• Journal of the Korean earth science society
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• 제44권3호
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• pp.196-209
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• 2023

The Nishinoshima volcano, located 940 km south of Tokyo, experienced an eruption from June to August 2020. The volcanic gas and ash from the eruption of Nishinoshima that occurred at the end of July 2020 was reported to have the potential to affect the Korean Peninsula. In this study, we used Ash3D, a numerical simulation program for volcanic ash dispersion, to investigate the eruption that occurred at 0:00 local time on July 28, 2020, with a volcanic explosivity index of three. The results showed that the volcanic ash cloud reached Okinawa on the morning of July 30, carried by an east wind. It then moved northward and reached Jeju Island on August 1, eventually circulating in a clockwise direction and reaching southern part of the Korean Peninsula on August 2. The concentration of Particulate Matter 10 (PM₁₀), measured at the Jeju Gosan Meteorological Observatory in Jeju Island, increase from August 1. A similar increase in PM₁₀ concentration was observed at the Gudeok Mountain Weather Station in Busan from August 2. These findings suggested that eruption of the Nishinoshima volcano had an impact on the fine dust concentrations at Jeju Island and southern part of the Korean Peninsula.

• The Journal of the Convergence on Culture Technology
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• 제9권5호
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• pp.661-667
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• 2023

Five commercially available edible sweeteners are used as diet products because they can replace sucrose. In studies on the effects on animals and the human body, stability has been proven by excreting-oriented studies with characteristics of animal cells, and accumulation in small amounts has been ignored. On the other hand, plants can absorb, degrade, and accumulate foreign substances, so the effect of degradability and accumulation potential can be studied using plants. Metabolic effects in plants of commercially available saccharin and acesulfame potassium (Ace K) were tested using germinated barley and bean sprouts. In germinated barley and bean sprouts, saccharin and ace K showed inhibitory effects on plant growth in all organs from low concentrations in leaves, stems and roots. In addition, it can be observed that the symptoms of death appear clearly over time, so it can be seen that they are accumulated in the body of the plant. As the accumulated amount increases, the toxic effect increases and the plant reaches a state where it is unable to metabolize, turning black from the tip of the leaf and reaching a state of death. In order to remove the accumulated artificial sweetener, recovery was attempted by culturing in distilled water, but it acts as a substance that is not degraded and dies without avoiding toxicity. Saccharin and ace K cannot be excreted from the cell. Its toxic effects are thought to be persistent, inhibiting growth and eventually leading to cell death.

• Journal of Life Science
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• 제33권10호
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• pp.835-841
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• 2023

To determine the characteristics of propolis fermented with microorganisms, the optimal conditions for propolis extraction with ethanol were first reviewed, and the physicochemical properties of the extracted propolis were then investigated. The shaking and stationary extraction methods were tested. The flavonoid content was 6.40 mg/g when the stationary extraction method was used and 6.95 mg/g when the shaking extraction method was used. The ethanol concentration was then varied, and the use of 50, 60, 70, and 80% ethanol resulted in the total flavonoid content in the propolis samples reaching 6.75, 8.45, 7.45, and 7.75 mg/g, respectively. This indicated that a 60% (v/v) concentration was optimal. As the extraction time was increased from 1 to 3 hr, the flavonoid content slightly increased; however, extending the extraction step to more than 3 hr did not significantly affect the flavonoid content. In terms of the extraction temperature, the highest concentration of flavonoids (8.63 mg/g) was detected at 50℃. In the propolis samples, 5.80, 2.61, and 1.32 mg/g of fructose, sucrose, and rhamnose were detected, respectively. As for the amino acid content, 17 amino acids, including glutamic acid, were detected, and the total amino acid content was 2.49 mg/g.

• Journal of the Korean Institute of Gas
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• 제27권4호
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• pp.12-18
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• 2023

The effective evacuation strategy according to the accident scenario is crucial to minimize human casualties in the event of toxic gas leak accidents. In this study, the effect of the direction of a building and the location of an industrial complex on the increase in indoor concentration and outdoor diffusion was examined under the same leakage conditions, and effective evacuation criteria were established. In addition, the guidelines for building directions were suggested when constructing buildings that would mitigate human damage caused by chemical accidents. Three scenarios where buildings faced the front, side, and rear of the leakage direction were investigated through CFD simulations. The results revealed that when the building faced the industrial complex, both indoor and outdoor average gas concentrations increased significantly, reaching up to 120 times higher than the other two orientations. Moreover, the indoor space was filled with toxic gas substances more than twice in the same time due to the rapid increase of indoor concentration rate. In cases where the building's windows were positioned at the front, toxic gas stagnation occurred around the building due to pressure differences and reduced flow velocities. Based on our findings, the implementation of these guidelines will contribute to safeguarding residents by minimizing exposure to toxic gas during chemical accidents.

