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Geometric modeling and numerical analysis of multi-directional FGM (Functionally Graded Material) plate, whose material properties grade continuously both in its thickness and in-plane directions, are increasingly required. In this work, postbuckling behavior of this type of plates with multiple cutouts is, for the first time, numerically investigated through the combination of NURBS-based IGA (IsoGeonetric Analysis) and FCM (Finite Cell Method). The nonlinear deformation of plate is determined by TSDT (Third-order Shear Deformation Theory) and von Karman nonlinear assumptions without the requirement of SCFs (shear correction factors). Besides, the higher continuity advantage of NURBS basis functions can easily meet the C1-continuous requirement of the displacement field. The main contribution is introducing the FCM to deal with the influence of complex cutouts on the postbuckling characteristics. The geometric interfaces of the cutouts are approached and approximated by adaptive quadrature procedure in the distinguished cut elements. The advantage of this implementation is that the previously tricky process of representing the geometry of perforated plate with multiple NURBS patches can be eliminated, which naturally avoids the imposition of C1-continuity condition across the patch boundaries. The cylinder arc-length method combined with modified Newton–Raphson iteration algorithm, which takes into account of the initial geometric imperfections, is applied to implement geometrically nonlinear stability analysis and track the postbuckling paths. The effectiveness and reliability of the presented method are verified with available solutions of isotropic and conventional perfect FGM plates. Subsequently, a series of factors, including material volume fraction, length-to-thickness ratio, boundary condition, cutout size, etc., affecting the postbuckling responses of multi-directional perforated FGM plates are considered and investigated.

In this paper, a pulsed spark discharge plasma actuator array is deployed to control laminar–turbulent transition in a Mach 3.0 flat-plate boundary layer, and the subtle flow structures are visualized by nanoparticle planar laser scattering (NPLS) technique. Results show that the onset location of turbulence can be brought upstream by plasma actuation, corresponding to forced boundary-layer transition. Hairpin vortex packets evolved from the thermal bulbs play a vital role in the breakdown of laminar flow. With the help of a machine learning tool, all the relevant structures induced by plasma actuation are extracted from NPLS images, and a conceptual model of the hairpin vortex generation is proposed, including three stages: production and lift-up of the high-vorticity region, formation of the $\varLambda$ vortex and evolution of the hairpin vortex.

In this paper, the vibration and buckling analyses of the FGM (functionally graded material) plates with multiple internal cracks and cutouts under thermal and mechanical loads are numerically investigated using the combined XIGA-PHT (extended isogeometric analysis based on PHT-splines) and FCM (finite cell method). Material properties are graded only in the thickness direction. The effective material properties are estimated by using either the rule of mixture or the Mori-Tanaka homogenization technique. The plate displacement field is based on the HSDT (higher-order shear deformation plate theory) without any requirement of the SCF (shear correction factor). The HSDT model can exactly represent the shear stress distribution and improve the accuracy of solutions. The PHT-splines can naturally fulfill the C1-continuous requirement of the HSDT model. The representation of internal defects is mesh-independent. The discontinuous and singular phenomena induced by the cracks are captured using the enrichment pattern in the XIGA, and the influence of cutouts is implemented by the FCM. The geometries of cutouts are captured by means of adaptive quadrature procedure based on a simple unfitted structural mesh, which avoids the need for multiple patches to describe the complex geometry and eliminates the enforcement of C1-continuity patch-coupling across the patch boundaries. The initial mesh density around the cracks and cutouts can be controlled flexibly utilizing the local refinement property of the PHT-splines. After validating the results of the developed approach with those available in the literature, the effects of material gradient index, side to thickness ratio, boundary conditions, cutout size and crack length on the normalized frequency and the critical buckling parameter are investigated. Numerical results illustrate the effectiveness and accuracy of the present approach.

An isogeometric analysis is used to simulate the vibration and buckling problems of functionally graded plates with curvilinear stiffeners and cutouts. The polynomial splines over a hierarchical T-...

In this paper, a posteriori error estimation and mesh adaptation approach for thin plate and shell structures of through-the-thickness crack is presented. This method uses the extended isogeometric analysis (XIGA) based on PHT-splines (Polynomial splines over Hierarchical T-meshes), which is abbreviated as XIGA-PHT. In XIGA-PHT, the isogeometric displacement approximation is locally enriched with enrichment functions, which efficiently capture the displacement discontinuity across the crack face as well as the stress singularity in the vicinity of the crack tip. On the one hand, the rotational degrees of freedom (RDOFs) are not required in Kirchhoff-Love theory, which drastically reduces the complexity of enrichment mode and computational scale for crack analysis. On the other hand, the PHT-splines basis functions can automatically satisfy the requirement of C 1 -continuity for the Kirchhoff-Love theory. Moreover, the PHT-splines facilitate the local refinement, which is the deficiency of NURBS-based isogeometric formulations. The local refinement is highly suitable for adaptive analysis. The stress recovery-based posteriori error estimator combined with the superconvergent patch recovery (SPR) technique is used to evaluate the approximate local discretization error. A new strategy for selecting enriched recovered functions in the enriched areas was proposed. Special functions extracted from the asymptotic stress solutions are applied to obtain the recovered stress field in the enriched area. The results of stress intensity factors or J-integral values obtained by the adaptive XIGA-PHT are compared with reference solutions. Several thin plate and shell illustrative examples demonstrate the effectiveness and accuracy of the proposed adaptive XIGA-PHT.

