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T.J. Whitcher,K.H. Yeoh,C.L. Chua,K.L. Woon,N. Chanlek,H. Nakajima,T. Saisopa,P. Songsiriritthigul 한국물리학회 2014 Current Applied Physics Vol.14 No.3
The work function of indium tin oxide (ITO) was increased by treating ITO with dichlorobenzene with UV light. Carbon contamination of the Cl-ITO was measured using X-ray Photoelectron Spectroscopy (XPS) and argon ion sputtering was used to remove the carbon from the surface. It was found that the carbon contamination from residual dichlorobenzene significantly lowered the work function of the ITO and after argon ion sputtering the work function increased to 5.8 eV. It was found that chlorination of ITO occurs after more than 6 min of UV exposure. Further sputtering of ITO resulted in the removal of the functionalized chlorine, the introduction of argon ion contaminants on the ITO decreases its work function.
Novel Anisotropic Superconductivity in Silicides
T. Tamegai,G. J. Li,K. Uozato,T. Nakagawa,Y. Nakajima 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
The discovery of superconductivity with Tc ∽39 K in MgB2 renewed our interest in intermetalic compounds containing light elements. We have revisited superconductivity in anisotropic silicides, such as CaMSi (M = Al and Ga), R5Ir4Si10 (R: rare-earth elements), and Lu2Fe3Si5. In CaAlSi with the AlB2 structure, an anomalous angular dependence of the upper critical field is found, sugesting the presence of a decoupled superconducting region. An X-ray diffraction study has shown the presence of a pronounced superlatice structure along thec-axis. Magneto-optical observations on the ac-plane of CaAlSi reveal the presence of strong inhomogeneities. Most R5Ir4Si10 (R: Sc, Y, rare-earth elements) compounds show a charge-density wave instability with the ex- ception of Sc5Ir4Si10, which shows the highest Tc among these compounds. We have compared their anisotropic superconductivity in order to get some insight into the exceptional properties of Sc5Ir4Si10. Lu2Fe3Si5 is a superconductor with Tc ∽ 6 K and containing nonmagnetic iron. Previous specific heat measurements show that Lu2Fe3Si5 has a large residual density of state in the superconducting state. We have sucesfuly grown high-quality single crystals of Lu2Fe3Si5 and found a signature of the presence of a second superconducting gap as in MgB2.
Energy level alignment of blended organic semiconductors and electrodes at the interface
T.J. Whitcher,W.S. Wong,A.N. Talik,K.L. Woon,A. Rusydi,N. Chanlek,H. Nakajima,T. Saisopa,P. Songsiriritthigul 한국물리학회 2018 Current Applied Physics Vol.18 No.9
The energy level alignment of a blended mixture of organic semiconductors is often depicted as having a common vacuum level. However, this is not a universal phenomenon among the vast number of organic semiconductors that currently exist, as in many cases the energy levels align via the Fermi level. In this report, the energy level alignments of the mixtures; poly(9-vinylcarbazole) (PVK) and 2,7-bis(diphenylphosphoryl)-9,9′- spirobifluorene (SPPO13) and poly(3-hexylthiophene-2,5-diyl) (P3HT) and SPPO13, with varying SPPO13 concentrations, are measured. It was found that the blended systems exhibit two different vacuum levels with the dipole between the PVK and SPPO13 increasing with the SPPO13 concentration, whilst the P3HT and SPPO13 vacuum levels only experience a small change. This is attributed to the decreasing electronic screening with increasing SPPO13 concentration. These new observations have an important implication in our understanding of interfacial behaviour for blended systems commonly used in various organic electronic devices.
