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The origin of characteristic increase of continental-scale summer surface temperature in decades over Northern hemisphere was investigated. July-temperature in Europe, East Asia, the North Pacific, and western North America have been undergoing more increase than the global average of about 1ºC increase, especially in recent years. On the contrary, MME of 37 CMIP5 models do not show the focused regional warming hot-spots but exhibits hemispheric surface temperature increase. From the comparison between GISTEMP observation record and CMIP5 MME historical data, we show an evidence that the observed characteristic increase of regional temperature for the recent 43 years is dominated by the Internal Climate Variability (ICV) of decadal time-scale. Performing EOF analysis on the ICV, the four dominant modes are identified as Pacific Decadal Oscillation (PDO), North Pacific Oscillation (NPO), Pacific Meridional Mode (PMM), and Atlantic Multi-decadal Oscillation (AMO). It is also shown that, with only two dominant modes among those modes, large portion of continental-scale temperature increase can be explained: We show that PDO and PMM are dominant modes in Europe and East Asia, NPO and AMO in the North Pacific, and PDO and NP in western North America. The observed sub-trend is nicely reproduced with only these two modes. Quantitatively, the observed sub-trend from ICV explains 73%, 60%, 55%, and 18% of the total variability in North Pacific, East Asia, western North America and Europe, respectively. Note that, despite 82% of temperature fluctuation in Europe is attributed by the external forcing, 18% of the internal variability is still important to explain the increasing number of extreme heat events in Europe in recent several decades.

The fabrication process of metallic hydrophobic surfaces was investigated using copper electrodeposition and oxidation. Hierarchical structures have well known advantages for producing super-hydrophobic surfaces. A micro-pillar array with a hierarchical structure of copper was fabricated through a sequential process of laser ablation followed by electrodeposition. Heat oxidation enhanced the hydrophobicity of both flat and micro-structured copper surfaces. Electrodeposition at higher current density gave a hierarchical structure with low surface energy, resulting from the presence of copper oxide. Fabricated surfaces with a depth of more than 100 micrometers display super-hydrophobicity. The effects of copper oxide and hierarchical structure were confirmed by an oxidation test of the fabricated structures, because the thickness of copper oxide was undetectable by XRD and XPS.

A novel beam-elastic substrate element with inclusion of microstructure and surface energy effects is proposed in this paper. The modified couple stress theory is employed to account for the microstructure-dependent effect of the beam bulk material while Gurtin-Murdoch surface theory is used to capture the surface energy-dependent size effect. Interaction mechanism between the beam and the surrounding substrate medium is represented by the Winkler foundation model. The governing differential equilibrium and compatibility equations of the beam-elastic substrate system are consistently derived based on virtual displacement and virtual force principles, respectively. Both essential and natural boundary conditions of the system are also obtained. Two modified Tonti’s diagrams are presented to provide the big picture of both displacement-based and force-based formulations of the system. Due to similarity between the current problem and the one related to the beam on Winkler-Pasternak foundation, the so-called “natural” beam-Winkler-Pasternak foundation element coined by the authors is employed to perform two numerical simulations to study the characteristics and behaviors of a beam-substrate system with inclusion of microstructure and surface effects.

The goal of this paper is to invent a simulation tool for developers of electric vehicle unit system. An electric vehicle simulator structured by MATLAB/SIMULINK can change all kinds of important parameters to use GUI and observe the results. Also, if it has a new MATLAB/SIMULINK model or an experimental data of an invented component, it can be applied to perform a simulation. Additionally, we conducted a simulation in a virtual environment with a model, inventing practical driver conduct, and thus we could obtain a practically reliable simulation data. On this paper, we present each characteristic briefly and finally set Nissan Leaf vehicle as a simulator to show possibilities of a simulator as the simulator obtains similar results compared with a practical vehicle.

