Grid-based Correlation Localization Method in Mixed Line-of-Sight/Non-Line-of-Sight Environments

( Riming Wang ),( Jiuchao Feng ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.1

Considering the localization estimation issue in mixed line-of-sight (LOS)/non-LOS(NLOS) environments based on received signal strength (RSS) measurements in wireless sensor networks, a grid-based correlation method based on the relationship between distance and RSS is proposed in this paper. The Maximum-Likelihood (ML) estimator is appended to further improve the localization accuracy. Furthermore, in order to reduce computation load and enhance performance, an improved recursively version with NLOS mitigation is also proposed. The most advantages of the proposed localization algorithm is that, it does not need any prior knowledge of the propagation model parameters and therefore does not need any offline calibration effort to calibrate the model parameters in harsh environments, which makes it more convenient for rapid implementation in practical applications. The simulation and experimental results evidence that the proposed localization algorithm exhibits good localization performance and flexibilities for different devices.

Advanced Building Blocks of Power Converters for Renewable Energy Based Distributed Generators

Riming Shao,Mary Kaye,Liuchen Chang 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

The power converter is a critical component of a distributed generation (DG) system, particularly for a renewable energy based distributed generator. With the rapid development and growing applications of DG systems, power converters have evolved from a traditional “power conversion device” to a “system integrator”. This paper outlines the basic and advanced building blocks of power converters for distributed generation systems, with an emphasis on the new algorithms developed especially for grid-connected single-phase power converters in small wind turbines and photovoltaic systems. A grid-connected power converter should feed power of a high quality into a grid with a low total harmonic distortion (THD), and fast dynamic response to the variations of a renewable energy resource. The newly developed space vector based pulse-width-modulation (PWM) with predictive current control provides a direct cycle-by-cycle regulation of the current waveform feeding into the grid. Effective anti-islanding is an essential function of a power converter, in compliance with the grid interconnection requirements. As active islanding detection methods exert disturbances to the grid and passive islanding detection methods generally have large non-detection zones, new and hybrid islanding detection methods have been developed. A power spectral density method has been developed to continuously monitor and identify the possible features of an islanding formation. Maximum power extraction from renewable energy resources is vitally important for distributed generators. Many algorithms have been developed for maximum power point tracking (MPPT) of photovoltaic and wind energy systems. A new MPPT method has been developed by integrating the fast extremum-finding method of Golden Section Search (GSS) into a multi-stage MPPT algorithm. The proposed MPPT algorithm provides fast response (in the order of 40 msec) and high tracking accuracy (99.9%) as compared to the existing algorithms.

Characterization of Energy Conversion of Synechococcus sp. PCC7942 under Photoautotrophic Conditions Based on Metabolic Flux and Chlorophyll Fluorescence Analysis

Riming Yan,Zhibin Zhang,Qinggui Zeng,Du Zhu,Ju Chu 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.3

Energy conversion efficiency of photoautotrophic microalgae plays an important role in the utilization of light energy for cell growth and production of metabolites. To understand the utilization of light energy,Synechococcus sp. PCC7942 was cultivated at different incident light intensities of 15.8, 47.3, and 94.6 μmol/m^2/sec in continuous culture. The influence of light on the carbon and energy metabolism of microalgae was investigated by combining metabolic flux analysis (MFA) and chlorophyll fluorescence analysis (CFA). Results showed that the yields of biomass based on ATP (Y_(ATP)) and total light energy (Y_E) both declined with increasing light, and the maximal values of Y_(ATP) and Y_E were estimated to be 4.73 g/mol-ATP, and 17.10 × 10_(−3) g/kJ respectively, at the examined conditions. The overall efficiency of energy conversion against total absorbed energy changed with the varying irradiances. However, the actual conversion efficiency of total energy based on CFA was almost constant,regardless of the different irradiances used in the present study.

