基于多层次互补特征的通用目标检测模型

针对实际场景中多类目标检测问题,该文提出了一种基于多层次特征表示和异质互补描述子的通用目标检测模型。该模型采用基于组件的目标描述思想,提取目标不同层次的互补特征,并将其统一到条件随机场(CRF)框架中。目标中单个组件及其局部特征对应CRF的一元节点,组件之间的几何空间结构特征则体现在节点之间的两两连接关系上。通过引入节点支持向量机(SVM)分类器和边缘拓扑结构学习,极大提高了模型的鉴别能力和灵活性。在UIUC多尺度数据集和PASCAL VOC 2007数据集上测试结果表明,该文模型不仅能有效描述多类复杂目标,还能较好地解决姿态、尺度、光照变化及局部遮挡情况下的目标检测问题。     

基于两种分类标准的目标检测算法综述

随着大数据、算力、深度学习的发展,基于深度学习的目标检测算法成为该领域主流算法,其性能远超传统算法.为了梳理算法发展脉络、跟踪最新研究成果、促进目标检测领域的研究,分别从两阶段/单阶段和an-chor-based/anchor-free两个维度,对这两种不同分类标准下实现矩形框或近似矩形框标注的代表性目标检测算法进行综述,分析了算法流程、特点、演进及其性能,并对其重要改进版本进行了归类分析.最后总结了算法的优缺点、局限性及适用场景,并展望了未来目标检测领域的发展趋势,提出了几个重要的研究方向.     

基于有功指令共享的两级式光伏并网系统低电压穿越控制策略

传统低电压穿越控制下,两级式光伏并网系统的前级和后级变换器控制相互独立。因此前级变换器需要根据直流母线电压波动被动地调整其输出功率,动态响应速度较低。针对这一问题,提出了一种基于有功功率指令共享的两级式光伏并网系统低电压穿越控制策略。该策略可以根据网侧电压降落深度动态调整后级变换器的有功功率指令,同时使光伏阵列根据该有功功率指令主动调整输出功率,保持直流母线电压恒定。通过仿真和实验将所提控制策略与现有的低电压穿越控制策略进行对比分析,结果表明：所提控制策略下光伏阵列的输出电压、电流的波动明显减小,且2台变换器输出功率动态响应加快,验证了所提控制策略的有效性。     

Experimental study on the effects of HP and LP EGR on thermal efficiency and emissions of a two-stage turbocharged diesel engine

An experimental study was performed to compare the effects of high- and low-pressure exhaust gas recirculation loops (HP and LP EGR loops) on thermal efficiency and emissions of a diesel engine. Tests were conducted on a 12-L six-cylinder turbocharged diesel engine under various operating conditions. We found that at a low speed of 1100 r/min, 1 MPa BMEP, the LP EGR loop could achieve higher brake thermal efficiency and lower emissions than the HP EGR. This is because the lower enthalpy available at the turbine inlet of the HP EGR loop increased the fuel/oxygen equivalence ratio. For the HP EGR, the gross indicated thermal efficiency was reduced by 1%, but pumping losses were only reduced by 0.5%, compared to the LP EGR loop. At a higher speed of 1600 r/min, 1 MPa BMEP, the HP EGR loop attained a higher brake thermal efficiency and lower emissions because of the relatively sufficient flow through the turbocharger. For the HP EGR loop, the gross indicated thermal efficiency was only reduced by 0.5% and pumping losses were reduced by 1.5%, compared to the LP EGR loop. Lower fuel consumption and a longer ignition delay made the distribution of fuel/oxygen equivalence ratio more homogeneous, leading to lower emissions. Our data also showed that at the high speed of 1600 r/min, 0.55 MPa BMEP, the brake thermal efficiency of the HP EGR loop first increased, then decreased as the EGR rate increased. Therefore, under all conditions, a reasonable match of both EGR loops could achieve a good balance between fuel consumption and emissions of NO _x and soot.     

