Tech Science Press
Not a member yet
3972 research outputs found
Sort by
An Automated Approach to Generate Test Cases From Use Case Description Model
No full textTest complexity and test adequacy are frequently raised by software developers and testing agents. However, there is little research works at this aspect on specification-based testing at the use case description level. Thus, this research proposes an automatic test cases generator approach to reduce the test complexity and to enhance the percentage of test coverage. First, to support the infrastructure for performing automatic, this proposed approach refines the use cases using use case describing template and save it in the text file. Then, the saved file is input to the Algorithm of Control Flow Diagram (ACFD) to convert use case details to a control flow diagram. After that, the Proposed Tool of Generating Test Paths (PTGTP) is used to generate test cases from the control flow diagram. Finally, the genetic algorithm associated with transition coverage is adapted to optimize and evaluate the adequacy of such test cases. A money withdrawal use case in the ATM system is used as an ongoing case study. Preliminary results show that the generated test cases achieve high coverage with an optimal test case. This automatic test case generation approach is effective and efficient. Therefore, it could promote to use other test case coverage criteria
Synthesis and Characterization of Novel Castor Oil-Based Polyol for Potential Applications in Coatings
No full textIn this study, three sorts of polyols were successfully synthesized from castor oil using a Dean-Stark quick, eco-friendly and high-efficiency method. For this purpose, castor oil was epoxidized in the presence of two types of catalysts including γ-alumina and formic acid, named as ECOAl and ECOF, respectively. Epoxidized castor oils were then characterized by use of hydrogen nuclear magnetic resonance (H-NMR) and oxirane oxygen content analysis. The relative percentages of conversion double bond to oxirane were obtained 96% and 74% for ECOAl and ECOF, respectively. Ring opening reaction of ECOAl was performed by two types of saponified castor oil as well as castor oil in a system equipped with Dean–Stark apparatus. The synthesized polyols were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), viscometer and OH number evaluation. The material obtained in this research is a candidate to be intended in synthesis of polyurethane for coating applications
Meshfree Point Collocation Schemes for 2D Steady State Incompressible Navier-Stokes Equations in Velocity-Vorticity Formulation for High Values of Reynolds Number
No full textA meshfree point collocation method has been developed for the velocity-vorticity formulation of two-dimensional, steady state incompressible Navier-Stokes equations. Particular emphasis was placed on the application of the velocity-correc -tion method, ensuring the continuity equation. The Moving Least Squares (MLS) approximation is employed for the construction of the shape functions, in conjunction with the general framework of the point collocation method. Computations are obtained for regular and irregular nodal distributions, stressing the positivity conditions that make the matrix of the system stable and convergent. The accuracy and the stability of the proposed scheme are demonstrated through two representative, well-known, and established benchmark problems. The numerical scheme was also applied to a case with irregular geometry for marginally high Reynolds numbers
Model of CEL for 3D Elements in PDMs of Unidirectional Composite Structures
Get PDFProgressive damage models (PDMs) have been increasingly used to simulate the failure process of composite material structures. To accurately simulate the damage in each ply, 3D PDMs of composite materials have received more attention recently. A characteristic element length (CEL), which is an important dimensional parameter of PDMs for composite materials, is quite difficult to obtain for 3D elements, especially considering the crack directions during damage propagation. In this paper, CEL models for 3D elements in PDMs of unidirectional composite structures are presented, and their approximate formulae are deduced. The damage in unidirectional composite materials can be divided into fiber cracks and inter-fiber cracks. The fiber crack and inter-fiber crack directions are considered in the CEL derivations, and thus, the CELs of 3D elements that have various damage modes and damage directions could be obtained relatively precisely. Static tensile and compressive tests of open-hole laminates were conducted, and the corresponding numerical analyses by the progressive damage method, including the proposed CEL models and those models from the literature, were performed. The numerical results are in good agreement with the experimental results, which proves the fidelity and effectiveness of the proposed CEL models. In addition, the proposed CEL models have better performance in improving the mesh independence of the numerical models
Numerical Simulation and Experimental Studies on Elastic-Plastic Fatigue Crack Growth
Get PDFA elastic-plastic fatigue crack growth (FCG) finite element model was developed for predicting crack growth rate under cyclic load. The propagation criterion for this model was established based on plastically dissipated energy. The crack growth simulation under cyclic computation was implemented through the ABAQUS scripting interface. The predictions of this model are in good agreement with the results of crack propagation experiment of compact tension specimen made of 304 stainless steel. Based on the proposed model, the single peak overload retardation effect of elastic-plastic fatigue crack was analyzed. The results shows that the single peak overload will reduce the accumulation rate of plastic energy dissipation of elements at crack tip plastic zone, so that crack growth will be arrested. The crack growth rate will not recover until the crack tip exceed the affected region. Meanwhile, the crack growth rate is mainly determined by the amplitude rather than the mean load under the condition of small scale yielding. The proposed model would be helpful for predicting the growth rate of mode I elastic-plastic fatigue crack
Impact of Tactical Parameters of Aircraft on Jamming Effectiveness of Surface-Source IR Decoy
