Applying TID-PSS to Enhance Dynamic Stability of Multi-Machine Power Systems

Mohammadi, Ramin Shir,Mehdizadeh, Ali,Kalantari, Navid Taghizadegan The Korean Institute of Electrical and Electronic 2017 Transactions on Electrical and Electronic Material Vol.18 No.5

Novel power system stabilizers (PSSs) have been proposed to effectively dampen low frequency oscillations (LFOs) in multi-machine power systems and have attracted increasing research interest in recent years. Due to this attention, recently, fractional order controllers (FOCs) have found new applications in power system stability issues. Here, a tilt-integral-derivative power system stabilizer (TID-PSS) is proposed to enhance the dynamic stability of a multi-machine power system by providing additional damping to the LFOs. The TID is an extended version of the classical proportional-integral-derivative (PID) applying fractional calculus. The design of the proposed three-parameter tunable TID-PSS is systematized as a nonlinear time domain optimization problem in which the tunable parameters are adjusted concurrently using a modified group search optimization (MGSO) algorithm. An integral of the time multiplied squared error (ITSE) performance index is considered as the objective function. The proposed stabilizer is simulated in the MATLAB/SIMULINK environment using the FOMCON toolbox and the dynamic performance is evaluated on a 3-machine 6-bus power system. The TID-PSS is compared with both classical PID-PSS (PID-PSS) and conventional PSS (CPSS) using eigenvalue analysis and time domain simulations. Sensitivity analyses are performed to assess the robustness of the proposed controller against large changes in system loading conditions and parameters. The results indicate that the proposed TID-PSS provides the better dynamic performance and robustness compared with the PID-PSS and CPSS.

Applying TID-PSS to Enhance Dynamic Stability of Multi-Machine Power Systems

Ramin Shir Mohammadi,Ali Mehdizadeh,Navid Taghizadegan Kalantari 한국전기전자재료학회 2017 Transactions on Electrical and Electronic Material Vol.18 No.5

Novel power system stabilizers (PSSs) have been proposed to effectively dampen low frequency oscillations (LFOs) in multi-machine power systems and have attracted increasing research interest in recent years. Due to this attention, recently, fractional order controllers (FOCs) have found new applications in power system stability issues. Here, a tilt-integral-derivative power system stabilizer (TID-PSS) is proposed to enhance the dynamic stability of a multi-machine power system by providing additional damping to the LFOs. The TID is an extended version of the classical proportional-integral-derivative (PID) applying fractional calculus. The design of the proposed three-parameter tunable TID-PSS is systematized as a nonlinear time domain optimization problem in which the tunable parameters are adjusted concurrently using a modified group search optimization (MGSO) algorithm. An integral of the time multiplied squared error (ITSE) performance index is considered as the objective function. The proposed stabilizer is simulated in the MATLAB/SIMULINK environment using the FOMCON toolbox and the dynamic performance is evaluated on a 3-machine 6-bus power system. The TID-PSS is compared with both classical PID-PSS (PID-PSS) and conventional PSS (CPSS) using eigenvalue analysis and time domain simulations. Sensitivity analyses are performed to assess the robustness of the proposed controller against large changes in system loading conditions and parameters. The results indicate that the proposed TID-PSS provides the better dynamic performance and robustness compared with the PID-PSS and CPSS.

Application of fuzzy RES and fuzzy DEMATEL in the rock behavioral systems under uncertainty

Ramin Rafiee,Sadjad Mohammadi,Mohammad Ataei,Reza Khalookakaie 한국자원공학회 2019 Geosystem engineering Vol.22 No.1

Most of the mine design methods, especially in underground mining depend on the rock mechanics and thus, they are based on rock behavioral systems. Existence of uncertainty in the rock physical and mechanical parameters leads this assessment to be impossible. In such situation, the system thinking methods can be useful. The aim of this paper is to apply system thinking-based techniques for assessment of the rock mass cavability in block caving mines. For this purpose, fuzzy rock engineering system (FRES) and the decision-making trial and evaluation laboratory (FDEMATEL) methods are used to investigate caving behavioral system. The interrelationships and structure of the parameters involved in the rock mass cavability were determined by these methods. In addition, the parameters were categorized from causality point of view and ranked due to their importance. Finally, two methods were compared in the studying a complex system like the cavability of rock masses from their advantages and disadvantages point of view. This study shows that such analysis is useful in practice to better understanding rock behavior and its impact on the working space regard to the safety and the productivity.

