Combustion and Sulfur-fixing Performance of Pulping Black Liquor Coal-water Slurry

The effects of adding pulping black liquor and other additives to coal-water slurry(CWS) on the sulfur-fixing performance of the resultant mixture(pulping black liquor coal-water slurry) were evaluated. The experimental results demonstrated that the ash content of the black liquor coalwater slurry decreased as the addition of pulping black liquor in the mixture increased. Nevertheless, the addition amount should be appropriately selected to ensure that the black liquor coal-water slurry had a moderate calorific value. Addition of black liquor improved the combustion performance of CWS by lowering the ignition point and stabilizing the combustion process; moreover, the sulfur-fixation ratio after combustion increased by 12 to 16 percentage points than that of CWS, and the content of high-melting-point salt in the ash from CWS after adding black liquor was low. The sulfur-fixing ratio of CWS after adding a sulfur-fixing agent was effectively increased by 25 to 30 percenatge points, but with compromise of the fluidity and stability of the CWS; thus, the addition amount of a sulfur-fixing agent should be optimized.

Performance of Random Contention PRMA: A Protocol for Fixed Wireless Access

This paper introduces a packet reservation multiple access (PRMA) with random contention for fixed wireless access communications. The performance of PRMA scheme with random contention is compared with the performances of traditional PRMA under permission contention scheme. The proposed scheme is a simpler contention mechanism that does not depend on a pre-determined permission probability as PRMA under permission contention scheme. In this new method, terminals select the contention slot uniformly from the pool of remaining free slots in the current frame. We evaluate the performance of the new contention mechanism in terms of various metrics including maximum number of carried voice calls and packet delays for a given acceptable drop rate of voice packets. We show that the new mechanism is superior to that of PRMA under permission contention scheme for loaded systems and is expected to be insensitive for traffic source burstiness.

Unified Coordinate System Model for Performance Calculation of Fix-pad Journal Bearing with Different Pad Preload

Traditional model for calculating performance parameters of a fix-pad journal bearing leads to heavy workload, complicated and changeable formulae as it requires deriving various geometric formulae with different bearing types such as circular journal bearing, dislocated bearing and elliptic bearing. Considering different pad preload ratios for non-standard bearing, traditional model not only becomes more complicated but also reduces scalability and promotion of the calculation programs. For the complexly case of traditional model while dealing with various fix-pad journal bearings, unified coordinate system model for performance calculation of fix-pad journal bearing is presented in the paper. A unified coordinate system with the bearing center at the origin is established, and the eccentricity ratio and attitude angle of axis relative to each pad are calculated through the coordinates of journal center and each pad center. Geometric description of fix-pad journal bearing is unified in this model, which can be used for both various standard bearing and non-standard bearing with different pad preload ratios. Validity of this model is verified with an elliptical bearing. Performance of a non-standard four-leaf bearing with different pad preload ratios is calculated based on this model. The calculation result shows that increasing preload ratio of the pad 1 and keeping that of the left three pads constant improves bearing capacity, stiffness and damping coefficients. This research presents a unified coordinate system model unifies performance calculation of fix-pad journal bearings and studied a non-standard four-leaf bearing with different pad preload ratios, the research conclusions provides new methods for performance calculation of fix-pad journal bearings.

Effect of Thermal Regeneration on the Breakthrough Performance of Ceramsite Saturated with Methylene Blue

The regeneration of a spent packing is crucial with respect to the development of circular economy and abstemious society.Thus,the effects of regeneration temperature,resistant time,heating rate,and regeneration cycle on the breakthrough performance of methylene blue(MB)dye⁃exhausted ceramsite in a two⁃stage fixed⁃bed column were studied in this work.Results illustrate that the ceramsite exhibited excellent potential regeneration properties under the following optimal regeneration conditions:treatment temperature was 600°C,resistant time was 15 min,heating rate was 20℃/min,regeneration cycle was over 9 cycles,and the breakthrough time,saturation time,regeneration efficiency(RE),and regeneration loss rate(RLR)were 540 min,1020 min,64.61%,and 17.73%,respectively.The RE declined by 35.14%in over 1 cycle,while the RLR increased by 3.15 times in over 9 cycles.Besides,Thomas model was suitable to describe the two⁃stage fixed⁃bed column adsorption and thermal regeneration process with R2=0.978.In conclusion,a thorough understanding of the regeneration behavior of the two⁃stage fixed⁃bed column packed with ceramsite provides reference to obtain an effective and feasible regeneration approach,and it is beneficial for further application in water treatment.

