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متن کامل


نویسندگان: 

ASHRAFI S. | ALIEV N.

اطلاعات دوره: 
  • سال: 

    2012
  • دوره: 

    2
  • شماره: 

    3
  • صفحات: 

    2750-2757
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    183
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

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نویسنده: 

SERAJI AMIR | TEIMOURI FATEMEH

اطلاعات دوره: 
  • سال: 

    2014
  • دوره: 

    17
تعامل: 
  • بازدید: 

    160
  • دانلود: 

    0
چکیده: 

BACKGROUND: SODIUM SULFIDE (NA2S) IS THE MOST IMPORTANT AND APPLICABLE COMPOUND AMONG ALKALI AND ALKALINE EARTH SULFIDES. NA2S IS USED IN A PROCESS FOR PRODUCING POLY (PHENYLENE SULFIDE) AND POLYSULFIDE POLYMERS. IT ALSO IS USED IN REDUCTION OF POLYNITROAROMATICS AND IN ENGINE OILS [1]. IN THE LABORATORY, ANHYDROUS NA2S CAN BE PREPARED BY REACTION OF SULFUR WITH SODIUM IN ANHYDROUS AMMONIA OR IN DRY THF WITH A CATALYTIC AMOUNT OF NAPHTHALENE [2]:2 NA + S ® NA2SINDUSTRIALLY NA2S IS PRODUCED BY REDUCTION OF SODIUM SULFATE WITH CARBON, IN THE FORM OF COAL AT 700- 900OC [3]:NA2SO4 +2C®NA2S+2CO2METHODS: IN THIS RESEARCH WE WISH TO REPORT OPTIMIZED PROCESS FOR THE SYNTHESIS OF NA2S USING NA2SO4 AND COAL. RAW MATERIALS OF THE REACTION ARE GRINDED VERY WELL IN MORTAR WHICH PASS TROUGH SIEVE WITH MESH 100. THE MIX OF NA2SO4 AND COAL IS HEATED IN ELECTRICAL FURNACE. AFTER EVOLUTION OF CO2 AND CO BEGINS THE REACTION MASS BECOMES VERY FLUID ON FURTHER HEATING, IT BECOMES PASTY AND FINALLY SOLID. THE PRODUCED SODIUM SULFIDE THAT CONTAINS EXCESS CARBON, ASH COMPONENTS AND OTHER SOLID IMPURITIES IS LEACHED WITH WATER, AND THE UNDISSOLVABLE COMPONENTS ARE REMOVED BY FILTRATION. THE FILTRATE IS CONCENTRATED BY EVAPORATION AND SOLIDIFIES BY COOLING.RESULTS: OPTIMIZED WEIGHT RATIO OF NA2SO4 TO COAL WAS 3.94:1. BEST YIELD OBTAINED AT 800OC FOR 2 HOURS. IN LEACHING STEP WEIGHT RATIO OF WATER TO SOLID PRODUCT MASS WAS 2.4:1. PURITY OF THE EVAPORATED FINAL PRODUCT WAS 60% AND SOLIDIFICATION TEMPERATURE WAS 90OC.CONCLUSION: IN SUMMARY, WE FOUND AN ECONOMICAL AND LocalLY DEPENDENT PROCEDURE FOR PRODUCTION OF NA2S. THE FEATURES OF THIS METHOD ARE HIGH YIELDS, OPERATIONAL SIMPLICITY AND THE ENVIRONMENTALLY FRIENDLY METHOD.

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اطلاعات دوره: 
  • سال: 

    1393
  • دوره: 

    11
تعامل: 
  • بازدید: 

    505
  • دانلود: 

    186
چکیده: 

لطفا برای مشاهده چکیده به متن کامل (PDF) مراجعه فرمایید.

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نویسندگان: 

GLADKOV A. | NIKITIN A.

نشریه: 

VIRTUAL

اطلاعات دوره: 
  • سال: 

    621
  • دوره: 

    1
  • شماره: 

    1
  • صفحات: 

    1-10
تعامل: 
  • استنادات: 

    1
  • بازدید: 

    202
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

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بازدید 202

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نویسنده: 

ADABIPOUR MOJTABA | TEIMOURI FATEMEH

اطلاعات دوره: 
  • سال: 

    2014
  • دوره: 

    17
تعامل: 
  • بازدید: 

    999
  • دانلود: 

    0
چکیده: 