Styrene-Butadiene Polytelomers for Pressure-Sensitive Applications

Novel styrene-butadiene polymer latex compositions and their utility for pressure-sensitive and other adhesive applications are described. These compositions, termed polytelomers, are based on the concept of synthesising sequentially a low glass transition temperature, high molecular weight (polymeric) fraction, followed by a high glass transition, low molecular weight (telomeric) fraction, in an attempt to simulate the compounding of elastomeric adhesives. Some of the described compositions can exhibit multiphase morphology, having discrete styrene-rich domains surrounded by butadiene rich phase, both of these phases being embedded in a “honeycomb” carboxyl-rich phase. The compositions were characterized by dynamic mechanical spectroscopy and by electron transmission microscopy, as well as by molecular weight distribution and glass transition temperature range data. Examples of adhesive applications are also given.     

煤泥两段浮选—两段脱水回收工艺在友谊选煤厂的应用

友谊选煤厂采用了煤泥两段分级浮选、两段脱水回收工艺流程,工业性试验数据表明,将煤泥按粒径粗细进行分级后再脱泥降灰,既稳定了精煤产品的灰分,又避免了可燃体的损失,浮选精煤产率达84.80%。     

Control of homogeneous charge compression ignition combustion in a two-cylinder gasoline direct injection engine with negative valve overlap

Homogeneous charge compression ignition (HCCI) has challenges in ignition timing control, combustion rate control, and operating range extension. In this paper, HCCI combustion was studied in a two-cylinder gasoline direct injection (GDI) engine with negative valve overlap (NVO). A two-stage gasoline direct injection strategy combined with negative valve overlap was used to control mixture formation and combustion. The gasoline engine could be operated in HCCI combustion mode at a speed range of 800–2 200 r/min and load, indicated mean effective pressure (IMEP) range of 0.1–0.53 MPa. The engine fuel consumption is below 240 g/(kW⁻¹·h⁻¹), and the NO _x emission is below 4 × 10⁻⁵ without soot emission. The effect of different injection strategies on HCCI combustion was studied. The experimental results indicated that the coefficient of variation of the engine cycle decreased by using NVO with two-stage direct injection; the ignition timing and combustion rate could be controlled; and the operational range of HCCI combustion could be extended. Translated from J Tsinghua Univ (Sci & Tech), 2006, 46(5): 720–723 [译自: 清华大学学报]     

车载燃机移动电源压气机设计

运用一套以“S2流面反问题设计”为核心的离心压气机设计体系,设计了某车载燃机双级离心压气机的低压压气机.通过三维CFD计算对气动设计进行数值模拟,结果表明设计的压气机流动情况良好,拥有较高的效率和稳定的工作范围,符合设计目标要求.     

蛇纹石综合利用的试验研究

通过实验研究了采用硫酸浸出工艺从蛇纹石中浸出硫酸镁盐及活性二氧化硅.采用循环酸浸工艺,不仅降低硫酸消耗、提高镁的利用率,使酸浸废液的排放量降至极少,同时采用常压室温的结晶方法回收酸浸滤液中的硫酸镁,降低了镁回收工序的能耗,酸浸滤饼活性二氧化硅具有较好的反应活性.     

两段脱硫尾部增湿技术在10t/h工业链条炉洁净燃烧中的应用

在对喜得宝集团公司10t／h链条炉进行改造后，加设了输粉系统装置，旨在对两段脱硫尾部增湿技术进行工业应用研究。试验研究结果表明，两段脱硫技术优于其它钙基脱硫方式，它可以在不影响锅炉热效率的正常运行下，较大幅度地提高脱硫效率，从而具有明显的技术优越性；同时利用原有水膜除尘装置，在不增加资金投入的情况下，进一步提高脱硫效率，减少排放烟尘，显示出了明显的经济优势，故两段脱硫技术可以在工业上加以运用推广。图2表3参3