• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.5
• /
• pp.323-334
• /
• 2020

Since boundary layer transition has a significant impact on the aero-thermodynamic performance of hypersonic flight vehicles, capability of accurate prediction of transition location is essential for design and performance analysis. In this study, γ-Re_θt model is improved to predict transition of hypersonic boundary layers and validated. A coefficient in the production term of the intermittency transport equation that affects the transition onset location is constructed and applied as a function of Mach number, wall temperature, and freestream stagnation temperature based on the similarity numerical solution of compressible boundary layer. To take into account a Mach number dependency of transition onset momentum thickness Reynolds number and transition length, additional correlation equations are determined as function of Mach number and applied to Re_θc and F_length correlations of the baseline model. The suggested model is implemented to a commercial CFD code in consideration of practical use. Analysis of hypersonic flat plate and circular cone boundary layers is carried out by using the model for validation purpose. An improvement of prediction capability with respect to variation of Mach number and unit Reynolds number is identified from the comparison with experimental data.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.5
• /
• pp.383-390
• /
• 2020

Wedge locks have been widely used for spaceborne electronics for mounting or removal of a printed circuit board (PCB) during integration, test and maintenance process. However, it can basically provide a mechanical constraint on the edge of the board. Thus, securing a fatigue life of solder joint for electronic package by limiting board deflection becomes difficult as the board size increases. Previously, additional stiffeners have been applied to reduce the board deflection, but the mass and volume increases of electronics are unavoidable. To overcome the aforementioned limitation, we proposed an application of multi-layered PCB sheet with viscoelastic adhesive tapes to implement high-damping capability on the board. Thus, it is more advantageous in securing the fatigue life of package under launch environment compared with the previous approach. The basic characteristics of the PCB with the multi-layered sheet was investigated through free-vibration tests at various temperatures. The effectiveness of the proposed design was validated through launch vibration test at qualification level and fatigue life prediction of electronic package based on the test results.

• Journal of Broadcast Engineering
• /
• v.25 no.2
• /
• pp.265-274
• /
• 2020

Free-viewpoint video service is a technology that allows users to watch at any angle, location and distance through interaction. In this paper, the free-viewpoint video services are defined in four viewing modes: Inward view, outward view, 3D object view and first person view. And we developed and implemented a new integrated program that plays all the suggested views. In the contents of girl band performances and basketball games, multi-view cameras suitable for each viewing mode are installed to acquire media, and data stored on the server is streamed over the network, making it available for viewing. Users can freely choose four viewing modes, space location, angle and so on, and the media data such as images and sounds are provided to them by rendering appropriately for the selected the viewpoint. Our system is expected to be a scalable free-viewpoint video service player as well as provide users with immersion and presence by combining various viewing modes.

• Journal of Bio-Environment Control
• /
• v.25 no.2
• /
• pp.123-132
• /
• 2016

The importance of energy saving technology for managing greenhouse was recently highlighted. For practical use of energy in greenhouse, it is necessary to simulate energy flow precisely and estimate heating/cooling loads of greenhouse. So the main purpose of this study was to develope and to validate greenhouse energy model and to estimate annual/maximum energy loads using Building Energy Simulation (BES). Field experiments were carried out in a multi-span plastic-film greenhouse in Jeju Island ($33.2^{\circ}N$, $126.3^{\circ}E$) for 2 months. To develop energy model of the greenhouse, a set of sensors was used to measure the greenhouse microclimate such as air temperature, humidity, leaf temperature, solar radiation, carbon dioxide concentration and so on. Moreover, characteristic length of plant leaf, leaf area index and diffuse non-interceptance were utilized to calculate sensible and latent heat exchange of plant. The internal temperature of greenhouse was compared to validate the greenhouse energy model. Developed model provided a good estimation for the internal temperature throughout the experiments period (coefficients of determination > 0.85, index of agreement > 0.92). After the model validation, we used last 10 years weather data to calculate energy loads of greenhouse according to growth stage of greenhouse crop. The tendency of heating/cooling loads change was depends on external weather condition and optimal temperature for growing crops at each stage. In addition, maximum heating/cooling loads of reference greenhouse were estimated to 644,014 and $756,456kJ{\cdot}hr^{-1}$, respectively.

