• KSBB Journal
• /
• v.23 no.1
• /
• pp.96-100
• /
• 2008

In this work, we describes analysis of the antioxidant potential of Korean green tea phenolics using an high-performance liquid chromatography (HPLC) on-line $ABTS^{+}$ antioxidant screening method. In conjunction with the analysis of their 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS+) radical scavenging ability, the extraction of catechine compounds from Korean green tea were performed by various temperature and time. The optimum operating conditions were experimentally determined to analyze the catechine compounds in the pretreatment extracts. From the results, the extraction temperature $60^{\circ}C$, time 3 min was selected as an optimal antioxidant activity condition. The analysis by $C_{18}$ column was performed, the flow rate of mobile phase and UV wavelength was fixed at 1.0 ml/min and 254 nm, respectively. the mobile phase was composed from acetonitrile and water, and the gradient elution mode were applied.

• Journal of ILASS-Korea
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2010

As world attention has focused on global warming and air pollution, high efficiency diesel engines with low $CO_2$ emissions have become more attractive. Premixed diesel engines in particular have the potential to achieve the more homogeneous mixture in the cylinder which results in lower NOx and soot emission. Early studies have shown that the operation conditions such as the EGR, intake conditions, injection conditions and compression ratio are important to reduce emissions in a PCCI (Premixed Charge Compression Ignition) engine. In this study a modified cam was employed to reduce the effective compression ratio. While opening timing of the intake valve was fixed, closing timing of the intake valve was retarded $30^{\circ}$. Although Atkinson cycle with the retarded cam leads to a low in-cylinder pressure in the compression stroke, the engine work can still be increased by advanced injection timing. On that account, we investigated the effects of various injection parameters to reduce emission and fuel consumption; as a result, lower NOx emission levels and almost same levels of fuel consumption and PM compared with those of conventional diesel engine cam timing could be achieved with the LIVC system.

• Journal of Astronomy and Space Sciences
• /
• v.29 no.2
• /
• pp.115-121
• /
• 2012

Existing but largely unused binary star model capabilities are examined. An easily implemented scheme is parameterization of starspot growth and decay that can stimulate work on outer convection zones and their dynamos. Improved precision in spot computation now enhances analysis of very precise data. An existing computational model for blended spectral line profiles is accurate for binary system effects but needs to include damping, thermal Doppler, and other intrinsic broadening effects. Binary star ephemerides had been found exclusively from eclipse timings until recently, but now come also from whole light and radial velocity curves. A logical further development will be to expand these whole curve solutions to include eclipse timings. An attenuation model for circumstellar clouds, with several absorption and scattering mechanisms, has been applied only once, perhaps because the model clouds have fixed locations. However the clouds could be made to move dynamically and be combined into moving streams and disks. An area of potential interest is polarization curve analysis, where incentive for modeling could follow from publication of observed polarization curves. Other recent advances include direct single step solutions for temperatures of both stars of an eclipsing binary and third body kinematics from combined light and velocity curves.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.1
• /
• pp.33-47
• /
• 1992

Experimental investigation on the performance of a heat pump system using refrigerant mixtures is done. The condenser and the evaporator are double pipe heat exchangers of counter flow type and the compressor is driven by a variable speed motor. The refrigerant mixture used in the experiment is R22/R142b. Experiments are performed by changing the compressor speed, composition on ratio of mixture, and the average temperatures of condenser and evaporator. The compressor work, heating capacity and the coefficient of performance are calculated. Results show that the heating capacity can be changed by varying the mass flow rate of refrigerant mixtures to meet the heating load. It is shown that the capacity control by changing the composition ratio is more effective than by changing the compressor speed. Under the condition where the external conditions are fixed and the heating loads are equal, the coefficient of performance has its maximum value near 50 : 50 mass fraction of the refrigerant mixture in this study.

• Journal of the Institute of Convergence Signal Processing
• /
• v.2 no.1
• /
• pp.113-118
• /
• 2001

In this paper, we implement modules of the MPEG-2 AAC decoder using VHDL. Tools of Huffman decoder, inverse quantizer and high-density filter bank which are necessary for the AAC decoder. We designed the high speed Huffman decoder using the method of octal tree search algorithm, and reduced computational time of filter bank using IFFT. Also, we use table of computation result for an exponential calculation of Inverse quantizer in fixed-point hardware, and reduced the size of table using linear interpolation. Modules implemented by hardware through optimization work in real time at low clock frequency are possible to reduce the system size.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.22 no.1
• /
• pp.135-148
• /
• 1994