In DC micro-grid system energy storage systems (ESS) are responsible for storing energy and balancing power. Also, control target of the bidirectional DC-DC converter(BDC) for ESS should be changed depending on the operating mode. During the grid connected mode, the BDC controls the battery current or voltage. When a grid fault occurs, the BDC should change the control target to regulate the DC-bus. The BDC with conventional control method may experience large transient state during the mode change. This paper proposes a control method of BDC for ESS. The proposed control method is able to provide autonomous and seamless mode transfer by a variable current limiter. To validate the proposed concept, simulation results using PSIM and experimental results from a 2kW prototype are provided.

In this research, the fabrication process of a super-hydrophobic metallic surface using laser ablation and electrodeposition was investigated. Re-entrant structure and surface roughness play an important role in forming a super-hydrophobic surface on intrinsically hydrophilic material. A micro pillar array with a re-entrant structure of copper on stainless steel was fabricated through a sequential process of laser ablation, insulating, mechanical polishing and electrodeposition. Spacing of the micro pillars in the array played a major role in the structure hydrophobicity that was confirmed by measuring the water contact angle. Surface morphology changed relative to the parameters of the laser ablation process and electrodeposition process. Under a gradual increase in current density during the electrodeposition process, surface morphology roughness was maximized for fabricating a super-hydrophobic surface. Finally, the super-hydrophobic surface was successfully fabricated on metal.

This paper proposes an isolated bidirectional three-phase push-pull dc-dc converter for high power application such as eco-friendly vehicles, renewable energy systems, energy storage systems, and solid-state transformers. The proposed converter achieves ZVS turn-on of all switches and volume of passive components is small by an effect of three-phase interleaving. The proposed converter has identical switching pattern for both boost and buck mode, and therefore can provide seamless characteristic at the mode transition. A 3kW prototype of the proposed converter has been built and tested to verify the validity of the proposed operation.

This paper presents the design, fabrication and performance of a reinforced concrete beam strengthened by GFRP box plate and its possibility for structural rehabilitations. The load capacity, ductility and failure mode of reinforced concrete structures strengthened by FRP box plate were investigated and compared with traditional FRP plate strengthening method. This is intended to assess the feasibility of using FRP box plate for repair and strengthening of damaged RC beams. A series of four-point bending tests were conducted on RC beams with or without strengthening FRP systems the influence of concrete cover thickness on the performance of overall stiffness of the structure. The parameters obtained by the experimental studies were the stiffness, strength, crack width and pattern, failure mode, respectively. The test yielded complete load-deflection curves from which the increase in load capacity and the failure mode was evaluated.

Research on steel plate concrete (SC) structures for the modularization of nuclear power plants have been performed recently in Korea. In this study, the seismic capacity and stiffness characteristics of unstiffened SC shear walls under the effects of earthquakes were investigated through static pushover tests. Failure modes, sectional strength, and stiffness characteristics of SC structures under lateral loads were inspected by analyzing the experimental results. The strengths obtained by the experiments were also compared with those derived by the design code of the SC structures. One of the main failures of unstiffened SC shear walls was found to be the type of bending shear failure due to the debonding of the steel plate at the concrete interface. The ductility capacity of SC structures was also confirmed to be improved, which is considered to be a confining effect on steel plates in the longitudinal behavior of SC structures.

As increasing number of large-size earthquake around Korean peninsula, many interests have been focused to the earthquake strengthening of existing structures. Fiber reinforced plastic composite material is one of strengthening material widely used to increase seismic performance of structures. It should have high stiffness as well as large ductility to provide best strengthening result. Thus selection of stiffener and fiber in composite is of important. In this study, the optimal combination of fiber and stiffener is selected with variety of tensile tests. In order to investigate performance of chosen composite material, several finite element analyses are performed with proposed FRP composite material for existing RC columns. It is discussed that the seismic performance of strengthened columns through the load-displacement relationship. It is shown that the proposed composite material can increase the strength as well as ductility of exiting RC columns.

Many reinforced concrete structures have been constructed at the offshore in Korea and those are exposed in environments for long period. Due to that, the reinforcement of the structure faces possibility of corrosion by the salt damage. Such corrosions are effects on the bond performance between concrete and reinforcing bar as well as the performance of the structure. In this study, the performance of RC structure has been investigated when the reinforcing bars are totally bonded and unbonded in the structure. Through the experimental tests and finite element analyses of beam-column joint with bond and unbonded reinforcing bar, the energy dissipation capacity, strength, and crack distribution are compared and discussed.

