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Hasan Komurcugil - One of the best experts on this subject based on the ideXlab platform.
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Super Twisting Algorithm Based Sliding Mode Control Method for Single-Phase Dynamic Voltage Restorers
2019 2nd International Conference on Smart Grid and Renewable Energy (SGRE), 2019Co-Authors: Hasan Komurcugil, Samet Biricik, Ebrahim BabaeiAbstract:This paper presents a super twisting algorithm (STA) based sliding mode control (SMC) method for single-Phase Dynamic voltage restorers (DVRs). The proposed control method eliminates chattering and achieves constant switching frequency. The STA is usually considered as high-order sliding mode (HOSM). The main advantage of HOSM is that its acts on the high-order derivatives of the sliding surface while preserving the inherent advantages of first-order sliding modes and reducing the chattering phenomenon while increasing the accuracy. Hence, the consequence of applying STA in DVR control is that a continuous control input is obtained which can be compared with the triangular carrier signal to produce the pulse width modulation (PWM) signals. The theoretical considerations and analytical results are verified through computer simulations. It is shown that the load voltage is maintained at desired level under voltage sags and voltage swells in the grid.
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Optimized Sliding Mode Control to Maximize Existence Region for Single-Phase Dynamic Voltage Restorers
IEEE Transactions on Industrial Informatics, 2016Co-Authors: Samet Biricik, Hasan KomurcugilAbstract:This paper presents an optimized sliding mode control (SMC) strategy to maximize existence region for single-Phase Dynamic voltage restorers. It is shown analytically that there exists an optimum sliding coefficient which enlarges the existence region of the sliding mode to its maximum. Also, it is pointed out that the optimum sliding coefficient improves the Dynamic response. In addition, a double-band hysteresis control which ensures the switching of a transistor in the voltage source inverter during a half-cycle while it remains either on or off in the other half cycle is used to mitigate the switching frequency. The theoretical considerations and analytical results are verified through computer simulations and experimental results. Simulation and experimental results show that the proposed SMC strategy not only compensates the undesired voltage disturbances and maintains the load voltage at desired level with low total harmonic distortion, but also exhibits fast Dynamic response and operates at reasonably low switching frequency.
Hitoshi Shibuya - One of the best experts on this subject based on the ideXlab platform.
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Differentiation between completely hyalinized uterine leiomyomas and ordinary leiomyomas: three-Phase Dynamic magnetic resonance imaging (MRI) vs. diffusion-weighted MRI with very small b-factors.
Journal of magnetic resonance imaging : JMRI, 2004Co-Authors: Ken Shimada, Isamu Ohashi, Ichiro Kasahara, Hiroshige Watanabe, Sayako Ohta, Naoyuki Miyasaka, Eisaku Itoh, Hitoshi ShibuyaAbstract:Purpose To assess the possibility of differentiating between completely hyalinized leiomyomas and ordinary leiomyomas by using diffusion-weighted (DW) magnetic resonance imaging (MRI) (DWI) employing very small b-factors (b = 1.51 and 55.3 seconds/mm2) in comparison with three-Phase Dynamic MRI. Materials and Methods The subjects were 25 patients with 52 histopathologically confirmed uterine leiomyomas. All leiomyomas were divided into two histopathologic subtypes (5 completely hyalinized leiomyomas and 47 ordinary leiomyomas). For each leiomyoma, the enhancement index (EI) at three-Phase Dynamic MRI and apparent diffusion coefficient (ADC) were obtained and then compared. Results The EIs at second and third Dynamic Phases clearly differentiated the two types of leiomyomas without overlap of values. ADCs also clearly differentiated the two types of leiomyomas without overlap of values. Moreover, there were significant positive correlations between ADCs and EIs at all Dynamic Phases (r = 0.41–0.50, P < 0.01). Conclusion Not only three-Phase Dynamic MRI but also DWI with very small b-factors could be useful for differentiating completely hyalinized leiomyomas from ordinary leiomyomas. J. Magn. Reson. Imaging 2004;20:97–104. © 2004 Wiley-Liss, Inc.
