• Environmental and Resource Economics Review
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• v.31 no.4
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• pp.451-480
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• 2022

The Japanese Flying Squid (Todarodes pacificus) is a commercially important species in South Korea and the most popular species among consumers. However commercial catches of Japanese Flying Squid have been declining since 2000. In this study, we conducted a stock assessment to identify stock status. This study differed from previous studies in two aspects: a greater amount of available fishing effort data was used, and data from China, Japan, and Korea were included. A CMSY (catch-maximum sustainable yield) model was used to estimate MSY, biomass and exploitation with Bayesian state-space implementation of the Schaefer (BSS) model for the method of stock assessment, and evaluated the species by dividing into two groups, 'Korea' and ' Korea·China·Japan'. In all cases, Japanese flying squid biomass showed a general decreasing trend. Additionally, the biomass estimated for 2020 was lower than the biomass necessary to achieve the maximum sustainable yield. To manage Japanese Flying Squid effectively, it is necessary to strengthen the resource management strategies of individual countries and prepare a cooperative plan among countries.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5D
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• pp.453-459
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• 2010

In the study of traffic safety, it is utmost important to obtain more reliable estimates of the expected crashes for a site (or a segment). The observed crashes have been mainly used as the estimate of the expected crashes in Korea, while the empirical Bayes (EB) estimates based on the Poisson-gamma mixture model have been used in the USA and several European countries. Although numerous studies have used the EB method for estimating the expected crashes and/or the effectiveness of the safety countermeasures, no past studies examine the difference in the estimation errors between the two estimates. Thus, this study compares the estimation errors of the two estimates using a Monte Carlo simulation study. By analyzing the crash dataset at 3,000,000 simulated sites, this study reveals that the estimation errors of the EB estimates are always less than those of the observed crashes. Hence, it is imperative to incorporate the EB method into the traffic safety research guideline in Korea. However, the results show that the differences in the estimation errors between the two estimates decrease as the uncertainty of the prior distribution increases. Consequently, it is recommended that the EB method be used with reliable hyper-parameter estimates after conducting a comprehensive examination on the estimated negative binomial model.

• The Journal of the Acoustical Society of Korea
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• v.29 no.4
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• pp.223-228
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• 2010

High-frequency bottom loss measurements for grazing angle of $82^{\circ}$ in frequency range 17-40 kHz were made in Jinhae bay in the southern part of Korea. Observations of bottom loss showed the strong variation as a function of frequency, which were compared to the predicted values using two-layered sediment reflection model. The geoacoustic parameters including sound speed, density and attenuation coefficient for the second sediment layer were predicted from the empirical relations with the mean grain size obtained from sediment core analysis. The geoacoustic parameters for the surficial sediment layer were inverted using Monte Carlo inversion algorithm. A sensitivity study for the geoacoustic parameters showed that the thickness of surficial sediment layer was most sensitive to the variation of the bottom loss.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.330-338
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• 2015

The influences of fluorescence, scattering, and flocculation in turbid material by light scattering of N-propyl-N,N-dimethylethanolamine, fluorescence agent and absorption agent were interpreted for the scattered fluorescence intensity and wavelength. They have been studied the molecular properties by the spectroscopy of laser induced fluorescence (LIF) and flocculation. The effects of optical properties in scattering media have been found by the optical parameters(${\mu}_s$, ${\mu}_a$, ${\mu}_t$). Flocculation is an important step in many solid-liquid separation processes and is widely used. When two particles approach each other, interactions of several colloid particles can come into play which may have major effect on the flocculation and LIF process. The values of scattering coefficient ${\mu}_s$ are large by means of the increasing scattering of scatterer, The values have been found that the slope decays exponentially as a function of concentration from laser source to detector by our experimental result. It may also aid in designing the best model for oil chemistry, bio-pharmaceutical, laser medicine and application of medical engineering on LIF and coagulation in particle transport mode.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.97-104
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• 2006

