• Wind and Structures
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• v.38 no.4
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• pp.261-275
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• 2024

Before performing an experimental study on the downburst-generated wave, it is necessary to examine the scale effects and corresponding corrections or compensations. Analysis of similarity is conducted to conclude the non-dimensional force ratios that account for the dynamic similarity in the interaction of downburst with wave between the prototype and the scale model, along with the corresponding scale factors. The fractional volume of fluid (VOF) method in association with the impinging jet model is employed to explore the characteristics of the downburst-generated wave numerically, and the validity of the proposed scaling method is verified. The study shows that the location of the maximum radial wind velocity in a downburst-wave field is a little higher than that identified in a downburst over the land, which might be attributed to the presence of the wave which changes the roughness of the underlying surface of the downburst. The impinging airflow would generate a concavity in the free surface of the water around the stagnation point of the downburst, with a diameter of about two times the jet diameter (D_jet). The maximum wave height appears at the location of 1.5D_jet from the stagnation point. Reynolds number has an insignificant influence on the scale effects, in accordance with the numerical investigation of the 30 scale models with the Reynolds number varying from 3.85 × 10⁴ to 7.30 × 10⁹. The ratio of the inertial force of air to the gravitational force of water, which is denoted by G, is found to be the most significant factor that would affect the interaction of downburst with wave. For the correction or compensation of the scale effects, fitting curves for the measures of the downburst-wave field (e.g., wind profile, significant wave height), along with the corresponding equations, are presented as a function of the parameter G.

• Ocean and Polar Research
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• v.33 no.2
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• pp.159-169
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• 2011

Antifreeze proteins (AFPs) have ice binding affinity, depress freezing temperature and inhibit ice recystallization which protect cellular membranes in polar organisms. Recent structural studies of antifreeze proteins have significantly expanded our understanding of the structure-function relationship and ice crystal growth inhibition. Although AFPs (Type I-IV AFP from fish, insect AFP and Plant AFP) have completely different fold and no sequence homology, they share a common feature of their surface area for ice binding property. The conserved ice-binding sites are relatively flat and hydrophobic. For example, Type I AFP has an amphipathic, single ${\alpha}$-helix and has regularly spaced Thr-Ala residues which make direct interaction with oxygen atoms of ice crystals. Unlike Type I AFP, Type II and III AFP are compact globular proteins that contain a flat ice-binding patch on the surface. Type II and Type III AFP show a remarkable structural similarity with the sugar binding lectin protein and C-terminal domain of sialic acid synthase, respectively. Type IV is assumed to form a four-helix bundle which has sequence similarity with apolipoprotein. The results of our modeling suggest an ice-binding induced structural change of Type IV AFP. Insect AFP has ${\beta}$-helical structure with a regular array of Thr-X-Thr motif. Threonine residues of each Thr-X-Thr motif fit well into the ice crystal lattice and provide a good surface-surface complementarity. This review focuses on the structural characteristics and details of the ice-binding mechanism of antifreeze proteins.

• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.3
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• pp.91-97
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• 1979

Boundary layer equations (partial differential equations) can be transformed to ordinary diffential equations with constant coeffieients in terms of similarity transformed to ordinary differential equations with constant coeffieients in terms of similarity transformations in the heat tranfer analysis on the surface of any axiaymmetric boiles. The azimuth functions can not be uniquely determined because of the singular behavior at the stagnation point(X=0.deg.).In spite of the azimuth functions behaving singularly, many of researchers have analyzed the heat transfer problem on a horizontal chlinder or a sphere, supposing the set of solutions( $H_{1}$ & G$_{1}$) of being yieled from the simple differential equation to be unique solution of therazimuth functions. In order to ascertain whether mathematical incompatibility as mentioned above can be admitted in the viewpoint of enginerring or not, condensation heat transfer coefficients on a sphere are computed for all azimuth functions( $H_{1}$ G$_{1}$ & $H_{2}$ G$_{2}$) and comparisons with the experimental result are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.8
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• pp.1010-1021
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• 1999

