• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.5
• /
• pp.585-590
• /
• 2011

Accelerometers have been exploited widely in various fields from monitoring vibration of precision machines to detecting an earthquake wave. The precision calibration of the accelerometers is required to maintain the measurement reliability when measuring the vibration of objects with accelerometers for modal analysis. Among evaluation factors for determining sensitivity of accelerometers, phase delay term should be also considered for accurate calibration. In this paper, a new calibration system of accelerometers capable of measuring phase delay as well as magnitude of its sensitivity was proposed and realized in the frequency range of 20 Hz to 5 kHz.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.818-821
• /
• 2002

The grain boundary resistivity of a 1-mol%-$Al_2O_3$-dopedd CaO-Stabilized Zirconia(CSZ) specimen was determined by impedance spectroscopy using sub-millimeter-scale electrodes. At the initial stage of sintering, the grain-boundary resistivity of the specimen interior was observed to be higher than that of the surface. However, upon further sintering the boundary resistivity of the specimen interior became lower than that of the surface. The results were explained in terms of a redistribution of the intergranular liquid phase. The liquid phase was predicted to initially coagulate at the interior of the specimen then spread outward during sintering.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.30 no.2
• /
• pp.147-151
• /
• 2004

This study aims at measuring electrical and rheological properties of cosmetic emulsions on the skin under shear flow. The effects of volume ratio and surfactants on structural changes of emulsions were examined by determining the changes of electrical resistance, viscosity, and morphology. As the ratio of the internal phase increased, the phase inversion occurred more quickly. The viscosity change was found to increase with increasing of the variation of electrical resistance of the emulsions. This phenomenon may be caused by decreased resistant force against the shear flow because of the breakdown of the internal phase. Surfactants a]so played a key ro]e on phase transition of emulsions. It is likely that polymeric surfactants anchoring on the emulsion surface reinforced the interfacial mechanical strength. As the concentration of surfactants increased, the phase transition occurred more slowly. It has been demonstrated that the phase changes of emulsions under shear flow can be monitored on the real-time basis by using a JELLI$\^$TM/ chip system, a combination of conductiometry and rheometry. Our approach is expected to a useful experimental tool for predicting the phase transition of the cosmetic products during skin application.

• Korean Journal of Metals and Materials
• /
• v.49 no.2
• /
• pp.145-152
• /
• 2011

Mechanical and property corrosion resistance of Mg-Zn-Y alloys with an atomic ratio of Zn/Y of 6.8 are investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, uniaxial tensile test and corrosion test with immersion and dynamic potentiometric tests. The alloys showed an in-situ composite microstructure consisting of ${\alpha}$-Mg and icosahedral phase (I-phase) as a strengthening phase. As the volume fraction of the I-phase increases, the yield and tensile strengths of the alloys increase while maintaining large elongation (26~30%), indicating that I-phase is effective for strengthening and forms a stable interface with surrounding ${\alpha}$-Mg matrix. The presence of I-phase having higher corrosion potential than ${\alpha}$-Mg, decreased the corrosion rate of the cast alloy up to I-phase volume fraction of 3.7%. However further increase in the volume fraction of the I-phase deteriorates the corrosion resistance due to enhanced internal galvanic corrosion cell between ${\alpha}$-Mg and I-phase.

• Journal of Powder Materials
• /
• v.30 no.5
• /
• pp.402-408
• /
• 2023

This study focused on improving the phase stability and mechanical properties of yttria-stabilized zirconia (YSZ), commonly utilized in gas turbine engine thermal barrier coatings, by incorporating Gd₂O₃, Er₂O₃, and TiO₂. The addition of 3-valent rare earth elements to YSZ can reduce thermal conductivity and enhance phase stability while adding the 4-valent element TiO₂ can improve phase stability and mechanical properties. Sintered specimens were prepared with hot-press equipment. Phase analysis was conducted with X-ray diffraction (XRD), and mechanical properties were assessed with Vickers hardness equipment. The research results revealed that, except for Z10YGE10T, most compositions predominantly exhibited the t-phase. Increasing the content of 3-valent rare earth oxides resulted in a decrease in the monoclinic phase and an increase in the tetragonal phase. In addition, the t(400) angle decreased while the t(004) angle increased. The addition of 10 mol% of 3-valent rare-earth oxides discarded the t-phase and led to the complete development of the c-phase. Adding 10 mol% TiO₂ increased hardness than YSZ.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.186-186
• /
• 2017

