New Synthesis of Perhydrotriazolotriazoles Catalyzed by TiCl₄ under Ambient Conditions

Safari, J.,Gandomi-Ravandi, S.,Ghotbinejad, M. Korean Chemical Society 2012 대한화학회지 Vol.56 No.1

Aromatic 2,3-diazabuta-1,3-dienes in glacial acetic acid with isothiocyanate in the presence of catalyst $TiCl_4$ at room temperature produced via criss-cross cycloaddition reactions the corresponding perhydro[1,2,4]triazolo[1,2-a][1,2,4] triazole-1,5-dithiones in relatively high yields and short reaction time.

New Die Design Configuration for Grain Refinement by Hollow Twist Extrusion (HTE) Process

J. Joudaki,M. Safari,S. M. Alhosseini 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4

The severe plastic deformation (SPD) processes used for applying an extensive shear plastic strain in the material andconsequently grain refinement and increase in the strength of materials. The strain distribution is very important and morehomogenous plastic strain is desired in SPD process modifications. In this article, four different die configurations will beinvestigated during the hollow twist extrusion (HTE) process and the plastic strain distribution will be compared within ahollow section. The die configurations are similar slope line angle of inner and outer dies (SD), opposite slope line anglebetween the inner and outer dies (OD), outer die with twist zone and flat inner die (FI) and inner die with twist zone and flatouter die (FO). The Von-Mises stress, plastic strain, and material deformation are studied by using a finite element modelwhich was developed in the ABAQUS finite element software. The results show that the FI and FO die configuration producehigher plastic strains than SD die configuration, but the strain homogeneity is not satisfactory. The plastic strain is higherand more homogenous for OD die configuration in comparison to the other die configurations. The required force for twistextrusion of the billet is almost equal for FI and FO die configuration (~ 216 kN) and increases to about 256 kN for SD dieconfiguration (16% increase). The required force for OD die configuration increased once more to 370 kN (44.5% increase). The element distortion along the two defined paths determined the material flow during the HTE process. The flat die retardsthe material flow for FI and FO die configurations. A significantly material flow will happen for OD die configuration. Theelement distortion leads to better material mixing in OD die configuration and consequently higher magnitude and morehomogenous plastic strain distribution and higher grain refinement will be obtained.

Hollow Twist Extrusion: Introduction, Strain Distribution, and Process Parameters Investigation

J. Joudaki,M. Safari,S. M. Alhosseini 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6

Twist Extrusion is kind of severe plastic deformation process which enhances the strength of materials by applying a shearplastic strain and consequently grain refinement. The strain distribution is minimum at the center of the die and is maximumat outer surfaces. In this article, the plastic strain distribution will be studied within a hollow section. The billet is solid inprevious experimental and numerical studies in the literature, but by adding a new die (mandrel) for extruding the hollowbillet, it is possible to twist extrude hollow sections. A finite element model is developed in the ABAQUS finite elementsoftware and the effects of process parameters (slope line angle, thickness and friction coefficient) on equivalent plastic straindistribution are investigated. The numerical results show that the equivalent plastic strain will be increased by increasingthe slope line angle and decreasing the thickness and more homogeneity in the strain field will be obtained. In addition,increasing the friction coefficient higher than 0.2 can lead to an increase in induced plastic strain. The required force fortwist extrusion will be increased by increasing the friction coefficient.

Combined Design of PSS and STATCOM Controllers for Power System Stability Enhancement

Ahmad Rohani,M. Reza Safari Tirtashi,Reza Noroozian 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.5

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system’s low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.

Combined Design of PSS and STATCOM Controllers for Power System Stability Enhancement

Rohani, Ahmad,Tirtashi, M. Reza Safari,Noroozian, Reza The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.5

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system's low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.

Investigation of key parameters influence on performance of direct ethanol fuel cell (DEFC)

Saeed Heysiattalab,Mehdi Safari,Mohsen Shakeri,M.M. Keikha 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.4

Direct ethanol fuel cell has been declared as a new alternative for other fuel cells such as direct methanol fuel cell and proton exchange membrane fuel cells. In this paper, effects of key parameters such as temperature, anode and cathode flow rate, molarity and cathode pressure have been investigated on ethanol fuel cell performance. Maximum power density and fuel cell performance will increase by temperature rising because of ion conductivity, diffusion and reaction rate increase. Molarity augmentation will increase ethanol concentration in catalyst layer and reaction rate which leads to better performance of the cell. Anode and cathode flow rate and cathode pressure will slightly increase fuel cell performance.

Photocatalytic process by immobilized carbon black/ZnO nanocomposite for dye removal from aqueous medium: Optimization by response surface methodology

R. Darvishi Cheshmeh Soltani,A. R. KHATAEE,A. Rezaee,M. Safari 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

A rectangular photo-reactor equipped with carbon black (CB)/ZnO nanocomposite film was used for photodegradation of methyl orange. Central composite design was used for evaluation of the effects of initial dye concentration, reaction time, CB/ZnO ratio and initial pH. The high correlation coefficients (R2 = 0.954 and adjusted R2 = 0.912) obtained by analysis of variance (ANOVA) demonstrated close fit between the predicted and experimental values. The initial dye concentration, reaction time, CB/ZnO ratio and initial pH were 13 mg/L, 95 min, 0.05 and 5, respectively for 80% decolorization efficiency. The result of TOC analysis showed that the process allowed 55.79% mineralization under optimized conditions.

