• Journal of the Korean Solar Energy Society
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• 제34권3호
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• pp.82-88
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• 2014

Using low outdoor temperature, free cooling system is used in a data center or industrial air-conditioning for energy saving. Because use of IT equipment has increased in some office building recently, there is a growing trend towards using free cooing system. Free cooling system performance is influenced by outdoor temperature. Therefore the performance is different with regions. In this study, performance characteristic of free cooling system is analysed and energy reduction is compared with some regions. Selected regions are 4 cities; including Ulsan analyzed in preceding research, Seoul, ChunCheon and Daejeon. The Aspentech software HYSYS 8.0v was used to conduct the analysis of free cooling system based on temperature per hour of 4 cities in 2013, respectively. The main result is following as. Free cooing system in this study has energy saving effect when outdoor temperature below $7^{\circ}C$. Becuase temperature of Chuncheon is relatively low, using free cooling system can conserve most air-conditioning energy. Energy reduction amount of Seoul is 11%, Chuncheon is 17.5%, Deajeon is 15%, Ulsan is 14%. In case of large scale of air-conditioning, it is reasonable to use free cooling system although the system is used in Seoul.

• The KIPS Transactions:PartA
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• 제12A권6호
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• pp.493-498
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• 2005

P2P service is a method that can share various information through direct connection between computer of a person who have information and a Person who have information without server in the Internet and it is getting a lot of popularity by method for free ex change of file. P2P file sharing systems have become popular as a new paradigm for information exchange. Because all users who use service in P2P file sharing system can use shared files of several users freely by equal access privilege, it is happening the 'free rider' that only download shared file of other users without share own files. Although a user share a malicious file including virus, worm or file that have title differing with actuality contents, can use file sharing service without limitation. In this paper, we propose a method that restrict access of 'free rider' that only download using reputation information that indicate reliability of user. Also, we restrict usage ons hared file of other users about users who share harmful file.

• Journal of Korea Multimedia Society
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• 제12권5호
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• pp.717-727
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• 2009

P2P (Peer-to-Peer) network depends on cooperation of peers considerably. However, some peers do not share files at all and only download files. Peers also share low quality files or unpopular files. These selfish behavior of peers is referred to 'free riding'. The free riding of peer may decrease participation of other peers or the system performance. In this paper, we propose an incentive mechanism, called IcMFS (Incentive Mechanism for File Sharing System), which provides the correct use of incentive mechanism using trust peer, computes contribution values referring behavior of peers and rewards peers. The proposed mechanism assigns bandwidth and TTL(Time-To-Live) to a peer and differentiates the use of service. A case study on simulations shows the service differentiation according to the contribution value of peer, the correct use of incentive mechanism using trust peer and the advantage by use of trust peer. To prove the stability of proposed mechanism, we also show the disadvantage that a peer receives from the incorrect use of incentive mechanism.

• Smart Structures and Systems
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• 제15권5호
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• pp.1203-1214
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• 2015

This paper deals with the experimental validation of the use of PVDF Patches for the assessment of spatial derivatives of displacement field. It focuses more exactly on the shear Force Identification by using Specific forms of PVDF patcHes (FISH) on beams. An overview of the theoretical approach is exposed. The principle is based on the use of the weak form of the equation of motion of the beam which allows the shear forces to be extracted at one edge of the sensor when this last has a specific form. The experimental validation is carried out with a cantilever steel beam, excited by a shaker at its free boundary. The validation consists in comparing the shear force measured by the designed sensor glued at the free edge and the directly measured force applied by the shaker. The sensor is made of two patches, called the "stiffness" patch and the "mass" patch. The use of both patches allows one to identify correctly the shear force on a large frequency domain. The use of only the stiffness patch is valid in the low frequency domain and has the advantage to have a frequency-independent gain that allows its use in real time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.241-244
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• 2010

This paper investigates mainly the new free mandrel technology of the metal spinning. Although the classical spinning, so called conventional, shear, tube spinning, uses the axisymmetric shaped mandrel(which is same inner shape of the final product), new technology does not use it.

