Analysis of the fluid-solid-thermal coupling of a pressurizer surge line under ocean conditions

Yu Hang,Zhao Xinwen,Fu Shengwei,Zhu Kang 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

To investigate the effects of ocean conditions on the thermal stress and deformation caused by thermal stratification of a pressurizer surge line in a floating nuclear power plant (FNPP), the finite element simulation platform ANSYS Workbench is utilized to conduct the fluid-solid-thermal coupling transient analysis of the surge line under normal “wave-out” condition (no motion) and under ocean conditions (rolling and pitching), generating the transient response characteristics of temperature distribution, thermal stress and thermal deformation inside the surge line. By comparing the calculated results for the three motion conditions, it is found that ocean conditions can significantly improve the thermal stratification phenomenon within the surge line, but may also result in periodic oscillations in the temperature, thermal stress, and thermal deformation of the surge line. Parts of the surge line that are more susceptible to thermal fatigue damage or failure are determined. According to calculation results, the improvements are recommended for pipeline structure to reduce the effects of thermal oscillation caused by ocean conditions. The analysis method used in this study is beneficial for designing and optimizing the pipeline structure of a floating nuclear power plant, as well as for increasing its safety.

Preparation and Characterization of Piroxicam/Poloxamer Solid Dispersion Prepared by Melting Method and Solvent Method

Yu, Hang,Chun, Myung-Kwan,Choi, Hoo-Kyun The Korean Society of Pharmaceutical Sciences and 2007 Journal of Pharmaceutical Investigation Vol.37 No.1

Solid dispersions of piroxicam were prepared by melting method using poloxamer as a carrier. The results of DSC and XRD studies showed that the amorphous farm of piroxicam coexisted with the crystalline form in the solid dispersions. However, the ratio of crystalline form of piroxicam in the solid dispersion prepared by melting method decreased in comparison with the same ratio of the solid dispersion prepared by solvent method. As the ratio of poloxamer in the solid dispersion increased, the ratio of the amorphous form of piroxicam in the solid dispersion increased. The dissolution rate of piroxicam from the solid dispersions was significantly higher than that from piroxicam powder. In comparison to the solid dispersion prepared by solvent method, the dissolution rate of piroxicam from the solid dispersion prepared by melting method was higher. As the ratio of poloxamer in the solid dispersion prepared by melting method increased, the initial dissolution rate decreased, however, the total amount dissolved at the end of the study increased.

Enhancement of solubility and dissolution rate of baicalein, wogonin and oroxylin A extracted from <i>Radix scutellariae</i>

Yu, Hang,Chang, Jae-Sang,Kim, Sun Young,Kim, Yoon G.,Choi, Hoo-Kyun Elsevier/North Holland 2017 International journal of pharmaceutics Vol.528 No.1

<P><B>Abstract</B></P> <P>Baicalein, wogonin, and oroxylin A are three major hydrophobic components in the extract of <I>Radix scutellariae</I> with wide spectrum of pharmacological applications. The purpose of this study was to enhance the solubility, dissolution rate and stability of baicalein, wogonin and oroxylin A by solid dispersion (SD) technique. SD of the extract with various polymers was prepared to select the best carrier. Solubility study, chemical stability study and dissolution study were performed to characterize the SD. The solubility of all three components, after forming solid dispersion with povidone K-30 (PVP K-30) was significantly increased in pH 6.8 medium at room temperature. Stability study conducted for 80days elucidated that the SD in powder state was fairly stable without the aid of Vitamin C (VC). VC was required as antioxidant to impart stability to baicalein in aqueous medium. The dissolution test of the SD of three components, admixed with VC at the weight ratio of 1:6 (<I>Radix scutellariae</I> extract: VC, w/w) exhibited faster dissolution rate with 100% release of all components. Pharmacokinetic study of baicalein solid dispersion revealed that AUC and C<SUB>max</SUB> significantly increased by solid dispersion preparation. Thus, the current developed method, being simple, economical and effective, can be useful for the production of soluble dosage forms of the extract of <I>Radix scutellariae</I> in commercial scale.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fault Tolerant Time Optimization of Switched Systems with Application to Multi-agent Flight Control

Yuhang Xu,Hao Yang,Bin Jiang 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.2

This paper considers the problem of determining optimal switching time for the switched system inthe presence of switching faults, which may result in the deviation of the prescribed switching time from normal. A passive fault-tolerant scheme, which relies on the min-max strategy containing gradient descent algorithm, isproposed to guarantee that the faulty switched system has the minimal upper bound of the cost function. In thecase that the switching faults take place regularly, an active fault-tolerant scheme is further developed which candecrease the minimal upper bound of the cost function, and thus reduce the conservativeness of the passive one. These two new schemes are applied to resolve the route conflict among multi-airplanes in multi-agent flight controlto illustrate their efficiency and applicability.