Is the association of continuous metabolic syndrome risk score with body mass index independent of physical activity? The CASPIAN-III study

Ramin Heshmat,Gita shafiee,Roya Kelishadi,Amir Eslami Shahr Babaki,Mohammad Esmaeil Motlagh,Tahereh Arefirad,Gelayol Ardalan,Asal Ataie-Jafari,Hamid Asayesh,Rasool Mohammadi,Mostafa Qorbani 대한지역사회영양학회 2015 Nutrition Research and Practice Vol.5 No.6

BACKGROUND/OBJECTIVES: Although the association of body mass index (BMI) with metabolic syndrome (MetS) is well documented, there is little knowledge on the independent and joint associations of BMI and physical activity with MetS risk based on a continuous scoring system. This study was designed to explore the effect of physical activity on interactions between excess body weight and continuous metabolic syndrome (cMetS) in a nationwide survey of Iranian children and adolescents. SUBJECTS/METHODS: Data on 5,625 school students between 10 and 18 years of age were analyzed. BMI percentiles, screen time activity (STA), leisure time physical activity (LTPA) levels, and components of cMetS risk score were extracted. Standardized residuals (z-scores) were calculated for MetS components. Linear regression models were used to study the interactions between different combinations of cMetS, LTPA, and BMI percentiles. RESULTS: Overall, 984 (17.5%) subjects were underweight, whereas 501 (8.9%) and 451 (8%) participants were overweight and obese, respectively. All standardized values for cMetS components, except fasting blood glucose level, were directly correlated with BMI percentiles in all models (P-trend < 0.001); these associations were independent of STA and LTPA levels. Linear associations were also observed among LTPA and standardized residuals for blood pressure, high-density lipoprotein, and waist circumference (P-trend < 0.01). CONCLUSIONS: Our findings suggest that BMI percentiles are associated with cMetS risk score independent of LTPA and STA levels.

Is the association of continuous metabolic syndrome risk score with body mass index independent of physical activity? The CASPIAN-III study

Ramin Heshmat,Gita shafiee,Roya Kelishadi,Amir Eslami Shahr Babaki,Mohammad Esmaeil Motlagh,Tahereh Arefirad,Gelayol Ardalan,Asal Ataie-Jafari,Hamid Asayesh,Rasool Mohammadi,Mostafa Qorbani 한국영양학회 2015 Nutrition Research and Practice Vol.9 No.4

BACKGROUND/OBJECTIVES: Although the association of body mass index (BMI) with metabolic syndrome (MetS) is well documented, there is little knowledge on the independent and joint associations of BMI and physical activity with MetS risk based on a continuous scoring system. This study was designed to explore the effect of physical activity on interactions between excess body weight and continuous metabolic syndrome (cMetS) in a nationwide survey of Iranian children and adolescents. SUBJECTS/METHODS: Data on 5,625 school students between 10 and 18 years of age were analyzed. BMI percentiles, screen time activity (STA), leisure time physical activity (LTPA) levels, and components of cMetS risk score were extracted. Standardized residuals (z-scores) were calculated for MetS components. Linear regression models were used to study the interactions between different combinations of cMetS, LTPA, and BMI percentiles. RESULTS: Overall, 984 (17.5%) subjects were underweight, whereas 501 (8.9%) and 451 (8%) participants were overweight and obese, respectively. All standardized values for cMetS components, except fasting blood glucose level, were directly correlated with BMI percentiles in all models (P-trend < 0.001); these associations were independent of STA and LTPA levels. Linear associations were also observed among LTPA and standardized residuals for blood pressure, high-density lipoprotein, and waist circumference (P-trend < 0.01). CONCLUSIONS: Our findings suggest that BMI percentiles are associated with cMetS risk score independent of LTPA and STA levels.

Is the association of continuous metabolic syndrome risk score with body mass index independent of physical activity? The CASPIAN-III study

Heshmat, Ramin,shafiee, Gita,Kelishadi, Roya,Babaki, Amir Eslami Shahr,Motlagh, Mohammad Esmaeil,Arefirad, Tahereh,Ardalan, Gelayol,Ataie-Jafari, Asal,Asayesh, Hamid,Mohammadi, Rasool,Qorbani, Mostafa The Korean Nutrition Society 2015 Nutrition Research and Practice Vol.9 No.4

BACKGROUND/OBJECTIVES: Although the association of body mass index (BMI) with metabolic syndrome (MetS) is well documented, there is little knowledge on the independent and joint associations of BMI and physical activity with MetS risk based on a continuous scoring system. This study was designed to explore the effect of physical activity on interactions between excess body weight and continuous metabolic syndrome (cMetS) in a nationwide survey of Iranian children and adolescents. SUBJECTS/METHODS: Data on 5,625 school students between 10 and 18 years of age were analyzed. BMI percentiles, screen time activity (STA), leisure time physical activity (LTPA) levels, and components of cMetS risk score were extracted. Standardized residuals (z-scores) were calculated for MetS components. Linear regression models were used to study the interactions between different combinations of cMetS, LTPA, and BMI percentiles. RESULTS: Overall, 984 (17.5%) subjects were underweight, whereas 501 (8.9%) and 451 (8%) participants were overweight and obese, respectively. All standardized values for cMetS components, except fasting blood glucose level, were directly correlated with BMI percentiles in all models (P-trend < 0.001); these associations were independent of STA and LTPA levels. Linear associations were also observed among LTPA and standardized residuals for blood pressure, high-density lipoprotein, and waist circumference (P-trend < 0.01). CONCLUSIONS: Our findings suggest that BMI percentiles are associated with cMetS risk score independent of LTPA and STA levels.

