Compound control strategy for maximum power point tracking with flexible step-up converters for thin film photovoltaic module applications

Liu, Yuhang,Liu, Xiangxin,Zhang, Jianwei,Zhang, Yufeng,Liu, Guangchen The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.9

This paper proposes a novel maximum power point tracking (MPPT) algorithm for a thin-film photovoltaic (PV) module with a flexible step-up DC-DC converter. To improve the voltage rating for the thin film module, a switch-inductor zero voltage transition (SIZVT) boost converter is proposed. In addition, the proposed methodology uses a multistage variable step size (MVSS) with a power close-loop control strategy (PCLC) for MPPT. The corresponding performances are compared with the classical fixed step size (FSS) algorithm and the conventional variable step size (CVSS) algorithm. Simulation results in MATLAB/Simulink and experimental tests with a 240 W prototype validate the proposed algorithm under a variety of conditions.

Analysis of nonlinear vibration response of a functionally graded truncated conical shell with piezoelectric layers

Yuhang Zhang,Wenguang Liu,Zhipeng Lyu,Chao Liu,Lei Pang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

The nonlinear vibration response of a functionally graded materials (FGMs) truncated conical shell with piezoelectric layers is analyzed. The vibration amplitude is suppressed by the positive and inverse piezoelectric effects. And the bifurcation phenomenon is described to reveal the motion state of the conical shell. Firstly, a truncated conical shell composed of three layers is described. And the effective material properties of the FG layer are defined by the Voigt model and the power law distribution. Next, the electric potentials of piezoelectric layers are defined as cosine distribution along the thickness direction. Meanwhile, the constant gain negative velocity feedback algorithm is used to suppress the vibration amplitude by the electric potential produced by the sensor layer. Thereafter, considering the first-order shear deformation theory and the von Karman nonlinearity, the relationship between the strain and displacement is defined. And the corresponding energy of the conical shell is calculated. After that, the motion equations of the conical shell are derived based on the Hamilton principle. Again, the nonlinear single degree of freedom equation is derived by the Galerkin method and the static condensation method. In the end, the nonlinear vibration response of FGMs truncated conical shell with piezoelectric layers under the external excitation is analyzed via using the harmonic balance method and the Runge-Kutta method. The effects of various parameters, such as ceramic volume fraction exponent, external excitation’s amplitude, control gain and geometric parameters on the nonlinear vibration response of the system are evaluated by case studies. Results indicate that the control gain plays an important role on the suppression of the vibration amplitude. The ceramic volume fraction exponents are not sensitive to the nonlinear vibration response compared with other parameters. The bifurcation behavior is observed under different parameters. The FGMs truncated conical shell with piezoelectric layers has three types of motion state, such as periodic motion, multi-periodic motion, and chaos motion.

Surfactant-free synthesis of CuBr NPs decorated by Pt for glucose and nitrite sensors

Xinmei Liu,Xue Zhou,Chunyang Yang,Wenlong Yang,Gang Liu,Yuhang Li,Guangyu Zhang,Xu Zhao 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.124 No.-

The high cost and narrow detection range of electrocatalyst are the two major challenges for the electrochemicalbiosensors. This work provided a surfactant-free synthesis of CuBr@Pt nanoparticles (CuBr@PtNPs) with controllable Pt loading rates. The introduction of chloroplatinic acid (H2PtCl6) and an elevatedsynthesis temperature resulted in a high surface area for CuBr@Pt NPs. The abundant active sites enabledthe CuBr@Pt NPs a superior performance as applied in glucose and nitrite detection. Moreover, an optimalPt loading would be conducive to optimize sensor performances of CuBr@Pt NPs. In the glucose detection,the sensor by CuBr@Pt-15% could reach the detection concentration up to 68.0 mM, which was 1.9 timeshigher than that by pure CuBr. And the corresponding sensitivity by CuBr@Pt-15% was calculated to be382.73 lA/mMcm2. In the detection of sodium nitrite, CuBr@Pt-15% also revealed a superior behaviorthan previous work. And the detection concentration (by the linear sweep voltammetry) was form 0 to80.0 mM. This work demonstrated the superior biosensor performance of CuBr@Pt-15%, which offereda promising material for sensor with wider detection range and rationalized cost.

