• 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.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.32-39
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• 2013

Although space-borne satellites are useful in obtaining information all around the world, they cannot observe at a suitable time and place. In order to overcome these limitations, an airborne remote sensing system was developed in this study. It is composed of a SAR sensor and a thermal infrared sensor. Additionally GPS, IMU, and thermometer/hygrometer were attached to the plane for radiometric and geometric calibration. The brightness of SAR image varies depending on surface roughness, and capillary waves on the sea surface, which are easily generated by sea winds, induce the surface roughness. Thus, sea surface wind can be estimated using the relationship between quantified SAR backscattering coefficient and the sea surface wind. On the other hand, thermal infrared sensor is sensitive to measure object's temperature. Sea surface temperature is obtained from the thermal infrared sensor after correcting the atmospheric effects which are located between sea surface and the sensor. Using these two remote sensing sensors mounted on airplane, four test flights were carried out along the west coast of Korea. The obtained SAR and thermal infrared images have shown that these images were useful enough to monitor coastal environment and estimate marine meteorology data.

• Journal of Korean Society of Transportation
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• v.23 no.7 s.85
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• pp.181-190
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• 2005

The time required for airport process is considered more important as the airports are becoming bigger. International Civil Aviation Organization mattes this international standards and recommends not to exceed it. The passenger forecasting model is developed to predict the number of passengers at the check-in counter, and the area of formalities for departure and entry. In case of forecasting the number of outbound-passengers. the patterns of show-up lead time(SLT) at the check-in counter and lag time from check-in counter to the area of departure formalities are modeled in terms of time. On the other hand, the matter of the choice of check-in counters and areas of departure formalities are modeled in terms of space. In case of forecasting the number of inbound-passengers and transfer passengers, the time of airplane movement from arrival to block on at the gate and the time of passengers required from gate to the area of formalities for entry are modeled in terms of time. While the matter of the choice of gates and the areas of formalities for entry are modeled in terms of space. The average error of forecasting outbound-passengers and inbound-passengers is respectively 15% and 10%, which are considered excellent with the 5% error of passenger reservation information as input data. Through the development of passenger forecasting models, we assure we could provide passengers with valuable service because we allocate resource such as employees and equipments according to the degree of concentration of passengers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.681-688
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• 2013

Several problems caused by inevitable increment of airplane have been issued. The most effective solution to solve the issues is considered as establishing appropriate Air Traffic Management (ATM) that reduces aircraft's delay at an airport and intensify the airport's capacity. The purpose of this paper is to produce the optimum aircraft schedules that maximize the aircraft throughput by smooth air traffic flow near terminal area of an airport In this paper, mathematical formulations of the scheduling problem are firstly specified. Based on the mathematical modelling, an Optimization-Based Flight Scheduler that provides the optimum flight schedules for arriving aircraft is developed by introducing the Mixed Integer Linear Programming(MILP) and the Genetic Algorithms(GA). With this scheduler, we calculated the optimum schedules to compare to real schedule data from an Incheon Airport. As a result, it is validated that aircraft throughput produced by the optimum schedule is much better than that of the schedule from the Incheon airport. The optimization-based flight scheduler is expected to deal with problems due to the aircraft saturation in near future.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.35-43
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• 2014

In this paper, we propose a performance enhancement method of the target tracking system for communication signal using the monopulse and the ${\alpha}{\beta}$ filter to keep the connection of the communication system between the airplane and the ground. We suggest the minimum distance measurement method for tracking error angle of the monopulse signal instead of the generally used method of MR(Monopulse Ratio) curve, and the ${\alpha}{\beta}$ filter with variable gain for enhancement of the tracking accuracy and the probability of re-tracking the monopulse signal under the disconnection of link. We show the performance enhancement of the proposed method of monopulse system using the measured MR Curve results of the prototype system. And also, the comparison of simulation results between the ${\alpha}{\beta}$ filter with variable gain and the ${\alpha}{\beta}$ filter with fixed gain shows the performance enhancement of the proposed ${\alpha}{\beta}$ filter. Using the proposed methods, we expect the enhanced performance of the existing target tracking system for communication signal only by changing the algorithm without hardware changes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.109-117
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• 2005

Based on the previous studies on alcohol effects on human behavior and performance in transportation system such as airplane and car driving, the alcohol exposure before and on watch of a ship has a great influence on subsequent behavior. In this paper, to examine the drinking status of officers on board multiple choice questionnaires are circularized under instruction and surveyed for 118 officers. According to the results of the questionnaire survey on alcohol dependance (Alcoholism) that was invested by WHO, over 27% of those surveyed represented alcohol abuse symptoms. In addition to that, the existing state and awareness for on-board-drinking was summarized to make a scenario of drunk-operation with a ship handling simulator to investigate the effect of alcohol (0.08 g% blood alcohol concentrations) on ship operational performance. A main effect for alcohol was found indicating that ship operational performance was comparatively impaired by this alcohol relative to performance in the non-alcohol condition. The results of this research can be applied to minimize marine acciedents as basic data.