Structural redundancy of 3D RC frames under seismic excitations

Ali Massumi,Ramin Mohammadi 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.1

The components of the seismic behavior factor of RC frames are expected to change as structural redundancy increases. Most researches indicate that increasing redundancy is desirable in response to stochastic events such as earthquake loading. The present paper investigated the effect of redundancy on a fixed plan for seismic behavior factor components and the nonlinear behavior of RC frames. The 3D RC moment resistant frames with equal lateral resistance were designed to examine the role of redundancy in earthquake-resistant design and to distinguish it from total overstrength capacity. The seismic behavior factor and dynamic behavior of structures under natural strong ground motions were numerically evaluated as the judging criteria for structural seismic behavior. The results indicate that increasing redundancy alone in a fixed plan cannot be defined as a criterion for improving the structural seismic behavior.

Structural modeling of petroleum fractions based on mixture viscosity and Watson K factor

Mohammad Reza Omidkhah,Abbas Mohammadi,Ramin Karimzadeh,Ali Haghtalab 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.2

Two procedures have been developed for structural modeling of petroleum fractions based on mixture viscosity and Watson K factor. The representative molecules of paraffinic, naphthenic and aromatic hydrocarbons, based upon Ruzicka’s structural model, have been determined for lube-oil cut SAE 10 from Tehran oil refinery. Unlike previous methods, the newly developed procedures do not require time-consuming and costly laboratory data such as true boiling point profile. Good agreement between predictions of the new models and experimental results has been observed. Moreover, the proposed methods take less run-time than previous models due to less experimental and computational complexities. The results indicate that Ruzicka’s procedure, based on vapor pressure, is only applicable for light hydrocarbon mixtures, while the new methods can be applied for structural modeling of a wide range of petroleum fractions. Furthermore, as a result of this study, the application of a vapor pressure constraint leads to a higher degree of accuracy than the earlier suggested constraint, partial pressure, by Ruzicka.

Analysis of Resistance to Macrolide–Lincosamide–Streptogramin B Among mecA-Positive Staphylococcus Aureus Isolates

Mahmoud Khodabandeh,Ramazan Rajabnia,Mohammad Reza Abdolsalehi,Azadeh Alvandimanesh,Mehrdad Gholami,Mohsen Mohammadi,Abazar Pournajaf,Ramin Kafshgari,Meysam Hasannejad Bibalan 질병관리본부 2019 Osong Public Health and Research Persptectives Vol.10 No.1

Objectives: Genetic determinants conferring resistance to macrolide, lincosamide, and streptogramin B (MLSB) via ribosomal modification such as, erm, msrA/B and ereA/B genes are distributed in bacteria. The main goals of this work were to evaluate the dissemination of MLSB resistance phenotypes and genotypes in methicillin-resistant Staphylococcus aureus (MRSA) isolates collected from clinical samples. Methods: A total of 106 MRSA isolates were studied. Isolates were recovered from 3 hospitals in Tehran between May 2016 to July 2017. The prevalence of MLSB-resistant strains were determined by D-test, and then M-PCR was performed to identify genes encoding resistance to macrolides, lincosamides, and streptogramins in the tested isolates. Results: The frequency of constitutive resistance MLSB, inducible resistance MLSB and MSB resistance were 56.2%, 22.9%, and 16.6%, respectively. Of 11 isolates with the inducible resistance MLSB phenotype, ermC, ermB, ermA and ereA were positive in 81.8%, 63.6%, 54.5% and 18.2% of these isolates, respectively. In isolates with the constitutive resistance MLSB phenotype, the prevalence of ermA, ermB, ermC, msrA, msrB, ereA and ereB were 25.9%, 18.5%, 44.4%, 0.0%, 0.0%, 11.1% and 0.0%, respectively. Conclusion: Clindamycin is commonly administered in severe MRSA infections depending upon the antimicrobial susceptibility findings. This study showed that the D-test should be used as an obligatory method in routine disk diffusion assay to detect inducible clindamycin resistance in MRSA so that effective antibiotic treatment can be provided.