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متن کامل


اطلاعات دوره: 
  • سال: 

    2010
  • دوره: 

    13
تعامل: 
  • بازدید: 

    312
  • دانلود: 

    0
چکیده: 

LABORATORY INVESTIGATION HAS BEEN CARRIED OUT ON MIXING POWER CONSUMPTION AND FLOW regime Transition IN A FULLY BAFFLED STIRRED TANK REACTOR EQUIPPED WITH DUAL SIX-BLADE RUSHTON TURBINES BY ELECTRICAL MEASUREMENT TECHNIQUE. AN EMPIRICAL CORRELATION HAS BEEN DERIVED USING PREDICTED EXPERIMENTAL DATA, WHICH PRESENTS A NEW RELATION IN ESTIMATION OF POWER CONSUMPTION IN STIRRED TANKS WITH DUAL RUSHTON IMPELLERS. RESULTS HAVE BEEN COMPARED WITH DATA AVAILABLE IN TECHNICAL LITERATURE. A REASONABLE AGREEMENT BETWEEN THE EXPERIMENTAL AND TECHNICAL LITERATURE RESULTS HAS BEEN OBSERVED.

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اطلاعات دوره: 
  • سال: 

    2014
  • دوره: 

    8
تعامل: 
  • بازدید: 

    184
  • دانلود: 

    0
چکیده: 

IN THIS WORK THE EFFECTS OF GAS FLOW AND SOLID CONCENTRATION ON BUBBLE SIZE DISTRIBUTION AND regime Transition IN A CONCENTRIC AIRLIFT CONTACTOR (10×10-3 M3 IN VOLUME) EQUIPED WITH PERFORATED RING SPARGER WERE INVESTIGATED. NONINVASIVE IMAGE PROCESSING WAS USED FOR BOTH THE VISUAL OBSERVATIONS OF THE PHENOMENA OCCURRING INTO DRAFT TUBE AND BUBBLE SIZE MEASUREMENTS. THE RESULTS OF EXPERIMENTS SHOWED THAT THE GAS FLOW STRONGLY AFFECTS THE BUBBLE FORMATION WHERE IT CAN PROVIDE A SUFFICIENT GAS-LIQUID INTERFACIAL AREA WITHOUT ADDING IMPURITIES SUCH AS SURFACTANTS. THE CHANGE FROM HOMOGENEOUS TO Transition FLOW IN TWO-PHASE FLOW APPEARED AT SUPERFICIAL GAS VELOCITY, UGS, OF 0.79 CM/S BECAUSE OF THE START OF COALESCENCE AND IT WAS FOUND THAT EVEN AT HIGH GAS THROUGHPUT (UGS³0.79CM/S) COALESCENCE MECHANISM DIDN’T OCCUR BEFORE THE HEIGHT OF 0.55M OF DRAFT TUBE WHICH WAS THE SPARGER ZONE. MOREOVER, IN THREE-PHASE SYSTEM RESULTS SHOWED FROM 0.5CM/S TO 0.6CM/S OF SUPERFICIAL GAS VELOCITIES, SOLIDS HAD TENDENCY TO CLUMP AND CHANNEL BUBBLES WAY IN COLUMN, WHICH MAKES THE COALESCENCE OF THE GAS BUBBLES EASIER.

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نشریه: 

GAS PROCESSING

اطلاعات دوره: 
  • سال: 

    2016
  • دوره: 

    4
  • شماره: 

    1
  • صفحات: 

    53-61
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    246
  • دانلود: 

    0
چکیده: 

Different flow patterns of downward gas-liquid two-phase flow using simple mixer are studied in an experimental manner. An experimental setup is designed and fabricated to allow the visual observation of downward two-phase flow patterns and their Transitions. The flow patterns are recorded by a 1200 frames per second high speed video camera. The quality of downward two-phase flow patterns photos are improved through image processing. The setup includes a transparent vertical pipe of 50 mm diameter and the (L/d) aspect ratio of 80. Flow patterns are obtained through 374 test cases during which air and water superficial velocities changed. In order to assess the performance of the mixer, all expected flow patterns are obtained. The four observed flow regimes are: of falling film, bubbly, slug and froth. The flow map is plotted and Transitions among different flow patterns are compared with previous finding in specified conditions indicating a good agreement was observed.

