• Proceedings of the Korean Society for Quality Management Conference
• /
• 1998.11a
• /
• pp.544-555
• /
• 1998

Although the bimodal mixed weibull distribution is used to developing burn-in model widely, the failure times for a component or a system is often truncated at some time, T, due to the obsolescence in the electronics industry. In this paper, we will determine minimum total cost and burn-in time by using the bimodal mixed weibull distribution and the truncated bimodal mixed weibull distribution under the free warranty policy. The results of this study are summarized as follows. First, when products or system is not repairable, the width of the change of burn-in time can be larger by ${\beta}_1,\;{\beta}_2$ Second, if burn-in time become longer, it will be impossible to consider the bum-in in a long time, and in this case, the burn-in time should be shorten by the acceleration burn-in. Third, in case that opportunity loss cost or repair cost is exceed the warranty cost, or the total cost of considering burn-in is larger than that of not considering burn-in, it is not existed burn-in time which makes total cost to minimize. Forth, the shorter life-cycle of product, the more burn-in times will be decreased and the cost in considering burn-in will be increased

• Proceedings of the Safety Management and Science Conference
• /
• 1999.11a
• /
• pp.147-155
• /
• 1999

This paper discusses an optimal burn-in procedure to minimize total costs based on the assumption that the failure rate pattern follows a bimodal mixed Weibull distribution. The procedure will consider warranty period as a factor of the total expected burn-in cost. A cost model is formulated to find the optimal burn-in time that minimizes the expected burn-in cost. Conditional reliability for warranty period will be discussed. An illustrative example is included to show how to use the cost model in practice.

• Journal of the Korean Data and Information Science Society
• /
• v.14 no.4
• /
• pp.997-1005
• /
• 2003

In this paper, the problem of determining optimal burn-in time is considered under a general failure model. There are two types of failure in the general failure model. One is Type I failure (minor failure) which can be removed by a minimal repair and the other is Type II failure (catastrophic failure) which can be removed only by a complete repair. In this model, when the unit fails at its age t, Type I failure occurs with probability 1 - p(t) and Type II failure occurs with probability p(t), $0{\leq}p(t)\leq1$. Under the model, the properties of optimal burn-in time maximizing mean time to the catastrophic failure during field operation are obtained. The obtained results are also applied to some illustrative examples.

• Archives of Plastic Surgery
• /
• v.35 no.4
• /
• pp.373-378
• /
• 2008

Purpose: In full thickness burn, the depth of burn is known to increase until around 1-3 days after the burn. However, no study on how the depth increase during the first 24 hours has been conducted. Therefore, the authors investigated how the depth of burn changes within the first 24 hours after the burn by using the standardized burn model. Methods: A total of four experiments on pigs were carried out for this study. Experiment 1 was performed to examine how temperature affects the depth of burn. The digitally controlled aluminum thermal block was set at different temperatures-80, 90 and 100 degrees in Celsius, respectively. Then the pig was exposed to the block for 15 seconds each time. The time exposed to heat was set as a variable for the Experiment 2. The temperature was maintained at 80 degrees Celsius, and the pig was contacted with the thermal block for 5, 10 and 20 seconds, respectively. The biopsy of the tissues were performed in one hour, 6 hours, 24 hours, and 7 days after the burn. After hematoxylin and eosin staining a percentage of the depth from a basement membrane of epidermis to the deepest tissue damaged by the burn against total dermal thickness was measured. Results: In Experiment 1, the depth of burn increased considerably as time passed by. At all three temperatures, differences in depths measured in 6 and 24 hours, and in 1 hour and 7 days were both significant. In addition, the depth deepened as the temperature went higher. In the case of Experiment 2, the depth of burn also increased significantly as time passed by. At all three times, differences in depth measured in 6 and 24 hours, and in 1 hour and 7 days were also significant. Moreover, the depth extended with longer contact time when it was compared according to the time. Conclusion: Full thickness burn progressed rapidly from 6 to 24 hours after the burn and the depth of burn was almost decided within the first 24 hours after the burn. On the other hand, partial thickness burn also advanced from 6 to 24 hours after the burn but the depth deepened at slower level.

• Aerospace Engineering and Technology
• /
• v.13 no.1
• /
• pp.96-107
• /
• 2014

Korea Aerospace Research Institute has a plan to launch experimental lunar orbiter in 2017, and lunar orbiter and lander in 2020. In the mission planning phase, LOI(Lunar Orbit Insertion) maneuver strategy should be designed using finite burn model because on-board propulsion system of lunar orbiter in finite burn type. LOI maneuver plan and amount of required ${\Delta}V$ using finite burn model depend on the spacecraft attitude at burn, a type of propellant, thrust level and burn timing. This paper describes the LOI maneuver of lunar orbiter of foreign space agency and then comes up with the LOI maneuver plan of Korean lunar orbiter. Adequate thrust level and burn duration of Korean lunar orbiter also present by performing simulation.

