• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.1B
• /
• pp.35-41
• /
• 2010

In this paper, we propose a 3D view design scheme which arranges 2D information in a 3D virtual space with a flexible interface and voice information. The scheme allows the user interface of the 2D image in 3D virtual space anytime from any view point. Voice information can be easily attached. It is this simple and efficient image and voice information arrangement in 3D virtual space that improves information transfer.

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.2315-2324
• /
• 2023

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.

• International Journal of Aeronautical and Space Sciences
• /
• v.17 no.1
• /
• pp.8-19
• /
• 2016

This paper investigates the effects of inlet turbulence conditions and near-wall treatment methods on the heat transfer prediction of gas turbine vanes within the range of engine relevant turbulence conditions. The two near-wall treatment methods, the wall-function and low-Reynolds number method, were combined with the SST and ${\omega}RSM$ turbulence model. Additionally, the RNG $k-{\varepsilon}$, SSG RSM, and $SST_+{\gamma}-Re_{\theta}$ transition model were adopted for the purpose of comparison. All computations were conducted using a commercial CFD code, CFX, considering a three-dimensional, steady, compressible flow. The conjugate heat transfer method was applied to all simulation cases with internally cooled NASA turbine vanes. The CFD results at mid-span were compared with the measured data under different inlet turbulence conditions. In the SST solutions, on the pressure side, both the wall-function and low-Reynolds number method exhibited a reasonable agreement with the measured data. On the suction side, however, both wall-function and low-Reynolds number method failed to predict the variations of heat transfer coefficient and temperature caused by boundary layer flow transition. In the ${\omega}RSM$ results, the wall-function showed reasonable predictions for both the heat transfer coefficient and temperature variations including flow transition onset on suction side, but, low-Reynolds methods did not properly capture the variation of the heat transfer coefficient. The $SST_+{\gamma}-Re_{\theta}$ transition model showed variation of the heat transfer coefficient on the transition regions, but did not capture the proper transition onset location, and was found to be much more sensitive to the inlet turbulence length scale. Overall, the Reynolds stress model and wall function configuration showed the reasonable predictions in presented cases.

• KIEAE Journal
• /
• v.16 no.1
• /
• pp.81-87
• /
• 2016

Purpose: Heat transfers phenomena are described by the second order partial differential equation and its boundary conditions. In a three-dimensional structure of a building, the heat transfer phenomena generally include more than one material, and thus, become complicate. The analytic solutions are useful to understand heat transfer phenomena, but they can hardly be applied in engineering or design problems. Engineers and designers have generally been forced to use numerical methods providing reliable results. Finite volume methods with the unstructured grid system is only the suitable means of the analysis for the complex and arbitrary domains. Method: To obtain an numerical solution, a discretization method, which approximates the differential equations, and the interpolation methods for temperature and heat flux between two or more materials are required. The discretization methods are applied to small domains in space and time, and these numerical solutions form the descretized equations provide approximated solutions in both space and time. The accuracy of numerical solutions is dependent on the quality of discretizations and size of cells used. The higher accuracy, the higher numerical resources are required. The balance between the accuracy and difficulty of the numerical methods is critical for the success of the numerical analysis. A simple and easy interpolation methods among multiple materials are developed. The linear equations are solved with the BiCGSTAB being a effective matrix solver. Result: This study provides an overview of discretization methods, boundary interface, and matrix solver for the 3-dimensional numerical heat transfer including two materials.

• Archives of Reconstructive Microsurgery
• /
• v.6 no.1
• /
• pp.39-46
• /
• 1997

