• Journal of Korean Society for Quality Management
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• v.26 no.1
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• pp.74-87
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• 1998

This study considers optimal design of accelerated life tests under constant stress using that the first passage time to cross a critical boundary through amount of accumulated degradation has an inverse Gaussian distribution when the degradation process follows to a Brownian motion with positive drift of log linear function of stress. Optimum plans for Type I censoring are derived by minimizing the asymptotic variance of estimated quantiles at the use stress. Sensitivity analyses are also conducted to see how sensitive the optimality criterion is with respect to the uncertainties involved in the guessed values.

• Current Research on Agriculture and Life Sciences
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• v.5
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• pp.158-167
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• 1987

The purpose of this study is to inquire and analyse the relation between traveltime (Tc) and watetshed physical characteristics surveyed such as river length (L), Lea, river main slope (s), base length of time area diagram, and storage constant (k). The results obtained in this study are as follows. The average widths of watersheds were with the range from 4.6 kilometers to 16.7 kilometers. The shape factors of main stream ranged from 0.08 to 0.37. The average slopes to main 8tream were within the range of 1.7-5.5 meter per kilometer. The relation between the base length and traveltime from S. C. S. method, Rational method, and RZIHA+KRAVEN method were derived $Tc=0.524{\times}1.35^c$ (r=0.98), $Tc=0.628{\times}1.339^c$, (r=0.98), $Tc=0.667{\times}1.342^c$ (r=0.97). The base length of the time-area diagram (c) for the IUH was derived as $c=0.9(\frac{L.L_{ca}}{\sqrt{s}})^{0.35}$ and correlation coefficient was 0.98 which defined a high significance. The storage constant K, derived in this study was $K=8.32+0.0213{\frac{L}{\sqrt{s}}}$ with correlation coefficient (0.96). The relation between storage Constant and conventional formula were figured out $Tc=0.0003{\times}3.323^k$ (r=0.97). $Tc=0.00045{\times}3.268^k$ (r=0.99) and $Tc=0.0004{\times}3.26^k$ (r=0.963). The base length (c) and storage constant (k) of time-Area Diagram were very important parts that determined traveltime for flood events. In the estimate of travel time for predicting flood volume, the formula of $Tc=0.524{\times}1.35^c$ that would be available to apply the Nak - Dong river watershed area and homogeneous watershed characteristics was found.

• Journal of the Korean Society of Safety
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• v.4 no.1
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• pp.25-39
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• 1989

Cyclic temperature creep tests were carried out an AS 7075 alloy specimens were subjected to a constant load and stepwise temperature cycles in which temperature was fluctuated between 30$0^{\circ}C$ and 25$0^{\circ}C$ with three different cycle ratios. The highest frequency of cycling was 1 cycle per 10 hr and the lowest one was 1 cycle per 12 hr. From the creep experimental results with the above conditions the creep strain under cyclic temperature can be predicted easily by introd ucing the equivalent steady temperature because defined by Eq.(16), but the rupture life is 1.1 time than those of constant temperature because of effect of temperature history at tertiary creep range. Besides thlis result, the results of the creep test under cyclic temperature conditions are respectively compayiea with calculated rupture lives using the life fraction law and Eq.(18). The agreement between the obseried rupture times and calculated ones is fairly good. So creep rupture lives can be respectively predicted using life fraction law and Eq.(18).

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.5
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• pp.305-312
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• 2016

Modern embedded systems are typically operated by the rechargeable batteries in our daily life. Since charge of batteries is considered as an time consuming task, there have been extensive efforts to manage the charge time from the perspective of materials, circuits, and systems. Estimation of battery charge time is one of the essential information to design the charge circuitry. A compact macro model for the constant-current and constant-voltage charge protocol was recently introduced, which gives us a quick estimation of charge time with similar shape to the famous Peukert's law for discharge time estimation. The CC-CV charging protocol is widely used for Lithium-based batteries and Lead-acid batteries. In this paper, we characterize the lead-acid battery by measurement to extract the model coefficients, which was not covered by the previous studies. By our proposed model, the key coefficient Kcc results in 1.18-1.31, which is little bit higher than that of Lithium batteries. The accuracy of our model is within the range of ${\pm}10%$ error, which is compatible with the other studies such as Peukert's law.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.32-37
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• 2003

