• KDI Journal of Economic Policy
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• v.12 no.4
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• pp.21-46
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• 1990

This paper, a sequel to Yoo and Lee (1990), attempts to investigate the interindustry determinants of technical efficiency in Korea's manufacturing industries, and also to conduct an exploratory analysis on the stability of technical efficiency over time. The hypotheses set forth in this paper are most found in the existing literature on technical efficiency. They are, however, revised and shed a new light upon, whenever possible, to accommodate any Korea-specific conditions. The set of regressors used in the cross-sectional analysis are chosen and the hypotheses are posed in such a way that our result can be made comparable to those of similar studies conducted for the U.S. and Japan by Caves and Barton (1990) and Uekusa and Torii (1987), respectively. It is interesting to observe a certain degree of similarity as well as differentiation between the cross-section evidence on Korea's manufacturing industries and that on the U.S. and Japanese industries. As for the similarities, we can find positive and significant effects on technical efficiency of relative size of production and the extent of specialization in production, and negative and significant effect of the variations in capital-labor ratio within industries. The curvature influence of concentration ratio on technical efficiency is also confirmed in the Korean case. There are differences, too. We cannot find any significant effects of capital vintage, R&D and foreign competition on technical efficiency, all of which were shown to be robust determinants of technical efficiency in the U.S. case. We note, however, that the variables measuring capital vintage effect, R&D and the degree of foreign competition in Korean markets are suspected to suffer from serious measurement errors incurred in data collection and/or conversion of industrial classification system into the KSIC (Korea Standard Industrial Classification) system. Thus, we are reluctant to accept the findings on the effects of these variables as definitive conclusions on Korea's industrial organization. Another finding that interests us is that the cross-industry evidence becomes consistently strong when we use the efficiency estimates based on gross output instead of value added, which provides us with an ex post empirical criterion to choose an output measure between the two in estimating the production frontier. We also conduct exploratory analyses on the stability of the estimates of technical efficiency in Korea's manufacturing industries. Though the method of testing stability employed in this paper is never a complete one, we cannot find strong evidence that our efficiency estimates are stable over time. The outcome is both surprising and disappointing. We can also show that the instability of technical efficiency over time is partly explained by the way we constructed our measures of technical efficiency. To the extent that our efficiency estimates depend on the shape of the empirical distribution of plants in the input-output space, any movements of the production frontier over time are not reflected in the estimates, and possibilities exist of associating a higher level of technical efficiency with a downward movement of the production frontier over time, and so on. Thus, we find that efficiency measures that take into account not only the distributional changes, but also the shifts of the production frontier over time, increase the extent of stability, and are more appropriate for use in a dynamic context. The remaining portion of the instability of technical efficiency over time is not explained satisfactorily in this paper, and future research should address this question.

• Sleep Medicine and Psychophysiology
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• v.9 no.1
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• pp.41-47
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• 2002

Objectives: In a number of simulated night shift studies, timed exposure to bright light improves sleep quality and work performance. We evaluated the effect of bright light on adaptation to night shift work with a field study. Methods: Five female nurses working shifts at Korea University Hospital were recruited for participation in this study. We investigated two series of six consecutive shift rotations comprising three day and three night shifts, using wrist Actigraphy, the Stanford Sleepiness Scale, Visual-analogue scales, STIM and tympanic membrane temperature for daytime sleep quality, alertness, subjective feeling, attention performance, and temperature rhythm. The subjects were exposed to bright light (2,500 lux) from 24:00 to 04:00 a.m. on three consecutive night shifts during the second series, whereas they worked under normal lightening (650 lux) conditions during the first series. Results: Actigraphic assessment of daytime sleep showed no significant difference between the first and third night shift in both baseline and light exposure phase. The mean lowest temperature shifted earlier during baseline phase but not during the light exposure phase. Also, the score for subjective feelings of depression, anxiety, physical discomfort and sleepiness was significantly higher in the third night shift than the first during baseline phase but not during the light exposure phase. Attention and attention switching ability was significantly improved in the third night shift compared to the first night during the light exposure phase but there were no significant changes during the baseline phase. Conclusion: This result suggests that there were no significant differences between the two phases in measures of quality of daytime sleep, but subjective feelings, attention and alertness were enhanced during light exposure. Although some placebo effects and learning effects might influence this result, bright light exposure between midnight and 4:00 a.m. may improve adaptation to night shift. In future, further controlled studies with a larger sample size, including melatonin measurement, are needed for real shift workers.

