• Journal of the Korean Chemical Society
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• v.24 no.3
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• pp.193-200
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• 1980

The crystal structure of N-acetyl-L-cysteine, $C_5H_9NO_3S,$ has been determined from three dimensional photographic intensity data $(CuK{\alpha}$ radiation) by single crystal X-ray diffraction analysis. There is one formula unit in the triclinic unit cell with a = 7.04(3), b = 5.14(2), c = 8.25(3) ${\AA}$, ${\alpha}$ = 106(2), ${\beta}$ = 51(1), ${\gamma}$ = 124(2)$^{\circ}$ and space group P$_1$, The structure was solved by the direct method and refined by the full matrix least-squares method. The final R value is 12.3% for 629 observed reflections. The C-carboxyl group and the N-acetyl group are very neary planar. The molecule appears to form with neighboring molecules a hydrogen bond, $O-H{\cdot}{\cdot}{\cdot}O(3)$ of length 2.59${\AA}$.

• Journal of the Speleological Society of Korea
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• no.95
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• pp.15-21
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• 2009

Global village warming and carbon dioxide CO2 gas, and the human efforts for their healing and necessary alternative technology would be much more difficult things than that of making necessary funds and efforts to lay to sleep angry nature on the earth. The limited natural resources of fossil fuel would be dried up in several decades, and the intensity of diplomatic negotiations for natural resource guarantee among countries may be showed looking alike an war. The drain of fossil fuel called a new word of alternative policy like an environment-friendly green-growth, and the solar-cell and lighting technology for the solar energy applications were developed still more repeatedly day by day from oil lantern to LED high-tech illumination in great economy. Therefore, it was studied that the low-carbon green-growth illumination technology in cave applications with SOLAR-LED system which was produced and unified in connection with solar-cell and LED from the semiconductor production technology, and it was also clarified in necessary with useful cave lighting in heatless and with no photosynthesis of plant production in underground space.

• Journal of Life Science
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• v.25 no.6
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• pp.615-623
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• 2015

This study investigated the effects of dissolved cement powder on Zacco koreanus by analyzing morphophysiological changes. The gills exposed to dissolved cement powder developed abnormal shapes in their secondary lamellae and increased numbers of mucous cells after long-term exposure. Additionally, clubbing, edema, and exfoliation of the epithelial cells were observed in the secondary lamellae. In the kidney tissue, the space in Bowman’s capsule was widened, and in the integument tissue the arrangement of the dermis was irregular due to the thinned epidermis. These results suggest that long-term exposure to cement powder can significantly affect morphological change, resulting death. The activities of antioxidant enzymes and LDH tended to increase commensurately with the duration of cement exposure. It was concluded that up-regulated proteins were the stress proteins involved in myofibrillar-protein production and down-regulated proteins were involved in glycolysis and energy metabolism after the integument’s exposure to cement. According to these results dissolved cement powder is a serious threat to the survival of fish because it causes morphological changes and weakens physiological activity in Z. koreanus tissues.

• Restorative Dentistry and Endodontics
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• v.16 no.1
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• pp.106-120
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• 1991

The main purpose of this study was to investigate the possibility of obstruction of dentinal tubules through irradiation of the $CO_2$ laser on the dentin surface. For this study, 104 extracted caries - free premolars and molars were grinded their mesial or distal surface to expose dentin completly. And these specimens were divided into three Groups. Group I : those with their smear layer not removed and Group IT : those with their smear layer removed, were irradiated by the $CO_2$ laser(SPACE LASER - $CO_2$ VEGA 25) at five different energy levels ranging 4 - 20J/$cm^2$, and all specimens were observed with scanning eletron microscope (Hitachi S - 450). Group m was divided into 2 sub - groups: one with smear layer, another one without and those were irradiated with $CO_2$ laser of the same condition as Group I & II. All specimens were immersed in, $37^{\circ}C$, 0.5% methylene blue solution for 48 hours after 100 times of thermocycling at $4^{\circ}C$ and $60^{\circ}C$, and were observed with stereo -light microscope (Olympus SZH - ILLD) to evaluate dye penetration. The following results were obtained; 1. The dentinal tubules were obstructed through laser irradiation. 2. The dentinal tubules were still obstructed after treatment of 10% HCl/2sec., then it was proved that acid resistance of detin surface was also increased. 3. The Group of laser irradiation showed less dye penetration than control Group. 4. The smear layer hardly affected obstruction of the dentinal tubules through laser irradiation.