Camouflage measures in military purpose utilize the apparent temperature difference between target and background, so it is essential to develop a thermal analysis program for apparent temperature predictions and to apply some camouflage measures to real military targets for camouflage purpose. In this study, a thermal analysis program including conduction, convection and radiation is developed and the validity of radiation heat transfer terms is examined. The results show that longwave radiation along with solar radiation should be included in order to predict the apparent temperature as well as the physical temperature precisely. Longwave emissivity variation as an effective camouflage measures is applied to a real M2 tank. From the simulation results, it is found that an effective surface treatment, such as painting of a less emissive material or camouflage clothing, may provide a temperature similarity or a spatial similarity, resulting in an effective camouflage.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.142-149
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• 2002

In this paper, the metal forming process is caused of rise of the unit cost of production in increase of the lead-time and cost because of manufacturing final product through a few the number of processes. Flow control complex forming is proposed to put into formulation in order to apply cold forging from conventional approximate similarity theory, and the forming loads of the real material(AISI 1008) can be calculated by put at the new similarity formula the load by plasticine model material experiment through hub clutch. In order to reduce lead-time and cost the technology is used to manufacture with lower die of this product. By the application synthetic resin as the raw material, it is have the merit such short lead-time, low cost, good surface finish etc., as compared with the machine work.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.87-90
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• 2002

Computational study has been undertaken to investigate the aerodynamic influence of side jet on a supersonic missile and to find a similarity condition between the flight condition and the wind tunnel testing. Tasks were performed to validate the existing Raytheon test body with side jet, to simulate the flow inside the supersonic wind tunnel, and to compare the flow fields between the missile in free flight and that in the wind tunnel. Then sub-scale model of body-tail configuration was analyzed to estimate the influence of the side jet on the missile components. It Is found that the influence of side Jet is not as significant on the tail region as on the body surface and a simple algebraic formula for aerodynamic coefficients accounting for the side jet as a point force may be cautiously utilized in setting up control logic.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.2 s.191
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• pp.47-57
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• 2007

The vibration environment essentially companied by vehicle operation on the road is determined by the shape of road surface, which is called profile. In general, the profile and severity of unpaved road is an important issue in the reliability of durability test for vehicles. In order to maintain severity of unpaved road, it is necessary to develop profilometer system. We developed profilometer system which is composed of data processing computer, power unit, air compressor and sensors. This paper focuses on the severity management of unpaved test courses using neural networks. This paper presents the maintenance range for cross-country course in CPG(Chang-won Proving Ground) and the evaluation of similarity degree between unpaved roads.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.41-46
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• 2002

Computational study has been undertaken to investigate the aerodynamic influence of side jet on a supersonic missile and to find a similarity condition between the flight condition and the wind tunnel testing. Tasks were peformed to validate the existing Raytheon test body with side jet, to simulate the flow inside the supersonic wind tunnel, and to compare the flow fields between the missile in free flight and that in the wind tunnel. Then sub-scale model of body-tail configuration was analyzed to estimate the influence of the side jet on the missile components. It is found that the influence of side jet is not as significant on the tail region as on the body surface and a simple algebraic formula for aerodynamic coefficients accounting for the side jet as a point force may be cautiously utilized in setting up control logic.

• The KSFM Journal of Fluid Machinery
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• v.12 no.2
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• pp.17-23
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• 2009

The program using $C/C^{++}$ which could calculate 3-D velocities from data of the flowfield obtained by a slant hot-wire has been developed. The characteristic of the exit flowfield of a circular nozzle with a curved surface was investigated. From the result, the inward-flow was verified at adjacent layers near the boundary of the exit flowfield of a circular nozzle in Id and outward-flow was sensed gradually from down-flow of Id. Similarity of the nondimensional velocity profile properlly could be obtained except near Id and the virtual origin reasonably could be obtained.

• Journal of Ocean Engineering and Technology
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• v.23 no.4
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• pp.32-37
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• 2009

An analytic similarity shape solution was studied for a two-dimensional floating and fluid-filled membrane structure. The static shape of a membrane structure can be expressed as a set of nonlinear ordinary differential equations. The integration of curvature leads to an analytic solution for the shape, which contains unknown boundary values. Matching the upper and lower shapes at the free surface incorporated with their buoyancy allowed the unknowns to be determined. Some characteristic values of similarity shapes were evaluated and shapes are illustrated for various density ratios and volume efficiency ratios.