• Journal of Korean Society of Water and Wastewater
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• v.28 no.5
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• pp.561-571
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• 2014

The paper is to estimate willingness-to-pay (WTP) for tap water quality improvement in Busan, using parametric approach in contingent valuation method(CVM). For parametric approach linear logit model and log logit model are employed in double-bounded dichotomous choice format of CVM. For the reliability and the validity of contingent valuation method a survey was conducted for 665 respondents, who were sampled by stratified random sampling method, by personal interview method. The result of mean WTP for the tap water quality improvement in Busan was estimated to be 3,687 won and 3,660 won per month per household, while median WTP being 1,884 won and 1,892 won per month per household, respectively by linear logit model and log logit model. Provided that our sample is broadly representative of the Busan's population, an estimate of the annual aggregated benefit of residential water improvement for all Busan households is approximately 29.7 billion won to 29.8 billion won based on median WTP.

• Journal of the Korean Institute of Navigation
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• v.5 no.2
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• pp.1-39
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• 1981

A doppler log is the typical device which can measure the ship's speed over the ground directly, by means of doppler effect of the underwater ultrasonic wave, which involves the error due to the sea bottom inclination, the trim and the incorrect transducer installation etc. The present doppler log adopts a single transducer, faced in the direction of themain beam, and therefore it is unable to correct the beam direction to eliminate the above mentioned error. Moreover, the frequencyis also limitted in a comparatively high range for getting a sharp beam with single transducer, and the speed over the ground can not be detectable at the deep sea, for an instance, over 200 meters. This paper describes a theoretical consideration for the doppler log error and an analysis by a computer on the observed speed data by a full size model ship. The result is verified that the most of doppler log error is caused by the ultrasonic beam angle of transducer. To eliminate the doppler log error due to the incorrect transducer installation and also to sharpen the beam for lower frequency range to expand measurable sea depth, this paper proposes a method of controlling the directivity adopting a linear transducer array and of controlling the directivity by the control of exciting current, and investigates by the computer simulation and make experiment with magnetostrictive ferrite transducer of 28, 50 and 75KHz. The experimental results are shown well coincide with the measured ones, and they are revealed that in case where the transducer interval is greater than 1 wavelength, the effective control of the beam direction is hardly performed with keeping adequate beam width and side lobe level. It is concluded that 6-elements array with inter element space of a half wavelength can make comparatively sharp beam and low side lobe level. The results obtained here will contribute very much to the improvement of the performance of doppler log.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.13-19
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• 1995

This paper considers model robust accelerated life test plans for estimating the logmean or percentile of product lige which is exponentially distributed. A linear relationship between the log mean life and the stress is assumed as usual, while the true relationship is quadratic. Optimum plans are then obtained by minimizing asymptotic mean squared error of maximum likelihood estimator of the log mean life.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.7
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• pp.1013-1018
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• 2014

In this study, we developed kinetic models to predict the growth of pathogenic Escherichia coli on cheeses during storage at constant and changing temperatures. A five-strain mixture of pathogenic E. coli was inoculated onto natural cheeses (Brie and Camembert) and processed cheeses (sliced Mozzarella and sliced Cheddar) at 3 to 4 log CFU/g. The inoculated cheeses were stored at 4, 10, 15, 25, and $30^{\circ}C$ for 1 to 320 h, with a different storage time being used for each temperature. Total bacteria and E. coli cells were enumerated on tryptic soy agar and MacConkey sorbitol agar, respectively. E. coli growth data were fitted to the Baranyi model to calculate the maximum specific growth rate (${\mu}_{max}$; log CFU/g/h), lag phase duration (LPD; h), lower asymptote (log CFU/g), and upper asymptote (log CFU/g). The kinetic parameters were then analyzed as a function of storage temperature, using the square root model, polynomial equation, and linear equation. A dynamic model was also developed for varying temperature. The model performance was evaluated against observed data, and the root mean square error (RMSE) was calculated. At $4^{\circ}C$, E. coli cell growth was not observed on any cheese. However, E. coli growth was observed at $10{\circ}C$ to $30^{\circ}C$C with a ${\mu}_{max}$ of 0.01 to 1.03 log CFU/g/h, depending on the cheese. The ${\mu}_{max}$ values increased as temperature increased, while LPD values decreased, and ${\mu}_{max}$ and LPD values were different among the four types of cheese. The developed models showed adequate performance (RMSE = 0.176-0.337), indicating that these models should be useful for describing the growth kinetics of E. coli on various cheeses.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.97-104
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• 2010

