• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.12
• /
• pp.987-993
• /
• 2013

Korean Utility Helicopter(KUH) is the first korean-developed helicopter. Its first flight was performed in March 2010 and then its development was completed successfully by June 2012. During flight test phase, KUH faced various vibration problems and appropriate vibration-reduction devices were designed and applied to solve the problems. The vibration-reduction devices were applied to main rotor blades, main gear box(MGB) supporting structure, cockpit, cabin and pilot seats to reduce rotor-induced 4/rev vibration. Also, dome-fairing was introduced in order to reduce the tail-shake vibration. This paper shows design technique and flight test results for vibration-reduction devices that have been incorporated into KUH.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.1
• /
• pp.29-39
• /
• 2017

In this research, thermal design data such as heat transfer coefficient on the wall surface required for ventilation system design which is to prevent the temperature rise in the underground utility tunnel that three sides are adjoined with the ground was investigated in numerical analalysis. The numerical model has been devised including the tunnel lining of the underground utility tunnel in order to take account for the heat transfer in the tunnel walls. The air temperature in the tunnel, wall temperature, and the heating value through the wall based on heating value(117~468 kW/km) of the power cable installed in the tunnel and the wind speed in the tunnel(0.5~4.0 m/s) were calculated by CFD simulation. In addition, the wall heat transfer coefficient was computed from the results analysis, and the limit distance used to keep the air temperature in the tunnel stable was examined through the research. The convective heat transfer coefficient at the wall surface shows unstable pattern at the inlet area. However, it converges to a constant value beyond approximately 100 meter. The tunnel wall heat transfer coefficient is $3.1{\sim}9.16W/m^2^{\circ}C$ depending on the wind speed, and following is the dimensionless number:$Nu=1.081Re^{0.4927}({\mu}/{\mu}_w)^{0.14}$. This study has suggested the prediction model of temperature in the tunnel based on the thermal resistance analysis technique, and it is appraised that deviation can be used in the range of 3% estimation.

• Honam Mathematical Journal
• /
• v.36 no.3
• /
• pp.695-706
• /
• 2014

Various properties of digital covering spaces have been substantially used in studying digital homotopic properties of digital images. In particular, these are so related to the study of a digital fundamental group, a classification of digital images, an automorphism group of a digital covering space and so forth. The goal of the present paper, as a survey article, to speak out utility of digital covering theory. Besides, the present paper recalls that the papers [1, 4, 30] took their own approaches into the study of a digital fundamental group. For instance, they consider the digital fundamental group of the special digital image (X, 4), where X := $SC^{2,8}_4$ which is a simple closed 4-curve with eight elements in $Z^2$, as a group which is isomorphic to an infinite cyclic group such as (Z, +). In spite of this approach, they could not propose any digital topological tools to get the result. Namely, the papers [4, 30] consider a simple closed 4 or 8-curve to be a kind of simple closed curve from the viewpoint of a Hausdorff topological structure, i.e. a continuous analogue induced by an algebraic topological approach. However, in digital topology we need to develop a digital topological tool to calculate a digital fundamental group of a given digital space. Finally, the paper [9] firstly developed the notion of a digital covering space and further, the advanced and simplified version was proposed in [21]. Thus the present paper refers the history and the process of calculating a digital fundamental group by using various tools and some utilities of digital covering spaces. Furthermore, we deal with some parts of the preprint [11] which were not published in a journal (see Theorems 4.3 and 4.4). Finally, the paper suggests an efficient process of the calculation of digital fundamental groups of digital images.

• Proceedings of the Korean Institute of Interior Design Conference
• /
• 2007.05a
• /
• pp.210-215
• /
• 2007

In terms of cultural history, museum architecture represents culture of society in an era. exhibition space which represents the society and culture can't be fixed in the same way in a current mobile era. Especially, mobility of exhibition can be able to give audience even opportunities to enjoy. As a result, mobile exhibition space that functions as total space for everybody and the study of this issue is necessary. As mobile exhibition space is in the middle of development, there are many things to make up for the weak points. In order to make mobile exhibition space more competitive, development of new form and material is needed most. besides, limited development on interior plans which has been overlooked in terms of mobility is needed. Also, there should be more aggressive and powerful marketing and promotion for mobile exhibition space. To equalize the metropolitan area and local exhibition space and revitalize domestic exhibition space, the utility of mobile exhibition space which is movable and economic is highly expected more than previous fixed exhibition space.

• Journal of Internet Computing and Services
• /
• v.17 no.5
• /
• pp.51-58
• /
• 2016

The unprecedented power of cloud computing (CC) that enables free sharing of confidential data records for further analysis and mining has prompted various security threats. Thus, supreme cyberspace security and mitigation against adversaries attack during data mining became inevitable. So, privacy preserving data mining is emerged as a precise and efficient solution, where various algorithms are developed to anonymize the data to be mined. Despite the wide use of generalized K-anonymizing approach its protection and truthfulness potency remains limited to tiny output space with unacceptable utility loss. By combining L-diversity and (${\alpha}$,k)-anonymity, we proposed a hybrid K-anonymity data relocation algorithm to surmount such limitation. The data relocation being a tradeoff between trustfulness and utility acted as a control input parameter. The performance of each K-anonymity's iteration is measured for data relocation. Data rows are changed into small groups of indistinguishable tuples to create anonymizations of finer granularity with assured privacy standard. Experimental results demonstrated considerable utility enhancement for relatively small number of group relocations.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.2B no.3
• /
• pp.133-139
• /
• 2002

