Search published articles


Showing 43 results for Expansion


Volume 0, Issue 0 (2-2024)
Abstract

Among the lexical units of a language, all of which can be subjected to semantic expansion according to selection and combination, verbs are quite susceptible to radial and semantic expansion due to their nature. This article tries to use the cognitive approach to investigate the semantic expansion of the simple triad form of the event "Zarb" in the Arabic language. And in a descriptive-analytical way, while enumerating the marginal expansions of this verb, explain how they are produced and also the semantic sharing relationship between the derivatives of the same root. About 80 usages were extracted from the most advanced to the latest Arabic dictionaries for the event "Zarb", which, excluding similar usages, resulted in 32 radial meanings for this event. The result showed that the existence of a semantic relationship between the derivatives of a word can be confirmed in the light of the derivational property of the Arabic language. Therefore, from the most unmarked meaning of "stroke" to its metaphorical expansions, each of them conveys the concept of "pressure and force" in a way. Therefore, the claim that the meaning of "beating" is late in this event is questionable. Also, most of the marginal expansions of the verb "to multiply" are the product of the change in the most frequently used elements accompanying this event, i.e. space scenes. In addition, in the virtual expansion of the event "hit", the necessary-necessary interest and the cause-cause have more frequency in producing the radial meanings of this event.
 

Volume 0, Issue 0 (3-2023)
Abstract

Urban growth boundaries are considered one of the key tools for controlling and managing the physical development of metropolitan areas. Uncontrolled and unplanned expansion in these regions has become a major challenge for urban and regional planners and managers, as this process leads to the destruction of agricultural lands and natural resources. The aim of this research is to simulate and assess future changes in growth boundaries in the Isfahan metropolitan area with the goal of preserving environmental resources and controlling physical expansion. In this regard, by adopting a positivist approach that follows an analytical and measurement-driven process, satellite imagery was utilized to assess changes in the physical expansion of the Isfahan metropolitan area. Artificial neural networks and machine learning algorithms were employed to predict the extent of future physical growth, and the projected growth boundaries were delineated. The research findings indicate that the Isfahan metropolitan area has experienced significant uncontrolled expansion, particularly in terms of physical development, over recent decades, and the reduction of agricultural and natural lands has become one of its major challenges. Based on the conducted simulations, the proposed growth boundaries can serve as an effective tool for managing and planning urban-regional development and preventing further degradation of natural resources and lands.

 

Volume 4, Issue 2 (7-2013)
Abstract

One of the stages in the contemporary linguistics, based on which the linguists recognize a special position for speaker, is the “discourse analysis”. In this innovative linguistic perspective, the individual indicator, which influence on producing the texts, constitutes a new area in pragmalinguistic researches. Though we can pursue the history of acquaintance of linguistics with deixis in the rhetorical tradition of Islam, where the term appears by means of struggling, which arises from the process between grammar and rhetoric. Islamic grammarians are interested into internal context (co-text) & ask if there is a cohesion between the propositional members of the text and its external context (context of situation). Whereas, the rhetoricians study about the illocutionary force(s) of the utterances through corresponding this force with the context of situation. But among these scientists, there are others who synthesize between co-text & context simultaneously. They respect the deviations in grammatical principles in order to achieve the illocutionary or force(s) of utterances. This article argues some deixis in Ney-Nameh, such as personal pronouns, demonstratives, spatial-temporal indicators & expansion-contraction in discourse to evaluate the importance of speaker’s function in the above-mentioned discourse. In fact, this article would reply to this question that if by means of the deixis, we can go out of utterances’ level to appreciate the illocutionary forces of a total text and evaluate the correspondence of co-text and context.  

Volume 6, Issue 1 (12-2006)
Abstract

This paper presents a framework for long term transmission expansion planning in competitive, electricity markets. Transmission lines and phase shifters are taken into account as expansion options. Maximization of the network users' benefits, with satisfying security constraints are considered as the criterion for transmission expansion planning. The elements of the objective function are the benefits of each network. The proposed model is as a non-linear mixed-integer programming (NLMIP) optimization problem. A GA (Genetic Algorithm) based method and quadratic programming (QP) approach is used to solve the problem. The discrete decision-making variables of the expansion plan are optimized by genetic algorithm, while QP optimizes the continuous variables.

