain stability after 24 h and 5000 cycles in the chronovoltage and cyclic voltammetry methods, respectively. When the as-prepared materials are oxidized by 30% H₂O₂ for 12 h, the corresponding as-prepared oxidation samples exhibit excellent electrochemical performance in a supercapacitor application. The specific capacitance (SC) of the as-obtained materials reaches 312 F g⁻¹ at 1 A g⁻¹ with decent rate capability and cyclic stability. This work provides new applications for bifunctional electrochemically active materials.     

Characteristics and pathways of hydrogen produced by pulsed discharge in ethanol-water mixtures

Hydrogen produced by pulsed discharge in ethanol-water mixtures is optimized in this work. A needle-balls configuration is designed, which is fit for situ hydrogen production in transportation. The energy yield of hydrogen can attain 141.3 gH₂/kWh, which is better than most existing methods. The high energy yield attributes to the special discharge characteristics. During the discharge, shock waves make the balls jumping in the reactor that increase the randomness and local strength of discharge. The microscopic pathway of pulsed discharge in ethanol-water mixtures is also analyzed by the comparison of rate constants. The main products can be analyzed from the microscopic pathway. In addition, CH₃CHO, CH₂O are important intermediates, which may be good additives for increasing hydrogen yield.     

A new technique for optimal time-dynamic distribution substation and feeder planning

This paper presents a new model for optimally sizing and locating distribution substations and feeders in a time-dynamic power distribution system. Recognizing that both linear and nonlinear loads are present within the system, the model's objective is to minimize the combined costs of the construction of substations and feeders with that of losses occurring at fundamental and harmonic frequencies. System specifications include power demand, power capacity, and logical restrictions. Two main contributions of this paper are: (1) the model captures the nonlinear costs due to power flow, as opposed to simplifying linear assumptions found in the literature; and (2) the effects of harmonics are considered. The model is a mixed 0-1 quadratic program, whose mathematical structure permits the application of generalized Benders' decomposition as a solution methodology. The effectiveness of the developed model and solution procedure is illustrated by application of a test example from the literature. The effects of nonlinear power losses and harmonic distortion are shown to influence the planning strategy.     

生活垃圾焚烧飞灰固化稳定化安全处置及建材资源化利用进展

生活垃圾焚烧发电是城市生活垃圾未来的主要发展方向,但其排放的飞灰属危险废物,含重金属等有害物质,对自然环境和人类健康存在潜在危害.飞灰的固化稳定化是当前主要的处置方式,同时也是资源化利用的主要途径.综述了目前国内外固化稳定化安全处置飞灰的主要方式,分析了各个方法的优缺点,总结了飞灰在建筑材料领域中的研究现状,探讨了未来...     

涂层对速凝3D打印水泥砂浆力学性能的影响

3D打印砂浆普遍存在层间界面粘结较弱、抗折强度较低的问题,而膨胀水泥浆涂层涂覆于砂浆表面可产生表层压应力,进而提升其抗折强度,作为界面剂涂覆于层间可同时增强其界面粘结强度。本文通过将硫铝酸盐水泥与膨胀剂混合而成的涂层涂覆于速凝3D打印砂浆的表面与层间,研究了该涂层对不掺纤维及掺0.5%(体积分数)玄武岩纤维3D打印砂浆试件力学性能的影响规律。结果表明,涂覆层间涂层对无纤维与掺纤维速凝3D打印砂浆的层间界面粘结强度提升率分别为21.4%、12.2%,同时对其抗压强度也有一定提升作用。仅涂覆表面涂层与仅涂覆层间涂层对3D打印砂浆的抗折强度提升效果相当;同时涂覆表面及层间涂层对3D打印砂浆的抗折强度提升效果最显著,与无纤维、掺纤维的无涂层试件相比,提升率最高分别可达44.2%、23.2%。涂层对于无纤维3D打印试件层间粘结强度及抗折强度的提升效果优于掺纤维试件。