BACKGROUND: TETRA SODIUM PYROPHOSPHATE (TSPP) WITH THE FORMULA NA4P2O7 IS USED AS A BUFFERING AGENT, AN EMULSIFIER, A DISPERSING AGENT, AND A THICKENING AGENT, AND IS USED AS A FOOD ADDITIVE. TSPP IS SOMETIMES USED IN DETERGENTS AND TOOTHPASTE AS ANTI-DEPOSITION AGENT [1]. THE CONVENTIONAL TSPP PRODUCTION METHODS INVOLVE A TWO STEPS REACTION: 1) NEUTRALIZATION OF PHOSPHORIC ACID WITH NA2CO3 AT 90-105OC FOR PRODUCING DISODIUM PHOSPHATE (DSP) AND 2) CONDENSATION OF DSP IN CALCINATION CONDITION [2].METHODS: IN THIS RESEARCH WE WISH TO REPORT OPTIMIZED PROCESS FOR THE SYNTHESIS OF TSPP USING PHOSPHORIC ACID AND SODIUM HYDROXIDE AS ROW MATERIALS. IN THE 1ST STEP, PHOSPHORIC ACID IS NEUTRALIZED TO DSP AS A MIDDLE PRODUCT THEN THE WATER OF THE REACTION IS EVAPORATED AND IN THE 2ND STEP DRIED DSP IS CALCINED TO TSPP. (FIGURE 1).RESULTS: THE NAOH/H3PO4 MOLE RATIO WAS 1.98/1 AT 98OC AND THE WATER CONTENT OF DRIED DSP WAS 6.0%. THE CALCINATION TEMPERATURE WAS 300-350OC. THE PURITY OF TSPP WAS 98%.CONCLUSION: IN SUMMARY, WE FOUND AN ECONOMICAL PROCEDURE FOR PRODUCTION OF TSPP BY A TWO STEPS METHOD. THE FEATURES OF THIS PROCEDURE ARE HIGH YIELDS, OPERATIONAL SIMPLICITY AND THE ENVIRONMENTALLY FRIENDLY METHOD. MEANWHILE, PRODUCTION OF TSPP IS DEPENDENT ON THE Local Conditions.

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اطلاعات دوره: 
  • سال: 

    1401
  • دوره: 

    13
  • شماره: 

    1
  • صفحات: 

    43-68
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    145
  • دانلود: 

    10
چکیده: 

The central issue of the present paper is the study of the causes of the mother tongue decline in the Sahne city in Kermanshah province. The issue of language is beyond the dialect of people and is refer to the form of life and the matter of macroeconomic and political relations. From this perspective, the form of life and the language associated with it explain the praxis of the members of the society. The appropriate method of examining the problem should be able to analyze the justification of agents to their situation, that is why Grounded Theory is chosen as the method of this research and data analysis is taken from abduction reasoning. The results of the analysis introduced the categories of globalizing, modernizing, de-use of language, economic necessity and the government as the most important factors of Local language fading. In this essay the meaning of globalization is the globalizing of special type of economic relation that explain other categories role in the process of fading of languages.

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اطلاعات دوره: 
  • سال: 

    1400
  • دوره: 

    52
  • شماره: 

    2
  • صفحات: 

    67-82
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    168
  • دانلود: 

    16
چکیده: 

Identifying the constraining factors of production and yield gap is very important. Therefore; this research was performed to identify the production constraining factors of Local rice cultivars. All management practices from nursery preparation to harvesting stages for 100 paddy fields of Local rice cultivars were recorded through field studies, in Sari, from 2015-2016. In the CPA, the actual and calculated potential yield were 4495 and 5703 kg/ha, respectively and the gap was 1221 kg/ha. The yield gap caused by number of top-dressing variables was 324 kg/ha, equal to 27% of the total yield gap. The yield gap related to previous year of legumes cultivation was 218 kg ha-1, equal to 18% of the total yield variation. Among the 10 variables entered in the CPA model, the effects of top-dress fertilizer application and its application frequency and foliar application were remarkable, which could compensate a significant part of the yield gap (444 kg/ha, 37% of total) in the farmers’ fields by managing these variables. According to boundary line analysis (BLA) finding, actual yield mean on the basis of optimal limit related to 12 variables under study was 5369 kg/ha, with 881 kg/ha yield gap . Mean relative yield and relative yield gap for 12 variables (transplanting date, seedling age, number of seedlings per hill, planting density, nitrogen and phosphorous per hectare, nitrogen before transplanting, harvesting date, lodging problem, pest problem, diseases problem and weeds problem) were 83.64 and 16.35 kg/ha, respectively. Based on the finding, it can be stated that the model precision is appropriate and can be applied for both estimation of the quantity of yield gap and determining the portion of each restricting yield variables.

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نویسندگان: 

HOSSEINI SEYED MOHAMMAD | ALIEV N.

