• Journal of the Semiconductor & Display Technology
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• v.23 no.2
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• pp.65-70
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• 2024

Using a computational fluid dynamics(CFD) simulation tool, we have provided a coating guideline for slot-die coating with a double layer slot die head. We have analyzed the fluid dynamics in terms of the coating speed, flow rate ratio, and viscosity ratio, which are critical for the stability of coating meniscus. We have identified the common coating defects such as break-up, air entrainment, and leakage by varying the coating speeds. The flow rate ratio is the critical parameter determining the wet film thickness of the top and bottom layers. It is shown that when the flow rate ratio exceeds or equals 1.8, air entrainment occurs due to insufficient hydraulic pressure in the bottom layer, even though the total flow rate remains constant. Furthermore, we have found that the flow of the bottom layer is significantly affected by the viscosity of top layer. The viscosity ratio of 4 or higher obstructs the flow of the bottom layer due to the increased hydraulic resistance, resulting in leakage. Finally, we have demonstrated that as the viscosity ratio increases from 0.1 to 10, the maximum coating speed rises from 0.4 mm/s to 1.6 mm/s, and the minimum wet film thickness decreases from 800 ㎛ to 200 ㎛.

• The Korean Journal of Pain
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• v.30 no.4
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• pp.281-286
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• 2017

Background: Magnetic resonance imaging (MRI) of the spine is the preferred diagnostic tool for pathologic conditions affecting the spine. However, in patients receiving epidural corticosteroid injection (ESI) for treatment of spinal diseases, there is a possibility of misreading of MR images because of air or fluid in the epidural space after the injection. Therefore, we defined the characteristics of abnormal changes in MRI findings following an ESI in patients with low back pain. Methods: We reviewed the medical records of 133 patients who underwent MRI of the lumbar spine within 7 days after ESI between 2006 and 2015. All patients were administered an ESI using a 22-gauge Tuohy needle at the lumbar spine through the interlaminar approach. The epidural space was identified by the loss of resistance technique with air. Results: The incidences of abnormal changes in MRI findings because of ESI were 54%, 31%, and 25% in patients who underwent MRI at approximately 24 h, and 2 and 3 days after ESI, respectively. Abnormal MRI findings included epidural air or fluid, needle tracks, and soft tissue changes. Epidural air, the most frequent abnormal finding (82%), was observed in 41% of patients who underwent MRI within 3 days after injection. Abnormal findings due to an ESI were not observed in MR images acquired 4 days after ESI or later. Conclusions: Pain physicians should consider the possibility of abnormal findings in MR images acquired after epidural injection using the interlaminar approach and the loss of resistance technique with air at the lumbar spine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.50-55
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• 2011

The fluid power products are widely used in current industrial area such as automation of products and equipment assembly, high-tech machine tool, aircraft, train, and etc. As the development of industry is in progress, the development of the fluid power products is demanding and it is required in every industrial area. This research proposed a pneumatic system to evaluate displacement accuracy of the pneumatic actuator without external load and to analyze capability of integration of the valve system. The pneumatic system consisted of a combination of pneumatic actuator, four two-port valves, two three-port valves, two pressure valve, a check valve, two proximity sensors, and a program logic controller (PLC). The position controller is based on the PLC connected with the proximity sensors. The maximum air pressure applied for tests was $49.05N/cm^2$ and the displacement accuracy of a stroke was measured using a dial gauge. The supply- and discharge-side of air pressure and the length of the stroke of the pneumatic cylinder were varied The test of the position control of the pneumatic cylinder was carried out 50 times at each supply- and discharge-side air pressure of 24.53/34.34, 29.43/39.24, 34.34/44.15, and $39.24/49.05N/cm^2$ and replicated three times. The accuracy of the displacement of the pneumatic cylinder stroke increased as the supply- and discharge-side of air pressure increased with the stroke length of 133mm. Also the displacement accuracy increased as the stroke length increased with the fixed supply- and discharge-side of air pressure of the pneumatic cylinder as 34.34 and $44.15N/cm^2$, respectively. The most accurate displacement of the pneumatic cylinder was obtained at the supplyand discharge-side of air pressure of 39.24 and $49.05N/cm^2$, respectively, and strokes of 170 and 190mm.