Moving Personal-Cell Network: Characteristics and Performance Evaluation

Recent years have witnessed a huge demand for ubiquitous communications services from continuously moving users. In order to provide seamless network services to high-mobility users, one of the promising solution proposed by 3 GPP is the deployment of moving-relays. In this article, we introduce the concept of Moving-Personal-Cell(mPC), which is a type of moving-relays. mPC is a user-centric network, which aims to provide reliable network services to moving users. A mPC receives data-traffic from eNB and its neighboring mPCs via wireless backhaul and sidehual links respectively and forwards the received data to its serving users. In addition to this, mPC can also increase the network capacity by caching and distributing the popular contents to its serving users. Besides these pros, the mPC also has some limitations, as its performance is highly affected by cross-tier and co-tier interferences. In this article, we analyze the effect of these interferences on mPCs performance. Our results show that the performance of mPC network is equally affected by the capacity of wireless backhaul, sidehaul, and access links. Moreover, since mPCs accommodate data traffic from wireless backhaul, sidehaul links, and content cache, their performance is also affected by the ratio of data-traffic delivered via these links.

Analysis of Cavitation Performance of a 2-D Hydrofoil Based on Mixed-iterative Method

以便学习一只 2-D 水翼船的成穴特征，联合非线性的成穴模型和混合重复的方法被用来预言并且分析水翼船的成穴表演。成穴元素非线性地基于格林公式和不安潜力面板方法被处理。同时，联合洞形状为的方法修理了重复和洞塑造的洞长度(CSCL ) 因为固定成穴数字(CSCN ) 重复被用来得出水翼船成穴的厚度和长度。通过计算结果的分析，成穴什么时候发生在水翼船上，能被结束压力和速度的 jump 潜在地在吸表面上在成穴结束区域和非成穴区域之间存在。在攻击的某些角度，成穴数字在成穴的长度上有否定影响。并且在攻击和成穴的一样的角度下面数，越大水翼船的厚度，越 shorter 成穴长度。

Performance Evaluation of Motor Insurance Companies: Panel Data Evidence from Nigeria

This paper evaluated performance of motor insurance companies in Nigeria. The objectives were to determine the following: 1) significant effects of claims settlements on motor insurance firms’ earned premium;2) differences in managerial/technological capabilities among the companies and 3) effects of policy (or time effect) on insurance firms’ output within the study period. Panel data obtained for this study comprised operational data on premium earned and direct claims settlement by these companies over a period of six (6) years. Using panel data statistical models, we found that direct claims settlement negatively affected insurance companies’ earned premium. Also, significant differences in technological and managerial capabilities were found to exist among the companies, though only one company exhibited this heterogeneity. Besides, there were no policy impacts (or time effect) on vehicle insurance firms’ output in the study period. Policy implications of the results were discussed.

数字化程度对零售业经营绩效影响研究

数字化进程不断深化对零售业经营绩效产生了相应的影响,现有研究大多聚焦于数字化程度对全领域经营绩效的影响,对于零售业单一行业影响的研究较少。选取2014—2021年零售业A股上市公司相关数据,运用回归模型对数字化程度与零售业经营绩效的关系展开实证研究。研究发现,数字化水平的加深提升零售业经营绩效,数字化水平较高的企业在市场销售中也处在有利地位。进一步分区域和不同经营内容探究结果表明:我国西部地区数字化程度对当地零售业经营绩效促进作用最为显著,东部其次;中部地区数字化程度对当地零售业经营绩效产生了负向影响;我国零售业不同经营内容数字化程度对于零售业经营绩效均产生正向影响,其中互联网零售业和珠宝首饰零售业最为显著。

煤炭企业ESG表现、研发投入与企业绩效

ESG作为关注企业环境责任、社会责任和内部治理的综合性评价体系,对企业实现可持续高质量发展具有重要意义。文中选择2011—2021年中国沪深A股煤炭上市企业作为研究样本,通过固定效应模型和中介效应模型实证检验ESG表现对上市煤炭企业绩效的影响,并探究研发投入在ESG表现对煤炭企业绩效的影响中发挥何种作用。研究结果表明,煤炭企业ESG表现对企业绩效具有促进作用,而研发投入在ESG表现对企业绩效的影响过程中发挥部分中介作用,煤炭企业ESG表现通过增加研发投入来促进企业绩效。通过变量缩尾检验、中介效应稳健性检验和内生性检验后依然成立。研究不仅丰富了ESG表现与煤炭企业绩效领域的相关文献,也为煤炭企业进行ESG实践提升企业绩效提供了理论支撑和经验证据。

