• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.6
• /
• pp.704-711
• /
• 2023

This paper discusses the control method of BLDC(Brushless Direct Current) motor that has similar electrical characteristics with DC motor but has improved its lifespan and reliability. The BLDC motor can improve durability and speed stability by using rotor position information to eliminate commutators that require mechanical contact with DC motors. In this study, a controller for a DC motor was designed based on the fact that the current in the windings of a BLDC motor is a square-wave current like the current flowing in the armature of a DC motor. Next, the designed controller was applied to a 3-phase BLDC motor to confirm the effectiveness of the controller. In detail, a single-phase DC motor with electrical parameter values of a three-phase BLDC motor was modeled and a PI controller for motor speed control was designed by applying the root locus method to the derived system. The speed control simulation of the DC motor was performed to confirm the validity of the controller, and the same controller was applied to the speed control of the 3-phase BLDC motor implemented in MATLAB. From the simulation, similar results of the DC motor were obtained in the 3 phase BLDC motor and confirmed the usefulness of the proposed control scheme.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.18 no.2
• /
• pp.67-79
• /
• 2023

The bounce rate is the rate at which a user leaves immediately after visiting, and this study aimed to find out what attributes of a website affect the bounce rate. Web site evaluation items were defined as a total of 4 items and 27 evaluation attributes, including usability, information, service interaction, and technology, so that they can be commonly applied to venture companies in various industries through prior research. As a result of the study, 6 website attributes that affect the bounce rate were verified to be significant by discriminant analysis and decision tree analysis. Suggestions to reduce the bounce rate of venture business websites through this study are as follows. First, the path name of the website is displayed as mandatory and a pull-down menu function is added to facilitate movement to other pages. Second, it is good to expose core content that can attract users' attention in the form of a banner, and place internal link banners in the right place on sub-pages. Third, external links should be linked to a new window so that they do not leave the current page immediately so that they can be re-entered. Lastly, it is recommended to expose the contact information of the person in charge and consultation function as direct information for communication with customers, but if individual response is difficult, at least the consultation function must be added. These suggestions are expected to be of practical help in various fields such as website development, operation, and marketing. However, in special cases, a high bounce rate may be normal, so it should be considered according to the situation.

• Journal of the Korean Geotechnical Society
• /
• v.40 no.1
• /
• pp.5-14
• /
• 2024

PHC piles demonstrate superior resistance to compression and bending moments, and their factory-based production enhances quality assurance and management processes. Despite these advantages that have resulted in widespread use in civil engineering and construction projects, the design process frequently relies on empirical formulas or N-values to estimate the soil-pile friction, which is crucial for bearing capacity, and this reliance underscores a significant lack of experimental validation. In addition, environmental factors, e.g., the pH levels in groundwater and the effects of seawater, are commonly not considered. Thus, this study investigates the influence of vibrating machine foundations on PHC pile models in consideration of the effects of varying pH conditions. Concrete model piles were subjected to a one-month conditioning period in different pH environments (acidic, neutral, and alkaline) and under the influence of seawater. Subsequent repeated direct shear tests were performed on the pile-soil interface, and the disturbed state concept was employed to derive parameters that effectively quantify the dynamic behavior of this interface. The results revealed a descending order of shear stress in neutral, acidic, and alkaline conditions, with the pH-influenced samples exhibiting a more pronounced reduction in shear stress than those affected by seawater.

