121 research outputs found

    Obscurant and Radiation Characteristics of Infrared Screening Smoke Composition Based on Red Phosphorus

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    Red phosphorus-based camouflage compositions are often used on naval ships to counter anti-ship missiles. This work focused on investigating the obscurant and infrared radiation characteristics of infrared-screening smoke of pyrotechnic compositions based on red phosphorus, Mg-Al alloy, barium nitrate and Viton A rubber. The results demonstrated that the smoke clouds of the formulation based on red phosphorus and Mg-Al alloy have a high attenuation capability to 1.064 µm laser radiation. Besides, these smokescreens also have a better emission power in the wavelength range of 2.5-5 and 8-14 µm. Therefore, the smoke compositions based on red phosphorus and Mg-Al alloy can be used in camouflage devices on naval ships against infrared and laser-guided missiles

    THE ANALYSIS OF FLUID DYNAMICS OF WAVE POWER STATION WITH WELLS TURBIN BY CFD

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    Natural energy such as wind, wave and other natural vibrations is one of the high potential renewable energy sources. The Wells turbine is based on the use of bidirectional turbines, which act as axial-flow self-rectifying turbines that employs a symmetrical blade profile and rotating unidirectionally in reciprocating airflows generated by the air chamber to extract energy from vibrations. These topics have been extensively studied both numerically and experimentally such as research on the parameters of the effects of structure, angle of attack, blade shape, etc. In this paper, numerical simulation is carried out using commercially available tool Fluent for fluid dynamics analysis and focus on oscillating predictions, with particular attention to the behavior of the flow. Based on the Numerical Wave Tank (NWT) model is simulated in a two dimensional used in this model, which is constructed mainly based on the spatially averaged Navier Stokes equation with the k-ε model for simulating the turbulence and modeled with Volume of Fluid (VOF). Axial-flow turbines system and future development as well as the proposed limitations will be discussed in detail

    Automatic Data Structure Repair using Separation Logic

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    Evaluation of genetic diversity and DNA fingerprinting of 19 standard reference rice varieties using SSR markers

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    Molecular markers are advanced-tools for identifying new varieties at DNA levels. According to the International Union for the Protection of New Varieties ofPlants,  new breeded varieties need to be tested for the Distinctness, Uniformity and Stability (DUS), before being recognized as the new ones. Traditional DUS criteria based on 62 - 65 morphological and biochemical characteristics, which evaluated on comparison of new varieties with 19 standard reference varieties for traits of interest.  Study on the genotypic polymorphism of 19 standard reference rice varieties provides genotypic information of these varieties for the evaluation of new rice varieties based on genotyping analysis.  The reference marker set (30 markers) was used to evaluate the genetic diversity and DNA fingerprinting of 19 standard reference rice varieties. The results showed the similarity coefficient of 19 varieties varied from 0.04 to 0.548. At the genetic similarity coefficient of 0.1, the 19 rice varieties divided into two main groups. Group one included 3 varieties: DH1, DH5, DH13. Group 2 included the remaining 16 varieties. Inside group two, phylogenetic tree divided into two main branches at the genetic similarity coefficient of 0.3. Branch 1 includes 5 varieties including DH2, DH6, DH10, DH11 and DH7. The 11 remaining varieties were in the branch 2. The most closely varieties were DH6 and DH10 with the genetic similarity coefficient of 0.548. This study shows that, the standard reference varieties have high uniformity and high genotypic polymorphism, could used for testing new varieties based on genotyping by DNA fingerprinting combining with phenotype

    A comparison study of some control methods for delta spatial parallel robot

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    A comparison between three methods applied to parallel robot control namely: computed torque controller, sliding mode control and sliding mode control using neural networks is presented in this paper. The simulation results show that PD control method is only accurate when model parameters are precisely identified. In case of uncertain parameters, sliding mode and neural network sliding mode control methods are applied instead. Three controllers are implemented in Matlab for simulation. The results show that the control quality is improved by using the neural network sliding mode control method in comparison with two others.