• Fisheries and Aquatic Sciences
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• 제27권4호
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• pp.240-255
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• 2024

Widas Reservoir is situated in an area of 570 ha in the Pajaran Village, Madiun Regency, East Java Province, Indonesia, playing an essential role in fisheries, with the average fish catch per year of about 283 tons/year. This study explores the standing stock, growth parameters, mortality, and exploitation rates of several dominant fishes in Widas Reservoir. This study was carried out from February to November 2019. Fish stocks were estimated using acoustic tools, fish catch records, and sizes collected by local enumerators. Fish length frequency sampling was conducted on several dominant fish species, such as Oreochromis niloticus, Barbonymus gonionotus, and Osteochilus vittatus. Based on the length-frequency data, estimating fish population dynamics, the fish population dynamics (infinitive length (L_∞) and growth coefficient (K)) estimation was run in a time series using the Fish Sock Analysis Tool, II (FISAT II) program package. Moreover, the estimation of natural mortality parameters, the fishing mortality parameter, and the exploitation rate was also performed. The approximated overall fish stock in the Widas Reservoir was about 79,848 kg, which lowered with the increase in water depth. Of particular concern, in the surface layer at a depth between 1-5 m, the fish stock reached 58,813 kg, while in the deeper zone (> 15 m), the value significantly lowered by about 98%, reaching 1,219 kg. These results indicate an overfishing in the Widas Reservoir. The value of the exploitation rate (E) of B. gonionotus was 0.748, O. niloticus 0.8, and O. vittatus 0.7, respectively, proving the overfishing states occurred in the study area. Therefore, regulations governing the number of catches and the use of fishing gear are crucial in Widas Reservoir, particularly the use of lift and gill nets with a mesh size of less than 2 cm.

• Journal of Global Scholars of Marketing Science
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• 제20권2호
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• pp.173-178
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• 2010

A privately held, third generation family owned company, Boom Technologies, Inc. (BTI), a provider of products and services to the electric utility, telecommunications and contractor markets, continues to make progress in exporting. Although export sales only equaled 5% of total revenue in 2008, BTI has an entire export division. Their export division's Managing Director reveals the trial and errors of a privately held company and their quest for success overseas. From its inception, BTI has always believed its greatest asset is its employees. When export sales struggled due to lack of strategy and direction, BTI hired a Managing Director for its export division. With leadership and guidance from BTI's president and from the Managing Director, they utilized the department's skills and knowledge. Structural changes were made to expand their market presence abroad and increase export sales. As a result, export sales increased four-fold, area managers in new countries were added and distribution networks were successfully cultivated. At times, revenue generation was difficult to determine due to the structure of the company. Therefore, in 1996, the export division was restructured as a limited liability company. This allowed the company to improve the tracking of revenue and expenses. Originally, 80% of BTI's export sales came from two countries; therefore, the initial approach to selling overseas was not reaching their anticipated goals of expanding their foreign market presence. However, changes were made and now the company manages the details of selling to over 80 countries. There were three major export expansion challenges noted by the Managing Director: 1. Product and Shipping - The major obstacle for BTI was product assembly. Originally, the majority of the product was assembled in the United States, which increased shipping and packaging costs. With so many parts specified in the order, many times the order would arrive with parts missing. The missing parts could equate to tens of thousands of dollars. Shipping these missing parts separately in another shipment also cost tens of thousands of dollar, plus a delivery delay time of six to eight weeks; all of which came out of the BTI's pockets. 2. Product Adaptation - Safety and product standards varied widely for each of the 80 countries to which BTI exported. Weights, special licenses, product specification requirements, measurement systems, and truck stability can all differ from country to country and can serve as a type of barrier to entry, making it difficult to adapt products accordingly. Technical and safety standards are barriers that serve as a type of protection for the local industry and can stand in the way of successfully pursuing foreign markets. 3. Marketing Challenges - The importance of distribution creates many challenges for BTI as they attempt to determine how each country prefers to operate with regard to their distribution systems. Some countries have competition from a small competitor that only produces one competing product; whereas BTI manufactures over 100 products. Marketing material is another concern for BTI as they attempt to push marketing costs to the distributors. Adapting the marketing material can be costly in terms of translation and cultural differences. In addition, the size of paper in the United States differs from those in some countries, causing many problems when attempting to copy the same layout and With distribution being one of several challenges for BTI, the company claims their distribution network is one of their competitive advantages, as the location and names of their distributors are not revealed. In addition, BTI rotates two offerings yearly: training to their distributors one year and then the next is a distributor's meeting. With a focus on product and shipping, product adaptation, and marketing challenges, the intricacies of selling overseas takes time and patience. Another competitive advantage noted is BTI's cradle to grave strategy, where they follow the product from sale to its final resting place, whether the truck is leased or purchased new or used. They also offer service and maintenance plans with a detailed cost analysis provided to the company prior to purchasing or leasing the product. Expanding abroad will always create challenges for a company. As the Managing Director stated, "If you don't have patience (in the export business), you better do something else." Knowing how to adapt quickly provides BTI with the skills necessary to adjust to the changing needs of each country and its own unique challenges, allowing them to remain competitive.

