• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1575-1580
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• 2010

Recently, the development of bio-mimetic underwater vehicles that can emulate the characteristic movements of marine fish and mammals has attracted considerable attention. In this study, the motion of the batoid (i.e., cownose ray) fin that facilitates excellent cruising and maneuvering during underwater movement has been studied. The velocity achieved and distance covered with each fin movement are numerically studied. A fluid-structure interaction method is used to perform 3D time-dependent numerical analysis, wherein an adaptive mesh is employed to account for the large deformation of a fin interacting with a fluid. The results of a preliminary study show that the thrust of a ray fin is highly dependent on the frequency. Further, once the fin amplitude required for generating a given thrust is evaluated for the conditions experienced by an actual ray, the frequency and amplitude values for achieving better thrust are determined.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.11
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• pp.613-620
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• 2009

The thermal stresses of a ceramic heat exchanger were analyzed numerically since the ceramic material is good in heat resistance but weak in the thermal stress. The analysis of thermal stress was conducted in the ceramic core with two boundary conditions depending on bolt jointing. The thermal stresses were computed by applying temperature and pressure distributions obtained from the numerical results of conjugate heat transfer to ANSYS WORKRBENCH. When number of bolt joining halls was reduced from $8\times2$ to $4\times2$, the maximum principal stresses decrease by 47.6~50.5% and increase in safety factors by 2.18~2.5 for ultimate tensile strength. Thus, it can be said that bolt joining halls should be minimized in ceramic heat exchanger to be efficient in reducing thermal stress. In addition, the width of particular gas flow passages were revised from 52 mm to 42 mm to reduce maximum thermal stresses since certain passages experienced high thermal stresses. From the revision, safety factors were increased by 13.8~14.1% for the boundary condition of $4\times2$ bolt joining halls. Therefore, it is suggested that thermal stress can be reduced by changing local geometry of a ceramic heat exchanger.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.246-258
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• 2016

The shield building of AP1000 was designed to protect the steel containment vessel of the nuclear reactor. Therefore, the safety and integrity must be ensured during the plant life in any conditions such as an earthquake. The aim of this paper is to study the effect of water in the water tank on the response of the AP1000 shield building when subjected to three-dimensional seismic ground acceleration. The smoothed particle hydrodynamics method (SPH) and finite element method (FEM) coupling method is used to numerically simulate the fluid and structure interaction (FSI) between water in the water tank and the AP1000 shield building. Then the grid convergence of FEM and SPH for the AP1000 shield building is analyzed. Next the modal analysis of the AP1000 shield building with various water levels (WLs) in the water tank is taken. Meanwhile, the pressure due to sloshing and oscillation of the water in the gravity drain water tank is studied. The influences of the height of water in the water tank on the time history of acceleration of the AP1000 shield building are discussed, as well as the distributions of amplification, acceleration, displacement, and stresses of the AP1000 shield building. Research on the relationship between the WLs in the water tank and the response spectrums of the structure are also taken. The results show that the high WL in the water tank can limit the vibration of the AP1000 shield building and can more efficiently dissipate the kinetic energy of the AP1000 shield building by fluid-structure interaction.

• Wind and Structures
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• v.27 no.6
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• pp.381-397
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• 2018

Nonlinear behavior in fluid-structure interaction (FSI) of bridge decks becomes increasingly significant for modern bridges with increasing spans, larger flexibility and new aerodynamic deck configurations. Better understanding of the nonlinear aeroelasticity of bridge decks and further development of reduced-order nonlinear models for the aeroelastic forces become necessary. In this paper, the amplitude-dependent and neutral angle dependent nonlinearities of the motion-induced loads are further highlighted by series of computational fluid dynamics (CFD) simulations. An effort has been made to investigate a semi-analytical time-domain model of the nonlinear motion induced loads on the deck, which enables nonlinear time domain simulations of the aeroelastic responses of the bridge deck. First, the computational schemes used here are validated through theoretically well-known cases. Then, static aerodynamic coefficients of the Great Belt East Bridge (GBEB) cross section are evaluated at various angles of attack, leading to the so-called nonlinear backbone curves. Flutter derivatives of the bridge are identified by CFD simulations using forced harmonic motion of the cross-section with various frequencies. By varying the amplitude of the forced motion, it is observed that the identified flutter derivatives are amplitude-dependent, especially for $A^*_2$ and $H^*_2$ parameters. Another nonlinear feature is observed from the change of hysteresis loop (between angle of attack and lift/moment) when the neutral angles of the cross-section are changed. Based on the CFD results, a semi-analytical time-domain model for describing the nonlinear motion-induced loads is proposed and calibrated. This model is based on accounting for the delay effect with respect to the nonlinear backbone curve and is established in the state-space form. Reasonable agreement between the results from the semi-analytical model and CFD demonstrates the potential application of the proposed model for nonlinear aeroelastic analysis of bridge decks.