• Advanced Composite Materials
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• v.18 no.3
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• pp.265-285
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• 2009

Off-axis compressive deformation behavior of a unidirectional CFRP laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis compressive and tensile behaviors at an equal strain rate, the effect of different loading modes on the flow stress level, rate-dependence and nonlinearity of the off-axis inelastic deformation is elucidated. The experimental results indicate that the compressive flow stress levels for relatively larger off-axis angles of $30^{\circ}$, $45^{\circ}$ and $90^{\circ}$ are about 50 percent larger than in tension for the same fiber orientations, respectively. The nonlinear deformations under off-axis tensile and compressive loading conditions exhibit significant strain-rate dependence. Similar features are observed in the fiber-orientation dependence of the off-axis flow stress levels under tension and compression and in the off-axis flow stress differential in tension and compression, regardless of the strain rate. A phenomenological theory of viscoplasticity is then developed which can describe the tension-compression asymmetry as well as the rate dependence, nonlinearity and fiber orientation dependence of the off-axis tensile and compressive behaviors of unidirectional composites in a unified manner. It is demonstrated by comparing with experimental results that the proposed viscoplastic constitutive model can be applied with reasonable accuracy to predict the different, nonlinear and rate-dependent behaviors of the unidirectional composite under off-axis tensile and compressive loading conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.798-802
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• 2013

In a conventional DC power supply used for CO2 laser, the circuit elements such as a rectifier bridge, a current-limiting resistor, a high voltage switch, energy storage capacitors ans a high-voltage isolation transformer using high turn ratio are necessary. Consequently, those supplies are expensive and require a large space. Thus, laser resonator and power supply should be optimally designed. In this paper, we propose a new power supply using high frequency resonance phenomena for CW(Continuous wave) CO2 laser (maximum output of 23W with discharge length of 450mm). It consists of a transformer including leakage inductance, magnetizing inductance and half-bridge converter, a three-stage Cockcroft-Walton and PFC(Power factor correction) circuit. The output ripple voltage can be controlled the minimum of 0.24% under the high frequency switching of 231kHz. Furthermore, the output efficiency was improved to 16.4% and the laser output stability of about 5.6% was obtained in this laser system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.1028-1036
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• 2000

In this paper, an error-resilient image compression technique using wavelet transform is proposed. The zerotree technique that uses properties of statistics, energy and directions of wavelet coefficients in the space-frequency domain shows effective compression results. Since it is highly sensitive to the propagation of channel errors, evena single bit error degrades the whole image quality severely. In the proposed algorithm, the image is encoded by the SPIHT(Set Partitioning in Hierarchical Trees) algorithm using the zerotree coding technique. Encoded bitstreams are partitioned into some blocks using the subband correlations and then fixed-length blocks are made by using the effective bit reorganization algorithm. finally, an effective bit allocation technique is used to limit error propagation in each block. Therefore, in low BER the proposed algorithm shows similar compression performance to the zerotree compression technique and in high BER it shows better performance in terms of PSNR than the conventional methods.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1479-1485
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• 2012

The parking management system can increase driver's convenience with detailed parking information service in the parking lot. At the same time, parking management system consumes non-negligible electrical energy with large amount of sensors, displays and control modules. With the increase in the demand for green and sustainable building design all over the world, it becomes a meaningful issue for parking management system to reduce operating power. This paper presents the preliminary design and estimated results of a parking management system which is optimized to reduce the power consumption mainly on detectors and displays. The system design is based on pre-developed wireless parking detectors, Park Tile and Park Disk. The system has a number of parking space detectors, vehicle count detectors, information displays, guidance terminals and other control units. We have performed system architecture design, communication network design, parking information service scenario planning, battery life regulation and at last operating power estimation. The estimated operating power was 0.93KW per parking-slot, which is 20% of traditional systems. The estimated annual maintenance cost was 18% of traditional systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.3
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• pp.265-273
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• 2008

The problem controlling lateral drift by the wind and the earthquake is very important in high rise buildings. But, outrigger system, generally used for residential tall buildings in Korea, has weak points with the occupancy of special space, the difficult construction and the long duration of works. On the other hand, the damper reduces story drifts of building structure by absorbing vibration energy induced by the dynamic loads and the application of damper systems is relatively simple. Also, the lateral drift control system such as outrigger system may raise the wind vibration problem of serviceability like human comfort and this problem may need another vibration control devices. Accordingly, we analyze the effect of the drift control using various dampers to substitute for outrigger system as the efficient system in residential tall buildings.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.84-90
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• 2017

Explosive bolt is coupled in a variety of guided weapons and space projectiles, to perform the separation function. Thus, the role of the explosive bolt in guided weapons systems is very important, as it can cause failure of the entire system in the case of mission failure. For this reason, the design life prediction for explosive bolt is highly and frequently required recently, but its accurate prediction method has not been presented. In order to apply the existing accelerated aging process, we should know the activation energy and the acceleration factor of the explosive bolt. Since the information required for accelerated aging is not presently secured, it is difficult to predict the design life of explosive. Thus, in the present study, we have evaluated the performance of actual explosive bolts in the condition of natural aging over 10 years in order to present a minimum design life.