Ha Tae Kyun

CuO nanoparticles, Cu₂O/CuO and CuO/TiO₂ nanocomposites exhibit excellent photocatalyst properties toward the degradation of methyl-orange and potassium-dichromate under the visible light irradiation.

The first experimental study is presented of a corrugated wall device that uses wakefields to remove a linear energy correlation in a relativistic electron beam (a "dechirper"). Time-resolved measurements of both longitudinal and transverse wakefields of the device are presented and compared with simulations. This study demonstrates the feasibility to employ a dechirper for precise control of the beam phase space in the next generation of free-electron-lasers.

Ce1-xEuxO2 (0 ≤x≤ 0.3) nanoparticles (NPs) were synthesized by the chemical precipitation method. The microstructures and morphology were characterized by synchrotron X-ray diffraction and high resolution transmission electron microscopy. X-ray absorption near edge structure (XANES) spectra at the Eu M5,4-edge and atomic-multiplet calculations revealed that Eu(3+) was predominantly present in the CeO2 lattice and Eu(2+) was negligibly present within the entire doping range. The detailed analysis

Single phase nanoparticles (NPs) of CeO2, Ce0.5Zr0.5O2, Ce0.5Hf0.5O2 and Ce0.5Hf0.25Zr0.25O2 were successfully synthesized by co-precipitation method at constant pH and temperature. The X-ray diffraction results revealed that the additive atoms did not segregate to form secondary phases but led to grain size variation in the NPs. The 10 Dq values in the near edge X-ray absorption fine structure (NEXAFS) spectra at the O K-edge did not vary in the same way as the average grain size was changed fo

After 14 years of successful operation, the Pohang Light Source (PLS) has completed PLS-II upgrade to meet the increasing demand from the growing user community. The PLS-II upgrade has increased the beam energy from 2.5 GeV to 3 GeV; the number of insertion devices has been increased by a factor of two (20 IDs); and the beam current has been increased to 400 mA from 200 mA. The beam emittance has been reduced to below 10 nm while retaining the existing PLS tunnel as well as the existing injectio

Outgassing rates of three low-carbon steels were measured using rate-of-rise and throughput methods. Outgassing rates of water vapor during pump-down were higher than those of stainless steels, probably due to the nature of native surface oxide layer. However, hydrogen outgassing rates without a high temperature pretreatment were as low as (1–4) × 10−10 Pa m3 s−1 m−2, which is much lower than that of untreated stainless steels. No dramatic reduction was observed in H2 outgassing after vacuum ann

ZrO2 and HfO2 powder samples were prepared by using the chemical precipitation method and subsequent annealing. Crystal structure, local electronic structure and dielectric constant of amorphous and crystalline powders of ZrO2 and HfO2 have been examined using the synchrotron X-ray diffraction, O K-edge X-ray absorption spectroscopy, Zr 3d and Hf 4f core-level X-ray photoelectron spectroscopy and temperature dependent dielectric measurements, respectively. Amorphous ZrO2 and HfO2 powders exhibit

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Transient CCl3+: Its Optical Absorption and Its Ability To Form Ion Pairs in Methylcyclohexane Solution of CCl4J. L. Gebicki, A. S. Domazou, T.-K. Ha, G. Cirelli, and R. E. BuehlerCite this: J. Phys. Chem. 1994, 98, 38, 9570–9576Publication Date (Print):September 1, 1994Publication History Published online1 May 2002Published inissue 1 September 1994https://doi.org/10.1021/j100089a034Request reuse permissionsArticle Views60Altmetric-Citations11LEARN

The authors performed simulations of Penning discharge at the low magnetic field using a particle-in-cell computer code to derive the optimum cell geometry of a sputter ion pump (SIP). The energy and angle distributions of incident ions on the cathode of a Penning cell were directly obtained from the simulation. Based on these data, the authors calculated the amount of deposited Ti on the inner surface of the cell, which was found to be proportional to intrinsic pumping speed of a SIP, and then

We report detailed investigations on the electronic structure and photocatalyst application of CuO and Cu0.9Ti0.1O nanoparticles (NPs). The NPs were prepared by co-precipitation method and subsequent annealing. Crystal structure and morphology of the NPs were investigated by synchrotron X-ray diffraction and high resolution transmission electron microscope, respectively. The local atomic structure around the Cu atoms was investigated by the extended X-ray absorption fine structure (EXAFS) at the

After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum

We present a numerical method of calculating the pressure profile of a large ultra-high vacuum (UHV) system using finite-element analysis (FEA) that exploits the continuity of gas flow. In this study, we introduce a modified FEA (MFEA) that excludes the redundant count of aperture conductance of the element by the Oatley method and uses a correction factor compensating the beaming effect. Along with the correction and by choosing an appropriate length of the element, we improve the result for a

PLS-II [1-4] as been operated successfully since 21<SUP>st</SUP> March 2012. Since a 3 GeV linear accelerator is used as a full energy injector, the performance of the linear accelerator is critical for reliable user service. Although the PLS-II linear accelerator shows full reliability without interrupting user service during the first half year, there is always the possibility for failure of the 3 GeV linear accelerator system. For instance, any of the many pulsed high power supplies may fail.