• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.2
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• pp.88-102
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• 2016

This paper considers the allocation and engagement scheduling problem of interceptor missiles, and the problem was formulated by using MIP (mixed integer programming) in the previous research. The objective of the model is the maximization of total intercept altitude instead of the more conventional objective such as the minimization of surviving target value. The concept of the time window was used to model the engagement situation and a continuous time is assumed for flying times of the both missiles. The MIP formulation of the problem is very complex due to the complexity of the real problem itself. Hence, the finding of an efficient optimal solution procedure seems to be difficult. In this paper, an efficient genetic algorithm is developed by improving a general genetic algorithm. The improvement is achieved by carefully analyzing the structure of the formulation. Specifically, the new algorithm includes an enhanced repair process and a crossover operation which utilizes the idea of the PSO (particle swarm optimization). Then, the algorithm is throughly tested on 50 randomly generated engagement scenarios, and its performance is compared with that of a commercial package and a more general genetic algorithm, respectively. The results indicate that the new algorithm consistently performs better than a general genetic algorithm. Also, the new algorithm generates much better results than those by the commercial package on several test cases when the execution time of the commercial package is limited to 8,000 seconds, which is about two hours and 13 minutes. Moreover, it obtains a solution within 0.13~33.34 seconds depending on the size of scenarios.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.94-100
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• 2016

A novel optical design for high resolution, large field of view (FOV) and multispectral remote sensing is presented. An f/7.3 Korsch and two f/17.9 Cook three-mirror optical systems are integrated by sharing the primary and secondary mirrors, bias of the FOV, decentering of the apertures and reasonable structure arrangement. The aperture stop of the Korsch system is located on the primary mirror, while those of the Cook systems are on the exit pupils. High resolution image with spectral coverage from visible to near-infrared (NIR) can be acquired through the Korsch system with a focal length of 14 m, while wide-field imaging is accomplished by the two Cook systems whose focal lengths are both 13.24 m. The full FOV is 4°×0.13°, a coverage width of 34.9 km at the altitude of 500 km can then be acquired by push-broom imaging. To facilitate controlling the stray light, the intermediate images and the real exit pupils are spatially available. After optimization, a near diffraction-limited performance and a compact optical package are achieved. The sharing of the on-axis primary and secondary mirrors reduces the cost of fabrication, test, and manufacture effectively. Besides, the two tertiary mirrors of the Cook systems possess the same parameters, further cutting down the cost.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.156-160
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• 2007

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.

• Journal of the Korean Home Economics Association
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• v.42 no.5
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• pp.53-76
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• 2004

This study conducted a survey on sexuality for the purpose of substantial verification, focusing on literature reviews of premarital sexuality. The Literature reviews included relevant studies of our society and its cultures such as premarital sexuality and behaviors, expressions of love or intimacy, contraception, abortion, sex education and sexuality in family contexts. The survey was conducted to 355 university students and 200 working premarital adults in Seoul, Gyeonggi and Gangwon areas. It has 21 questions to measure sexuality by sexual altitude sentence completion Scale (composed of 4 categories and options of the other items)which has been widely used by professional counsel institutes. Male and female students complete the sentence of this scale, then similar contents were classified. Love type test was developed by Hendrick & Hendrick (1986) was used to measure love and intimacy. Results from the sentence completion for sexuality attitudes are generally as follows: First of all, there was clear difference in male md female responses about each categories. For example, With regard to the questions on premarital sex with opposite sex friends of long time relationship, more than half of male students said it is all right, whereas more than half of female students answered to the same questions that it can never be possible, with many answering 'I don't know', or leaving them unanswered. The survey result, masturbation answered that Female is needed however many Females actually don't it. But Male is almost necessary and conduct himself. On questions regarding, Homosexuality is both male and Female answered opposed. These results of the study show that premarital adults clearly open to issues on sexuality compared with the past, but they have not established their own sexual identity, which can be seen with big gap between male and female perspectives, due to experiencing confusion under the changing environment of the society.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.256-259
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• 2008

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some ejectors with a various of nozzle throat and mixing chamber diameter were manufactured precisely and tested for the comparison with the calculation results.

• Journal of Advanced Navigation Technology
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• v.24 no.1
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• pp.1-8
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• 2020

In this research, we develop an airborne equipment radiating S/C-band signal to a target located at a long distance. RF interface of the equipment comprises band-specific transmitters and an broadband antenna to satisfy EIRP(effective isotropic radiated power) requirements. The equipment is in a shape of a POD like an aircraft fuel tank. The measured weight of the equipment is 119.8 kg, the CG(center of gravity) is 1391.35 mm and the MOI(moment of inertia) are 46.07 ± 0.05(I_yy) kg·㎡, 45.36 ± 0.09(I_zz) kg·㎡. All results are found to meet the requirements for aircraft installation. To verify flight safety, EMI(electromagnetic interference) tests (RE102, CE102), environmental tests (high/low temperature operation, altitude), intra-system EMC(electromagnetic compatibility) and HERP(hazards electromagnetic radiation personnel) tests have been conducted and all the test results met the requirements. It is confirmed that the equipment could be mounted on the aircraft by meeting all electrical and mechanical requirements.