Evaluation of fatigue strength on the spot welded part is very important for strength design of spot welded steel structures. In this paper, we could get the life cycle of the spot welded part using the lethargy coefficient obtained through the quasi-static tensile shear test for the specimen welded by current 10kA. The reliability evaluation of the life cycle is completed by comparing the life cycle calculated under the constant loading rate with the life cycle obtained by dynamic fatigue test. And then the result calculated by the lethargy coefficient is verified through the lift cycle calculated using the dynamic final tensile stress formula under the increased loading speed. This way can make save the time and cost in processing of predicting the life cycle of a structure.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.771-792
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• 2015

In the paper we study dynamic response of a finite, simply supported Timoshenko beam subject to a moving continuously distributed forces. Three problems have been considered. The dynamic response of the Timoshenko beam under a uniform distributed load moving with a constant velocity v has been considered as the first problem. Obtained solutions allow to find the response of the beam under the interval of the finite length a uniformly distributed moving load. Part of the solutions are presented in a closed form instead of an infinite series. As the second problem the steady-state vibrations of the beam under uniformly distributed mass $m_1$ moving with the constant velocity has been considered. The vibrations of the beam caused by the interval of the finite length randomly distributed load moving with constant velocity is considered as the last problem. It is assumed that load process is space-time stationary stochastic process.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.308-311
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• 2001

Most of the battery charger for electric powered forklift truck are controlled by the method of 3-phased constant current and constant voltage. However, these chargers have several disadvantages like a large charger capacity, and a short battery life time. This paper presents a digital type battery charger based on multi-mode control adding a constant power control and several assistant controls in the conventional control. The whole control system is performed by a low cost one-chip micro-controller and completely digitize. So we can get a high precision control and a good reliability.

• Fisheries and Aquatic Sciences
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• v.7 no.1
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• pp.39-45
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• 2004

Six demographic parameters including life span (LS), maturation time (MT), net reproduction rate (Ro), mean generation length (G), innate capacity for increase $(r_m)$ and finite rate of increase $(\gamma)$ were estimated in the rotifer (Brachionus rotundiformis) cultured at three salinities of 5, 20 and 34 PSU and under a constant temperature of $28^{\circ}C$. The maximum life spans at salinities of 5, 20 and 34 PSU were 17, 12 and 13 days, respectively. The shortest maturation time (24 hr) was recorded at 5 PSU, and the rotifer at 20 PSU showed a most delayed maturation (192 hr). The maximum reproduction rate was 42 offspring per female in rotifer cultured at 5 PSU, while the longest generation length (8 days) was observed at 20 PSU. Maximum and minimum values of $r_m$ (1.56 and 0.46 individual per day) and $(\gamma)$ (6.67 and 1.70 individuals per day) were calculated at 5 and 34 PSU, respectively. Salinity also showed strong effect on correlation of the demographic traits examined. ANOVA revealed significant differences (P<0.05) between demographic parameters of the rotifer at the three salinity condition. Considering the higher values of life span, innate capacity and finite rate of increase, and shortest maturation time at 5 PSU, the rotifer we examined had a higher reproductive potential and longer life span at 5 PSU rather than at 20 or 34 PSU.

• BMB Reports
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• v.32 no.3
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• pp.294-298
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• 1999

Myo-inositol monophosphate phosphatase is a key enzyme in the phosphoinositide cell-signaling system. Incubation of myo-inositol monophosphate phosphatase from porcine brain with N-bromosuccinimide (NBS) resulted in a time-dependent loss of enzyme activity. The inactivation followed pseudo-first-order kinetics with the second-order rate constant of $3.8{\times}10^3\;M^{-1}min^{-1}$. The time course of the reaction was significantly affected by the substrate myo-inositol-1-phosphate, which afforded complete protection against the loss of catalytic activity. Spectrophotometric studies indicated that about one oxindole group per molecule of enzyme was formed following complete loss of enzymatic activity. It is suggested that the catalytic function of myo-inositol monophosphate phosphatase is modulated by the binding of NBS to a specific tryptophan residue at or near the substrate binding site of the enzyme.

• Journal of Korean Society for Quality Management
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• v.35 no.2
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• pp.45-52
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• 2007

The danger of self-ignition of single base propellants will increase with time. Therefore, a good prediction of the safe storage time is very important. In order to determine the remaining shelf-life of the propellants, the content of stabilizer is determined. The propellants stored under normal storage conditions about 10 to 18 years were investigated and accelerated aging test was carried out by storing propellant sample at higher temperature. Finally, we analyzed the results by various methods in order to show the best way to predict the realistic shelf-life. The safe storage life of the propellants will be 24 years, at least 15 years. In case of applying Arrhenius's law, using the reaction rate constant at 28$^{\circ}C$ to 30$^{\circ}C$ to predict the shelf-life by accelerated aging test is reasonable for a good prediction.