• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.217-224
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• 2010

In this paper, we propose a hard handover algorithm for a base station's self-optimization, one of the automatic operational technologies for the 3GPP LTE systems. The proposed algorithm simultaneously considers a mixed target sell selection method for optimal selection and a multiple parameter based active hysteresis method with the received signal strength from adjacent cells and the cell load information of the candidate target cells from information exchanges between eNBs through X2 interface. The active hysteresis method chooses optimal handover hysteresis value considering the costs of the various environmental parameters effect to handover performance. The algorithm works on the optimal target cell and the hysteresis value selections for a base station's automatic operational optimization of the LTE system with the gathered informaton effects to the handover performance. The simulation results show distinguished handover performances in terms of the most important performance indexes of handover, handover failure rate and load balancing.

• Composites Research
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• v.16 no.3
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• pp.1-8
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• 2003

Densification occurs by the inelastic flow of the matrix materials during the consolidation processes at high temperature for MMCs, and the results depend on many process conditions such as applied pressure, temperature and volume fraction of fiber and matrix materials. This is particularly important in titanium matrix composites since material failure may occur by either the applied conditions or microstructural parameters through the processes, and thus a generic model based on micro-mechanical approaches enabling the evolution of density over time to be predicted has been developed. The mode developed is then implemented into FEM so that practical process simulation has been carried out. Further the experimental investigation of the consolidation behavior of SiC/Ti-6Al-4V composites using vacuum hot pressing has been performed, and the results obtained are compared with the model predictions.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.17-23
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• 2016

This study assessed the behavior of rock pillar in tunnel asymmetric diverging area by using a three dimensional numerical analysis. The stability of pillar is very important for the ensure the stability of the tunnel asymmetric diverging area. Based on parameters affecting the behavior of rock pillar, this study evaluated different safety factors according to pillar width, depth and rock conditions. It turned out that as the rock pillar width increases, the change curve of safety factors in accordance with depth and rock conditions shows more of the nonlinear behavior. By the assessment of the minimum safety factor, a safety factor chart on the behavior of rock pillar in tunnel asymmetric diverging area was suggested.

• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.1
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• pp.19-32
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• 2002

This paper examines the effect of the producer-supplier quality contract parameters and the magnitude of the quality related variables on the quality of the final products. Our analysis focuses on the parties' equilibrium behavior In a quality game environment where the supplier should choose among the two production technologies, one requiring high cost but producing high quality Parts and the other requiring low cost but producing low quality parts and where the producer should decide whether to do the inspection of the parts. The game framework is employed to depict the potential conflicts existing between the Producer and the supplier because the Producer can not observe the supplier's choice and each party wants the other to bear the cost of producing high quality products. In our model, we specifically consider the competitive situation where the producer competes with a firm producing the same product. We employ the market share attraction model to Incorporate the competitive situation and completely characterize the equilibrium by using the Nash equilibrium concept for the game solution. Our results show that the equilibrium depends on the contract terms and the magnitude of the quality related variables. Compared to the non-competitive situation, the probability of producer's Inspection and the probability of supplier's choosing the high quality technology increases in a competitive situation. This is true even when the competitor's quality is lower than the producer's lowest. As a result, the quality of the final product increases In a competitive situation. And as the failure cost borne by the supplier increases, the probability of choosing the high quality technology Increases and the probability of inspection decreases. The net effect of this results in the decrease of the final product quality.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.273-288
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• 2015

Purpose: In this study, we apply environmental stress screening (ESS) to battle management system (BMS) of a tank and use the ESS profile based on production process data, guided by MIL-HDBK-781/344/2164. Methods: To optimize ESS Profile of the BMS of a tank, we estimate ESS model parameters (e.g., defect density, screening strength) using primary production failure reporting and corrective action system (FRACAS) data of military supply contract firm. Results: First, we collect the Primary production FRACAS data of military supply contract firm. Second, we compute curve fitting approach to find patent defect density and latent defect density using FRACAS data. Third, we solve the equation of Defect Density(patent defect density + latent defect density)($D_{IN}$) and Screening Strength(SS) Using second step data. As a result of analysis according to the order, we calculate $D_{IN}$(Temperature stress case : 74.02, Vibration stress : 10.252) and : SS(Temperature stress case : 0.4632, Vibration stress : 0.4142) and confirm the Condition II-D based on MIL-HDBK-344. According to Condition II-D, it is necessary to modify existing ESS profile through decreasing the $D_{IN}$ and increasing the SS. Conclusion: Identification of defect causes through ESS approach reduce defect densities for production. It provides feedback to a lessons-learned data base to avoid similar problems on next generation tank BMS.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.589-600
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• 1997

Cold-formed deck sections are used in many composite floor slab applications wherein the steel deck serves not only as the form for the concrete during construction but also as the principal tensile reinforcement for the bottom fiber of the composite slab. This paper provides the results of an experimental study performed for the composite slabs with the new shaped deck plates with the locking ribs, the dove tails, and the powerful embossment, which are the mechanical means to improve positive interlocking effect between the deck and the concrete. A total of 28 specimens are tested to investigate the composite effects between the concrete and metal deck plate. Important parameters in this are the span length, the thickness of the deck plate, support condition, and whether shear studs are placed at each support or not. The test results are summarized for the maximum load and failure behavior for the specimens.