The materials failure relation $\ddot{\Omega}=A{(\dot{\Omega})}^\alpha$ where $\Omega$ is a measurable quantity such as displacement and the dot superscript is the time derivative, may be used to analyze the accelerating creep of materials. Coefficients, A and $\alpha$, are determined by fitting given data sets. In this study, it is tried to predict the failure time of tunnel using the materials failure relation. Four fitting techniques of applying the materials failure relation are attempted to forecast a failure time. Log velocity versus log acceleration technique, log time versus log velocity technique, inverse velocity technique are based on the linear least squares fits and non-linear least squares technique utilizes the Levenberg-Marquardt algorithm. Since the log velocity versus log acceleration technique utilizes a logarithmic representation of the materials failure relation, it indicates the suitability of the materials failure relation applied to predict a failure time of tunnel. A linear correlation between log velocity and log acceleration appears satisfactory(R=0.84) and this represents that the materials failure relation is a suitable model for predicting a failure time of tunnel. Through comparing the real failure time of tunnel with the predicted failure times from four curve fittings, it is shown that the log time versus log velocity technique results in the best prediction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.920-927
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• 2008

This study deals with modeling of Head-Related Transfer Functions (HRTFs) using Principal Components Analysis (PCA) in the time and frequency domains. Four PCA models based on Head-Related Impulse Responses (HRIRs), complex-valued HRTFs, augmented HRTFs, and log-magnitudes of HRTFs are investigated. The objective of this study is to compare modeling performances of the PCA models in the least-squares sense and to show the theoretical relationship between the PCA models. In terms of the number of principal components needed for modeling, the PCA model based on HRIR or augmented HRTFs showed more efficient modeling performance than the PCA model based on complex-valued HRTFs. The PCA model based on HRIRs in the time domain and that based on augmented HRTFs in the frequency domain are shown to be theoretically equivalent. Modeling performance of the PCA model based on log-magnitudes of HRTFs cannot be compared with that of other PCA models because the PCA model deals with log-scaled magnitude components only, whereas the other PCA models consider both magnitude and phase components in linear scale.

• Journal of Korea Water Resources Association
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• v.40 no.1 s.174
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• pp.39-50
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• 2007

This paper presents applications of the log-linear ROCOF(rate-of-occurrence-of-failure) and the Weibull ROCOF to model the failure rate of individual cast iron pipes in a water distribution system and provides a method of estimating the economically optimal replacement time of the pipes using the 'modified time-scale'. The performance of the two ROCOFs is examined using the maximized log-likelihood estimates of the ROCOFs for the two types of failure data: 'failure-time data' and 'failure-number data'. The optimal replacement time equations for the two models are developed by applying the 'modified time-scale' to ensure the numerical convergence of the estimated values of the model parameters. The methodology is applied to the case study water distribution cast iron pipes and it is found that the log-linear ROCOF has better modeling capability than the Weibull ROCOF when the 'failure-time data' is used. Furthermore, the 'failure-time data' is determined to be more appropriate for both ROCOFs compared to the 'failure-number data' in terms of the ROCOF modeling performances for the water mains under study, implying that recording each failure time results in better modeling of the failure rate than recording failure numbers in some time intervals.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.962-971
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• 2002

The current study proposes a simple monodimensional model to estimate the linear growth rate of photosynthetic microorganisms in flat-plate photobioreactors (FPPBRs) during batch cultivation. As a model microorganism, Chlorella kessleri was cultivated photoautotrophically in FPPBRs using light-emitting diodes (LEDs) as the light sources to provide unidirectional irradiation in the photobioreactors. Various conditions were simulated by adjusting both the intensity of the light and the height of the culture. The validity of the proposed model was examined by comparing the linear growth rates measured with the predicted ones obtained from the proposed model. Accordingly, the value of $\frac{K\cdot\mu m}{\alpha\cdot L}log(I_0\cdot{I_s}^{\varepsilon 1)\cdot {I_c}^{-\varepsilon})$ was proposed as an approximate index for strategies to obtain the maximal lightn yield under light-limiting conditions for high-density algal cultures and as a control parameter to improve the photosynthetic productivity and efficiency.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.6
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• pp.445-452
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• 2015

Software reliability in the software development process is an important issue. Software process improvement helps in finishing with reliable software product. Infinite failure NHPP software reliability models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, proposes the reliability model with log and power intensity function (log linear, log power and exponential power), which made out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on mean square error (MSE) and coefficient of determination($R^2$), for the sake of efficient model, was employed. Analysis of failure, using real data set for the sake of proposing log and power intensity function, was employed. This analysis of failure data compared with log and power intensity function. In order to insurance for the reliability of data, Laplace trend test was employed. In this study, the log type model is also efficient in terms of reliability because it (the coefficient of determination is 70% or more) in the field of the conventional model can be used as an alternative could be confirmed. From this paper, software developers have to consider the growth model by prior knowledge of the software to identify failure modes which can be able to help.

• The Korean Journal of Applied Statistics
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• v.16 no.1
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• pp.55-69
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• 2003

In this article, we propose the weighted LAD (least absolute deviations) estimators for multi-dimensional contingency tables and drive an estimation method to estimate the proposed estimators. To illustrate the robustness of the estimators, simulation results are presented for several models Including log-linear models and models for ordinal variables in multidimensional contingency tables. Examples were also introduced.