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نشریه: 

Scientia Iranica

اطلاعات دوره: 
  • سال: 

    2006
  • دوره: 

    13
  • شماره: 

    2
  • صفحات: 

    174-186
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    340
  • دانلود: 

    0
کلیدواژه: 
چکیده: 

Air-water two-phase flow usually occurs during a sudden rise in water level at a tunnel or during the falling of the water level at an upstream reservoir while entering the conduit. When this happens, different flow patterns are generated, due to the hydraulics of flow and fluid properties. An analytical/numerical model, based on the assumption of a rigid incompressible water column and a compressible air bubble, is derived, to simulate pressure fluctuation, void fraction, air/water flow rate and water velocity in a closed conduit, including water depth at the upper reservoir, due to air bubbles becoming trapped in the water, for the highest possible number of flow patterns. It is a comprehensive model, which can generate different hydraulic situations in closed conduits such as tunnels and culverts, based on a hydraulic approach. The boundary conditions are a system of algebraic or/and simple differential equations. The steady solution of the governing differential equations is, generally, performed as the initial data. The frequency of pressure fluctuation and air/water flow rate predicted by the model is in close agreement with the results of the experiments and the numerical model referred to in the literature. Hence, the present model, which is simply derived due to one-dimensional assumptions, shows itself to be a good tool for predicting the characteristics of a two-phase flow.      

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اطلاعات دوره: 
  • سال: 

    1397
  • دوره: 

    6
  • شماره: 

    1
  • صفحات: 

    49-77
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    417
  • دانلود: 

    242
چکیده: 

با وجود پتانسیل بسیار بالای ایران در تولید برق از سیستمهای خورشیدی فتوولتاییک، انتشار این سیستم ها بسیار کند است. پژوهش حاضر که در بازه ی زمانی1397-1395صورت گرفته، با ترکیب رویکردهای چند سطحی و نظام نوآوری فناورانه، در پی شناسایی و بررسی موانعی برآمده که رژیم اجتماعی – فنی برق فسیلی ایران در بستر تاریخی و فرهنگی خود موجبات عدم گذار به سیستم های خورشیدی فتوولتاییک را فراهم آورده اند. بدین منظور، در مرحله نخست، ابتدا پس از مرور ادبیات، مصاحبه با خبرگان و سپس تحلیل مضمون داده های حاصله، موانع گذار با تاکید بر رژیم شناسایی شدند و سپس از تکنیک دلفی فازی جهت آزمون نتایج و خبره سنجی استفاده گردید که نهایتا 10 مانع در 4 دسته ی اقتصادی، نهادی، سیاسی و فنی طبقه بندی شدند که از جمله ی آنها می توان به کنترل بازار توسط رژیم حاکم، بکارگیری استراتژی های گفتمانی، تنظیم مقررات و استانداردها و. . . اشاره کرد. در مرحله ی دوم نیز مصاحبه با خبرگان و استفاده از روش تحلیل و توسعه گزینه های استراتژیک (سودا) مشخص کرد که این موانع بیشترین تاثیر را بر کارکردهای مشروعیت بخشی، تخصیص منابع و جهت دهی به سیستم داشته اند. در نهایت نیز تعدادی سازوکار برای غلبه بر این موانع پیشنهاد گردید.

