• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.703-715
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• 2017

In this paper, we analyze the channel characteristics of the long distance air-ground wideband common data link and we propose a mathematical method to analyze the effect of narrowband and wideband interference of air-ground channel on the received signal of wideband data link. In this paper, we analyze the reception performance according to the communication distance using the proposed performance analysis method, and found out that the communication distance is limited by the narrowband and wideband interference of ground reflection wave. As a result of the performance analysis of the method of controlling the receiving antenna upward, not only the narrow band but also the wideband interference is effectively reduced, so that the communication distance is increased even in the existing wideband data link not including the equalizer.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.62-69
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• 2014

This paper presents a preliminary study of a convergent divergent nozzle in an afterburning turbofan engine of a supersonic aircraft engine. In order to design a convergent divergent nozzle, cycle model of a low bypass afterburning turbofan engine of which thrust class is 29,000 lbf at a sea level static condition is established. The cycle analysis at the design point is conducted by Gasturb 12 software and one dimensional gas properties at a downstream direction of the turbine are obtained. The dimension and configuration of an model turbofan engine are derived from take-off operation with wet reheat condition. The off-design cycle calculation is conducted at the all flight envelope on the maximum flight Mach number of 2.0 and maximum flight altitude of 15,000 m.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.2
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• pp.22-30
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• 2017

PL (Product Liability) refers to the legal responsibility of a manufacturer or seller for bodily injuries or property losses caused by product defects. Therefore, it is important for companies to construct a product liability response system that strategically manage and effectively adapt to product liability. A PL response system refers to companywide operations of PL prevention (PLP) measures, product safety (PS) measures, and PL defense (PLD) measures appropriate for a company's scale and environment. To establish an enterprise product liability response system, each essential component of corporations should be systematically operated and maintained considering the scale and characteristics of the corporations. Essential components of PL response system is Strategy, Organization, Training, Technology, Investment, and Awareness. Role of essential components is that companies need specific strategies to secure product safety and protect customers from product defects, and appropriate organizations must be composed for effective operation of such strategies. The objective of this paper seeks to examine the relationships among the essential components of the product liability response system and PL performance. PL performance consists of positive performance and negative performance. In particular, positive performance include increased efforts in product or process innovation such as strengthening research and development (R&D) to produce safer products without defects. In order to carry out this research we obtained 98 questionnaire of manufacturing company. A summary of the analyses is as follows: First, the awareness and technology among essential components affect significantly to the positive performance. Second, the awareness and strategy among essential components negative affect to the negative performance.

• Composites Research
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• v.28 no.6
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• pp.395-401
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• 2015

This study investigated the thermal stability of Grubbs' catalyst and its reactivity with self-healing agents for self-healing damage repair. Four types of Grubbs' catalyst supplied by manufacturers were considered and each catalyst was tested in as-received and grinded conditions. Four types of self-healing agents were prepared by varying the mixing ratio of dicyclopentadiene (DCPD) and 5-ethylidene-2-norbonene (ENB). Heat flows as a function of temperature were measured through a differential scanning calorimetry (DSC) to determine the thermal stability of catalysts. Reaction heats of self-healing agents with the catalyst were measured to evaluate the reactivity of the catalyst. For this evaluation, Fluka Chemika Grubbs' catalyst was used based on the maximum temperature and the time to reach the maximum temperature. According to the results, catalysts had different shapes depending on the manufacturer and the results showed that the smaller the size of the catalyst the higher the reactivity with self-healing agents. As the ENB ratio in self-healing agents increased, the maximum temperature increased, and the time to reach the maximum temperature decreased. As the amount of the catalyst increased, the maximum temperature increased, and the time to reach the maximum temperature decreased. Considering the thermal stability of the catalyst and its reactivity with the self-healing agent, combination of 0.5 wt% catalyst and the D3E1 self-healing agent was optimal for self-healing damage repair. Finally, as the thermal decomposition may occur depending on the environmental temperature, the catalyst must not be exposed to temperature higher than that is necessary to maintain the thermal stability of the catalyst.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.953-958
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• 2008