• Journal of Bio-Environment Control
• /
• v.20 no.3
• /
• pp.169-175
• /
• 2011

The adaptive neuro-fuzzy inference system (ANFIS) based automatic control system framework was proposed for integrated environment management of ubiquitous plant factory which can collect information of crop cultivation environment and monitor it in real-time by using various environment sensors. Installed wireless sensor nodes, based on the sensor network, collect the growing condition's information such as temperature, humidity, $CO_2$, and the control system is to monitor the control devices by using ANFIS. The proposed automatic control system provides that users can control all equipments installed on the plant factory directly or remotely and the equipments can be controlled automatically when the measured values such as temperature, humidity, $CO_2$, and illuminance deviated from the decent criteria. In addition, the better quality of the agricultural products can be gained through the proposed automatic control system for plant factory.

• Journal of Educational Research in Mathematics
• /
• v.27 no.3
• /
• pp.411-430
• /
• 2017

This study examined the understanding of 24 pre-service teachers about the three contexts for constructing the exponential graphs. The three contexts consisted of the infinite points context (2009 revision curriculum textbook method), the infinite straight lines context (French textbook method), and the continuous compounding context (2015 revision curriculum textbook method). As the result of the examination, most of the pre-service teachers selected the infinite points context as easier context for introducing the exponential graph. They noted that it was the appropriate method because they thought their students would easily understand, but they showed the most errors in the graph presentation of this method. These errors are interpreted as a lack of content knowledge. In addition, a number of pre-service teachers noted that the infinite straight lines context and continuous compounding context were not appropriate because these contexts can aggravate students' difficulty in understanding. What they pointed out was interpreted in terms of knowledge of content and students, but at the same time those things revealed a lack of content knowledge for understanding the continuous compounding context. In fact, considering the curriculum they have experienced, they were not familiar with this context, continuous compounding. These results suggest that pre-service teacher education should be improved. Finally, some of the pre-service teachers mentioned that using technology can help the students' difficulties because they considered the design of visual model.

• Journal of Fashion Business
• /
• v.7 no.1
• /
• pp.38-54
• /
• 2003

This study looked into the present status of e-mail marketing, which is conducted in local Internet fashion shopping malls and is being used as a one-to-one marketing method in the e-CRM concept so as to establish an effective e-mail marketing policy by grasping problems based on the current status and by presenting solutions to the problems. This study analyzed the e-mail letters received during a certain period of time by 30 professional Internet fashion shopping malls of with famous goods, brands and non-brands. Four individuals subscribed to shopping mall through the procedure for membership applying for e-mail services. The analysis showed that there were no shopping malls that were doing a differentiated e-mail marketing among Internet shopping malls. As for time factor, they were sending e-mail letters irregularly regardless of a certain cycle. And as for visual factor, they didnt have any standard for the content of the mail. As for content factor, the contents of their mail were not differentiated and all the same. The comparison of fashion malls showed that the brand shopping malls were the most active in e-mail marketing. On the basis of the problems, the direction for the effective e-mail marketing of Internet shopping malls are presented as follows: First, individualized contents fitting for customers should be developed, and differentiated mailing services should be provided thereby. Second, each shopping mall should make periodic tests of mailing to find out the optimal time and day to provide e-mail services to the customers at the designated time. Third, e-mail should be differentiated fitting for the website according to a certain on a certain standard for visual effects and the identity of shopping mall should be established. Firth, in the contents of e-mail, the image and message elements should be properly harmonized and creative policies should be made with interactive or recreational elements. Fifth, a homepage policy which can satisfy customers demand for information when the e-mail is clicked on..

