• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.159-163
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• 2010

Co-(0.5 mol%) and Ce-(0~0.3 mol%) doped cubic zirconia ($ZrO_2:Y_2O_3$=64:36 mol%) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1200^{\circ}C$ for 3 hrs. The brown-colored as-grown single crystals were changed into either green or blue color after the heat treatment. Before and after the heat treatment, the YSZ (yttriastabilized zirconia) single crystals were cut for wafer form (${\phi}7mm{\times}t2mm$) and round brilliant cut ($\phi$ 12 mm). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Ce^{3+}(^2F_{5/2},\;_{7/2}(4f){\rightarrow}^2T_g(5d^1)),\;Co^{2+}(^4A_2(^4F){\rightarrow}^4T_1(^4F)$ or $^4T_1(^4P))$ and $Co^{3+}$, change of ionization energy and lattice parameter were confirmed.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.328-334
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• 2001

The characteristics of $NO/N_2O$ nitrided oxide and reoxidized nitrided oxide being studied as super thin gate oxide and gate dielectric layers of nonvolatile semiconductor memory(NVSM) was investigated by dynamic secondary ion mass spectrometry(D-SMS), time-of-flight secondary ion mass spectrometry(ToF-SIMS), and x-ray photoelectron spectroscopy (XPS). The specimen was annealed in $NO/N_2O$ ambient after initial oxide process. The result of D-SIMS exhibits that the center of nitrogen exists at the initial oxide interface and the distribution of nitrogen is wider in the annealing process with $N_2O$ than with NO annealing process. For investigating the condition of nitrogen that exists within the nitrided oxide, ToF-SIMS and XPS analysis were carried out. It was shown that the center of nitrogen investigated by D-SIMS was expected the SiON chemical bonds. The nitrogen near the newly formed reoxide/silicon substrate interface was appeared as $Si_2NO$ chemical bonds, and it is agreed with the distribution of SiN and $Si_2NO$ species by ToF-SIMS.

• Advances in nano research
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• v.15 no.1
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• pp.1-13
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• 2023

Ti₃C₂T_x MXene, a 2D material, is known to exhibit unique characteristics that are strongly dependent on surface termination groups. Here, we developed a novel annealing approach with Ca as a reducing agent to simultaneously remove F and O groups from the surface of multilayered MXene powder. Unlike H₂ annealing that removes F effectively but has difficulty in removing O, annealing with Ca effectively removed both O and F. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy revealed that the proposed approach effectively removed F and O from the MXene powder. The results of O/N analyses showed that the O concentration decreased by 57.5% (from 2.66 to 1.13 wt%). In addition, XPS fitting showed that the volume fraction of metal oxides (TiO₂ and Al₂O₃) decreased, while surface termination groups (-O and -OH) were enhanced, which could increase the hydrophilic and adsorption properties of the MXene. These findings suggest that when F and O are removed from the MXene powder, the interlayer spacing of its lattice structure increases. The proposed treatment also resulted in an increase in the specific surface area (from 5.17 to 10.98 m²/g), with an increase in oxidation resistance temperature in air from ~436 to ~667 ℃. The benefits of this novel technology were verified by demonstrating the significantly improved cyclic charge-discharge characteristics of a lithium-ion battery with a Ca-treated MXene electrode.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.575-580
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• 2014

We uniformly coated Eu(III)- and Tb(III)-doped yttrium oxide onto the surface of $SiO_2$ spheres and then characterized them by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction crystallography and UV-Visible absorption. 2D and 3D photoluminescence image map profiles were reported for the core-shell type structure. Red emission peaks of Eu(III) were observed between 580 to 730 nm and assigned to $^5D_0{\rightarrow}^7F_J$ (J = 0 - 4) transitions. The green emission peaks of Tb(III) between 450 and 650 nm were attributed to the $^5D_4{\rightarrow}^7F_J$ (J = 6, 5, 4, 3) transitions. For annealed samples, Eu(III) ions were embedded at a $C_2$ symmetry site in $Y_2O_3$, which was accompanied by an increase in luminescence intensity and redness, while Tb(III) was changed to Tb(IV), which resulted in no green emission.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.732-742
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• 2002

This paper presents twin spray characteristics of two impinging F-O-O-F type injectors in which fuel and oxidizer impinge on each other to atomize under the various conditions. The droplet size and velocity in the impinging spray flow field were measured using PDPA. The droplet size and velocity were investigated at the mixture ratios of 1.5, 2.0, 2.47 and 3.0 for four injectors in which two single F-O-O-F injectors were arranged at the intervals of 20.8, 31.2, 41.6 and 62.4mm respectively. In general, the arithmetic mean diameter, SMD and standard deviation of droplet size in the interaction area (X=0 and Y=0mm) were smaller, while the axial velocity in the interaction area was slightly higher. An empirical correlation is obtained for the (D$\_$10/)$\_$D//(D$\_$10/)$\_$c/ value under the assumptions of two identical droplets and these with different size and velocity. The droplets with low Weber numbers below 40 have possibility to coalesce, while those over 40 tend to disintegrate after impingement in the interaction area.