• The KSFM Journal of Fluid Machinery
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• v.19 no.2
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• pp.5-10
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• 2016

Gas flow measurement in a closed duct was performed using multi-point Pitot tubes. Measurement uncertainty was assessed for this measurement method. The method was applied for the measurement of air flow into a gas turbine engine in an altitude engine test facility. 46 Pitot tubes, 15 total temperature Kiel probes and 9 static pressure tabs were installed in the engine inlet duct of inner diameter of 264 mm. Five tests were done in an airflow range of 2~10 kg/s. The flow was compressible and the Reynolds numbers were between 450,000 and 2,220,000. The measurement uncertainty was the highest as 6.1% for the lowest flow rate, and lowest as 0.8% for the highest flow rate. This is because the difference between the total and static pressures, which is also related to the flow velocity, becomes almost zero for low flow rate cases. It was found that this measurement method can be used only when the flow velocity is relatively high, e.g., 50 m/s. Static pressure was the most influencing parameter on the flow rate measurement uncertainty. Temperature measurement uncertainty was not very important. Measurement of boundary layer was found to be important for this type of flow rate measurement method. But measurement of flow non-uniformity was not very important provided that the non-uniformity has random behavior in the duct.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.563-570
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• 2017

Experimental and numerical studies were performed to investigate the performance and internal flow characteristics of a supersonic second throat exhaust diffuser (STED) with back pressure ($P_a$). An ejector system was used to vary the back pressure ($P_a$) conditions. The operating gas for the STED and the ejector was high pressure nitrogen at room temperature. When the back pressure ($P_a$) at a constant nozzle inlet pressure $P_0$) decreases, the pressure recovery location moves downstream. If the pressure ratio $P_0/P_a$) is the same, even if the nozzle inlet pressures $P_0$) are different, the diffuser's internal flow pattern and starting pressure ratio ($(P_0/P_a)_{st}$) are almost the same.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.146-159
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• 2014

In this study, we evaluated the temporal changes of water quality in the 90 reservoirs in Korea and the relationships between water quality and their environmental factors in the reservoirs for effective management of reservoirs. The majority of study reservoirs were categorized as the eutrophic state based on Carlson's trophic index. Among 90 reservoirs, more than 55.0% were nutrient-rich based on $TSI_{TP}$ in each month, where more than 50.0% were nutrient-rich based on $TSI_{Chl-a}$ from June to November. Seasonal Mann-Kendall test was used to analyze temporal variation of water quality in the selected 60 reservoirs using monthly data from 2004 to 2008. The results showed that 27 (45.0%) reservoirs showed the improvement of water quality based on TP and Chl-a concentrations, while 14 (23.3%) and 11 (18.3%) reservoirs displayed the degradation of water quality based on TP and Chl-a concentrations, respectively. Meanwhile, a self-organizing map classified the study reservoirs into five groups based on differences of hydrogeomorphology (altitude, catchment area, bank height, lake age, etc.). Physicochemical factors and land use/cover types showed clear differences among groups. Finally, hydrogeomorphology of reservoirs were related to water quality, indicating that the hydrogeomorphological characters strongly affect water quality of reservoirs.

• Journal of the Korean Home Economics Association
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• v.43 no.3 s.205
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• pp.59-73
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• 2005

The purpose of this study was to investigate the relationships between children's self-efficacy, parental child-rearing attitude perceived by the child, and creativity. The study subjects were 120 5th and 6th graders at elementary school in Gyeongbuk. The instruments of measurement were question sheets, Self-Efficacy Scale, and Parental child-rearing attitude Scale. For creative thinking tests, the Kim Yong-Chae version of TTCT (Torrance Test of Creative Thinking) was used. The data were analysed through mean, standard deviation, frequency, percentile, Cronbach's $\alpha$, and Pearson's Correlation Coefficient. The major findings of this study were as follows: First, the results from the correlational analysis didn't yield significant and meaningful correlations between children's self-efficacy and thinking creatively with words. Nevertheless, children's self-efficacy was partly related to thinking creatively with pictures. Second, the results from the correlational analysis didn't yield significant and meaningful correlations between warmth vs. rejection altitude of father and thinking creatively with words. Warmth vs. rejection attitudes of father was not related to thinking creatively with pictures. However, the results from the correlational analysis yielded a number of significant and meaningful correlations between self-control vs. regulation attitudes of father and the thinking creatively with words. The self-control vs. regulation attitudes of father was significantly positively related to the thinking creatively with pictures. Third, the warmth vs. rejection attitudes of mother was significantly positively related to the thinking creatively with words. However the warmth vs. rejection attitudes of mother was not related significantly to the thinking creatively with pictures. The self-control vs. regulation attitudes of mother was not related to the thinking creatively with words. Moreover, self-control vs. regulation attitudes of mother was not related to the thinking creatively with pictures.