Sharif Digital Repository

Test Driven Development (TDD), as a quality promotion approach, suffers from some shortages that discourage its usage. One of the most challenging shortcomings of TDD is the low level of granularity and abstraction. This may lead to production of software that is not acceptable by the end users. Additionally, exploiting of TDD is not applicable in the enterprise systems development. To overcome this defect, we have merged TDD with Model Based Testing (MBT) and suggested a framework named Model Based Test Driven Development (MBTDD). According to TDD, writing test cases comes before programming, and based on our improved method of TDD, modeling precedes writing test cases. To validate the... 

This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler-Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used for determination of aerodynamic loading on the wing. Combining these... 

Communication wire delay between multiple blocks is becoming a critical issue in System on Chip (SoC) design. Scheduling-based Latency-Insensitive Design (LID) is a method to alleviate wire delays by utilizing a central scheduling scheme for periodic clock gating of the blocks. The scheduling scheme resides in shift registers as sequences of '1' and '0' bits. In many systems, these sequences are too long, and have large area overhead. This problem indisposes the implementation of the scheduling based protocol. This paper proposes an algorithm that finds sequences with shorter lengths in comparison with the prior algorithm. On synthetic/random test cases, the algorithm gives 45% reduction on... 

This paper introduces two new compression methods. One of these methods is adaptive and powerful for the compression of hyperspectral data, which is based on separating the bands with different specifications by the histogram analyzes and new version of Binary Hybrid GA-PSO (BHGAPSO) and compressing each one with a different manner. The new proposed methods improve the compression ratio of the JPEG standards and save storage space the transmission system. The proposed methods are applied on different test cases, and the results are evaluated and compared with some other compression methods, such as lossless JPEG and JPEG2000  

Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) can lead to non-physical oscillations in the pressure and density fields when simulating incompressible flow problems. This in turn may result in tensile instability and sometimes divergence. In this paper, it is shown that this difficulty originates from the specific form of spatial discretization used for the pressure term when solving the mass conservation equation. After describing the pressure-velocity decoupling problem associated with the so-called colocated grid methods, a modified approach is presented that overcomes this problem using a different discretization scheme for the second derivative of pressure. The modified... 

Medical images include information about human body which are used for different purposes such as surgical and diagnostic plans. Compression of medical images is used in some applications such as profiling patient's data and transmission systems. Regard to importance of medical images information, lossless or near-lossless compression is preferred. Lossless JPEG, JPEG-LS and lossless version of JPEG2000 are few well-known methods for lossless compression. JPEG2000 is one of the latest and provides good compression ratio, however, it is complex [1]. In real time application which needs hardware implementation, low complex algorithm accelerates compression process. In this paper, a lossless... 

This paper uses a fourth-order compact finite-difference scheme for solving steady incompressible flows. The high-order compact method applied is an alternating direction implicit operator scheme, which has been used by Ekaterinaris for computing two-dimensional compressible flows. Herein, this numerical scheme is efficiently implemented to solve the incompressible Navier-Stokes equations in the primitive variables formulation using the artificial compressibility method. For space discretizing the convective fluxes, fourth-order centered spatial accuracy of the implicit operators is efficiently obtained by performing compact space differentiation in which the method uses block-tridiagonal... 

Benefitting from an analogy between compressible and incompressible governing equations, a novel dual-purpose, pressure-based finite-volume algorithm is suitably extended to simulate laminar mixing and reacting flows in low-Mach-number regimes. In our test cases, the Mach number is as high as 0.00326. Definitely, such low-Mach-number flows cannot be readily solved by either regular density-based solvers or most of their extensions. To examine the accuracy and performance of the extended formulation and algorithm, we simulate two benchmark cases including the mixing natural-convection flow in a square cavity with strong temperature gradients and the premixed reacting flow through annuli with... 

Detailed geological models of a reservoir may contain many more cells that can be handled by reservoir simulators due to computer hardware limitations. Upscaling is introduced as an effective way to overcome this problem. However, recovery predictions performed on a coarser upscaled mesh are inevitably less accurate than those performed on the initial fine mesh. Dual mesh method is an approach that uses both coarse and fine grid information during simulation. In the reconstruction step of this method, the equations should be solved numerically within each coarse block, which is a time consuming process. Recently, a new coarse-grid generation technique based on the vorticity preservation... 