• Parasites, Hosts and Diseases
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• v.22 no.2
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• pp.171-180
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• 1984

In order to provide some clues for differential diagnosis of trematode infections in fecal examination, the comparative morphology of eggs of 5 kinds of heterophyid flukes (Metagonimus yokogawai, Heterophyes heterophyes nocens, Heterophyopsis continua, Stellantchasmus falcatus and Pygidiopsis summa) and Clonorchis sinensis was studied. The eggs were obtained from distal portion of uteri of worms which were recovered from men after treatment. The characteristic shape and appearance of each kind of eggs were observed in detail under light microscope, and their length and width measured and compared one another. The results are as follows: 1. Eggs of C. sinensis are elongated ovoidal in shape with attenuated anterior end, 25.3~33. 2 (28. 3 in average) ${\mu}m$ long and 14.2~17.4(5.9) ${\mu}m$ wide with length/width ratio of 1.60~2.00 (1.78). They differ from all heterophyid eggs in that they have prominent wrinkling (muskmelon pattern) at their shell surface. 2. P. summa eggs are ovoid to pyriform in shape and characterized by the smallest size of all kinds examined, 19.8~22.9 (21.6) ${\mu}m$ long and 11.1~13.4 (12.1) ${\mu}m$ wide and the ratio 1.63~1.99 (1.78). 3. Eggs of S. falcatus are elongated ovoidal and most slender form, 25.3~29.2 (27.2) ${\mu}m$ long and 11.1~13.4 (12.5) ${\mu}m$ wide with the ratio of 2.00~2.57 (2.17). 4. Eggs of M. yokogawai are ellipsoid to elliptical in shape with round both ends, 26.9~31.6 (28.5) ${\mu}m$ long and 14.2~18.2 (16.8)${\mu}m$ wide with the ratio of 1.48~2.11 (1.70). 5. H. continua eggs are oval in shape, sometimes similar to M. yokogawai or H. h. nocen$ eggs, however, the relative breadth is broadest among all kinds, with maximum width at posterior half portion. They are 23.7~27.7 (25.0) ${\mu}m$ long, 15.8~18.9 (16.4) ${\mu}m$ wide with the ratio of 1. 33~1.75 (1.53). 6. Eggs of H. h. nocens are ellipsoid to ovoid in shape but sometimes more slender than M. yokogawai and have slightly pointed both ends. They are 23.7~29.2 (25.7) p.m long, 14.2~15.8 (15.4) ${\mu}m$ wide, and the ratio 1.50~2.06 (1.67). From the results, it is concluded that eggs, of 5 kinds of heterophyids and C. sinensis can be morphologically differentiated one another, however, careful observation and measurement on sufficient number of eggs are needed.

• Tuberculosis and Respiratory Diseases
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• v.65 no.6
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• pp.504-511
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• 2008

Background: Particulate matter may be toxic to human tissue. Ambient air particulate matter ${\leq}10{\mu}m$ in aerodynamic size ($PM_{10}$), which changes under different environmental conditions, is a complex mixture of organic and inorganic compounds. The Asian dust event caused by meteorological phenomena can also spread unique particulate matter in affected areas. We evaluated production of ROS, $TGF-{\beta}$, fibronectin, and $NF{\kappa}B$ by exposing normal epithelial cells to Asian dust particulate matter. Methods: Bronchial epithelial cells were exposed to 0, 50, ${\leq}100{\mu}g/ml$ of a suspension of $PM_{10}$ for 24 h. ROS were detected by measurement of DCF release from DCF-DA by FACScan. $TGF-{\beta}$, fibronectin, and $NF{\kappa}B$ were detected by western blotting. Results: $PM_{10}$ exposure increased the expression of $TGF-{\beta}$, fibronectin, and $NF{\kappa}B$. ROS production and $TGF-{\beta}$ levels were significantly higher with 50 or ${\leq}100{\mu}g/ml$ $PM_{10}$. Fibronectin and $NF{\kappa}B$ production were significantly higher after ${\leq}100{\mu}g/ml$ of $PM_{10}$. Conclusion: $PM_{10}$ from Asian dust particles might have fibrotic potential in bronchial epithelial cells via ROS induction after $PM_{10}$ exposure.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.746-763
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• 1996