Efficient Solar Cells Based on Light-Harvesting Antimony Sulfoiodide

Nie, Riming,Yun, Hyun-sung,Paik, Min-Jae,Mehta, Aarti,Park, Byung-wook,Choi, Yong Chan,Seok, Sang Il Wiley-VCH 2018 ADVANCED ENERGY MATERIALS Vol.8 No.7

<P> Although antimony sulfoiodide (SbSI) exhibits very interesting properties including high photoconductivity, ferroelectricity, and piezoelectricity, it is not applied to solar cells. Meanwhile, SbSI is predominantly prepared as a powder using a high-temperature, high-pressure system. Herein, the fabrication of solar cells utilizing SbSI as light harvesters is reported for the first time to the best of knowledge. SbSI is prepared by solution processing, followed by annealing under mild temperature conditions by a reaction between antimony trisulfide, which is deposited by chemical bath deposition on a mesoporous TiO<SUB>2</SUB> electrode and antimony triiodide, under air at a low temperature (90 °C) without any external pressure. The solar cells fabricated using SbSI exhibit a power conversion efficiency of 3.05% under standard illumination conditions of 100 mW cm<SUP>-2</SUP>. </P>

Mixed Sulfur and Iodide-Based Lead-Free Perovskite Solar Cells

Nie, Riming,Mehta, Aarti,Park, Byung-wook,Kwon, Hyoung-Woo,Im, Jino,Seok, Sang Il American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.3

<P>The use of divalent chalcogenides and monovalent halides as anions in a perovskite structure allows the introduction of 3<SUP>+</SUP> and 4<SUP>+</SUP> charged cations in the place of the 2<SUP>+</SUP> metal cations. Herein we report for the first time on the fabrication of solar cells exploiting methylammonium antimony sulfur diiodide (MASbSI<SUB>2</SUB>) perovskite structures, as light harvesters. The MASbSI<SUB>2</SUB> was prepared by annealing under mild temperature conditions, via a sequential reaction between antimony trisulfide (Sb<SUB>2</SUB>S<SUB>3</SUB>), which is deposited by the chemical bath deposition (CBD) method, antimony triiodide (SbI<SUB>3</SUB>), and methylammonium iodide (MAI) onto a mesoporous TiO<SUB>2</SUB> electrode, and then annealed at 150 °C in an argon atmosphere. The solar cells fabricated using MASbSI<SUB>2</SUB> exhibited power conversion efficiencies (PCE) of 3.08%, under the standard illumination conditions of 100 mW/cm<SUP>2</SUP>.</P> [FIG OMISSION]</BR>

Predictive current controller and compensator‑based discrete current controller for single‑phase bridge inverters

Jinghua Zhou,Shuang Xu,Riming Shao,Liuchen Chang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.9

Transfer efficiency and power quality are two critical factors when it comes to grid-connected distributed generation systems. Single-phase inverters are commonly used in distributed generation systems under 10 kilowatts as the connection between the gird and renewable energy sources (RESs). In this application, grid current distortion plays a pivotal role in determining inverter performance. In this article, an improved current control strategy based on a predictive current controller (PCC) and a compensator is presented to decrease current harmonic distortion and increase power quality. The controller design method inspects a single-phase inverter system as a digital platform, and designs the controller in discrete time in order to obtain a more precise and effective controller than that in continuous time. The discretization procedures using sampling and hold (S&H) are taken into consideration in the design process. The improved current controller is a DSP-based digital current controller for grid-connected single-phase bridge inverters, whose performance is optimized by considering the time delay caused by analog–digital conversion (ADC) and computations. A comparison has been made to analyze the performance of the single-phase grid-connected inverter system with PCC and ICC. Experimental results are shown to validate the effectiveness of the designed current controller.

Control Strategy for an Electromechanical Transmission Vehicle Based on a Double Markov Process

Liu Hui,Xu Riming,Han Lijin,Xiong Shanshan 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.3

Based on an analysis of the driving demand and system dynamics of heavy-duty vehicles equipped with electromechanical transmission (EMT), a double Markov model is put forward to represent drivers’ power demand for driving and electricity. Transfer probability matrices are calculated by utilizing the maximum likelihood estimation method. A power distribution control strategy based on stochastic dynamic programming (SDP) is proposed. With economy being the optimization goal, the model for power allocation control based on SDP is established while regarding the engine torque, motor speeds, vehicle speed and state of charge (SOC) as state variables’ engine speed and motor torques as control variables’ and power demands as interference variables. The SDP problem is solved by an improved policy iteration algorithm based on value iteration and policy iteration algorithms.

