• Journal of Advanced Research in Ocean Engineering
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• 제2권2호
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• pp.86-98
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• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• 한국초전도ㆍ저온공학회논문지
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• 제14권2호
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• pp.20-23
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• 2012

With continuous development of the 2nd generation HTS conductor, the critical current of the conductor is also increasing. However, many applications require more than 2 conductors in parallel to transport large current. Applications such as HTS power cables and some HTS current leads usually need much larger transport current than that provided by a single conductor and they require more than several tens of HTS conductors. In the case of parallel connection of multiple HTS conductors, the current distribution depends on the contact resistance of each conductor at the terminals for DC operation. The non-uniform distribution of the terminal resistances results in a non-uniform distribution of the current. The resultant current non-uniformity affects on the measurement of the I-V curve and the thermal performance of the multiple conductors. This paper describes the I-V curves obtained from multiply connected HTS conductors with different terminal contact resistances to investigate the relationship between the distorted I-V curve and heat generation.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.47-50
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• 2005

The AC loss is an important issue in the design of the high temperature superconductor (HTS) power cables, which consist of a number of lli 2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. These make loss measurements considerably complex, especially for short samples of laboratory size. In this work we have prepared a multi-tape conductor composed of Bi-2223 tapes. The at losses of the conductor have experimentally investigated. The loss tests indicate that the effect of tapes critical currents on AC loss measurement in the multi tape conductor is negligible only if currents in the tapes flow uniformly Moreover, the measured tosses of the conductor are in good agreement with the sum of the transport losses in the tapes. However, in the case of non-uniform current distributions, the measured AC losses considerably depend on the current distribution parameter of the positioning of a voltage lead. Thus special cautions should be needed for the measurement of the true AC losses in the short power cable samples.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.163-164
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• 2005

Round shape Bi2212/Ag is isotropic and can be fabricated Rutherford cable to transport high current. Bi2212/Ag round wires with various Ag ratio were fabricated using powder-in-tube process. Double stacked 385 (55\times$7) filamentary wire of various wire diameter was heat-treated at various melting temperature. Wires which have Ag ratio of 0.3 and 0.42 of Ag tube for monofilament show similar critical current density. As average filament diameter decreases from 33 to 16 \mu$m, critical current density of wires increase, and in case of 16 ${\mu}m$ and $T_m$ 890$^{\circ}C$, critical current density was 2,062 $A/mm^2$ at 4.2 K, 0 T.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.17-20
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• 2001

Stress/strain dependencies of the critical current I$_{c}$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K. The external reinforcement was accomplished by soldering Ag-Mg tapes to single side or both sides of the sample. With the external reinforcement, the strength of tapes increased but I$_{c}$ decreased. The I$_{c}$ degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less remarkable on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current, which is closely associated with the location of them relative to the voltage-monitoring region in the tape. tape.

• Progress in Superconductivity
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• 제11권2호
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• pp.118-122
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• 2010

Electrical transport properties were measured on $SmFeAsO_{0.85}$ single crystals along the c-axis for various temperatures and magnetic fields. For the measurements a mesa structure was fabricated on the surface of the single crystals. Samples showed a metallic temperature dependence of resistance and current-voltage curves without hysteretic multiple branch splitting that is usually observed in tunneling Josephson junctions. In addition, in ab-planar magnetic fields, samples did not show the Fraunhofer-type field modulation of the critical current. All these features indicate that the c-axis transport characteristics of $SmFeAsO_{0.85}$ single crystals are explained by the anisotropic bulk superconductivity rather than Josephson tunneling.

• 한국정보처리학회논문지
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• 제6권2호
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• pp.396-407
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• 1999

A Multicast transfer is a critical delivery method to provide a transport service to multipeer applications, the various problems on the multicast transfer environments have been occurred from the results of current research. One of these problems is the multicast transport service issue to guarantee reliability and scalability. First, this paper presents the related research of the reliable multicast transport methods, and then proposes a new transfer architecture using the Agent Sender and Receiver Concept(ASRC) to solve a reliable multicast transfer issue. we also propose a method to apply the proposed architecture(ASRC) to the well-known sender-initiated and receiver-initiated transport protocol. In order 새 validate the proposed ASRC architecture, t도 applied sender and receiver system si compared and analyzed over the processing requirement and maximum throughput.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.257-262
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• 2002

Numerical model introduced in this study combines wave refraction-diffraction, breaking, bottom friction, lateral mixing, and critical shear stress and three sub-models for simulating waves, currents, and bottom change were briefly discussed. Simulations of beach processes and harbor sedimentation were also described at the coast neighboring Bangpo Harbor, Anmyundo, Chungnam, where the area has suffered from accumulation of drifting sand in a small fishing harbor with a wide tidal range. We also made model test for the case of a narrow tidal range at Nakdong river's estuary area to understand the effect of water level variation on the littoral drift. Simulations are conducted in terms of incident wave direction and tidal level. Characteristics of wave transformation, nearshore current, sediment transport, and bottom change are shown and analyzed. We found from the simulation that the tidal level impact to the sediment transport is very important and we should apply the numerical model with different water level to analyze sediment transport mechanism correctly. Although the model study gave reasonable description of beach processes and harbor sedimentation mechanism, it is necessary to collect lots of field observation data, including waves, tides and bottom materials, etc. for better prediction.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.240-245
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• 2000

The self-field losses in a long multifilamentary Bi-2223/AgMgNi tape with varying transport current, voltage tap configurations, frequency and tape arrangements were investigated. Experimental results show that the measured losses are strongly dependent on voltage gap configurations but independent on tape arrangements. All voltage taps except the center tap are found to agree well with those predicted by Norris for an elliptical conductor. The self-field losses are purely hysteretic in nature in the range of applied frequencies for the transport currents below the critical current.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.6-9
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• 2015

For many applications of $ReBa_2Cu_3O_{7-x}$ (ReBCO) tapes it is needed to know the anisotropic properties of the used conductor in a broad range of magnetic field. In this paper we present the results of transport measurements on the SuNAM tape (GdBaCuO) with the rotation of the sample in magnetic fields up to 5 T in liquid nitrogen. The critical current over the magnetic field orientation ($I_c({\theta})$) curves demonstrate the appearance of distinct second peak around c-axis in low fields. This peak almost vanishes in the fields over 3 T. The evolution of the ab-peak form is also presented: the peak consistently reduces its height with the magnetic field going up and in the high fields the shoulders rise, changing the type of the distribution. To describe experimental curves the vortex path model was applied to the angular distributions of the critical current in magnetic field. Good agreements of the experimental data with the analytical expressions were obtained that confirm the vortex path model approach.