In recent years, the MOSFET dosimeter has been widely used in various medical applications such as dose verification in radiation therapeutic and diagnostic applications. The MOSFET dosimeter is, however, mainly made of silicon and shows some energy dependence for low energy Photons. Therefore, the MOSFET dosimeter tends to overestimate the dose for low energy scattered photons in a phantom. This study determines the correction factors to compensate these dependences of the MOSFET dosimeter in ATOM phantom. For this, we first constructed a computational model of the ATOM phantom based on the 3D CT image data of the phantom. The voxel phantom was then implemented in a Monte Carlo simulation code and used to calculate the energy spectrum of the photon field at each of the MOSFET dosimeter locations in the phantom. Finally, the correction factors were calculated based on the energy spectrum of the photon field at the dosimeter locations and the pre-determined energy and directional dependence of the MOSFET dosimeter. Our result for $^{60}Co$ and $^{137}Cs$ photon fields shows that the correction factors are distributed within the range of 0.89 and 0.97 considering all the MOSFET dosimeter locations in the phantom.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.2
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• pp.57-61
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• 2014

Purpose Iodine (I-131) is one of the most widely used radioactive isotopes for therapeutic in the field of nuclear medicine. Therapeutic I-131 capsule is made out of lead to shield high energy radiation. Accurate dosimetry is necessarily required to perform safe and effective work for relative workers. The Monte Carlo method is known as a method to predict the absorbed dose distribution most accurately in radiation therapy and many researchers constantly attempt to apply this method to the dose calculation of radiotherapy recently. This paper aims to calculate distance dependent and activity dependent therapeutic I-131 capsule using GEANT4. Materials and Methods Therapeutic capsules was implemented on the basis of the design drawings. The simulated dose was determined by generating of gamma rays of energy to more than 364 keV. The simulated dose from the capsule at the distance of 10 cm and 100 cm was measured and calculated in the model of water phantom. The simulated dose were separately calculated for each position of each detector. Results According to the domestic regulation on radiation safety, the dose at 10 cm and 100 cm away from the surface of therapeutic I-131 capsule should not exceed 2.0 mSv/h and 0.02 mSv/h, respectively. The simulated doses turned out to be less than the limit, satisfying the domestic regulation. Conclusion These simulation results may serve as useful data in the prediction of hands dose absorbed by I-131 capsule handling. GEANT4 is considered that it will be effectively used in order to check the radiation dose.

• The Korean Journal of Applied Statistics
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• v.10 no.1
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• pp.69-84
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• 1997

We consider a linear calibration problem, $y_i = $$\alpha + \beta (x_i - x_0) + \epsilon_i$, $i=1, 2, {\cdot}{\cdot},n$ $y_f = \alpha + \beta (x_f - x_0) + \epsilon, $ where we observe $(x_i, y_i)$'s for the controlled calibration experiments and later we make inference about $x_f$ from a new observation $y_f$. The objective of the calibration design problem is to find the optimal design $x = (x_i, \cdots, x_n$ that gives the best estimates for $x_f$. We compare Kim(1989)'s Bayesian design which minimizes the expected value of the posterior variance of $x_f$ and some optimal designs from literature. Kim suggested the Bayesian optimal design based on the analysis of the characteristics of the expected loss function and numerical must be equal to the prior mean and that the sum of squares be as large as possible. The designs to be compared are (1) Buonaccorsi(1986)'s AV optimal design that minimizes the average asymptotic variance of the classical estimators, (2) D-optimal and A-optimal design for the linear regression model that optimize some functions of $M(x) = \sum x_i x_i'$, and (3) Hunter & Lamboy (1981)'s reference design from their paper. In order to compare the designs which are optimal in some sense, we consider two criteria. First, we compare them by the expected posterior variance criterion and secondly, we perform the Monte Carlo simulation to obtain the HPD intervals and compare the lengths of them. If the prior mean of $x_f$ is at the center of the finite design interval, then the Bayesian, AV optimal, D-optimal and A-optimal designs are indentical and they are equally weighted end-point design. However if the prior mean is not at the center, then they are not expected to be identical.In this case, we demonstrate that the almost Bayesian-optimal design was slightly better than the approximate AV optimal design. We also investigate the effects of the prior variance of the parameters and solution for the case when the number of experiments is odd.

