• Journal of the Korean Society of Visualization
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• v.19 no.1
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• pp.94-99
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• 2021

In order to increase the efficiency of thermoelectric refrigerators using the Peltier effect, it is necessary to optimize the distribution of the flow of cold air from the fan. In this study, the flow flowing upwards and downwards while changing the area of the flow path was visualized using the PIV technique for the control of cold air in a thermoelectric refrigerator. From these results, the flow rate according to the change in the area of the flow path was confirmed, and design criteria for optimizing the distribution of cold air flowing to the top and bottom of the refrigerator were suggested.

• The Journal of Economics, Marketing and Management
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• v.6 no.1
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• pp.25-30
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• 2018

Purpose - This paper mainly studied the role of the logistics legal system in promoting international transport logistics, building marine economy international cooperation demonstration zone and deepening the economic and financial cooperation etc between China and Korea. Research design, data, and methodology - The study conducted a survey on China and Korea's 2012-2017 years data. After empirically analyzing the data, we believe that cultural industry in Korea and China will maintain its growth momentum. Results - This study explored the way to establish an integrated logistics system between China and Korea to match the e-commerce certification system, online payment system and logistic distribution, thereby gradually promoting economic development and logistics integration in Asia. Conclusions- China-Korea FTA can encourage private flow to take on enterprises. In terms of improving logistics efficiency, reducing logistics costs and establishing a unified logistics industry standardization system. This will accelerate logistics industry integration in Northeast Asia, build a unified logistics management center in Northeast Asia, and promote a new model of integrated logistics cooperation in Northeast Asia. Therefore, it has a practical and reference significance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.939-942
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• 2007

Vacuum cleaner is a close life product that can remove various dusts from our surroundings. However well vacuum cleaner clean our environments, many people are looking away from it, due to its loud noise. Its noise causes a big trouble in the usual life, for example, catch calls, TV watching and discussing etc. To reduce these inconveniences, noise reduction methods and systematic design of low noise vacuum cleaner are studied in this paper. At first, sound quality investigation is performed to get the noise level and quality that make people TV watching and catch calls available. Based on the European and domestic customer SQ survey result, sound power, peak noise level and target sound spectrum guideline are studied and introduced. As a second, precise product sound spectrums are designed into each part based on the sound quality result. Fan-motor, brush, mainbody, cyclone spectrums are decided to get the final target sound based on the contribution level. Fan-motor is the major noise source of vacuum cleaner. Specially, its peak sound, RPM peak and BPF Peak, cause the people nervous. To reduce these peak sounds, high rotating impeller and diffuser are focused due to its interaction. A lot of experimental and numerical tests, operation points are investigated and optimization of flow path area between diffusers is performed. As a bagless device, cyclones are one of the major noise sources of vacuum cleaner. To reduce its noise, previous research is used and adopted well. Brush is the most difficult part to reduce noise. Its noise sources are all comes from aero-acoustic phenomena. Numerical analysis helps the understanding of flow structure and pattern, and a lot of experimental test are performed to reduce the noise. Gaps between the carpet and brush are optimized and flow paths are re-designed to lower the noise. Reduction is performed with keeping the cleaning efficiency and handling power together and much reduction of noise is acquired. With all above parts, main-body design is studied. To do a systematic design, configuration design developments technique is introduced from airplane design and evolved with each component design. As a first configuration, fan-motor installation position is investigated and 10 configuration ideas are developed and tested. As a second step, reduced size and compressed configuration candidates are tested and evaluated by a lot of major factor. Noise, power, mass production availability, size, flow path are evaluated together. If noise reduction configuration results in other performance degrade, the noise reduction configuration is ineffective. As a third configuration, cyclones are introduced and the size is reduced one more time and fourth, fifth, sixth, seventh configuration are evolved with size and design image with noise and other performance indexes. Finally we can get a overall much noise level reduction configuration. All above investigations are adopted into vacuum cleaner design and final customer satisfaction tests in Europe are performed. 1st grade sound quality and lowest noise level of bagless vacuum cleaner are achieved.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.12-25
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• 2017

In local underground mines heavily depending on the natural ventilation, ducted fan auxiliary ventilation system is strongly recommended instead of the total mine ventilation system requiring large capital and operating costs. Optimizing the installation of ducted fans in series in long large-opening mines is required to assure the economy and efficiency of the ventilation system. The two most critical design parameters for optimization are the wall separation distance and gap length between adjoining ducts. This study aims at deriving the optimal values for those two parameters concerning the economic and environmental aspects through the extensive CFD analysis, which minimizes pressure loss, leakage and entrainment of the contaminated air in the gap space. The ranges of the wall separation distance and gap length for study are selected by taking into consideration the existing recommendations and guidelines. The ultimate goal is to optimize the auxiliary ventilation system using ducted fans in series to provide a reliable and efficient solution to maintain clean and safe workplace environment in local long underground mines.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.35-40
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• 2015

Centrifugal pumps consume considerable amounts of energy in various industrial applications. Therefore, improving the efficiency of pumps machine is a crucial challenge in industrial world. This paper presents numerical investigation of flow characteristics in volutes of centrifugal pumps in order to compare the energy consumption. A wide range of volumetric flow rate has been investigated for each case. The standard k-${\varepsilon}$ is adopted as the turbulence model. The impeller rotation is simulated employing the Multi Reference Frames(MRF) method. First, two different conventional design methods, i.e., the constant angular momentum(CAM) and the constant mean velocity (CMV) are studied and compared to a baseline volute model. The CAM volute profile is a logarithmic spiral. The CMV volute profile shape is an Archimedes spiral curve. The modified volute models show lower head value than baseline volute model, but in case of efficiency graph, CAM curve has higher values than others. Finally for this part, CAM curve is selected to be used in the simulation of different cross-section shape. Two different types of cross-section are generated. One is a simple rectangular shape, and the other one is fan shape. In terms of different cross-section shape, simple rectangular geometry generated higher head and efficiency. Overall, simulation results showed that the volute designed using constant angular momentum(CAM) method has higher characteristic performances than one by CMV volute.