• Journal of the Korean Society of Combustion
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• v.19 no.4
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• pp.14-20
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• 2014

In the present study, an annular combustor for a 500 W class micro gas turbine generator was designed and its characteristics were investigated by using both numerical and experimental methods. For this purpose, geometrical configurations of the annular combustor were determined in the aspect of the aerodynamic and chemical consideration. Also, fluid flow and pressure drop characteristics in the combustor were numerically studied by using commercial tool, FLUENT. Based on the numerical results, the diameter and the angle of air admission holes in the primary zone were chosen to be 2.5 mm and $30^{\circ}$, respectively. Finally, an integrated test unit, which consisted of a compressor, combustor, turbine, and motor/generator, was developed in order to measure the combustor efficiency. As the temperature difference between the combustor inlet and the turbine inlet or the air mass flow rate increased, the combustor efficiency increased and it was over 90% when the air mass flow rate was larger than 7.30 g/s. It was shown that the annular combustor developed in this study met the design requirement for a 500 W class micro gas turbine generator.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.1-9
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• 2016

NSS (Navigation satellite system) provides the information for determining the position, velocity and time of users in real time using satellite-networking, and is classified into GNSS (Global NSS) and RNSS (Regional NSS). Although GNSS services for global users, the exactitude of provided information is dissatisfied with the degree required in modern systems such as unmanned system, autonomous navigation system for aircraft, ship and others, air-traffic control system. Especially, due to concern about the monopoly status of the countries operating it, some other countries have already considered establishing RNSS. The RNSS services for users within a specific area, however, it not only gives more precise information than those from GNSS, but also can be operated independently from the NSS of other countries. Thus, for Korean RNSS, this paper suggests the methodology to design the satellite constellation considering the regional features of Korean Peninsula. It intends to determine the orbits and the arrangement of navigation satellites for minimizing PDOP (Position dilution of precision). PGA (Parallel Genetic Algorithm) geared to solve this nonlinear optimization problem is proposed and STK (System tool kit) software is used for simulating their space flight. The PGA is composed of several GAs and iterates the process that they search the solution for a problem during the pre-specified generations, and then mutually exchange the superior solutions investigated by each GA. Numerical experiments were performed with increasing from four to seven satellites for Korean RNSS. When the RNSS was established by seven satellites, the time ratio that PDOP was measured to less than 5 (i.e. better than 'Good' level on the meaning of the PDOP value) was found to 94.3% and PDOP was always kept at 10 or less (i.e. better than 'Moderate' level).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.638-647
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• 2003

Triangular patches have been studied, both theoretically and experimentally. We feund that provided radiation characteristics similar to those of rectangular patches, but with smaller size. In this paper, we designed an equilateral triangular microstrip patch antenna using cavity model analysis. Then, in order to improve narrow bandwidth, we add capacitive gap and air gap. Capacitive gap is located with square shape beside feeding point on the patch, and air gap is inserted between substrate dielectric and ground plane to adjust probe inductance. The analysis of characteristics and effects of each component was performed by commercial simulation tool, Ensemble 5.0. Throughout the simulation and experiment, we found the possibility of bandwidth enhancement in triangular microstrip antenna.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.39-47
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• 1987