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نویسندگان: 

پروین بابک

اطلاعات دوره: 
  • سال: 

    1400
  • دوره: 

    21
  • شماره: 

    1 (پیاپی 83)
  • صفحات: 

    171-180
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    53
  • دانلود: 

    3
چکیده: 

سازوکار یک اتم چهار ترازی محصور شده در یک کاواک اپتیکی تک مد با گذار چند فوتونی از لحاظ تئوری در حالت پایا بررسی شده است. رفتار سامانۀ اتم- کاواک بر حسب معادلة اصلی بیان شده است که برای حل این معادله، از مجموعه ای از مقادیر چشمداشتی یک سری عملگر استفاده شده است. روش کسرهای دنباله دار ماتریسی برای حل عددی این دسته از مقادیر چشمداشتی جفت شده به کار رفته است. نحوۀ تغییرات کمیت های فیزیکیِ وارونی جمعیت اتمی، تعداد فوتون میانگین و تابع همبستگی مرتبة دوم به ازای هر گذار مطالعه شده است. در نهایت فرایند تبدیل اتم چهار ترازی به یک اتم سه ترازی تحت چندین شرط خاص برای هر گذاری، مورد بحث قرار گرفته است.

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نویسندگان: 

براتی جواد | مجرد عصمت

اطلاعات دوره: 
  • سال: 

    1400
  • دوره: 

    11
  • شماره: 

    42
  • صفحات: 

    154-169
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    149
  • دانلود: 

    503
چکیده: 

اثرپذیری گسترده بخش گردشگری از نوسانات ارزی و سطوح متفاوت توسعه گردشگری در استان های مختلف در ایران، باعث می شود که اثرات گردشگری بر رشد اقتصادی استان ها متمایز از یکدیگر باشد. بررسی این موضوع در قالب تعیین اثرات تغییر رژیمی گردشگری بر رشد اقتصادی استان ها، دیدگاه برنامه ریزان منطقه ای در کشور بهبود خواهد بخشید. از اینرو، این مطالعه به بررسی فرضیه رشد اقتصادی مبتنی بر گردشگری و اثرات تغییر رژیمی گردشگری بر رشد اقتصادی چهار استان بزرگ گردشگرپذیر (اصفهان، خراسان رضوی، فارس وگیلان) پرداخته است. بدین منظور، از تکنیک های غیرخطی و مدل انتقال ملایم (STAR) برای سنجش اعتبار فرضیه وجود رابطه ی غیرخطی بین گردشگری و رشد اقتصادی استفاده شده است. همچنین، از علیت گرنجر برای بررسی فرضیه تحقیق در دوره مورد مطالعه 1387-1396 استفاده شده است. نتایج مطالعه، اثرات غیرخطی بین گردشگری و رشد اقتصادی را تایید کرده است، بطوریکه نتایج بین استانی، رفتار متمایز و اثرات متفاوتی را نشان داده است. طبق نتایج بدست آمده، در استان های اصفهان و فارس، گردشگری تاثیری بر ارزش تولید ناخالص منطقه ای ندارد. علاوه بر این، خطی بودن این رابطه برای استان های خراسان رضوی و گیلان رد می شود و گردشگری تاثیری به سزایی بر ارزش تولید ناخالص این استان ها دارد. جریان غیرخطی علیت گرنجر در همه ی موارد اثبات علیت از ارزش تولید ناخالص منطقه ای به گردشگری را تایید می کند. لذا ارزش تولید ناخالص منطقه ای بر گردشگری تمامی استان های اصفهان، خراسان رضوی، فارس و گیلان تاثیر قابل توجهی دارد. بنابراین می توان توصیه نمود که با بهبود رشد اقتصادی جهت توسعه گردشگری تلاش نمود. همچنین بایستی تصمیم گیران اقتصادی وجود رابطه ی غیرخطی در ارتباط پویا ی بین گردشگری و رشد اقتصادی را برای تعیین سطح آستانه ای از منافع بالقوه توسعه گردشگری در برنامه ریزی های آینده مورد توجه قرار دهند.