Get PDFAs the platform for surface-source infrared decoys, the target aircraft is the aim of attacks in air-to-air combat. It can quickly and accurately evaluate the jamming effectiveness of the surface-source IR decoy in various states of motion is important for enhancing the security of the aircraft. This paper proposes a model of surface-source IR decoy, and compares and analyzes simulated and measured infrared images of diffusion. A system to assess the effectiveness of the jamming of the surface-source IR decoy, target aircraft, and infrared guided missile called “Trinity” is established. Simulations were conducted to assess the impact of flight height, flight speed, and the maneuvering of the target aircraft on the jamming effectiveness of the surface-source IR decoy. The results show that with an increase in flight height and speed, the jamming probability of a surface-source IR decoy first increases and then decreases, where evasive maneuvering by the target aircraft can effectively improve this probability. When the radius of the vertical snake maneuver was 125 m, that of the horizontal snake maneuver was 200 m, and the radius of the barrel roll maneuver was 250 m, the jamming probability of the surface-source IR decoy was relatively high. By comparing the simulation results with measured data, the study verified the accuracy of the proposed method
Development and Application of a High-Performance Triangular Shell Element and an Explicit Algorithm in OpenSees for Strongly Nonlinear Analysis
Get PDFThe open-source finite element software, OpenSees, is widely used in the earthquake engineering community. However, the shell elements and explicit algorithm in OpenSees still require further improvements. Therefore, in this work, a triangular shell element, NLDKGT, and an explicit algorithm are proposed and implemented in OpenSees. Specifically, based on the generalized conforming theory and the updated Lagrangian formulation, the proposed NLDKGT element is suitable for problems with complicated boundary conditions and strong nonlinearity. The accuracy and reliability of the NLDKGT element are validated through typical cases. Furthermore, by adopting the leapfrog integration method, an explicit algorithm in OpenSees and a modal damping model are developed. Finally, the stability and efficiency of the proposed shell element and explicit algorithm are validated through the nonlinear time-history analysis of a high-rise building
Structural Finite Element Software Coupling Using Adapter Elements
Get PDFThis paper describes a versatile and computationally efficient method for coupling several finite element analysis (FEA) programs together so that the unique modeling and analysis capabilities of each code can be utilized simultaneously to simulate the static or dynamic response of a complete numerical system. An arbitrary number of finite element analysis software packages can be coupled by adding two special types of elements, namely generic and adapter elements, to each of the finite element applications using their programming interface. These elements are inserted at the interfaces between the different sub-domains of the complete system modeled by each finite element analysis software package. Exchange of data between the coupled FEA codes is accomplished in a modular and synchronized manner using OpenFresco (Open-source Framework for Experimental Setup and Control). OpenFresco is an object-oriented, environment independent software framework initially developed for hybrid simulation in which certain aspects of a complete structure are simulated numerically and other aspects are simultaneously tested physically. An important practical advantage of this coupled analysis approach is that all of the connected FEA codes run concurrently and continuously, decreasing analysis time consumption by an order of magnitude or more compared to more traditional approaches that shut down and restart the coupled analysis codes at each integration time step. The implementation and accuracy of this approach to FE software coupling are demonstrated using dynamic analyses of three simple structural models from the field of earthquake engineering
Development of Cloud Based Air Pollution Information System Using Visualization
Get PDFAir pollution caused by fine dust is a big problem all over the world and fine dust has a fatal impact on human health. But there are too few fine dust measuring stations and the installation cost of fine dust measuring station is very expensive. In this paper, we propose Cloud-based air pollution information system using R. To measure fine dust, we have developed an inexpensive measuring device and studied the technique to accurately measure the concentration of fine dust at the user’s location. And we have developed the smartphone application to provide air pollution information. In our system, we provide collected data based analytical results through effective data modeling. Our system provides information on fine dust value and action tips through the air pollution information application. And it supports visualization on the map using the statistical program R. The user can check the fine dust statistics map and cope with fine dust accordingly
Dynamic Response Solution of Multi-Layered Pavement Structure Under FWD Load Appling the Precise Integration Algorithm
Get PDFThe pavement layered structures are composed of surface layer, road base and multi-layered soil foundation. They can be undermined over time by repeated vehicle loads. In this study, a hybrid numerical method which can evaluate the displacement responses of pavement structures under dynamic falling weight deflectometer (FWD) loads. The proposed method consists of two parts: (a) the dynamic stiffness matrices of the points at the surface in the frequency domain which is based on the domain-transformation and dual vector form equation, and (b) interpolates the dynamic stiffness matrices by a continues rational function of frequency. The mixed variables formulation (MVF) can treat multiple degree of freedom systems with considering the coupling term between degree of freedoms. The accuracy of the developed method has been demonstrated by comparison between the proposed method and published results from the other method. Then the proposed method can be applied as a forward calculation technique to emulate the falling weight deflectometer test for multi-layered pavement structures