The object of this study was to investigate the immune-enhancing effects of Chlorella vulgaris (CV) on a deteriorated immune function by a protein-energy malnutrition (PEM) diet. Unicellular algae, CV were used as a biological response modifier. Male C57BL/6J mice were fed for 15 days with standard diet or a PEM diet, which is associated with decreased host immune defense. After 8 days, mice in the PEM diet group were orally administered by 0.05, 0.1, and 0.15 g/kg body weight of CV or distilled water. Nutritional parameters, and interferon (IFN)-$\gamma$ levels were significantly increased in the blood serum of the CV (0.15 g/kg)-treated group (29.6$\pm$2.8 pg/mL) compared to the non-treated PEM group (4.1$\pm$0.4 pg/mL, p<0.05). In addition, cell proliferation and production of cytokines were investigated via a CV (0.01, 0.1, and 1 mg/mL) treatment using a human T cell line MOLT-4 cell. The CV treatment (1 mg/mL) significantly increased the production of both IFN-$\gamma$ and interleukin (IL)-2 (51.3$\pm$3.4 and 285.9$\pm$18.8 pg/mL, respectively) compared to the control (51.3$\pm$3.4 and 442.6$\pm$14.3 pg/mL, respectively), but did not affect the production of IL-4. These results suggest that CV may be useful in improving the immune function.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1054-1061
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• 2016

Development of an accurate infrared signature (IR) measurement system is expected to contribute in the development of low observable technology and the spectroscopic analysis of electromagnetic radiation. Application of a spectroradiometer (SR) allows for the measurement of detailed infrared signature from the exhaust plume due to its own heat source. Establishment of a measurement system using a micro-turbo engine is intended to simulate the modelling of the aircraft plume. The engine was installed on a test stand to measure the engine performance. The IR signature was measured by placing the SR perpendicular to the axis line of the exhaust plume. Reference data from the blackbody were also measured to calibrate the raw data, and the infrared signature of the background was also measured for comparison with that of the plume. The calibrated spectral radiance was obtained through the data reduction process and the results were analyzed in specific bands. The experiments revealed that the measurement system established here showed sufficient performance for further comprehensive analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.3
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• pp.32-36
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• 2016

Test equipment was designed and manufactured to evaluate thermal reaction characteristic of internal insulators of solid rocket motor. Test is allowed up to chamber pressure 2,500 psi, burn-time 100 s. A cross section of test sample part is quadrature, and various test samples can be comparable at the same time. Inner temperature of test sample can be measured by thermocouples during burning. Test was executed in condition of efficient average chamber pressure 1,000 psi, efficient burn-time 10 s and safety of equipment was confirmed. Basic data for understanding thermal characteristics of internal insulator, that is, pressure-time curve, temperature-time curve in the test sample, and thermal destruction thickness of test sample was gained successfully.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.6
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• pp.42-53
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• 2015

In this study, the influence of Al particle size, as an additive for solid propellant, on the mechanical erosion of the carbon-composite nozzle was evaluated. A new model which can predict the size and distribution of the agglomerated reaction product($Al(l)/Al_2O_3(l)$) was established, and the size of agglomerate were calculated according to the various initial size of Al in the solid propellant. With predicted results of the model, subsequently, the characteristics of mechanical erosion on the carbon-composite nozzle was estimated using a commercial CFD software, STAR CCM+. The result shows that the smaller the initial Al particles are, in the solid propellant, the lower is the mechanical erosion rate of the composite nozzle wall, especially for the nano-size Al particle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.601-608
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• 2015

The static aeroelastic analysis and optimization of flexible wings are conducted for steady state conditions while both aerodynamic and structural parameters can be used as optimization variables. The system of multidisciplinary design optimization as a robust methodology to couple commercial codes for a static aeroelastic optimization purpose to yield a convenient adaptation to engineering applications is developed. Aspect ratio, taper ratio, sweepback angle are chosen as optimization variables and the skin thickness of the wing. The real-coded adaptive range multi-objective genetic algorithm code, which represents the global multi-objective optimization algorithm, was used to control the optimization process. The support vector regression(SVR) is applied for optimization, in order to reduce the time of computation. For this multi-objective design optimization problem, numerical results show that several useful Pareto optimal designs exist for the flexible wing.

• Journal of Adhesion and Interface
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• v.5 no.3
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• pp.10-17
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• 2004

We investigated the effect of stabilization processing parameters on the thermal shrinkage, thermal stability and microstructure of rayon fabrics stabilized under various conditions such as heating rate, stabilization temperature, atmosphere gas, and chemical treatment. The presence and absence of phosphoric acid treatment and the heating rate have most importantly influenced the thermal shrinkage and the weight change of rayon fabrics. Especially, the phosphoric acid treatment decreases the reduction of thickness, length, and weight of the fabrics by about 80%, 20%, and 26%, respectively, in comparison with the untreated counterparts, showing the protective effectiveness of the thermal shrinkage involved. The thermal stability of stabilized rayon fabrics is also affected by all the processing conditions used: stabilization temperature, phosphoric acid treatment, atmosphere gas, and heating rate. In addition, the surface and diameter of the stabilized fiber significantly depend on the treatment of phosphoric acid prior to stabilization process.