In this paper, a prototype of an active auxiliary quasi-resonant DC link (QRDCL) snubber assisted voltage source bidirectional power converter (AC to DC and DC to AC) operating at zero voltage soft-switching (BVS) PWM nlode is presented for a Battery Energy Storage System (BESS). The operating principle of this QRDCL circuit and multifunctional control-based converter system, including PWM inverter mode in which energy flows from the battery bank to the three-phase utility-grid in addition to an active PWM converter mode in which energy flows from the utility-grid to the battery banks are described respectively by the control implementation on the basis of d-q coordinate plane transformation. The multifunctional operation characteristics of this three-phase ZVS PWM bi-directional converter with QRDCL is demonstrated fer a BESS under the power conditioning and processing schemes of energy supply mode and energy storage mode, and compared with a conventional three-phase hard switching PWM bi-directional converter for a BESS. The effectiveness of the three-phase ZVS PWM hi-directional converter with QRDCL is proven via the simulation analysis.

• Proceedings of the KIEE Conference
• /
• 1995.07a
• /
• pp.440-442
• /
• 1995

In a recently as renewable energy source photovoltaic(PV) system using solar energy has been very widely researched because of its pollution-free and infinity. Especially many researches are intensively focused on small scale utility interactive PV system which can use dead space and easily make power stabilized from unstable natural energy source. In this system one of the most important matters is islanding protection. Islanding phenomenon appears when power failure occurs. For the safety of utility interactive PV system must has the function of not only system protection but also detection of islanding. This paper describes parallel operating alghorithm using reactive power variation method and twin peak band pass filter. This alghorithm is verified useful by simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.6
• /
• pp.1638-1658
• /
• 2024

As a crucial development direction for the sixth generation of mobile communication networks (6G), Low Earth Orbit (LEO) satellite networks exhibit characteristics such as low latency, seamless coverage, and high bandwidth. However, the frequent changes in the topology of LEO satellite networks complicate communication between satellites, and satellite power resources are limited. To fully utilize resources on satellites, it is essential to determine the association between satellites before power allocation. To effectively address the satellite association problem in LEO satellite networks, this paper proposes a satellite association-based resource allocation algorithm. The algorithm comprehensively considers the throughput of the satellite network and the fairness associated with satellite correlation. It formulates an objective function with logarithmic utility by taking the logarithm and summing the satellite channel capacities. This aims to maximize the sum of logarithmic utility while promoting the selection of fewer associated satellites for forwarding satellites, thereby enhancing the fairness of satellite association. The problems of satellite association and power allocation are solved under constraints on resources and transmission rates, maximizing the logarithmic utility function. The paper employs an improved Kuhn-Munkres (KM) algorithm to solve the satellite association problem and determine the correlation between satellites. Based on the satellite association results, the paper uses the Lagrangian dual method to solve the power allocation problem. Simulation results demonstrate that the proposed algorithm enhances the fairness of satellite association, optimizes resource utilization, and effectively improves the throughput of LEO satellite networks.

• Korean Institute of Interior Design Journal
• /
• no.21
• /
• pp.107-113
• /
• 1999

The purpose of this study is to suggest the materials for developing the new house style by analysing the space characteristics of wood frame houses in suburbs of Seoul. For this, we analysed 45 drawings(site plan, floor plan, elevation, section) that were designed by MICHOO, WOOD-LAND, STUGA and CHOWONJUTECK company etc. The space design characteristics that we found are as follows; 1. The wood is fragile to humidity. Therefore this characteristic is especially considered in designing the space of bathroom and utility room. 2. It is the merit of wood frame house that inner space can be designed variously by using spilt-level and the slope of roof. 3.The public space and private space are completely separated in most cases and the stair is located in the middle of house. This structure of house is short of horizontal openness. Instead, most houses gets vertical openness by making second floor on the living room opev. 4. In wood frame house as the rural house, the outer space is well used by setting up deck and balcony. The outer spaces like deck and balcony are usually used as a part of life space in connected with living room, dining room, master bed room and family room. 5. The public spaces like kitchen, living room, dining room and family room are considered so important in design that those are arranged in front in order to have good outlook and directiov.

• Journal of the Korean Institute of Rural Architecture
• /
• v.6 no.1
• /
• pp.42-53
• /
• 2004

The purpose of this study is to examine the space usage behaviors of dwelling by using field study method and by interviewing residents of apartment houses in rural areas. It has been found that the main occupancy space among the residents of apartment houses in rural area is based on agricultural activities. This study will show that apartment houses in rural areas must, as a necessity, reflect the characteristics and needs of its rural environment. It is certain that the existing "unit plan" is not a suitable method. Residents of rural areas have been able to adjust themselves to their current dwelling space properly. This is, mainly, due to economic factors. The interior space is used for simple everyday activities like loading, deposit and drying things. "Nongmak" is a space used for agricultural work and the balcony is used for storage of various things. In conclusion, this study strongly suggested that secure storage space based on the farmhouse model and rural lifestyle should be necessary. Furthermore, special designed cubic shelves should be placed in utility rooms and balconys. And the design and function of apartment houses in rural areas must reflect the needs of its residents.