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This paper investigates implementation of upwind compact implicit and explicit high-order finite difference schemes for solution of the level set equation. The upwind compact implicit and explicit high-order finite difference schemes are well-known techniques to descritize spatial derivatives for convection term in hyperbolic equations. Applying of upwind high-order schemes on the level set equation leads to less error and CPU time reduction compared to essential non-oscillatory (ENO), weighted essential non-oscillatory schemes (WENO), and even different particle level set methods. The results indicate the error based on area loss decreases drastically with applying high-order upwind,... 

This work simulates the turbulent boundary layer of an incompressible viscous swirling flow through a conical chamber. To model the pressure gradient normal to the wall, the radial and tangential velocity components across the boundary layer have been calculated by both the integral and numerical methods. The numerical solution is accomplished by finite difference, based on the finite volume method. The results show that the radial and tangential boundary layer thicknesses depend on the velocity ratios, Reynolds number and nozzle angle. The peak of radial and tangential boundary layer thicknesses are located at zL≈0.2 and zL≈0.8 from the nozzle inlet, respectively. Due to the short length of... 

In this paper, we consider the problem of computing the visibility polygon (VP) of a query point q (or VP(q)) in a scene consisting of some obstacles with total complexity of n. We show that the combinatorial representation of VP(q) can be computed in logarithmic time by preprocessing the scene in O( n4logn) time and using O( n4) space. We can also report the actual VP(q) in additional O(|VP(q)|) time. As a main result of this paper, we will prove that we can have a tradeoff between the query time and the preprocessing time/space. In other words, we will show that using O(m) space, we can obtain O( n2log(m/n)/m) query time, where m is a parameter satisfying n2≤m≤ n4. For example, when m= n3,... 

There are different choices for auction and settlement mechanisms in electricity markets; however, selecting the appropriate mechanisms is too hard. Traditionally, the offer cost minimization (OCM) mechanism that minimizes the total offer cost is used as the clearing mechanism, and payments are calculated based on locational marginal prices (LMPs). Under this setup, the clearing and settlement mechanisms are inconsistent, since the minimized cost is different from the total payment cost. Some recent studies have proposed the payment cost minimization (PCM) mechanism. However, the discussion is still open, and different aspects of these mechanisms are yet needed to be analyzed. This paper... 

This paper considers the problem of computing the weak visibility polygon (WVP) of any query line segment pq (or WVP(pq)) inside a given simple polygon P. We present an algorithm that preprocesses P and creates a data structure from which WVP(pq) is efficiently reported in an output sensitive manner. Our algorithm needs O(n2log n) time and O(n2) space in the preprocessing phase to report WVP(pq) of any query line segment pq in time O(|WVP(pq)|+log2 n+κlog2 (nκ)), where κ is an input and output sensitive parameter of at most |WVP(pq)|. We improve the preprocessing time and space of current results for this problem [11,6] at the expense of more query time  

The main focus of this study is on reserve market settlement in an electricity market with marginal pricing scheme as the pricing mechanism. Following a day-ahead market clearing, the marginal prices are found using the appropriate Lagrange multipliers as the bi-products of the optimisation process. The payments to energy and reserve providers can then be found based on these prices. However, it is hard to find an appropriate settlement scheme that provides the fair and justifiable consumer payments based on marginal pricing scheme considering the actual reserve functions in power systems. In this study, a reserve marginal pricing that is based on a proper reserve marginal price definition... 

In this paper we study combinatorial segment visibility, and show how to compute and maintain it as the observer moves in the plane. There are n non-overlapping convex objects in the plane, and we have a segment observer among them. We first consider static case of the problem, in which the observer and objects are static, and then we study dynamic case of the problem, in which the observer can move among obstacles. ©2009 IEEE  

In this paper we define topological segment visibility, and show how to compute and maintain it as the observer moves in the plane. There are n non-intersecting line segment objects in the plane, and we have a segment observer among them. As the topological visibility of a line segment has not been studied before, we first consider static case of the problem, in which the observer and objects are static, and then we study dynamic case of the problem, in which the observer can move among obstacles  

