• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.633-644
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• 2008

The structural framework design uses high-strength bolts and welding in column splices. However, for the column under high compression, the number of the required high-strength bolts can be excessive and the increase of welding results in difficulty of quality inspection, the transformation of the structural steels, and the increase of erection time. According to the AISC criteria, when columns have bearing plates, or they are finished to bear at splices, there shall be sufficient connections to hold all parts securely in place. The Korean standard sets the maximum 25% of the load as criteria. Using direct contact makes it possible to transfer all compressive force through it. The objective of this study is to examine the generally applied stress path mechanism of welded or bolted columns and to verify the bending moment and compression transfer mechanism of the column splice according to metal touch precision. For this study,22 specimens of various geometric shapes were constructed according to the change in the variables for each column splice type, which includes the splice method, gap width, gap axis, presence or absence of splice material, and connector type. The results show that the application of each splice can be improved through the examination of the stress path mechanism upon metal contact. Moreover, the revision of the relative local code on direct contact needs to be reviewed properly for the economics and efficiency of the splices.

• Journal of Korean Society of Steel Construction
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• v.18 no.1
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• pp.33-45
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• 2006

Cable-stayed bridges are more inherently vulnerable to wind during the erection stages than when they are already being used. Even if a bridge that is already being used is aerodynamically stable, it is prone to having aerodynamic instabilities within the design wind speed during construction. Therefore, when the bridge's designers deliberate on the method they will use in constructing the bridge, they must likewise come up with a suitable plan to ensure the stability of the bridge during its erection (e.g., conducting a wind-tunnel investigation). This paper describes the aeroelastic full-bridge model tests that were conducted to investigate the aerodynamic behavior of the bridge during erection, with emphasis on aerodynamic stability and the mitigation of the buffeting response through temporary stabilization. The aerodynamic performance of a cable -stayed bridge with a main span of 50 m was studied in its completed stage and in two erection stages, corresponding 50% and 90% completion, respectively. In the 50% erection stage tests, a balanced cantilever configuration, with wind cable and temporary support at the tower, was conducted. The system that was determined to be most effective in reducing wind action on the bridge during construction was proposed in the paper, based on the results of the comparative study that was conducted.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.4
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• pp.47-52
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• 2014

Species distribution models have been widely applied in order to assess biodiversity, design reserve, manage habitat and predict climate change. However, SDMs has been used restrictively to the public and policy sectors owing to model uncertainty. Recent studies on ensemble and consensus models have been increased to reduce model uncertainty. This paper was carried out single model and multi model for Corylopsis coreana and compares two models. First, model evaluation was used AUC, kappa and TSS. TSS was the most effective method because it was easy to compare several models and convert binary maps. Second, both single and ensemble model show good performance and RF, Maxent and GBM was evaluated higher, GAM and SRE was evaluated lower relatively. Third, ensemble model tended to overestimate over single model. This problem can be solved by the suitable model selection and weighting through collaboration between field experts and modeler. Finally, we should identify causes and magnitude of model uncertainty and improve data quality and model methods in order to apply special decision-making support system and conservation planning, and when we make policy decisions using SDMs, we should recognize uncertainty and risk.

• The Korean Journal of Emergency Medical Services
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• v.11 no.3
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• pp.31-45
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• 2007

Purpose : The simulation-based training in this research consists of theory and practice. Before the training, target students took a test on the competence of basic life support. Based on the result, they were separated as the subject group and comparison group. The simulation-based training was offered to the subject group and the traditional training was given to the comparison group. As soon as the training was completed, a follow-up study was conducted. Methods : This research aimed to figure out the effect of the simulation-based training on the competence of basic life support of the students Emergency Medical Technology. To this end, the nonequivalent pretest-posttest-quasi-experimental design using a comparison group was conducted. Results : The first hypothesis was that 'The group who took the simulation-based training would show higher points in the knowledge of basic life support than the group who took the traditional training.' Among those who took prior theory education, the subject group showed $69.38{\pm}20.43$ points while the comparison group showed $76.25{\pm}21.33$ points(t = -0.658, p = 0.531). Among those who took prior theory education and training, the subject group showed $82.86{\pm}10.86$ points while the comparison group showed $79.33{\pm}15.45$ points(t = 0.705, p = 0.487). Since there were no significant statistical differences between the two groups, the first hypothesis didn't hold. It showed few differences between the two training methods. The second hypothesis was that 'The group who took the simulation-based training would show higher points in the basic life support skills than the group who took the traditional training.' Among those who took prior theory education, the subject group showed $65.75{\pm}7.66$ points while the comparison group showed $46.88{\pm}13.48$ points(t = -3.442, p = 0.004). Among those who took prior theory education and training, the subject group showed $79.50{\pm}11.40$ points while the comparison group showed $62.13{\pm}11.44$ points(t = 4.091, p = 0.000). Since there were significant statistical differences between the two groups, the second hypothesis held. It showed substantial differences between the two training methods. Conclusion : The group who took the simulation-based training showed more positive effects on the competence of basic life support than those who took the traditional training. Therefore, it is confirmed that the simulation-based training is a useful method to improve clinical work performance of the students Emergency Medical Technology.