The latest study for formulation of finite element method and computation techniques has progressed widely. The classical method in the formulation of frame elements for geometrically nonlinear analysis derives the geometric stiffness directly from the governing differential equation for bending with axial force. From the computational viewpoint of this paper, the most common approach is the finite element method. Commonly, the formulation of frame elements for geometrically nonlinear structures is based on appropriate interpolation functions for the transverse and axial displacements of the member. The formulation of flexibility-based elements, on the other hand, is based on interpolation functions for the internal forces. In this paper, a new method is used to suppose that interpolation functions for the displacements from the curvatures is Lagrangian interpolation. This paper derives flexibility matrix from that displacement functions and is considered the application of it. Using the flexibility matrix, this paper apply the program considered geometrically nonlinear analysis to common problems.

This study is to develop nonlinear analysis algorithm for transfer matrix method, which can be applied to continuous beam analysis. Gauss-Lobatto integral rule is adopted and the transfer matrix is derived from stiffness matrix. In the transfer matrix method, the system equation has a constant number of unknowns regardless of number of D.O.F. Therefore, the transfer matrix method has computational efficiencies not only in linear elastic analysis but also in nonlinear analysis. To verify the developed method, the analysis results of several examples are compared with commercial code in moment-curvature, moment-displacement and load-displacement relation.

Surface texturing with micro-dimples is a known method for friction reduction under lubricated sliding contact, and various machining techniques have been researched and developed in order to fabricate micro-dimple patterns. However, previous fabrication methods possess several problems, such as causing thermal damage on the workpiece or limiting the available workpiece geometry. In micro ECM, micro features can be machined without any resulting thermal or mechanical damage. From this perspective, micro ECM has certain advantages over surface texturing. Also, micro ECM is applicable to non-planar workpieces. In this research study, micro ECM with microsecond pulses was applied in order to fabricate a micro-dimple pattern. The machining characteristics were investigated in fabricating micro dimples on AISI 440C specimen. On the basis of the experimental results, a O 300 μm dimple pattern was successively produced on the AISI 440C specimen. A friction test on the textured specimen was performed and compared with a non-textured specimen. The enhancement of frictional performance was successfully demonstrated experimentally.

Infinite element approach has been widely used to analysis soil-structure interaction, in which the soil domain is treated as infinite domain. However, most of the developed infinite element has been formulated in the frequency domain rather than the time domain to include the frequency contents of the earthquake or vibration wave. Due to that, those approaches have a critical limitation which is restricted to the linear elastic analysis. To main objective of this research is to develop the infinite element in the time domain to cooperate the inelastic soil and structure behavior. Developed infinite element is verified with the results of finite element analysis modeled in large domain. The nonlinear analysis also conducted to demonstrate the application of developed infinite element. Hence, based on above-mentioned statements, it can be concluded that the propose approach would assist for structure-seismic design. Key Words : Infinite Element, Time Domain, Nonlinear 본 연구는 국토해양부 도시철도표준화2단계 연구개발사업의 연구비에 의해 수행되었습니다.

In this study, we examine the relationship between the number of tropical cyclones (TCs) in the western North Pacific and the tropical Pacific sea surface temperature (SST) during the main TC season (July–November) for the period of 1965–2006. Results show that there are periods when TC frequency and the tropical Pacific SST are well correlated and periods when the relationship breaks down. Therefore, decadal variation is readily apparent in the relationship between the TC frequency and the SST variations in the tropical Pacific. We further examine the oceanic and atmospheric states in the two periods (i.e., 1979–1989 vs. 1990–2000) when the marked contrast in the correlation between the TC frequency and the tropical Pacific SST is observed. Before 1990, the analysis indicates that oceanic conditions largely influenced anomalous TC frequency, whereas atmospheric conditions had little impact. After 1990, there the reverse appears to be the case, i.e., atmospheric conditions drive anomalous TC frequency and oceanic conditions are relatively unimportant. A role of atmosphere and ocean in relation to the TC development in the western North Pacific changes, which is consistent with the change of the correlations between the TC frequency and the tropical Pacific SST.

