Tarek Ahmed - Academia.edu (original) (raw)

Papers by Tarek Ahmed

Research paper thumbnail of A Modeltheoretic Solution to a Problem of Tarski

Mathematical Logic Quarterly, 2002

Let 1 < n < ω and β > n. We show that the class Nr n CA β of n-dimensional neat reducts ... more Let 1 < n < ω and β > n. We show that the class Nr n CA β of n-dimensional neat reducts of β-dimensional cylindric algebras is not closed under forming elementary subalgebras. This solves a long-standing open problem of Tarski and his co-authors Andréka, Henkin, Monk and ...

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Research paper thumbnail of On Neat Reducts of Algebras of Logic

Studia Logica - An International Journal for Symbolic Logic, 2001

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Research paper thumbnail of Omitting types for finite variable fragments and complete representations of algebras

Journal of Symbolic Logic, 2008

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Research paper thumbnail of Quasi-Resonant Dual Mode Soft Switching PWM and PDM High-Frequency Inverter with IH Load Resonant Tank

International Journal of Mechanical Sciences, 2005

In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current sof... more In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current soft switching pulse modulation single-ended push pull (SEPP) series load resonant inverter with two auxiliary resonant lossless inductor snubbers is proposed for consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each mode equivalent circuits. The new multi resonant high-frequency inverter can regulate its output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of asymmetrical PWM control scheme. The consumer brand-new IH products using proposed ZCS-PWM series load resonant SEPP high-frequency inverter is evaluated and discussed as compared with conventional high-frequency inverter on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM, the pulse density modulation (PDM) strategy is demonstrated for high frequency multi resonant inverter. Its practical effectiveness is substantially proved from an application point of view

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Research paper thumbnail of Advanced control of PWM converter with variable-speed induction generator

IEEE Transactions on Industry Applications, 2006

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Research paper thumbnail of Series load resonant phase shifted ZVS-PWM high-frequency inverter with a single auxiliary edge resonant AC load side snubber for induction heating super heated steamer

... Laknath Gamage, Tarek Ahmed, Hisayuki Sugimura, Srawouth Chandhaket Mutsuo Nakaoka(Prof.Dr-En... more ... Laknath Gamage, Tarek Ahmed, Hisayuki Sugimura, Srawouth Chandhaket Mutsuo Nakaoka(Prof.Dr-Eng ... invcrtcr with auxiliary passive capasitivc snubbcrs.and active rcsonant AC link load ... 15. Auxiliary rcsonant DC link soft commutation snubbcr assisted high-frcqucncy invcrtcr ...

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Research paper thumbnail of Terminal voltage regulation characteristics by static var compensator for a three-phase self-excited induction generator

IEEE Transactions on Industry Applications, 2004

... and can be represented by [6], [7] (2) where and are, respectively, the torque coefficient an... more ... and can be represented by [6], [7] (2) where and are, respectively, the torque coefficient and the speed coefficient in newton meters. In the experiment, a controllable separately excited dc motor is used with a constant armature voltage and a field current Page 4. ... control. Fig. ...

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Research paper thumbnail of A Novel Induction Generator System for Small-Scale AC and DC Power Applications

Abstract-This paper presents a novel dynamic model in the stationary reference frame for a diode ... more Abstract-This paper presents a novel dynamic model in the stationary reference frame for a diode bridge rectifier with a DC-link filter directly connected to a three-phase induction generator (IG). Moreover, a hybrid excitation system, consisting of a capacitor bank and an active ...