• The Journal of the Acoustical Society of Korea
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• 제20권2E호
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• pp.30-45
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• 2001

This study considers the environmental factors affecting propagation loss and sonar performance in the continental regions of the East Coast Sea of Korea. Water mass distributions appear to change dramatically in a few weeks. Simple calculation with the case when the NKCW (North Korean Cold Water) develops shows that the difference in propagation loss may reach in the worst up to 10dB over range 5km. Another factor, an eddy, has typical dimensions of 100-200km in diameter and 150-200m in thickness. Employing a typical eddy and assuming frequency to be 100Hz, its effects on propagation loss appear to make lower the normal formation of convergence zones with which sonars are possible to detect long-range targets. The change of convergence zones may result in 10dB difference in received signals in a given depth. Thermal fronts also appear to be critical restrictions to operating sonars in shallow waters. Assuming frequency to be 200Hz, thermal fronts can make 10dB difference in propagation loss between with and without them over range 20km. An observation made in one site in the East Coast Sea of Korea reveals that internal waves may appear in near-inertial period and their spectra may exist in periods 2-17min. A simulation employing simple internal wave packets gives that they break convergence zones on the bottom, causing the performance degradation of FOM as much as 4dB in frequency 1kHz. An acoustic experiment, using fixed source and receiver at the same site, shows that the received signals fluctuate tremendously with time reaching up to 6.5dB in frequencies 1kHz or less. Ambient noises give negative effects directly on sonar performance. Measurements at some sites in the East Coast Sea of Korea suggest that the noise levels greatly fluctuate with time, for example noon and early morning, mainly due to ship traffics. The average difference in a day may reach 10dB in frequency 200Hz. Another experiment using an array of hydrophones gives that the spectrum levels of ambient noises are highly directional, their difference being as large as 10dB with vertical or horizontal angles. This fact strongly implies that we should obtain in-situ information of noise levels to estimate reasonable sonar performance. As one of non-stationary noise sources, an eel may give serious problems to sonar operation on or under the sea bottoms. Observed eel noises in a pier of water depth 14m appear to have duration time of about 0.4 seconds and frequency ranges of 0.2-2.8kHz. The 'song'of an eel increases ambient noise levels to average 2.16dB in the frequencies concerned, being large enough to degrade detection performance of the sonars on or below sediments. An experiment using hydrophones in water and sediment gives that sensitivity drops of 3-4dB are expected for the hydrophones laid in sediment at frequencies of 0.5-1.5kHz. The SNR difference between in water and in sediment, however, shows large fluctuations rather than stable patterns with the source-receiver ranges.

• Magazine of the Korean Society of Agricultural Engineers
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• 제19권1호
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• pp.4323-4337
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• 1977

The study was to estimate the effect of the rise of water temperature in the warm water pool and to make contribution to the establishment of reducing to a damage of cool water as well as to the planning for warm water pool. This observation was performed in Wudu warm water pool located at Wudu-Dong of Chuncheon for two years from 1975 to 1976. The results were showed as follows; 1. The daily variation of water temperature was the least for inset (No.1; 0.6$^{\circ}C$) the second for middle overflow (No2: 3$^{\circ}C$, No.3; 2.3$^{\circ}C$) and another for outflet (No.4; 3.6$^{\circ}C$, No.5; 3.8$^{\circ}C$) And the highest reaching time of water temperature in each block was later about 1 hour than the time at which air temperature happend in the daytime. So, the variation of water temperature was sensitive to the variation of air temperature 2. The monthly variation of water temperature at each measuring point was plotted to be increased with increase in air temperature till August (Mean monthly rising degree; No.1; 1.15$^{\circ}C$, No.2; 1.7$^{\circ}C$, No.3; 1.73$^{\circ}C$, No.4; 2.08$^{\circ}C$, No.5; 2.0$^{\circ}C$), and expressed gradually descended influence upon water temperature after August. 3. The mean temperature of inflow folwed in warm Water pool was 7.5∼12.5$^{\circ}C$, and outflow temperature was described as 13.4∼22.5$^{\circ}C$ to be climbed. And So, the rising interval of water temperature was shown as 6.7∼10.4$^{\circ}C$. 4. The correlation between the rising of water temperature and the weather condition was found out highly significant. As the result, their correlation coefficents of water temperature depending on mean air temperature, ground temperature, wind velocity and relative humidity were to be 0.93, 0.90, - 0.83 and 0.71 respectively. But there was no confrimation of the correlation on the clouds, sunlight time, volume of evaporation, and heat capacity of horizontal place. 5. The water temperature of balance during the period of rice growing in Chuncheon district was shown as table 10, and the mean of whole period was calculated as about 23.7$^{\circ}C$. 6. The observed value of the outflow temperature passed through the warm water pool was higher than that of computed, the mean difference between two value was marked as 1.15$^{\circ}C$ for blockl, 1.18$^{\circ}C$ for block2, and 0.47$^{\circ}C$ for block3, respectivly. Therefore, the ratio on the rising degree between the observed and computed were shown as 53%, 44%, and 18%, mean 38% through each block warm water pool (referring item $\circled9$ of table 11,12, and 13). Accordingly, formula (4) in order to fit for each block warm water pool was transfromed as follow; {{{{ { theta }_{w } - { theta }_{ 0} =[1-exp LEFT { { 1-(1+2 varphi )} over {cp } CDOT { A} over { q} RIGHT } ] TIMES ( { theta }_{w } - { theta }_{ 0}) TIMES C }}}} Here, correction coefficinent was computed 1.38, and being substituted 1.38 for C in preceding formula, the expected water temperature will be calculated to be able to irrigate the rice paddy. As the result, we can apply the coefficient in order to plan and to construct a new warm water pool.