An alternative design to conventional class II cavity preparation for proximal carious lesions is the tunnel preparation. It preserves the marginal ridge intact, thus making it possible to maintain the natural contact relationship with the adjacent tooth and minimize tooth reduction. This in vitro study was purposed to evaluate the effect of the materials' elastic constants and shear-bond strength on the marginal ridge fracture resistance of teeth restored by the tunnel technique, and to find the materials of choice for tunnel restorations. $Resinomer^{(R)}$, $Ketac-silver^{(R)}$, $Miracle-Mix^{(R)}$, and Tytin were used as restorative material. The elastic constants of each restorative material were evaluated by ultrasonic pulse measurement. Young's modulus and bulk modulus of the restorative materials were evaluated in three specimens for each material type. The shear-bond strength of the restorative materials to the dentin surface was measured after thermocycling 400 times between 6 and $60^{\circ}C$, using ten specimens for each material type. For measuring marginal ridge strength, 60 sound extracted molar teeth were distributed into six groups by size. Sound molar teeth were used as a Control group and unfilled prepared teeth were grouped as Unrestored. Another four groups were named Resinomer group, Ketac-Silver group, Miracle Mix group, and Tytin group by type of restorative material. Tunnel cavity preparation was done with ' 1/2, 2, and 4 round burs in sequence. Initial access to proximal surface was made through an occlusal access preparation started at least 2mm from the marginal ridge, and the proximal opening was formed about 2.5mm below the marginal ridge. After restoration and thermocycling, marginal ridge strength was measured using a universal testing machine. The results were as follows: 1. The Young's modulus of $Tytin^{(R)}$ was 63.95 GPa, followed by $Ketac-Silver^{(R)}$ 27.60 GPa, $Miracle-mix^{(R)}$ 18.48 GPa, and $Resinomer^{(R)}$ 10.74 GPa showing significant differences between the groups(P<0.05). The bulk modulus of the materials showed the same order as Young's modulus. The value of $Tytin^{(R)}$ showed 59.57 GPa indicating that it will deform less than other materials under the same stress. It was followed by $Ketac-Silver^{(R)}$ 23.57 GPa, Miracle $Mix^{(R)}$ 12.50 GPa, and $Resinomer^{(R)}$ 11.60 GPa. 2. The Resinomer group had a shear-bond strength of 7.41 MPa which was significantly higher than those of the Ketac-Silver group (1.80 MPa) and the Miracle Mix group (2.84 MPa) (P<0.01). All the specimens of Tytin group detatched from the dentin surface during thermocycling. 3. The mean marginal ridge strength of the Unrestored group(46.14 kgf) was significantly lower than that of the Control group (84.24 kgf) (P<0.01). The marginal ridge strength of teeth restored by the tunnel technique was, in order, Ketac-Silver group 74.06 kgf, Miracle Mix group 73.36 kgf, Resinomer group 63.47 kgf, and Tytin group 58.76 kgf. The Ketac-Silver, Miracle Mix, and Resinomer groups showed no significant difference with the Control group (P>0.05), but the Tytin group showed significantly lower strength compared to the Control group(P<0.05). The results showed that the marginal ridge strength of the teeth restored by the tunnel technique was not significantly lower than that of sound teeth. They also demonstrated that the bonding strength of the restorative material to the tooth surface should be high and the modulus of elasticity should not be lower than that of the tooth in order to restore the marginal ridge strength to its natural condition.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.9
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• pp.1106-1113
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• 2017