Isogeometric analysis (IGA) with the polynomial splines over hierarchical T-meshes (PHT-splines) is used to provide an efficient tool capable of carrying out the vibration and buckling analyses of the stiffened laminates. IGA offers increased accuracy and efficiency using the PHT-splines, which represent exact geometry of the stiffeners and make the refinement more flexible near the areas where the stiffeners and composite plate are connected. Numerical examples are given to validate the correctness and superiority of the present method, comparing with the results from existing literatures and commercial softwares. Besides, the influences of the orientation, curvature, location and cross-section size of the stiffeners on the natural frequencies and buckling loads are also studied. The results show that the optimization of the shape and size of the stiffeners has an important effect on the vibration and buckling characteristics of stiffened laminates.

Isogeometric boundary element method (IGABEM) based on Bezier extraction of non-uniform rational B-splines (NURBS) is developed to analyze the crack propagation and the interaction between inclusions and cracks in 2D infinite isotropic medium. We use isogeometric analysis (IGA) with NURBS to describe the geometric boundaries of inclusions and cracks which can be represented exactly no matter how coarse the discretization of the studied bodies is, so there are no geometric errors. Meanwhile, the same NURBS basis functions are used to approximate the unknown boundary quantities. For the crack boundary, the collocation points are moved inside the crack elements to meet the continuity requirement, i.e., discontinuous quadratic elements are applied on the crack boundary. Then, in order to obtain accurate stress intensity factors (SIFs), special crack tip basis functions are adopted to simulate the r variation of displacements near the crack tips. Some numerical examples are given and the obtained results have been compared with the results in the references.

The isogeometric analysis boundary element method (IGABEM) has a broad application prospect due to its exact geometric representation and good approximation properties. In this paper, a novel radial integration IGABEM (RI-IGABEM) based on the generalized- α method is proposed to solve 2D and 3D elastodynamic problems of homogeneous and inhomogeneous materials. First of all, the elastostatics Kelvin fundamental solution is used as the fundamental solution of the problem. In order to preserve the advantage of IGABEM, i.e. only boundary is discretized, the radial integration method (RIM) is applied to transform the domain integral caused by the material heterogeneity and the inertia term into an equivalent boundary integral by means of applied points. In addition, using a simple transformation method, the rigid-body technique is applied to solve the strongly singular integrals , and the Telles scheme and the power series expansion method are used to solve the weakly singular integrals in RI-IGABEM respectively. Furthermore, the generalized- α method is adopted to solve the time domain problem, which can improve the stability of numerical results by effectively filtering out the false response of high frequency and minimizing the attenuation of low frequency response. A number of 2D and 3D examples, such as those with homogeneous materials, functionally gradient materials, and material defects and inclusions, are used to demonstrate the ability of the scheme to simulate the elastodynamic problems.

In this paper, the collocation-based isogeometric boundary element method (IGABEM) is combined with the isogeometric Reissner–Mindlin shell elements to conduct the mixed dimensional solid–shell coupling analysis. On the basis of taking advantages of the geometric smoothness and exactness of isogeometric analysis (IGA), this method can reduce the computational scale of the solid part and eliminate the procedure of constructing analysis-suitable volumetric discretizations. In addition, this method only needs to provide the surface CAD (computer-aided design) meshes of the whole coupling model, so it has great potential in achieving close link with CAD systems. For the coupling implementation, the stiffness formula of BE subdomains is formed by condensing the unknown tractions, which simplifies the implementation of coupling constraints. That is to say, only the displacement compatibility equations on the interface are required, without explicitly establishing the traction equilibrium conditions. Two coupling approaches are developed and studied. One is the collocation-based direct strict kinematic coupling based on the deformation hypothesis of the shell across the section, and another is the weak coupling formulation in an integral sense based on work equality. The accuracy and convergence properties of the presented coupling method are investigated through numerical examples including a complex impeller blade.