Commutability Assessment of Processed Human Plasma Samples for Normetanephrine and Metanephrine Measurements Based on the Candidate Reference Measurement Procedure

Deng Yuhang,Liu Qingxiang,Liu Zhenni,Zhao Haijian,Zhou Weiyan,Zhang Chuanbao 대한진단검사의학회 2022 Annals of Laboratory Medicine Vol.42 No.5

Background: To identify candidate external quality assessment (EQA) materials for normetanephrine and metanephrine measurements, we assessed the commutability of eight processed human plasma samples. The agreement between routine assays and the candidate reference measurement procedure (cRMP) was also evaluated. Methods: Fifty-three clinical samples and eight processed plasma samples were prepared. The processed samples included pooled and individual plasma samples spiked with pure normetanephrine and metanephrine and non-spiked pooled and individual plasma samples. The clinical and processed samples were subjected to four routine isotope dilution tandem mass spectrometry assays and cRMP. Commutability was assessed based on two approaches recommended by the CLSI and International Federation of Clinical Chemistry (IFCC). Passing–Bablok regression and Bland–Altman analysis were used to evaluate the agreement between the routine assays and cRMP. Results: The commutability results of the CLSI approach were better than those of the IFCC approach. For the CLSI approach, spiked individual plasma samples and spiked high-concentration pooled plasma samples were commutable for all routine assays for both analytes. The non-spiked pooled plasma sample was commutable for two out of four routine assays for metanephrine and three out of four routine assays for normetanephrine. The agreement between the routine assays and the cRMP was satisfactory, except for one routine assay showing significant bias. Conclusions: High-concentration spiked pooled plasma samples and spiked individual plasma samples are candidate EQA materials for normetanephrine and metanephrine measurements.

Trajectory Planning with Collision Avoidance for Multiple Quadrotor UAVs Using DMPC

Yuhang Jiang,Shiqiang Hu,Christopher Damaren,Lingkun Luo,Bing Liu 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.5

Trajectory planning with collision avoidance plays an important role for the safe application of multi-UAV systems in low altitude airspace. Although the synchronous DMPC algorithm had been widely applied in multi-agent systems due to its lower communication and computing cost, it generally suffers from the strict requirements. For example, the additional terminal conditions significantly reduce the maneuverability of the UAV in the fleet, whereas which ensure the stability of the algorithm and the feasibility of recursion. To remedy the raised issues, in this paper, a novel set of terminal conditions is proposed, which effectively reduces the conservativeness of the collision-free trajectories and satisfies the requirements of collision avoidance algorithms simultaneously. In this research, we also leverage the theoretical qualitative analysis, and thus providing initial guesses and related parameter settings for the algorithm. Finally, sufficient numerical simulations are proposed to verify the effectiveness and superiority of the proposed algorithm.

The development model of PT Visionet Internasional (OVO) in Indonesia

Yuhang Xia,Yuming Liu,최명철,Chuijie Meng,김한얼 국제문화기술진흥원 2023 International Journal of Advanced Culture Technolo Vol.11 No.2

OVO is a digital platform that provides simple payments and smart financial services, as well as one of the largest digital payment platforms in Indonesia. It has wide coverage and security when making payments, and supports multiple settlement currencies. The purpose of this study is to explore the history, business model, and future strategic direction of OVO, an Indonesian e-wallet. To date, OVO has built its own mobile payment ecosystem covering a wide range of consumer scenarios including e-commerce, travel, offline shopping and finance. And it supports mobile banking, online banking, debit cards or selected partner merchants. Its three largest transaction categories are in the transportation, retail and e-commerce sectors. With over 110 million consumers and 1.3 million merchant users, it is one of the dominant e-wallets in Indonesian market and has become the country's e-payment market leader. OVO eWallet's ‘One Card’ model offers convenience and choice for users, thus contributing to the rapid growth of OVO eWallet. And OVO eWallet competes fiercely with other competitors, but OVO eWallet continues to grow in terms of the number of users and market share. Finally, this study analyzes the strategic goals and plans of OVO eWallet, predicts its future direction. OVO eWallet has a huge success, but there are still competition and challenges to face.

