• IEIE Transactions on Smart Processing and Computing
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• v.2 no.4
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• pp.197-202
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• 2013

Large gains in speech intelligibility can be obtained using the SNR-based binary mask approach. This approach retains the time-frequency (T-F) units of the mixture signal, where the target signal is stronger than the interference noise (masker) (e.g., SNR > 0 dB), and removes the T-F units, where the interfering noise is dominant. This paper introduces two alternative binary masks based on the distortion constraints to improve the speech intelligibility. The distortion constraints are induced by a gain function for estimating the short-time spectral amplitude. One binary mask is designed to retain the speech underestimated (T-F) units while removing the speech overestimated (T-F)units. The other binary mask is designed to retain the noise overestimated (T-F) units while removing noise underestimated (T-F) units. Listening tests with oracle binary masks were conducted to assess the potential of the two binary masks in improving the intelligibility. The results suggested that the two binary masks based on distortion constraints can provide large gains in intelligibility when applied to noise-corrupted speech.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.1
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• pp.97-107
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• 1998

This paper is concerned with a parallel system that sustains a time-independent load and consists of n components with exponential lifetimes. It is assumed that the total load is shared by the working components and the failures of components increase higher failure rates in the surviving components according to the relationship between the load and the fialure rates. The power rule model among several load-failure rate relationships is considered. We consider the system efficiency meausre as the expected profit earned by the system per unit time. The high load causes high gain but it also occurs frequent system failures. The expected profit per unit time is used as criterion to evaluate the system efficiency. The goal of system engineer is to determine the optimal load and redundant units maximizing the expected profit per unit time. First, the system reliability function is obtained and the optimization problem of the load-sharing parallel system is considered. Given the redundant units, the existence of the optimal load can be proved analytically and given the load, the optimal redundant units can be solved also analytically. The optimal load and redundant units are obtained simultaneously by numerical computation. Some numerical examples are studied.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.301-312
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• 1997

The purpose of this study was to evaluate the analgesic effect on pulp induced by pulsed Nd : YAG laser according to the power density, irradiated time and the method of application (Non-contact vs contact) in vivo. Experiments were carried out on 90 volunteers who have sound 4 canines. Each canine was grouped by the intensity and the time of irradiation of pulsed Nd : YAG laser was measured. Mean EPT response(units) was measured at 5 min, 30 min, and 60 min after irradiation with various intensity(1.5-3W, 15-30Hz), irradiated time (1.5min, 3min), and application method (Non-contact and contact). The results were as follows: 1. 5 minutes after irradiation, the mean EPT response(units) was increased by 32 % in the non-contact method and by 35% in the contact method of application. Which showed significant difference in mean EPT response(units) compared to not-lased canine in each groups(P<0.05). 2. The mean EPT response(units) with irradiating condition according to the various laser intensity, and the irradiation time stastically did not show significant difference in each groups as time elapsed. 3. There was no significant difference between the non-contact and contact method in the mean EPT response(units). 4. The mean EPT response(units) returned to the baseline value within 30 miuntes. In regard to the above results, the analgesic effect on pulp induced by pulsed Nd : YAG laser resulted a slight increase of pulpal pain threshold, but it was not as high as to replace the role of drug analgesia as whole. This technique can be used for inducing pulpal analgesia as adjunct to other pain control methods and is needed to develop better analgesic effects.

• Journal of Korean Society for Quality Management
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• v.32 no.3
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• pp.62-67
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• 2004

This paper presents and compares two block replacement policies under random use durations. The units are put in service altogether and then idle for some time. The time durations during which units are put in service are random variables. Two block replacement policies, called N-policy and T-policy, are presented. Under N-policy, units are replaced altogether after the Nth use. Under T-policy, units are replaced altogether at the end of the use after cumulative use time T elapses. The failures during use durations are replaced by new ones individually. The cost rate expressions under the policies are derived for exponential use durations. Numerical examples are presented to compare the performances of the two policies.

• Water Engineering Research
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• v.1 no.4
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• pp.279-291
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• 2000

A mathematical model using dynamic programming approach is applied to an optimal unit commitment problem. In this study, the units are treated as stages instead of as state dimension, and the time dimension corresponds to the state dimension instead of stages. A considerable amount of computer time is saved as compared to the normal approach if there are many units in the basin. A case study on the Lower Colorado River Basin System is presented to demonstrate the capabilities of the optimal scheduling of hydropower units.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.79-85
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• 2018