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.

PMN-PT Single Crystal for Endoscopic Ultrasound 2D Array Application

Yuhang Zhu,Huageng Liang,Benpeng Zhu,Dan Zhou,Xiaofei Yang 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.2

Based on lead magnesium niobate-lead titanate single crystal, a 24 × 24row-column addressing endoscopic two-dimensional array has beensuccessfully fabricated using novel flanged electrodes and “semi-kerf”technologies. Each row/column array element was measured to have anelectromechanical coupling coefficient of 0.81, a center frequency of5MHz, and a fractional bandwidth of approximately 88% at −6 dB. Ofparticular significance was that the lead magnesium niobate-lead titanateelement exhibits much higher sensitivity compared with lead zirconatetitanate-based 2D arrays with similar operational frequency and elementarea. According to the Field II simulated results, although the obtainedbeamwidth at −6 dB was a little inferior to that of the fully sampled 24 × 24two-dimensional array, it is believed that the beamwidth can be improved byappropriately increasing the element number. These results demonstratedthat the lead magnesium niobate-lead titanate single-crystal 2D array is apromising candidate for real-time three-dimensional endoscopic ultrasoundimaging.

Study of Bidirectional DC-DC Converter Interfacing Energy Storage for Vehicle Power Management Using Real Time Digital Simulator (RTDS)

Yuhang Deng,Simon Y. Foo,Hui Li 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4

The bidirectional dc-dc converter, being the interface between Energy Storage Element (ESE) and DC bus, is an essential component of the power management system for vehicle applications including electric vehicle (EV), hybrid electric vehicle (HEV), and fuel cell vehicle (FCV). In this paper, a novel multiphase bidirectional dc-dc converter interfacing with battery to supply and absorb the electric energy in the FCV system was studied with the help of real time digital simulator (RTDS). The mathematical models of fuel cell, battery and dc-dc converter were derived. A power management strategy was developed and first simulated in RTDS. A Power Hardware-In-the-Loop (PHIL) simulation using RTDS is then presented. The main challenge of this PHIL is the requirement for a highly dynamic bidirectional Simulation-Stimulation (Sim-Stim) interface. This paper describes three different interface algorithms. The closed-loop stability of the resulting PHIL system is analyzed in terms of time delay and sampling rate. A prototype bidirectional Sim-Stim interface is designed to implement the PHIL simulation.

A nondestructive method for controlling wind loads and wind-induced responses of wooden pagoda

Yuhang LI,Yang Deng,Ai-Qun Li 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.6

High-rise wooden pagodas generate large displacement responses under wind action. It is necessary and wise to reduce the wind loads and wind-induced responses on the architectural heritage using artificial plants, which do not damage ancient architecture and increase greenery. This study calculates and analyzes the wind loads and wind-induced responses on the Yingxian Wooden Pagoda, in China, using artificial plants via the finite element analysis (FEA). A three-dimensional windloading field was simulated using a wind tunnel test. Wind loads and wind-induced responses, including the displacement and acceleration of the pagoda with and without artificial plants, were analyzed. In addition, three types of tree arrangements were discussed and analyzed using the score method. The results revealed that artificial plants can effectively control wind loads and wind-induced displacements, but the wind-induced accelerations are enlarged to some extent during the process. The height of the tree significantly affected the shelter effects of the structure. The distance of trees from the pagoda and arrangement width of the tree had less influence on shelter effects. This study extends the understanding of the nondestructive method based on artificial plants, for controlling the wind base loads and structural responses of wooden pagodas and preserving architectural heritage via FEA.

Customer Voice at Starbucks: An SVM-based Sentiment Analysis Perspective

( Yuhang Wu ),( Wenqi Li ) 한국감성과학회 2023 한국감성과학회 국제학술대회(ICES) Vol.2023 No.-

This study presents a comprehensive sentiment analysis of customer reviews pertaining to Starbucks, employing the Support Vector Machine (SVM) model. Our findings underscore the model's notable proficiency in discerning negative feedback, thus functioning as a vital tool for enterprises to comprehend customer sentiments in real-time. The insights gleaned from our research extend beyond Starbucks, offering valuable insights for diverse businesses aiming to leverage customer feedback for service enhancement and strategic decision-making. Looking ahead, the potential integration of deep learning techniques holds promising prospects for further enhancing sentiment analysis capabilities.

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.