• Food Science and Industry
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• v.54 no.3
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• pp.184-195
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• 2021

Smart HACCP is a system that can check the monitoring of critical control point (CCP) in real time to implement improvement measures immediately after departure from limit criteria and prevent falsification of data by digitizing handwritten records. In this study, we developed the analysis model for the effectiveness ofsmart HACCP to compare and analyze with existing HACCP. By introducing of smart HACCP system, the evaluation index value of HACCP effectiveness for HACCP-certificated companies on a small scale increased by 9.25 points, corresponding to 11.52% of increase rate. General HACCP-certificated companies showed 4.52 point and 5.00% of increase rate by introducing of smart HACCP system. Thus, it was confirmed that the introduction of smart HACCP system contributes to the improvement of food safety management and especially it would be more effective for HACCP-certificated companies on a small scale than general HACCP-certificated companies.

• Food Science and Industry
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• v.54 no.2
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• pp.73-81
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• 2021

Korea Agency of HACCP Accreditation and Services(KAHAS) has been focused on strengthen food safety management and competitiveness of the food industry. As a solution, the institution has launched the smart HACCP project, which is highly praised to be an innovation in food safety management system. KAHAS try to analysis of food manufacturing company, candidate of supporting about construction of smart factory from Small and Medium venture Business Department and confirm the effect of smart HACCP introduction. Korea Agency of HACCP Accreditation and Services will use these results for widespread of smart HACCP

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.287-294
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• 2021

Modern small farms are important link components in the structure of the world agro-industrial complex. It ensures the food and nutritional sustainability of the country exclusively at the local regional level. The purpose of the research is to examine the role of farming in ensuring nutritional security and food stability based on the analysis of the Food Sustainability Index (FSI). Research methods: modeling, abstraction, analogy, analysis, synthesis, formalization, logical abstraction, theoretical cognition, systematization and classification, abstract-logical, etc. Results. Having analyzed the Food Sustainability Index for 2018, it has been established that there is a lack of a clear relationship between the pace of economic development and the level of food and nutritional sustainability. In addition, this study has identified the countries with the largest number of small farms, as well as the number of farms within the region. The correlation between the size of the farm and the area of agricultural land that it cultivates has been determined. The problems faced by small farms in the process of their activity have been analyzed. The programs implemented in the field of agro-industrial complex development by international profile institutions have been systematized. Particularly, the regional structure of agricultural development programs under the guidance of IFAD is defined, as well as the areas to which they are directed. Specific measures taken by governments to stimulate the development of small farms have been outlined. Reasonable conclusions have been formed based on the study. The direction of future research is seen in the assessment of the export potential of small farms in terms of range, volume of export deliveries and geographical direction of movement of their products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1185-1191
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• 2014

Gas turbine blades that have complex geometry of the cooling holes and cooling passages are usually subjected to cyclic and sustained thermal loads due to changes in the operating characteristic in combined power plants; these results in non-uniform temperature and stress distributions according to time to gas turbine blades. Those operation conditions cause creep or thermo-mechanical fatigue damage and reduce the lifetime of gas turbine blades. Thus, an accurate analysis of the stresses caused by various loading conditions is required to ensure the integrity and to ensure an accurate life assessment of the components of a gas turbine. It is well known that computational analysis such as cross-linking process including CFD, heat transfer and stress analysis is used as an alternative to demonstration test. In this paper, temperatures and stresses of gas turbine blade were calculated with fluid-structural analysis integrating fluid-thermal-solid analysis methodologies by considering actual operation conditions. Based on analysis results, additionally, the total lifetime was obtained using creep and thermo-mechanical damage model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.724-729
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• 2017

The crashworthiness of the fuel tank of a rotorcraft is verified through the crash impact test. The crash impact test has a high risk of failure due to the application of an excessive load, which can seriously affect the overall development schedule of the aircraft. Therefore, a lot of effort has been made to minimize the possibility of failure in the actual test by carrying out a numerical analysis of the crash impact test of the fuel tank in the initial design stage. Recently, an external auxiliary fuel tank was added to increase the cruising distance. In this study, the numerical analysis results of the crash impact test based on several different shapes of the external auxiliary fuel tank are presented, in order to evaluate its crashworthiness. For the numerical analysis, smoothed particle hydrodynamics (SPH), which is one of the fluid-structure coupled analysis methods, is applied and the test conditions prescribed by US military standards are reflected in the analysis conditions. In addition, the material property data previously obtained by the specimen test of the actual fuel tank is applied to the numerical analysis. As a result, the equivalent stress of the fuel tank material itself and the metal fitting is provided and the possibility of acquiring data for designing the crash-worthiness of the external auxiliary fuel tank is evaluated by examining the behavior and working load of the internal mounted components.

• Food Science and Industry
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• v.51 no.3
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• pp.174-184
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• 2018

The impact of regulations on industrial activities is significant. Because the food industry has to observe given obligations and bear costs and expenses resulted from complying with applicable food safety regulations. Meanwhile, A government drafts the regulatory impact analysis report prior to enactment, amendment or reinforcement of any regulations. The analysis powered by objective and scientific methodologies enable a government to judge whether a particular regulation will be good or bad for the society. An effective policy implementation in practice and cost-bearing is entirely up to industries. Moreover, opportunity cost and actual cost relating to or arising from regulatory compliance will be estimated only by the respective industries. Therefore, the food Industry needs to collect and accumulate the said information and also to disseminate their hardships and financial burdens. Objective and practical information will encourage a government to set out regulatory frameworks that rational policy making.