Schistosoma mansoni Infection and Its Related Morbidity among Adults Living in Selected Villages of Mara Region, North-Western Tanzania

Humphrey D. Mazigo,Fred Nuwaha,David W. Dunn,Godfrey M. Kaatano(편집자),Tekla Angelo,Stella Kepha,Safari M. Kinung’hi 대한기생충학열대의학회 2017 The Korean Journal of Parasitology Vol.55 No.5

Chemical Composition and Meat Quality Attributes of Indigenous Sheep and Goats from Traditional Production System in Tanzania

Shija, Dismas S.,Mtenga, Louis A.,Kimambo, Abiliza E.,Laswai, Germana H.,Mushi, Daniel E.,Mgheni, Dynes M.,Mwilawa, Angello J.,Shirima, Eligy J.M.,Safari, John G. Asian Australasian Association of Animal Productio 2013 Animal Bioscience Vol.26 No.2

The aim of the study was to compare chemical composition and quality attributes of meat between male long fat tailed sheep (n = 17) and Small East African goats (n = 17) existing in Tanzania. Animals of 1.5 to 2 yrs in age and live body weight of $22.59{\pm}0.50$ kg were purchased from livestock auction markets. Animals were fasted for 18 h and slaughtered according to standard halal procedure. Left carcasses were dissected into muscles, fat and bone and the muscle and fat were mixed together and chemically analysed. Meat quality attributes were measured based on Muscle longissimus thoracis et lumborum excised from right sides of carcasses. Goat carcasses had significant higher (p = 0.0302) moisture content (70.65% vs 66.96%) and lower (p = 0.0027) ether extract (2.49% vs 5.82%) than sheep but there was no significant species differences in protein and ash content. Sheep had lower (p = 0.0157) ultimate pH (5.74 vs 5.88) and higher (p = 0.0307) temperature ($3.77^{\circ}C$ vs $3.15^{\circ}C$) than goat carcasses. Sheep meat had lower (p = 0.0021) shear force values (29.83 N vs 34.07 N) than goat. Within species, at day 9 of ageing, meat tenderness improved (p = 0.0001) by 44.63% and 34.18% for sheep and goat. Pooled data showed that at d 9 of ageing, meat tenderness improved (p = 0.0001) by 39.25% (from 39.54 N to 24.02 N) compared to tenderness of meat which was not aged at day one of slaughter. The present study demonstrated the differences in chemical composition and quality attributes of meat existing between sheep and goats originated from East Africa.

Meat Quality Characteristics of Small East African Goats and Norwegian Crosses Finished under Small Scale Farming Conditions

Hozza, W.A.,Mtenga, L.A.,Kifaro, G.C.,Shija, D.S.N.,Mushi, D.E.,Safari, J.G.,Shirima, E.J.M. Asian Australasian Association of Animal Productio 2014 Animal Bioscience Vol.27 No.12

The aim of the experiment was to study the effect of feeding system on meat quality characteristics of Small East African (SEA) goats and their crosses with Norwegian ($SEA{\times}N$) goats finished under small scale farming conditions. Twenty four castrated goats at the age of 18 months with live body weight of $16.7{\pm}0.54kg$ from each breed (SEA and $SEA{\times}N$) were distributed in a completely randomized design in a $2{\times}3$ factorial arrangement (two breed, and three dietary treatments). The dietary treatments were; no access to concentrate (T0), 66% access to ad libitum concentrate allowance (T66) and 100% access to ad libitum concentrate allowance with 20% refusal (T100) and the experimental period was for 84 days. In addition, all goats were allowed to graze for 2 hours daily and later fed grass hay on ad libitum basis. Daily feed intakes were recorded for all 84-days of experiment after which the animals were slaughtered. Feed intake of T100 animals was 536 g/d, which was 183 g/d higher than that of T66 group. Supplemented goats had significantly (p<0.05) better feed conversion efficiency. The SEA had higher (p<0.05) hot carcass weight (8.2 vs 7.9 kg), true dressing percentage (54.5 vs 53.3) and commercial dressing percentage (43.3 vs 41.6) compared to $SEA{\times}N$. There was no significant difference (p>0.05) for dressing percentage and carcass conformation among supplemented goats except fatness score, total fat depots and carcass fat which increased (p<0.05) with increasing concentrate levels in the diet. Increasing level of concentrate on offer increased meat dry matter with subsequent increase of fat in the meat. Muscle pH of goats fed concentrate declined rapidly and reached below 6 at 6 h post-mortem but temperature remained at $28^{\circ}C$. Cooking loss and meat tenderness improved (p<0.05) and thawing loss increased (p<0.05) with ageing period. Similarly, meat tenderness improved (p<0.05) with concentrate supplementation. Shear force of muscles varied from 36 to 66, the high values been associated with Semimembranosus and Gluteobiceps muscles. The present study demonstrates that there are differences in meat quality characteristics of meat from SEA goats and their crosses with Norwegian breeds finished under small scale farming conditions in rural areas. Therefore, concentrate supplementation of goats of both breeds improves meat quality attributes.