Relay intercropping system of direct seeded rice and winter cereal is labor saving cultivation and has high land use efficiency in Japan. In this system, rice seeds are direct seeded into inter-row space of winter cereals (wheat or barley) in March or April. If the direct seeding of rice is conducted before stem elongation phase or using suitable seeder, these are little effect to yield of winter cereals. Though the seeds are generally thiuram treated, it's a matter that seedling establishment rate (SER) of direct seeded rice is low and unstable. The cause of low SER has not been revealed. In present study, with the aim to reveal causes of low SER, we conducted experiments and investigated the SER, and analyzed some factors that might affect SER. Experiment1: In 2015, 2016, we buried rice seeds underground, and investigated the transition of the seed survival rates (SSR). Seeds were thiuram-treated or non-treated. In 2 periods, SSR of thiuram-treated seeds were significantly higher than non-treated seeds. In 2016, thiuram-treated seeds were high in SSR (almost 75%) at April 30th, but low SER (10~27%) after harvest of winter cereals. Therefore, almost all of seed death might have been happen after germination. Analysis 1: We investigated the SER and cultivation conditions in Ibaraki pref. for several years. Meteorological factors were referred from the nearest point of AMeDAS. From mean temperature (MT) among 5days after and before the day, we divided the period of seeding ~June 20 to phase1~4. We defined each phase as below; Phase1: $MT{\leq}10^{\circ}C$, Phase2: $10^{\circ}C<MT{\leq}15^{\circ}C$, Phase3:$15^{\circ}C<MT{\leq}20^{\circ}C$, Phase4: $MT>20^{\circ}C$. We analyzed the correlation of SER and meteorological factors by each phase. Total number of days in phase 1~4 was significantly negative correlated with SER. In phase1, total rain fall and number of soil wetting days were significantly negative correlated with SER. In phase2~4, only MT was significantly positive correlated with SER. This result suggested that rainfalls in phase1 declined seed vigor to emergence from soil surface, by repeated water absorption and re-dry. From these present studies, it was suggested that one of factors of low SER of direct seeded rice in relay intercropping system is changing of water condition by rainfalls in phase1 ($MT{\leq}10^{\circ}C$). To improve SER, it's necessary to consider something seed treatments such as prevent water absorption during phase1. However, 58~60% of seeds seemed to die during May. It's suggested that, if seeds are thiuram treated, almost all of seeds can germinate underground, but the seed vigor to emergence from soil surface are insufficient. Further studies are needed to reveal the rest causes that is happening during emergence from soil surface.

• Journal of Powder Materials
• /
• v.23 no.5
• /
• pp.353-357
• /
• 2016

In this study, $TiO_2$ powders are synthesized from ammonium hexafluoride titanate (AHFT, $(NH_4)_2TiF_6$) as a precursor by heat treatment. First, we evaluate the physical properties of AHFT using X-ray diffraction (XRD), particle size analysis (PSA), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FE-SEM). Then, to prepare the $TiO_2$ powders, is heat-treated at $300-1300^{\circ}C$ for 1 h. The ratio of anatase to rutile phase in $TiO_2$ is estimated by XRD. The anatase phase forms at $500^{\circ}C$ and phase transformation to the rutile phase occurs at $1200^{\circ}C$. Increase in the particle size is observed upon increasing the reaction temperature, and the phase ratio of the rutile phase is determined from a comparison with the calculated XRD data. Thus, we show that anatase and rutile $TiO_2$ powders could be synthesized using AHFT as a raw material, and the obtained data are utilized for developing a new process for producing high-quality $TiO_2$ powder.

• Proceedings of the KIPE Conference
• /
• 2008.06a
• /
• pp.103-105
• /
• 2008

In grid-interconnection system, a fast, robust and precise phase angle detector is most important to grid synchronization and the active power control. The phase angle can be easily estimated by synchronous dq PLL system. On the other hand under unbalanced voltage condition, synchronous dq PLL system has problem that harmonics occur to phase angle or magnitude of grid voltage because of the effect of the negative sequence components. So, To eliminate the negative sequence components, the PLL method using APF (All Pass Filter) in a stationery reference frame to extract positive sequence components under unbalanced voltage condition is researched. In this paper, we propose a new PLL method with decoupling network using APF in a synchronous reference frame to extract the positive sequence components of the grid voltage under unbalanced grid. The cut-off frequency of APF in a synchronous reference frame can be set to twice of the fundamental frequency comparing with that of APF in a stationery reference frame which is the fundamental frequency. The proposed PLL strategy can detect the phase angle quickly and accurately under unbalanced gird voltages. Simulation and experimental results are presented to verify the proposed strategy under different kind of voltage dips.

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.183-189
• /
• 2014

Purpose : Intravenous contrast medium is a substance used to enhance the contrast of normal tissues or malignant tissues within the body. For this reason, intravenous contrast media have been extensively used form treatment-planning CT. However, when the patient is receiving proton therapy, there is no contrast medium in that moment. In this study, evaluate the influence of intravenous contrast medium on proton range and Spread-Out Bragg peak(SOBP) in Treatment Planning System(TPS). Materials and Methods : Hounsfield Unit(HU) value were measured by 20 liver cancer patients with phase change. and evaluate the proton range and SOBP on 5 liver proton treatment plan. By using the hand made water phantom measure the proton range and SOBP on proton treatment plan with changing HU and Depth. Results : Changing value(Pre contrast, Arterial phase, Portal phase) in liver cancer patient were ($58{\pm}5.7$, $75{\pm}9.5$, $117{\pm}14.6$ for liver tissue) and ($40{\pm}6.1$, $279{\pm}49.0$, $154{\pm}22.8$ for aorta), respectively. The mean difference of range was 2.5mm and SOBP was 1.4mm according to HU change. In phantom study, proton range was shorter and SOBP was narrowed with increasing HU. Conclusion : We verify that HU change lead to range and SOBP change in TPS. Additional study is required to verify that change of HU make range and SOBP be changed in actual substance.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.12
• /
• pp.2935-2937
• /
• 2009

Asymmetric glycolate alkylation reactions in the solid phase were investigated for the first time with good stereoselectivities being obtained by using a Wang resin supported 2-imidazolidinone chiral auxiliary.