• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.152-156
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• 2009

This paper examines the BER performance of the recently proposed half-symbol-rate-carrier (HSRC) offset quadrature phase-shift-keying (OQPSK) receiver for high-speed data communication. A modified demodulation technique using a bit-time period signal integration, the bit-error-rate (BER) performance of the HSRC-OQPSK signal improves more than 4dB compared to that of a demodulation technique using a symbol-time period integration. This paper also examines the BER performance of modified demodulation with various band-limited channels modeled using low-pass filters, and the three different data-rate systems are simulated and compared with the performance of the system using the conventional demodulation technique.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.1
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• pp.25-31
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• 2009

This study presents an analytical model of hydraulic clutch system of a power shift transmission to analyze pressure modulation characteristics. A typical hydraulic clutch system was modeled by using AMESim in which the parameters of major components were measured for simulation. Test apparatus was established using the components of power shift and power shuttle clutches with instrumental equipment. The results of simulation and experiment were so close that the proposed analytical model in this study was validated. However the cylinder model analogized clutch dynamics need to be improved in future study. The effects of parameters of orifice diameter, accumulator stroke and oil temperature on pressure modulation were analyzed respectively. The results of parameter sensitivity analysis show that modulation time and set pressure can be easily adjusted by changing parameter values. It is also found that the hydraulic clutch system used in this study is so susceptible to oil temperature that cooling equipment is necessary.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.161-163
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• 2006

This paper introduce the technology of peak demand reduction using automatic water tank pumping system on the apartment. That systems on the apartments installed water tank can control pumping(electricity) demand. Generally, system peak demand is occurred at the same time on workday and many water pumps consume electric power randomly. At this point, shift of operating time of water pump can reduce peak demand using automatic water tank pumping system. We were operating this system on some apartments for test of effect of peak demand reduction. and we represent result of demand shift. This result suggests that spread of the automatic water pumping system can contribute to reduce system peak demand and reduce system operation cost.

• Journal of Environmental Health Sciences
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• v.37 no.1
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• pp.73-79
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• 2011

The growing interest in nanotechnology has resulted in increasing concern and a number of published environmental and workplace measurements for assessing occupational exposure to engineered nanomaterials. However, the amount of previous exposure data remains limited. Furthermore the data available was collected with extensive variation in terms of exposure measurement strategy, which limits the ability to pool the data in the future. In response, this paper reviewed several pertinent issues related to exposure measurement strategy to suggest a harmonized measurement strategy which would make exposure data more useful in the future, e.g. correlation between exposure metrics, relationship between activity and exposure, task-based or shift-based assessment, background concentration, limitation of personal exposure monitoring and other determinants of exposure/modeling. An improved sampling strategy for nanomaterial exposure assessment should be considered in order to maximize the use of the data from various real time monitoring instruments.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.44-48
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• 2015

Housing price is a key indicator of housing demand. Actual Transaction Price Index of Apartment (ATPIA) released by Korea Appraisal Board is useful to understand the current level of housing price, but it does not forecast future prices. Big data such as the frequency of internet search queries is more accessible and faster than ever. Forecasting future housing demand through big data will be very helpful in housing market. The objective of this study is to develop a forecasting model of ATPIA as a part of forecasting housing demand. For forecasting, a concept of time shift was applied in the model. As a result, the forecasting model with the time shift of 5 months shows the highest coefficient of determination, thus selected as the optimal model. The mean error rate is 2.95% which is a quite promising result.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.423-430
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• 2015

$Cu/ZnO/Al_2O_3$ catalysts for water gas shift (WGS) reaction were synthesized by co-precipitation method with the fixed molar ratio of Cu/Zn/Al precursors as 45/45/10. Copper and zinc precursor were added into sodium carbonate solution for precipitation and aged for 24h. During the aging period, aluminum precursor was added into the aging solution with different time gap from the precipitation starting point: 6h, 12h, and 18h. The resulting catalysts were characterized with SEM, XRD, BET surface measurement, $N_2O$ chemisorption, TPR, and $NH_3$-TPD analysis. The catalytic activity tests were carried out at a GHSV of $27,986h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The catalyst morphology and crystalline structures were not affected by aluminum precursor addition time. The Cu dispersion degree, surface area, and pore diameter depended on the aging time of Cu-Zn precipitate without the presence of $Al_2O_3$ precursor. Also, the interaction between the active substance and $Al_2O_3$ became more stronger as aging duration, with Al precursor presented in the solution, increased. Therefore, it was confirmed that aluminum precursor addition time affected the catalytic characteristics and their catalytic activities.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.47-52
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• 2013

