• Journal of Powder Materials
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• v.21 no.3
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• pp.196-201
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• 2014

In this study, nanocrystalline Cu-Ni bulk materials with various compositions were cold compacted by a shock compaction method using a single-stage gas gun system. Since the oxide layers on powder surface disturbs bonding between powder particles during the shock compaction process, each nanopowder was hydrogen-reduced to remove the oxide layers. X-ray peak analysis shows that hydrogen reduction successfully removed the oxide layers from the nano powders. For the shock compaction process, mixed powder samples with various compositions were prepared using a roller mixer. After the shock compaction process, the density of specimens increased up to 95% of the relative density. Longitudinal cross-sections of the shock compacted specimen demonstrates that a boundary between two powders are clearly distinguished and agglomerated powder particles remained in the compacted bulk. Internal crack tended to decrease with an increase in volumetric ratio of nano Cu powders in compacted bulk, showing that nano Cu powders has a higher coherency than nano Ni powders. On the other hand, hardness results are dominated by volume fraction of the nano Ni powder. The crystalline size of the shock compacted bulk materials was greatly reduced from the initial powder crystalline size since the shock wave severely deformed the powders.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.4072-4089
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• 2018

This paper introduces a scheme for optimizing the material properties of mass-spring systems of different resolutions to provide coherent behavior for reduced level-of-detail in MSS(Mass-Spring System) meshes. The global optimal material coefficients are derived to match the behavior of provided reference mesh. The proposed method also gives us insight into levels of reduction that we can achieve in the systematic behavioral coherency among the different resolution of MSS meshes. We obtain visually acceptable coherent behaviors for cloth models based on our proposed error metric and identify that this method can significantly reduce the resolution levels of simulated objects. In addition, we have confirmed coherent behaviors with different resolutions through various experimental validation tests. We analyzed spring force estimations through triangular Barycentric coordinates based from the reference MSS that uses a Gaussian kernel based distribution. Experimental results show that the displacement difference ratio of the node positions is less than 10% even if the number of nodes of $MSS^{sim}$ decreases by more than 50% compared with $MSS^{ref}$. Therefore, we believe that it can be applied to various fields that are requiring the real-time simulation technology such as VR, AR, surgical simulation, mobile game, and numerous other application domains.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.14-18
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• 2004

High levels of ambient noise and safety factors often limit the use of 'active-source' seismic methods for geotechnical investigations in urban environments. As an alternative, shear-wave velocity-depth profiles can be obtained by treating the background microtremor wave field as a stochastic process, rather than adopting the traditional approach of calculating velocity based on ray path geometry from a known source. A recent field test in Melbourne demonstrates the ability of the microtremor method, using only Rayleigh waves, to resolve a velocity inversion resulting from the presence of a hard, 12 m thick basalt flow overlying 25 m of softer alluvial sediments and weathered mudstone. Normally the presence of the weaker underlying sediments would lead to an ambiguous or incorrect interpretation with conventional seismic refraction methods. However, this layer of sediments is resolved by the microtremor method, and its inclusion is required in one-dimensional layered-earth modelling in order to reproduce the Rayleigh-wave coherency spectra computed from observed seismic noise records. Nearby borehole data provided both a guide for interpretation and a confirmation of the usefulness of the passive Rayleigh-wave microtremor method. Sensitivity analyses of resolvable modelling parameters demonstrate that estimates of shear velocities and layer thicknesses are accurate to within approximately $10\%\;to\;20\%$ using the spatial autocorrelation (SPAC) technique. Improved accuracy can be obtained by constraining shear velocities and/or layer thicknesses using independent site knowledge. Although there exists potential for ambiguity due to velocity-thickness equivalence, the microtremor method has significant potential as a site investigation tool in situations where the use of traditional seismic methods is limited.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.6-6
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• 1994

Har dmaterials such as cemented carbides with or without coated layer, cermets, ceramics and diamond or c-BN high pressure sintered compact are used for cutting tools, wear -resistant parts, rock drilling bits and/or high pressure vessels. These hardmaterials contain not only hard phase, but also second consituent as the element for forming ductile phase and/or sintering aid, and the mechanical properties of each material depend on (1) the amount of the second constituent as well as (2) the grain size of the hard phase. The hardness of each material mainly depends on these two factors. The fracture strength, however, largely depends on other microstructur a1 factors as well as the above two factors. For all hardmaterials, the fracture strength is consider ably affected by (3) the size of microstructur a1 defect which acts as the fracture source. In cemented carbides, the following factors which are generated mainly due to the addition of the second constituent are also important; (4) the variation of the carbon content in the normal phase region free from V-phase and graphite phase, (5) the precipitation of $Co_3$ during heating at about $800^{\circ}C$,(6) the domain size of binder phase, and (7) the formation of ${\beta}$-free layer or Co-rich layer near the surface of sintered compacts. For cemented carbides coated with thin hard substance, the important factors are as follows; (8) the kind of coated substance, (9) the formation of ${\eta}$-phase layer at the interface between coated layer and substrate, (10) the type of residual stress (tension or compression) in the coated layer which depends on the kind of coating method (CVD or PVD), and (11) the properties of the substrate, and (12) the combination, coherency and periodicity of multi-layers. In the lecture, the details of these factors and their effect on the strength will be explained.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.47-58
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• 2005

Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.224-227
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• 2009

Nanofabrication is an essential process throughout industry. Technologies that produce general nanofabrication, such as e-beam lithography, dip-pen lithography, DUV lithography, immersion lithography, and laser interference lithography, have drawbacks including complicated processes, low throughput, and high costs, whereas nano-transfer printing (nTP) is inexpensive, simple, and can produce patterns on non-plane substrates and multilayer structures. In general nTP, the coherency of gold-deposited stamps is strengthened by using SAM treatment on substrates, so the gold patterns are transferred from stamps to substrates. However, it is hard to apply to transfer other metallic materials, and the existing nTP process requires a complicated surface treatment. Therefore, it is necessary to simplify the nTP technology to obtain an easy and simple method for fabricating metal patterns. In this paper, asnTP process with poly vinyl alcohol (PVA) mold was proposed without any chemical treatment. At first, a PVA mold was duplicated from the master mold. Then, a Mo layer, with a thickness of 20 nm, was deposited on the PVA mold. The Mo deposited PVA mold was put on the Si wafer substrate, and nTP process progressed. After the nTP process, the PVA mold was removed using DI water, and transferred Mo nano patterns were characterized by a Scanning electron micrograph (SEM) and Energy Dispersive spectroscopy (EDS).

• The KIPS Transactions:PartB
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• v.10B no.3
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• pp.321-328
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• 2003

This Paper Proposes a size-variable block matching algorithm for motion vector extraction. The Proposed algorithm dynamically determines the search area and the size of a block. We exploit the constraint of small velocity changes of a block along the time to determine the origin of the search area. The range of the search area is adjusted according to the motion coherency of spatially neighboring blocks. The process of determining the sire of a block begins matching with a small block. If the matching degree is not good enough, we expand the size of a block a little bit and then repeat the matching process until our matching criterion Is satisfied. The experimental results show that the proposed algorithm can yield very accurate block motion vectors. Our algorithm outperforms other algorithms in terms of the estimated motion vectors, though our algorithm requires some computational overhead.

• Journal of Korea Foundry Society
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• v.22 no.3
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• pp.109-113
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• 2002

A good fluidity of high strength Al-alloys is required to cast thin wall castings needed to reduce the weight of cast parts. The fluidity, measured as the length to which the metal flows in a standard channel, is affected by many factors, such as the pouring temperature, solidification type of the alloy, the channel thickness, melt head, mold materials and temperature, coating etc. Therefore the experimentally measured fluidity scatters very much and makes it difficult to estimate the fluidity of a melt with a few measurements. The effect of Ti content and grain refinement on the fluidity of high strength aluminum alloy was investigated with a test casting with 8 thin flow channels to reduce the scattering of the fluidity results. The fluidity of Al-4.8%Cu-0.6%Mn Al-6.2%Zn-1.6%Mg-1.0%Cu and well-known commercial aluminum alloy, A356 was tested. Initial content of Ti was varied from 0 to 0.2wt% and Al-5Ti-B master alloy was added for grain refinement. The flow length varied linearly with superheat. By adding Ti and Al-5Ti-B, the fluidity increased. The grain size decreased by adding grain refiner at the same time. The fluidity depended on the degree of grain refinement. The fluidity of the alloy solidifying in mushy type is improved by grain refinement, because grain refinement increases the solid fraction at the time of flow stoppage.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.12
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• pp.716-725
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• 2004

It is extremely important to minimize network access time in constructing a high-performance PC cluster system. For PC cluster systems, it is possible to reduce network access time by maintaining network cache in each cluster node. This paper presents a Network Cache Coherent NUMA (NCC-NUMA) system to utilize network cache by locating shared memory on the PCI bus, and the NCC-NUMA card which is core module of the NCC-NUMA system is developed. The NCC-NUMA card is directly plugged into the PCI slot of each node, and contains shared memory, network cache, shared memory control module and network control module. The network cache is maintained for the shared memory on the PCI bus of cluster nodes. The coherency mechanism between the network cache and the shared memory is based on the IEEE SCI standard. According to the SPLASH-2 benchmark experiments, the NCC-NUMA system showed improvements of 56% compared with an SCI-based cluster without network cache.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.115-119
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• 2001

The electrical properties of heavily drawn bundled Cu- Nb filamentary microcomposite wires were examined and correlated with the microstructural changes caused by thermomechanical treatments. The cross sectional shape of Nb filaments in wires fabricated by bundling and drawing appear straight or slightly curved. The different shape of Nb filaments is attributed to the break- up and cylinderization of Nb filaments during the bundling process at high temperatures. The resistivity of Cu-Nb microcomposites is predominantly controlled by electron scattering at Cu-Nb interfaces. The decrease of the conductivity below the annealing temperature of $400^{\circ}C$ is due to the increasing contribution of the scattering associated with coherency strains of needle- shaped precipitates. The slight decrease of the resistivity ratio (${\rho}_{295K}/{\rho}_{75K}$) is also due to the precipitation of Nb atoms. The increase in conductivity in Cu-Nb microcomposites at an annealing temperature of 50$0^{\circ}C$ is due to the coarsening and spheroidization of Nb filaments.