• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.735-737
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• 2003

A superconducting motor consisting of high temperature superconducting (HTS) rotor and air-core stator is under development in Korea Electrotechnology Research Institute. HTS motor was designed for having the rated power of 100hp at 1800 rpm. HTS field winding is composed of sixteen HTS race track shaped coils wound with stainless steel-reinforced Bi-2223 tape conductor by react and wind fabrication method. Nomex Paper was used for electrical insulation. Each of four magnet pole assemblies was constructed with four double pancake sub-coils, mechanically stacked and electrically in series. Four magnet assemblies were fixed on an aluminum support structure to make effective heat transfer. Critical current (Ic) of HTS field winding was 41A but minimum Ic of sub-coils was 35A at 77K and self field. Joule heat generated in HTS field winding was 2.11W at 77K and 35A.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.900-902
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• 2003

Critical current($I_c$) degradation of HTS tapes after bending is one of the holiest issues in HTS development and application studies. Many people are measuring $I_c$ degradations for effect of tending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the $I_c$ degradation after repetitive bending, at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC), Innova Superconductor Technology(InnoST) and Korea Electro-technology Research Institute(KERI). For each specimen $I_c$ degradation was measured various bending radius as function of repetitive bending number.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1015-1017
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• 2003

In a research and development team of high temperature superconducting (HTS) transformer for power distribution, prior to manufacture a single phase 1MVA 22.9 kV/6.6 kV HTS transformer, a 1MVA transformer for insulation test with windings made of copper tapes with the same size as BSCCO-2223 HTS tape was manufactured. The test transformer was composed of both the copper windings of double pancake type and the shell type core of laminated silicon steel plates. The characteristics tests of the test transformer were performed, such as no load test, load test and short test at 77k using liquid nitrogen. Insulation tests, lightning impulse test, power-frequency voltage test and external insulation test, were accomplished also.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.851-853
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• 2004

This paper deals with current distribution analysis of the windings of a superconducting transformer with BSCCO-2223 High Tc Superconducting (HTS) tapes. Current distribution of HTS windings wound in parallel is analyzed by electromagnetic field analysis of finite element method and verified by experiments. For the sake of uniform current distribution, windings must be transposed so to make the impedances of each strands same. The parallel HTS tapes were transposed between the pancakes via non-superconducting joints because it is hard to make transpositions inside the pancake windings. In order to measure current distribution, test windings are fabricated and experimented for both transposed and non-transposed windings. We compared test results with calculated ones.

• 전기학회논문지
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• 제58권11호
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• pp.2223-2228
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• 2009

Dye sensitized solar cells(DSCs) have been very economical and easy method to convert solar energy to electricity. DSC can reach low costs in future outdoor power applications. However, to commercialize the DSC, there are still many shortages to overcome such a low efficiency in a large size DSC. In this study, DSCs were fabricated by an electrospray coating method for the $TiO_2$ thin film. They were compared with DSCs prepared by conventional coating methods. We conducted an experiment to obtain the optimized parameters of voltage, flow rate, incident angle and distance in the electrospray method. After we fabricated $TiO_2$ film using that way, we investigated the characteristics of DSC through I-V Curve, SEM and EIS. This novel method shows stable performance with an energy conversion efficiency of 3.44 % under 1 sun illumination (AM 1, $P_{in}$ of $100\;mW/cm^2$).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.221-223
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• 1999

In this work, samples were manufactured variously by changing conventional calcining and sintering conditions and we tried the utilization by making the heat treatment time, which is demanded to high-Tc phase formation, much shorter. We found out optimal heat treatment conditions with the analysis on formation process at superconducting phase in term of the change of calcining and sintering time and then, examined X-ray diffraction(XRD) patterns, scanning electron microscope(SEM) measurement and energy dispersive X-ray spectrometer(EDX) of the samples manufactured under heat treatment conditions which we suggest here. As a result, 2223 high-$T_c$, phase of (Bi,Pb)SrCaCuO superconductor starting with ($Bi_l$ xPbx,)$_2$$Sr_2$$Ca_2$$Cu_3$$O_y$, composition was formed from 1 hr sintering sample at temperature nearby melting point and also the completed sample with calcining and sintering time of 9 hr was formed high-$T_c$.low-$T_c$ phase appearing in sight above the critical temperature of liquid $N_2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.52-57
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• 2002

