单级并联式高功率因数直流不间断电源

提出了一类单级并联式高功率因数直流不间断电源(uninterruptible power supply, UPS)电路结构与拓扑族。它是由二极管整流桥与具有功率因数校正、不间断供电、快速输出电压调节等功能的并联式变换器构成。也可以看成是由主直流变换器、辅助直流变换器和充电器3个模块构成。以Buck-Boost式拓扑为例,深入分析研究了这类变换器的工作模式、稳态原理特性、控制策略,给出了关键电路参数设计准则。理论分析与试验结果表明,这类变换器具有单级功率变换、对负载真正的在线不间断供电、网侧功率因数高、蓄电池与电网高频电气隔离、输出电压调节速度快、不需故障检测及模式转换电路、体积重量小、成本低等优点。     

一种原边控制恒流LED驱动电路设计

提出了一种应用于LED照明的原边控制电路,通过控制变压器初级峰值电流与tDIS/TS(占空比)的乘积为一个常数,从而实现平均输出电流恒流;通过检测电压谷底来开启原边功率管,大大减小了导通开关损耗。仿真结果表明,该电路成功实现了平均输出电流的恒流控制,效率为93.3%,说明驱动反激变换器工作在准谐振模式有较高的转换效率。     

单级PFC反激式LED电源的研究与设计

针对目前LED驱动电源功率因数不高和效率低等问题,设计了一款单级PFC反激式LED恒流驱动电源,其输出功率为40 W。电源采用临界导通模式的AP1661作为主控芯片,在单级结构上既实现了功率因数的校正,又实现了DC/DC级的降压、高低压的电气隔离,并为LED提供了恒定的电流,保证了LED稳定发光。分析了临界导通模式的单级PFC反激式的特殊电路结构特性,设计了恒流限压反馈回路,满足了LED恒流的特殊要求。实验测试结果表明,该电源功率因数高于0.92,效率在0.87以上,在满足功率因数要求的同时实现了高效率和低成本,符合LED驱动电源发展的趋势。     

一种单级PFC半桥变换器的研究

文章讨论了一种带有ZVZCS的单级PFC半桥变换器。通过合适的参数选择,这种变换器可以软开关方式高效率地工作,同时保持简单的拓扑结构。详细分析了这种变换器的工作原理,并给出了相关设计参数。通过Matlab仿真实验,验证了该变换器工作原理的正确性。     

SSHT Process-a Low Cost Solution for Low Sulfur and Low Aromatics Diesel

The need for cleaner fuels has resulted in a continuing worldwide trend to reduce diesel sulfur and aromatics. There are many approaches to reducing sulfur and aromatics in diesel. Most of them have a common drawback of high cost because of adopting two stages of hydrotreating and using noble-metal catalyst, especially for reducing aromatics. The attempt to resolve this issue has led to the recent development of the Single Stage Hydrotreating (SSHT) process by Research Institute of Petroleum Processing (RIPP), SINOPEC.The SSHT process is a single-stage hydrotreating technology for producing low sulfur and low aromatics diesel. The process uses one or two non-noble-metal catalysts system and operates at moderate pressure. When revamping an existing unit to meet low aromatics diesel specification, the only thing to do is to add a reactor or replace the existing reactor. In pilot plant tests, the SSHT technology has successfully treated SRGO (Straight Run Gas Oil), LCO (Light Cycle Oil) or the blend of them. It is shown that by using the SSHT process diesel with sulfur of 30 ppm and aromatics of 15 m% can be produced from Middle-East SRGO and diesel with aromatics content of 25 m% can be produced from cracked feed, such as FCC-LCO. High diesel yield and cetane number gain (from cracked feed stocks) give the SSHT technology a performance advantage compared to conventional hydrocracking and hydrotreating processes.The lower investment and operating cost is another advantage. The first commercial application of the SSHT technology has been in operation since September 2001.     

