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Author(s): 

Pourhaji S. | Pourmand A.

Issue Info: 
  • Year: 

    2024
  • Volume: 

    53
  • Issue: 

    4
  • Pages: 

    291-297
Measures: 
  • Citations: 

    0
  • Views: 

    44
  • Downloads: 

    5
Abstract: 

In this paper, recommended spiral passive micromixer was designed and simulated. spiral design has the potential to create and strengthen the centrifugal force and the secondary flow. A series of simulations were carried out to evaluate the effects of channel width, channel depth, the gap between loops, and flowrate on the micromixer performance. These features impact the contact area of the two fluids and ultimately lead to an increment in the quality of the mixture. In this study, for the flow rate of 25 μl/min and molecular diffusion coefficient of 1×10-10 m2/s, mixing efficiency of more than 90% is achieved after 30 (approximately one-third of the total channel length). Finally, the optimized design fabricated using proposed 3D printing method.

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Writer: 

مهدی-جلالی

Issue Info: 
  • End Date: 

    مهر 1384
Measures: 
  • Citations: 

    0
  • Views: 

    245
  • Downloads: 

    0
Keywords: 
Abstract: 

قطعه فوق یک قطعه استراتژیک در صنعت حفاری است که دانش فنی آن را جهاد تهیه کرده است. دانش فنی این قطعه شامل مشخصات مکانیکی و متالورژیکی، نقشه فنی و نقشه بازرسی و همچنین اسکوپ بازرسی است.

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Issue Info: 
  • Year: 

    2024
  • Volume: 

    13
  • Issue: 

    25
  • Pages: 

    3-32
Measures: 
  • Citations: 

    0
  • Views: 

    15
  • Downloads: 

    0
Abstract: 

In this research, in order to investigate the effect of the piezoelectric patch which is used as a sensor or actuator in rotating flexible structures such as a helicopter blade, the free vibrations of the rotating rectangular sheet with and without the piezoelectric patch have been presented. First-order shear deformation theory is considered for plate displacement and piezoelectric field. Considering the effect of Coriolis acceleration, centrifugal acceleration and centrifugal in-plane forces, the equations of motion are derived from Hamilton's principle and the electromechanical couple equation is obtained from Maxwell's equation. For piezoelectric, two electrical conditions, open circuit and closed circuit, which are used in sensors and actuators, respectively, have been considered. The equations are discretized with the help of the Numerical method of generalized differential squares and the matrices of inertia mass, eccentricity, Coriolis and stiffness matrix are obtained. Natural frequency values for beam and rotating plate have been compared in Abaqus software. Also, the values obtained from the Numerical solution in MATLAB have been verified with articles and ABAQUS, which have high accuracy. The effect of parameters such as hub radius, rotation speed, sheet thickness, aspect ratio, piezoelectric patch thickness and applied voltage on the natural frequency of the system has also been investigated.

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Issue Info: 
  • Year: 

    2023
  • Volume: 

    53
  • Issue: 

    2
  • Pages: 

    168-178
Measures: 
  • Citations: 

    0
  • Views: 

    105
  • Downloads: 

    18
Abstract: 

Plastic hinge properties play a crucial role in predicting the nonlinear response of structural elements. The plastic hinge region of reinforced concrete normal beams has been previously studied experimentally and analytically. The main objective of this research is to evaluate the behavior of the plastic hinge region of reinforced concrete deep beams and its comparison with normal beams through finite element simulation. To do so, ten beams contain six deep beams, and four normal beams, under concentrated and uniformly distributed loading, are investigated. Lengths in the plastic hinge region involving curvature localization, rebar yielding, and concrete crushing zones are studied. The results indicate that the curvature localization zone is not suitable for the prediction of plastic hinge length in reinforced concrete deep beams. Based on the results it can be stated that in simply supported normal beams the concrete crushing zone is focused on the middle span, but in simply supported deep beams by creating a compression strut between loading place and support, the concrete crushing zone spreads along the compression trajectory. The rebar yielding zone of simply supported beams increases as the loading type is changed from the concentrated load at the middle to the uniformly distributed load.

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Issue Info: 
  • Year: 

    2013
  • Volume: 

    13
  • Issue: 

    28
  • Pages: 

    113-135
Measures: 
  • Citations: 

    1
  • Views: 

    2100
  • Downloads: 

    0
Abstract: 

The Numerical taxonomy technique is a multi - criteria decision making technique for evaluating and ranking alternatives, and is widely used in areas of planning and development. This model like the other multi- criteria decision making models has some drawbacks, the most important criticism on this method is uniform presuming the indicators and being the indicators in same direction. Therefore, the objective of this paper is presenting appropriate methodology for improvement of this method and eliminating the limitations of this technique and introducing the modified taxonomy model. In the following of introducing the modified model, for better representing the difference, the two models is used to assess the level of development in rural areas of Mazandaran province. The research method is descriptive and applied, and libraries based on data of the 1385 Census. Results showed the more accurate the modified model compared with the contemporary taxonomy model. Development coefficient (Fi) and rank in these models have substantially different. Based on Numerical taxonomy rural areas of Ghaemshahr Township with a grade of 0.455 are in rating 1 and rural areas of Ghaloga Township with a grade of 0.455 are in rating 3, Whereas with the modified model that to weight important indicators and also the direction of indicators (being positive or negative) is significant, Levels of development in rural areas of Ghaloga Township with a grade of. 396 to rating 1 and Ghaemshahr Township to rating 2 change.