Tabletop laser-driven gamma-ray source with nanostructured double-layer target
Huang, T W,Kim, C M,Zhou, C T,Ryu, C M,Nakajima, K,Ruan, S C,Nam, C H IOP 2018 Plasma physics and controlled fusion Vol.60 No.11
<P>Laser-driven gamma-ray source potentially offers a compact, cost-effective, ultra-short, and ultra-bright alternative to conventional gamma-ray sources based on large-scale particle accelerators. Based on the laser-driven approach, we use multidimensional particle-in-cell simulations to demonstrate that a nanostructured double-layer target, which consists of a nanostructured foam coated on top of a metal substrate, can absorb laser energy into high-energy electrons in the nanostructured foam, and then efficiently convert it into copious gamma photons via the nonlinear Compton scattering process enabled by the solid-density substrate, which acts as a plasma mirror to reflect the laser pulse. The effects of different nanostructures in the foam target and the oblique laser incidence are presented. It is shown that the conversion efficiency of gamma photons increases when the size of nanoparticles decreases or the filling factor of nanoparticles increases in nanostructured foam target, but decreases when the laser incidence angle increases. At realistic conditions with nanostructured foam and non-normal incidence, the double-layer target still exhibits an unprecedentedly high conversion efficiency in high-energy gamma-ray production due to the laser reflection by the plasma mirror, which can be two and even three orders of magnitude higher than that of the single-layer target without the substrate using currently available lasers with intensity of 10<SUP>21</SUP> <img ALIGN='MIDDLE' ALT='${\rm{W}}/{\mathrm{cm}}^{2}$' SRC='http://ej.iop.org/images/0741-3335/60/11/115006/ppcfaadbebieqn1.gif'/>.</P>
HYDROPLANING ANALYSIS BY FEM AND FVM - EFFECT OF TIRE ROLLING AND TIRE PATTERN ON HYDROPLANING
Nakajima, Y.,Seta, E.,Kamegawa, T.,Ogawa, H. The Korean Society of Automotive Engineers 2000 International journal of automotive technology Vol.1 No.1
The new numerical procedure for hydroplaning has been developed by considering the following three important factors; fluid/structure interaction, tire rolling, and practical tread pattern. The tire was analyzed by FEM with Lagrangian formulation and the fluid is analyzed by FVM with Eulerian formulation. Since the tire and the fluid are modeled separately and their coupling is automatically computed by the coupling element, the fluid/structure interaction of the complex geometry such as the tire with the tread pattern can be analyzed practically. We verified the predictability of the hydroplaning simulation in the different parameters such as the water flow, the velocity dependence of hydroplaning, and the effect of the tread pattern on hydroplaning. In order to predict the streamline in the contact patch, the procedure of the global-local analysis was developed. Since the streamline could be predicted by this technology, we could develop the new pattern in a short period based on the principle; "make the stream line smooth".
A. NAKAJIMA,T. MAWATARI 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
Using a low viscosity synthetic traction oil and a low viscosity mineral oil with nearly equal viscosity grade of ISO VG 32, the effect of kind of oil on the fatigue life of bearing steel rollers was examined. A pair of rollers finished the contact surfaces to a mirror-like condition were driven under rolling with sliding conditions of s = -3.2% and a maximum Hertzian stress in the range of PH=2.8㎬~4.0㎬ was applied in point contact condition. As a result of experiments, the fatigue life with a mineral oil was longer than that with a traction oil under higher stress conditions above PH=3.4㎬. Based on the numerical calculation results of the thermal EHL which simulates the present experiment, the authors discuss the reason why such a difference in the fatigue life comes out.
HYDROPLANING ANALYSIS BY FEN AND FVM:EFFECT OF TIRE ROLLING AND TIRE PATTERN ON HYDROPLANING
Y. NAKAJIMA,E. SETA,T. KAMEGAWA,H. OGAWA 한국자동차공학회 2000 International journal of automotive technology Vol.1 No.1
The new numerical procedure for hydroplaning has been developed by considering the following three important factors; fluid/structure interaction, tire rolling, and practical tread pattern. The tire was analyzed by FEM with Lagrangian formulation and the fluid is analyzed by FVM with Eulerian formulation. Since the tire and the fluid arc modeled separately and their coupling is automatically computed by the coupling element. the fluid/structure interaction of the complex geometry such as the tire with the tread pattern can be analyzed praetically. We verified the predictability of the hydroplaning simulation in the different parameters such as the water flow, the velocity dependence of hydroplaning. and the effect of the tread pattern on hydroplaning. In order to predict the streamline in the contact patch. the procedure of the global-local analysis was developed. Since the streamline could be predicted by this technology, we could develop the new pattern in a short period based on the principle; "make the stream line smooth",<br/>
A Versatile IC Design & Current-Sense IGBT Match For Smart Modules
G.Majumdar,T.Nakajima,H.Iwamoto 전력전자학회 1989 ICPE(ISPE)논문집 Vol.- No.-
An integrated circuit and a new series of currrent sensing IGBT chips have been developed to meet the growing trend toward Power ICs. The new IC will directly drive and protect an n-channel current-sense type power MOSFET or IGBT under the direction of input. The IC is designed particularly for inverter circuit application where the power bridge is constituted by the above mentioned MOSPOWER devices of 10 to 50A and up to 600V class. This paper describes the details of the internal circuit design, the switching and protection performances of the new IC and the new IGBTs. The paper will also describe application and functionality of these devices in configuring typical inverter bridges on board or within modular housings where the IC is paired togetherwith the newly developed current-sense n-channel IGBT of 10 20A, 500V class.