The problems of Acoustic-Structural Interaction (ASI) are commonly encountered in the simulation of the thin-walled structures immersed in the fluid. This interaction can affect the acoustic properties of the fluid and the dynamic characteristics of the structure. In this paper, a Non-Uniform Rational B-Splines (NURBS)-based Isogeometric Finite Element (FE) - Boundary Element (BE) symmetric coupling method is developed to study the ASI problems and the free vibration of the elastic structures submerged in the fluid. The geometry of the thin-walled structures is exactly modelled and discretized by utilizing the Isogeometric Reissner-Mindlin shell elements. This shell theory simplifies the continuity enforcement between NURBS patch boundaries. The Isogeometric Boundary Element Method (IGABEM) is applied to describe the acoustic field. In order to impose coupling constraints, a transformation equation of unknown variables on the interface between sound field and structure field is established, that is, sound pressure versus external force and particle velocity versus displacement. Different from the non-symmetric matrix obtained by the traditional direct BEM, a new variational formulation is introduced to obtain the symmetric coupling coefficient matrix, which maks this coupling approach suitable for a broad class of solvers and improves the robustness of the computation. The reliability and stability of the symmetric coupling method are verified by numerical examples considering acoustic and structural loadings. It is concluded that the symmetric coupling method possesses high accuracy, and can circumvent the limitation of traditional coupling method in solving open boundary problems.

In this paper, a three-dimensional (3D) isogeometric finite element (FE) and boundary element (BE) coupling approach based on non-uniform rational B-splines (NURBS) is developed to simulate the deformed body. Based on the geometric exactness and higher smoothness of isogeometric analysis (IGA), NURBS discretization is applied to the approximation of geometric representation, displacement field and traction field simultaneously. An improved power series expansion method (M-PSEM) is used to evaluate the singular integral and is suitable for high order ( ≥ 3) NURBS basis functions, which is the limitation of the traditional method. Adaptive integration scheme based on quadtree subdivision technique is adopted to enable the non-singular integration computation more flexible and efficient at optimal computational cost. The relationship between the tractions and nodal external forces on the interface is established by using the virtual work principle. On the other hand, displacement coupling constraints among the non-conforming (or incomplete coincident) surface meshes are constructed by a virtual knot insertion technique. The main advantages of this method are simplicity and robustness, as it is problem-independent and only depends on the NURBS meshes on both sides of the interface. Introducing an enhanced symmetric matrix related to the BE subdomain, the symmetric iterative coupling method (SICM) is extended to solve the final system coupling equation. The final coupling matrix obtained by this iterative method is symmetric, and its dimension is the same as that of the stiffness matrix of IGA finite element method (IGAFEM). Numerical examples are investigated to assess the accuracy and efficiency of the presented method.

In this paper, Finite Element-Indirect Boundary Element (FE-IBE) coupling approach based on the Isogeometric Analysis (IGA) framework is proposed to deal with Acoustic-Structural Interaction (ASI) problems. Numerical simulation of thin-walled structures is carried out by using isogeometric Reissner-Mindlin shell theory. The isogeometric indirect boundary element method (IBEM) is used to simulate the fluid domain, and the coupling formula is established by connecting the primary variables. IBEM contains information on both sides of the boundary. Naturally, FE-IBE coupling method inherits these attractive features. FE-IBE coupling method has a wide application prospect. In general, it can not only deal with the common problems, but also solve the problems that Finite Element-Direct Boundary Element (FE-DBE) coupling method cannot handle, such as the opened boundary problems, whose inner and outer boundaries contact the liquid. In order to further expand its application range, based on the universality of the primary variables in IBEM, a more generalized coupling formula is derived to solve the hybrid problems with both the closed and opened boundaries. Numerical examples with analytical solution verify the reliability and stability of the proposed IGA FE-IBE coupling method, and two complex problems in aerospace engineering and ocean engineering are studied in detail.

This paper introduces two NURBS (Non-Uniform Rational B-Splines)-based Isogeometric FE (Finite Element)-BE (Boundary Element) coupling approaches, i.e. DCM (Directed Coupling Method) and SICM (Symmetric-Iterative Coupling Method), to solve the structural-acoustic interaction problems. IGA (IsoGeometric Analysis) can eliminate the substantial geometrical errors and time-consuming meshing steps. Meanwhile, CAD (Computer Aided Design) only makes use of surface representations to model geometrical objects, which is naturally combined with BEM (Boundary Element Method). Therefore, the IGABEM (Isogeometric Boundary Element Method) simulates the acoustic domain described by the Helmholtz equation, while structures are discretized by using the Isogeometric Reissner-Mindlin shell elements that only require C 0 -continuity across the element boundaries, which simplifies the continuity enforcement between patch boundaries. The main strategy of two coupling approaches is to establish the transformation of interface boundary conditions, that is, the sound pressure is converted to the force boundary conditions of shell structure. The reliability and accuracy of DCM are verified by analytical solutions or Lagrange-based coupling method. By using the model with six identical bi-quartic NURBS patches, the geometric singularity of the spherical surface is eliminated, and the accuracy is significantly improved. It is found that the interaction between the fluid and structure is closely related to the physical properties of the fluid. Compared with Lagrange model, IGA method has much higher accuracy and convergence. SICM method is introduced for the first time to deal with the structure-sound interaction problem. Although SICM fails near the natural frequency of the structure, it has the advantage of generating symmetric coupling matrix, which greatly reduces the dimension of the matrix. Finally, a complex toroidal shell subjected to the mixed structural-acoustic loads, including the plane acoustic wave and the concentrated load, is investigated.