In this paper we consider the problem of computing the weak visibility polygon of a query line segment pq (or WVP(pq)) inside a given polygon P. Our first algorithm runs in simple polygons and needs O(n3 log n) time and O(n3) space in the preprocessing phase to report WVP(pq) of any query line segment pq in time O(log n + |WVP(pq)|).. We also give an algorithm to compute the weak visibility polygon of a query line segment in a non-simple polygon with h ≥ 1 pairwise-disjoint polygonal obstacles with a total of n vertices. Our algorithm needs O(n2 log n) time and O(n2) space in the preprocessing phase and WVP(pq) in query time of O(nh’ log n + k), in which h’ is an output sensitive parameter... 

In this paper we consider the problem of computing the weak visibility polygon of a query line segment pq (or (Formula presented.)) inside a given polygon (Formula presented.). Our first algorithm runs in simple polygons and needs (Formula presented.) time and (Formula presented.) space in the preprocessing phase to report (Formula presented.) of any query line segment pq in time (Formula presented.). We also give an algorithm to compute the weak visibility polygon of a query line segment in a non-simple polygon with (Formula presented.) pairwise-disjoint polygonal obstacles with a total of n vertices. Our algorithm needs (Formula presented.) time and (Formula presented.) space in the... 

The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In... 

Among the different options available for market clearing mechanisms, offer cost minimisation mechanism is being used in most electric power markets. The payments are then calculated based on locational marginal prices (LMPs). The payments can be significantly higher due to the inconsistency of the clearing and pricing mechanisms. Payment cost minimisation (PCM) mechanism which directly minimises the total payment has been recently proposed to solve this issue. In this study, an auction mechanism is proposed for payment to suppliers minimisation (PSM) based on the LMPs instead of consumers payment minimisation (CPM). Using a proper formulation for the supply side reserve LMPs, the complete... 

The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In... 

In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of 1010 < Ra < 1012. The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic, and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling, and industrial cold box packages. Governing equations,... 

In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of 1010 < Ra < 1012. The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic, and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling, and industrial cold box packages. Governing equations,... 

Societies today have come closer together as a result of the development of communication technologies and the greater ease with which business is transacted. Consequently, technological tools and devices are being transferred from industrial societies to other countries at dazzling speeds the transfer of technology to non-industrialized societies with their own histories, civilizations, and backgrounds has led to the emergence of cultural issues and conflicts that are specific to the modern period and that had not existed prior to this period. In this article, we have reviewed the ideas of Don Ihde, a leading contemporary philosopher who has done much work in the field of the philosophy of... 

Many important problems in Computational Geometry needs to perform some kind of angle processing. The Polar Diagram [4] is a locus approach for problems processing angles. Using this structure as preprocessing, one can eliminate exhaustive searches to find objects with smallest angle. Handling data in change is a significant concept in Computer Science. One of the design and analysis tools used in the modeling of moving geometric objects is the kinetic data structure (or KDS) framework Kinetic Data Structure is a framework for maintaining a certain attribute of a set of objects while moving in a continuous manner. In this paper, we use the notion of kinetic data structure to model the... 

In this paper, two models are developed to predict liquid pressure drop and velocity profile in the wicks of concentric annular heat pipes. A steady-state incompressible laminar flow is modeled in the wicks based on velocity and pressure mean values by the extended Darcy-Brinkman model. The corresponding one- and two-dimensional governing equations are solved analytically and numerically, respectively, in the range of low to moderate radial Reynolds numbers. It has been found that there is a difference, about 12% in the worse case, between the total pressure drops of the two models. Whereas, the predicted total pressure drop by the one-dimensional model and that of the Darcy model are in... 

In the present study criterion for local thermal equilibrium assumption is studied. It concerns with the fluid flow and heat transfer between two parallel plates filled with a saturated porous medium under non-equilibrium condition. A two-equation model is utilized to represent the fluid and solid energy transport. Numerical Finite Volume Method has been developed for solving coupled energy equations and the Non-Darcian effects are considered for description of momentum equation. The effects of suitable non dimensional parameters as Peclet number and conductivity ratio has been studied thoroughly. A suitable non dimensional equation proposed in wide range of Peclet number and conductivity...