• International Commerce and Information Review
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• v.13 no.3
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• pp.77-95
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• 2011

This paper investigates the relationship between export and economic variables such as trade insurance, world economy activity, relative price, unemployment rate, exchange rate volatility, using monthly data. I employ Johansen cointegration methodology since the model must be stationary to avoid the spurious results. The results indicate that there is a long-run relationship between export and variables. Also, the empirical analysis of cointegrating vector using the CCR, DOLS, FMOLS reveals that the increases of trade insurance has positive relations and the increases of exchange rate volatility have negative relations with export. Especially, DOLS based on Monte Carlo simulations, of this estimator being superior in small samples compared to a number of alternative estimators, as well as being able not only to accommodate higher orders of integration but also to account for possible simultaneity within regressors of a potential system. This paper also applies impulse-response functions to get the additional information regarding the responses of the export to the shocks of the variables. The result indicates that export positively to trade insurance and then decay fast compare with exchange rate volatility. Consequently, trade insurance plays the role of trade policy for export promotion in Korea. Whereas, increase of exchange risk result in reduction of export. Therefore, the support of trade insurance should be expanded and the stabilization of the foreign exchange market must be done for the export promotion.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.2
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• pp.799-805
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• 2016

Background: There is no standard treatment for patients with platinum-resistant or refractory epithelial ovarian cancer. Single agent chemotherapies have evidence of more efficacy and less toxicity than combination therapy. Most are very expensive, with appreciable toxicity and minimal survival. Since it is difficult to make comparison between outcomes, economic analysis of single-agent chemotherapy regimens and best supportive care may help to make decisions about an appropriate management for the affected patients. Objective: To evaluate the cost effectiveness of second-line chemotherapy compared with best supportive care for patients with platinum-resistant or refractory epithelial ovarian cancer. Materials and Methods: A Markov model was used to estimate the effectiveness and total costs associated with treatments. The hypothetical patient population comprised women aged 55 with platinum-resistant or refractory epithelial ovarian cancer. Four types of alternative treatment options were evaluated: 1) gemcitabine followed by BSC; 2) pegylated liposomal doxorubicin (PLD) followed by BSC; 3) gemcitabine followed by topotecan; and 4) PLD followed by topotecan. Baseline comparator of alternative treatments was BSC. Time horizon of the analysis was 2 years. Health care provider perspective and 3% discount rate were used to determine the costs of medical treatment in this study. Quality-adjusted life-years (QALY) were used to measure the treatment effectiveness. Treatment effectiveness data were derived from the literature. Costs were calculated from unit cost treatment of epithelial ovarian cancer patients at various stages of disease in King Chulalongkorn Memorial Hospital (KCMH) in the year 2011. Parameter uncertainty was tested in probabilistic sensitivity analysis by using Monte Carlo simulation. One-way sensitivity analysis was used to explore each variable's impact on the uncertainty of the results. Results: Approximated life expectancy of best supportive care was 0.182 years and its total cost was 26,862 Baht. All four alternative treatments increased life expectancy. Life expectancy of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 0.510, 0.513, 0.566, and 0.570 years, respectively. The total cost of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 113,000, 124,302, 139,788 and 151,135 Baht, respectively. PLD followed by topotecan had the highest expected quality-adjusted life-years but was the most expensive of all the above strategies. The incremental cost-effectiveness ratios (ICER) of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 344,643, 385,322, 385,856, and 420,299 Baht, respectively. Conclusions: All of the second-line chemotherapy strategies showed certain benefits due to an increased life-year gained compared with best supportive care. Moreover, gemcitabine as second-line chemotherapy followed by best supportive care in progressive disease case was likely to be more effective strategy with less cost from health care provider perspective. Gemcitabine was the most cost-effective treatment among all four alternative treatments. ICER is only an economic factor. Treatment decisions should be based on the patient benefit.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.176-186
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• 2014

Roughness, aperture and filling material of rock joint are widely considered to affect the hydraulic characteristics of joint. Among these factors, in this study, the joint roughness was examined with artificial joint profiles generated by Monte Carlo simulating on the original profiles suggested by Barton and Choubey(1977). Original profiles and revised profiles were combined to establish flow channel models, in which the hydraulic characteristics were analyzed numerically on the basis of minimum aperture changes and flow channel shapes. Maximum flow rate was identified at the growing point of flow area after passing through minimum aperture generated by the two profiles, and it was resulted that maximum flow rate is inversely proportional to minimum aperture. Maximum flow rate per unit area showed different values because flow channel shapes and minimum aperture locations are different in each model. In flow channel, mechanical aperture showed approximately 1.07 ~ 3.00 times larger than hydraulic aperture. In this study, mechanical and hydraulic aperture were concluded to be closely related to $A_i$ value, and their relations can be denoted by $e_m=0.519A^{0.7169_i}$ and $e_h=0.6182A^{0.239}_i$, respectively.