흡착튜브를 이용한 가스상물질 채취용 펌프의 유량성능 평가방법

김남희 ( Nam Hee Kim ),송호준 ( Ho June Song ),김기연 ( Ki Youn Kim ),마혜란 ( Hye Lan Ma4 ),이광용 ( Gwang Yong Yi ),정지연 ( Jee Yeon Jeong ) 한국산업보건학회 2014 한국산업보건학회지 Vol.24 No.2

Objectives: Flow rate stability is very important for obtaining reliable measurements. However there is no easily used method for checking whether the flow rate set at the initial stage is sustained during sampling. The purpose of this study was to develop a method to evaluate the flow rate performance of gas sampling pumps with adsorbents commonly used to sample gases. Materials and methods: We tested the back pressure of gas sampling pumps commonly used in Korea with adsorbents such as charcoal and silica tubes and attempted to discover the combination conditions of adsorbents in accordance with back pressure required by ISO standard 13137. Results: We found the combination of sampling adsorbents to be applicable to the pressure drop required by the ISO standard for evaluating flow rate stability under increasing pressure drop and long term (eight-hour) performance. Conclusions: This evaluation method of using a sampling media matrix for checking flow rate stability as proposed by this study could be a highly useful tool for determining the reliability of the performance pumps before sampling.

Happy Children’s Day

Ma Jia Yi 한국콘텐츠학회 2022 ICCC International Digital Design Invitation Exhib Vol.2022 No.12

Energy Dissipation of Cosmological Shock Waves in the Large Scale Structure

Ma, Ren-Yi,Ryu, Dong-Su,Kang, Hye-Sung 한국우주과학회 2009 한국우주과학회보 Vol.18 No.1

Effect of Thyroid Hormone on the Gene Expression of Myostatin in Rat Skeletal Muscle

Ma, Yi,Chen, Xiaoqiang,Li, Qing,An, Xiaorong,Chen, Yongfu Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.2

Modification of thyroid hormone levels has a profound effect on skeletal muscle differentiation, predominantly through direct regulation involving thyroid hormone receptors. Nevertheless, little is known about the regulation of myostatin gene expression in skeletal muscle due to altered concentrations of thyroid hormone. Thus, the goal of our study was to find out whether altered thyroid states could change the gene expression of myostatin, the most powerful inhibitor of skeletal muscle development. A hyperthyroid state was induced in rats by daily injections of L-thyroxine 20 mg/100 g body weight for 14 days, while a hypothyroid state was induced in another group of rats by administering methimazole (0.04%) in drinking water for 14 days. After a period of 14 days of L-thyroxine treatment we observed a significant increase of myostatin expression both in mRNA and protein level. However, decreased expression of myostatin mRNA and protein were observed in hypothyroid rats. Furthermore, our studies demonstrated that the upregulation of myostatin gene expression might be responsible for the loss of body weight induced by altered thyroid hormone levels. We concluded that myostatin played a role in a metabolic process in muscle that was regulated by thyroid hormone.

Catalytic Combustion of Propionaldehyde over Alumina-Supported Manganese Oxides

Yi Liu,Zhong-Kun Ma,Seong-Gyu Seo 한국냄새환경학회 2011 실내환경 및 냄새 학회지 Vol.10 No.1

In this study, the catalytic combustion of propionaldehyde, which is an Offensive Odorant Substance assigned by the Korean Ministry of Environment (KMOE), over alumina-supported manganese oxide (Mn/Al2 O3) catalysts was investigated. The combustion reaction was carried out in a fixed-bed reactor at the temperature range of 200 ∼340 ℃. Mn/Al2O3 catalysts with Mn loadings ranging from 3.9 to 18.3 wt.% were prepared by impregnation method. The physicochemical characteristics of the catalysts were analyzed by X-Ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and Brunauer-Emmett-Teller (BET). The Mn crystalline phases of the Mn/Al2O3 catalysts were identified as α-Mn2O3 and β-MnO2. Mn oxides were covered on γ-Al2O3 supports with an average diameter of around 1 μm. With the increase of Mn loadings, the BET surface areas, pore volumes and average pore diameters of the Mn/Al2O3 catalysts decreased. The catalytic activities of Mn/Al2O3 catalysts increased as the Mn loading was increased from 3.9 wt.% to 18.3 wt.%. The catalyst with 18.3 wt.% Mn loading was able to achieve 100% propionaldehyde conversion at 260 ℃. For the same temperature, a lower Gas Hourly Space Velocity (GHSV) and a lower propionaldehyde concentration promote the complete combustion of propionaldehyde.

