• The Journal of Korean Academy of Prosthodontics
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• v.18 no.1
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• pp.15-35
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• 1980

The purpose of this study was to investigate stresses in the various components of fixed partial dentures restoring the posterior teeth of the lower jaw, and to measure quantitatively the effects of certain modifications in structural design on the stresses in the restorations using two-dimensional photoelasticity. Two-dimensional photoelastic methods were used in this study. Several models of fixed partial dentures were constructed. Shoulder less margins and anatomic occlusal reduction were incorporated in Model 1. Rounded shoulders and flat occlusal reduction were incorporated in Model 2, while Model 3 was a cantilever fixed partial denture. Other similar fixed partial dentures were constructed with V and U notches deliverately included in the region of the fixed joints for comparative reasons. The birefringent materials used in this study were PSM-1 and PSM-5 in standard sheets. PSM-1 was used for constructing the substructure, and PSM-5 was used in making the components of the fixed partial dentures. The two materials were used in the construction of composite photoelastic models. Improved artificial stone was used to represent dental cement in luting the composite photoelastic models. Static loading procedures were used at preplanned sites to represent occlusal loads in the mouth. 35 mm color and B/W film were used to record isochromatics in accordance with photoelastic procedures. Data reduction was performed using the grid method, which helped in, the mathematical integration procedure (Shear difference method) to separate the principal stresses. The results were as follows. 1. Fixed partial dentures do not function in bending as a symmetrical beam. Alternate areas of tension and compression were demonstrated when multiple contact loading was used. 2. The weakest part in posterior fixed partial dentures is the fixed joint. 3. (1) Models I and modified Model I were loaded on the pontic using a 50 pound vertical static load. The shear stress near the posterior fixed joint in Model 1 (U notches) was+129.4 p.s.i., and at the same fixed joint in modified Model 1 (V notches) was+239.4 p.s.i. The concentration of stress in fixed joint was reduced by 50% when U notches replaced the V notches. (2) Modified Model 2 was loaded using a multiple contact loader at a total load of 125 pounds. The difference between the principal stresses (${\sigma}_1-{\sigma}_2$), shear stress, at the V notches was+600 p.s.i., and at the U notches was+3l7 p.s.i. The shear stress was reduced by 50% when U notches replaced the V notches. V-grooves at the fixed joints should be avoided, and should be replaced by regular shaped U-grooves. 4. Cantilever fixed partial dentures had much higher stresses at the fixed joint than fixed partial dentures that were attached at both ends.

• Journal of the Korean Operations Research and Management Science Society
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• v.34 no.1
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• pp.85-100
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• 2009

An online marketplace, such as eBay, is an example of two-sided markets. In online marketplaces, there are transactions between sellers and buyers and direct competition effects among sellers and among buyers. Previous research on two-sided market has not handle these competition effects and mostly focused on indirect network externalities between sellers and buyers. We analyze the fee structure of an online marketplace considering direct competition effects among sellers and among buyers. We find that when fees for sellers and buyers can be imposed, an auction or fixed-pricing rule can be chosen according to the characteristics of a product traded. But when only fees for sellers can be imposed, an auction can be taken as a trading mechanism solely.

• East Asian Economic Review
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• v.16 no.2
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• pp.205-225
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• 2012

I use panel data of sales by the foreign subsidiaries of the U.S. MNCs to examine whether trading blocs create more or less FDI and the impacts on FDI of the extended market size created by forming blocs. By employing a region-fixed effects model, I find that countries forming trading blocs attract more FDI, particularly from non-member countries, but that FDI does not always increase with the market size of the blocs. As the market size increases, FDI increases only for large blocs. However, these findings are sensitive to model specifications. A policy implication is that a country considering forming or joining a trading bloc with a view to attract FDI may want to form a trading bloc with a country or countries with a large market size.

• Journal of Labour Economics
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• v.37 no.2
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• pp.79-103
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• 2014

Previous studies show that tall people have better labor market outcomes, but controlling for their abilities reduces the size of height effects. This implies that a failure to properly control for one's ability could overestimate the OLS estimate. This paper contributes to the literature by being the first to control for individual fixed effects (FE) and to examine height effects on the probability of one's attaining a leadership position. The data used are panel data of a cohort obtained during the cohort's middle and high school years. In OLS estimation, this paper finds positive height effects for boys. However, when controlling for individual fixed effects, the estimate is not statistically significant. For girls, the height effects are found on neither OLS nor FE model.

• The Journal of Fisheries Business Administration
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• v.51 no.1
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• pp.81-96
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• 2020

The purpose of this paper is to analyze factors affecting the net income of regional and industrial fisheries cooperatives in South Korea using panel data. This paper utilizes linear or GLS regression models such as pooled OLS model, fixed effects model, and random effects model to estimate affecting factors of the net income of regional and industrial fisheries cooperatives. After reviewing various tests, we eventually select random effects model. The results, based on panel data between 2013 and 2018 year and 64 fisheries cooperatives, indicate that capital and area dummy variables have positive effects and employment has negative effect on the net income of regional and industrial fisheries cooperatives as predicted. However, debt are opposite with our predictions. Specifically, it turns out that debt has positive effect on the net income of regional and industrial fisheries cooperatives although it has been increased. Additionally, this paper shows that the member of confreres does not show any significant effect on the net income of regional and industrial fisheries cooperatives in South Korea. This study is significant in that it analyzes the major factors influencing changes in the net income that have not been conducted recently for the fisheries cooperatives by region and industry.

