• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.170-178
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• 2011

In general, a software fault detection phenonenon is described by a software reliability model based on a nonhomogeneous Poisson process(NHPP). In this paper, we propose a software reliability growth model considering the differences of the software environments in both the testing phase and the operational phase. Also, we consider the problem of determining the optimal release time and the optimal warranty period that minimize the total expected software cost which takes account of periodic software maintenance(e.g. patch, update, etc). Finally, we analyze the sensitivity of the optimal release time and warranty period based on the fault data observed in the actual testing process.

• Coupled systems mechanics
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• v.13 no.2
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• pp.153-170
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• 2024

The problem considered in this theoretical paper is the delamination of a multilayered inhomogeneous beam structure that has viscoelastic behaviour under angle of twist, horizontal and vertical displacements which vary smoothly with time according to prescribed laws. The cross-section of the beam is a rectangle. The layers are made of different materials which are smoothly inhomogeneous along the length of the beam. The beam under consideration represents statically undetermined structure since it is clamped in its two ends. The problem of the strain energy release rate is solved. For this purpose, the strain energy stored in the beam structure is analyzed. In order to verify the solution obtained, the strain energy release rate is found also analyzing the time-dependent compliances of the beam under prescribed angle of twist and displacements. A parametric investigation is carried-out by applying the solution obtained. Special attention is paid to the effect of the parameters which control the variation of the angle of twist and the displacements with time on the strain energy release rate.

• The Journal of Internal Korean Medicine
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• v.19 no.2
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• pp.233-248
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• 1998

This study was conducted to investigate effects of Dansambohyultang on serum gastrin, secretin release and CNS in rats and mice. One group of seven rats was intactly in normal condition, the other group of seven rats was respectively heated, starved, and stressfully immobilized. The third group of seven rats was provided with Dansambohyultang before the stress, and the forth one after the stress. And, gastrin concentration and secretin concentration were measured. Mice were studied with regard to convulsion time, total sleep time and analegic effects on cental nerve system. The results were as follows: 1. Gastrin concentration was significantly decreased, and secretin concentration was significantly increased. 2. Analegic effect by acetic acid method was recognizably observed. 3. Effect of total sleep time done by pentobarbital-Na was recognizably observed. 4. Anti-convulsion effects induced by strychnine, picrotoxin and caffeine were recognizable. It is inferred from above results that Dansambohyultang inhibits gastin release, stimulates secretin release and palliate the pain.

• Fire Science and Engineering
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• v.18 no.2
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• pp.67-72
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• 2004

This study describes to assess combustion characteristics of fiber reinforced plastic (FRP) that is used an elements of building or structure in workplace. The combustion characteristics of the fiber reinforced plastic were carried out using by a Cone Calorimeter according to ISO 5660 standard. As the results of this study, the time to ignition and heat release rate of the fiber reinforced plastic was differ with heat flux of irradiance and content of flame retardant agent. The heat release rate of the fiber reinforced plastic was increased with increasing heat flux of irradiance. The flashover propensity of the fiber reinforced plastic using time to ignition and peak heat release rate was examined according to classification method by R.V. Petrella.

• Journal of the Korea Society for Simulation
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• v.8 no.3
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• pp.49-66
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• 1999

Semiconductor wafer fabrication is known to be one of the most complex manufacturing processes due to process intricacy, random yields, product diversity, and rapid changing technologies. In this study we are concerned with the impact of lot release and dispatching policies on the performance of semiconductor wafer fabrication facilities. We consider several semiconductor wafer fabrication environments according to the machine failure types such as no failure, normal MTBF, bottleneck with low MTBF, high randomness, and high MTBF cases. Lot release rules to be considered are Deterministic, Poisson process, WR(Workload Regulation), SA(Starvation Avoidance), and Multi-SA. These rules are combined with several dispatching rules such as FIFO (First In First Out), SRPT (Shortest Remaining Processing Time), and NING/M(smallest Number In Next Queue per Machine). We applied the combined policies to each of semiconductor wafer fabrication environments. These policies are assessed in terms of throughput and flow time. Basically Weins fabrication setup was used to make the simulation models. The simulation parameters were obtained through the preliminary simulation experiments. The key results throughout the simulation experiments is that Multi-SA and SA are the most robust rules, which give mostly good performance for any wafer fabrication environments when used with any dispatching rules. The more important result is that for each of wafer fabrication environments there exist the best and worst choices of lot release and dispatching policies. For example, the Poisson release rule results in the least throughput and largest flow time without regard to failure types and dispatching rules.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1486-1496
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• 2000

