A Valley-Fill Single-Stage Electrolytic Capacitorless AC-DC LED Driver

Xiangjie Chen,Weiyin Wang,Hei Wong 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.1

Lighting a long-life light-emitting diode (LED) lamp with the AC mains requires an AC/DC rectifying and regulating circuit where the bulky and short-lifetime electrolytic capacitors become the critical limiting components governing both the system performance and reliability of the light bulb. This work proposes a high-performance LED driver which employs a valley-fill technique for overcoming the low power factor and large ripple issues for circuits without using large-value electrolytic capacitors. Validated with a 15 W LED lamp, it demonstrates that fairly smooth loading current, high power efficiency and high power factor have been achieved. In addition, the single switch topology has reduced the complexity in the controller design of the circuit.

Experiment investigation on flow characteristics of open natural circulation system

Xiangjie Qi,Zichen Zhao,Peng Ai,Peng Chen,Zhongning Sun,Zhaoming Meng 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5

Experimental research on flow characteristics of open natural circulation system was performed, tofigure out the mechanism of the open natural circulation behaviors. The influence factors, such as theheating power, the inlet subcooled and the level of cooling tank on the flow characteristics of the systemwere examined. It was shown that within the scope of the experimental conditions, there are five flowtypes: single-phase stable flow, flash and geyser coexisting unstable flow, flash stable flow, flash unstableflow, and flash and boiling coexisting unstable flow. The geyser flow in flash and geyser coexisting unstable flow is different from classic geysers flow. The flow oscillation period and amplitude of the formerare more regular, is a newly discovered flow pattern. By drawing the flow instability boundary diagramand sorting out the flow types, it is found that the two-phase unstable flow is mainly characterized byboiling and flash, which determine the behavior of open natural circulation respectively or jointly. Moreover, compared with full liquid level system, non-full liquid level system is more prone to boilingphenomenon, and the range of heat flux density and undercooling degree corresponding to unstableflow is larger

Urban Arterial Traffic Two-direction Green Wave Intelligent Coordination Control Technique and Its Application

Xiangjie Kong,Guojiang Shen,Feng Xia,Chuang Lin 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.1

This paper presents a new two-direction green wave intelligent control strategy to solve the coordina-tion control problem of urban arterial traffic. The whole control structure includes two layers - the coordination layer and the control layer. Public cycle time, splits, inbound offset and outbound offset are calculated in the coordination layer. Public cycle time is adjusted by fuzzy neural networks (FNN) according to the traffic flow saturation degree of the key intersection. Splits are calculated based on historical and real-time traffic information. Offsets are calculated by the real-time average speeds. The control layer determines phase composition and adjusts splits at the end of each cycle. The target of this control strategy is to maximize the possibility for vehicles in each direction along the arterial road to pass the local intersection without stop while the utility efficiency of the green signal time is at relatively high level. The actual application results show the proposed method can decrease the average travel time and average number of stops, and increase the average travel speed for vehicles on the arterial road effectively.

1.5 GHz Sigma-delta Fractional-N Ring-based PLL Realized using 40 nm CMOS Technology for SoC Applications

Weiyin Wang,Xiangjie Chen,Hei Wong 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.1

This work presents the design and realization of a 1.5 GHz sigma-delta fractional-N ring-based PLL for SoC applications. The whole system consists of a phase/frequency detector (PFD), charge pump (CP), low-pass filter (LPF), voltage-control oscillator (VCO) and a multi-modulus (MMD) with a variable sigma-delta modulator. Some design optimizations were conducted to improve the performance of each functional block such as PFD, VCO, CP, MMD and so as the whole system. In particular, a time delay circuit is designed for overcoming the blind zone in the PFD; an operational amplifier feedback structure was used to eliminate the current mismatch in the CP, a 3<SUP>rd</SUP> order LPF was used for suppressing noises and a current overdrive structure was used in VCO. The design was realized with a commercial 40 nm CMOS process. The core die sized about 250 m×165 ㎛. Measurements on the fabricated circuit showed various performance improvements over the conventional ones.