固定污染源废气颗粒物现场测试关键性能指标校验方法的研究

传统污染源颗粒物监测方法虽保证了质量但耗时过长;而快速检测方法多以间接测量为主,测量信号与质量浓度量的对应关系无法现场进行校核。基于便携式振荡天平法采用标准膜重量直接验证方式解决了设备性能无法现场核查的难题,无需重新建立测量信号与质量浓度量的对应关系。研究表明:在水平振动为56.2~94.4 dB,垂直振动为58.4~96.5 dB条件下,测试前、后振荡天平称量值与标准滤膜定值的相对误差均不大于±3.5%,标准偏差均小于0.5%。该研究为固定污染废气颗粒物的现场快速监测提供了有效的质量保证。

高超声速变外形飞行器建模与固定时间预设性能控制

以一种折叠式高超声速变外形飞行器(Hypersonic morphing vehicle, HMV)为研究对象,综合考虑变形引起的气动特性、动力学特性的动态变化和模型不确定性、外部干扰的影响,开展飞行器建模与固定时间预设性能控制方法研究.首先,建立高超声速变外形飞行器的运动模型和姿态控制模型;然后,采用固定时间干扰观测器实现对模型不确定性和外部干扰构成的复合总扰动的精确估计,并设计一种新型固定时间预设性能函数以定量描述期望性能约束,在此基础上,基于预设性能控制架构并结合动态面控制技术设计预设性能姿态控制器,利用Lyapunov稳定性理论证明闭环系统的固定时间稳定性;最后,通过数值仿真验证所提出方法的有效性和鲁棒性.

基于固定和产出DEA的上市物流运输企业运营绩效评估研究

随着国民经济和电子商务的高速发展,物流运输业已经成为了商业贸易的重要方式和必需手段,评估物流企业的运营绩效对于提升企业的运营管理水平具有积极的作用.以2022年“中国500强”企业中的16家上市物流运输企业作为研究对象,将市场份额看作固定和产出,运用数据包络分析方法中的一般均衡有效前沿面模型(GEEFDEA)计算并分析了这16家企业2022年的运营效率得分与排名.研究结果显示:我国物流业整体表现良好,平均运营绩效达到0.9949.此外,物流运输企业的运营绩效与成本管理水平、盈利能力、企业规模和市场竞争力这四个因素呈显著正相关性.最后,对表现落后的企业提出相应的改进意见.

基坑装配式内支撑高脚螺栓-模袋混凝土固支端及其承载性能

基坑工程内支撑体系中,混凝土支撑因其承载能力高、布置不受限制、端部节点现浇、整体性良好等优势得以在基坑工程中广泛使用,但混凝土支撑在设计与施工中的弊病也十分显著,存在设计截面过大、施工周期长、污染性强、成本高、浪费严重等问题。因而,针对混凝土支撑在基坑工程中表现出的优势与劣势,并结合地铁明挖车站深基坑工程的特点,设计一种装配式组合钢管混凝土内支撑,从提高端部节点刚度和强度、实现端部固定连接等角度出发,提出一种适应于地铁基坑装配式组合钢管混凝土内支撑的高脚螺栓-模袋混凝土固支端。通过阐明固支端的设计方案、构造特点和工作原理,并将其与混凝土支撑现浇节点进行对比分析,论证了由预埋钢板、空心法兰盘、模袋混凝土和高脚螺栓等特殊构件组成的固支端,在支撑体系中发挥了固定支座的作用;为建立固支端设计与验算的理论依据,通过分析固支端的力学机理、破坏模式及其演变规律,得到固支端的抗压与抗弯承载力的解析方法;为验证固支端承载性能的理论解析方法的可行性,结合数值模拟验证分析了理论与数值结果,并对影响固支端承载性能的主要因素进行参数化分析。

商业银行数字化转型对经营绩效影响研究

数字化转型是科技与金融逐步融合发展的重要催化剂,也是商业银行业务经营迭代发展的必然趋势。利用文本挖掘法计算出商业银行数字化发展指数,基于2011—2021年43家上市商业银行的相关财务数据,建立双向固定效应模型和中介效应模型,验证商业银行数字化转型对商业银行经营绩效的影响。研究发现:现阶段商业银行进行数字化转型抑制经营绩效水平提升;数字化转型对不同类型、不同规模、不同性质的商业银行经营绩效的作用效应不尽相同;商业银行进行数字化转型,可通过优化收入结构,进而提高商业银行经营绩效水平。据此,应合理进行数字化转型,更新企业数字化业务,实现企业数字化运营,进一步提高商业银行经营绩效水平。

随机大系统的分散预设固定时间有界H_(∞)控制

针对具有未知非线性函数和不确定外部扰动的随机大系统,设计分散预设固定时间有界H_(∞)控制器.该文控制器能使大系统中各子系统的跟踪误差被预设有限时间性能函数约束,使各子系统的输出较好地跟踪参考信号,确保各子系统的所有信号均依概率固定时间有界稳定.该文控制器具有可行性.