The dynamics of the melt-quenched amorphization in TiOx mixed Ge2Sb2Te5 films were studied using real-time reflectivity measurements with a nanosecond laser pulse and various amounts of TiOx. It was observed that the laser-power required for amorphization was significantly reduced by 27% when 9.1 mol% of TiOx was incorporated with Ge2Sb2Te5. The lowering of the thermal conductivity of the films, due to the increase in the number of interface between the Ge2Sb2Te5 and TiOx phases, led to an increase in the thermal efficiency. Such enhanced thermal efficiency is of great technological importance in phase change storage applications.

A nonvolatile memory technology utilizing reversible changes between fcc and hcp crystalline phases is proposed. In this new type of phase-change memory, data are stored in different forms of crystalline phases of (Ge/sub 1/Sb/sub 2/Te/sub 4/)/sub 0.8/(Sn/sub 1/Bi/sub 2/Te/sub 4/)/sub 0.2/ chalcogenide alloy. RESET operation produces the less conductive metastable fcc phase via melt-quenching from the more conductive stable hcp phase and SET operation involves a phase change from fcc directly to hcp. Both RESET and SET operations can be completed as fast as 70 ns with large changes in cell resistance.

ISI Document Delivery No.: 497SP Times Cited: 252 Cited Reference Count: 28 Cited References: Alexander MA, 2002, J CLIMATE, V15, P2205, DOI 10.1175/1520-0442(2002)0152.0.CO;2 An SI, 2000, J CLIMATE, V13, P2044, DOI 10.1175/1520-0442(2000)0132.0.CO;2 An SI, 2004, J CLIMATE, V17, P2399, DOI 10.1175/1520-0442(2004)0172.0.CO;2 Ashok K, 2007, J GEOPHYS RES-OCEANS, V112, DOI 10.1029/2006JC003798 Barsugli JJ, 2002, J CLIMATE, V15, P3427, DOI 10.1175/1520-0442(2002)0152.0.CO;2 Bejarano L, 2008, J CLIMATE, V21, P3051, DOI 10.1175/2007JCLI1679.1 CAYAN DR, 1992, J PHYS OCEANOGR, V22, P859, DOI 10.1175/1520-0485(1992)0222.0.CO;2 Cobb K., 2003, NATURE, V424, P272 EFRON B, 1982, JACKKNIFE BOOTSTRAP, P1 Fedorov AV, 2000, SCIENCE, V288, P1997, DOI 10.1126/science.288.5473.1997 Hoerling MP, 2002, J CLIMATE, V15, P2184, DOI 10.1175/1520-0442(2002)0152.0.CO;2 KALNAY E, 1996, B AM METEOROL SOC, V77, P471 Kao HY, 2009, J CLIMATE, V22, P615, DOI 10.1175/2008JCLI2309.1 Kug JS, 2009, J CLIMATE, V22, P1499, DOI 10.1175/2008JCLI2624.1 Kumar KK, 2006, SCIENCE, V314, P115, DOI 10.1126/science.1131152 Larkin NK, 2005, GEOPHYS RES LETT, V32, DOI 10.1029/2005GL022738 Latif M, 1997, J CLIMATE, V10, P2221, DOI 10.1175/1520-0442(1997)0102.0.CO;2 Meehl GA, 2007, B AM METEOROL SOC, V88, P1383, DOI 10.1175/BAMS-88-9-1383 RASMUSSON EM, 1982, MON WEATHER REV, V110, P354, DOI 10.1175/1520-0493(1982)1102.0.CO;2 Smith TM, 2004, J CLIMATE, V17, P2466, DOI 10.1175/1520-0442(2004)0172.0.CO;2 Solomon S, 2007, CLIMATE CHANGE 2007: THE PHYSICAL SCIENCE BASIS, P19 Trenberth KE, 2001, J CLIMATE, V14, P1697, DOI 10.1175/1520-0442(2001)0142.0.CO;2 TRENBERTH KE, 1987, MON WEATHER REV, V115, P3078, DOI 10.1175/1520-0493(1987)1152.0.CO;2 Vecchi GA, 2006, NATURE, V441, P73, DOI 10.1038/nature04744 Wang G, 2007, J CLIMATE, V20, P4211, DOI 10.1175/JCLI4228.1 Weng HY, 2007, CLIM DYNAM, V29, P113, DOI 10.1007/s00382-007-0234-0 Weng HY, 2009, CLIM DYNAM, V32, P663, DOI 10.1007/s00382-008-0394-6 Xie PP, 1997, B AM METEOROL SOC, V78, P2539, DOI 10.1175/1520-0477(1997)0782.0.CO;2 Yeh, Sang-Wook Kug, Jong-Seong Dewitte, Boris Kwon, Min-Ho Kirtman, Ben P. Jin, Fei-Fei KUG, JONG-SEONG/A-8053-2013 KORDI [PE98401, PP00720]; PCCC project; ANR (Agence Nationale de la Recherche); NSF [ATM 060552, AMT 065145]; NOAA [GC01-229] We acknowledge the international modelling groups for providing their data and PCMDI and the IPCC Data Archive at LLNL/DOE for collecting, archiving and making the data readily available. S.