Scaling analysis of the pressure suppression containment test facility for the small pressurized water reactor

Liu, Xinxing,Qi, Xiangjie,Zhang, Nan,Meng, Zhaoming,Sun, Zhongning Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.3

The small PWR has been paid more and more attention due to its diversity of application and flexibility in the site selection. However, the large core power density, the small containment space and the rapid accident progress characteristics make it difficult to control the containment pressure like the traditional PWR during the LOCA. The pressure suppression system has been used by the BWR since the early design, which is a suitable technique that can be applied to the small PWR. Since the configuration and operating conditions are different from the BWR, the pressure suppression system should be redesigned for the small PWR. Conducting the experiments on the scale down test facility is a good choice to reproduce the prototypical phenomena in the test facility, which is both economical and reasonable. A systematic scaling method referring to the H2TS method was proposed to determine the geometrical and thermohydraulic parameters of the pressure suppression containment response test facility for the small PWR conceptual design. The containment and the pressure suppression system related thermohydraulic phenomena were analyzed with top-down and bottom-up scaling methods. A set of the scaling criteria were obtained, through which the main parameters of the test facility can be determined.

Overexpression and characterization of a novel cold-adapted and salt-tolerant GH1 β-glucosidase from the marine bacterium Alteromonas sp. L82

Jingjing Sun,Wei Wang,Congyu Yao,Fangqun Dai,Xiangjie Zhu,Junzhong Liu,Jianhua Hao 한국미생물학회 2018 The journal of microbiology Vol.56 No.9

A novel gene (bgl) encoding a cold-adapted β-glucosidase was cloned from the marine bacterium Alteromonas sp. L82. Based on sequence analysis and its putative catalytic conserved region, Bgl belonged to the glycoside hydrolase family 1. Bgl was overexpressed in E. coli and purified by Ni2+ affinity chromatography. The purified recombinant β- glucosidase showed maximum activity at temperatures between 25°C to 45°C and over the pH range 6 to 8. The enzyme lost activity quickly after incubation at 40°C. Therefore, recombinant β-glucosidase appears to be a cold-adapted enzyme. The addition of reducing agent doubled its activity and 2 M NaCl did not influence its activity. Recombinant β-glucosidase was also tolerant of 700 mM glucose and some organic solvents. Bgl had a Km of 0.55 mM, a Vmax of 83.6 U/mg, a kcat of 74.3 s-1 and kcat/Km of 135.1 at 40°C, pH 7 with 4-nitrophenyl-β-D-glucopyranoside as a substrate. These properties indicate Bgl may be an interesting candidate for biotechnological and industrial applications.

PGA: An Efficient Adaptive Traffic Signal Timing Optimization Scheme Using Actor-Critic Reinforcement Learning Algorithm

( Si Shen ),( Guojiang Shen ),( Yang Shen ),( Duanyang Liu ),( Xi Yang ),( Xiangjie Kong ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.11

Advanced traffic signal timing method plays very important role in reducing road congestion and air pollution. Reinforcement learning is considered as superior approach to build traffic light timing scheme by many recent studies. It fulfills real adaptive control by the means of taking real-time traffic information as state, and adjusting traffic light scheme as action. However, existing works behave inefficient in complex intersections and they are lack of feasibility because most of them adopt traffic light scheme whose phase sequence is flexible. To address these issues, a novel adaptive traffic signal timing scheme is proposed. It's based on actor-critic reinforcement learning algorithm, and advanced techniques proximal policy optimization and generalized advantage estimation are integrated. In particular, a new kind of reward function and a simplified form of state representation are carefully defined, and they facilitate to improve the learning efficiency and reduce the computational complexity, respectively. Meanwhile, a fixed phase sequence signal scheme is derived, and constraint on the variations of successive phase durations is introduced, which enhances its feasibility and robustness in field applications. The proposed scheme is verified through field-data-based experiments in both medium and high traffic density scenarios. Simulation results exhibit remarkable improvement in traffic performance as well as the learning efficiency comparing with the existing reinforcement learning-based methods such as 3DQN and DDQN.