• KCID journal
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• v.19 no.1
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• pp.64-76
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• 2012

Recently, it has been increased disaster of crops and agricultural facilities with climate change such as regional storm, typhoon. However agricultural facilities have unsafe design criteria of improving drainage corresponding to this change. This study has analyzed the impact that inundation area and magnitude of drainage-facility is decided based on fixed- and unfixed-duration precipitation by applying revised design criteria of drainage for climate change. The result was shown that 1-day and 2-days rainfall for 20-years return period has increased about 11.4%, 4.4% respectively by changing fixed- to unfixed duration. And the increase rate of design flood was 15.0%. The result was also shown that Inundation area was enlarged by 6.6% as well as increased inundation duration under same basic condition in designed rainfall between fixed- and unfixed-duration. According to the analysis, it is necessary for pump capacity in unfixed-duration to be increased by 70% for same effect with fixed-duration. Therefore, when computing method of probability precipitation is changed from fixed one to unfixed-duration by applying revised design criteria, there seems to be improving effect in drainage design. Because 1440-minutes rainfall for 20-years return period with unfixed-duration is more effective than 1-day rainfall for 30-years return period with fixed-duration. By applying unfixed-duration rainfall, capacity of drainage facilities need to be expanded to achieve the same effects (Inundation depth & duration) with fixed-duration rainfall. Further study is required for considering each condition of climate, topography and drainage by applying revised design criteria.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.417-424
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• 2019

Despite its superior ability to show distinct cellular morphology and for long-term storage, conventional tissue fixation by formalin has many drawback, including slower fixation, the exposure to harmful chemicals and extensive protein modification. Herein, we assessed the effects of rapid microwave-assisted tissue fixation on histological examination and on protein integrity by comparing these microwave irradiation fixated tissues with the formalin-fixed tissues. One of the paired mouse tissues (liver and kidney) was fixed in formalin and the other was fixed by using microwave irradiation in phosphate buffered saline. Each slide from the paraffin-embedded tissues was examined by H & E staining for the adequacy of fixation and by immunohistochemical staining for antigenicity in a blinded fashion. Evaluation of protein recovery and the protein quality from the fixed tissues were analyzed by the BCA method and Western blotting, respectively. The results from H & E staining and immunohistochemical staining showed that the sections obtained from microwave-fixed tissues under our experimental conditions were comparable to those of the formalin-fixed tissues except for the integrity of RBCs. Furthermore, proteins were effectively extracted from the microwave-fixed tissues with acceptable preservation of the proteins' quality. Taken together, this microwave-assisted tissue processing yields a quick fixation and better protein recovery in higher amounts, as well as the adequacy of fixation and the antigenicity being comparable to formalin-fixed tissues, and this all suggests that this new fixation technique can be applied in an environment where rapid tissue fixation is required.

• Journal of Labour Economics
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• v.34 no.3
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• pp.81-117
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• 2011

This study examined how firms responded to the articles regarding the prohibition or correction of discrimination against fixed-term workers in the 'fixed-term worker protection law', which has been effective since July of 2007 in Korea. Data used cone from the Korean Workplace Survey, and a difference-in-differences method was employed for the identification of the causal effect, noting that the 'discrimination prohibition law' has been applied to firms over stages based on their sizes. The empirical results show no strong evidence that the law played a positive role in reducing differentials between permanent workers and fixed-term workers in the areas of wage and various employee benefits, including the provision of severance pay, annual leave, and 4 major social insurances for fixed-term workers. A more thorough future analysis on the causes of the insignificant impact of the law in some employee welfare benefits, along with supplemental policies, is needed to have the law achieve the desired goal of removing discrimination at the workplace.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.73-84
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• 2020

In the seismic design of bridges, formation of plastic hinges plays an important role in the dissipation of seismic energy. In the case of conventional fixed-base bridges, the plastic hinges are allowed to form in the superstructure alone. During seismic event, such bridges may be safe from collapse but the superstructure undergoes significant plastic deformations. As an alternative design approach, the plastic hinges are guided to form in the soil thereby utilizing the inevitable yielding of the soil. Rocking foundations work on this concept. The formation of plastic hinges in the soil reduces the load and displacement demands on the superstructure. This study aims at evaluating the seismic response of bridge pier supported on rocking shallow foundation. For this purpose, a BNWF model is implemented in OpenSees platform. The capability of the BNWF model to capture the SSI effects, nonlinear behavior and dynamic loading response are validated using the centrifuge and shake table test results. A comparative study is performed between the seismic response of the bridge pier supported on the rocking shallow foundation and conventional fixed-base foundation. Results of the study have established the beneficial effects of using the rocking shallow foundation for the seismic response analysis of the bridge piers.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.10
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• pp.219-228
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• 2021

The study examines the behavior of stock prices after large price changes. It further examines the effect of firm size on stock returns, and the presence of the disposition effect. The study employs the event study methodology using daily price data from Pakistan Stock Exchange (PSX) for the period January 2001 to July 2012. Furthermore, to examine the factors that explain stock price behavior after large price movements, the study employs a two-way fixed-effect model that allows for the analysis of unobservable company and time fixed effects that explain market reversals or continuation. The findings suggest that winners perform better than losers after experiencing large price shocks thus showing a momentum behavior. In addition, the winners remain the winner, while the losers continue to lose more. This suggests that most of the investors in PSX behave rationally. Further, the study finds no evidence of disposition effect in PSX. The investors underreact to new information and the prices continue to move in the direction of initial change. The pooled regression estimates show that firm size is positively related to post-event abnormal returns while the fixed-effect model reveals the presence of unobservable firm-specific and time-specific effects that account for price continuation.