• Journal of the Korean Wood Science and Technology
• /
• v.52 no.3
• /
• pp.221-233
• /
• 2024

Lignin, a prominent constituent of woody biomass, is abundant in nature, cost-effective, and contains various functional groups, including hydroxyl groups. Owing to these characteristics, they have the potential to replace petroleum-based polyols in the polyurethane industry, offering a solution to environmental problems linked to resource depletion and CO₂ emissions. However, the structural complexity and low reactivity of lignin present challenges for its direct application in polyurethane materials. In this study, Kraft lignin (KL), a representative technical lignin, was fractionated with ethanol, an eco-friendly solvent, and mixed with conventional polyols in varying proportions to produce polyurethane films. The results of ethanol fractionation showed that the polydispersity of ethanol-soluble lignin (ESL) decreased from 3.71 to 2.72 and the hydroxyl content of ESL increased from 4.20 mmol/g to 5.49 mmol/g. Consequently, the polyurethane prepared by adding ESL was superior to the KL-based film, exhibiting improved miscibility with petrochemical-based polyols and reactivity with isocyanate groups. Consequently, the films using ESL as the polyol exhibited reduced shrinkage and a more uniform structure. Optical microscope and scanning electron microscope observations confirmed that lignin aggregation was lower in polyurethane with ESL than in that with KL. When the hydrophobicity of the samples was measured using the water contact angle, the addition of ESL resulted in higher hydrophobicity. In addition, as the amount of ESL added increased, an increase of 7.4% in the residual char was observed, and a 4.04% increase in Tmax the thermal stability of the produced polyurethane was effectively improved.

• Korean Journal of Environmental Biology
• /
• v.41 no.4
• /
• pp.463-472
• /
• 2023

The insecticidal activities of 27 different commercial products with environmentally friendly organic material(EFOM) against Scotinophara lurida, a major rice pest, were evaluated in the laboratory using spraying methods on plants and insects. Seven plant-derived organic farming materials (EFOM-8, -10, -12, -13, -19, -20, and -26) with high insecticidal effects when sprayed directly on the insect's body rather than on the plant were selected. In the indoor rice pot test, all 7 EFOMs showed an insecticidal rate of over 73.3% under flooding conditions. Notably, EFOM-13 and EFOM-20 demonstrated much higher insecticidal rates, ranging from 1.5 to 1.8 times, in flooding conditions compared to drained conditions. In the semi-paddy field test, EFOM-10 (80% garlic extract), EFOM-13 (62% neem extract), and EFOM-26 (70% sophora extract+28% ethyl alcohol+2% pyrethrum extract) exhibited a higher control value of 88.9% in the irrigated paddy on the 7th day, surpassing the control values in the drained paddy by 1.4 to 1.9 times. The control value in the irrigated rice paddy field sprayed with EFOM-10 reached 86.2% on the 7th day, which was 1.4 times higher than 61.9% in the drained paddy. Taken together, the findings suggest that direct contact of the insect's body with sufficient amounts of spray solution and the maintenance of paddy irrigation can enhance the controlling effect of EFOMs. These findings will be valuable in developing an optimal S. lurida control strategy for application in rice paddy fields in the near future.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.13
• /
• pp.869-895
• /
• 2000