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اطلاعات دوره: 
  • سال: 

    1393
  • دوره: 

    14
  • شماره: 

    9
  • صفحات: 

    203-210
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    1136
  • دانلود: 

    393
چکیده: 

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نویسندگان: 

Hanaee Toktam | Farhangdoust Hadi

اطلاعات دوره: 
  • سال: 

    1402
  • دوره: 

    11
  • شماره: 

    2
  • صفحات: 

    133-152
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    204
  • دانلود: 

    30
چکیده: 

ABSTRACT The attention of contemporary planners to environmental factors and increasing awareness and communication of man with his surrounding environment has increased the layers and defining factors of design and planning concepts. In such a way, a common problem with the issue of environmental capabilities to respond was put in front of the planners. The collection of ideas presented in this era was in the form of responsive planning, focusing on the maximum use of environmental capabilities. The necessity of the emergence of a comprehensive discourse to overcome the plurality of factors, definitions and design methods in the environmental fields has been given less attention. Based on this, the current research aims to organize the leading theories in this field in a targeted manner and seeks to improve them based on their synergy. The structural question of this research is the meanings, examples and meaningful contexts of flexibility in various aspects and scales of urban planning. The research method used is qualitative thematic analysis with the help of artificial intelligence in MAXQDA software in a 6-step processing process. The important application of this research is to structure the minds of the planners of this field to reduce the scattered and interdisciplinary problems of the resources. The results of this research revealed dimensions such as identification and recognizability, diversity and changeability, adaptability and expandability, distribution, separation and continuity, organization and compatibility in the field of flexibility and related to the corresponding parts in urban planning   Extended Abstract Introduction Responsiveness-based design and planning emphasizing the maximum use of environmental capacities to meet users' needs implicitly cause a targeted improvement of environmental quality. As the environmental awareness of contemporary man has expanded and the platforms have become more diverse, many challenges are raised in the field of environment-oriented in the field of infrastructure quality and service provision. Urban developments and new developments in cities should be interpreted with integrated conceptualization. The conceptualization of interpretive flexibility in the planning and designing of public spaces in the city is used as an interdisciplinary perspective in urban space design to open and discuss its connection and potential as an approach to strengthening social cohesion and inclusion. The general definition of flexibility is that it can create places with new forms of meaning and be used for different groups to strengthen its coherence and multidisciplinary inclusion in terms of design and planning of space and body. On this basis, the concept of flexibility is proposed as a principle in the context of design and planning due to its wide range of effects on background phenomena. The history of such a role can be seen in the diversity of users' needs. In such a way, it is impossible to express the specific time and area of the need to pay attention to this concept. This is in line with Oldenburg's theory of "social public spaces," in which being in public space, communicating with people and the environment through observing the streets, sidewalks, squares, and parks of the city is a necessary step for people as a part of their social life. The meaningfulness of the design of the artificial environment was considered. In any case, in the contemporary era, on the one hand, at the same time as the quantitative and qualitative increase of human environmental awareness, there is no longer any phenomenon in the eyes of contemporary man arising from a unique aspect and range of factors. On the other hand, his life needs in the individual and collective dimensions have seen a high diversity, which has led to the formation of multiple semantic domains of past flexibility. The meaning of flexibility in such an interdisciplinary platform and basic design refers to the concept of understanding and responding quickly and efficiently to environmental changes. Such a holistic definition for this broad field of environmental design means the implicit acceptance of the role of scale in the meaningful domain of these concepts. On a macro scale, it means making design options to increase the presence, participation, and power of choices of users of the environment in participatory urban planning and design methods, and on a small scale, it means making design options to increase spatial quality and, as a result, the quality of activities. The daily activities of environmental users are through selection against the "dominant space." Flexibility at different scales is crucial for dimensional optimization, shaping, and structuring spatial features, leading to improved performance of space components and spaces. The development of the concept of "flexibility" from various studies in metropolitan to micro scales, such as interior architecture, allows it to pass the discourse of responsiveness to provide a broad approach to environmental design in which different values, interests, and priorities are prioritized. As a result, the issue of flexibility in environmental design has been raised as a multi-dimensional field in the design and planning of the basic environment. The breadth and complexity of this concept have made the researchers of this field deal with it in one or more ways, and it has been avoided to provide a comprehensive framework about the nature and structuring processes. The current research presents a structured view of flexibility in architecture and urban planning with an environmental approach.   Methodology The methodology to achieve this goal is to use the macro research method and achieve a comprehensive framework by combining categorized interpretations. In such a way that by sorting and categorizing these concepts and bases in a new way, he has found a new level of theoretical findings, which will be a suitable answer for the gaps in scientific knowledge and scientific methods created in this field. In this context, the research method "thematic analysis" has been used with a qualitative approach and the use of library resources. Also, to overcome the breadth and complexity of these concepts and the multi-layer networking of concepts in this research method, artificial intelligence has been used in MAXQDA research assistance software.   Results and discussion In the meantime, attention should also be paid to the fields of influence and application of the results of this research because designers refer to flexibility as the creator of environmental qualities, including dynamism. Also, since flexibility, along with the principles of readability and adaptability, affect the lifestyle and behavioral patterns of the audience of environmental design in architecture and urban planning, it will also be effective in dealing with the challenge of complexity in environmental design factors. One of the key questions for achieving research goals on this issue is how flexibility in environmental design impacts the relationship between flexibility and scale.   Conclusion The most important finding of this research suggests that first, it requires a focus on the conditions under which the processes of perceiving human abilities and discovering the needs of the human audience can manifest. The theoretical framework arises from a comparative approach between design disciplines. These conditions are independent of the final state of the design product, and strengthening the environmental capacities will lead to a direction and an area that includes environmental flexibility. By responding to new situations, the construction of the space and the body within a space building can be adapted to various configurations. Even though the environment may remain constant, the designed place will continue functioning as a strong living system over time.  It also seems that the nature of issues related to flexibility has complexity. Considering that the quality of flexibility in urban planning and architecture is significant in multilevel and multifaceted scales from micro to macro, it is important to pay attention to the scale of different variables. In order to reduce this problem, the consistency and adjustment of the scale of the variables measured in a specific analysis should be considered in the first step.   Funding There is no funding support.   Authors’ Contribution All of the authors approved the content of the manuscript and agreed on all aspects of the work.   Conflict of Interest Authors declared no conflict of interest.   Acknowledgments We are grateful to all the scientific.

