• Tribology and Lubricants
• /
• v.17 no.1
• /
• pp.40-55
• /
• 2001

Acoustic emission(AE) signal has been widely utilized to monitor the interaction at the head/disk interface. In this work the relationship between the AE signal and the state of contact between the slider and the disk is presented. Results of the FFT(Fast Fourier Transform) analyses of the AE signal could be used to better understand the interfacial interaction. Also, it was found that wear particles affect the AE signal. Therefore, the signal can be used to monitor the wear particle presence at the interface.

• Journal of Mechanical Science and Technology
• /
• v.15 no.3
• /
• pp.281-290
• /
• 2001

Particle contamination has been an ongoing problem affecting the reliability of the magnetic hard disk drives. Especially the recent use of MR head requires much tighter control of particle contamination due to thermal asperity (TA) phenomenon. In this study, the effects of slider air bearing surface design of TA reduction capability were investigated by manufacturing two types of sliders. Numerical methods were used to simulate the motion of particles in the head/media interface. Experiments were conducted to verify the results predicted by the numerical simulation. Drives were built and exposed to particle contamination using a particle injection chamber, which turned out to be a very simple and reliable particle generation method over conventional aerosol technique. Then the number of TA generated in the drives was recorded and compared. Also the contacts between slider and particles were investigated by acoustic emission study. It was found that a new ABS design, which has aerodynamic U-shaped rail and central flow passage, was beneficial in reducing the particle contamination on the slider.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.11
• /
• pp.932-938
• /
• 2017

Particle-in-cell method which blends Eulerian grids and Lagrangian particle is utilized to solve simplified hall-effect thruster. Since this study individually tracks not only neutrons and ions but also electrons, message passing interface(mpi) scheme is adopted for parallel computer cluster. Helical movement of an electron cloud in constant magnetic field is validated comparing with an exact solution. A plasma in radial magnetic field and axial electric field in a reaction cylinder is established. Electrons do double helix movement and are well anchored in a cylinder. Ionization of neutrons by impact with high-speed electrons generates ion particles. They are accelerated by axial electric field, which forms a plume of a plasma-effect thruster.

• Journal of the Korean Ceramic Society
• /
• v.26 no.5
• /
• pp.617-624
• /
• 1989

Piezoelectric composites of O-3 connectivity were prepared by thermosetting barium titanate-phenolic resin composite under various cruing pressure. Among three kinds of pore in O-3 type ceramic-polymer composite, such as matrix pores, particle pores, and ceramic-polymer interface pores, the effect of interface porosity on the dielectric and piezoelectric constant was investigated. In pure barium titanate ceramics, the porosity factor of dielectric and piezoelectric constants were 5.7 and 5.0, respectively. However, in BaTiO3-polymer composite, the interface porosity factor of the piezoelectric constant was greater than that of the dielectric constant, interface porosity factor b in d33 was 9.8 and in r 4.6. On the other, piezoelectric voltage constant g33 was independent of the porosity of barium titanate ceramics. But in composite system, the piezoelectric voltage constant g33 was decreased with interface porosity.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.684-689
• /
• 2008

In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.

• Journal of Adhesion and Interface
• /
• v.3 no.4
• /
• pp.19-26
• /
• 2002

In order to study the toughening mechanism of rubber modified polycarbonate, the sequence of development of micro-voids was investigated by real-time small angle X-ray scattering with Synchrotron radiation (SR-SAXS). The used test method was wedge test. The scattering intensity increases with increasing penetration depth of wedge, i.e. applied strain. The increase is due to the micro-void formation during deformation. This micro-void was uniformly developed in matrix and was different from large-void due to internal cavitation of rubber particle and/or debonding between rubber particle and polycarbonate matrix. The micro-void was developed at the critical strain and the radius of micro-void is around $600{\AA}$. Above the critical strain the size of micro-void remains almost constant with increasing applied strain. However, the population of micro-void increased with applied strain.

• International Journal of Concrete Structures and Materials
• /
• v.8 no.4
• /
• pp.269-278
• /
• 2014

When concrete is being transported through a pipe, the lubrication layer is formed at the interface between concrete and the pipe wall and is the major factor facilitating concrete pumping. A possible mechanism that illustrates to the formation of the layer is the shear-induced particle migration and determining the rheological parameters is a paramount factor to simulate the concrete flow in pipe. In this study, numerical simulations considering various rheological models in the shear-induced particle migration were conducted and compared with 170 m full-scale pumping tests. It was found that the multimodal viscosity model representing concrete as a three-phase suspension consisting of cement paste, sand and gravel can accurately simulate the lubrication layer. Moreover, considering the particle shape effects of concrete constituents with increased intrinsic viscosity can more exactly predict the pipe flow of pumped concrete.

• Journal of Adhesion and Interface
• /
• v.11 no.1
• /
• pp.9-14
• /
• 2010

O/W emulsions were prepared with the phase inversion emulsification methods. The emulsifiers were used the UNIQ-1 (isopropylamine alkyl aryl sulphonate) and UNIQ-2 (alkoxylated glycol ether). Investigated effect that HLB value, agitator velocity and manufacture temperature get in mean particle size of emulsions. Mean particle size receives much effect of HLB value. Also, estimated stability about storage temperature and light. Emulsion's mean particle size was 193 nm lastly, reduced VOC amount used 90% than existing alkyd resin.

• Applied Chemistry for Engineering
• /
• v.28 no.1
• /
• pp.125-131
• /
• 2017

We report organically functionalized Ag nanoparticles spontaneously form two-dimensional (2D) novel superstructures at the air-water interface. Analysis of the superstructures suggests that the 2D assembly of Ag nanoparticles originates from a subtle interplay between characteristic inter-particle interactions that can be readily controlled by changing the sizes of nanoparticle metal core and surfactants. Such structures have potential uses in nanostructured functional materials, catalysis, and device applications.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2003.05a
• /
• pp.381-384
• /
• 2003

실제 게임에서는 파티클 시스템을 사용하여 대부분의 특수효과들 (비, 불, 안개, 폭발, 분수 둥...) 을 만들어낸다 파티클 효과를 간편하게 게임안에 삽입하기 위한 전용 에디터를 사용하기도 하는데, 이것을 좀더 편리하게 만들어 보고자 하는데 본 논문의 초점이었다. 본 논문에서는 강화된 인터페이스를 가진 파티클 시스템을 만들어 보다 편리하게 효과를 생성하고 삽입하고자 한다. 기본적으로 매우 직관적인 효과들을 편리하게 표현해보고자 하는 의도에서 만들어진 것으로, 직관적으로 보이는 곡선을 그려 파티클의 이동경로를 미리 지정해주고 몇 가지 요소들을 제거함으로써 완전한 기존의 파티클 시스템과는 약간의 차별성을 두었다.