• Journal of Magnetics
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• v.15 no.2
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• pp.78-84
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• 2010

A 3-D.O.F. spherical PM motor has 3 degrees of freedom in its motion by tilting and rotating of a shaft, which can be applied in a range of fields. The back-EMF is proportional to the field flux and angular velocity. The back-EMF constant in conventional rotating machine has a uniform value. However, in a spherical PM motor, the back-EMF constant of the coils varies according to the tilting conditions regardless of whether the angular speed is constant. Consideration of the back-EMF constant is useful for designing 3-D.O.F. spherical PM motors. In this study, the back-EMF constant of the spherical PM motor was considered carefully.

• Journal of IKEEE
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• v.25 no.4
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• pp.774-777
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• 2021

In this paper, we analyzed the gate controllability of 3D NAND Flash Memory with Charge Trap Flash using Ferroelectric (CTF-F) structure. HfO₂, a ferroelectric material, has a high-k characteristic besides polarization. Due to these characteristics, gate controllability is increased in CTF-F structure and on/off current characteristics are improved in Bit Line(BL). As a result of the simulation, in the CTF-F structure, the channel length of String Select Line(SSL) and Ground Select Line(GSL) was 100 nm, which was reduced by 33% compared to the conventional CTF structure, but almost the same off-current characteristics were confirmed. In addition, it was confirmed that the inversion layer was formed stronger in the channel during the program operation, and the current through the BL was increased by about 2 times.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.14-21
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• 1997

This study was conducte dto fabricate 2GHz circulator using Ca,Sn substituted UIG(yttrium iron garnet)ceramics. When the electric, magnetic and microwave properties were measured in Ca, Sn substituted YIG, the measured perimittivity and perfmeability in microwave frequencies were 16.25, 0.8964. For $Y_{2.4}$C $a_{0.3}$A $n_{0.3}$F $e_{3.5}$A $l_{1.5}$ $O_{12}$ garnet ceramics sintered at 1400.deg. C, the ferrimagnetic resonance line width (.DELTA.H) at 10GHz was 53 Oe and saturation magnetization was 375G. The strip-line circulator was simulated with 3-D FEM (finite element method) software and designed at the center frequency of 2GHz. The fabricated strip-line junction circulator using above YIG ceramics had insertion loss of 1.271dB, return loss of 23.843dB, isolation of 21.751dB at the center frequency 1.855GHz.z.z.z.z.z.z.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.147-156
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• 1990

A two-dimensional pulsed doppler system for ultrasonic blood velocity doppler signals is studied and implemented. The second-order sampling method and serial data processing procedures are utillized in the sys- tem, which eliminates the untuning problems at phase channels in the quadrature detection method as well as in the channels of parallel data processing. rho digital signal processor used in this system allows a hardware savings and flexible design options. The efficiency of the various mean frequency estimators in the second-order sampling system is examined by computer simulation as a function of the intersequence sample delay time. The temporal delay for the quadrature component is changed from $1/(4f_o){\;}to{\;}3/(4f_o){\;}and{\;}5/(4f_o)$ where to is the center frequency of the transducer, It is found that autocorrelator is the optimum frequency estimator for the second-order sampling: with !he intersequence sample delay of $1/(4f_o){\;}to{\;}3/(4f_o){\;}and{\;}5/(4f_o)$. The qualitative variation and information proportional to blood velocity in the vessel system are obtained in the VIVO experiments.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.92-98
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• 2006

In this paper, a planar car model with 3 degrees of freedom was analyzed using the concept of the roll center. To avoid ambiguity, force components which require experimental data were excluded. Only kinematic approach was used to find the position and orientation of the vehicle body and the position of the roll center. The roll center was found by the pole with infinitesimal movement and Kennedy-Aronhold theorem. Centrodes, which are the loci of instantaneous centers of planar motion, were constructed with analyzed results to show characteristics of vehicle body motion. To verify the presented analysis method in this paper, the locus of the roll center and the motion of a 3 D.O.F. planar car model were compared with those of the 1 D.O.F. model.