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اطلاعات دوره: 
  • سال: 

    1395
  • دوره: 

    5
  • شماره: 

    17
  • صفحات: 

    67-98
تعامل: 
  • استنادات: 

    0
  • بازدید: 

    566
  • دانلود: 

    196
چکیده: 

شدت انرژی از جمله شاخص های مهم و مورد توجه در اقتصاد انرژی است. در ایران با توجه به فراوانی منابع انرژی، متاسفانه از این منابع به درستی استفاده نشده و بنابراین شدت انرژی به نسبت دیگر کشورها بسیار بالاست. از این رو در این مقاله با استفاده از یک روش رگرسیون غیر خطی به بررسی عوامل موثر بر شدت انرژی در ایران طی دوره 1357-1392 پرداخته ایم. نتایج حاکی از وجود دو رژیم حدی برای اثرگذاری متغیرهای تحت بررسی با در نظر گرفتن قیمت نسبی انرژی به عنوان متغیر انتقال با حد آستانه ای 1.58 می باشد. نرخ شهرنشینی و سهم صنعت از تولیدناخالص داخلی باعث افزایش شدت انرژی در ایران شده اند و سطح تکنولوژی و قیمت نسبی انرژی دارای اثر منفی بوده اند. میزان اثرگذاری قیمت نسبی انرژی در رژیم قیمت بالا تشدید شده و میزان اثرگذاری سهم صنعت و سطح تکنولوژی در این رژیم تقلیل یافته است. این نتایج بیانگر نقش مهم رژیم قیمتی در مساله شدت انرژی در ایران بوده و سیاستگزاران را به جلوگیری از کاهش قیمت نسبی انرژی در سال های پس از اجرای طرح هدفمندی یارانه ها رهنمون می سازد.

شاخص‌های تعامل:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesدانلود 196 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesاستناد 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resourcesمرجع 0
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