• Journal of Fashion Business
• /
• v.2 no.1
• /
• pp.71-75
• /
• 1998

The Miaos who is the minority people mainly living in the southwestern part of China, expressed their indicator and solidarity through the costume in order to maintain their racial character while experiencing numerous adversities over thousands of years, where the costume has served as a source of cohesion as well as a primitive religious thought, and also showed their faith, desire, longing and aspiration. This study examined the Miao's traditional costume by classifying it into the following; hair style, headdress, upper and lower garments, and other costume. And the silver ornaments used for attire and their symbolic meaning were examined. The result of the study is summarized as follows. 1. The reason that types of the costume has been diversified is because there was promise of ancestors who intended to differently express the type of a kind as symbol of the racial branch that is the Miao's special type of society. Thus, the costume type could tell where a tribe live. Another reason is because only marriage between families with different surname but the same type of costume was accepted. 2. As women made and wore the costume themselves, it also served as a means of being proud of their skill or wealth, they tried to make it more beautiful and it was also used as a token of marriage or love between relatively enlightened men and women. 3. The design used on the costume was expressed as a symbolic meaning of indicator to strengthen the racial solidarity because it connoted worship to ancestors who had experienced lots of adversities. 4. The hair style was expressed in various styles by using Kache such as Chukye, Byunbal and Kokye. It is likely that ornaments used on the head of women in the form of cow's horn or silver crown were used as one of the methods to stress the valuableness of the cattle that were essential to agricultural life. In addition, various styles of turbans were used to indicate the respective regions. 5. Cock's feather ornaments or silver ornaments in the form of pheasant's feather on the edge of women's skirts, peasant's feathers that men wore on their head, or Baekjoui and men wore resulted from the Miaos' thought of adoration for birds, which implied a primitive religious meaning. 6. As the region where the Miaos live yields much silver, the silver ornaments were mostly used to be proud of wealth, which symbolized light and pureness.

• Journal of Fashion Business
• /
• v.13 no.1
• /
• pp.152-166
• /
• 2009

By virtue of the development of mass media, the cinema, the composite space art taking the visual and auditory elements together, exhibits the actual life of the realities, thereby having a mutually close relationship to social, cultural and economic fields and continuing to generate the fashion code as well as reflecting the image of the times. Especially, fashion style in movies delivers their image and atmosphere and becomes the means for containing the personality, spiritual world and inner thinking of the characters in the movie and inducing its plot. Therefore, this study was intended to make clear that fashion fuses and shares with a diversity of genres such as movies and the like, becomes the cultural model that proceeds to create a new culture in relation to daily life and induces and presents the trend of contemporary fashion. For this purpose, this study attempted to analyze fashion style in the movie. Lolita is the fiction published by the Russian?American writer Vladimir Nabokov($1899{\sim}1977$) in 1954. It is the fiction that portrays the unethical love between Humbert, a middleaged man, and Lolita, a girl in her 10s. It was cinematized by the director Stanley Kubrick for the first time in 1962 and revived by the movie director Adrian Lyne in 1997. The character of Lolita has a younger look like a girl and looks immature in the movie directed by the movie director Stanley Kubrick and the movie director Adrian Lyne. But the character of Lolita has the commonality that she showed an incomplete female image of having a sexually freewheeling thinking. Thereby, this study sought to prove that the created fashion style of the character in the film not only became the clue to enable us to know the time and space background in the film but also helped the film develop effectively by performing a role of portraying the character in the movie. And it attempted to present that it becomes both the foundation for leading the fashion trend shown in contemporary fashion and the code of mass culture. Fashion style of Lolita in the movie appears to be reflected diversely in mass culture as well as fashion style in the contemporary times.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.36 no.3
• /
• pp.157-165
• /
• 2000

A small hydraulic winch system with an automatic tension control unit was designed to improve the work efficiency of coastal small vessels and the dynamic response characteristics of the winch system operated in the open loop condition was investigated. The inlet and the outlet pressures in hydraulic motor, the torque and the rotating speed of winch drum were measured as a function of time, and the behaviour in autotension mode for stepped load changes was analyzed. The results obtained are summarized as follows : 1. The developed winch system for coastal small vessels will result in better fishing with improved efficiency and lower manpower consumption by remote control of winch system. 2. The rotating delay times of winch drum for on/off operations of solenoid valve were 0.09 see at CW mode and 0.04 sec at CCW mode, respectively. After the solenoid valve was controlled, response characteristics were unstable slightly but showed good tracking behaviour over short time. 3. The driving torque of winch system in autotension mode was kept almost constant of 55.9 kgf·m, and 11.1 then the rotating speed of winch drum was kept almost constant of 5.1 rpm in the larger torque than 55.9 kgf·m and 11.1 rpm in the lower torque than that. 4. The 5% settling times in the transient response characteristics of autotension mode under rapid increasing and decreasing conditions of load were 0.12 sec and 0.2 sec, respectively, and then the rotating speeds were 11 rpm and 5.3 rpm, respectively. 5. The tracking behaviour of torque and rotating speed by remote control operation were stable within 0.23 sec at CW mode and 0.37 sec at CCW mode, respectively.