Direct observation of the hysteretic Fermi level modulation in monolayer MoS2 field effect transistors

Yuhang Wang,Dongyong Li,Xubo Lai,Boyang Liu,Yibao Chen,Fengping Wang,Rongming Wang,Liuwan Zhang 한국물리학회 2020 Current Applied Physics Vol.20 No.2

The hysteresis in the transfer curve of MoS2 has significant impact on the device performance. However, the hysteresis mechanism is still not clear. Here, we investigate the hysteresis of the monolayer MoS2 by probing the local Fermi level variations as a function of the back gate voltage in different atmosphere using the Kelvin probe microscopy. While the Fermi level of the MoS2 in air is much lower than that in vacuum, both the MoS2 devices in vacuum and air show large Fermi level hysteresis. The Fermi level hysteresis direction is clock-wise, identical to that observed in the transfer curves. Both the hysteresis in Fermi level and transfer curve can be explained consistently by taking into account the charge trapping. Our findings confirm that carrier density modulation in MoS2 plays a vital role in the hysteresis, and provide insight into the hysteresis mechanism for the optimization of the device performance.

Significance of considering respiratory movement in estimating sleep stage

Haipeng Liu,Yuhang Xu,Dingchang Zheng 대한의용생체공학회 2020 Biomedical Engineering Letters (BMEL) Vol.10 No.2

We read with great interest the paper “Sleep stage estimationmethods using a camera for home use” by Nochino et al. [ 1 ]. The paper proposed a method of sleep stage (wake, light,deep, and rapid-eye movement (REM)) estimation using anoff -the-shelf camera. Recognizing its potential in providingconvenient daily sleep monitoring for home use, we wouldlike to open a productive discussion concerning the methodologicalerrors and limitations presented in the paper.

Cu nanoplates with ‘‘clean surface”: Synthesis and their enhanced biosensors performance

Xinmei Liu,Chunyang Yang,Wenlong Yang,Jiaqi Lin,Xue Zhou,Yuhang Li 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

In this study, we demonstrated a one-pot synthesis of Cu nanoplates (Cu NPs) with high purity and ‘‘cleansurface”. Different from surfactant-assisted method, we tailored the architecture by controlling the ripeningtime of Cu seeds. Citrate is introduced as a structure-directing agent. Since the ‘‘clean surface” providemore available active sites, the as-prepared Cu NPs show a superior performance when utilized in thenon-enzymatic biosensors. In the detection of nitrite, the sensor constructed by Cu NPs exhibited a superiorsensitivity (303.1 ± 10.18 mAmM1cm2), and the detection range is 5.0 mM. On the contrary, sensitivityfor the Cu NPs by surfactant-assisted method is negligible. As applied in the glucose sensors,detection range by Cu NPs could reach 36.0 mM. And the sensitivity under ambient condition (298 K)is 561.93 ± 3.72 mAmM1cm2, which is ca. 2.11-folds higher than that for Cu NPs by surfactantassistedmethod. In the detection of H2O2, detection range is 10.0 mM, and the enhancement factor fordetection range is up to 2.0-folds. The superior performance can also be extended to the catalysis forthe reduction of 4-nitro-phenol. Since no additional noble metals was applied, this strategy would openup a new avenue for utilizing non-noble metals.

Field-effect transistors using two-dimensional electron gas in ultrathin film heterostructure interface

석태준,Liu yuhang,정해준,김수빈,김대현,김성민,장재혁,조덕용,이상운,박태주 한국표면공학회 2019 한국표면공학회 학술발표회 초록집 Vol.2019 No.5