• Particle and aerosol research
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• v.15 no.4
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• pp.139-148
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• 2019

This study was performed for the application of a high-speed centrifugal cyclone to shale gas mining process. This device uses the centrifugal force to control particles similar to typical cyclones, and the disk located inside the cyclone is forced to rotate using a motor. The pressure difference occurred during the rotating of disk. Hence, inflow rate was generated without a blower fan. In addition, flow rate increased with elevating rpm of motor. The installing the disk in multiple stages on the inner rotor increased the instantaneous disk outlet flow. Hence, the control efficiency of oil particle increased from 1.05% to 31.2%. By modifying the structure of the disk so that the air flow to the opposite direction of the cyclone, the control efficiency of oil particles increased to 81.5%. By increasing the capacity of the motor and the size of the disk, the flow rate was increased to 2.5 ㎥/min because the rpm of motor and pressure difference increased. As rpm of motor increased, the cut-off diameter (d_pc) became smaller. Unlike the Lapple's equation, d_pc was inversely proportional to the effective number of rotations (N_e). The control efficiency was maintained even if the concentration of oil particles increased, for this reason, the higher the oil concentration, the more particles were accumulated and controlled.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.467-474
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• 2012

UAVs for reconnaissance and intelligence operations require long endurance capability, which demands high efficiency of the propulsion system. The distributed propulsion system(DPS) generates the thrust by replacing a large propulsion system with a number of small propulsion systems. A DPS distributed along the wing span can produce gains in propulsion efficiency by reducing ejection velocity. Also, the ingestion of boundary layers through the distributed DPS inlet and ejecting flow from the outlet can improve the lift to drag ratio of the vehicle. This study investigates the effects of locations and size of the inlet and outlet of the DPS on the blended-wing-body design based on Eppler 337 airfoil, with a CFD tool. The fans in the DPS are modeled as actuator disks for computational efficiency. The best location and aspect ratio of the inlet and outlet are found from lift-to-drag ratio and pitching moment considerations.

• Fire Science and Engineering
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• v.20 no.4 s.64
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• pp.135-142
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• 2006

The experiment applied Positive Pressure Ventilation to rapidly exhaust heat and smoke inside the construction in the fire was done. Changes of heat discharge and smoke density were measured, with the various blowing condition like a fan tilting angle to find the effect of the parameter. Experimental apparatus were with PPV and water mist system for better efficiency, and investigate the effect of heat discharge and smoke removal. In the experiment, flame temperature has decreased when PPV was applied. Smoke density, generated from fire also decreased dramatically and the efficiency showed the highest rate at $0^{\circ}$ tilting angle. In addition, combination of PPV and water mist system highly improved the efficiency of evacuation on heat and smoke density, clearly was influenced by the tilting angle.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.717-726
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• 2020

The physical characteristics of the major varieties of perilla were analyzed to use as basic data for the design of a high-quality, high-efficiency perilla cleaner and stone separator. Because the size, thousand-grain weight, angle of repose, angle of friction, bulk density and terminal velocity of perilla have significant differences according to the perilla variety, the different of characteristics by variety should be considered for performance improvement of a perilla cleaner and stone separator. Therefore the cleaner and stone separator using a sieve could be improved by the application of a detachable sieve or by using equipment such as a 2 - 3 stage sieve and regulating the slope. Moreover, because differences in the terminal velocity occur due to the differences in the size and thousand-grain weight according to the perilla variety, a blower with an adjustable fan speed was considered for the design of the improved cleaner. Additionally, it was shown that the length of perilla has the greatest correlation based on a comparison of the coefficients of the other characteristics. Accordingly, the length of perilla could be used as a major factor for the fine adjustment and parts replacement of the device. These results can be used as basic data for a high-quality, high-efficiency perilla cleaner and stone separator. In the future, the development of the machine and follow-up studies based on the basic data are needed to determine the optimized operating conditions and mechanism of action.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.233-240
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• 2023

p-type Tunnel Oxide Passivating Contacts (TOPCon) solar cell is fabricated with a poly-Si/SiO_x structure. It simultaneously achieves surface passivation and enhances the carriers' selective collection, which is a promising technology for conventional solar cells. The quality of passivation is depended on the quality of the tunnel oxide layer at the interface with the c-Si wafer, which is affected by the bond of SiO formed during the subsequent annealing process. The highest cell efficiency reported to date for the laboratory scale has increased to 26.1%, fabricated by the Institute for Solar Energy Research. The cells used a p-type float zone silicon with an interdigitated back contact (IBC) structure that fabricates poly-Si and SiO_x layer achieves the highest implied open-circuit voltage (iV_oc) is 750 mV, and the highest level of edge passivation is 40%. This review presents an overview of p-type TOPCon technologies, including the ultra-thin silicon oxide layer (SiO_x) and poly-silicon layer (poly-Si), as well as the advancement of the SiO_x and poly-Si layers. Subsequently, the limitations of improving efficiency are discussed in detail. Consequently, it is expected to provide a basis for the simplification of industrial mass production.