The methods of clinical applications of the foot as a free-flap donor site includes microvascular toe-to-finger transfer, free neurovascular flap transfer, first web space flap transfer, and osteocutaneous free flap transfer. We have evaluated the results of treatment for 35 patients to be undergone a microvascular reconstructive procedure with the foot as a donor site from January 1982 to June 1996. The performed operations were 16 cases of thumb reconstruction with wrap around procedure, 3 cases of tenocutaneous flap transfer, 10 cases of dorsalis pedis flap transfer, 2 cases of first web space free flap and 4 cases of toe-to-finger transfer. The follow up study was 69 months in average. Regarding to the various donor sites, morbidity was divided into five different categories: Cosmesis, Functional loss, Sensory loss, Wound complication, and Pain. According to the results of examination(35 patients), the results was excellent(25), good(9), fair(1), and poor(0). Among the categories, morbidity was higher at cosmesis. The patients under 50 years were better outcome. Among the operative methods from the foot as a donor site, thumb reconstruction with wrap around procedure showed poorest outcomes. So, We conclude that the foot as a free flap donor site is a good source for the microvascular reconstructive surgery. But, Preoperative donor site evaluation, adequate operative technique and post operative management are essential to decrease the morbidity of donor site.

• Journal of the Economic Geographical Society of Korea
• /
• v.25 no.1
• /
• pp.61-86
• /
• 2022

This paper analyzes the technology transfer mechanism of companies clustered in a specific economic space from the perspective of absorptive capacity, taking the Daegu automotive parts industry as an example. According to the analysis results, The absorptive capacity of a company was found to be positively related to the supplier, channel, method, and institutional interaction of technology transfer. Low absorptive capacity limits technology transfer by reducing companies' technology search capabilities, while high absorptive capacity gives companies access to technology search and various technology transfer opportunities through formal and informal channels. These results suggest that, in the short term, it is necessary to supplement the search capabilities of companies through preemptive visiting services of local intermediaries for the vitalization of regional technology transfer, while in the long term, a policy approach focusing on enhancing the absorptive capacity of local companies is required. For effective implementation of these policies, a multi-layered governance approach corresponding to each level of companies' absorptive capacities is required in establishing an interface structure that promotes linkage between institutional actors.

• Journal of Hydrogen and New Energy
• /
• v.33 no.4
• /
• pp.413-418
• /
• 2022

This paper presents two-phase condensation heat transfer and pressure drop characteristics of R32 and R454B as an alternative refrigerant to R410A in a 9.52 mm OD microfin tube. The test facility has a straight, horizontal test section with an active length of 2.0 m and is cooled by cold water circulated in a surrounding annular space. The heat transfer coefficients of the annular space were obtained using the modified Wilson plot method. Average condensation heat transfer coefficient and pressure drop data are presented at the condensation temperature of 35℃ for the range of mass flux 100-400 kg/m²s. The average condensation heat transfer coefficients of R32 refrigerant are 35-47% higher than R410A at the mass flux considered in the study, while R454B data are similar to R410A. The average pressure drop of R32 and R454B are much higher than R410A and they are 134-224% and 151-215% of R410A, respectively. R32 and R454B have relatively low GWP and high heat transfer characteristics, so they are suitable as alternatives for R410A.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.12
• /
• pp.1078-1087
• /
• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.10
• /
• pp.927-933
• /
• 2007

Heat transfer characteristic near a sharp fin was studied in a supersonic flow. Mach number and the Reynolds number were 3 and $5{\times}10^7$ respectively. Infra-red thermography was used to obtain the variation of surface heat transfer coefficient distribution. The angles of attack were ranged from $12.5^{\circ}$ to $20^{\circ}$ and the numerical analysis and the oil flow method were conducted to understand flow fields near a sharp fin.

• Journal of Astronomy and Space Sciences
• /
• v.28 no.3
• /
• pp.233-239
• /
• 2011

A series of computational analyses was performed to predict the cooling process by the cooling channel of preburners used for kerosene-liquid oxygen staged combustion cycle rocket engines. As an oxygen-rich combustion occurs in the kerosene fueled preburner, it is of great importance to control the wall temperature so that it does not exceed the critical temperature. However, since the heat transfer is proportional to the speed of fluid running inside the channel, the high heat transfer leads to a trade-off of pressure loss. For this reason, it is necessary to establish a certain criteria between the pressure loss and the heat transfer or the wall surface temperature. The design factors of the cooling channel were determined by the computational research, and a test model was manufactured. The test model was used for the hot fire tests to prove the function of the cooling mechanism, among other purposes.