• Korean journal of applied entomology
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• 제25권4호
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• pp.221-228
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• 1986

An empirical model to predict initial disease occurrence and subsequent progress of Alternaria leaf spot was constructed based on the modified degree day temperature and frequency of rainfall in three years field experiments. Climatic factors were analized 10-day bases, beginning April 20 to the end of August, and were used as variables for model construction. Cumulative degree portion (CDP) that is over $10^{\circ}C$ in the daily average temperature was used as a parameter to determine the relationship between temperature and initial disease occurrence. Around one hundred and sixty of CDP was needed to initiate disease incidence. This value was considered as temperature threshhold. After reaching 160 CDP, time of initial occurrence was determined by frequency of rainfall. At least four times of rainfall were necessary to be accumulated for initial occurrence of the disease after passing temperature threshhold. Disease progress after initial incidence generally followed the pattern of frequency of rainfall accumulated in those periods. Apparent infection rate (r) in the general differential equation dx/dt=xr(1-x) for individual epidemics when x is disease proportion and t is time, was a linear function of accumulation rate of rainfall frequency (Rc) and was able to be directly estimated based on the equation r=1.06Rc-0.11($R^2=0.993$). Disease severity (x) after t time could be predicted using exponential equation $[x/(1-x)]=[x_0/(1-x)]e^{(b_0+b_1R_c)t}$ derived from the differential equation, when $x_0$ is initial disease, $b_0\;and\;b_1$ are constants. There was a significant linear relationship between disease progress and cumulative number of air-borne conidia of Alternaria mali. When the cumulative number of air-borne conidia was used as an independent variable to predict disease severity, accuracy of prediction was poor with $R^2=0.3328$.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제31권1호
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• pp.71-76
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• 1998

To know the antibiotic specificity of a Dinoflagellate, Cochlodinium polykrikoides, we investigated the survival time of C. polykrikoides against several concentrations of antibiotics and judged the selective specificity of antibiotics based on the $LT_50$ ($50\%$ of lethal time). The result showed that C. polykrikoides was sensitive to tetracycline and chloramphenicol, and resistant to polymixin-B, ampicillin, penicillin-G, dihydrostreptomycin, and neomycin. In the case of sensitive antibiotics to C. polykrikoides, tetracycline and chloramphenicol, the safety concentrations of both antibiotics were determined and the antibiotic specificity based or the plotted survival curve was analyzed. Before antibiotic treatment, we tested the antibiotic susceptibility of the contaminated bacterial population in tile culture of C. polykrikoides, and decided the proper kinds of antibiotics and concentrations before percoll-centrifugation. By percoll-centrifugation, we reduced bacteria, removed fungi, collected the algal pellet, and made axonic culture by antibiotic cascade procedure based on the result of antibiotic susceptibility test. We observed that axonic C. polykrikoides culture entered the logarthmic phase of growth when cell density was over 740 cells/ml and propagated to 5,800 cells/ml maximally. Divisions per day, k value of C. polykrikoides represented a good index for growth at the low density of cells. There was a highest k value shift before reaching to the logarithmic phase. We suggested that the preceeding highest k value shift stage is a good indicator for accurate broadcasting for red. tide blooming in the field, and the stage is also a good time for controlling red tide blooming in the filed, either.