The objective of this study was to determine the quality characteristics of fried yakgwa and baked yakgwa prepared with different amounts of P. frutescens powder. Moisture contents of fried yakgwa were 7.05%, and moisture content of baked yakgwa with different amounts of P. frutescens powder were 12.42~10.44% and decreased with higher amount of P. frutescens powder. This result can be attributed to loss of water in yakgwa in the course of the fried process. Although the degree of expansion of baked yakgwa was lower than that of fried yakgwa, size and shape of yakgwa were maintained. Yakgwa is appropriate as a cookie type product. Crude lipid contents of fried yakgwa were higher than those of baked yakgwa due to the exchange reaction of water and fat during the fried process. Energy of fried yakgwa was 501 kcal and was higher than that of baked yakgwa with different amounts of P. frutescens powder. This greatly affected the fat content of each sample. Energy of baked yakgwa increased with higher amount of P. frutescens powder due to the characteristics of the ingredients or jasoyeop. For chromaticity determination, L values of fried yakgwa were lower, but a, and b values were higher than those of baked yakgwa, and L, a, and b values decreased when P. frutescens powder increased. Texture measurement showed that hardness, cohesiveness, chewiness, gumminess increased with higher amounts of P. frutescens powder, whereas springiness decreased. The antioxidant activities of fried yakgwa measured based on DPPH scavenging activity were higher than those of baked yakgwa with 0%~0.2% P. frutescens powder and lower than those of baked yakgwa with 0.3%~0.4% P. frutescens powder. In the sensory evaluation, baked yakgwa with 0.1% addition of P. frutescens powder showed the highest preference in terms of overall acceptance, and 0% addition of P. frutescens powder showed the highest preference in terms of color and flavor. These results suggest that P. frutescens powder may be a useful ingredient in baked yakgwa to improve quality and sensory properties.

• Journal of Distribution Research
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• v.16 no.1
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• pp.65-93
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• 2011

This paper aims to explore how relational constructs(supplier's idiosyncratic investment, retailer's dependence, and dyadic communication) impact the buyer's trust across the relationship lifecycle. Companies make great efforts to create trust and maintain long-term relationship with buyers. Buyer and supplier relationships evolve through distinct lifecycles. In each phase, buyers and suppliers exhibit different patterns of behaviour. Also, they have different attitudes toward, and expectation of, one another. In this study, the final outcome investigated is long-term orientation from the buyer's perspective. Data were collected from 296 survey questionnaires of retailers engaging in Crops Protected Material industry in Korea. Exploratory factor analysis and confirmatory factor analysis were used to purify the measurement scales. And structural equation analysis and Chow test were used to test the hypotheses. The result indicates that the effect of retailer's dependence on the trust is greatest. Especially, the effect of dependence is growing as the relationship has developed. Supplier's idiosyncratic investment increases trust in the early phase, while it is not found to affect trust in the maturity phase. In the early phase, the determination of trust begins to be increasingly influenced by partner's relationship investment only because other clues are not observed yet. Reciprocal communication has a positive effect on trust, and long-term orientation is directly influenced by retailer's trust. Communication's effect is greater in the build-up phase than in the maturity phase. A limitation of this study is the unequal sample size in each of the relationship phases. Literature has suggested that the effects of relational constructs on outcomes are different across relationship phases. This study shows that different relational constructs have different effects on trust depending upon the relationship phase.

• Journal of Animal Science and Technology
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• v.44 no.6
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• pp.643-652
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• 2002

