• Journal of Korea Port Economic Association
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• v.32 no.3
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• pp.35-46
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• 2016

This study investigates the export behavior of Busan, Gwangyang and Incheon Port. The monthly data cover the period from January 2000 to December 2015. We employ six export functions composed of various exchange rates and industrial production index. This paper finds that the nominal effective exchange rate is more appropriate for explaining the export behaviors of the three ports, regardless of the narrow and wide indices which comprise 26 and 61 economies for the nominal and real indices respectively. This paper tests whether exchange rate and industrial production are stationary or not, rejecting the null hypothesis of a unit root in each of the level variables and of a unit root for the residuals from the cointegration at the 5 percent significance level. The error-correction model is estimated to find that both Gwangyang and Incheon ports are much slower than Busan port in adjusting the short-run disequilibrium and Gwangyang port is a little slower than Incheon port. The rolling regressions show that the influence of exchange rate as well as industrial production tends to decrease in all of three ports. The variance decomposition, however, shows that the export variables are very exogenous and the export of Busan Port is the least exogenous and that of Gwangyang Port the most. This result indicates that the economic variables such as exchange rate and economic activity affect the export of Busan Port more strongly than that of Gwangyang and Incheon Port.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.188-196
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• 2021

For the tactical vehicles operated by the Korean army, the hub-reduction portal axle was applied considering Korea's topographical characteristics. Hub-reduction was applied to a Korean military vehicle to increase the vehicle body to secure ground clearance and improve the driving capability on rough roads, such as unpaved and field land by increasing the torque. The Korean military is operating tactical vehicles after various performance tests, including durability driving, but wheel damage occurred in one of the vehicles operating in the front units. Failure analysis revealed many damaged parts, including the hub, making it difficult to determine the cause. Therefore, an analysis of the failure occurrence mechanism for each damaged part was conducted, which confirmed that the cause of wheel breakage was a hub. Furthermore, the root cause of the hub breakage was a crack due to internal pores and foreign matters. In addition, a realistic improvement plan that can be applied throughout the design, manufacture, and shipping stages was presented using the fishbone diagram analysis. The derived improvement plan was verified through unit performance tests, including CAE and actual vehicle tests, and by reflecting this, the driving safety of Korean tactical vehicles was improved. Finally, it is expected that the proposed method for analyzing the failure occurrence mechanism will be used as reference material when analyzing the quality problems of similar military vehicles in the future.

• KDI Journal of Economic Policy
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• v.14 no.1
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• pp.37-60
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• 1992

This paper applies a Structural VAR approach to a 4 variable system in real GNP, M2, GNP deflator and nominal monthly earnings, disentangling 4 structural shocks, i.e., aggregate demand and supply shocks, wage pushes and various forms of regulations reinforced especially during stabilization process. Preliminary diagnostic tests confirm that the log level of each time series has at least one unit root, though the evidence is somewhat ambiguous for real GNP. One co-integration relationship is found among 4 variables, while no co-integration is found in a subsystem consisting of nomina) variables. The absence of co-integration among nominal variables strongly suggested that money is not neutral even in the long-run. The reduced form is estimated and the structural form is recovered using 6 additional identifying restrictions. Recovered structural shocks are able to capture main episodes of past 20 years, ranging from first and second oil shocks, to strong stabilization policy of early 80's and rapid wage hikes of late 80's. Overall responses of the economy to each structural shock are usually consistent with the standard Keynesian predictions, though some responses seem to be specific to Korean economic environment.

• Journal of Food Hygiene and Safety
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• v.34 no.6
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• pp.509-518
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• 2019

To monitor the levels of antimicrobials, allergens, pathogens and other contaminants in foods meant for human consumption, it is imperative to have quick, accurate and low-cost tests. Advanced techniques (e.g. label-free biosensor assays) have been developed over the past 10-15 years to solve some of these problems. As biosensors, immunosensors can provide real-time measurements, a high degree of automation, and improved throughput and sensitivity. By comparison with conventional methods, immunosensors are less expensive, less sophisticated physicochemical instruments that require less time for analysis while also being more user-friendly. In this review, we discuss our current knowledge about immunosensors, their strengths and weaknesses, as well as the future of these biosensors in food safety.

• Ocean and Polar Research
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• v.36 no.4
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• pp.327-341
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• 2014

This study aims to analyze causality among Wando abalone producer prices by size using a vector autoregressive model to expiscate the leading-price of Wando abalone in various price classes by size per kg. This study, using an analytical approach, applies a unit-root test for stability of data, a Granger causality test to learn about interaction among price classes by size for Wando abalone, and a vector autoregressive model to estimate the statistical impact among t-1 variables used in the model. As a result of our leading-price analysis of Wando abalone producer prices by shell size using a VAR model, first, DF, PP, and KPSS tests showed that the Wando abalone monthly price change rate by size differentiated by logarithm were stable. Second, the Granger causality relationship analysis showed that the price change rate for big size abalone weakly led the price change rate for the small and medium sizes of abalone. Third, the vector autoregressive model showed that three price change rates of t-1 period variables statistically, significantly impacted price change rates of own size and other sizes in t period. Fourth, the impulse response analysis indicated that the impulse responses of structural shocks for price change rate for big size abalone was relatively more powerful in its own size and in other sizes than shocks emanating from other sizes. Fifth, the variance decomposition analysis indicated that the price change rate for big size abalone was relatively more influential than the price change rates for medium and small size abalone.