Introduction To evaluate the improvement of systolic and diastolic left ventricular(LV) dysfunction by preconditioning and postconditioning with netrin-1 after acute myocardial infarction(MI) in rat model, we examined the changes of echocardiographic parameters and compared with them before and after MI. Methods Male, 8-to 9-week-old, Spraque-Dawley rats with a mean body weight of 277.40 ±9.48 g were anesthesized with intraperitoneal injection of pentobarbital at a dose of 65 mg / kg, followed by intubation and positive pressure ventilation for 15 minutes as a stabilizing period. The acute MI model had the ligation of left coronary artery under heart exposure through 4-5th intercostal space then closed. After 30 minutes under mechanical ventilation, the left anterior descending artery (LAD) of the rat was ligated for 30 minutes And reperfusion for 2 hours to produce an ischemic / perfusion animal model of myocardial ischemia. After 30 minutes of ischemia, netrin-1(5mcg/kg) was slowly injected into MI group but vehicle(normal saline) into another MI group via tail vein. Netrin-1 preconditioning was administered intravenously 3 minutes before the induction of ischemia and 3 minutes after the induction of ischemia. Netrin-1 postconditioning was administered intravenously 5 minutes before the end of ischemic induction for 3 minutes and pentobarbital 35 mg / kg after 2 hours of reperfusion. And the echocardiographic evaluation was performed. Using Vevo2100, Echocardiographic studies were performed before surgery and After 120 minutes of reperfusion. Results Fractional shortening values were significantly increased in the pre-isch, pre-netrin, post-isch and post-netrin groups compared to the vehicle group. The EF (ejection fraction), And in the post-netrin group, the left ventricular systolic function was improved. E'(initial diastolic velocity) values were significantly higher in the post-iso, post-isch, and post-netrin groups than in the vehicle group. E / E', Post-isch, post-isch, and post-netrin, respectively. Discussion Preconditioning and postconditioning with netrin-1 makes meaningful improvemet of systolic dysfunction with significant increase with FS and EF after acute MI. Also it helps E’ recovery for LV diastolic function and E/E’ ratio for left atrial pressure.

DC HTS cable has advantages in the absence of ac loss. Therefore, the Korea Electric Power Corporation (KEPCO) has started a project of operating and manufacturing technology for applying an 80-kV 500-MW 500-m-long dc HTS cable to the commercial power grid since 2011. LS Cable Ltd. has joined this project for designing and manufacturing an HTS power cable, and KEPCO has taken on cryogenic system and real power grid operation. The cryogenic system for an 80-kV dc HTS cable is composed mainly of Stirling-type cryocoolers. The Stirling cryocooler has been examined and verified by real grid operation in Icheon substation, and we therefore became assured of reliability for the cooling HTS cable system. We present the cryogenic system design, installation, and some results of preliminary tests in this paper.

FeCrAl is comprised essentially of Fe, Cr, Al and generally considered as metallic substrates for catalyst support because of its advantage in the high-temperature corrosion resistance, high mechanical strength, and ductility. Oxidation film and its adhesion on FeCrAl surface with aluminum are important for catalyst life. Therefore various appropriate surface treatments such as thermal oxidation, Sol, PVD, CVD has studied. In this research, PEO (plasma electrolytic oxidation) process was applied to form the aluminum oxide on FeCrAl surface, and the formed oxide particle according to process conditions such as electric energy and oxidation time were investigated. Microstructure and aluminum oxide particle on FeCrAl surface after PEO process was observed by FE-SEM and EDS with element mapping analysis. The study presents possibility of aluminum oxide formation by electro-chemical coating process without any pretreatment of FeCrAl.

Introduction The purpose of this study was to investigate whether tidal volume (TV) of 8 mL/kg without positive end-expiratory pressure (PEEP) and TV of 6 mL/kg with or without PEEP in pressure-controlled, ventilation-volume guaranteed (PCV-VG) mode can maintain arterial oxygenation and decrease inspiratory airway pressure effectively during one-lung ventilation (OLV). Methods The study enrolled 27 patients undergoing thoracic surgery. All patients were ventilated with PCV-VG mode. During OLV, patients were initially ventilated with TV 8 mL/kg (group TV8) without PEEP. Ventilation was subsequently changed to TV 6 mL/kg with PEEP (5 cmH2O; group TV6+PEEP) or without (group TV6) in random sequence. Peak inspiratory pressure (Ppeak), mean airway pressure (Pmean), and arterial blood gas analysis were measured 30 min after changing ventilator settings. Ventilation was then changed once more to add or eliminate PEEP (5 cmH2O), while maintaining TV 6 mL/kg. Thirty min after changing ventilator settings, the same parameters were measured once more. Results The Ppeak was significantly lower in group TV6 (19.3±3.3 cmH2O) than in group TV8 (21.8±3.1 cmH2O) and group TV6+PEEP (20.1±3.4 cmH2O). PaO2 was significantly higher in group TV8 (242.5±111.4 mmHg) than in group TV6 (202.1±101.3 mmHg) (P = 0.044). There was no significant difference in PaO2 between group TV8 and group TV6+PEEP (226.8±121.1 mmHg). However, three patients in group TV6 were dropped from the study because PaO2 was lower than 80 mmHg after ventilation. Discussion It is postulated that TV 8 mL/kg without PEEP or TV 6 mL/kg with 5 cmH2O PEEP in PCV-VG mode during OLV can safely maintain adequate oxygenation.

