COMMUTING POWERS AND EXTERIOR DEGREE OF FINITE GROUPS

Niroomand, Peyman,Rezaei, Rashid,Russo, Francesco G. Korean Mathematical Society 2012 대한수학회지 Vol.49 No.4

Recently, we have introduced a group invariant, which is related to the number of elements $x$ and $y$ of a finite group $G$ such that $x{\wedge}y=1_{G{\wedge}G}$ in the exterior square $G{\wedge}G$ of $G$. This number gives restrictions on the Schur multiplier of $G$ and, consequently, large classes of groups can be described. In the present paper we generalize the previous investigations on the topic, focusing on the number of elements of the form $h^m{\wedge}k$ of $H{\wedge}K$ such that $h^m{\wedge}k=1_{H{\wedge}K}$, where $m{\geq}1$ and $H$ and $K$ are arbitrary subgroups of $G$.

Commuting powers and exterior degree of finite groups

Peyman Niroomand,Rashid Rezaei,Francesco G. Russo 대한수학회 2012 대한수학회지 Vol.49 No.4

Recently, we have introduced a group invariant, which is re-lated to the number of elements x and y of a nite group G such that x ^ y = 1G^G in the exterior square G ^ G of G. This number gives re-strictions on the Schur multiplier of G and, consequently, large classes of groups can be described. In the present paper we generalize the previous investigations on the topic, focusing on the number of elements of the form hm ^ k of H ^ K such that hm ^ k = 1H^K, where m 1 and H and K are arbitrary subgroups of G.

Knowledge, Attitude, and Practice of Iranian Internists Regarding Diabetes: A Cross Sectional Study

Mahtab Niroomand,Seyedeh Najmeh Ghasemi,Hamidreza Karimi-Sari,Mohammad Hossein Khosravi 대한당뇨병학회 2017 Diabetes and Metabolism Journal Vol.41 No.3

Background: A number of studies investigated the general practitioners’ and family physicians’ knowledge, attitude, and practice (KAP) on diabetes. However, studies on internists’ KAP on diabetes management are limited. This study aimed to investigate the Iranian internists’ KAP on diabetes mellitus and its management. Methods: A cross-sectional study was conducted on a random sample of internists who participated in the 26th annual congress of internists in Tehran, Iran. The level of KAP and affecting factor was evaluated by a validated instrument. Results: One-hundred internists with the mean age of 41.98±9.26 years were evaluated. Totally, the physicians possessed 66.29%±19.5%, 50.44%±19.39%, and 64.5%±15.3% of the scores in KAP, respectively. The time since graduation in general medicine had significant negative correlation with their knowledge and practice, that was along with the subjects’ age (P<0.05). The KAP level had not significant difference between subjects participated in a continuing medical education (CME) program during the last year compared to subjects did not participated (P>0.05). Attitude, and practice scores were significantly higher in physicians who were working at diabetes clinic (P<0.05), and attitude was more in physicians working at teaching hospitals compared to those who were not working (57.82 vs. 47.72, P=0.020). Conclusion: According to our results, subjects’ age and time since graduation in general medicine and specialty were inversely correlated by knowledge and practice. So internists with older age seems to be in priority for educational programs. And holding CME programs in current forms seems to be not suitable to increase the KAP regarding diabetes.

A Novel AE Based Algorithm for PD Localization in Power Transformers

Mehdizadeh, Sina,Yazdchi, Mohammadreza,Niroomand, Mehdi The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

In this paper, a novel algorithm for PD localization in power transformers based on wavelet de-noising technique and energy criterion is proposed. Partial discharge is one of the main failures in power transformers. The localization of which could be very useful for maintenance systems. Acoustic signals due to a PD event are transient, irregular and non-repetitive. So wavelet transform is an efficient tool for this signal processing problem that gives a time-frequency demonstration. First, different wavelet based de-noising methods are analyzed. Then, a reasonable structure for threshold value determining and applying manner on signals is presented. Evaluated errors are good evidences for choices. Next, applying the elimination low energy frequency bands is discussed and developed as a de-noising method. Time differences between signals are used for PD localization. Different ways in time arrival detection are introduced and a novel approach in energy criterion method is presented. At the end, the quality of algorithm is verified through the different assays in lab.

