• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.986-993
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• 2007

The microchannel heat sink is promising heat dissipation method far high density electronic devices. The cross-sectional shape of MEMS based microchannel heat sink is limited to triangular, trapezoidal, and rectangular due to their fabrication method. And heat is added to one side surface of heat source. Therefore, those specific conditions make some complexity of heat transfer in microchannel heat sink. Though many previous research of conjugate heat transfer in microchannel was conducted, most of them did not consider heat loss. In this study, numerical investigation of conjugate heat transfer in rectangular microchannel was conducted. The method of heat loss evaluation was verified numerically. Heat distribution was different for each wall of rectangular microchannel due to thermal conductivity and distance from heat source. However, the ratio of heat from each channel wall was correlated. Therefore, the effective area correction factor could be proposed to evaluate accurate heat flux in one side heating condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.14-22
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• 2007

A reversed trapezoidal fin with variable lateral surface slope is optimized using a two-dimensional analytic method. For a fin base boundary condition, convection from the inside fluid to the inside wall and conduction from the inside wall to the fin base are considered. Heat loss from the fin tip surface is not ignored. The maximum heat loss at the practical fin length, the corresponding optimum fin efficiency, fin length and fin base height are presented as a function of the fin inside and outside convection characteristic numbers. One of the results shows that the optimum fin shape becomes 'fatter and shorter' as the ratio of fin tip height to base height increases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.1044-1051
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• 1989

A numerical calculation is carried out for the analysis of 3-dimensional compressible flow field in axial-flow rotating blades by using finite element method. The calculation of flow in impellers plays a dominant role in the theoretical research and design of turbomachines. Three-dimensional flow fields can be obtained by the quasi-three-dimensional iterative calculation of the flows both on blade-to-blade stream surfaces and hub-to-shroud stream surfaces with the introduction of viscous loss model in order to consider a loss due to viscosity of fluid. In devising the loss model, four primary sources of losses were identified: (1) blade profile loss (2) end wall loss (3) secondary flow loss (4) tip-leakage loss. For the consideration of an axially parabolic distribution of loss, the results of present calcullation are well agreed with the results by experiment, thus the introduction of loss model is proved to be valid.

• Steel and Composite Structures
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• v.37 no.3
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• pp.341-351
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• 2020

Steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is a lateral force-resisting system that exhibits flag-shaped hysteretic responses, which consists of two pre-pressed spring self-centering energy dissipation (PS-SCED) braces and a wall plate connected to horizontal boundary elements only. The present study conducted a series of cyclic tests to study the hysteretic performances of braces in SPSW-SCEDB and the effects of braces on the overall hysteretic characteristics of this system. The SPSW-SCEDB with PS-SCED braces only exhibits excellent self-centering capability and the energy loss caused by the large inclination angle of PS-SCED braces can be compensated by appropriately increasing the friction force. Under the combined effect of the two components, the SPSW-SCEDB exhibits a flag-shaped hysteretic response with large lateral resistance, good energy dissipation and self-centering capabilities. In addition, the wall plate is the primary energy dissipation component and the PS-SCED braces provide supplementary energy dissipation for system. The PS-SCED braces can provide up to 90% self-centering capability for the SPSW-SCEDB system. The compressive bearing capacity of the wall plate should be smaller than the horizontal remaining restoring force of the braces to achieve better self-centering effect of the system.

• Journal of The Korean Digital Architecture Interior Association
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• v.13 no.4
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• pp.25-32
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• 2013

The green building is one of biggest factors to go the goal of energy saving and environmental conservation, reduction of energy consumption, friendly energy technology, recycling of resource, and environmental pollution reduction technology. The purpose of these green buildings realized by the energy-saving technology such as the exterior materials or curtain wall system. The curtain wall system is a element that come to insulated portions of building envelope that results in heat loss. The purpose of this paper is to carried out mock-up tests for exterior wall used in autoclaved lightweight concrete panels in green building practices. Mock-up test execute a mixed process between standard test procedure and complex test procedure based on AAMA 501(American Society for Testing and Materials) and ASTM 283, ASTM 330(American Society for Testing and Materials). In results, tests meet the requirements that grant values in steps of procedures provided on ASTM and AAMA. ALC panel is suitable for a exterior wall product to be gratified thermal cycling performance and structural capacity, deflection(H/200) and lateral displacement(H/50), for curtain walls.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.81-88
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• 2022

