• Environmental and Resource Economics Review
• /
• v.17 no.4
• /
• pp.751-774
• /
• 2008

In this paper, we examine the institutional prices differences in the electricity and natural gas industries using unbalanced panel data from 1999 to 2001. The changing market structures following deregulation in both markets allow us to examine the institutional prices differences by ownership type, market structure and merger activities. Estimating the reduced form, after controlling both intrinsic characteristic (marginal costs) and external factors (demand), allows us to identify the extent to which specific factors are correlated with the price. Furthermore it allows us to identify systematic institutional price differences in both electricity and natural gas markets. Our estimation results suggest that the private firms in electricity markets are associated with higher prices than public firms after controlling for demand and cost. We further find that dual-product firms in the natural gas industry and the electricity industry are associated with lower rates than single product firms. These results provide a weak evidence of economies of scope in the dual-product firms. Our results finally suggest that merger activities in natural gas markets are associated with higher rates.

• Journal of radiological science and technology
• /
• v.37 no.3
• /
• pp.223-231
• /
• 2014

Medical linear accelerator is widely used in radiation treatment field, and high energy photons, above 10 MV nominal accelerator voltage, are commonly utilized for the radiation treatment. However, these high energy photons lead the photo-nuclear reaction and the generation of photo-neutrons are accompanied. Thus, these problematic factors are issued in the view of radiation protection. Therefore, linear accelerator and radiation treatment room are simulated from MCNPX program in this study. The measurement points of interest are selected and analyzed, and the resulting effects derived from the properties of photo-neutron are evaluated. Therefore, we realized that the number of generating photo-neutrons was decreased by depending on the distance from the source. No matter what the nominal energy is set, the rates thermal neutrons to fast neutrons are marginal. It is founded that the amount of the thermal neutrons were decreased by depending on the distance from the source.

• Journal of Korean Society of Transportation
• /
• v.30 no.3
• /
• pp.57-70
• /
• 2012

Variable speed limit(VSL) is a useful speed management tool for alleviating traffic congestion and enhancing traffic safety. The purpose of this study is to identify promising freeway segments for safety enhancement through VSL operations. An ordered probit model was adopted to capture factors affecting freeway crash severity that can be used to support decision making for selecting the promising segments. Pseudo elasticity and marginal effects, which are outcomes of the ordered probit analysis, were used to determine priority of promising segments for traffic safety. The results of this study would be useful in installing VSL systems and developing traffic control and operations strategies in practice.

• Preventive Nutrition and Food Science
• /
• v.14 no.3
• /
• pp.233-239
• /
• 2009

The effects of guar gum (GG) and xanthan gum (XG) at different concentrations (0, 0.2, 0.4, and 0.6% w/w) on the rheological properties of Korean waxy rice starch (WRS) pastes were evaluated under both steady and dynamic shear conditions. The flow properties of WRS-gum mixtures were determined from the rheological parameters of the power law model. The addition of GG and XG to WRS resulted in an increase in the apparent viscosity ($\eta_{a,100}$) and consistency index (K) values obtained from power law model. The flow behavior index (n) values of the WRS-XG mixtures decreased with an increase in gum concentration while there was only a marginal difference between n values for the WRS-GG mixtures. Dynamic moduli (G', G", and $\eta^*$) values in the WRS-gum mixture systems also increased with an increase in gum concentration. WRS-XG mixtures had higher dynamic moduli and lower tan $\delta$ (ratio of G"/G') values than WRS-GG mixtures, indicating that the higher dynamic rheological properties of WRS-XG can be attributed to an increase in the viscoelasticity of the continuous phase in the starch-gum mixture systems, which was due to the higher viscoleastic properties of XG compared to GG. The dynamic ($\eta^*$) and steady shear ($\eta_a$) viscosities of the WRS-XG paste at a 0.2% gum concentration followed the Cox-Merz superposition rule.

• The Journal of Korean Academy of Prosthodontics
• /
• v.58 no.2
• /
• pp.169-175
• /
• 2020

Traditionally, gingival retraction has been performed to obtain customized abutment impressions with subgingival margins of the implant supported prosthesis. However, gingival retraction may have side effects such as gingival recession and bleed, leading to an inaccurate impression. In order to prevent these problems, in this case, the new technique has been introduced; a customized abutment which is designed for superimposition is used. Before the connection of the abutment to the implant fixture, pre-scanned shape data are stored, and then the optical impression without gingival retraction is obtained after connecting to the fixture. The suprastructure is fabricated by superimposing the two data. This technique showed the clinical efficacy of fabricating the implant supported prosthesis with subgingival margin, which satisfied the aesthetics, convenience, and clinically acceptable marginal and internal fit.