Data were consisted of the ten body measurements (withers height, rump height, body length, chest depth, chest width, rump width, rump length, thurls width, hipbone width and chest girth) of 642 steers (Korean cattle), which was entered in the National Beef Quality Contest hosted by the Korea Animal Improvement Association from 1997 to 2001. A principal components analysis was used to classify the body types of the steers, and estimate the correlations between carcass traits and principal components for the body measurements of the first, second, third and fourth period, respectively. The first principal component of body measurements at the first, second, third and fourth period accounted for 76.0%, 83.0%, 72.7% and 57.4% of the total variance, respectively. The sum of first, second and third principal component at each period accounted for 86.69%, 90.49%, 84.62% and 77.26% of the total variance, respectively. At each period, all the first principal component of the body measurements were positive and it generally showed large framed body shape. The size of body was influenced mostly by chest depth(0.328${\sim}$0.339) and rump length(0.325${\sim}$0.341). The second, third and fourth principal component at the each period were various. There were positive correlations between principal components index of each period and carcass traits such as carcass weight(0.539${\sim}$0.755), average daily gain(0.256${\sim}$0.564), backfat thickness(0.227${\sim}$0.280), and eye muscle area(0.187${\sim}$0.344). The correlation with yield grade index(－0.246${\sim}$－0.110), however, was negative. The correlation with marbling score(0.066${\sim}$0.099) was low or statistically insignificant. According to principal component indexes of the second, third, and fourth components, the correlations with the carcass traits were various. There were no large differences between the correlations of the single body measurement trait with the carcass traits and the correlations of the first principal component indexes with the carcass traits.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.290-294
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• 2009

Larval development of Nannopaya pygmaea Rambur (Libellulidae), an endangered dragonfly in Korea, was studied using an introduced lariat population in an artificial wetland habitat. Artificial habitat was created in a green house which imitated a small wetland in Boryeong-si, Chungcheongnam-do, Korea, where N. pygmaea inhabited. A total of 300 N. pygmaea larvae were introduced to the artificial habitat in June 2007. Larvae were recaptured five times between June 2007 and November 2008 for measurement of body length. As a result, the initial and recaptured populations (Recaptured I, II, III, IV, and V populations, respectively) contained two body size groups [initial 6.20$\pm$0.34 mm and 7.94$\pm$0.46 mm (mean$\pm$SD); Recaptured I 2.84$\pm$0.43 mm and 5.16$\pm$0.83 mm; Recaptured II 5.96$\pm$0.66 mm and 8.02$\pm$0.35 mm; Recaptured III 5.97$\pm$0.73 mm and 7.82$\pm$0.37 mm; Recaptured IV 7.04$\pm$0.93 mm and 8.52$\pm$0.39 mm; Recaptured V 5.72$\pm$0.60 mm and 7.71$\pm$0.30 mm]. Our rearing experiment evidenced that the recaptured I-V populations are the offspring of the initial population and the offspring grew approximately 3 mm at 470 degree days. It was also estimated that N. pygmaea larvae need approximately 100 degree days to grow 0.7 mm in body length.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.4
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• pp.357-365
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• 2016

We observed the ${\gamma}-ray$ shielding characteristics and compressive strength of five types of concrete using general aggregates and high-weight aggregates. The aggregates were classified into fine aggregate and coarse aggregate according to the average size. The experimental results obtained an attenuation coefficient of $0.371cm^{-1}$ from a concrete with the oxidizing slag sand (OSS) and oxidizing slag gravel (OSG) for a ${\gamma}-ray$ of $^{137}Cs$, which is improved by 2% compared with a concrete with typical aggregates of sand and gravel. In the unit weight measurement, a concrete prepared by iron ore sand (IOS) and OSG had the highest value of $3,175kg{\cdot}m^{-3}$. Although the unit weight of the concrete with OSS and OSG was $3,052kg{\cdot}m^{-3}$, which was lower than the maximum unit weight condition by $123kg{\cdot}m^{-3}$, its attenuation coefficient was improved by $0.012cm^{-1}$. The results of chemical analysis of aggregates revealed that the magnesium content in oxidizing slag was lower than that in iron ore, while the calcium content was higher. The concrete with oxidizing slag aggregates demonstrated enhanced ${\gamma}-ray$ shielding performance due to a relatively high calcium content compared with the concrete with OSS and OSG in spite of a low unit weight. All sample concretes mixed with high-weight aggregates had higher compressive strength than the concrete with typical sand and gravel. When OSS and IOS were used, the highest compressive strength was 50.2 MPa, which was an improvement by 45% over general concrete, which was achieved after four weeks of curing.