• Korean Journal of Optics and Photonics
• /
• v.14 no.5
• /
• pp.565-569
• /
• 2003

We designed a transflective-type LCD using a twisted VA mode. Generally, a VA mode had a blue shift due to intrinsic properties. We solved this problem using spectroscopic compensation film. We used the front scattering film and negative C-plate to improve characteristics of the viewing angle and contrast ratio. As a result, we found that proposed the transflective-type TVA mode had a contrast ratio of about 80:1, a response time of 22 ms, and a reflectance of 25% in comparison with the standard MgO reflector.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.482-485
• /
• 1996

We design a homing guidance law based on the proportional navigation for the fast-rolling, single-axis control missiles and analyse the misdistance of the designed guidance system. The guidance law includes a compensation scheme which compensates for the phase-shift between the commanded and achieved acceleration which is peculiar to the fast rolling airframe with single-axis control. In the error analysis of the guidance system, we calculate the misdistance with respect to the target maneuver on the 3-dimensional space via direct simulations. Also, we conduct adjoint simulation on the 2-dimensional plane in case that phase-shift is perfectly compensated. Finally we approximate the linear time-varying dynamics of the missile with autopilot to a linear time-invarient system, and as a result we can find the misdistance as a closed-form.

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

• Journal of information and communication convergence engineering
• /
• v.7 no.2
• /
• pp.152-156
• /
• 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 Korean Society of Automotive Engineers
• /
• v.12 no.5
• /
• pp.180-186
• /
• 2004

The simulator of a vehicle equipped with mechanical transmission and hydraulic accumulator type-braking energy regeneration system is developed using a PC. The simulator receives the shift lever position, the accelerator pedal angle and the brake pedal angle generated by the operator using the keyboard, updates the state variables of the energy regeneration system responding to the input signals, and draws the moving pictures of the accumulator piston and pump/motor plate angle every drawing time on the PC monitor. Also, the operator can observe the shift lever position, the accel pedal angle, brake pedal angle, pressures of accumulators, vehicle speed, hydraulic torque, engine torque and air brake torque representing the operation of braking energy regeneration system through the PC monitor every drawing time. The simulator can be a very useful tool to design and improve the braking energy regeneration system.

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

• Journal of the Korea Safety Management & Science
• /
• v.9 no.2
• /
• pp.215-233
• /
• 2007

Even though the ad hoc Shewhart methods remain controversial due to various mathematical flaws, there is little disagreement among researchers and practitioners when a set of process data has a skewness distribution. In the context and language of process control, the error related to the process data shows that time to signal increases when a control parameter shifts to a skewness direction. In real-world industrial settings, however, quality practitioners often need to consider a skewness distribution. To address this situation, we developed an enhanced design method to utilize advantages of the traditional attribute control chart and to overcome its associated shortcomings. The proposed design method minimizes bias, i.e., an average time to signal for the shift of process from the target value (ATS) curve, as well as it applies a variable sampling interval (VSI) method to an attribute control chart for detecting a process shift efficiently. The results of the factorial experiment obtained by various parameter circumstances show that the VSI c control chart using nearly unbiased ATS design provides the smallest decreasing rate in ATS among other charts for all experimental cases.

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

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

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