• Journal of Energy Engineering
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• v.20 no.1
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• pp.13-20
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• 2011

The high fuel flexibility of Micro Gas Turbine(MGT) has boosted their use in a wide variety of applications. Recently, the demand for biogas generated from the digestion of organic wastes and landfill as a fuel for gas turbines has increased. We researched the influence of firing landfill gas(LFG) on the performance and operating characteristics of a micro gas turbine combined heat and power system. $CH_4$ and $CO_2$ simultaneous recovery process has been developed for field plant scale to provide an isothermal, low operating cost method for carrying out the contaminants removal in Land Fill Gas(LFG) by liquid phase catalyst for introduce into the green house for the purpose of $CO_2$ rich cultivation of the plants. Methane purification and carbon dioxide stripping by muti panel autocirculation bubble lift column reactor utilizing Fe-EDTA was conducted for evaluate optimum conditions for land fill gas. Based on inflow rate of LFG as 0.207 $m^3$/min, 5.5 kg/$cm^2$, we designed reactor system for 70% $CH_4$ and 27% $CO_2$ gas introduce into MGT system with $H_2S$ 99% removal efficiency. A green house designed for four different carbon dioxide concentration from ambient air to 1500 ppm by utilizing the exhaust gas and hot water from MGT system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.84-93
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• 2006

Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines between OLT and ONUs. It has a point-to-multipoint and multipoint-to-point architecture in downstream and upstream direction, respectively. Therefore, downstream packets are broadcast from an OLT toward all ONUs sithout collision. On the other hand, since alt ONUs share a common channel, the collision may be occurred for the upstream transmission. Therefore, earlier efforts on Ethernet-PON have been concentrated on an upstream MAC protocol to avoid collision. But it is needed to control downstream traffic in practical access network, where the network provider limits available bandwidth according to the number of users. In this paper, we propose a traffic control scheme for supporting the fairness of the downstream bandwidth. The objective of this algorithm is to guarantee the fairness of ONUs while maintaining good performance. In order to do this, we define the service probability that considers the past traffic information for downstream, the number of tokens and the relative size of negotiated bandwidth. We develop the simulation model for Ethernet-PON to evaluate the rate-limiting algorithm by using AWESIM. Some results are evaluated and analyzed in terms of defined fairness factor, delay and dropping rate under various scenario.

• Journal of IKEEE
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• v.13 no.4
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• pp.63-68
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• 2009

The power management integrated circuit(PMIC) for CCD image sensor is presented in this study. A CCD image sensor is very sensitive against temperature. The temperature, that is heat, is generally generated by the PMIC with low efficiency. Since the generated heat influences performance of CCD image sensor, it should be minimized by using a PMIC which has a high efficiency. In order to develop the PMIC with high efficiency, the input stage is designed with synchronous type step down DC-DC converter. The operating range of the converter is from 5V to 15V and the converter is controlled using PWM method. The PWM control circuit consists of a saw-tooth generator, a band-gap reference circuit, an error amplifier and a comparator circuit. The saw-tooth generator is designed with 1.2MHz oscillation frequency. The comparator is designed with the two stages OP Amp. And the error amplifier has 40dB DC gain and $77^{\circ}$ phase margin. The output of the step down converter is connected to input stage of the charge pump. The output of the charge pump is connected to input of the LDO which is the output stage of the PMIC. Finally, the PMIC, based on the PWM control circuit and the charge pump and the LDO, has output voltage of 15V, -7.5V, 3.3V and 5V. The PMIC is designed with a 0.35um process.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.21-35
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• 2016