Volume 9, Issue 1 (1-2009)
Abstract

Transmission expansion planning (TEP) is one of the most important parts in power systems. Restructuring of power system has changed the traditional planning objectives and introduced new challenges in the field of TEP. In this new environment, the comprehensive and precise design based on electricity market criteria in planning horizon is indispensable. In this paper a new algorithm is proposed for dynamic transmission expansion planning in deregulated environment. In this method, investment cost and operation cost are considered as market based economic criteria, and average load curtailment cost in contingencies is considered as a reliability criterion from market players' viewpoint. Congestion cost is also used as a competition index between market participants. The combination of Genetic Algorithm (GA) and fuzzy satisfying method is used for solving TEP problem. At last the proposed method has been tested on 8-bus network and IEEE 30-bus network.

Volume 10, Issue 2 (7-2010)
Abstract

Network expansion studies normally offer new power lines, new substations or expansion of existing substations. They are generally proposed based on technical requirements, but financial restrictions are not considered. Because of financial restrictions, ranking of network expansion plans is required. In this paper an algorithm for such ranking, based on technical and financial view points and proposes suitable parameters. This algorithm may be used to compliment static or dynamic expansion planning studies of electric power networks.

Volume 10, Issue 4 (1-2011)
Abstract

In this paper, first, a new criterion, titled “surplus percent of the customers” is defined for static transmission expansion planning in restructured power systems. Then by a simple example, the new criterion is compared with some already presented market-based criteria and it is shown that the new criterion can realistically evaluate the transmission network expansion from the market view. In this paper the bid of market participants (producers and consumers) to sell and buy power are considered as random variables with known probability density functions. Then the expectation of the surplus percent is introduced as an index for measuring the competitiveness of each transmission expansion plan. Then a least-investment cost expansion plan that increases the surplus percent to its ideal or near ideal value is searched. In this paper a fast method is also presented to calculate the expectation of the surplus percent using Monte-Carlo simulation with a predefined approximation. The results of applying the proposed method are illustrated for an example 8-bus power system.

Volume 12, Issue 4 (11-2012)
Abstract

In this research, a novel method to decrease macro-residual stresses of laminated composites by adding carbon nano-fiber (CNF) is proposed. To this end, using micromechanical and modified micromechanical approaches, coefficient of thermal expansion (CTE) and Young’s modulus of carbon nano-fiber reinforced polymer are calculated. Then using this enhanced matrix, longitudinal and transverse of thermal expansion and Young’s modulus of a CNF/glass/epoxy unidirectional lamina in presence of CNF are obtained. Finally, using the classical lamination theory (CLT), macro-residual stresses for CNF/glass/epoxy laminated composites are obtained. The results explain how CNF can result in reducing macro-residual stresses in nano particle filled laminated composites. The results for both cross ply and angle ply glass/epoxy laminated composites are presented and show that adding CNF through the matrix can decrease macro-residual stresses in each plies up to about 30%. The main reason for the decrease in residual stresses are due to the sever decrease of coefficient of thermal expansion of the unidirectional ply.

Volume 12, Issue 4 (3-2013)
Abstract

This paper presents a probabilistic confidence-interval based method for optimal placement of shunt capacitors in distribution networks by considering probabilistic characteristics of loads. The main objective function are reducing loss and improving the voltage profile. Backward forward sweep method has been employed to obtain the power flow results in distribution system. In addition, Integer Harmony Search Algorithm has been used to solve the optimization problem. The probabilistic aspects of problem have been solved using point estimation (PE) method. The novelty of this paper is introducing a confidence interval index using Gram-Charlier expansion. This index shows the risk of system to violate its security constraints when loads are considered as stochastic random variables. Using this index, planners can find the optimal sitting and sizing of capacitors in distribution systems based on their desired level of risk. Verification of the proposed method has been tested on 33-bus radial distribution system. Results demonstrate the effectiveness and merits of the proposed method.

