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COMMUTATOR LENGTH OF SOLVABLE GROUPS SATISFYING MAX-N
Mehri, Akhavan-Malayeri Korean Mathematical Society 2006 대한수학회보 Vol.43 No.4
In this paper we find a suitable bound for the number of commutators which is required to express every element of the derived group of a solvable group satisfying the maximal condition for normal subgroups. The precise formulas for expressing every element of the derived group to the minimal number of commutators are given.
Mehri-Saddat Ekrami-Kakhki,Nahid Farzaneh,Sedigheh Abbasi,Hadi Beitollahi,Seyed Ali Ekrami-Kakhki 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.5
In this research, graphene oxide was prepared by a modified Hummers’ method, and then functionalized with 1, 1′-dimethyl-4, 4′-bipyridinium dichloride (MV), and chitosan (CH) to get a MV–RGO–CH support. Pt nanoparticles were preparedon this support to get Pt/MV–RGO–CH catalyst. The morphology and microstructure of Pt/MV–RGO–CH catalyst werecharacterized with transmission electron microscopy image and X-ray diffraction analysis. The electrocatalytic activity ofthe prepared catalyst towards ethanol oxidation was investigated by carbon monoxide stripping voltammetry, cyclic voltammetry,and electrochemical impedance spectroscopy techniques. The effects of some experimental parameters such as scanrate, ethanol concentration, and temperature were investigated for ethanol electrooxidation at Pt/MV–RGO–CH catalyst. Durability of the catalyst was also investigated. The electrocatalytic performance of Pt/MV–RGO–CH catalyst for ethanoloxidation was compared with those of Pt/CH and Pt/MV–RGO catalysts. The higher electrocatalytic performance of Pt/MV–RGO–CH than Pt/CH and Pt/MV–RGO catalysts towards ethanol electrooxidation indicated that Pt/MV–RGO–CHcould be a promising catalyst for application in direct ethanol fuel cells.
Mehri, Fereshteh,Jenabi, Ensiyeh,Bashirian, Saeed,Shahna, Farshid Ghorbani,Khazaei, Salman Occupational Safety and Health Research Institute 2020 Safety and health at work Vol.11 No.2
Background: Rheumatoid arthritis (RA) is an autoimmune disease with systemic inflammatory arthritis. This meta-analysis was conducted to examine the association between occupational exposure to silica and the risk of developing RA among different workers. Methods: In this meta-analysis, we searched relevant published studies using major electronic databases including Scopus, PubMed, ISI Web of Science, and Google Scholar search engine up to October 2019, and the references of retrieved articles were also checked for further possible sources. A random-effects model was used to account for heterogeneity among the results of the studies using the pooled odds ratios (ORs) and their 95% confidence intervals (CIs). The Q-statistic and I<SUP>2</SUP> tests were calculated to assess heterogeneity between the studies. Results: The pooled calculation of OR indicated a significant association between occupational exposure to silica and risk of developing RA among different workers (OR = 2.59, 95% CI = 1.73 to 3.45). In addition, the pooled estimates of OR in smokers were statistically significant (OR = 2.49, 95% CI = 1.13 to 3.86). Conclusions: The findings of the present study reveal that occupational exposure to silica may be associated with increased risk of developing RA.
( Mehri Khoshhali ),( Iraj Kazemi ),( S. Mohsen Hosseini ),( Shiva Seirafian ) 대한신장학회 2017 Kidney Research and Clinical Practice Vol.36 No.2
Background: In peritoneal dialysis, technique failure is an important metric to be considered. This study was performed in order to identify the relationship between trajectories of serum albumin levels and peritoneal dialysis technique failure on end-stage renal disease patients according to diabetic status. Furthermore, this study was performed to reveal predictors of serum albumin and technique failure simultaneously. Methods: This retrospective cohort study included 300 (189 non-diabetic and 111 diabetic) end-stage renal disease patients on continuous ambulatory peritoneal dialysis treated in Al-Zahra Hospital, Isfahan, Iran, from May 2005 to March 2015. Bayesian joint modeling was carried out in order to determine the relationship between trajectories of serum albumin levels and peritoneal dialysis technique failure in the patients according to diabetic status. Death from all causes was considered as a competing risk. Results: Using joint modeling approach, a relationship between trajectories of serum albumin with hazard of transfer to hemodialysis was estimated as -0.720 (95% confidence interval [CI], -0.971 to -0.472) for diabetic and -0.784 (95% CI, -0.963 to -0.587) for non-diabetic patients. From our findings it was showed that predictors of low serum albumin over time were time on peritoneal dialysis for diabetic patients and increase in age and time on peritoneal dialysis, history of previous hemodialysis, and lower body mass index in non-diabetic patients. Conclusion: The results of current study showed that controlling serum albumin over time in non-diabetic and diabetic patients undergoing continuous ambulatory peritoneal dialysis treatment can decrease risk of adverse outcomes during the peritoneal dialysis period.