The US supports the Information and Communication (IC) industry as a strategic one to wield a complete power over the World Market. However, several other countries are also eager to have the support for the IC industry because the industry produces a high added value and has a significant effect on other industries. Korea is not an exception. Korea recently succeeded in the commercialization of CDMA for the first time in the world, after the successful development of TDX. Hence, it is highly likely to get tracked by the US. Although the IC industry is a specific sector of IT, there is a concern that there might be a trade friction between the US and Korea due to a possible competition. It will be very important to prepare a solution in advance so that Korea could prevent the friction and at the same time increase its share domestically and globally. It will be our important task to solve the problem with the minimum cost if the conflict arises unfortunately in the IT area. The parties that have a strong influence on the US trade policy are the think tank group and the IT-related interest group. Therefore, it would be important to have a close relationship with them. We found some implications by analyzing the case of Japan, which has experienced trade frictions with the US over the long period of time in the high tech industry. In order to get rid of those conflicts with the US, the Japanese did the following things : (1) The Japanese government developed supporting theories and also resorted to international support so that the world could support the Japanese theories. (2) Through continual dialogue with the US business people, the Japanese business people sought after solutions to share profits among the Japanese and the US both in the domestic and in the worldwide markets. They focused on lobbying activities to influence the US public opinion to support the Japanese. The specific implementation plan was first to open culture lobby toward opinion leaders who were leaders about the US opinion. The institution, Japan Society, were formed to deliver a high quality lobbying activities. The second plan is economic lobby. They have established Japanese Economic Institute at Washington. They provide information about Japan regularly or irregularly to the US government, research institution, universities, etc., that are interested in Japan. The main objective behind these activities though is to advertise the validity of Japanese policy. Japanese top executives, practical interest groups on international trade, are trying to justify their position by direct contact with the US policy makers. The third one is political lobby. Japan is very careful about this political lobby. It is doing its best not to give impression that Japan is trying to shape the US policy making. It is collecting a vast amount of information to make a correct judgment on situation. It is not tilted toward one political party or the other, and is rather developing a long-term network of people who understand and support the Japanese policy. The following implications were drawn from the experience of Japan. First, the Korean government should develop a long-term plan and execute it to improve the Korean image perceived by American people. Second, the Korean government should begin public relation activities toward the US elite group. It is inevitable to make an effort to advertise Korea to this elite group because this group leads public opinion in the USA. Third, the Korean government needs the development of a relevant policy to elevate the positive atmosphere for advertising toward the US. For example, we need information about to whom and how to about lobbying activities, personnel network who immediately respond to wrong articles about Korea in the US press, and lastly the most recent data bank of Korean support group inside the USA. Fourth, the Korean government should create an atmosphere to facilitate the advertising toward the US. Examples include provision of incentives in tax on the expenses for the advertising toward the US and provision of rewards to those who significantly contribute to the advertising activities. Fifth, the Korean government should perform the role of a bridge between Korean and the US business people. Sixth, the government should promptly analyze the policy of IT industry, a strategic area, and timely distribute information to industries in Korea. Since the Korean government is the only institution that has formal contact with the US government, it is highly likely to provide information of a high quality. The followings are some implications for business institutions. First, Korean business organization should carefully analyze and observe the business policy and managerial conditions of US companies. It is very important to do so because all the trade frictions arise at the business level. Second, it is also very important that the top management of Korean firms contact the opinion leaders of the US. Third, it is critically needed that Korean business people sent to the USA do their part for PR activities. Fourth, it is very important to advertise to American employees in Korean companies. If we cannot convince our American employees, it would be a lot harder to convince regular American. Therefore, it is very important to make the American employees the support group for Korean ways. Fifth, it should try to get much information as early as possible about the US firms policy in the IT area. It should give an enormous effort on early collection of information because by doing so it has more time to respond. Sixth, it should research on the PR cases of foreign enterprise or non-American companies inside the USA. The research needs to identify the success factors and the failure factors. Finally, the business firm will get more valuable information if it analyzes and responds to, according to each medium.