• Journal of Pharmaceutical Investigation
• /
• v.35 no.4
• /
• pp.255-263
• /
• 2005

Research was undertaken to compare the pharmacological activity of Lithospermi radix (LR) reported as an oriental medicine for classical uses. LR contains naphthoquinone pigments : shikonin, acetylshikonin, isobutylshikonin, etc. LR is used for the treatment of excision wound, burn, eczema, blister, scarlatina and septicemia as antifebrile, antidotic and antiphlogistic. Gardeniae fructus (GF) has been used for the treatment to jaundice, hepatic disease, anti-inflammatory and analgesic effects, and it contains crocin, geniposide and its derivatives. The therapeutic effects of burn and excision wound healing from LR & GF hydrogel with $Nano-ATP^{\circledR}$ (GLN) were investigated. To evaluate the therapeutic value of various hydrogels, thermal burn model and excision wound mouse model were used. The burn and wound reduction rate and therapeutic period were measured to calculate the healing extent after 5 experiments. The 2nd degree burn was prepared on hairless mouse back skin and dressing with collagen. The burn and wound reduction rate of GLN hydrogel treated group decreased more rapidly than that of other gel group in animal model. Furthermore therapeutic periods of GLN hydrogel treated group was shorter than that of other gel group. In anti-inflammatory test, GLN hydrogel treated group decreased edema rapidly than that of other gel group. These results suggest that the GLN hydrogel treatment has an therapeutic effect on burn and excision wound healing.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.24 no.62
• /
• pp.1-10
• /
• 2001

The electronics industry is fast growing segment of manufacturing and service industries. It is important that the manufacturer develops a product with adequate life cycle, high quality, and low failure rate in the specified time period. Environmental Stress Screening(ESS) and burn-in are widely used in the electronic industry to assist in the elimination of early failure. In this research, we construct optimal cost model of combined ESS and burn-in under various warranty policy and establish optimal testing times for given environments. Also we conduct sensitivity analysis on various parameter. The results of this study are summarized as follows. Comparing free warranty policy to rebate warranty policy, optimal ESS time is longer under free warranty policy, and optimal burn-in time is longer under rebate warranty policy. Free warranty policy higher than rebate warranty policy in total cost.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.35 no.4
• /
• pp.1-9
• /
• 2012

Decisions on reliability screening rules and burn-in policies are determined based on the estimated reliability. The variability in a semiconductor manufacturing process does not only causes quality problems but it also makes reliability estimation more complicated. This study investigates the nonuniformity characteristics of integrated circuit reliability according to defect density distribution within a wafer and between wafers then develops optimal burn-in policy based on the estimated reliability. New reliability estimation model based on yield information is developed using a spatial stochastic process. Spatial defect density variation is reflected in the reliability estimation, and the defect densities of each die location are considered as input variables of the burn-in optimization. Reliability screening and optimal burn-in policy subject to the burn-in cost minimization is examined, and numerical experiments are conducted.

• Physical Therapy Rehabilitation Science
• /
• v.6 no.4
• /
• pp.170-175
• /
• 2017

Objective: The anti-inflammatory effects of low-level laser in burn wound model in rats were investigated. Design: Randomized controlled trial. Methods: The rats were assigned to three experimental groups. Group I received second-degree burn wounds; Group II received dressing film and low-level laser ($1.2J/cm^2$) treatment after a burn wound; Group III received dressing film and low-level laser ($2.3J/cm^2$) treatment after a burn wound. After inducing a deep second-degree burn wound, the wound was observed every day and the burn area diameter and retraction quantification at 1, 7, and 14 days were evaluated. Low-level laser was investigated on hematological parameters after 14 days. Effects of low-level laser on the inflammatory cytokines (tumor necrosis $factor-{\alpha}$ [$TNF-{\alpha}$] and interleukin-6 [IL-6]) concentrations in the serum were evaluated using immunosorbent assay kits. Results: Group III showed a significant difference in wound size on days 7 and 14 compared to Group I (p<0.05). Group II showed a significant difference in wound size on day 14 compared to Group I (p<0.05). For wound contraction percentage, both laser therapy treatment groups showed a significant difference compared with Group I (p<0.05). There was also a significant difference in wound contraction percentage in Group III compared to Group II (p<0.05). Compared with the model control group, decreased $TNF-{\alpha}$ and IL-6 levels in the serum was observed at 14 days after burn wound induction. Conclusions: The results of this study suggest that low-level laser therapy can assist in burn wound healing, which might be associated with decreased concentrations of $TNF-{\alpha}$ and IL-6 related proinflammatory cytokines.

• Journal of Radiation Protection and Research
• /
• v.41 no.2
• /
• pp.155-159
• /
• 2016

Background: Nuclear reactors produce a great number of antielectron neutrinos mainly from beta-decay chains of fission products. Such neutrinos have energies mostly in MeV range. We are interested in neutrinos in a region of keV, since they may take part in special weak interactions. We calculate reactor antineutrino spectra especially in the low energy region. In this work we present neutrino spectrum from a typical pressurized water reactor (PWR) reactor core. Materials and Methods: To calculate neutrino spectra, we need information about all generated nuclides that emit neutrinos. They are mainly fission fragments, reaction products and trans-uranium nuclides that undergo negative beta decay. Information in relation to trans-uranium nuclide compositions and its evolution in time (burn-up process) were provided by a reactor code MVP-BURN. We used typical PWR parameter input for MVP-BURN code and assumed the reactor to be operated continuously for 1 year (12 months) in a steady thermal power (3.4 GWth). The PWR has three fuel compositions of 2.0, 3.5 and 4.1 wt% $^{235}U$ contents. For preliminary calculation we adopted a standard burn-up chain model provided by MVP-BURN. The chain model treated 21 heavy nuclides and 50 fission products. The MVB-BURN code utilized JENDL 3.3 as nuclear data library. Results and Discussion: We confirm that the antielectron neutrino flux in the low energy region increases with burn-up of nuclear fuel. The antielectron-neutrino spectrum in low energy region is influenced by beta emitter nuclides with low Q value in beta decay (e.g. $^{241}Pu$) which is influenced by burp-up level: Low energy antielectron-neutrino spectra or emission rates increase when beta emitters with low Q value in beta decay accumulate Conclusion: Our result shows the flux of low energy reactor neutrinos increases with burn-up of nuclear fuel.