Crowd Activity Classification Using Category Constrained Correlated Topic Model

( Xianping Huang ),( Wanliang Wang ),( Guojiang Shen ),( Xiaoqing Feng ),( Xiangjie Kong ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.11

Automatic analysis and understanding of human activities is a challenging task in computer vision, especially for the surveillance scenarios which typically contains crowds, complex motions and occlusions. To address these issues, a Bag-of-words representation of videos is developed by leveraging information including crowd positions, motion directions and velocities. We infer the crowd activity in a motion field using Category Constrained Correlated Topic Model (CC-CTM) with latent topics. We represent each video by a mixture of learned motion patterns, and predict the associated activity by training a SVM classifier. The experiment dataset we constructed are from Crowd_PETS09 bench dataset and UCF_Crowds dataset, including 2000 documents. Experimental results demonstrate that accuracy reaches 90%, and the proposed approach outperforms the state-of-the-arts by a large margin.

Dissimilar Metal Joining of 304 Stainless Steel to SMA490BW Steel Using the Filler Metal Powders with a High-Entropy Design

Dejia Liu,Rui Guo,Yong Hu,Mingxue Shen,Yanchuan Tang,Longzhi Zhao,Deying Li,Xiangjie Wang 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.6

High-entropy alloys having excellent properties are particularly suitable for the application as the filler metals in welding. In the present study, multi-component mixed powders of FeCoCrNiMn and CrFeNi2.4Al0.6,based on a high-entropy design,as well as the comparative 316L stainless steel powders, were used as the filler metals, to achieve the dissimilar weldingbetween 304 stainless steel and SMA490BW steel by laser deposition welding. By comparative analysis of the microstructureand mechanical properties of three types of joints, the feasibility and weld-ability of the filler metal powders based on ahigh-entropy design were studied. It was found that the melting of base metal (BM) and weld metal dilution had an impacton the set high-entropy component in the weld zone. And high-entropy structures were achieved in the weld zone by usingthe powders of CrFeNi2.4Al0.6. Compared to the BM of SMA490BW steel, three types of joints presented a higher notchedtensile strength and had a better corrosion resistance. The joint welded using the powders of CrFeNi2.4Al0.6had the lowesthardness value in the weld zone, in which the joint was fractured during the notched tensile tests. The other two jointsfractured near the notch in the SMA490BW steel side. Transgranular fracture and a typical dimple fracture were observedin the fractured joints.

Genome-wide identification of the valine-glutamine motif containing gene family and the role of VQ25-1 in pollen germination in Brassica oleracea

Yang Miaomiao,Liu Ziwei,Yu Yuanhui,Yang Min,Guo Li,Han Xuejie,Ma Xiangjie,Huang Ziya,Gao Qiguo 한국유전학회 2023 Genes & Genomics Vol.45 No.7

Background The plant-specific valine-glutamine (VQ) motif containing proteins tightly regulate plant growth, development, and stress responses. However, the genome-wide identification and functional analysis of Brassica oleracea (B. oleracea) VQ genes have not been reported. Objective To identify the VQ gene family in B. oleracea and analyze the function of Bo25-1 in pollen germination. Methods The Hidden Markov Model (HMM) of VQ family was used to query the BoVQ genes in the B. oleracea genome. The BoVQ genes preferentially expressed in anthers were screened by qRT-PCR. Subcellular localization of VQ25-1 was observed in Nicotiana benthamiana (N. benthamiana) leaves. To analysis the role of BoVQ25-1 in pollen germination, the expression of BoVQ25-1 was suppressed using antisense-oligonucleotides (AS-ODN). Results A total of 64 BoVQ genes were identified in the B. oleracea genome. BoVQ25-1 was found to be preferentially expressed in the B. oleracea anthers. BoVQ25-1 was cloned from the anthers of the B. oleracea cultivar ‘Fast Cycle’. BoVQ25-1 is localized to the nucleus. The pollen germination rate significantly decreased after AS-ODN treatment. Conclusion Sixty-four BoVQ genes were identified in the B. oleracea genome, of which BoVQ25-1 plays an important role in pollen germination.