    Investment on environmental social and governance activities and its impact on achieving sustainable development goals: evidence from Chinese manufacturing firms

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    Achieving sustainable development goals (SDGs) is a global requirement that attracts new researchers and regulators. So, the current research investigates the impact of investment on the environment, social, and governance (ESG) activities on the achievement of SDGs of the Chinese manufacturing companies. The current article also examines the mediating impact of organizational effectiveness among the nexus of investment in ESG activities and the achievement of SDGs of the Chinese manufacturing companies. The current research has taken the questionnaires to gather the data and used the smart-PLS to analyze the data. The results exposed that investment in the environment and social activities have a positive impact on the achievement of SDGs. The findings also revealed that the organizational effectiveness significantly mediates among the nexus of investment in the environment and social activities and the achievement of SDGs of the Chinese manufacturing companies. This study provides help to the relevant authorities to achieve the SDGs using the investment in ESG activities

    The impact of productivity on export transitions: revisited evidence from the Vietnamese manufacturing sectors

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    The effect of total factor productivity (TFP) on exports particularly interests policy-makers and economists, but empirical evidence is ambiguous. This paper uses the 6-wave panel data in 2010-2015 to investigate the impact of TFP on export transitions at the firm level. We distinguish different types of export transitions, namely start, stop, continuity, fluctuation, and striving, and different phases of export transition. The Generalised Method of Moments (GMM) estimation is applied to control for endogeneity and unobserved time-invariant specific components. The results reveal that (i) the effect of productivity on export (the self-selection hypothesis) is heterogeneous, depending on specific sectors and types and phases of export transitions; (ii) productivity growth does not necessarily result in positive effects on and lead to participation in types and phases of export transitions. Our results also reveal strong evidence of favourable sunk cost in long-run export striving in nearly all sectors, and unlike previous studies, empirical results show a negative effect of sunk cost in some manufacturing sectors. Policy-makers should create dynamic comparative advantages and favourable environments for new exporters, focus the relevant policies on productivity stimulus, and strengthen the likelihood of survival for the domestic firms in the competitive global markets

    Study change of the performance of airfoil of small wind turbine under low wind speed by CFD simulation

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    Renewable energy has received strong attention and investment to replace fossil energy sources and reduce greenhouse gas emissions. Quite good and good wind speed areas have been invested in building large-capacity wind farms for many years. The low wind speed region occupies a very large on the world, which has been interested in the exploitation of wind energy in recent years. In this study, the original airfoil of S1010 operated at low wind speed was redesigned to increase the aerodynamic efficiency of the airfoil by using XFLR5 software. After, the new VAST-EPU-S1010 airfoil model was adjusted to the maximum thickness and the maximum thickness position. It was simulated in low wind speed conditions of 4-6 m/s by CFD simulation. The lift coefficient, drag coefficient and CLC_{L}/CDC_{D} coefficient ratio were evaluated under the effect of the angle of attack and the maximum thickness by using the kϵk-\epsilon model. Simulation results show that the VAST-EPU-S1010 airfoil achieved the greatest aerodynamic efficiency at the angle of attack of 3\,^{\circ}, the maximum thickness of 8\% and the maximum thickness position of 20.32\%. The maximum value of CLC_{L}/CDC_{D} of the new airfoil at 6 m/s is higher than at the 4 m/s by about 6.25\%.Comment: 19 pages, 21 figure

    Literature Review of Knowledge Sharing and Issues Raised for Vietnamese Universities

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    This study aims to review previous studies in the field of knowledge sharing. Data being used in this study was collected from researches related to the topic of knowledge sharing. We summarize literature on knowledge sharing in terms of (i) Necessity of knowledge sharing, (ii) Supporting from information and communication technology tools (ICT), (iii) Context of knowledge sharing, (iv) Participants knowledge sharing, (v) Receiver knowledge and (vi) advantages and disadvantages when participating in knowledge sharing. Some implications are recommended for Vietnamese universities to better support knowledge sharing activities in Vietnam and around the world. Keywords: Knowledge management, Knowledge sharing, Information technology, Management information system. DOI: 10.7176/JESD/10-18-17 Publication date:September 30th 201

    Depth-dose distribution in potatoes with low-energy X-rays

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    Irradiation is known as a handful measure to inhibit potato sprouting, kill harmful bacteria, and increase preservation. The absorbed dose is one of the essential characteristics of the irradiation process. In this study, the depth-dose distributions in potatoes and polymethyl methacrylate were investigated under low-energy X-ray irradiation by using the Fricke dosimeter and Gafchromic film dosimeter. The dose rates required for the rays to penetrate in polymethyl methacrylate were compared with those in potatoes. Polymethyl methacrylate could be used as a phantom in measuring the depth dose delivered in potatoes. The difference in depth-dose distribution in potatoes between one-sided and double-sided irradiation was also investigated. The calculated dose uniformity ratio values are 5.8 and 1.9 for potatoes irradiating one-sided and double-sided
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