• Journal of the Korean institute of surface engineering
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• 제32권3호
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• pp.211-213
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• 1999

In the future, restrictions are likely to be imposed on the use of lead in the electronics industry. In dealing with such a move, we have been developing Pb-free Sn-Ag plating process to replace presently available Sn-Pb process. In this paper, the result of a basic comparison test between Sn-Pb plating and Sn-Ag plating is reported.

• Archives of Plastic Surgery
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• 제50권3호
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• pp.264-273
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• 2023

The medial sural artery perforator (MSAP) flap is a versatile fasciocutaneous flap, and yet is less commonly utilized than other free flaps in microvascular reconstructions of the head and neck. The aim is to conduct a high-quality Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA)- and Assessment of Multiple Systematic Reviews 2 (AMSTAR 2)-compliant systematic review comparing the use of the MSAP flap to other microvascular free flaps in the head and neck. Medline, Embase, and Web of Science databases were searched to identify all original comparative studies comparing patients undergoing head and neck reconstruction with an MSAP flap to the radial forearm free flap (RFFF) or anterolateral thigh (ALT) flap from inception to February 2021. Outcome studied were the recipient-site and donor-site morbidities as well as speech and swallow function. A total of 473 articles were identified from title and abstract review. Four studies met the inclusion criteria. Compared with the RFFF and the ALT flaps, the MSAP flap had more recipient-site complications (6.0 vs 10.4%) but less donor-site complications (20.2 vs 7.8%). The MSAP flap demonstrated better overall donor-site appearance and function than the RFFF and ALT flaps (p = 0.0006) but no statistical difference in speech and swallowing function following reconstruction (p = 0.28). Although higher quality studies reviewing the use of the MSAP flap to other free flaps are needed, the MSAP flap provides a viable and effective reconstructive option and should be strongly considered for reconstruction of head and neck defects.

• Proceedings of the KSME Conference
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• 대한기계학회 2003년도 춘계학술대회
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• pp.740-745
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method is based on the collocation method, no integration procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is required. A special coordinate transformation has been devised to consider the complicated free boundary conditions at boundary nodes. By the use of the special coordinate transformation, the radius of curvature involved in the free boundary conditions can be successfully dealt with. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by exact method and other analytical methods.

• Journal of the Microelectronics and Packaging Society
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• 제7권2호
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• pp.47-53
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• 2000

The fluxless wetting properties of TSM-coated glass substrate were evaluated by the wetting balance method. We could estimate the wettability of the TSM with new parameters obtained from the wetting balance test for one side-coated specimen. It was more effective in wetting to use Cu as a wetting layer and Au as a protection layer than to use Au itself as a wetting layer. The SnSb solder showed better wettability than SnAg, SnBi, and SnIn solders. The contact angle of the one side-coated glass substrate to the Pb-free solders could be calculated from the farce balance equation by measuring the static force and the tilt angle.

• Korean Journal of Child Studies
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• 제25권4호
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• pp.33-48
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• 2004

The purpose of this study was to examine if mothers and their children used different interaction strategies depending on the interacting contexts. Sixty-five mothers and their children were observed while they interacted with each other in two contexts, that is, a free play context and a joint problem solving context. The result of this study showed that first, the mothers' strategies and their children's strategies were closely related. When the mothers used positive strategies, their children also responded with positive strategies. In contrast, when the mothers used negative strategies, their children also tended to use negative strategies. Second, the contexts which the mothers and their children interacted affected the strategies that the mothers and their children used. The mothers and the children were more likely to use positive strategies in the context of free play than in the context of the joint problem solving. This result points out the importance of free play as the context of producing a positive atmosphere where the mothers and their children interacted positively and had a good time. Suggestions for further study and implications for parents were provided.