• Journal of Korean Society of Forest Science
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• v.89 no.1
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• pp.1-8
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• 2000

This paper investigates the empirical validity of market integration for the five softwood lumber markets in Canada : Atlantic, Quebec, Ontario, Prairie, and British Columbia (BC). The Augmented Dickey-Fuller (ADF) tests of monthly price series for the period 1987 : 10-1998 : 11 reveal strong evidence for the presence of a unit root in each series. Accordingly, the Johansen cointegration technique is used to test for the law of one price in the five regional markets. Results show that the law holds in the pair, three, four, and five markets, supporting the hypothesis of market integration.

• International Commerce and Information Review
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• v.14 no.4
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• pp.27-47
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• 2012

The study aims to analyze how the variables for Korea, such as the exports, imports, FDI(Inward) and FDI(Outward), influence the economic growth and how they affect each other. For the purpose of empirical analysis, this paper used the quarterly time series data from 1980 to 2010, dividing the period before and after 1997(IMF). The variables used in this study were log-transformation from the original variables. This study empirically tests the relationship among variables by using VECM with considering the time-series properties of each variable. The results found from the study are as followings. Causality analysis using VECM proved that no causality between GDP and exports existed, whereas causality between GDP and FDI(Inward) existed, in which GDP affected FDI(Inward) since IMF. However, it was found that other periods and FDI(Inward) did not affect GDF and had no causality among them.

• Journal of Ginseng Research
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• v.8 no.2
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• pp.153-166
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• 1984

The anticancer activities of petroleum ether extract of Panax ginseng root(crude GX) and its partially purified fraction from silicic acid column chromatography (7:3 GX) were studied with Sarcoma 180(S-180) or Walker carcinosarcoma 256 (Walker 256) in vivo and with L1210 leukemic lympocyte in vitro. Potential cytotoxic activities of the crude GX and against L1210 cells were compared with those of 5-Fluorouracil (5-FU) and saponin derivatives (Panax-diol, Panax-triol, Diol saponin, Triol saponin) in vitro. In order to observe the physiological effects of the crude GX and 7:3 GX on the animals with cancer, hemoglobin(Hb), red blood cell(R.B.C) and white blood cell after treatment with each GX in comparison with corresponding control groups, respectively. The anticancer effects of the crude GX and 7:3 GX were estimated by measuring the survival time of S-180 bearing mice after treatment with them. The experimental results obtained are summarized as follows; 1. The one unit of cytotoxic activity against L1210 cells was equivalent to 2.54$\mu\textrm{g}$ and 0.88$\mu\textrm{g}$of the crude GX and 7:3 GX per ml of culture medium, respectively. 2. The cytotoxic activities of Panax-diol, Panax=triol, Diol saponin and triol saponin against L1210 cells were not detected. 3. The anticancer activities of 5-FU against L1210, S-180 and Walker 256 were very effective in vivo and vitro tests. 4. The significantly increased W.B.C values of mice after inoculation with S-180 cells were reduced to normal range by the crude GX treatment. 5. The significantly decreased Hb values of rats after inoculation with Walker 256 were recovered to normal range by oral administration of the crude GX. 6. The survival times of mice inoculated with S-180 cells were extended about 1.5 to 2 times by the 7:3 GX treatment compared with their control group.

• Restorative Dentistry and Endodontics
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• v.40 no.2
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• pp.123-127
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• 2015

Objectives: Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. Materials and Methods: The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). Results: The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). Conclusions: Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

• The Journal of Advanced Prosthodontics
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• v.14 no.2
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• pp.122-132
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• 2022

PURPOSE. This in-vitro analysis aimed to compare the intaglio trueness, the antagonist's wear volume loss, and fracture load of various single-unit zirconia prostheses fabricated by different manufacturing techniques. MATERIALS AND METHODS. Zirconia crowns were prepared into four different groups (n = 14 per group) according to the manufacturing techniques and generations of the materials. The intaglio surface trueness (root-mean-square estimates, RMS) of the crown was measured at the marginal, axial, occlusal, and inner surface areas. Half of the specimens were artificially aged in the chewing simulator with 120,000 cycles, and the antagonist's volume loss after aging was calculated. The fracture load for each crown group was measured before and after hydrothermal aging. The intaglio trueness was evaluated with Welch's ANOVA and the antagonist's volume loss was assessed by the Kruskal-Wallis tests. The effects of manufacturing and aging on the fracture resistance of the tested zirconia crowns were determined by two-way ANOVA. RESULTS. The trueness analysis of the crown intaglio surfaces showed surface deviation (RMS) within 50 ㎛, regardless of the manufacturing methods (P = .053). After simulated mastication, no significant differences in the volume loss of the antagonists were observed among the zirconia groups (P = .946). The manufacturing methods and simulated chewing had statistically significant effects on the fracture resistance (P < .001). CONCLUSION. The intaglio surface trueness, fracture resistance, and antagonist's wear volume of the additively manufactured 3Y-TZP crown were clinically acceptable, as compared with those of the 4Y- or 5Y-PSZ crowns produced by subtractive milling.