Mehri-Saddat Ekrami-Kakhki,Sedigheh Abbasi,Nahid Farzaneh 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.1
XCThepurpose of this study is to statistically analyze the anodic currentdensity and peak potential of methanol oxidation at Pt nanoparticlessupported on functionalized reduced graphene oxide (RGO), usingdesign of experiments methodology. RGO is functionalized with methylviologen (MV) and chitosan (CH). The novel Pt/MV-RGO-CH catalystis successfully prepared and characterized with transmission electronmicroscopy (TEM) image. The electrocatalytic activity of Pt/MV-RGOCHcatalyst is experimentally evaluated for methanol oxidation. Theeffects of methanol concentration and scan rate factors are alsoinvestigated experimentally and statistically. The effects of these twomain factors and their interactions are investigated, using analysis ofvariance test, Duncan’s multiple range test and response surface method. The results of the analysis of variance show that all the main factors andtheir interactions have a significant effect on anodic current density andpeak potential of methanol oxidation at α = 0.05. The suggested modelswhich encompass significant factors can predict the variation of theanodic current density and peak potential of methanol oxidation. Theresults of Duncan’s multiple range test confirmed that there is asignificant difference between the studied levels of the main factors.
Isolating the most recent entry in a random recursive tree by random cuts
Mehri Javanian,M. Q. Vahidi-Asl 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.16 No.-
A recursive tree is constructed by starting with a root node and repeatedly adjoining new nodes to one node of the tree already constructed. Such a tree can represent, for example, the heirarchy of a workforce of a company that grows via recruiting. At times of economic depression, the company may decide to lay off participants, and in some cases it is a fair policy to relieve the last senior worker (most recent entry in the tree). If we remove an edge from such a tree then it falls into two subtrees one of which contains the most recent entry. If we continue to remove edges from the successively smaller subtrees that contain the most recent entry, we eventually isolate the most recent entry. We consider how many randomly selected edges must be removed in average before isolating the most recent entry by this procedure.
Safety Evaluation of the Lighting at the Entrance of a Very Long Road Tunnel: A Case Study in Ilam
Mehri, Ahmad,Hajizadeh, Roohalah,Dehghan, Somayeh Farhang,Nassiri, Parvin,Jafari, Sayed Mohammad,Taheri, Fereshteh,Zakerian, Seyed Abolfazl Occupational Safety and Health Research Institute 2017 Safety and health at work Vol.8 No.2
Background: At the entrance of a tunnel, reflection of sunlight from the surrounding environment and a lack of adequate lighting usually cause some vision problems. The purpose of this study was to perform a safety evaluation of lighting on a very long road in Ilam, Iran. Methods: The average luminance was measured using a luminance meter (model S3; Hagner, Solna, Sweden). A camera (model 108, 35-mm single-lens reflex; Yashica, Nagano, Japan) was used to take photographs of the safe stopping distance from the tunnel entrance. Equivalent luminance was determined according to the Holliday polar diagram. Results: Considering the average luminance at the tunnel entrance ($116.7cd/m^2$) and using Adrian's equation, the safe level of lighting at the entrance of the tunnel was determined to be 0.7. Conclusion: A comparison between the results of the safe levels of lighting at the entrance of the tunnel and the De Boer scale showed that the phenomenon of black holes is created at the tunnel entrance. This may lead to a misadaptation of the drivers' eyes to the change in luminance level at the entrance of the tunnel, thereby increasing the risk of road accidents in this zone.
Mehri Kouhkan,Behzad Zeynizadeh 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.10
Reduction of carbonyl compounds such as aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones and acyloins was carried out readily with NaBH3CN in the presence of wet SiO2 as a neutral media. The reactions were performed at solvent-free conditions in oil bath (70 - 80 oC) or under microwave irradiation (240 W) to give the product alcohols in high to excellent yields. Regioselective 1,2-reduction of conjugated carbonyl compounds took place in a perfect selectivity without any side product formation.
Mehri, Fereshteh,Bashirian, Saeid,Khazaei, Salman,Jenabi, Ensiyeh The Korean Pediatric Society 2021 Clinical and Experimental Pediatrics (CEP) Vol.64 No.6
Background: The effect of exposure to environmental factors on autism spectrum disorders (ASD), especially during pregnancy, is unclear. Purpose: This meta-analysis investigated the association between exposure to pesticides and polychlorinated biphenyls (PCBs) during pregnancy and ASD risk among children. Methods: We searched Scopus, PubMed, Web of Science, and ProQuest for articles published through September 2019. Random-effects models were used to examine the association among studies using pooled odds ratios (ORs) and their 95% confidence intervals (CI). I2 tests were used to measure interstudy heterogeneity. Results: The pooled OR indicated a significant association between PCB and pesticide exposure during pregnancy and ASD risk among children (OR, 1.80; 95% CI, 1.26-2.34; and OR, 1.20; 95% CI, 1.02-1.39), respectively. Conclusion: Findings of the present study indicate that exposure to pesticides and PCBs during pregnancy may affect the risk of ASD among children.