The records of 268 patients, who were diagnosed as spontaneous pneumothorax during the period 1975 to 1984, treated at the department of thoracic and cardiovascular surgery, Hanyang University Hospital, were reviewed retrospectively to evaluate the effect of surgical intervention on each indications. Of these,.61 patients [22.8%] were taken operation to treat the pneumothorax after closed thoracostomy. We have classified the 61 patients to evaluate the therapeutic effect on each indications. And the therapeutic effect is based on the chest tube indwelling days. The results were as follows: 1. The chest tube indwelling days of the group who were taken closed thoracostomy only was average 14.13*9.17 days [range 5-66 days], and that of the group who were finally taken the thoracotomy after closed thoracostomy was 21.85*12.30 days [range 5-55 days]. 2. The indications of thoractomy were thoracoscopic findings, recurrence and continuous air leakage. 3. The chest tube indwelling day of the group who was taken thoracotomy by thoracoscopic findings was average 11.67*6.51 day, that was relatively short compared to those of the other groups. 4. The continuous air leakage group after closed thoracostomy was subdivided into three subgroups, continuous air leakage in 1st attack, thoracoscopic findings in 1st attack, and recurrence. 5. Of these, the chest tube indwelling day of the subgroup, who was taken operation by thoracoscopic findings, was 21.33e8.26, that was relatively short compared with those of the other subgroups. We use the thoracoscope as excellent diagnostic tool to detect the operation indication in the spontaneous pneumothorax patients. And we gain the benefits to shorten the chest tube indwelling days and admission days, and also to protect the recurrence.

• Archives of design research
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• no.18
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• pp.53-60
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• 1996

A Human desire to improve the quality of living, intends to share, along with increase of the income, more importance(in the form of money and time) on the leisure and sport activity. This study has been motivated to create a design a tool(product) which will effectively and variously improve the joy of leisure and sports activity In the course of the design work; 1 We collected and reviewed all the On-Land Runni'ng leisure and sports products in the country, 2 We investigated life styles of various ages of the end users and the consumers' environmental change, to find a market pOSSibility, and 3. A good deal of consideration has been made to find the Korean folk (traditlonal)pastlme culture and to apply It into a possibility of globalization The investigation and analysis work provided a base to designing of "Air-Inflated Road Ski ", Which is completely a new form of leports product. which will help well balanced strengthening of the body, and which is enjoyable in and out-door in various ways and by everybody old or young and man or womann or woman.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.283-290
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• 2007

Recently, plastic products in air-intake parts of automotive engines have become very popular due to advantages that include reduced weight, constricted cost, and lower intake air temperature. However, flow-induced noise in air-intake parts becomes a more serious problem for plastic intake-manifolds than for conventional aluminum-made manifolds. This is due to the fact that plastic manifolds transmit more noise owing to their lower material density. Internal aerodynamic noise from an Idle Speed control Actuator (ISA) is qualitatively analyzed by using a scaling law, which is expressed with some flow parameters such as pressure drop, maximum flow velocity, and turbulence kinetic energy. First, basic flow characteristics through ISA passage are identified with the flow predictions obtained by applying Computational Fluid Dynamics techniques. Then, the effects on ISA passage noise of each design factors including the duct turning shape and vane geometries are assessed. Based on these results, the preliminary low noise design for the ISA passage are proposed. The current method for the prediction of internal aerodynamic noise consists of the steady CFD and the scaling laws for the noise prediction. This combination is most cost-effective, compared with other methods, and therefore is believed to be suited for the preliminary design tool in the industrial field.

• Journal of Environmental Impact Assessment
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• v.10 no.2
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• pp.123-133
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• 2001

Gaussian dispersion model is the most widely used tool for the ground level air pollution simulation. Though in spite of the convenience there are important problems on the Pasquill- Gifford' stability classification scheme which was used to define the turbulent state of the atmosphere or to describe the dispersion capabilities of the atmosphere which was each covers a broad range of stability conditions, and that they were very site specific, and the vertical dispersion calculation formula on the case of the unstable atmospheric condition. This paper was carried out to revise the Gaussian dispension model for the purposed of increase the modeling performance and propose the revised model, which was composed of the turbulent characteristics in the unstable atmospheric conditions. The proposed models in this study were composed of the profile method, Monin-Obukhove length, the probability density function model and the lateral dispersion function which was composed of the turbulent parameters, $u_*$(friction velocity), $w_*$(convective velocity scale), $T_L$(lagrangian time scale) for the model specific. There were very good performance results compare with the tracer experiment result on the case of the short distance (<1415m) from the source, but increase the simulation error(%) to stand off the source in the all models. In conclusion, the revised Gaussian dispersion model using the turbulent characteristics may be a good contribution for the development of the air pollution simulation model.