• Korean Journal of Occupational Health Nursing
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• v.24 no.4
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• pp.372-380
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• 2015

Purpose: The purpose of this study was to seek ways to improve the quality of life of workers by separating workers into the low fatigue group and the severe fatigue group depending on the level of fatigue level, and analyzing and understanding the difference between quality of life and job stress according to the fatigue level. Methods: For the 'Development of Mibyeong management system which was a consumer-directed health care service', the data of job stress, fatigue and quality of life was collected from 115 workers who visited the oriental hospitals located in J city and C city from Jul, 2012 to Dec, 2012. Results: The severe fatigue group showed significantly higher job stress than the low fatigue group in physical environment (p=.004), job demand (p<.001), interpersonal conflict (p=.012), lack of reward (p=.062). The severe fatigue group showed lower degrees both in physical component summary (PCS) (p<.001) and mental component summary (MCS) (p<.001) measured by SF-12 and the quality of life (p<.001) measured by EQ5D than the lower fatigue group. A relatively strong negative correlation was found in the item of mental component summary (MCS) measured by SF-12. Conclusion: Considering our results that high fatigue level show negative impact on quality of life and job stress, we suggest to provide a variety of health promotion strategies to improve the quality of life through the prevention and relief of fatigue for workers.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.10-19
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• 2012

In this paper, we propose an Adaptive Modulation and Coding (AMC) scheme using relay protocols generally known as Relay Node (RN). The AMC scheme is used for improving the throughput and a reliability of a communication system, because of the nature of different modulation and coding schemes. We analyze the performance of relay protocols with the AMC scheme and observed that relay protocols with the AMC scheme is capable of providing better average throughput at a lower Signal to Noise Ratio (SNR) level as compared to the conventional scheme with no AMC. We perform Monte Carlo simulations with Long Term Evolution-Advanced (LTE-A) parameters to prove the performance comparison of adaptive Modulation and Coding Scheme (MCS) relay protocols with the non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the Amplify-and-Forward (AF), Decode-and-Forward (DF) and DeModulate-and-Forward (DMF), the DMF protocol performs best at a lower SNR value and also provides better average throughput.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.652-657
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• 2003

In this paper, Adaptive Modulation and Coding (AMC) is combined with Multiple Input Multiple Output (MIMO) multiplexing to improve the throughput performance of AMC. In addition, a system that adopts Selection Transmit Diversity (STD) in the AMC-MIMO multiplexing system is proposed. The received SNR is improved by adopting STD techniques. And it increases probability of selecting MCS (Modulation and Coding Scheme) level that supports higher data rate. This leads to an increased throughput of the AMC-MIMO system. STD in our simulation selects 2 transmission antennas from 4 antennas and AMC-MIMO multiplexing process operates with the selected antennas. The computer simulation is performed in flat Rayleigh fading channel. The results show that the proposed system achieves a gain of 1Mbps over the AMC-MIMO multiplexing system with the same number of antennas at 15dB SNR.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.11
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• pp.1123-1131
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• 2008

In this study, measurement uncertainty of instrumental neutron activation analysis was evaluated for ambient As concentration in PM2.5. Expanded uncertainties of the measurements were calculated by applying both ISO-GUM approximation and Monte Carlo Simulation(MCS). The estimate of As concentration on a specific day by the Monte Carlo Simulation differed from that of ISO-GUM approximation by less than 4%. Relative expanded uncertainties of As concentrations from a total number of 60 PM2.5 samples were also estimated to be more or less than 10% with 95% confidence level using the Monte Carlo Simulation. Sensitivity test of the measurement uncertainties showed that $\gamma$-ray counting error(62.3%), efficiency(18.5%), air volume(12.3%), neutron flux(2.3%), and absolute gamma-intensity(1.8%) are major factors of uncertainty variations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.8-12
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• 2008

In this paper, we proposes a D-STTD(Double-Space Time Transmit Diversity) communication system with AMC scheme and analyzes its performance using simulation experiments. The AMC scheme selects an optimal channel coding rate and modulation scheme based on the channel response data for signal transmission, creating a balance between error rate and throughput to improve the overall system throughput and transmission quality. The D-STTD scheme complements the conventional STTD(Space Time Transmit Diversity) scheme, yielding about twice the throughput. The simulation results show that the probability of selecting a high MCS(Modulation and Coding Scheme) level increased as the SNR(Signal to Noise Ratio) improved. Furthermore, the D-STTD communication system with AMC scheme provided a more uniform throughput distribution throughout the entire SNR range compared to its counterpart which did not apply AMC scheme. Also, the maximum throughput of the D-STTD communication system with AMC scheme was twice that of a conventional AMC communication system or a STTD communication system with AMC scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10A
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• pp.839-846
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• 2011

