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- 저자 : Amar, Nechnech (검색결과 293 건)
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Amar Bouhallassa,Samia Benattalah 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.3
The gas liquid mass transfer has been studied for a single long bubble, which is kept stationary in the flow by a low and stable flow rate of liquid around it. This study was carried out for a downward flow in small diameter pipe. The mass transfer mechanism is quite complicated because it doesn’t depend only on the physical properties of the gas; but also on the hydrodynamics of the bubble and the liquid film around it. Based on Hgbie’s penetration theory a detailed numerical simulation of the hydrodynamic characteristics of the gas liquid mass transfer in a vertical pipe is developed using the volume of fluid (VOF) method implemented in the commercial software ANSYS Fluent. The simulation is performed using three types of gas, which are nitrogen, oxygen, and carbon dioxide as the gas phase, and water as the liquid one. The results show that the mass transfer of gas increases as the length of the bubble does. For the three types of gas, the mass transfer coefficient increases with the decrease of the gas density. The numerical results are analogous with the experimental ones available in the literature.
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Thermoelectrically controlled micronozzle - A novel application for thermoelements
Amar Hasan Hameed,Raed Kafafy 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
This paper introduces and assesses the concept of the recently invented thermoelectrically controlled micronozzle (TECMN). A generalized quasi-one-dimensional model for gas flow, which is influenced by area variation and by wall heat transfer, is considered. In order to assess the merits of wall temperature control in micronozzles, the flow in the micronozzle is solved numerically for cases of convergent wall heating, divergent wall cooling, and a combination of both. Thermal efficiency and specific impulse are affected by heat exchange through the side wall of the micronozzle. By cooling the divergent section, kinetic energy increases, thus improving thermal efficiency. The mass flow rate is decreased in all cases that include convergent section heating, thereby enhancing specific impulse. The combination of convergent section heating with divergent part cooling results in significant performance enhancement in terms of thermal efficiency and specific impulse. To determine the TECMN wall temperature profile, we developed a one-dimensional general energy model for a thermoelement (TE) subject to an electric field as well as for heat convection on the lateral surface. The energy equation is analytically solved for constant properties and for Joule heating equivalent to heat convection. The temperature profile is then imposed on the quasi-one-dimensional flow model, which is solved numerically for various mass flow rates and exit wall temperature (cold junction). As the exit section wall temperature and mass flow rate decrease, the utilization of TEs to control the temperature of micronozzle walls considerably increases the Mach number at exit.
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Adaptability and Stability Analysis of Groundnut Genotypes Using AMMI Model and GGE-biplot
Amare Kebede B,Adisu Getahun 한국작물학회 2017 Journal of crop science and biotechnology Vol.20 No.5
Unpredictable rainfall, variations in farm inputs, crop-diseases, and the inherent potential of genotypes are among the major factors for low and variable crop yield. Fourteen elite groundnut genotypes were examined in 14 environments to analyze adaptability and stability of genotypes, and identify mega-environments if they exist. Additive main effect and multiplicative interaction (AMMI) model, cultivar-superiority measure, and genotype plus genotype-by-environment (GGE) biplot analysis were used for data analysis. The environment (69.8%) and genotype-by-environment interaction (GEI) effects (21.4%) were dominating the genotypic effect (8.8%). The GEI was significant (P < 0.01), and two distinct environments (mega-environments) were identified, suggesting separate national groundnut breeding strategies for Babile and Pawe. ICGV-94100 and ICGV-97156 were stable and had the highest-yield at Babile and Pawe, respectively. The higher heritability value was recorded in more homogeneous and favorable environments, indicating the genetic potential of groundnut genotypes were better attained in more homogeneous and favorable environments. AMMI model, cultivar-superiority measure, and GGE biplots were helpful methodologies and complemented each other to evaluate the adaptability and stability of groundnut genotypes in diverse environments.
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Amar Udare,Nilesh Sable,Rajiv Kumar,Meenakshi Thakur,Shashikant Juvekar 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.1
Solitary metastases from colorectal carcinoma in the absence of hepatic or pulmonary metastases are rare. These can have a diverse imaging appearance, particularly after chemotherapy. It is important identify patients with solitary skeletal metastases, as they have a better prognosis than those with multiple skeletal or visceral metastases. We describe an unusual case of a solitary metastasis to the femur in a case of colon carcinoma that went undiagnosed and later presented with imaging features of osteogenic sarcoma.
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Amare WONDIRAD 한국서비스디자인학회 2023 한국서비스디자인학회 학술대회자료집 Vol.2023 No.1
Ecotourism has been widely promoted by academics and practitioners alike as a tool to achieve the dual aims of conservation and development. However,several scholars questioned whether sustainability goals can be successfully achieved through ecotourism. Of the various limiting factors of ejfective ecotourism development discussed in the literature, a lack of ejfective stakeholder collaboration is pervasive. This study investigates the contributions of stakeholder collaboration towards sustainable ecotourism development in a developing country setting by employing stakeholder and collaboration theories and triple-bottom-line principles. Through adopting a qualitative research approach with an exploratory design, the current study unfolds the existence of poor interactions and collaboration among ecotourism stakeholders, which in turn, affects the sustainable development of ecotourism. Findings challenge that in poorly resourced remote destinations, failure to meaningfully empower and participate communities does not only undermine the successful development of ecotourism but also it jeopardizes the long-term survival of the ecosystem and communities themselves.
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