Using dc magnetic susceptibility, electron spin resonance (ESR) and dielectric spectroscopy techniques, we investigate the magnetic and dielectric properties of Sr 7 Mn 4 O 15 , which has a layered structure with pairs of face-sharing octahedra Mn 2 O 9 . Magnetic susceptibility reveals the Neel temperature T N ∼70.5 K, above which Sr 7 Mn 4 O 15 manifests intense short range order. ESR spectra indicate the existence of a transition at about 370 K, confirming the suggested spin pairing in the Mn 2 O 9 units. In the dielectric spectra, a sudden drop of permittivity is observed at T N , revealing the existence of strong spin–lattice coupling in Sr 7 Mn 4 O 15 .

The 22.9 kV/50 MVA AC HTS power cable system consisted of power cable with 410 m length and cryogenic system has been manufactured by LS Cable & System and installed in Icheon substation of KEPCO grid in the end of 2010. High temperature superconductor only appears the superconductivity at the constant temperate range. So in order to maintain the superconductivity, the cryogenic system is needed. The cryogenic system, the open-loop type, is consisted of the Pressure Control System (PCS), Gas/liquid separator, Circulation Pump, Decompression unit, Filter and so on. Decompression unit is a device that keeps the sub-cooled nitrogen by way of the latent heat of evaporation and includes the heat exchanger. The effectiveness-NTU method is used for the design of the heat exchanger. After installation of the cryogenic system on the site, the test of the cooling capacity of the cryogenic system and commissioning tests were performed. During the grid operation of the HTS power cable system, no major problems have been encountered to this point. The cryogenic system has been operated sufficiently to maintain a stable of the HTS power cable system. This paper will summarize the design of the cryogenic system and the results of the grid operation.

This paper presents dynamic analysis of FCEV(fuel cell electric vehicle) turbo blower. To analyze the dynamic characteristics of turbo blower, FEA(finite element analysis) and experimental test are performed. Evaluations of stress safety for rotor sleeve and impeller due to rotational force and shrink fit are performed. Rotor dynamic analysis is conducted by Campbell diagram and structure vibration analyses are performed using FEA and experimental test. Through these results, noise sources of turbo blower are verified.

The Korea Electric Power Corporation (KEPCO) HTS power cable has been successfully installed and operated for feasible confirmation since 2006 at Gochang power test center. The 3-phase 100 m long HTS power cable with 22.9 kV/1.25 kA was manufactured and cooled by subcooled liquid nitrogen. At the beginning stage, the cooling system was composed of a liquid nitrogen decompression cooling unit. No major fault has been observed during long term operating test. As a next step, cooling system was modified that a cryocooler was employed, resulting in the total cooling capacity of 4 kW at liquid nitrogen temperature. In this paper, the progress on the performance test of HTS power cable is reported. Temperature as well as pressure in the system is discussed with respect to the supplied current levels. Also, the installation of hybrid cooling system for real power grid application is described.

The X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, and resistivity ρ are measured on Nd 1.85− x R x Ce 0.15 CuO 4± δ ( R = Gd and Sm) single crystals. From the XRD and FTIR spectra studies, the lattice constant c are found to decrease faster for Gd doping than that for Sm doping with increasing doping concentration x . Upon Gd doping, all the transmission peaks shift to high frequency but nearly unchanged with increasing Sm doping content. The volume of the unit cell observed through XRD and FTIR spectra decreases faster for Gd doping than that for Sm doping. Furthermore, for Gd doping the superconducting T c decreases rapidly with increasing the doping concentration, while the T c decreases slowly for Sm doping with increasing Sm content, which is found to be very well consistent with the evolution of the volume of the unit cell for two series.