Link Adaptation should select the best modulation and coding scheme (MCS) which gives the highest throughput as channel conditions vary. Several link adaptation algorithms for wireless local area network (WLAN) have been proposed but for the future WLAN systems such as 802.11n system, these algorithms do not guarantee the best performance. In this paper, we propose a new link adaptation algorithm in which an MCS level is chosen by the received SNR plus the offset value obtained from the transmission results. The performance of proposed algorithm is simulated by an IEEE 802.11n system. From the analysis, we conclude the proposed algorithm performs better than the well-known link adaptation algorithms such as auto rate fallback and general SNR-based techniques. Particularly, the proposed algorithm improves throughput when the packet error ratio (PER) is constrained for fast fading channels.

• Journal of the Korean Wood Science and Technology
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• v.30 no.4
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• pp.41-50
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• 2002

Small clear specimens of Quercus acutissima Carr. and Larix caempferi Carr. were used to measure shrinkage and thermal conductivity for the reasonable and effective use. All samples were conditioned to 18, 12, 5% moisture contents in a humidity chamber of 86, 66, 20% relative humidity(RH), respectively and room temperature(23℃) All specimens were conducted on the shrinkage and thermal conductivity test at each MCs. These processes(cycle) were repeated three times. The radial and tangential shrinkages of Quercus acutissima Carr. and Larix caempferi Carr. decreased at each level of MCs, with the increasing cycles. The radial and tangential shrinkages increased as the specific gravity(on oven-dry weight and volume basis) increased. Thermal conductivities of the radial and tangential direction of Quercus acutissima Carr. and Larix caempferi Carr. increased at each levels of MCs, with increasing cycles. Good correlations were obtained between shrinkages and thermal conductivities of radial and tangential direction, and specific gravity (on oven-dry weight and oven-dry volume basis) and MC.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.157-165
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• 2008

Level II AFDA and Level III MCS reliability models are applied to analyze the stability of armor units on trading and coastal harbors in Korea. Hudson's formula and Van der Meer's formula are used in this reliability analysis. Also, probability density functions of reliability index and probability of failure are derived by the additional analysis. In addition, the partial safety factors of all harbors related to armor units can be straightforwardly evaluated by the inverse-reliability method. The upper and lower limits and average level of partial safety factors can be statistically investigated with the results of all cases applied in this paper. Therefore, it may be possible to design armor units of new breakwaters including the uncertainty of random variable and target level by using the present results.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2124-2135
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• 2006

In this paper, the reliability estimation of pipelines is performed by employing the probabilistic method, which accounts for the uncertainties in the load and resistance parameters of the limit state function. The FORM (first order reliability method) and the SORM (second order reliability method) are carried out to estimate the failure probability of pipeline utilizing the FAD (failure assessment diagram). And the reliability of pipeline is assessed by using this failure probability and analyzed in accordance with a target safety level. Furthermore, the MCS (Monte Carlo Simulation) is used to verify the results of the FORM and the SORM. It is noted that the failure probability increases with the increase of dent depth, gouge depth, operating pressure, outside radius, and the decrease of wall thickness. It is found that the FORM utilizing the FAD is a useful and is an efficient method to estimate the failure probability in the reliability assessment of a pipeline. Furthermore, the pipeline safety assessment technique with the deterministic procedure utilizing the FAD only is turned out more conservative than those obtained by using the probability theory together with the FAD. The probabilistic method such as the FORM, the SORM and the MCS can be used by most plant designers regarding the operating condition and design parameters.

• Journal of the Korea Safety Management & Science
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• v.2 no.4
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• pp.91-102
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• 2000

Nowadays, every kind of system is changed so complex and enormous, it is necessary to assure system reliability, product liability and safety. Fault tree analysis(FTA) is a reliability/safety design analysis technique which starts from consideration of system failure effect, referred to as “top event”, and proceeds by determining how these can be caused by single or combined lower level failures or events. So in fault tree analysis, it is important to find the combination of events which affect system failure. Minimal cut sets(MCS) and minimal path sets(MPS) are used in this process. FTA-I computer program is developed which calculates MCS and MPS in terms of Gw-Basic computer language considering Fussell's algorithm. FTA-II computer program which analyzes importance and function cost of VE consists. of five programs as follows : (l) Structural importance of basic event, (2) Structural probability importance of basic event, (3) Structural criticality importance of basic event, (4) Cost-Failure importance of basic event, (5) VE function cost analysis for importance of basic event. In this study, a method of initiation such as failure, function and cost in FTA is suggested, and especially the priority rank which is calculated by computer-aided decision analysis program developed in this study can be used in decision making determining the most important basic event under various conditions. Also the priority rank can be available for the case which selects system component in FMEA analysis.