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Research paper thumbnail of Three-phase self-excited induction generator driven by variable-speed prime mover for clean renewable energy utilizations and its terminal voltage regulation characteristics by static VAr compensator

Journal of Electroanalytical Chemistry, 2003

In this paper, the practical impedance approach steady-state analysis in the frequency domain of ... more In this paper, the practical impedance approach steady-state analysis in the frequency domain of the three-phase self-excited induction generator (SEIG) with squirrel cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover (VSPM) such as a wind turbine for the clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate electro-mechanical equivalent circuit and the operating performances of the three-phase SEIG coupled by a VSPM in the steady-state analysis are evaluated and discussed on line under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for the small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreements with those ones obtained from the simulation results. Furthermore, a PI controlled feedback closed-loop voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static VAr compensator (SVC) composed of the thyristor phase controlled reactor (TCR) in parallel with the thyristor switched capacitor (TSC) and the fixed excitation capacitor bank (FC) is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in the steady-state operations in terms of the fast response and the high performances.

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Research paper thumbnail of Dual-mode time-sharing one-stage single-phase power conditioner using sinewave tracked soft switching PWM boost chopper

Gastroenterology, 2005

The paper presents a novel circuit topology of a high efficiency single-phase sinewave power cond... more The paper presents a novel circuit topology of a high efficiency single-phase sinewave power conditioning and processing converter with a DC-link chemical capacitor. This power conditioner, used as a small scale stand-alone new-energy related power generation system, is composed of time-sharing operated sinewave absolute modulation boost chopper with a bypass diode in the first power processing stage and cascaded with a time-sharing sinewave pulse modulated full-bridge inverter as a second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the power processing stage with the time-sharing dual mode sinewave modulation scheme is described with a simple design example. The paper provides and describes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the effectiveness of this novel one stage sinewave power conditioner related to new-energy generation system is reviewed through the experimental results.

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Research paper thumbnail of Static VAr compensator-based voltage regulation implementation of single-phase self-excited induction generator

Energy Procedia, 2004

In this paper, the single-phase static VAR compensator (SVC) is applied to regulate and stabilize... more In this paper, the single-phase static VAR compensator (SVC) is applied to regulate and stabilize smoothly the generated output voltage of the single-phase self-excited induction generator (single-phase SEIG) driven by a variable-speed prime mover (VSPM) under the ...

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Research paper thumbnail of A Modeltheoretic Solution to a Problem of Tarski

Mathematical Logic Quarterly, 2002

Let 1 < n < ω and β > n. We show that the class Nr n CA β of n-dimensional neat reducts ... more Let 1 < n < ω and β > n. We show that the class Nr n CA β of n-dimensional neat reducts of β-dimensional cylindric algebras is not closed under forming elementary subalgebras. This solves a long-standing open problem of Tarski and his co-authors Andréka, Henkin, Monk and ...

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Research paper thumbnail of On Neat Reducts of Algebras of Logic

Studia Logica - An International Journal for Symbolic Logic, 2001

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Research paper thumbnail of Omitting types for finite variable fragments and complete representations of algebras

Journal of Symbolic Logic, 2008

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Research paper thumbnail of Quasi-Resonant Dual Mode Soft Switching PWM and PDM High-Frequency Inverter with IH Load Resonant Tank

International Journal of Mechanical Sciences, 2005

In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current sof... more In this paper, a novel type auxiliary active resonant capacitor snubber assisted zero current soft switching pulse modulation single-ended push pull (SEPP) series load resonant inverter with two auxiliary resonant lossless inductor snubbers is proposed for consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each mode equivalent circuits. The new multi resonant high-frequency inverter can regulate its output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of asymmetrical PWM control scheme. The consumer brand-new IH products using proposed ZCS-PWM series load resonant SEPP high-frequency inverter is evaluated and discussed as compared with conventional high-frequency inverter on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM, the pulse density modulation (PDM) strategy is demonstrated for high frequency multi resonant inverter. Its practical effectiveness is substantially proved from an application point of view

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Research paper thumbnail of Advanced control of PWM converter with variable-speed induction generator

IEEE Transactions on Industry Applications, 2006

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Research paper thumbnail of Series load resonant phase shifted ZVS-PWM high-frequency inverter with a single auxiliary edge resonant AC load side snubber for induction heating super heated steamer

... Laknath Gamage, Tarek Ahmed, Hisayuki Sugimura, Srawouth Chandhaket Mutsuo Nakaoka(Prof.Dr-En... more ... Laknath Gamage, Tarek Ahmed, Hisayuki Sugimura, Srawouth Chandhaket Mutsuo Nakaoka(Prof.Dr-Eng ... invcrtcr with auxiliary passive capasitivc snubbcrs.and active rcsonant AC link load ... 15. Auxiliary rcsonant DC link soft commutation snubbcr assisted high-frcqucncy invcrtcr ...

