• Environmental and Resource Economics Review
• /
• v.30 no.4
• /
• pp.535-555
• /
• 2021

This study empirically analyzes the effects of international oil prices on domestic stock market volatility. The data used for the analysis are 10-minute high-frequency data of the KOSPI index and WTI futures price from January 2, 2015, to July 30, 2021. For using the high-frequency data, a heterogeneous autoregression (HAR) model is employed. The analysis model utilizes the advantages of high frequency data to observe the impact of international oil prices through realized volatility, realized skewness, and kurtosis as well as oil price return. In the estimation, the Box-Cox transformation is applied in consideration of the distribution of realized volatility with high skewness. As a result, it finds that the daily return fluctuation of the WTI price has a statistically significant positive (+) effect on the volatility of the KOSPI return. However, the volatility, skewness, and kurtosis of the WTI return do not appear to affect the volatility of the KOSPI return. This result is believed to be because the volatility of the KOSPI return reflects the daily change in the WTI return, but does not reflect the intraday trading behavior of investors.

• Structural Engineering and Mechanics
• /
• v.81 no.2
• /
• pp.205-217
• /
• 2022

The thermodynamic properties of shaft lining concrete (SLC) are important evidence for the design and construction, and the spatial variability of concrete materials can directly affect the stochastic thermal analysis of the concrete structures. In this work, an array of field experiments of the concrete materials are carried out, and the statistical characteristics of thermophysical parameters of SLC are obtained. The coefficient of variation (COV) and scale of fluctuation (SOF) of uncertain thermophysical parameters are estimated. A three-dimensional (3-D) stochastic thermal model of concrete materials with heat conduction and hydration heat is proposed, and the uncertain thermodynamic properties of SLC are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between autocorrelation functions distance (ACD) and SOF for the five theoretical autocorrelation functions (ACFs), the effects of the ACF, COV and ACD of concrete materials on the uncertain thermodynamic properties of SLC are analyzed. The results show that the spatial variability of concrete materials is subsistent. The average temperatures and standard deviation (SD) of inner SLC are the lowest while the outer SLC is the highest. The effects of five 3-D ACFs of concrete materials on uncertain thermodynamic properties of SLC are insignificant. The larger the COV of concrete materials is, the larger the SD of SLC will be. On the contrary, the longer the ACD of concrete materials is, the smaller the SD of SLC will be. The SD of temperature of SLC increases first and then decreases. This study can provide a reliable reference for the thermodynamic properties of SLC considering spatial variability of concrete materials.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.31 no.1
• /
• pp.54-62
• /
• 1995

In order to telemeter the behavior and distribution of fishes. the telesounder was manufactured and it was examined to verify its performance and effects in the gape nets with wings located around Gokunsan islands. Yellow Sea. on August 8. 18~19 and September 8~9, 1994. The behavior of fish entering the net was observed with the buoy station at sea which was installed at the entrance of the gape nets with wing and its echosignal was transmitted remotely to the base station on ship at distance of about 1 km away from the buoy station at sea. The fishes catched by the gape nets with wings were 12 species and Anchovy(Engraulis japonica), Beka squid(Loligo beka), Herring(Harengula zunasi) was 95% of total catches. The images of color display monitor at the base station on ship were very well coincident with the records of fish finder from the buoy station located at sea. When the current velocity was less than 0.6 kt and slight fluctuation, the fishes entered into the gape net were much more in comparision with over 1.0kt and heavy fluctuation, and then the average swimming depth was about 4 m. The catches per one hauling was about 10~30 kg and when the current velocity was too weak and the current direction did not coincident with the direction of net or the current velocity was too strong, the catches was a few. It is concluded that telesounder system is very useful for investigating the distribution and the swimming behavior of fishes entering in the gape nets with wings.