The initial flame kernel development and flame propagation in a constant volume combustion chamber is analyzed by the heat release rate and the mass fraction burnt. The combustion pressure is measured with a piezoelectric type pressure sensor. In order to evaluate the effects of ignition system and ignition energy on the flame propagation, four different ignition systems are designed and tested, and the ignition energy is varied by the dwell time. Several different spark plugs are also tested and examined to analysis the effects of electrodes on flame kernel development. The results show that the when the dwell time is increased, and when the spark plug gap is extended, heat release rate and the mass burnt fraction are increased. The materials and shapes of electrodes affect the flame development, because they change the energy transfer efficiency from electrical energy to chemical energy. The diameter of electrodes influences not only the heat release rate but also the mass burnt fraction as well.

• Environmental Mutagens and Carcinogens
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• v.22 no.4
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• pp.229-235
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• 2002

Thimerosal, a widely used preservative, has been well known to induce intracellular calcium mobilization in various cell types. However, the mechanism of its calcium mobilization is not clearly understood yet. For studying the mechanism of thimerosal-mediated calcium release, we have used HL60 cells in calcium-free Lockes solution that has no extracellular calcium. Thimerosal significantly reduced the lag period of initial calcium release whereas it enhanced the rate and magnitude of the calcium release in a dose-dependent manner. At the same time, we found that thimerosal generated superoxide anion by activating NADPH oxidase in dose- and time-dependent manner. Interestingly, the kinetics and the dosedependency of superoxide anion generation were very similar to those of intracellular calcium mobilization. In inhibitors study, the thimerosal-induced superoxide anion generation was significantly suppressed by DMSO as well as superoxide dismutase but not by genistein or EGTA. Surprisingly, the pretreatment with N-Acetyl-$_{L}$-Cysteine blocked almost completely the thimerosal-induced calcium increase, indicating that ROS playa key role in the calcium mobilization. The present results suggest that thimerosal-induced calcium mobilization is possibly mediated by the activation of NADPH oxidase and subsequent ROS generation.n.

• Archives of Pharmacal Research
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• v.29 no.12
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• pp.1179-1186
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• 2006

Cross-linked starch microspheres were prepared using different kinds of cross-linking agents. The influence of several parameters on morphology, size, swelling ratio and drug release rate from these microspheres were evaluated. These parameters included cross-linker type, concentration and the duration of cross-linking reaction. Microspheres cross-linked with glutaraldehyde had smooth surface compared with those prepared with epichlorhydrine or formaldehyde. The particle size increased with increasing the cross-linking time and increasing the drug loading. Swelling ratio of the particles was a function of cross-linker type but not the concentration or time of cross-linking. Drug release from starch microspheres was measured in phosphate buffer and also in phosphate buffer containing a-amylase. Results showed that microspheres cross-linked with epichlorhydrine released all their drug content in the first 30 minutes. However, cross-linking of the starch microspheres with glutaraldehyde or formaldehyde decreased drug release rate. SEM and drug release studies showed that cross-linked starch microspheres were susceptible to the enzymatic degradation under the influence of alpha-amylase. Changing the enzyme concentration from 5000 to 10,000 IU/L, increased drug release rate but higher concentration of enzyme (20,000 IU/L) caused no more acceleration.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1225-1233
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• 1998

An important issue for software developers is to determine when to stop testing the software system and release it to users. Generally the release time is specified by the number of detected faults or the testing time needed to meet the reliability requirement. Software reliability directly depends on the number of remaining or corrected faults. All the detected faults are not always corrected under imperfect debugging environment. We therefore need a new approach to software release policy for imperfect debugging. This paper suggests a software release policy, which guarantees that the reliability requirement has been achieved. The suggested policy is then implemented and illustrated for specific SRGMs.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.685-691
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• 2004

Water quality forecasting with long term flow is important for management and operation of river environment. However, it is difficult to set up and operate a physical model for water quality forecasting due to large uncertainty in the data required for model setting. Therefore, relatively simpler stochastic approaches are adopted for this problem. In this study we try several multivariate time series models such as ARMAX models for the possible substitute for water quality forecasting. Those models are applied to the BOD and COD levels at Noryangin station, Han river, and also evaluated the effect of release from Paldang dam on them. Monthly BOD and COD data from 1985 to 1991 (7 years) are used for model building and another two year data for model testing. As a result of the study, the effect of improvement on water quality is much more effective combining with the water quality improvement of dam release than considering only increment of dam release in the downstream Han river.