• Journal of the Korean Society of Costume
• /
• v.16
• /
• pp.15-42
• /
• 1991

A nation's culture isn't consisted by the characteristics of the nation only, but it is greatly affected by the geographical features and natural conditions, and it could be also dominated by the continual effect through mutual contact on economic exchange or social problem and political interests with neighboring countries. It is a well known fact that the contact of culture between Korea and Mongolia established under the special political situation that Corea was invaded by Won. But more basically, the Nomad including Mongolia had influenced upon neighboring countries, therefore, our country was also greatly influenced on consisting of our own culture by them. Moreover. the fact that our language belongs to their language's category(mostly Tweigru and Mongolian language) proves that the origin of our culture was deeply related with Mongolia. Accordingly, we could not limit the cultural relation between Korea and Mongolia within a special era. But especially, since unification of China by Mongolia, Won which appeared as a new great nation had dominated Corea for one hundred years, and the Corea's costume culture had a point of conversion to the mongolian. Therefore, this study expects to comment upon the relations of costume between Corea and Mongolia from a view point of Corea's tribute and royal gifts gifts by Mongolia written on the reference literatures. 1) From the ancient times, between our country and Mongolia there has been a direct or indirect exchange caused by the people's movement or invasion due to very closed neighboring. The relations between Corea and Mongolia have started from the mongolia's requests of tribute for the reason why they helped Corea against the Keoran's invasion, and these relation had continued by King Kongmin's age. 2) Mongolia had plundered a tribute such as dress, cereals, horses, military supplies, soldiers, maiden and little girls etc. from Corea, and therefore, a great confusion occurred on political, economic and social fields. And since King Chungyoul of Corea got married with a Princess of Won, the Corea's position was placed as the Buma nation(nation of son in law) and then high class people of Corea preferred to follow the mongolian costume such as Byunbal (pigtail), Ho dress (mongolian dress), Rouges, Chockturi (a kind of formal cap) and Doturak pigtail ribbon, and some have been applied up to date. On the other hand, the custom of Corea had transmitted to the Mongolian nobility, they called it "Corea Yang(style)". 3) The costume of Corea could be divided into three different periods, the first is the period influenced by Tang and Song's regime, the second is affected by the Won's costume and the third is applying the Myung's regime in the end of Corea. The Mongolian dress was based on the Ho dress form and it has been developed through compounding artistic traditional fields and foreign customs in long history. And Mongolia is composed of various tribes, therefore, they have their own dress for each tribe. Our country and Mongolia had a similar dress form based on Ho dress and both used the Chacksukunggo (jacket with small sleeves and slacks) and Seon(line). And the ornaments of costume such as Chockturi, Doturak pigtail ribbon and Rouges had transmitted and fixed down as a traditional wedding garment, but the Rouges has been used by noble women from the ancient times in our country. Since a member of the Society of Korean Costume has visited Mongolia in August 1990 for the first time, I really recognized the neccesity of more detailed study on the costume relation between Korea and Mongolia, and I will proceed with the study on various fields of costume under cooperation of Institute of Oriental Academy of Mongolia.

• The Korean Journal of Pesticide Science
• /
• v.13 no.1
• /
• pp.39-44
• /
• 2009

This study was conducted to evaluate the actual risk of fipronil on worker honey bees (Apis mellifera L.) through acute contact toxicity test, acute oral toxicity test, toxicity of residues on foliage test, and small scale field test. The $48h-LD_{50s}$ of fipronil SC on honeybee were $0.005{\mu}g$ a.i./bee in acute contact toxicity test and $0.004{\mu}g$ a.i./bee in acute oral toxicity test, respectively. In toxicity of residues on foliage test, fipronil showed over 90% of mortality during 28days after treatment at recommended application rate. The $DT_{50}$ of dislodgeable foliar residue was 9 days. Finally, In small scale field test, fipronil showed similar toxicity in the residues on foliage test. It was concluded that fipronil has very high acute toxicity and long residual toxicity to honeybee. Therefore, fipronil is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area. To protect honeybee and wild pollinators from outdoor use of fipronil, ultimately it should need to limit for only indoor use to prevent pollinators from unintentionally exposure of fipronil.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.6
• /
• pp.529-532
• /
• 2000

To establish a food safety of dried layer, heat treatment effect on the bacterial density of dried layers was investigated. And a modified process developing experiment for dried layer products using closing type drying oven was carried out. tittle bacterial density difference on the dried layer products were found before and after heat treatment at $90^{\circ}C$ for 6 hrs called Hwaip treatment having been used for long term storage. Direct or indirect heat treatment of dried lavers using gas burner and frying pan reduced about 1 to 3 log cycle of viable cell count from $10^8\;CFU/g\;to\;10^5\;CFU/g$. Heat treatment by direct surface contact type cooking machine being used in the market place for cooked dried layer products could reduce the viable cell count on the layer product from $2.2{\times}10^5{\~}5.2{\times}10^7\;CFU/g\;to\;7.0{\times}10^2{\~}5.0{\times}10^5\;CFU/g$, Ultraviolet irradiation (20 W, 30 cm) to one or both side of the dried laver products reduced the viable cell count from $2.2{\times}10^6\;CFU/g\;to\;8.0{\times}10^5\;CFU/g\;and\;2.0{\times}10^5\;CFU/g$, respectively. The viable cell count of the dried layer products produced by modified process using a closing type dryer was about $10^3\;CFU/g$ and lower 3 log cycle than that in the products collected in market place and made by open type dryer.