采用卷积核金字塔和空洞卷积的单阶段目标检测

目的 在基于深度学习的目标检测模型中,浅层特征图包含更多细节但缺乏语义信息,深层特征图则相反,为了利用不同深度特征图的优势,并在此基础上解决检测目标的多尺度问题,本文提出基于卷积核金字塔和空洞卷积的单阶段目标检测模型。方法 所提模型采用多种方式融合特征信息,先使用逐像素相加方式融合多层不同大小的特征图信息,然后在通道维度拼接不同阶段的特征图,形成具有丰富语义信息和细节信息的信息融合特征层作为模型的预测层。模型在锚框机制中引入卷积核金字塔结构,以解决检测目标的多尺度问题,采用空洞卷积减少大尺寸卷积核增加的参数量,合理地降低锚框数量。结果 实验结果表明,在PASCAL VOC2007测试数据集上,所提检测框架在300×300像素的输入上检测精度达到79.3% mAP（mean average precision）,比SSD（single shot multibox detector）高1.8%,比DSSD（deconvolutional single shot detector）高0.9%。在UCAS-AOD遥感数据测试集上,所提模型的检测精度分别比SSD和DSSD高2.8%和1.9%。在检测速度上,所提模型在Titan X GPU上达到21帧/s,速度超过DSSD。结论 本文模型提出在两个阶段融合特征信息并改进锚框机制,不仅具有较快的检测速度和较高的精度,而且较好地解决了小目标以及重叠目标难以被检出的问题。     

In Vitro and Ectopic In Vivo Studies toward the Utilization of Rapidly Isolated Human Nasal Chondrocytes for Single-Stage Arthroscopic Cartilage Regeneration Therapy

Nasal chondrocytes (NCs) have a higher and more reproducible chondrogenic capacity than articular chondrocytes, and the engineered cartilage tissue they generate in vitro has been demonstrated to be safe in clinical applications. Here, we aimed at determining the feasibility for a single-stage application of NCs for cartilage regeneration under minimally invasive settings. In particular, we assessed whether NCs isolated using a short collagenase digestion protocol retain their potential to proliferate and chondro-differentiate within an injectable, swiftly cross-linked and matrix-metalloproteinase (MMP)-degradable polyethylene glycol (PEG) gel enriched with human platelet lysate (hPL). NC-hPL-PEG gels were additionally tested for their capacity to generate cartilage tissue in vivo and to integrate into cartilage/bone compartments of human osteochondral plugs upon ectopic subcutaneous implantation into nude mice. NCs isolated with a rapid protocol and embedded in PEG gels with hPL at low cell density were capable of efficiently proliferating and of generating tissue rich in glycosaminoglycans and collagen II. NC-hPL-PEG gels developed into hyaline-like cartilage tissues upon ectopic in vivo implantation and integrated with surrounding native cartilage and bone tissues. The delivery of NCs in PEG gels containing hPL is a feasible strategy for cartilage repair and now requires further validation in orthotopic in vivo models.     

双绕组反激式单级PFC变换器及功率因数改善措施研究

为改善功率变换器的功率因数,提出一种双绕组反激式单级功率因数校正PFC(Power Factor Correction)变换拓扑。该拓扑由Boost PFC电路和具有串并联结构的双绕组反激变换电路组合而成,利用2个中间储能电容吸收变压器初级绕组的漏感能量,有效地抑制功率器件的电压应力,提高变换器的可靠性。详细分析了变换器的工作原理和稳态特性,并在传统的单电压环控制方法的基础上,将整流电压引入到控制电路,提出了一种简单的电压补偿控制方法来提高变换器的功率因数、降低输入电流的总谐波畸变率。设计制作了一台150 W/24 V实验样机,实验结果验证了所提出电路原理的正确性和采用电压补偿控制方法改善输入电流波形质量的有效性。     

单级双向反激式高频环节逆变器研究

讨论了一种新颖的基于双向反激拓扑的单级逆变器,并对该电路拓扑的工作原理、控制策略和关键电路参数设计进行了深入的分析。该拓扑由两个完全相同的双向反激变换器构成,两个双向变换器输入并联、输出串联,负载与两个双向变换器的输出端连接,从而组成一种单级逆变器。该逆变器具有单级功率变换、结构简洁、双向功率流和可靠性高等特点。实验充分证实了理论分析的正确性和单级逆变器的可行性。     

单级PFC滤波电容器电容量与输出电压纹波关系

单级功率因数校正是带有功率因数校正的AC/DC变换器中的最简单的一种.在半个工频周期中,文中详尽的分析了单级功率因数校正电路的输出电压的纹波成分与输出电流与输出滤波电容器电容量电容关系;得出了单级功率因数校正需要和大的输出滤波电容器的电容量才能满足常规开关电源对纹波电压的要求的结论,这使得单级功率因数校正的应用受到极大...