EXTREMUM PROPERTIES OF DUAL L_p-CENTROID BODY AND L_p-JOHN ELLIPSOID

Ma, Tong-Yi Korean Mathematical Society 2012 대한수학회보 Vol.49 No.3

For $0<p{\leq}{\infty}$ and a convex body $K$ in $\mathbb{R}^n$, Lutwak, Yang and Zhang defined the concept of dual $L_p$-centroid body ${\Gamma}_{-p}K$ and $L_p$-John ellipsoid $E_pK$. In this paper, we prove the following two results: (i) For any origin-symmetric convex body $K$, there exist an ellipsoid $E$ and a parallelotope $P$ such that for $1{\leq}p{\leq}2$ and $0<q{\leq}{\infty}$, $E_qE{\supseteq}{\Gamma}_{-p}K{\supseteq}(nc_{n-2,p})^{-\frac{1}{p}}E_qP$ and $V(E)=V(K)=V(P)$; For $2{\leq}p{\leq}{\infty}$ and $0<q{\leq}{\infty}$, $2^{-1}{\omega_n}^{\frac{1}{n}}E_qE{\subseteq}{\Gamma}_{-p}K{\subseteq}{2\omega_n}^{-\frac{1}{n}}(nc_{n-2,p})^{-\frac{1}{p}}E_qP$ and $V(E)=V(K)=V(P)$. (ii) For any convex body $K$ whose John point is at the origin, there exists a simplex $T$ such that for $1{\leq}p{\leq}{\infty}$ and $0<q{\leq}{\infty}$, ${\alpha}n(nc_{n-2,p})^{-\frac{1}{p}}E_qT{\supseteq}{\Gamma}_{-p}K{\supseteq}(nc_{n-2,p})^{-\frac{1}{p}}E_qT$ and $V(K)=V(T)$.

GreenIoT Architecture for Internet of Things Applications

( Yi-wei Ma ),( Jiann-liang Chen ),( Yung-sheng Lee ),( Hsin-yi Chang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.2

A power-saving mechanism for smartphone devices is developed by analyzing the features of data that are received from Internet of Things (IoT) sensors devices to optimize the data processing policies. In the proposed GreenIoT architecture for power-saving in IoT, the power saving and feedback mechanism are implemented in the IoT middleware. When the GreenIoT application in the power-saving IoT architecture is launched, IoT devices collect the sensor data and send them to the middleware. After the scanning module in the IoT middleware has received the data, the data are analyzed by a feature evaluation module and a threshold analysis module. Based on the analytical results, the policy decision module processes the data in the device or in the cloud computing environment. The feedback mechanism then records the power consumed and, based on the history of these records, dynamically adjusts the threshold value to increase accuracy. Two smart living applications, a biomedical application and a smart building application, are proposed. Comparisons of data processed in the cloud computing environment show that the power-saving mechanism with IoT architecture reduces the power consumed by these applications by 24% and 9.2%.

Instability Prediction of Valve Motion and Internal Flow in Novel Large-scale Reciprocating Pump

Yi Ma,Yutao Chen,He Zhang,Huashuai Luo,Hongying Deng 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.1

To study the transient valve motions and flow pulsation of novel five-cylinder double-acting reciprocating pump, the theoretical analysis and computational fluid dynamics (CFD) method are employed to investigate the full-cycle working process of the pump. The theoretical models describing the motions and flow rates of hydraulic end are established for reciprocating pump under the actions of piston and valves. The open-close behavior of suction and discharge valves, internal turbulent flow and pulsation characteristics of the pump are studied and the effects of crank speed on those are analyzed in detail. The results show that the valves of reciprocating pump open and close quickly and non-linearly with various degrees of striking velocities and lag phenomena. Through the time and frequency domain results of flow pulsation, the single-cavity frequency is the dominant frequency. The most obvious amplitude appears for discharge flow pulsation, which gradually increases with crank speed. The results could provide useful information for the optimization of reciprocating pumping systems.

Robust Control for Spacecraft Rendezvous with Disturbances and Input Saturation

Yi-Ke Ma,Haibo Ji 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.2

This paper deals with the stabilization problem of spacecraft rendezvous in the presence of disturbances and input saturation. A dead zone operator based model is used to describe the saturation phenomenon. By using Lyapunov method, two groups of control laws are obtained, which ensure the input-to-state stability and the input-to-state practical stability of the closed-loop systems respect to disturbance acceleration, respectively. Simulation results are provided to illustrate the effectiveness of the proposed approaches.

A 3D triple-deck photoanode with a strengthened structure integrality: enhanced photoelectrochemical water oxidation

Ma, M.,Shi, X.,Zhang, K.,Kwon, S.,Li, P.,Kim, J.,Phu, T.,Yi, G. R.,Park, J. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.6

<P>4 WO3/BiVO4 is one of the attractive Type II heterojunctions for photoelectrochemical (PEC) water splitting due to its well-matched band edge positions and visible light harvesting abilities. However, two light absorption components generally suffer from poor charge collection and cannot be efficiently utilized because of non-ideal interfaces. Herein, a triple-deck three-dimensional (3D) architecture was designed through a one-step shaping process with an additional stress relaxation WO3 underlayer. The final photoanodes showed a promising photocurrent density of 5.1 mA cm(-2) at 1.23 V vs. RHE under AM 1.5G illumination. Using the uniformly distributed oxygen evolution co-catalyst (OEC) layer as the outer most shell of the WO3/BiVO4/OEC triple-deck 3D structure with a dense WO3 underlayer, the water splitting efficiency was improved dramatically by facilitating the charge transfer process at the electrode/electrolyte interface.</P>