-W. Y. and J.-S. K. are supported by KORDI ( grants PE98401, PP00720). B. D. benefited from funding from the PCCC project ( Peru Chile Climate Change) of the ANR (Agence Nationale de la Recherche). J.- S. K. and F.- F. J. are also supported by NSF grants ATM 060552 and AMT 065145 and NOAA grant GC01-229. 262 NATURE PUBLISHING GROUP LONDON NATURE; El Nino events, characterized by anomalous warming in the eastern equatorial Pacific Ocean, have global climatic teleconnections and are the most dominant feature of cyclic climate variability on subdecadal timescales. Understanding changes in the frequency or characteristics of El Nino events in a changing climate is therefore of broad scientific and socioeconomic interest. Recent studies(1-5) show that the canonical El Nino has become less frequent and that a different kind of El Nino has become more common during the late twentieth century, in which warm sea surface temperatures (SSTs) in the central Pacific are flanked on the east and west by cooler SSTs. This type of El Nino, termed the central Pacific El Nino (CP-El Nino; also termed the dateline El Nino(2), El Nino Modoki(3) or warm pool El Nino(5)), differs from the canonical eastern Pacific El Nino (EP-El Nino) in both the location of maximum SST anomalies and tropical-midlatitude teleconnections. Here we show changes in the ratio of CP-El Nino to EP-El Nino under projected global warming scenarios from the Coupled Model Intercomparison Project phase 3 multi-model data set(6). Using calculations based on historical El Nino indices, we find that projections of anthropogenic climate change are associated with an increased frequency of the CP-El Nino compared to the EP-El Nino. When restricted to the six climate models with the best representation of the twentieth-century ratio of CP-El Nino to EP-El Nino, the occurrence ratio of CP-El Nino/EP-El Nino is projected to increase as much as five times under global warming. The change is related to a flattening of the thermocline in the equatorial Pacific.

Micromachining of internal features by electrochemical machining (ECM) is investigated. By controlling pulse conditions and using a customized tool electrode, micro features were machined on the side wall of a micro hole. In micro ECM, longer pulse on-time enlarges the side gap. A reverse tapered hole and a barrel-shape hole were fabricated through pulse duration control. Micro cavity was machined by controlling the pulse duration and machining time in similar manner. A micro disk-shape electrode was used to machine microgroove inside the hole, which is similar to turning lathe process.

Ge2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on amorphous phase. Many chalcogenides display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were also the result of photo-oxidation. The oxide has lower value of (n, k) than Ge2Sb2Te5, and can be etched by hydrofluoric acid or water. The photo-oxidation is presumably the result of free carrier generation in the Ge2Sb2Te5. Our observation of negligible photodarkening is consistent with previous works that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.