The increase in complexity and rate of technological changes in modern software development has led to a demand for systematic methods that raise the abstraction level for system maintenance and regression testing. Model-driven development (MDD) has promised to reduce extra coding efforts in software maintenance activities using traceable change management. The research described in this paper presents a Z-notation-based framework, called delta-based regression testing (DbRT), for formal modeling of regression testing in the context of MDD. The framework proposes to propagate the changes from a software specification to testing artifacts in order to preserve consistency after system... 

Context Event-Driven Software (EDS) is a class of software whose behavior is driven by incoming events. Web and desktop applications that respond to user-initiated events on their Graphical User Interface (GUI), or embedded software responding to events and signals received from the equipment in its operating environment are examples of EDS. Testing EDS poses great challenges to software testers. One of these challenges is the need to generate a huge number of possible event sequences that could sufficiently cover the EDS's state space. Objective In this paper, we introduce a new six-stage testing procedure for event-driven web applications to overcome EDS testing challenges. Method The... 

Medical images contain human body pictures and used widely in diagnosis and surgical purposes [1]. Compression is needed for medical images for some applications such as profiling patient's data or transmission systems Due to the importance of the information of medical images, lossless or visually lossless compression preferred. Lossless compression mainly consists of transformation and encoding steps. On the other hand, hardware implementation of lossless compression algorithm accelerates real time tasks such as online diagnosis and telemedicine. Lossless JPEG, JPEG-LS and lossless version of JPEG2000 are few well known methods for lossless compression. This paper is focused on the... 

We investigate heat transfer between parallel plates separated by liquid argon using two-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. In molecular dynamics simulation of nanoscale flows through nanochannels, it is customary to fix the wall molecules. However, this approach cannot suitably model the heat transfer between the fluid molecules and wall molecules. Alternatively, we use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the... 

Wind power is a promising alternative in power generation because of its tremendous environmental and social benefits. Generation scheduling (GS) is more important in a power system integrating wind farms. Unlike conventional power generation sources, wind power generators supply intermittent power because of uncertainty in resource. This paper presents a fuzzy approach to the generation scheduling problem of a GenCo considering uncertainties in parameters or constraints such as load, reserve and available wind power generation. The modeling of constraints is an important issue in power system scheduling. A fuzzy optimization approach is an approach that can be used to obtain the generation... 

Secondary voltage control is used to re-adjust the reference values of automatic voltage regulators of generators. The performance of the secondary voltage control strongly depends on pilot node selection. In this paper the two proposed control laws for secondary voltage control are discussed and then an immune based algorithm is proposed to solve the optimal pilot node selection problem. The proposed algorithm is based on the clonal selection theory. The merit of immune algorithm lies in pattern recognition and memorization capabilities. Also, to provide independency of electrical zones a decoupling factor based on electrical distance concept is proposed. To verify the network observability... 

Numerical approximation based on different forms of the governing partial differential equation can lead to significantly different results for two-phase flow in porous media. Selecting the proper primary variables is a critical step in efficiently modeling the highly nonlinear problem of multiphase subsurface flow. A comparison of various forms of numerical approximations for two-phase flow equations is performed in this work. Three forms of equations including the pressure-based, mixed pressure-saturation and modified pressure-saturation are examined. Each of these three highly nonlinear formulations is approximated using finite difference method and is linearized using both Picard and... 

The multigrid method is one of the most efficient techniques for convergence acceleration of iterative methods. In this method, a grid coarsening algorithm is required. Here, an agglomeration scheme is introduced, which is applicable in both cell-center and cell-vertex 2 and 3D discretizations. A new implicit formulation is presented, which results in better computation efficiency, when added to the multigrid scheme. A few simple procedures are also proposed and applied to provide even higher convergence acceleration. The Euler equations are solved on an unstructured grid around standard transonic configurations to validate the algorithm and to assess its superiority to conventional explicit...