Volume 13, Issue 2 (5-2013)
Abstract

It is well known that ground surface with irregular topographic features causes complicated seismic responses. The complex seismic response is mainly caused by wave scattering. In this study, for a homogeneous, isotropic, linearly elastic half-space, the formulation of a two-dimensional SH-wave field based on the direct boundary element method and Neumann series expansion is developed. By discretizing the ground surface to boundary elements, the boundary integral equation is formulated into a general matrix form. This general matrix form is then reduced to a more efficient form, which considerably reduces the size of the computational matrices using Neumann series expansion. For this purpose, a Fortran computer program is developed, whose accuracy and feasibility in the frequency domain is shown by some numerical analyses conducted for grounds with semicircular convex and concave, and symmetrical V-shaped canyon topographical configurations. Comparing the results of the present study with those available in the literature shows the accuracy of the present study by just considering two first terms of Neumann series expansion. The minor differences of the results of the present research with other reseach results may be assigned to the number of terms of Neumann series expansion and the order of used boundary elements. In other words, if the number of terms of Neumann series expansion and the order of used boundary elements incease, the accuracy of the numerical results may enhance. Based on the results of the present research for various parameters of different two-dimensional canyons, the following conclusions may be obtained: When the exciting frequency increases, the wave-length decreases. As a result, the violence effects of incident wave due to canyon effects may be significant for a given canyon. Moreover, the displacement field of various canyon points follows more complicated pattern. On the other hand, for smaller exciting frequencies with larger wave-lengths, the canyon effects as the main cause of disturbation source are not so remarkable, and the displacement field of various canyon points are smoother. The effects of incident wave angle is also remarkable on the disturbation patterns of displacement field of different canyon points. When the angle increases, the triangle canyons experience more complicated patterns compared to semicircular canyons. Analyses'''' results show important effects of shape and depth of various canyons. These effects are more considerable when depth''''s variations are remarkable in comparison with the wave-length of incident wave. Furthermore, the mentioned effects are functions of frequency and angle of incident wave.

Volume 13, Issue 3 (6-2013)
Abstract

The main object of current study is investigation of instability threshold of flow in a gradual expansion from symmetric to asymmetric situations. The expansion ratio is 1:3 and expansion angles are 30, 45, 60 and 90 degree. Discretization of governing equations is performed using finite volume method based on PISO algorithm on a staggered mesh. The CFD code is validated based on the results of sudden expansion reported in previous works. Here, the effects of expansion angle and Reynolds number on flow instability in transition from symmetric situation to two and three asymmetric vortices are investigated and the first and second critical Reynolds numbers are obtained. The bifurcation diagrams of vortices and velocity profile in centerline are plotted for each case and the effects of instability on flow field are discussed based on them. Unlike the previous studies which have been focused on the planar flow in sudden expansions, the flow instability in gradual expansions with different expansion angles is investigated which is the main innovation of current study.
Nader Vazifeh Shiran, Masoud Soleimani, Yousef Mortazavi, Saeed Kaviani, Hassan Aboulghasemi, Mahin Nikougoftar,
Volume 13, Issue 3 (8-2010)
Abstract

Objective: Allogeneic transplantation with umbilical cord blood (UCB) in adult recipients is limited mainly by a low CD34+ cell dose. To overcome this shortcoming, human placenta as a novel source of human mesenchymal progenitor cell (MPC)- unrestricted somatic stem cells (USSC)- was incorporated in an attempt to expand CD34+ cells from UCB. To provide a similar environment in vitro, we coated DBM scaffold with USSC cells as the matrix for support UCB-CD34+ cells growth. Materials and Methods: Human placenta USSC was isolated and characterized by morphologic and immunophenotypical analysis. UCB CD34+ cells were expanded by coculture with placental USSC in 2D and 3D environment. Suitable aliquots of cells were used to monitor cell production, clonogenic activity, and long-term culture-initiating culture (LTC-IC) output. Results: Ex vivo expansion of UCB hematopoietic cells, when cultured in different 2D conditions and 3D condition for 3 weeks, was significantly enhanced, the total cell count increased within the 28-day period. For total CFC, the highest CFC expansion was observed at day 14. Flow cytometry analysis of the percentage of CD34+ cells showed a decline in USSC cocultures in 2D and 3D condition at 3 weeks. Conclusion: These results strongly suggest that human USSC may be a suitable feeder layer for expansion of hematopoietic progenitors from UCB in vitro and USSC- coated DBM can therefore provide an ex vivo mimicry of bone marrow by enhancing of surface/ volume ratio and feeder layers,recapitulate the desired niche, and provide a suitable environment for stem cell expansion and differentiation.

Volume 14, Issue 1 (4-2014)
Abstract

- In this study, the shrinkage behavior of knitted fabrics during drying is studied .To this end, a model is presented to predict the knitted fabric length changes during the drying process. In order to model the shrinkage behavior, a 1DOF model consisting of a mass, a linear spring and a linear dashpot was used. Considering that the fabric is wet, mass is time dependent and Three-order Straight Forward Expansion method is used to solve nonlinear equations of motion. The results of the model were compared with the experimental results of five samples with different courses density. The results show that the proposed model is capable to predict the length changes of the center of the mass during the process of drying and after that. Error rate is about ten percent for the samples with less Loop length. But by increasing the length of the loop, error rates increases.