• Journal of Distribution Science
• /
• v.18 no.5
• /
• pp.99-109
• /
• 2020

Purpose: This study aims to develop and empirically analyze a research model in order to comprehend the relationship among the service quality of market-wholesaler system, re-transaction intention, and recommendation intention of forwarder. Further, we suggest new six factors reflecting the service quality of market-wholesaler system and highlight market expansion of forwarder as a mechanism in the relationship. Research design, data and methodology: The authors developed the new scales measuring the service quality of market-wholesaler system (i.e. trade price, price fluctuation, payment receipt, settlement period, trade information, and customer service) and conducted a cross-sectional survey for 439 forwarders in a wholesale market. And then we performed a series of path analyses to test hypotheses. The hypotheses are as follows. [H1] The service quality of market-wholesaler system will positively affect forwarders' market expansion, [H2] Forwarders' market expansion will positively affect their re-transaction intention, [H3] Forwarders' market expansion will positively affect their recommendation intention, [H4] Forwarders' re-transaction intention will positively affect their recommendation intention. Results: The results showed that all the six factors for the service quality of market-wholesaler system were positively related to market expansion of forwarders. There was a differential effectiveness in the six factors of the service quality. More specifically, the positive effect of customer service factor was the strongest on market expansion of forwarders. And the respective effects of trade price, price fluctuation, settlement period, trade information factors were followed in order. The positive effect of payment receipt factor was the weakest on market expansion of forwarders. Also, market expansion of forwarders was positively related to their re-transaction intention and recommendation intention. Furthermore, market expansion of forwarders was indirectly related to recommendation intention through re-transaction intention as well. Conclusions: The research findings provide important theoretical and practical implications. This study is the first to attempt to test the perception of forwarders for the service quality of market-wholesaler system by developing and using the new scales. Also, there has been a sharp controversy about the effectiveness of market-wholesaler system. The findings support that market-wholesaler system would be activated by empirically verifying the effectiveness of the service quality on the various outcomes.

• Korean Journal of Soil Science and Fertilizer
• /
• v.31 no.3
• /
• pp.291-300
• /
• 1998

A study was carried out to evaluate the effect of different salts and their Quantities on the fluctuation and rhizosphere colonization of soil microorganisms. The results obtained are as follows. The electrical conductivities(ECs) of $KNO_3$, $K_2HPO_4$, KCl and $K_2SO_4$ showed negative correlations to the number of gram positive bacteria and gram negative bacteria : the number of bacteria was significantly decreased in the KCl or $KNO_3$ treated group compared to the $K_2HPO_4$ or $K_2SO_4$ treated group. The highest microorganism density of gram negative bacteria, gram positive bacteria and Fusarium sp. in balanced salts-treated soil was observed at $0.5dS\;m^{-1}$, $2.1dS\;m^{-1}$ and $8.0dS\;m^{-1}$ of EC, respectively. The ratio of bacteria to fungi ratio in balanced salts-treated soil substantially decreased as the EC of soil increased. Ten and thirty days after soil treatment with balanced salts, the ratio of bacteria to fungi decreased to 757-1571 and 89-215, respectively. Root colonization density of Fluorescent Pseudomonas in cucumber and tomato significantly decreased as the EC of soil increased, whereas that of Fusarium sp. increased.

• Korean journal of applied entomology
• /
• v.39 no.4
• /
• pp.245-250
• /
• 2000

These studies were conducted to investigate the effect of temperature on the development and seasonal occurrence of Chrysopa pallens Ramber, a predator of aphids. Mean developmental periods of C. pallens from egg to adult emergence at four different temperatures of 17, 22, 27, and $30^{\circ}C$ were 39.5, 32.0,25.0, and 19.8 days, respectively. The longevities of adult females of C. pallens at the four temperatures were 84.7, 79.6, 77.7, and 69.8 days, respectively, whereas the total numbers of eggs laid by a female were 973, 1085, 1637, and 1735, respectively. Egg hatchability, rate of adult emergence, and sex ratio of C. pallets were slighty higher with increased temperature with 84.1~95.9%, 67.6~86.3%, and 1:1. Under three humidity conditions of 35, 55 and 75% RH, the mean developmental periods of C. pallets from egg to adult emergence at the $27^{\circ}C$ were 26, 24, and 22.9 days, respectively, while the number of eggs laid by a female were 1042.8, 1526.5, and 1640.0, respectively. Oviposition of C. pallets usually began 5~6 days after the emergence at $27^{\circ}C$. Then females laid ca. 30~40 eggs a day, reaching a peak of 80~90 eggs a day about 22~28 days after the emergence. Population fluctuation of M. persicae and A. gossypii showed the highest peak in late May through the mid-June, and the second peak appeared in early~mid-September. The adult occurrence of C. pallens by the light trap record started from mid-May, and show two peaks, in mid-late July and mid-late September in Chonbuk area.