A new method of evaluating crystallization activation energy of Ge2Sb2Te5 is proposed by in situ resistance measurement under isothermal annealing conditions. Linear relationship between logarithmic time and reciprocal temperature in modified Johnson–Mehl–Avrami–Kolmogorov equation is derived under the assumption that proportion of resistance drop from the initial value is closely related to crystal fraction. Crystallization activation energy thus obtained is 2.67 eV. Numerical calculation was conducted to manifest the validity of this analysis based on percolation model. Moreover, crystallization behavior of patterned single-line structure of Ge2Sb2Te5 was evaluated, and the scaling effect of increasing activation energy with decreasing line width was observed.

Amorphous Ge 2 Sb 2 Te 5 clusters with a size of 20 nm, self-enclosed by a thin layer of TiO x , were obtained by cosputtering Ge 2 Sb 2 Te 5 and TiO 2 targets at room temperature with the aim of reducing the reset current for phase change random access memory applications. Eutectic decomposition during the deposition caused a phase separation of Ge 2 Sb 2 Te 5 and TiO x . The temperature-dependent resistance change results showed that the activation energy for crystallization increased from 2.44 ± 0.76 to 3.84 ± 1.43 eV in the Ge 2 Sb 2 Te 5 film. The set resistance can be tuned within an acceptable range, and the reliability of this microstructure during repetitive laser melt-quenching cycles was tested.

Nature 461, 511–514 (2009) In Figure 4 of this letter, the key for the 20C3M ensemble (red line) and the SRESA1B ensemble (blue line) were inadvertently mislabelled. The correct figure is shown below.

The chemical instability of line patterned Ge2Sb2Te5 was studied by transmission electron microscopy after electrically inducing melt and solidification. Compositional analysis showed elemental separation of Te to the anode side, while Ge and Sb mutually separated at the cathode side. Such elemental separation of Ge2Sb2Te5 is explained by the electric field effects and thermodynamic driving forces.

Nanometer scale Ge2Sb2Te5 (GST) domains formed by immiscible mixture of GST-SiOx at room temperature and 180 °C show remarkable suppression in electrical and thermal conductivity. Thermal boundary resistance with increased GST-SiOx interface becomes crucial to the reduction in thermal conductivity. These conductivity reductions concurrently result in the reduction in programming current and power consumption in phase change memory devices.

We report the breakdown behavior of a patterned Ge2Sb2Te5 multiline structure during the voltage-driven electric stress biasing. Scanning Auger microscope analysis shows that the breakdown process accompanies with a phase separation of Ge2Sb2Te5 into an Sb, Te-rich phase and a Ge-rich phase. The phase separation is explained by the incongruent melting of Ge2Sb2Te5 based on the pseudobinary phase diagram between Sb2Te3 and GeTe. It is claimed that this phase separation behavior by incongruent melting provides one of the plausible mechanisms of the device failure in a phase change memory.

The phase change material Ge2Sb2Te5 is widely investigated for use in nonvolatile memories. It has been reported that the crystallization speed depends on the thermal history, indicating that structural differences exist between amorphous states. The authors apply fluctuation electron microscopy to quantify differences in the nanometer-scale structural order between several amorphous states of Ge2Sb2Te5. All as-deposited films are found to contain ordered regions. Thermal annealing below the crystallization threshold increases the nanoscale order, and such samples crystallize slightly more rapidly. The authors hypothesize that the nanoscale ordered regions act as the nuclei for crystallization, with the largest regions being the most significant.

The thermal conductivity of thin films of the phase-change material Ge2Sb2Te5 is measured in the temperature range of 27°C

The electrical switching behaviors of an offset-type phase change memory device with a highly resistive TiON layer were investigated, where the TiON layer (7 nm thick) was formed at a 70 nm wide contact between Ge1Sb2Te4 and TiN layers. Reversible transitions between crystalline (set) and amorphous (reset) phases were found to occur at relatively lower reset and set voltages, as compared with a device having no TiON layer. These results hold a high promise for a low-power operation of a phase change memory device.