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Triple-Phase Dynamic MRI of Intratumoral Vessel Density and Hyalinization Grade in Uterine Leiomyomas
AJR. American journal of roentgenology, 2004Co-Authors: Ken Shimada, Isamu Ohashi, Ichiro Kasahara, Naoyuki Miyasaka, Hitoshi ShibuyaAbstract:OBJECTIVE. Our purpose was to clarify the relationship between the tissue vascularity shown on triple-Phase Dynamic MRI and the number of intratumoral vessels and degree of hyalinization, which are two histopathologic changes in leiomyoma.SUBJECTS AND METHODS. The subjects were 10 premenopausal patients with 20 leiomyomas who had undergone surgery without preoperative gonadotropin-releasing hormone analogue treatment. Intratumoral vessel density was determined by the mean number of intratumoral vessels with at least one smooth-muscle layer in the optic fields magnified 100 times. Hyalinization grade was determined by the severity of hyalinization, histopathologically classified in three grades. The enhancement index (EI) of the leiomyoma was calculated using the formula EI(t) = [S(t) – S(0)] / S(0), where S(0) is the signal intensity on enhanced T1-weighted images and S(t) is the signal intensity on each Dynamic Phase image (t = 20, 60, and 180 sec). The histopathologic parameters of intratumoral vessel d...
Burkhard Madea - One of the best experts on this subject based on the ideXlab platform.
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Automated headspace solid-Phase Dynamic extraction for the determination of cannabinoids in hair samples.
Forensic science international, 2003Co-Authors: Frank Musshoff, Dirk W Lachenmeier, Lars Kroener, Burkhard MadeaAbstract:This article describes a fully automated procedure for detecting cannabinoids in human hair samples. The procedure uses alkaline hydrolysis and headspace solid-Phase Dynamic extraction (HS-SPDE), followed by on-coating derivatization and gas chromatography-mass spectrometry (GC-MS). SPDE is a further development of solid-Phase microextraction (SPME), based on an inside needle capillary absorption trap. It uses a hollow needle with an internal coating of polydimethylsiloxane as extraction and pre-concentration medium. Ten mg of hair were washed with deionised water, petroleum ether and dichloromethane. After adding deuterated internal standards, the sample was hydrolyzed with sodium hydroxide and directly submitted to HS-SPDE. After absorption of analytes for an on-coating derivatization procedure, the SPDE-needle was directly placed into the headspace of a second vial containing N-methyl-N-trimethylsilyl-trifluoroacetamide before GC-MS analysis. The limit of detection was 0.14 ng/mg for Delta(9)-tetrahydrocannabinol, 0.09 ng/mg for cannabidiol, and 0.12ng/mg for cannabinol. Absolute recoveries were in the range of 0.6 to 8.4%. Linearity was verified over a range from 0.2 to 20 ng/mg, with coefficients of correlation between 0.998 and 0.999. Intra- and inter-day precision were determined at two different concentrations and resulted in ranges between 2.3 and 6.0% (intra-day) and 3.3 and 7.6% (inter-day). Compared with conventional methods of hair analysis, this automated HS-SPDE-GC-MS procedure is substantially faster. It is easy to perform without using solvents and with minimal sample quantities, and it yields the same sensitivity and reproducibility. Compared to SPME, we found a higher extraction rate, coupled with a faster automated operation and greater stability of the device.
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Automated headspace solid-Phase Dynamic extraction for the determination of cannabinoids in hair samples.
Forensic Science International, 2003Co-Authors: Frank Musshoff, Dirk W Lachenmeier, Lars Kroener, Burkhard MadeaAbstract:Abstract This article describes a fully automated procedure for detecting cannabinoids in human hair samples. The procedure uses alkaline hydrolysis and headspace solid-Phase Dynamic extraction (HS-SPDE), followed by on-coating derivatization and gas chromatography–mass spectrometry (GC–MS). SPDE is a further development of solid-Phase microextraction (SPME), based on an inside needle capillary absorption trap. It uses a hollow needle with an internal coating of polydimethylsiloxane as extraction and pre-concentration medium. Ten mg of hair were washed with deionised water, petroleum ether and dichloromethane. After adding deuterated internal standards, the sample was hydrolyzed with sodium hydroxide and directly submitted to HS-SPDE. After absorption of analytes for an on-coating derivatization procedure, the SPDE-needle was directly placed into the headspace of a second vial containing N -methyl- N -trimethylsilyl-trifluoroacetamide before GC–MS analysis. The limit of detection was 0.14 ng/mg for Δ 9 -tetrahydrocannabinol, 0.09 ng/mg for cannabidiol, and 0.12 ng/mg for cannabinol. Absolute recoveries were in the range of 0.6 to 8.4%. Linearity was verified over a range from 0.2 to 20 ng/mg, with coefficients of correlation between 0.998 and 0.999. Intra- and inter-day precision were determined at two different concentrations and resulted in ranges between 2.3 and 6.0% (intra-day) and 3.3 and 7.6% (inter-day). Compared with conventional methods of hair analysis, this automated HS-SPDE–GC–MS procedure is substantially faster. It is easy to perform without using solvents and with minimal sample quantities, and it yields the same sensitivity and reproducibility. Compared to SPME, we found a higher extraction rate, coupled with a faster automated operation and greater stability of the device.