Objective: This study aimed to create a strategic training method to enhance optimal athletic ability using information from 1H to 10H rhythmic units. Method: Top three world class athletes and three national winners of 110-m hurdle finals from the 2010 Daegu International Athletics Competition and 2017 National Athletics Championship, respectively, were selected. To analyze the kinematic variables, Dartfish 9.0 was used for two-dimensional analysis. Results: Regarding the interval time from the start to the finish line, the national athletes took less time during the pure acceleration phase (start to 1H) than the foreign athletes. The horizontal velocity increase was slower after 1H; the national athletes showed a lack of ability to accelerate at the interval phases. Moreover, the hurdle clearance time between phases was longer in the national athletes than in the foreign athletes and lacked consistency. Conclusion: The national athletes lacked the ability to accelerate at the transition, maximum rhythm, rhythm maintenance, and re-acceleration phases and showed a longer hurdle clearance time. If technical improvements and strategic training methods using rhythmic units are applied for hurdling motions, the national athlete's hurdling abilities, performance, and consistency could improve.

• Advances in materials Research
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• v.11 no.1
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• pp.41-57
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• 2022

This paper is focused on delamination analysis of a multilayered inhomogeneous viscoelastic beam subjected to linear creep under constant applied stress. The viscoelastic model that is used to treat the creep consists of consecutively connected units. Each unit consists of one spring and two dashpots. The number of units in the model is arbitrary. The modulus of elasticity of the spring in each unit changes with time. Besides, the modulii of elasticity and the coefficients of viscosity change continuously along the thickness, width and length in each layer since the material is continuously inhomogeneous in each layer of the beam. A time-dependent solution to the strain energy release rate for the delamination is derived. A time-dependent solution to the J-integral is derived too. A parametric analysis of the strain energy release rate is carried-out by applying the solution derived. The influence of various factors such as creep, material inhomogeneity, the change of the modulii of elasticity with time and the number of units in the viscoelastic model on the strain energy release rate are clarified.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.1
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• pp.124-130
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• 2015

In many inventory situations, items for sales are generally stocked in a multiple of variations called stockkeeping units, such as size, color, style, and so on. For better management performance on sales items, proper and effective management is necessary for the stockkeeping units. In dealing with many items and those stockkeeping units, individual inventory analysis for each stockkeeping unit needs large amount of time or cost. Also the individual approach in inventory planning increases the demand variation of an item as the result by combining of demand variations of all stockkeeping units, accordingly the inventory turnover ratio and profitability are dropped down. This research suggests an effective method of systematic control of total stockkeeping units by generating from the total item basis, and shows how to reduce the safety stock and the average inventory with attaining a planned customer fill rate of the item and each stockkeeping units.

• Journal of applied mathematics & informatics
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• v.8 no.1
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• pp.199-212
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• 2001

We consider a k-out-of-n system with repair under T-policy. Life time of each component is exponentially distributed with parameter $\lambda$. Server is called to the system after the elapse of T time units since his departure after completion of repair of all failed units in the previous cycle or until accumulation of n-k failed units, whichever occurs first. Service time is assumed to be exponential with rate ${\mu}$. T is also exponentially distributed with parameter ${\alpha}$. System state probabilities in finite time and long run are derived for (i) cold (ii) warm (iii) hot systems. Several characteristics of these systems are obtained. A control problem is also investigated and numerical illustrations are provided. It is proved that the expected profit to the system is concave in ${\alpha}$ and hence global maximum exists.

• Journal of Radiation Protection and Research
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• v.34 no.1
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• pp.31-36
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• 2009

The purpose of this study is to measure the tube voltage, the tube current/volume, exposure time and exposure dose of diagnostic X-ray unit in each doctor offices, hospitals and general hospitals for evaluating the performance of such device, to learn the method and technology of its measurement and to suggest its importance. Research subjects were total 30 X-ray units and divided into groups of 10 X-ray units each. The tube voltage, the tube current/volume, exposure time and exposure dose were measured using percentage average error, and then reproducibility of exposure dose was measured through calculating coefficient of variation. The results are like followings; The tube voltage correctness examination showed that incongruent devices among total 30 X-ray units were 5 devices (16.7%). The tube current correctness examination showed that incongruent X-ray units were 3 devices (10.0%). The tube current volume correctness examination showed that incongruent X-ray units were 4 devices (13.3%). Finally, according to exposure time correctness examination, incongruent X-ray units were 5 devices (16.7%) and according to reproducibility examination of exposure dose, incongruent X-ray units were 7 devices (23.3%). Above results showed serious problem in performance management based on management regulation of diagnostic X-ray unit; it means that regular checkout and safety management are required, and as doing so, patients will be able to receive good quality of medical service by the reduction of radiation exposure time, image quality administration, unnecessary retake and etc. Therefore, this study suggests that the performance of diagnostic X-ray units should be checked regularly.