• Korean Journal of Food Science and Technology
• /
• v.28 no.4
• /
• pp.624-631
• /
• 1996

Effect of fluctuation range and intervals of defrosting temperature on quality of frozen foods stored in a domestic refrigerator equipped with an automatic defrost system was evaluated. As defrost system was operated, temperatures of domestic refrigerators were elevated from $-18^{\circ}C\;to\;-5^{\circ}C\;and\;-15^{\circ}C$, and fluctuation intervals were l6 hrs and 30 hrs, respectively. Quality deterioration such as protein denaturation, vitamin loss, exudate production and changes in appearance of frozen foods was minimized by reducing temperature oscillation during storage. Considerable effects of thermal oscillation on ice crystal sizes were observed for frozen beef tissue and ice cream. TTI (time temperature indicator) system also proved that the temperature control of defrost system in domestic refrigerator can improve the quality of foods during storage.

• Korean Journal of Environment and Ecology
• /
• v.29 no.5
• /
• pp.681-692
• /
• 2015

It is well documented that physiological and nutritional condition of wintering birds is strongly related to migration success to breeding sites, and also breeding success. However, how abiotic factors during winter affect the migration and breeding successes still remains unclear. Thus, this study developed a dynamic-state-dependent model for wintering life-history to identify the potential impact on the life-history, success to breeding site and breeding success of wintering birds, which are related to temperature fluctuation, interspecific competition and human disturbance at the wintering sites. To find the best-fit-model, we referred to the existing research data on wintering ecology of Red-crowned cranes (Grus japonensis) in Cheolwon, Korea, which is well documented as a long-term wintering study. Our model predicted that the higher temperature fluctuation and a higher rate of human disturbance are negatively related to migration success to breeding sites and their fitness, ultimately breeding success via changing of proportion in resource allocation (for e. g., lower energy compensation or higher level of stress accumulation). Particularly, the rate of body mass compensation after arrival at wintering sites may be accelerated when there are less temperature fluctuations and a lower rate of human disturbance. In addition, the rate of interspecific competition sharing the wintering foraging sites is negatively related to the rate of body mass compensation. Consequently, we discussed the conservation strategies of wintering birds based on the outcomes of the model.

• Journal of Korean Society of Transportation
• /
• v.33 no.5
• /
• pp.478-487
• /
• 2015

This study proposed a Variable Speed Limits(VSL) algorithm to use traffic information based on Cumulative Demand-Capacity Analysis and evaluated its performance. According to the analysis result, the total of delay consisted of 3 separate parts. There was no change in total travel time although the total of delay decreased. These effects was analysed theoretically and then, evaluated through VISSIM, a microscopic simulator. VISSIM simulation results show almost same as those of theoretical analysis. Furthermore in SSAM analysis with VISSIM simulation log, the number of high risk collisions decreased 36.0 %. However, the total delay decrease effect is not real meaning of decrease effect because the drivers' desired speed is same whether the VSL model is operated or not. Nevertheless this VSL model maintains free flow speed for longer and increases the cycle of traffic speed fluctuation. In other words, this is decrease of delay occurrence and scale. The decrease of speed gap between upstream and downstream stabilizes the traffic flow and leads decrease number of high risk collision. In conclusion, we can expect increase of safety through total delay minimization according to this VSL model.

• The Journal of the Acoustical Society of Korea
• /
• v.39 no.4
• /
• pp.351-363
• /
• 2020

Launch vehicles are subject to airborne acoustic loads during atmospheric flight and these effects become pronounced especially in transonic region. As the vibration due to the acoustic loads can cause malfunction of payloads, it is essential to predict and reduce the acoustic loads. In this study, a complete process has been developed for predicting airborne vibro-acoustic environment inside the payload pairing and subsequent noise reduction procedure employing acoustic blankets and Helmholtz resonators. Acoustic loads were predicted by Reynolds-Averaged Navier-Stokes (RANS) analysis and a semi-empirical model for pressure fluctuation inside turbulent boundary layer. Coupled vibro-acoustic analysis was performed using VA One SEA's Finite Element Statistical Energy Analysis (FE-SEA) hybrid module and ANSYS APDL. The process has been applied to a hammerhead launch vehicle to evaluate the effect of acoustic load reduction and accordingly to verify the effectiveness of the process. The presently developed process enables to obtain quick analysis result with reasonable accuracy and thus is expected to be useful in the initial design phase of a launch vehicle.