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Issue Info: 
  • Year: 

    2004
  • Volume: 

    2
  • Issue: 

    4
  • Pages: 

    0-0
Measures: 
  • Citations: 

    0
  • Views: 

    350
  • Downloads: 

    0
Abstract: 

A two-dimensional Numerical model has been developed to study wave breaking on a sloping beach. The basic elements of Numerical model are Reynolds Averaged Navier-Stokes (RANS) equations that describe the mean flow motion of a turbulent flow; a k turbulence closure model that describes the turbulent transport and dissipation process; an efficient technique (VOF- Volume Of Fluid method) for tracking the free surface motion; and a new scheme developed by Lin and Liu (1999) for wave generation. Shoaling, breaking and overturning of solitary wave on a slope of 1/16 have been studied with the main emphasis on turbulence characteristics. Turbulence characteristics i.e., turbulence kinetic energy, k; turbulence dissipation rate, ; turbulence production, pr; turbulence eddy viscosity, vt; and their spatial distribution during the breaking process have been discussed in great details. Spatial distribution of turbulence characteristics and the order of magnitude have been found to be in agreement with existing experimental and Numerical studies. The main characteristic of plunging breaking waves, the shoreward advective transport of turbulence, has also been investigated and Numerically proved.

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Journal: 

Issue Info: 
  • Year: 

    2007
  • Volume: 

    20
  • Issue: 

    3 (76 IN AGRONOMY AND HORTICULTURE)
  • Pages: 

    71-79
Measures: 
  • Citations: 

    0
  • Views: 

    1479
  • Downloads: 

    0
Abstract: 

Plant development can be defined as a programmed qualitative change in plant form, which leads plant to maturity, and researchers call it as phasic development or phenology. Recognizing the timing of occurring each development stage is necessary for managing system in order to yield increment. The timing of occurring development stages depend on climate, genotype specifications and sowing date then determination of these times in different regions is difficult and it is only possible through the using of crop simulation models which can predict the timing of occurrence each development stage by integrating effective factors. The model was constructed based on linear equation of plant temperature response. In order to model evaluation two experiments were carried out in agricultural and natural resources research center of Khuzistan in 2003-2004 and 2004-2005 cropping years. Wheat development stages were determined based on Kirby and Appleyard’s scale by stereoscopic microscope and required GDD for each development stage as well. The constructed model was calibrated and run for simulation. Comparison of simulated and observed data showed that the model can strongly predict wheat development stages.

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Author(s): 

Tohidi Nasim | Dadkhah Chitra

Issue Info: 
  • Year: 

    2023
  • Volume: 

    12
  • Issue: 

    1
  • Pages: 

    74-88
Measures: 
  • Citations: 

    0
  • Views: 

    54
  • Downloads: 

    0
Abstract: 

Today, one of the most widely used natural language representation methods is meaning representation for text processing in different systems. Meaning representation methods have had many applications in the field of natural language processing in recent years, including automatic text summarization systems and question and answer systems, etc. Many text expressions may be different in terms of grammatical structure, but they are the same in terms of meaning, so how to apply a single and uniform meaning to them is one of the challenges of text processing. The main goal of this paper is to design an Integrated Semantic Representation (ISR) model for natural language. The proposed model, while maintaining its simplicity in annotation and understanding, does not depend on specific natural language features or on syntactic and lexical structure. In this regard, several examples in both English and Persian language, which have different in terms of written and grammatical structure, are presented in this paper. Moreover, by using the proposed model, the same representation is provided for texts with the same meaning and different grammatical structure. The proposed model is designed in graph and list format is recommended to annotate its corpuses. One of the main features of this model is that it can represent semantic relations at both sentence-level and document-level and is able to represent complex and important linguistic phenomena such as aspect, tense, and quantification. The simplicity of the proposed model helps to avoid making language processing slow or complicated in various applications, and the preparation of structures based on this model for different natural languages will not be too complicated, so that it can be used both for natural languages with low resources and for those with various resources. Further, features of the proposed model are compared with one of the most important related works.

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Writer: 

راسخ پریوش

Issue Info: 
  • Year: 

    1391
  • Volume: 

    4
Measures: 
  • Views: 

    746
  • Downloads: 

    0
Keywords: 
Abstract: 

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Issue Info: 
  • Year: 

    2022
  • Volume: 

    7
  • Issue: 

    2
  • Pages: 

    155-179
Measures: 
  • Citations: 

    0
  • Views: 

    171
  • Downloads: 

    30
Abstract: 

Purpose: Resilience in start-ups is a challenging issue that has caught the attention of policymakers and business owners. The present study is an attempt to provide a model for designing the resilience model of start-up businesses as a path to the future of start-up businesses. Method: This research is practical in terms of purpose and from the perspective of data collection is a qualitative research that has been done by content analysis method. The data collection method is semi-structured interview. Interviews with participants continued until they reached the theoretical saturation point, which was achieved by conducting 15 interviews. Participants were selected by snowball and purposeful method and data analysis was done through three coding steps (open, axial, selective) with MAXQDA2020 software. Findings: Based on the research results, the components of "cognitive resilience, financial resilience, adaptive resilience" as well as the effective organizational factors of "precedent, drivers and boys and resilience consequences" were identified. In this research, foresight and futures studies were identified as the drivers of resilience of start-up businesses. Conclusion: Resilience enables businesses to respond effectively to the dynamic conditions of their environment and maximize their competencies through strategic foresight and as a result gain more value than their competitors in the field of business. In this regard, the integration of foresight in the process of business resilience can be suggested as a facilitator of drivers.

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