This study is to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for multi-purpose dams and multi-function weirs operation in Namhan river basin ($12,577km^2$) of South Korea. The SWAT was calibrated (2005 ~ 2009) and validated (2010 ~ 2014) considering of 4 multi-purpose dams and 3 multi-function weirs using daily observed dam inflow and storage, evapotranspiration, soil moisture, and groundwater level data. Firstly, the dam inflow was calibrated by the five steps; (step 1) the physical rate between total runoff and evapotranspiration was controlled by ESCO, (step 2) the peak runoff was calibrated by CN, OV_N, and CH_N, (step 3) the baseflow was calibrated by GW_DELAY, (step 4) the recession curve of baseflow was calibrated by ALPHA_BF, (step 5) the flux between lateral flow and return flow was controlled by SOL_AWC and SOL_K, and (step 6) the flux between reevaporation and return flow was controlled by REVAPMN and GW_REVAP. Secondly, for the storage water level calibration, the SWAT emergency and principle spillway were applied for water level from design flood level to restricted water level for dam and from maximum to management water level for weir respectively. Finally, the parameters for evapotranspiration (ESCO), soil water (SOL_AWC) and groundwater level fluctuation (GWQMN, ALPHA_BF) were repeatedly adjusted by trial error method. For the dam inflow, the determination coefficient $R^2$ was above 0.80. The average Nash-Sutcliffe efficiency (NSE) was from 0.59 to 0.88 and the RMSE was from 3.3 mm/day to 8.6 mm/day respectively. For the water balance performance, the PBIAS was between 9.4 and 21.4 %. For the dam storage volume, the $R^2$ was above 0.63 and the PBIAS was between 6.3 and 13.5 % respectively. The average $R^2$ for evapotranspiration and soil moisture at CM (Cheongmicheon) site was 0.72 and 0.78, and the average $R^2$ for groundwater level was 0.59 and 0.60 at 2 YP (Yangpyeong) sites.

• Fire Science and Engineering
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• v.31 no.1
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• pp.10-17
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• 2017

Securing fire safety using only fire-fighting facilities is difficult because causes of modern fire vary, such as architectural structures and building use patterns. In order for fire safety to be guaranteed by enacting and revising fire regulations reflecting the fire hazard characteristics and user's characteristics, the introduction of fire influence evaluation (fire risk assessment) system needs to be considered in a timely manner to be adopted but unfortunately two attempts before have failed. In this study, a fire case of urban lifestyle housing was surveyed to introduce a fire influence evaluation system and a field survey on the actual condition of the 414 urban lifestyle housing buildings and fire & evacuation simulation results of one representative building in Suyoung-gu and Nam-gu District of Busan Metropolitan City were analyzed. The necessity, procedures and implementation method of fire influence evaluation system were questioned and tested by the professional fire experts, fire officers and firefighters and architects. On the basis of these facts, introduction of (fire influence evaluation system) should be absolutely adopted and the fire department and fire regulation are eligible to implement the system. Therefore, fire regulation needs to be enacted or revised in accordance with the new fire environment and fire safety system that needs to be built up. Accordingly, aggressive promotion through public hearings on the necessity of fire impact assessments, consensus among departments and fostering experts to carry out fire influence evaluation system will be the core.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.671-680
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• 2005

The CFL linearisation chip which is one of key devices in ultra-narrowband mobile radio transmitter using CQPSK digital modulation method is designed and implemented with $0.35{\mu}m$ CMOS technology. The reduced size and low cost of transmitter are available by the use of direct-conversion and CFL ASIC chip, which improve the power effi챠ency and linearity of transmitting path. In addition, low power operation is possible through CMOS technology The performance test results of transmitter show -25 dBc improvement of IMD level at the 3 kHz frequency offset and then satisfy FCC 47 CFR 90.210 E emission mask in the operation of CFL ASIC chip. At that time, the transmitting power is about PEP(Peak-to-Envelope Power) 5 W. The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.