Volume 14, Issue 1 (4-2014)
Abstract

This paper presents an experimental study on the mold design and the effect of processing parameters on the expansion of foam injection molded parts. Limitation in foam expansion is a primary challenge in foam injection molding process. In this study a novel approach in mold design is introduced to take advantages of concepts such as counter-pressure and mold opening to further extend the expansion range. A modular sheet mold with a rectangular cavity and a fan gate was designed and manufactured. The mold includes a main cavity, the thickness of which could be varied, connected to an overflow channel via a secondary gate, the size of which was also varied in this research. The investigated parameters were part thickness, secondary gate width. Full factorial test experiments were carried out in this research work. The results indicated the high effectiveness of the proposed approach in further reducing the foamed part weight. For the parts with a larger thickness, a noticeable decrease in bulk density and an increase in cell population density along with an improvement in cellular structure uniformity were observed.

Volume 14, Issue 1 (5-2014)
Abstract

Transmission network expansion planning is a challenging problem with the aim to determine the type, location, and time of the equipment to be added to the existing transmission network in order to desirably meet the increasing load demand. On the other hand, reactive power sources are the other important components of the power system, which are used improve voltage profile and maintain the system stability. This paper, presents a comprehensive AC load flow based framework for concurrent expansion planning of transmission networks and reactive power resources. Although major advances have been made in optimization techniques, finding an optimal solution to a problem of this nature is still challenging. Using some linearization techniques, a mixed-integer linear programming (MILP) model for transmission expansion and reactive power planning is proposed. In order to show the influence of the concurrent transmission network expansion and reactive power resources planning in reducing investment costs, simulation studies and analysis of the numerical results are carried out on the Garver 6-Bus and the standard IEEE 24-bus test system.
 

Volume 14, Issue 15 (3-2015)
Abstract

The significance of research on the specifications of the supercritical fluids becomes more evident with respect to the increase of their application in different food, chemical, polymer, oil, and gas industries. One of the major specification, is the coefficient of thermal expansion (β) where the ideal gas model was used in most of the processes in which this component is applied; the weakness of this model is that it is unable to make an accurate prediction of this parameter within the range of critical point. For this reason, in this study to determine the coefficient of thermal expansion, Redlich–Kwong equation of state is used and a new relation as a function of temperature, pressure, and compressibility is obtained. Comparing behavior of the curves obtained from this relation with experimental data, exhibits a favorable consistency. Moreover, natural convection heat transfer of the supercritical fluid in a vertical channel at constant temperature walls conditions were considered numerically. The governing equations were solved using the finite-volume method (FVM) and based on the SIMPLE Algorithm. After validation with the earlier studies. Then, the flow and heat transfer characteristics based on the obtained coefficient of thermal expansion were compared with the ideal gas assumptions. Finally, the trend of change in heat transfer coefficient away from the critical point was studied.

Volume 15, Issue 2 (4-2015)
Abstract

In the present study, in order to evaluate the elastic displacement field and subsequently the fracture parameters within the isotropic homogeneous elastic solids with the edge or interior cracks, the extended finite element method with level set technique was used to avoid the disadvantages associated with the standard finite element method. An overdeterministic least squares method was utilized to determine the crack stress intensity factors as well as the coefficients of the higher order terms in the Williams' asymptotic series solution for structures containing crack in various modes of failure by fitting the series solution of displacement fields around the crack tip to a large number of nodal displacements obtained from the extended finite element method. For validating the results, several cracked specimens subjected to pure mode I, pure mode II, and mixed modes I/II loading were performed. Comparisons with results available from the literature obtained by the other formulations reveal the efficiency and the simplicity of the proposed method and demonstrate the capability of it to capture accurately the crack stress intensity factors and the coefficients of higher order terms.