High temperature superconductors can only be applied against an engineering specification that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. However, in order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. Therefore, the composite insulation of double pancake coil type transformer are described and ac breakdown voltage characteristics of liquid nitrogen($LN_{2}$) under HITS pancake coil electrode made by Bi-2223/Ag are studied. Breakdown in $LN_{2}$ is dominated electrode shape and distance. And we investigated AC breakdown properties of $LN_{2}$ and complex conition of cryogenic gaseous nitrogen($CGN_{2}$) obove a $LN_{2}$ surface. Also, the surface voltage of GFRP was measured as a function of thickness and electrode distance in $LN_{2}$ and complex condition of $CGN_{2}$ above a $LN_{2}$ surface. This research presented information of electrical insulation design for double pancake coil type HTS transformer.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2213-2223
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• 2005

In order to reconstruct a full 3D human model in reverse engineering (RE), a 3D scanner needs to be placed arbitrarily around the target model to capture all part of the scanned surface. Then, acquired multiple scans must be registered and merged since each scanned data set taken from different position is just given in its own local co-ordinate system. The goal of the registration is to create a single model by aligning all individual scans. It usually consists of two sub-steps: rough and fine registration. The fine registration process can only be performed after an initial position is approximated through the rough registration. Hence an automated rough registration process is crucial to realize a completely automatic RE system. In this paper an automated rough registration method for aligning multiple scans of complex human face is presented. The proposed method automatically aligns the meshes of different scans with the information of features that are extracted from the estimated principal curvatures of triangular meshes of the human face. Then the roughly aligned scanned data sets are further precisely enhanced with a fine registration step with the recently popular Iterative Closest Point (ICP) algorithm. Some typical examples are presented and discussed to validate the proposed system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.2223-2242
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• 2019

Distance Vector-Hop (DV-Hop) algorithm is widely used in node localization. It often suffers the wormhole attack. The current researches focus on Double-Wormhole-Node-Link (DWNL) and have limited attention to Multi-Wormhole-Node-Link (MWNL). In this paper, we propose a security DV-Hop algorithm (AMLDV-Hop) to resist MWNL. Firstly, the algorithm establishes the Neighbor List (NL) in initialization phase. It uses the NL to find the suspect beacon nodes and then find the actually attacked beacon nodes by calculating the distances to other beacon nodes. The attacked beacon nodes generate and broadcast the conflict sets to distinguish the different wormhole areas. The unknown nodes take the marked beacon nodes as references and mark themselves with different numbers in the first-round marking. If the unknown nodes fail to mark themselves, they will take the marked unknown nodes as references to mark themselves in the second-round marking. The unknown nodes that still fail to be marked are semi-isolated. The results indicate that the localization error of proposed AMLDV-Hop algorithm has 112.3%, 10.2%, 41.7%, 6.9% reduction compared to the attacked DV-Hop algorithm, the Label-based DV-Hop (LBDV-Hop), the Secure Neighbor Discovery Based DV-Hop (NDDV-Hop), and the Against Wormhole DV-Hop (AWDV-Hop) algorithm.

• 한국초전도ㆍ저온공학회논문지
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• 제8권2호
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• pp.43-45
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• 2006

Recently, the resistive Fault Current Limiter (SFCL) made with Coated Conductor (CC) has been researched with an advanced capability in CC. Current limiting elements must be connected in series in order to fabricate the resistive SFCL having large capacity. By the way, unless the applied voltage in the SFCL is distributed to the elements when the fault occurred, those elements will be critically damaged. Thus simultaneous quench of the elements is an important factor to design the resistive SFCL. In this paper, simultaneous quench characteristics of current limiting module by using BSCCO 2223 were researched before manufacturing the resistive SFCL by using CC. At the first fault stage, the elements generated the resistance at the same time. However, the unequal voltage is applied to the each element in process of time. The method is suggested to solve the problem of the unequal distribution. These experimental results will play an important part in developing for the resistive SFCL by using CC.