A two-and-a-half-dimensional (2.5D) platform for enabling silicon nano-photonics and dense electrical interconnections between interposers in a tile-like configuration is presented. Three 20 × 20 mm silicon interposer tiles are assembled directly on an FR4 printed wiring board (PWB), and two 6 × 20 mm silicon bridges are assembled on top of the interposer tiles. Accurate alignment of interposer tiles to bridges, an important metric in enabling highly efficient optical coupling, is provided using positive self-alignment structures (PSASs). It is demonstrated that by using PSAS on two silicon substrates, sub-micron alignment between substrates is possible; in the cascaded configuration involving FR4

In order to investigate the compatibility as a power utility facility, Korea Electric Power Corporation (KEPCO) had installed a 22.9 kV, 1250 A, 100 m long high temperature superconducting (HTS) power cable system. Using the HTS cable, various tests have been performed to investigate electrical and thermo-mechanical properties. Since 2005, a series of thermal cycle tests between liquid nitrogen (LN 2 ) and ambient temperatures have been conducted using a vacuum-pump driven open-loop cryogenic system with a capacity of 3 kW. In the tests, although the open-loop cryogenic system was reliable to operate the HTS cable system, it was not effective in economic view point because LN 2 consumption was larger than expected. In order to secure against unexpected emergencies and solve the problem of LN 2 consumption, a hybrid cryogenic system was designed and installed. A stirling cryocooler was employed and combined with the open-loop cryogenic system. Considering the average heat load at rated condition, the cooling capacity of the cryocooler was determined to 4 kW at 77 K. In this paper, results of performance tests and the design of the hybrid cooling system are presented.

In Korea, two long-term field demonstrations for high temperature superconducting (HTS) cable have been carried out for several years; Korea Electric Power Corporation (KEPCO) and LS Cable Ltd. (LSC) independently. Encouraged at the result of the projects performed in parallel, a new project targeting the real grid operation was launched in the fourth quarter of 2008 with the Korean government’s financial support. KEPCO and LSC are jointly collaborating in the selection of substation, determination of cable specification, design of cryogenic system, and the scheme of protection coordination. A three phase 500 m long HTS cable at a distribution level voltage of 22.9 kV is to be built at 154/22.9 kV Icheon substation located in near Seoul. A hybrid cryogenic system reflecting the contingency plan is being designed including cryocoolers. The HTS cable system will be installed in the second quarter of 2010, being commissioned by the fall of 2010. This paper describes the objectives of the project and design issues of the cable and cryogenic system in detail.

In Korea, the KEPCO (Korea Electric Power Corporation) HTS power cable system has been successfully operated for evaluating the technical and economic feasibility as well as accumulating the operation experience since 2006. A cooling system composed of a liquid nitrogen decompression cooling unit and a closed-circulation system of subcooled liquid nitrogen at the KEPCO's Gochang power testing center. As the next step, we adjusted the cooling system for the purpose of testing a different cooling system using a cryocooler unit with cooling capacity of 4 kW at 77 K in the existing cooling system. It was designed to be used as a hybrid cooling system. In other words, it has as an each system of cryocooler unit or decompression pump unit. In this paper, the performance test results are summarized and the outline of the hybrid cooling system is introduced.

Fifteen USDA Select beef strip loins were divided individually into four equal width sections, and one of six treatments containing phosphate and/or calcium lactate (CAL) enhancement solutions were assigned randomly to each loin section (n = 10). Steaks from each loin section were packaged with high-oxygen (80% O2) modified-atmosphere packaging, and/or irradiated at 2.4 kGy, stored 10 days and then displayed for 5 days at 1 °C. Instrumental colour, total reducing activity (TRA), 2-thiobarbituric acid value (TBARS), and NADH concentration were measured. Loins with CAL and phosphate maintained the most stable red colour, increased NADH (p

The semi-retractable current lead cooled by a cryocooler is designed for a high field superconducting magnet system. The semi-retractable current lead is composed of a normal metal element, conducting the current from room temperature to an intermediate temperature, and an HTS element, conducting the current down to liquid helium temperature. An HTS element and the joint between the normal metal and HTS element are connected to a two-stage cryocooler. The intermediate joint carries current through a strip of louvered material. After charging the normal metal element is disengaged from the HTS element without breaking vacuum in the insulating space. The semi-retractable current lead is fabricated and assembled with a two-stage cryocooler for feasibility test. The adaptability and reliability of the lead are tested during engage and disengage performance. The electrical contact resistance is also measured in the intermediate joint with respect to the vacuum level and temperature has been measured.

Two different bovine muscles -M.longissimus lumborum (LD) and M. psoas major (PM) - were injection-enhanced (n=10, respectively) with solutions containing phosphate and potassium L- or D-lactate, cut into steaks, packaged with a high-oxygen (80% O(2)) modified atmosphere packaging, stored 9d at 2°C and then displayed for 5d at 1°C. Instrumental color, total reducing activity (TRA), lactate dehydrogenase (LDH) activity, and NADH were measured. Enhancement with L-lactate resulted in less color deterioration, and higher a(∗) and chroma values (P0.05) than non-enhanced control of the bovine muscles. L-lactate enhancement significantly increased NADH concentration and TRA of LD and PM than the non-enhanced control through increased LDH-B flux at 14d. This study presents supportive evidence that the lactate-LDH system remains active for muscles with different metabolic activities and may be a possible mechanism of the lactate-color stabilization effect. Further, L-lactate enhancement can be utilized for improving muscles with lower color stability in high-oxygen modified atmosphere.