Volume 15, Issue 2 (7-2015)
Abstract

Currently, large dams in the world, due to high amount of sediments in the reservoir, especially around the intake, have operational problems. One of the solutions for this problem is pressure flushing which is an efficient method for extracting the accumulated sediments behind the dams, where, the valves and turbines are placed over there. In this type of flushing, previously deposited sediments are removed by opening the bottom outlets. Sediment is scoured and a funnel shaped crater is created in the vicinity of the bottom outlet opening. Amount of the flushed sediments depend on many parameters such as water depth on the bottom outlets, discharge released through bottom outlets, size of the outlets, geometry of the reservoir, size and kind of the deposited sediments in the reservoir. But the extent of flushing impact range is limited. On the other hand, since in this method, the waste of water in the reservoir is relatively low; therefore, an appropriate solution for increasing the efficiency of the pressure flushing process, would be able to increase the dam’s lifetime with minimal amount of water waste. In laboratory experiments carried out in this study, the effect of expansion of bottom outlet channel within the reservoir is investigated on the volume and dimensions of the flushing cone. In order to achieve the objective of this study, experiments done by means of a physical model with length 7.1 m, wide 1.4 m and height of 1.5 m. Experiments performed with three bottom outlet channel lengths 10, 20 and 30 cm, three water heights 47.5, 55 and 64.5 cm over center of outlet and three discharge flows equal to 1, 2 and 3 (l/s) for each height. Preliminary results showed that, expansion of bottom outlet channel within the reservoir has positive and tangible effects on the size of the flushing cone. As, with the expansion of bottom outlet channel within the reservoir, new hydraulic conditions are introduced, which affects the mechanism of flushing and by increase in the length of outlet channel, dimension of flushing cone increases. But the rate of increase in dimensions decreases with increment in expansion amount. So the relative amount of bottom outlet channel expansion for 0.5, 1 and 1.5 times height of the sediment in the reservoir, leads to increase in flushing cone volume for average amount of 50, 74 and 96% compared to the case with the no developed bottom outlet channel. according to the experimental data, non-dimensional equations are derived for estimation of the flushing cone size. These equations show high regression coefficients and provide good estimations. Also the results indicate that, In the higher discharges of flow, effect of the expansion size of bottom outlet channel on the amount of the sediment discharged is high.

Volume 15, Issue 3 (5-2015)
Abstract

In this paper, Propagated modes in a three-layer adhesive joint are investigated regardless of wave generation source influence and also by taking into consideration it and low-attenuation modes are determined. In the beginning, lamb wave propagation in the adhesive joints is investigated using global matrix method and characteristic equation is derived by applying continuity and boundary conditions which are included traction-free boundary conditions on outer surfaces of the joints and continuity between layers. Phased velocity and attenuation dispersion curves in terms of frequency are obtained by numerical solution of the characteristic equation. Then, the source influence on wave field is investigated using normal mode expansion method. Average power flow of low-attenuation excited mode and its energy percent to the lamb wave total energy curves in terms of source parameters for specific frequency are obtained. These results are used to determine the suitable parameters of the source which are used to generate low-attenuation lamb wave mode. Finally, finite element simulation of lamb wave generation is performed to compare with the results of normal modes expansion method. The results indicate to generate M3 mode with low-attenuation level in the three-layer adhesive joint aluminium-epoxy-aluminium at frequency 0.25 MHz, suitable wedge angle is 16 degree and suitable transducer width is 20 mm.

Volume 15, Issue 4 (6-2015)
Abstract

Due to the diversity and width applications of polymeric fluids in various industries the investigation of viscoelastic fluids is noted by many researchers. In this study, non-creep flow of viscoelastic fluid has investigated inside planar channel with gradual expansion for the expansion ratio of 1:3. The laminar and incompressible flow of viscoelastic fluid has been simulated numerically using finite volume method and PISO algorithm. The nonlinear PTT rheological model has been applied to study effect of elasticity property on the length of vortices in polymeric fluid flow. The investigation of symmetric and asymmetric vortices length in a wide range of Reynolds and Weissenberg numbers is the main purpose of present study. The three angles of 30, 45 and 60 degrees have been considered for influence of the expansion angles on the length of vortices. The study of polymeric fluids flow through the planar channel with gradual changes in cross section (with expansion angles less than 90 degrees) is the innovation of this research. Also the critical values of first and second for Reynolds and Weissenberg numbers have been expressed in various expansion angles and furthermore length of second and third vortices has been presented as a function of Reynolds and Weissenberg numbers. The length of symmetric vortices decreases with increment of elastic property at all expansion angles for values of Weissenberg numbers less than one. Whereas the growth of expansion angle leads to increase in the length of symmetric and asymmetric vortices for low Reynolds and Weissenberg numbers.

Page 1 from 3    
First
Previous
1