اطلاعات دوره: 
  • سال: 

    2000
  • دوره: 

    11
  • شماره: 

    3
  • صفحات: 

    233-237
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    336
  • دانلود: 

    0
چکیده: 

Krein [1] mentioned that for each PD equation we have two extreme operators, one is the minimal in which solution and its derivatives on the boundary are zero, the other one is the maximal operator in which there is no prescribed boundary Conditions. They claim it is not possible to have a related boundary value problem for an arbitrarily chosen operator in between. They have only considered Local Conditions and so their claim is justified, particularly, for partial differential boundary value problems of odd orders. By considering more general (non-Local and global) Conditions, we showed this is not necessarily true. With similarly general Conditions as considered in this paper one can define a boundary value problem for PDEs of odd order and also problems with Local Conditions will be a particular case of this general form. In this paper, a mixed problem for a parabolic equation with general Conditions is analytically investigated and, in a closed from, its unique solution is shown.

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اطلاعات دوره: 
  • سال: 

    1390
  • دوره: 

    11
  • شماره: 

    2
  • صفحات: 

    199-213
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    767
  • دانلود: 

    189
چکیده: 

جریان های محلی نقش تعیین کننده ای در انتقال آلاینده های جوی دارند. جو پایدار به همراه جریان های کم سرعت فراهم کننده شرایط مساعد برای افزایش غلظت آلودگی در مناطق شهری می باشند. این شرایط جوی زمینه ساز پیدایش جریان های محلی خصوصا در مناطق مجاور کوهستان ها است. لذا در این وضعیت جوی، به طور عمده جریان های محلی نقش کلیدی را در انتقال آلاینده ها بازی می کنند. از سوی دیگر یکی از عامل های مهم در برآورد میزان دید پروازها حجم آلاینده ها و پراکندگی آنها در مناطق فرودگاهی است. از اینرو آشکارسازی و شناخت این دسته از جریان ها در شهرهایی همچون تهران که از یک سو در دامنه رشته کوه ها قرار دارند و از سوی دیگر دارای بیشترین تراکم جمعیتی می باشند به طور مستقیم در تعیین و پیش بینی کیفیت هوا و سلامت ساکنین آن نقش دارد. چرا که رشته کوه ها با در بر داشتن تاثیرات مختلف دینامیکی و ترمودینامیکی عاملی در پیچیدگی بیشتر الگوی جریان ها شهرهای مجاور آنها (نظیر نقش رشته کوه البرز روی تهران) می باشند. در این مقاله به منظور آشکارسازی بهتر این جریان ها از یک نمایه قائم ایده آل، که شاخص یک جو پایدار با حداقل سرعت جریان است، به عنوان شرایط آغازین و مرزی مدل میان مقیاس، استفاده شده است. در ادامه جریان های محلی از جمله جریان های گرما واداشتی توسط مدل میان مقیاس پیش بینی وضع هوایWRF  شبیه سازی و عملکرد آن مورد ارزیابی قرار گرفته است. نتایج بیانگر تاثیر چیره جریان های ناشی از اثر کوهستان نسبت به جریان های شهری (اثر جزیره گرمایی) می باشد. با توجه به نتایج حاصل از این مقاله به نظر می رسد وجود مناطق شهری در مجاورت ارتفاعات می تواند تا حد زیادی انتقال جرم (آلودگی) و انرژی در لایه مرزی و از این لایه به جو آزاد را افزایش دهد. در کنار شبیه سازی های عددی، بررسی های مشاهداتی نشان دهنده تاخیر زمان گذار 2 الی 3 ساعتی در مناطق شمالی و جنوبی شهر است که این پدیده با شبیه سازی های ایده آل همخوانی دارد. وقوع این امر در ساعات گذار عصرگاهی پتانسیل افزایش آلودگی را تا حد قابل توجهی در این ساعات بالا می برد که این امر از دیدگاه مدیریت شهری بسیار حائز اهمیت است.

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نویسندگان: 

Goli Abdollah | ZAHMATKESH IMAN

اطلاعات دوره: 
  • سال: 

    2018
  • دوره: 

    6
  • شماره: 

    2
  • صفحات: 

    79-87
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    192
  • دانلود: 

    0
چکیده: 

In the present work, forced convection heat transfer of slip flow in porous micro-tubes with Local thermal non-equilibrium between the gas and the solid matrix is investigated numerically. For this purpose, the flow is considered hydrodynamically developed but thermally developing. The Darcy-Brinkman-Forchheimer model in conjunction with separate energy equations for the gas and the solid matrix is used to describe the flow and heat transfer in the porous media. Moreover, both velocity slip and temperature jump are applied to the fluid at the wall. Simulation results are presented in terms of velocity field, distributions of the fluid and solid temperatures, the Local Nusselt number, and the thermal entry length. The results indicate heat transfer improvement as a result of increase in the Peclet/Biot number. Increase in the Knudsen number or the modified conductivity ratio, however, diminishes the heat transfer rate. Although the choice of the Darcy/Forchheimer number may change the computational results, trends are not similar in the developing and the developed regions of the flow.

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