다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

Technical feasibility study on a standalone hybrid solar-wind system with pumped hydro storage for a remote island in Hong Kong

Quantifying hourly suspended sediment load using data mining models: Case study of a glacierized Andean catchment in Chile

In this paper, a new cascaded nonlinear controller has been designed and implemented on the packed U-cell (PUC) seven-level inverter. The proposed controller has been designed based on a simplified model of PUC inverter and consists of a voltage controller as an outer loop and a current controller as an inner loop. The outer loop regulates the PUC inverter capacitor voltage as the second dc bus. The inner loop is in charge of controlling the flowing current, which is also used to charge and discharge that capacitor. The main goal of the whole system is to keep the dc capacitor voltage at a certain level results in generating a smooth and quasi-sine-wave seven-level voltage waveform at the output of the inverter with low switching frequency. The proposed controller performance is verified through experimental tests. Practical results prove the good dynamic performance of the controller in fixing the PUC capacitor voltage for various and variable load conditions and yet generating low-harmonic seven-level voltage waveform to deliver power to the loads. Operation as an uninterruptible power supply (UPS) or ac loads interface for photovoltaic energy conversion applications is targeted.

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Real-Time Implementation of a Seven-Level Packed U-Cell Inverter with a Low-Switching-Frequency Voltage Regulator

A new single-phase power factor corrector (PFC) based on the Sheppard-Taylor topology is studied. Compared with conventional PFCs, this topology facilitates a better input current tracking, lower voltage stresses across the devices and larger output voltage range for the same operating area. The converter is integrated as a PFC at the DC-end of a single-phase diode bridge. Pulse-width-modulated (PWM) multi-loops control schemes are proposed and developed in order to ensure a unity power factor at the AC-source side and a regulated voltage at the DC-load side. The first control method uses the simple and robust hysteretic-based controller; the second employs a conventional PI regulator; and the third is based on the model nonlinearity compensation approach. The design of the last two control methods is based on the knowledge of a mathematical model that would accurately represent the converter. This model is developed in this paper using the state-space averaging technique, and then the small-signal transfer functions of the converter are derived for linear control design purpose. The performance of the different control strategies is evaluated through simulation experiments carried out on a numerical version of the converter. The implemented model of the converter is obtained by using the switching function technique. The control system is tested under both rated and disturbed operating conditions. The system performance is evaluated in terms of source current total harmonic distortion (THD), input power factor, DC voltage stabilization, and regulation following load variations.

Design, study, modelling and control of a new single-phase high power factor rectifier based on the single-ended primary inductance converter and the Sheppard-Taylor topology

Capacitor banks are used to compensate the reactive power demand of large commercial and industrial loads. When used to switch capacitor banks mechanical breakers generate large current transients. These transients may cause serious system disturbances, premature wear of the breaker contacts and, possibly, shorten the life of the capacitors. While thyristor switches are not new and industry has successfully used them to obtain transient-free switching of capacitor banks, there are very few papers describing this application. This paper tries to fill the void and presents a comparative study of various three-phase configurations of semiconductor switches intended for low voltage (600 V and less) distribution systems. Simple theoretical analysis enables the calculation of the optimal switching times to minimize transients. These calculations take into account the system impedance and the initial capacitor voltages. >

Minimal transient switching of capacitors

Advance technologies are used to overcome a wide range of deficiencies for driving a powered wheelchair. Tetraplegia is one of the cases where complex and expensive interfaces are used for this issue. One interesting solution for this kind of deficiency consists of using a sip and puff interface. It is a simple and inexpensive method but it has two important limitations that restrict its practical use. The first one is in the reduced degree of freedom. The second one is in the tiring driving process. In order to minimize the driving effort for a given trajectory or for an unknown trajectory, this paper presents an optimal adaptation of the controller parameters. The adaptation could be done statically or dynamically according to the environment requirements. The controller is validated by means of simulations applied to three different cases: 1- the complete pathway is defined, 2- the pathway is divided to sub-paths and 3- the pathway is unknown. The first two cases are processed by means of averaging the pathway parameters and the third one by using a fuzzy controller.

Comparative study on different adaptation approaches concerning a sip and puff controller for a powered wheelchair

ABDULSALAM AO, 2003, P 2 INT C PRINC PRAC, P109; Candelas FA, 2003, INT J ENG EDUC, V19, P363; Chen S.H., 1999, P 1999 IEEE HONG KON, VII, P756; COOPER M, ASCILITE 2002 C P; DELALAMO JA, 2003, LAB WEB, P49; ELHAJJ A, 2004, CIBITIC C MAY BEIR L; FJELDLY TA, 2003, LAB WEB, P1; Henry J, 2003, INT J ENG EDUC, V19, P403; HUA J, 2003, P ASEE NEW ENGL REG; LELEVE A, 2003, ITHET 03 MARR MOROCC; McKee GT, 2003, INT J ENG EDUC, V19, P356; NAGHEDOLFEIZI M, 2002, P 2002 ASEE ANN C EX; Pastor R, 2003, INT J ENG EDUC, V19, P445; Pfleeger S.L., 2001, SOFTWARE ENG THEORY; RODRIGUEZ JA, 1999, INT C ACC LARG EXP P, P483; Serri A, 2003, INT J ENG EDUC, V19, P420; Tan KK, 2003, INT J ENG EDUC, V19, P503; ZIMMER T, 2003, LAB WEB, P89

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Remote lab experiments models: A comparative study

This paper presents a review of the recent advances in matrix converter topologies used with the permanent magnet synchronous generator (PMSG) in wind power generation systems. Dedicated literatures introduce different topologies inspired by the conventional matrix converter. Two-stage matrix converters known as sparse matrix converters are compared to the conventional matrix converter in terms of implementation complexity, cost, power rating and voltage ratio. Single-phase matrix converters topologies are implemented in high power wind applications in two different modular concepts: the reduced matrix concept for offshore wind farms and the multi-modular high power matrix converter. On the other hand, several modulation techniques applied to the matrix converter-PMSG scheme are briefly presented.

Imad Mougharbel

Papers

Design, study, modelling and control of a new single-phase high power factor rectifier based on the single-ended primary inductance converter and the Sheppard-Taylor topology

Minimal transient switching of capacitors

Comparative study on different adaptation approaches concerning a sip and puff controller for a powered wheelchair

Remote lab experiments models: A comparative study

A review of matrix converters applied to PMSG based wind energy conversion systems