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automated headspace solid Phase Dynamic extraction for the determination of amphetamines and synthetic designer drugs in hair samples
Journal of Chromatography A, 2002Co-Authors: Frank Musshoff, Dirk W Lachenmeier, Lars Kroener, Burkhard MadeaAbstract:Abstract The technique of automated headspace solid-Phase Dynamic extraction (SPDE) coupled with gas chromatography–mass spectrometry was evaluated for the determination of amphetamines and synthetic designer drugs in hair samples. Headspace SPDE is a novel method for the solventless extraction of organic compounds in aqueous samples. In a so-called inside needle capillary absorption trap a hollow needle with an internal coating of polydimethylsiloxane is used as extraction and preconcentration medium. Sampling is performed on the solution headspace by passing the gas through the device actively by a syringe. Analytes present in the sample are sorbed onto the deposited stationary Phase. The syringe needle is placed into the injection port of a GC and rapid heating of the metal needle induces the desorption of analytes. For the determination of amphetamine, methamphetamine, 3,4-methylendioxyamphetamine (MDA), 3,4-methylendioxymethamphetamine, 3,4-methylendioxyethylamphetamine (MDEA), 3,4-methylendioxyphenyl-2-butanamine and N-methyl-1-(3,4-methylendioxyphenyl)-2-butanamine in human hair samples, 10 mg of hair were hydrolysed with sodium hydroxide. After absorption of analytes for an on-coating derivatization procedure the SPDE needle was directly placed into the headspace of a second vial containing N-methyl-bis(trifluoroacetamide). A validation procedure revealed absolute analyte recoveries between 10.2 and 16.7%. Linearity was obtained from 0.1 to 20 ng/mg with coefficients of correlation between 0.992 and 0.999. Intra- and inter-day precision were determined at two different concentrations and resulted in ranges between 1.4 and 4.1% (intra-day) and 4.2–14.6% (inter-day). Limits of detection between 0.03 ng/mg (MDA) and 0.19 ng/mg (MDEA) were achieved. Results indicated that SPDE is a rapid and sensitive method for the analysis of biological samples. Compared to solid-Phase microextraction we found a higher extraction rate coupled with a faster automated operation.
Samet Biricik - One of the best experts on this subject based on the ideXlab platform.
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Super Twisting Algorithm Based Sliding Mode Control Method for Single-Phase Dynamic Voltage Restorers
2019 2nd International Conference on Smart Grid and Renewable Energy (SGRE), 2019Co-Authors: Hasan Komurcugil, Samet Biricik, Ebrahim BabaeiAbstract:This paper presents a super twisting algorithm (STA) based sliding mode control (SMC) method for single-Phase Dynamic voltage restorers (DVRs). The proposed control method eliminates chattering and achieves constant switching frequency. The STA is usually considered as high-order sliding mode (HOSM). The main advantage of HOSM is that its acts on the high-order derivatives of the sliding surface while preserving the inherent advantages of first-order sliding modes and reducing the chattering phenomenon while increasing the accuracy. Hence, the consequence of applying STA in DVR control is that a continuous control input is obtained which can be compared with the triangular carrier signal to produce the pulse width modulation (PWM) signals. The theoretical considerations and analytical results are verified through computer simulations. It is shown that the load voltage is maintained at desired level under voltage sags and voltage swells in the grid.