When we put a construction on the space organization form of Seyeon-jong garden through a consequence of drawing analysis, we were able to certify that a certain space construction principle was applied as following. First, the arrangement and organization of space construction element embodied systematic order y clearing the character of space, and heightening the degree of cognizance with the means of functionability, scale, height, decorationability, an inclination of artificiality and nature, systemetic approchability. Second, the space construction element of Seyeon-jong garden pursued a harmony of human work and nature for creating a various atmosphere and visual quality. Third, Seyeon-jong garden constructed the space by establishing the measurement of human scale that introduced a conception of near, middle, distant view on the visual angle. Forth, Yun go san introduced the natural shape of 'The song of five friends' as a construction element, and represented the symbolism that he had seeked for throught he arrangement method, christening, composing technique of the space construction element for expressing ideal space which is described in 'The four season song of fishermen' spatially at Seyeon-jong garden. As the results of this study, that Yun go san created his own ideal space that he longed for at Seyeon-jong garden with applying fixed design system, and he realized his will that he strived to form a complete whole in perfect harmony.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.7
• /
• pp.153-162
• /
• 2004

This paper describes a research work on the die design for the deep drawing ＆ ironing(D.D.I.) of high pressure gas cylinder. D.D.I die set is large-sized die used in horizontal press, which is usually composed of drawing, and ironing die. Design method of D.D.I. die set is very different from those of conventional cold forging die set.. Out diameter of the die set is fixed because of press specification and out diameter of the insert should be as small as possible for saving cost of material. In this study, D.D.I die set has been designed to consider those characteristics and the feasibility of the designed die has been verified by FE-analysis. In addition, the automated system of die design has been developed in AutoCAD R14 by formulating the applied methods to the regular rules.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.1
• /
• pp.18-34
• /
• 2014

It is widely believed that cognitive radio (CR) networks have an opportunistic nature and therefore can only support best-effort traffics without quality-of-service (QoS) guarantees. In this paper, we propose a centralized CR network that adopts interference averaging techniques to support QoS guaranteed traffics under interference outage constraints. In such a CR network, a CR user adaptively adjusts its transmit power to compensate for the channel loss, thereby keeping the receive signal power at the CR base station (BS) at a constant level. The closed-form system capacity of such a CR network is analyzed and derived for a single cell with one CR BS and multiple CR users, taking into account various key factors such as interference outage constraints, channel fading, cell radius, and locations of primary users. The accuracy of the theoretical results is validated by Monte Carlo simulations. Numerical and simulation results show promising capacity potential for deploying QoS-guaranteed CR networks in frequency bands with fixed primary receivers. Our work can provide theoretical guidelines for the strategic planning of centralized CR networks.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.31 no.2
• /
• pp.66-71
• /
• 2023

In the case of the Navy, if some of the co-pilots are included in the long-term promotion process due to the limited number of co-pilots, operational flight and administrative tasks will be added to the co-pilots not included in the rest of the Pilot in commander process. Therefore, to solve this problem, the co-pilot who has passed the PQS step-by-step process minimizes the personnel gap in the flight operation unit through a system that evaluates whether it is possible to perform its duties as a co-pilot through actual flight after entering the school. The advantage of the PQS course is that you can control flight plans on your own and minimize gaps in flight and ground work while carrying out the curriculum, but you can't focus on education or improve your skills due to irregular training flight cycles. Therefore, in this study, after collecting opinions on effective flight cycles through a survey of pilots of P-3C, the Navy's fixed-wing aircraft representative, we will analyze the association of aircraft volume performance by flight cycle to derive the optimal flight cycle of the P-3C pilot course.

• Korean Journal of Remote Sensing
• /
• v.11 no.3
• /
• pp.101-116
• /
• 1995

The fact that the demands on traffic data collection are imposed by economic and safety considerations raisese the question of the potential for complementing existing traffic data collection programs with satellite data. Evaluating and monitoring traffic characteristics is becoming increasingly important as worsening congestion, declining economic situations, and increasing environmental sensitivies are forcing the government and municipalities to make better use of existing roadway capacities. The present system of using automatic counters at selected points on highways works well from a temporal point of view (i.e., during a specific period of time at one location). However, the present system does not cover the spatial aspects of the entire road system (i.e., for every location during specific periods of time); the counters are employed only at points and only on selected highways. This lack of spatial coverage is due, in part, to the cost of the automatic counters systems (fixed procurement and maintenance costs) and of the personal required to deploy them. The current procedure is believed to work fairly well in the aggregate mode, at the macro level. However, at micro level, the numbers are more suspect. In addition, the statistics only work when assuming a certain homogenity among characteristics of highways in the same class, an assumption that is impossible to test whn little or no data is gathered on many of the highways for a given class. In this paper, a remote sensing system as complement of the existing system is considered and implemented. Since satellite imagery with high resolution is not available, digitized panchromatic imagery acquired from an aircraft platform is utilized for initial test of the feasibility and performance capability of remote sensing data. Different levels of imagery resolutions are evaluated in an attempt to determine what vehicle types could be classified and counted against a background of pavement types, which might be expected in panchromatic satellite imagery. The results of a systematic study with three different levels of resolutions (1m, 2m and 4m) show that the panchromat ic reflectances of vehicles and pavements would be distributed so similarly that it would be difficult to classify systematically and analytically remotely sensing vehicles on pavement within panchromatic range. Anaysis of the aerial photographs show that the shadows of the vehicles could be a cue for vehicle detection.