• Journal of The Korean Association For Science Education
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• v.34 no.8
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• pp.719-730
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• 2014

The purpose of this study was to investigate elementary school students' perceptions about science, engineering and technology and their images of scientists, engineers, and technicians. In order to investigate students' images of scientists, engineers, technicians and student's perception of science, engineering, and technology, we used the tools "Draw a scientist at work, Draw an engineer at work, and Draw a technician at work". We have revised the tool DAST (Draw a scientist test), which was used in Fralick et al.'s study (2009). Subjects were 209 6th grade students sampled from an elementary school in G-city in Korea. According to the results of this study, the students' representative image of a scientist was similar to stereotypical scientist image in previous studies, but the students perceived science as a field of research with various professionals. The students' representative image of an engineer was a man with short hair, no beard or mustache, wearing ordinary clothes but no glasses. The engineer was designing or constructing a ship, a robot, a computer, and an airplane. The students' representative image of a technician was a man with short hair, wearing protective goggles and a mask for welding. The technician was fixing a car, a robot, a rocket, etc. and working with wrenches, hammers, screw drivers, welding machines, etc. Many students didn't perceive engineering and technology as fields of research. Also, many students didn't variously perceive engineering and technology as fields and ways of study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.219-226
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• 2010

The stamping process is widely used in fabricating various sheet-parts for vehicle, airplane, and electronic devices due to its low processing cost and high productivity. Recently the use of thin sheets with corrugated structures has rapidly increased for the production of energy devices, e.g., heat exchangers and fuel cells. However, it is very difficult to make corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, this paper proposes a multi-step stamping process with a combined heat treatment process: a sequence of the first stamping, heat treatment, and second stamping. By multi-stamping, we obtained successful results in fabricating very thin corrugated structures with thicknesses of $100{\mu}m$; these are applicable as part of a plate-type heat exchanger.

• Journal of IKEEE
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• v.19 no.3
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• pp.415-423
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• 2015

The DO-178C guide, which is referenced as the software development guide when a certification of the airworthiness in the commercial airplane is acquired by FAA in US, is recently referenced for the local military aircraft airworthiness. This indicates that when the auditor of the military aircraft airworthiness looks over the software development documents, the auditor reviews if all of the documents are verified in accordance with the DO-178C guide. However, when we developed the military aircraft intercom, We developed its control software in accordance with the CMMI level 3, since there were no requirements for the compliance of the DO-178C guide. Therefore, When we consider the airworthiness of this intercomm system, The analysis for how much the software development based on the CMMI level 3 is different from the DO-178C guide is needed to prepare the essential software documents additionally. Thus, This study analyzes the differences between CMMI level 3 and DO-178C guide and provides that which data on the CMMI level 3 is necessary for the compliance of the aircraft airworthiness comparing with the DO-178C. The analyzed result can be applied at the software development of the other military aircraft avionics equipment based on the CMMI model environment considering the compliance of the military aircraft airworthiness.

• Reproductive and Developmental Biology
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• v.33 no.4
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• pp.257-262
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• 2009

This study was to investigate pregnancy rate of IVM/IVF/IVC Korean cattle (registered in government) embryos according to transport time course. For the production of embryos, oocytes recovered from slaughtered excellent grade cow and highly motile frozen-thawed bull semen (purchased from LIMC, KPN#497) was used. In vitro produced embryos were cultured in CR1aa medium for 8 days and some of them were frozen. The rate of average cleavage (>2-cell) was 83.0% (308/371) and blastocyst rate at day 8 was 34.7% (107/308). Among in vitro produced blastocyst embryos at day 8, most healthy embryos were freshly transferred on production day and some frozen embryos were direct transferred on appropriate day. These embryos were produced in a laboratory, embryo transfer (ET) was planned in 10 areas of the remote island (Jeju) from the laboratory by airplane. Thus, we examined the pregnancy rate in recipient cow according to embryo of transport time course before ET. From embryo transferred 44 recipient cows, overall pregnancy was 40.9% (18/44), these 18 cows were all calved [single, 94% (17/18); twin, 6% (1/18)] and total embryo implantation rate was 26% (19/66). Comparing transport time in the base of 6 hr, pregnancy rate in ET group required less 4 hr (60%, 9/15) was significantly higher than that required more 6 hr (26.3%, 5/19). In direct ET of freezing embryos, the pregnancy rate was 40% (4/10). However, it was difficult to find the meaning of temperature, pH and corpus luteum quality of recipients on comparison of pregnancy rate. When the cell death level of embryos according to storage time in thermos (straw container) before ET was measured by TUNEL staining, apoptotic index was increased with storage time-dependent. These results demonstrated that long distance transfer of IVM/IVF/IVC embryos is possible and the time of embryo transport is very important for the pregnancy rate on field trial.