Technological Change and Contribution to Growth and Convergence

Edward Nissan,Farhang Niroomand 중앙대학교 경제연구소 2006 Journal of Economic Development Vol.31 No.1

This paper incorporates data on efficiency and output per worker for 1965 and 1990 for 57 countries divided into four groups to seek an understanding of similarities and differences among them. Tools employed were testing for equality of means and testing for convergence. The findings indicate that the gaps between the groups were widened during the period studied for both efficiency and output per worker. While divergence was observed when all countries were grouped in one set, there were indications of convergence when the groups were treated separately.

SOME PROPERTIES OF TENSOR CENTRE OF GROUPS

Moghaddam, Mohammad Reza R.,Niroomand, Payman,Jafari, S. Hadi Korean Mathematical Society 2009 대한수학회지 Vol.46 No.2

Let $G{\otimes}G$ be the tensor square of a group G. The set of all elements a in G such that $a{\otimes}g\;=\;1_{\otimes}$, for all g in G, is called the tensor centre of G and denoted by $Z^{\otimes}^$(G). In this paper some properties of the tensor centre of G are obtained and the capability of the pair of groups (G, G') is determined. Finally, the structure of $J_2$(G) will be described, where $J_2$(G) is the kernel of the map $\kappa$ : $G{\otimes}\;{\rightarrow}\;G'$.

A Novel AE Based Algorithm for PD Localization in Power Transformers

Sina Mehdizadeh,Mohammadreza Yazdchi,Mehdi Niroomand 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

In this paper, a novel algorithm for PD localization in power transformers based on wavelet de-noising technique and energy criterion is proposed. Partial discharge is one of the main failures in power transformers. The localization of which could be very useful for maintenance systems. Acoustic signals due to a PD event are transient, irregular and non-repetitive. So wavelet transform is an efficient tool for this signal processing problem that gives a time-frequency demonstration. First, different wavelet based de-noising methods are analyzed. Then, a reasonable structure for threshold value determining and applying manner on signals is presented. Evaluated errors are good evidences for choices. Next, applying the elimination low energy frequency bands is discussed and developed as a de-noising method. Time differences between signals are used for PD localization. Different ways in time arrival detection are introduced and a novel approach in energy criterion method is presented. At the end, the quality of algorithm is verified through the different assays in lab.

Analysis and Implementation of a New Single Switch, High Voltage Gain DC-DC Converter with a Wide CCM Operation Range and Reduced Components Voltage Stress

Honarjoo, Babak,Madani, Seyed M.,Niroomand, Mehdi,Adib, Ehsan The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.

Analysis and Implementation of a New Single Switch, High Voltage Gain DC-DC Converter with a Wide CCM Operation Range and Reduced Components Voltage Stress

Babak Honarjoo,Seyed M. Madani,Mehdi Niroomand,Ehsan Adib 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.

Some properties of tensor centre of groups

Mohammad Reza R. Moghaddam,Payman Niroomand,S. Hadi Jafari 대한수학회 2009 대한수학회지 Vol.46 No.2

Let G⊗G be the tensor square of a group G. The set of all elements a in G such that a⊗g = 1_⊗, for all g in G, is called the tensor centre of G and denoted by Z^⊗(G). In this paper some properties of the tensor centre of G are obtained and the capability of the pair of groups (G,G‘) is determined. Finally, the structure of J_2 (G) will be described, where J_2 (G) is the kernel of the map k : G ⊗ G → G'. Let G⊗G be the tensor square of a group G. The set of all elements a in G such that a⊗g = 1_⊗, for all g in G, is called the tensor centre of G and denoted by Z^⊗(G). In this paper some properties of the tensor centre of G are obtained and the capability of the pair of groups (G,G‘) is determined. Finally, the structure of J_2 (G) will be described, where J_2 (G) is the kernel of the map k : G ⊗ G → G'.