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Research paper thumbnail of Terminal voltage regulation characteristics by static var compensator for a three-phase self-excited induction generator

IEEE Transactions on Industry Applications, 2004

... and can be represented by [6], [7] (2) where and are, respectively, the torque coefficient an... more ... and can be represented by [6], [7] (2) where and are, respectively, the torque coefficient and the speed coefficient in newton meters. In the experiment, a controllable separately excited dc motor is used with a constant armature voltage and a field current Page 4. ... control. Fig. ...

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Research paper thumbnail of A Novel Induction Generator System for Small-Scale AC and DC Power Applications

Abstract-This paper presents a novel dynamic model in the stationary reference frame for a diode ... more Abstract-This paper presents a novel dynamic model in the stationary reference frame for a diode bridge rectifier with a DC-link filter directly connected to a three-phase induction generator (IG). Moreover, a hybrid excitation system, consisting of a capacitor bank and an active ...

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Research paper thumbnail of Three-phase self-excited induction generator driven by variable-speed prime mover for clean renewable energy utilizations and its terminal voltage regulation characteristics by static VAr compensator

Journal of Electroanalytical Chemistry, 2003

In this paper, the practical impedance approach steady-state analysis in the frequency domain of ... more In this paper, the practical impedance approach steady-state analysis in the frequency domain of the three-phase self-excited induction generator (SEIG) with squirrel cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover (VSPM) such as a wind turbine for the clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate electro-mechanical equivalent circuit and the operating performances of the three-phase SEIG coupled by a VSPM in the steady-state analysis are evaluated and discussed on line under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for the small-scale clean renewable and alternative energy utilizations. The experimental performance results give good agreements with those ones obtained from the simulation results. Furthermore, a PI controlled feedback closed-loop voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static VAr compensator (SVC) composed of the thyristor phase controlled reactor (TCR) in parallel with the thyristor switched capacitor (TSC) and the fixed excitation capacitor bank (FC) is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the PI controller-based feedback loop in the steady-state operations in terms of the fast response and the high performances.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Dual-mode time-sharing one-stage single-phase power conditioner using sinewave tracked soft switching PWM boost chopper

Gastroenterology, 2005

The paper presents a novel circuit topology of a high efficiency single-phase sinewave power cond... more The paper presents a novel circuit topology of a high efficiency single-phase sinewave power conditioning and processing converter with a DC-link chemical capacitor. This power conditioner, used as a small scale stand-alone new-energy related power generation system, is composed of time-sharing operated sinewave absolute modulation boost chopper with a bypass diode in the first power processing stage and cascaded with a time-sharing sinewave pulse modulated full-bridge inverter as a second power processing stage operated by time-sharing dual mode pulse pattern control scheme. The unique operating principle of the power processing stage with the time-sharing dual mode sinewave modulation scheme is described with a simple design example. The paper provides and describes also a sinewave tracking voltage controlled soft switching PWM boost chopper with a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the effectiveness of this novel one stage sinewave power conditioner related to new-energy generation system is reviewed through the experimental results.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Static VAr compensator-based voltage regulation implementation of single-phase self-excited induction generator

Energy Procedia, 2004

In this paper, the single-phase static VAR compensator (SVC) is applied to regulate and stabilize... more In this paper, the single-phase static VAR compensator (SVC) is applied to regulate and stabilize smoothly the generated output voltage of the single-phase self-excited induction generator (single-phase SEIG) driven by a variable-speed prime mover (VSPM) under the ...

Bookmarks Related papers MentionsView impact