Novel Nonlinear DC-Link Voltage Control for Small-Scale Grid-Connected Wind Power Converters

Guanhong Song,Bo Cao,Liuchen Chang,Riming Shao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

A novel nonlinear observer-based DC-link voltage control algorithm is proposed in this paper for smallscale grid-connected variable-speed wind power converters to minimize the voltage fluctuation across DC-link capacitors caused by wind power variations. The DC-link capacitors, in wind power converters, are normally used to buffer the difference between the input and output power. However, the DC-link voltage varies significantly under rapidly changing working conditions. Hence, a proper DC-link voltage controller is essential to regulate the DC-link voltage in order to minimize these fluctuations. The proposed algorithm estimates the power fed into the converter system using a nonlinear observer integrated with a PI controller, combining the advantages of fast dynamic response capability offered by the proposed observer and control robustness from the PI controller without any additional measurement components. The effectiveness of the proposed control algorithm is verified by both simulation and experimental results.

Nanochannel-Assisted Perovskite Nanowires: From Growth Mechanisms to Photodetector Applications

Zhou, Qitao,Park, Jun Gyu,Nie, Riming,Thokchom, Ashish Kumar,Ha, Dogyeong,Pan, Jing,Seok, Sang Il,Kim, Taesung American Chemical Society 2018 ACS NANO Vol.12 No.8

<P>Growing interest in hybrid organic-inorganic lead halide perovskites has led to the development of various perovskite nanowires (NWs), which have potential use in a wide range of applications, including lasers, photodetectors, and light-emitting diodes (LEDs). However, existing nanofabrication approaches lack the ability to control the number, location, orientation, and properties of perovskite NWs. Their growth mechanism also remains elusive. Here, we demonstrate a micro/nanofluidic fabrication technique (MNFFT) enabling both precise control and <I>in situ</I> monitoring of the growth of perovskite NWs. The initial nucleation point and subsequent growth path of a methylammonium lead iodide-dimethylformamide (MAPbI<SUB>3</SUB>·DMF) NW array can be guided by a nanochannel. <I>In situ</I> UV-vis absorption spectra are measured in real time, permitting the study of the growth mechanism of the DMF-mediated crystallization of MAPbI<SUB>3</SUB>. As an example of an application of the MNFFT, we demonstrate a highly sensitive MAPbI<SUB>3</SUB>-NW-based photodetector on both solid and flexible substrates, showing the potential of the MNFFT for low-cost, large-scale, highly efficient, and flexible optoelectronic applications.</P> [FIG OMISSION]</BR>

Identification and heterologous reconstitution of a 5-alk(en)ylresorcinol synthase from endophytic fungus Shiraia sp. Slf14

Huiwen Yan,Lei Sun,Jinge Huang,Yixing Qiu,Fuchao Xu,Riming Yan,Du Zhu,Wei Wang,Jixun Zhan 한국미생물학회 2018 The journal of microbiology Vol.56 No.11

A new type III polyketide synthase gene (Ssars) was discovered from the genome of Shiraia sp. Slf14, an endophytic fungal strain from Huperzia serrata. The intron-free gene was cloned from the cDNA and ligated to two expression vectors pET28a and YEpADH2p-URA3 for expression in Escherichia coli BL21(DE3) and Saccharomyces cerevisiae BJ5464, respectively. SsARS was efficiently expressed in E. coli BL21(DE3), leading to the synthesis of a series of polyketide products. Six major products were isolated from the engineered E. coli and characterized as 1,3-dihydroxyphenyl- 5-undecane, 1,3-dihydroxyphenyl-5-cis-6 -tridecene,1,3-dihydroxyphenyl- 5-tridecane, 1,3-dihydroxyphenyl-5-cis-8 - pentadecene, 1,3-dihydroxyphenyl-5-pentadecane, and 1,3- dihydroxyphenyl-5-cis-10 -heptadecene, respectively, based on the spectral data and biosynthetic origin. Expression of SsARS in the yeast also led to the synthesis of the same polyketide products, indicating that this enzyme can be reconstituted in both heterologous hosts. Supplementation of soybean oil into the culture of E. coli BL21(DE3)/SsARS increased the production titers of 1–6 and led to the synthesis of an additional product, which was identified as 5-(8 Z,11 Z-heptadecadienyl) resorcinol. This work thus allowed the identification of SsARS as a 5-alk(en)ylresorcinol synthase with flexible substrate specificity toward endogenous and exogenous fatty acids. Desired resorcinol derivatives may be synthesized by supplying corresponding fatty acids into the culture medium.