• Korean Journal of Veterinary Research
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• v.50 no.1
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• pp.43-48
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• 2010

Animal disease surveillance system, defined as the continuous investigation of a given population to detect the occurrence of disease or infection for control purposes, has been key roles to assess the health status of an animal population and, more recently, in international trade of animal and animal products with regard to risk assessment. Especially, for a system aiming to determine whether or not a disease is present in a population sensitivity of the system should be maintained high enough not to miss an infected animal. Therefore, when planning the implementation of surveillance system a number of factors that affecting surveillance sensitivity should be taken into account. Of these parameters sample size is of important, and different approaches are used to calculate sample size, usually depending on the objective of surveillance systems. The purpose of this study was to evaluate the sensitivity of the current national serological surveillance programs for four selected bovine diseases assuming a specified sampling plan, to examine factors affecting the probability of detection, and to provide sample sizes required for achieving surveillance goal of detecting at least an infection in a given population. Our results showed that, for example, detecting low level of prevalence (0.2% for bovine tuberculosis) requires selection of all animals per typical Korean cattle farm (n = 17), and thus risk-based target surveillance for high risk groups can be an alternative strategy to increase sensitivity while not increasing overall sampling efforts. The minimum sample size required for detecting at least one positive animal was sharply increased as the disease prevalence is low. More importantly, high reliability of prevalence estimation was expected with increased sampling fraction even when zero-infected animal was identified. The effect of sample size is also discussed in terms of the maximum prevalence when zero-infected animals were identified and on the probability of failure to detect an infection. We suggest that for many serological surveillance systems, diagnostic performance of the testing method, sample size, prevalence, population size, and statistical confidence need to be considered to correctly interpret results of the system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1591-1597
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• 2012

Adherend samples were made from unsaturated polyester and woven and mat glass fibers by the hand layup and vacuum methods. The mechanical properties of the adhesive, composite adherends, and terminal-joint and secondary-joint specimens were determined experimentally. Combinations of the experiment results and the bonding theory were used in this study. The maximum and average shear stresses were calculated based on the maximum tensile force and geometry parameters of the joint specimens. The results of the maximum and average shear stresses were compared and evaluated for six joints. The results showed that the grinding and grind/acetone joint had the highest strength among three types of terminal-joints. Similarly, the mat-mat and mat-woven joints had the highest strength among three types of secondary-joints with the same value. Conversely, no treatment and woven-woven bonding had very low strength. In each case, failure occurred always at two ends and then moved toward the middle area of the overlap length.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.1
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• pp.38-49
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• 1988

This paper presented as follows results of laboratory model tests with various shaped footings on soil bed reinforced with the strips on the base of behaviour of soil structure according to the loads and triaxial test results reinforced with geotextiles. Their parameters studied were the effects on the bearing capacity of a footing of the first layer of reinforcement, horizontal and vertical spacing of layers, number of layers, tensile strength of reinforcement and iclination load to the vertical 1.Depending on the strip arrangement, ultimate bearing capacity values could be more improved than urreinforced soil and the failure of soil was that the soil structure was transfered from the macrospace to microspase and its arrangement, from edge to edge to face to face. 2.The reinforcement was produced the reinforcing effects due to controlling the value of factor of one and permeable reinforcement was never a barrier of drainage condition. 3.Strength ratio was decreased as a linear shape according to increment of saturation degree of soil used even though at the lower strength ratio, the value of M-factor was rot influenced on the strength ratio but impermeable reinforcement decreased the strength of bearing capacity. 4.Ultimate bearing capacity under the plane-strain condition was appeared a little larger than triaxial or the other theoretical formulars and the circular footing more effective. 5.The maximum reinforcing effects were obtained at U I B=o.5, B / B=3 and N=3, when over that limit only acting as a anchor, and same strength of fabric appeared larger reinforcing effects compared to the thinner one. 6.As the LDR increased, more and more BCR occurred and there was appeared a block action below Z / B=O.5, but over the value, decrement of BCR was shown linear relation, and no effects above one. 7.The coefficient of the inclination was shown of minimum at the three layers of fabrics, but the value of H / B related to the ultimate load was decreased as increment of inclination degree, even though over the value of 4.5 there wasn't expected to the reinforcing effects As a consequence of the effects on load inclination, the degree of inclination of 15 per cent was decreased the bearing capacity of 70 per cent but irnproved the effects of 45 per cent through the insertion of geotextile.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.33-42
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• 2007

Accurate predictions of software release times, and estimation of the reliability and availability of a software product require quantification of a critical element of the software testing process : test coverage. This model called Enhanced non-homogeneous poission process(ENHPP). In this paper, exponential coverage and S-shaped model was reviewed, proposes the Kappa coverage model, which maked out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE statistics and Kolmogorov distance, for the sake of efficient model, was employed. From the analysis of mission time, the result of this comparative study shows the excellent performance of Burr coverage model rather than exponential coverage and S-shaped model using NTDS data. This analysis of failure data compared with the Kappa coverage model and the existing model(using arithmetic and Laplace trend tests, bias tests) is presented.