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Optimized Sliding Mode Control to Maximize Existence Region for Single-Phase Dynamic Voltage Restorers
IEEE Transactions on Industrial Informatics, 2016Co-Authors: Samet Biricik, Hasan KomurcugilAbstract:This paper presents an optimized sliding mode control (SMC) strategy to maximize existence region for single-Phase Dynamic voltage restorers. It is shown analytically that there exists an optimum sliding coefficient which enlarges the existence region of the sliding mode to its maximum. Also, it is pointed out that the optimum sliding coefficient improves the Dynamic response. In addition, a double-band hysteresis control which ensures the switching of a transistor in the voltage source inverter during a half-cycle while it remains either on or off in the other half cycle is used to mitigate the switching frequency. The theoretical considerations and analytical results are verified through computer simulations and experimental results. Simulation and experimental results show that the proposed SMC strategy not only compensates the undesired voltage disturbances and maintains the load voltage at desired level with low total harmonic distortion, but also exhibits fast Dynamic response and operates at reasonably low switching frequency.
Ken Shimada - One of the best experts on this subject based on the ideXlab platform.
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Differentiation between completely hyalinized uterine leiomyomas and ordinary leiomyomas: three-Phase Dynamic magnetic resonance imaging (MRI) vs. diffusion-weighted MRI with very small b-factors.
Journal of magnetic resonance imaging : JMRI, 2004Co-Authors: Ken Shimada, Isamu Ohashi, Ichiro Kasahara, Hiroshige Watanabe, Sayako Ohta, Naoyuki Miyasaka, Eisaku Itoh, Hitoshi ShibuyaAbstract:Purpose To assess the possibility of differentiating between completely hyalinized leiomyomas and ordinary leiomyomas by using diffusion-weighted (DW) magnetic resonance imaging (MRI) (DWI) employing very small b-factors (b = 1.51 and 55.3 seconds/mm2) in comparison with three-Phase Dynamic MRI. Materials and Methods The subjects were 25 patients with 52 histopathologically confirmed uterine leiomyomas. All leiomyomas were divided into two histopathologic subtypes (5 completely hyalinized leiomyomas and 47 ordinary leiomyomas). For each leiomyoma, the enhancement index (EI) at three-Phase Dynamic MRI and apparent diffusion coefficient (ADC) were obtained and then compared. Results The EIs at second and third Dynamic Phases clearly differentiated the two types of leiomyomas without overlap of values. ADCs also clearly differentiated the two types of leiomyomas without overlap of values. Moreover, there were significant positive correlations between ADCs and EIs at all Dynamic Phases (r = 0.41–0.50, P < 0.01). Conclusion Not only three-Phase Dynamic MRI but also DWI with very small b-factors could be useful for differentiating completely hyalinized leiomyomas from ordinary leiomyomas. J. Magn. Reson. Imaging 2004;20:97–104. © 2004 Wiley-Liss, Inc.
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Triple-Phase Dynamic MRI of Intratumoral Vessel Density and Hyalinization Grade in Uterine Leiomyomas
AJR. American journal of roentgenology, 2004Co-Authors: Ken Shimada, Isamu Ohashi, Ichiro Kasahara, Naoyuki Miyasaka, Hitoshi ShibuyaAbstract:OBJECTIVE. Our purpose was to clarify the relationship between the tissue vascularity shown on triple-Phase Dynamic MRI and the number of intratumoral vessels and degree of hyalinization, which are two histopathologic changes in leiomyoma.SUBJECTS AND METHODS. The subjects were 10 premenopausal patients with 20 leiomyomas who had undergone surgery without preoperative gonadotropin-releasing hormone analogue treatment. Intratumoral vessel density was determined by the mean number of intratumoral vessels with at least one smooth-muscle layer in the optic fields magnified 100 times. Hyalinization grade was determined by the severity of hyalinization, histopathologically classified in three grades. The enhancement index (EI) of the leiomyoma was calculated using the formula EI(t) = [S(t) – S(0)] / S(0), where S(0) is the signal intensity on enhanced T1-weighted images and S(t) is the signal intensity on each Dynamic Phase image (t = 20, 60, and 180 sec). The histopathologic parameters of intratumoral vessel d...