In order to meet the needs of economical and stable power supply and high current density cable with compact size, several countries carry out researches on high temperature superconducting (HTS) cables. Korea Electric Power Corporation (KEPCO) established the HTS cable test center and installed 22.9 kV, 1250 A, 50 MVA, 100 m class HTS cable system to investigate the performances and application possibility in real power grids. The HTS cable system went through seven cool down and warm-up cycles and also many kinds of performance tests for 3 years. Rated voltage-current tests, over voltage tests, and measurements of heat loss and AC loss with various currents have been examined. Moreover, DC critical current tests were performed for checking conductor degradation before warming up or after cooling down. Through the performance tests of the HTS cable system, the overall efficiency and loss factors are estimated and compared with conventional power cables in this paper. We conclude the present status of HTS cable system and application possibility in the real power grid.

The experiments of electrical resistivity and thermopower on Nd 0.75 Sr 1.25 CoO 4 film in the temperature range 90 K T

One way of achieving controlled crack growth is to introduce notches into the surface of the guide hole wall. This results in high stress concentration at the notch tips when the stress wave reaches the guide hole. This paper presents the estimated fracture properties for analyzing blasting-induced fracture processes in PMMA specimens. The model experiments, which have a notched guide hole between the charge holes, were simulated using dynamic fracture process analysis (DFPA) software to examine the effect of the notched guide hole on fracture plane control. The influence of the location of the guide hole and the initiation time lag on the crack propagation control is discussed, as is the relationship between the applied fracture energy and crack extension.

The in-plane resistivities ( ρ ) and thermopower ( S ) are studied in the Nd 1.85 Ce 0.15 CuO 4+ δ single crystals under different annealing conditions. In the optimally annealed samples, a positive thermopower indicates the existence of a holelike band. The resistivity and thermopower behaviors can be well described in a two-band model characterized by the different relaxation time (i.e. τ h ∝ T −1 in holelike band and τ e ∝ T −2 in electronic band). Moreover, the band shape is nearly unchanged and the Fermi level ( E F ) rises after the samples further deoxygenated. In contrast, the width of holelike band has been broadened and the Fermi level is nearly unchanged after the further oxygenation process.

A closed-loop cooling concept for 21 T Fourier transform ion cyclotron resonance (FT-ICR) superconducting magnets is presented. In the magnet system, low temperature superconducting coils are immersed in a subcooled 1.8 K bath, which is connected to the saturated helium reservoir through the weight load relief valve. Saturated liquid helium is refrigerated by a Joule-Thomson (JT) heat exchanger and flows through the JT valve, isenthalpically dropping its pressure to approximately 1.6 kPa, corresponding to a saturation temperature of 1.8 K. Helium gas exhausted from JT pump is liquefied by a two-stage cryocooler located after the vapor purify system. In the present paper, the amount of heat budget is determined and the structural design of cryostat is carried out by the relevant analyses. The position of a cryocooler in the magnet system is investigated, taking into account the requirement of magnetic field for normal performance. Helium liquefaction system, a key component of the closed-loop cooling system, is fabricated and tested in order to demonstrate the feasibility of our new cryogenic cooling for high field magnets.

The temporal and spatial evolution processes of the in-cylinder flow structures and turbulence intensities in the symmetry and offset planes of a motored four-valve, four-stroke engine during the intake and compression strokes are diagnosed by using a particle image velocimeter. Two pistons of different crown shapes (flat-crown and slightly concave-crown pistons) are studied. The inception, establishment, and evolution of the tumbling vortical flow structures during the intake and compression strokes are clearly depicted. Quantitative strengths of the rotating vortical flow motions are presented by a dimensionless parameter, the tumble ratio, which can represent the mean angular velocity of the vortices in the target plane. The turbulence intensity of the in-cylinder flow is also calculated by using the measured time-varying velocity data. The results show that the flat-crown piston induces higher bulk-averaged tumble ratio and turbulence intensity than the slightly concave-crown piston does because the tumble ratio and turbulence generated by the flat-crown piston in the offset planes during the compression stroke are particularly large. The engine with the flat-crown piston also presents larger torque and power outputs and lower hydrocarbon emission than that with the slightly concave-crown piston. This might be caused by the enhanced combustion in the engine cylinder due to the stronger tumble ratio and turbulence intensity.