• Molecular & Cellular Toxicology
• /
• v.5 no.3
• /
• pp.257-264
• /
• 2009

Gardenia yellow, extracted from gardenia fruit, has been widely used as a coloring agent for foods, and thus, safety of its usage is of prime importance. In the current study, short-term genotoxicity assays were conducted to evaluate the potential genotoxic effects of gardenia yellow. The gardenia yellow used was found to contain 0.057 mg/g of genipin, a known biologically active compound of the gardenia fruit extract. Ames test did not reveal any positive results. No clastogenicity was detected by a chromosomal aberration test, even on evaluation at the highest feasible concentration of gardenia yellow. Gardenia yellow was also shown to be non-genotoxic using an in vitro comet assay and a micronucleus test with L5178Y cells, although a marginal increase in DNA damage and micronuclei frequency was reported in the respective assays. Additionally, in vivo micronucleus test results clearly demonstrated that oral administration of gardenia yellow did not induce micronuclei formation in the bone marrow cells of male ICR mice. Taken together, our results indicate that gardenia yellow is not mutagenic to bacterial cells, and that it does not cause chromosomal damage in mammalian cells, either in vitro or in vivo.

• The Korean Journal of Applied Statistics
• /
• v.27 no.6
• /
• pp.991-1002
• /
• 2014

Both Bayesian and maximum likelihood methods are efficient for the estimation of regression coefficients of various Tobit regression models (see. e.g. Chib, 1992; Greene, 1990; Lee and Choi, 2013); however, some researchers recognized that the maximum likelihood method tends to underestimate the disturbance variance, which has implications for the estimation of marginal effects and the asymptotic standard error of estimates. The underestimation of the maximum likelihood estimate in a seemingly unrelated Tobit regression model is examined. A Bayesian method based on an objective noninformative prior is shown to provide proper estimates of the disturbance variance as well as other regression parameters

• Journal of Korea Multimedia Society
• /
• v.3 no.4
• /
• pp.380-388
• /
• 2000

In computing the optical flow, Horn and Schunck's method which is a representative algorithm is based on differentiation. Therefore it is difficult to estimate the velocity for a large displacement by this algorithm. In this paper, we propose a method for estimating nonuniform motion from sequential images which is based on integral brightness constancy constraints. The equations which transform a source image to a target image are expressed as a function of the displacement field. If marginal effects can be neglected, the form of the transformation integral transform or orthogonal expansion can be determined from the expansion coefficients of the two images. The apparent displacement field is then computed iteratively by a projection method which utilities the functional derivatives of the linearized moment equations. We demonstrate that the performance of the orthogonal function transform on the data set of large motion.

• Archives of Plastic Surgery
• /
• v.47 no.3
• /
• pp.242-249
• /
• 2020

Background The Exoscope is a novel high-definition digital camera system. There is limited evidence signifying the use of exoscopic devices in microsurgery. This trial objectively assesses the effects of the use of the Exoscope as an alternative to the standard operating microscope (OM) on the performance of experts in a simulated microvascular anastomosis. Methods Modus V Exoscope and OM were used by expert microsurgeons to perform standardized tasks. Hand-motion analyzer measured the total pathlength (TP), total movements (TM), total time (TT), and quality of end-product anastomosis. A clinical margin of TT was performed to prove non-inferiority. An expert performed consecutive microvascular anastomoses to provide the exoscopic learning curve until reached plateau in TT. Results Ten micro sutures and 10 anastomoses were performed. Analysis demonstrated statistically significant differences in performing micro sutures for TP, TM, and TT. There was statistical significance in TM and TT, however, marginal non-significant difference in TP regarding microvascular anastomoses performance. The intimal suture line analysis demonstrated no statistically significant differences. Non-inferiority results based on clinical inferiority margin (Δ) of TT=10 minutes demonstrated an absolute difference of 0.07 minutes between OM and Exoscope cohorts. A 51%, 58%, and 46% improvement or reduction was achieved in TT, TM, TP, respectively, during the exoscopic microvascular anastomosis learning curve. Conclusions This study demonstrated that experts' Exoscope anastomoses appear non-inferior to the OM anastomoses. Exoscopic microvascular anastomosis was more time consuming but end-product (patency) in not clinically inferior. Experts' "warm-up" learning curve is steep but swift and may prove to reach clinical equality.

• KDI Journal of Economic Policy
• /
• v.31 no.1
• /
• pp.207-237
• /
• 2009

One of the main problems in Korea's public assistance program, the NBLS (National Basic Livelihood Security), is that the loophole of welfare system is continuously growing. Living wage program is the largest sub-program of the NBLS, and the most important determinant of amount of living wage for each beneficiary is the level of reported income. Therefore, accurate and effective income detection is essential in improving policy effects and furthermore reducing the leakage of wage expenditure as beneficiaries always have an incentive to underreport their income. Since most of them do not pay income tax, the welfare authority should exert an independent effort to effectively detect their income. Considering that living wage is a special kind of income tax of which marginal tax rate is -1, one can apply a classical theory of tax evasion to understand illegal or excessive receipt of living wage caused by income underreporting. Utilizing a classical theory given by Alingham and Sandmo (1972), this paper provides a theoretical analysis of the optimal income reporting of the beneficiary. Then an optimization problem is constructed from the government's viewpoint to derive optimal income detecting device (auditing). This paper proves that cut-off discriminated auditing outperforms random auditing and cut-off auditing which implies if the government assigns a positive audit probability to every reported income less than a certain level and the probability is inversely proportional to the level of reported income, it can minimize underreporting and then gradually reduce the leakage of wage expenditure.