It is necessary to better understand the effect of age-related degradation on the performance of reinforced concrete shear walls in nuclear power plants in order to ensure their structural safety in the event of earthquakes. Therefore, this paper studies seismic fragility of the typical shear wall in nuclear power plants under earthquake excitation Reinforced concrete shear wall is composed of wall, horizontal and vertical flanges. Due to characteristics of its geometry, it is difficult to predict the ultimate behavior of shear wall under earthquake excitation. In this study, for more realistic numerical simulation, the Latin Hyper-Cube (LHC) simulation technique was used to generate uncertain variables for the material properties of concrete shear walls. The effects of crack, characteristics of inelastic behavior of concrete, and loss of cross section were considered in the nonlinear finite element analysis. The effects of aging-related deterioration were investigated on the performance of reinforced concrete shear walls through analysis of undegraded concrete shear walls and degraded concrete shear walls. The resulting seismic fragility curves present the change of performance of concrete shear wall due to age-related degradation.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.10 no.1
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• pp.1-11
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• 1981

In this paper, a new performance equation of bath tubs has been derived, which is very characteristically illuminating and in good agreement with experiments : $$T=T_{\infty}+(T_0-T_{\infty})e-\frac{k(A'_f+A_0)}{Mc_{P{\Delta}x}t$$, where $T_{\infty}$ is the temperature of the bathroom, $T_0$ that of the bathwater at t=0, k the overall heat conductivity of the tub- wall, $A'_f$ the equivalent surface area to the wall, $A_0$ the submerged area of the tub-wall, M mass of the bath-water, $C_p$ the specific heat of the bathwater and ${\Delta}x$ the thickness of the tub-wall. Here the equivalent-free surface area is written as $$A'_f=mA_f,\;m=const.(1-{\phi})^{0.88}$$ : where m is a numerical factor which is determined by a simple experiment and some calculation, {\phi}$ the relative humidity and $A_f$ the real free-surface area. From this study, it has been clarified that cooling of bath-water is mainly due to mass-transfer through evaporation from the free surface and conductive heat loss through the tub-wall is minor, which rather gaily mock at common sense. The effect of keeping bathwater warn by increase of the tub-wall thickness is also analyzed by a new idea of the thickness gain factor.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.211-218
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• 2020

The radio wave propagation characteristics of the transmitter and receiver position change in the indoor environment were predicted through simulation, then the results obtained through the transmission loss measurement were compared and analyzed with the simulation results. The conference room was chosen as the environment for measuring transmission loss, and the radio transmission characteristics of the two environments were compared by selecting the exhibition hall without interior decorations and fixtures. In each indoor environment, the position of the transmitter chose two cases. One located in the center of the front wall and the other in the center of the side wall, and the position of the receiver moved along the centerline of the conference room and the side wall, measuring the receiving power. For each change in transmitter-receiver position, received power of 3GHz and 6GHz band were measured and compared with the simulation forecast results. The changes in received power at each receiving point were analyzed according to the location of the transmitter and the frequency band variation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.5
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• pp.262-269
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• 2023

Objectives: Anterior maxillary sinus wall fractures are common in all types of maxillofacial trauma. They can result in various complications, including injury to the surrounding nerves. Owing to its anatomy, trauma to the maxillary antrum can result in injury to the middle superior alveolar nerve (MSAN) and the anterior superior alveolar nerve (ASAN). The purpose of this study is to evaluate neurosensory deficits (NSD) present in maxillary gingiva, incisors, and premolars after injury to the anterior wall of the maxillary antrum. Materials and Methods: This prospective study was conducted among 39 patients sustaining unilateral fractures of the anterior maxillary sinus wall. Clinical neurosensory tests including two-point discrimination and fine touch discrimination were performed to classify the extent of nerve injuries as mild, moderate, severe, or anesthetic. Additional temperature discrimination and pulpal sensibility tests (electric pulp testing and cold testing) were carried out. A comparison of radiographic fracture patterns and severity of nerve injury was done. Testing was carried out immediately after trauma and at 2-month follow-up. Results: More than half of the patients assessed in the study group presented with NSD of the teeth and gingiva after trauma. The incidence of deficits varied with the type of test used to measure them. Most frequently, patients presented with both loss of two point as well as fine touch discrimination thresholds. Severe nerve injuries were associated with loss of temperature discrimination clinically and displaced fractures radiographically. There was no significant relationship between the recovery of pulpal and gingival sensation. The patterns of injury and recovery in ASAN and MSAN were similar. Conclusion: NSD after trauma to the maxillary antrum is relatively common. Clinical loss of temperature discrimination and radiographic signs of fracture lines passing through the canalis sinuosus are predictors of persistent and severe oral NSD.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.843-848
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• 2000

This paper deals experimently with the difference between the cabins in ship-board and the reverberation chamber in sound transmission loss. Experimental results from the cabins show that there are various flanking transmission losses which deteriorate significantly the performance of the sound transmission loss. They also show that as a representative of the flanking transmission losses, sound leakages between a ceiling and a wall, the joints of the partitions, and the luminant devices play an important role. From the various measurements, it can be is concluded that unless one do not take any treatments on the flanking transmission loss, the field sound transmission loss will be considerably decreased by more than 10 dB, comparable to the sound transmission loss.