基于概率性分析的混合关键级系统节能调度算法

针对混合关键级系统中的固定优先级任务节能问题,文中提出了基于概率性分析的混合关键级系统节能调度算法。混合关键级系统的实时性要求使得系统建模和分析偏向于较坏的情况。该类系统中出现任务超限的情况相对较少,易存在资源配置过度问题。通过DVFS(Dynamic Voltage Frequency Scaling)技术和混合关键级系统调度算法相结合的方式挖掘空闲时间,从而在保证系统实时性的前提下降低系统的能耗。利用MCSIMU仿真软件对所提算法进行了仿真验证,实验结果表明,对于固定优先级任务与未使用节能调度算法相比,固定优先级节能调度算法的节能率可达45%。

数字化转型对证券公司经营绩效的影响机理研究

基于金融强国建设视角,高质量推进金融机构数字化转型,加快数字金融产品创新和迭代,激活金融服务新功能,是国家赋予金融机构的时代使命。本文基于我国证券公司2017-2021年的全样本面板数据,使用固定效应模型进行系列检验,结果发现:(1)整体而言,证券公司数字化转型能够显著提升经营绩效;(2)机制检验表明,在数字化转型过程中,证券公司通过优化财富管理业务以及强化风险管理能力,进而改善经营绩效;(3)异质性检验表明,非上市证券公司虽然在资产规模、客户体量以及市场地位等方面逊色于上市证券公司,但是这并不影响其对数字化转型的重视程度以及投入力度。研究结论为我国证券公司数字化转型战略实施提供理论依据,有助于其根据自身特点,借助数字技术增强核心竞争力,并不断提升抗风险能力。

对科研事业单位高质量固定资产管理的思考

固定资产管理是科研事业单位的基础性管理工作,但是整体管理水平尚未达到较高质量,管理的流程化、标准化、信息化效能释放不明显。本研究借鉴全面质量管理、六西格玛管理、卓越绩效管理等管理模式理念和思路,提出了高质量固定资产管理的定位与目标,按照卓越绩效管理设计了科研机构高质量固定资产管理的总体框架,给出了科研事业单位实现高质量固定资产管理的实施路径和政策建议,为提升固定资产管理质量提供了指引与支撑。

考虑执行器非线性的固定时间全局预设性能车辆队列控制

针对含有执行器非线性的车辆队列控制系统,提出一种固定时间全局预设性能控制(Global prescribed performance control, GPPC)控制方法.首先,设计一种平滑等效变换,在同一框架下解决死区及饱和问题,同时消除执行器非线性固有拐点问题.其次,构造两个新型性能函数,并基于此提出一种全局预设性能控制算法,实现如下目标:1)保证跟踪误差在固定时间内收敛到预定稳态区域;2)消除初始误差必须已知的限制;3)减小误差的超调量.然后,基于上述等效变换及预设性能控制算法,设计一种固定时间滑模队列容错控制方案,实现固定时间单车稳定及队列稳定.最后,通过MATLAB仿真实验,验证了所提算法的有效性.

基于三角腔体吸收器的小型菲涅尔定焦线聚集系统参数的影响分析

为解决线性菲涅尔太阳能集热器中所存在的余弦损失、吸热器端部损失和辐射能流非均匀分布等以及由此带来的问题,本研究介绍了一种采用三角腔体吸收器的小型菲涅尔定焦线聚集系统,并建立了相应的光学模型.通过使用基于蒙特卡罗光线追迹法的TracePro光学软件和统计分析软件SPSS,对该模型进行数值模拟,研究了三角腔体吸收器参数对系统光学性能的影响.结果表明,系统光学效率因子和腔体吸收器内吸收表面能流密度分布均匀因子受太阳时角的影响最显著,其次是太阳赤纬角和腔体吸收器内吸收表面吸收率.当太阳赤纬角为23°27′、腔体吸收器端部反射镜面反射率为0.85,并且太阳时角在0-60°范围内变化时,腔体吸收器内吸收表面吸收率分别为0.75、0.85和1.00,对应的平均系统光学效率因子分别为0.782、0.814和0.855.该系统的光学性能良好,适宜应用在太阳能中温集热领域.