Several verification tests are being underway world widely in order to apply HTS cable to real grid. KEPCO (Korea Electric Power Corporation) has initiated HTS cable project since 2002 with the aid of MOCIE (Ministry of Commerce, Industry and Energy), Korea. The HTS cable system with the specification of three-phase, 1.25 kArms, 22.9 kV and 100 m was installed at the KEPCO’s Gochang test yard. In consideration of economical efficiency on retrofit for typical underground cable, the HTS cable was designed to be applicable for 175 mm ELP duct and 55 m-long cable was laid on underground trench in the same manner as the conventional pulling method. Cool-down to LN2 temperature and warm-up to room temperature were performed several times to investigate the influence of thermal cycle. The main objectives of this project are to verify performance of the HTS cable system and evaluate the economical and technical feasibility from all angles. Expected pros and cons of HTS cable including reliability and maintainability will be assessed with the view point of utilities. This paper summarizes some results of installation and after-laying tests.

Thermopower (S), in-plane resistivity (ρ) and magnetic susceptibility (χ) on electron-doped Nd1.85Ce0.15CuO4+δ single crystals have been investigated. Susceptibility (χ) shows a kink at T m about 230 K. T m is close to the characteristic temperature T ∗ of thermopower. A positive thermopower over the whole temperature region suggests the existence of holelike carrier and the behavior of temperature dependent diffusion thermopower can be attributed to two-band model, which means the coexistence of two types of charge carriers and we abbreviate them as holelike band and electronic band in this text. When the temperature increases above T ∗ , the diffusion thermopower of holelike band contribution satisfies the Heikes formula as a narrow band does and the bandwidth t is estimated about 0.02 eV. The fitting results of resistivity in deoxygenated and oxygenated samples support the coexistence of two types of charge carriers. A kink is also observed in a derivative plot of in-plane resistivity at the temperature close to T ∗ .

As high temperature superconducting (HTS) power cables have some merits over conventional cables, several demonstration projects on the HTS cable system are presently under way around the world. Korea Electric Power Corporation (KEPCO) also initiated an HTS cable project in 2002 with the Korean government's support. A three phase 100 m HTS cable system with a capacity of 50 MVA has been installed at Gochang test yard, located in Chonnbuk province, Korea. The HTS cable system is composed of a 100 m-long cable, two terminations and a cooling system. The rated current is 1,250 Arms and the rated voltage is 22.9 kV considering compatibility with the conventional power distribution system in Korea. Main purposes of this project are to verify the performance of an HTS cable system and to evaluate the potential of the HTS cable system from the viewpoint of power utilities. The real grid application of the HTS cable system requires the demonstration of system reliability, accumulated operation experiences, and it has to meet the practical needs of the utilities. In such a meaning, this project provides various challenges for KEPCO, and the feedback will be delivered to cable manufacturers. This user initiative test will facilitate the introduction of HTS cable systems into a real grid network. The installation process of the HTS cable system and some results of the preliminary test were presented in this paper.

A new concept of current leads for a 21 T Fourier Transform Ion Cyclotron Resonance (FT-ICR) superconducting magnet system is presented. The binary current lead, a series combination of a normal conductor in the high-temperature section and an HTS conductor in the low-temperature section, is employed. The HTS section is partly immersed in liquid helium and the joint between the normal metal and HTS conductor is cooled by the contact with a cryocooler. After excitation, the normal metal conductor section is thermally disengaged from the HTS section without disturbance to the insulating vacuum space and without requiring complete removal of the current leads. The present paper describes the so-called semi-retractable current leads for a 21 T FT-ICR magnet system application. The optimized dimensions of the leads are presented in order to minimize the thermal heat load when carrying operational current with some margin.

A submerged biofilm sequencing batch reactor (SBSBR) process, which liquor was internally circulated through sandfilter, was designed, and performances in swine wastewater treatment was evaluated under a condition of no external carbon source addition. Denitrification of NOx-N with loading rate in vertical and slope type of sandfilter was 19% and 3.8%, respectively, showing approximately 5 times difference, and so vertical type sandfilter was chosen for the combination with SBSBR. When the process was operated under 15 days HRT, 105L/hr.m3 of internal circulation rate and 54g/m3.d of NH4-N loading rate, treatment efficiencies of STOC, NH4-N and TN (as NH4-N plus NOx-N) was 75%, 97% and 85%, respectively. By conducting internal circulation through sandfilter, removal performances of TN were enhanced by 14%, and the elevation of nitrogen removal was mainly attributed to occurrence of denitrification in sandfilter. Also, approximately 57% of phosphorus was removed with the conduction of internal circulation through sandfilter, meanwhile phosphorus concentration in final effluent rather increased when the internal circulation was not performed. Therefore, It was quite sure that the continuous internal circulation of liquor through sandfilter could contribute to enhancement of biological nutrient removal. Under 60g/m3.d of NH4-N loading rate, the NH4-N level in final effluent was relatively low and constant(below 20mg/L) and over 80% of nitrogen removal was maintained in spite of loading rate increase up to 100g/m3.d. However, the treatment efficiency of nitrogen was deteriorated with further increase of loading rate. Based on this result, an optimum loading rate of nitrogen for the process would be 100g/m3.d.