Despite the usefulness of nitrogen isotope tracer experiments in nitrogen cycling studies, there are not such many measurement data mainly due to the difficulties in analytical methods. Although Gardner et al. (1996) developed a relatively simple and accurate method that can measure ammonium isotope using HPLC and used it widely in various N dynamics studies, the technique was not adopted to other laboratories. An HPLC-RTS system using updated HPLC pumps that can perform the same measurements as that of Gardner et al. (1996) was built. The result of standard sample showed linear increase of RTS with the $^{15}N$ proportions. Centroid retention times calculated with Matlab$^{(R)}$ program enhanced the linearity of the response. In a sea water incubation experiment spiked with $^{15}NH_4{^+}$, the uptake and regeneration of ammonium could be separately estimated using the temporal change of $^{15}N/^{14}N$.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.191-202
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• 2004

The batting performance in baseball is a repetitive movement. In order to make the stabilization of posture and the efficient shift of body weight, both the range of stance and stride are important. The previous studies explained that the consistent stride which included the amount of time, stance, and direction were needed. However, the batting performance is frequently changed according to the several speed of ball. Therefore, this study was to analyze the reaction time, the range of stance, the change of stride, and the change of GRF during the batting movement in three kinds of ball speed (120km/h, 130km/h, & 140km/h). Seven elite players are participated in this study. 1. The reaction time of the stride phase was short whereas the time of the swing phase was long according to the increasing ball speed. 2. The range of the stance was wide and the mediolateral direction of the stride was decreased according to the increasing ball speed. 3. In the three kinds of ball speed, the change of body weight was transferred to the center, the rear foot, and the front foot directions. The ball speed of 130km/h showed the high frequency of the suitable batting. At this ball speed, the movement of the body weight was shifted smoothly and the value of the Ground Reaction Force was large enough.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.20.1-20.12
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• 2022

Background: In the manufacturing industry, work-family conflict (WFC) is related to working hour characteristics. Earlier studies on the relationship between working hour characteristics and WFC in the manufacturing industry have been limited to some regions in Korea. No study has addressed the data on a national scale. Thus, this study investigated the impact of weekly working hours, weekend work, and shift work on WFC using national-scale data. Methods: This study was based on the fifth Korean Working Conditions Survey of 5,432 manufacturers. WFC consists of 5 variables; WFC1 "kept worrying about work"; WFC2 "felt too tired after work"; WFC3 "work prevented time for family"; WFC4 "difficult to concentrate on work"; WFC5 "family responsibilities prevented time for work". As WFC refers to the inter-role conflict between the need for paid work and family work, WFC has been measured in two directions, work to family conflict (WTFC: WFC1, 2, 3) and family to work conflict (FTWC: WFC4, 5). With these WFC variables, we conducted multiple logistic analyses to study how working hours, weekend work, and shift work impact WFC. Results: Korean manufacturers' prolonged working hours increased all aspects of WFCs. Odds ratios (ORs) of WFCs based on working hours (reference of under 40 hours) of 41-52, 53-60, over 61 were 1.247, 1.611, 2.279 (WFC1); 1.111, 2.561, 6.442 (WFC2); 1.219, 3.495, 8.327 (WFC3); 1.076, 2.019, 2.656 (WFC4); and 1.166, 1.592, 1.946 (WFC5), respectively. Shiftwork in the WFC2 model showed a significantly higher OR of 1.390. Weekend work 'only on Saturday' had significant ORs with WFC2 (1.323) and WFC3 (1.552). Conclusions: An increase in working hours leads to the spending of less time attending to problems between work and family, causing both WTFC and FTWC to increase. As weekends, evenings, and nighttime are considered to be family-friendly to people, working on weekends and shift-work were highly correlated to WTFC.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.71
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• pp.325-350
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• 2016

As the new competitive environment become more global, technologically oriented and customer driven, as customers continually demand higher quality, faster response, and greater reliability of products and services, the new global market demands a more customer responsive behaviour by companies and firms have responded with innovative products and improved manufacturing processes to manufacture products. Further, the shift from traditional manufacturing and purchasing to JIT manufacturing and purchasing requires customers and suppliers to shift from adversarial relationships to strategic partnerships, and information sharing, so as to attain flexibility, reliability, and speed. SCM practices such as supplier collaboration and information sharing is considered as a key to attaining supplier network responsiveness and enhancing the product innovation and the market access time. The current research investigates the effect of SCM practices on supplier network responsiveness, the product innovation and the market access time of export companies. Thus by providing empirical evidence of the said relationships, this study offers useful guidelines for measuring and improving the supplier network responsiveness of a firm, facilitating further research in the area.