• Journal of Korean Academy of Nursing
• /
• v.24 no.2
• /
• pp.264-277
• /
• 1994

In Korea the concept of social support was first used as a research concept in nursing and has not had much application in the clinical field. Another problem is that research on social support has used a direct translation of the words “social support” into Korean as “sawhejuk jiji”. Three questions were posed to direct the re-search. 1) Is there a concept of social support in Korean society? 2) if so, what words or expressions are used to de-scribe it? 3) further, if so, how is social support structured and how does it function? In order to answer the research questions a three-step research methodology was used : The first step consisted of a literature review on re-search related to social support and on information on the background of, and the way of thinking re-lated to interpersonal relations among Korean people. The second step, which was done to identify whether there is a concept of social support in korean society, involved interviewing a sample of the population. The third step involved a panel discussion that included the members of the research team and three consultants, a sociologist, a philosopher and a scholor in korean literature. A review of the literature on interpersonal relationships in traditional korean society identified a four cirole structure that explains interpersonal relationships. The first circle with “me” at the center is the family but here “me” disappears into the “we” that is essential for a cooperative agricultural society. In the second circle are those close to “me” but outside the family. The third circle includes those with whom “I ” have infrequent but regular contact and with whom correct conduct is important. The last circle is all the people with whom “I” have nothing in common. They are excluded in interpersonal relationships. The literature on interpersonal relationships showed that within the traditional Korean society people lived in villages where most people were very familiar with each other. “Yun”, the social network established the connection and “Jung”, the feeling of affection increased with time as the connection was strengthened. In the traditional village psychological support was provided through “Mallaniki”, “Pumashi” and “Kae” with the latter two also providing material support. In modern Korea there are more informal and formal social networks, like social services and community activities on the formal level and cultural and leisure groups along with “kae’s on the informal level. But even with this modern variety of groups, most social support comes from informal networks that resemble the traditiorlal “Pumashi”, “Kai” md “Mallaniki”. The six member research team interviewed 65 people in order to identify whether there is a concept of social support and then analysed their responses. There were 20 different words describing the reception of the social support and these could be grouped into seven major categories : virtuous, fortunate, helped, supported, blessed, attached(receiving affection) and receiving (grace) benevolence. there were 27 words describing the act of social support which could be categorized into seven major categories : love, looking after, affection(attachment), kindness(goodness), faith, psychological help and material help. for the meaning of social support translated as “sawhe juk jiji” there were a total of 14 different answers which could be categorized into 3 major categories : help, agreement, and faith. In third step, the results of the literature review and the answers to the questions were discussed in a pannel. The results of the discussion led to the following definition of social support in Korea which is shaped like a the four sided pyramid on a base. Social support is the apex of the pyramid and four sides are made up of : “do-oom” (both emotional and material help), “jung” (connectedness, or relationship bound by affection, regard or shared common experience ), “midum” (faith or belief in), “eunhae” (kindness or benevolence). The research team identified “Yun”( the basic network of relationships) as the base of the pyramid and as such the foundation for the components of social support in Korean culture. On “Yun” rest the other four components of social support : “Jung”, “Midum”, “Do-oom”, and “Eunhae”, For social support to take place there must be “Yun”. This is an important factor in social support. In private social network “Jung” is an essential factor in social support. But not in the public social network. “Yun” is a condition for “Jung” and “Jung” is the manifestation of support.