Ewald 합 기법을 이용한 구형 도파관의 H-면에 위치한 타원 편파 오프셋 십자 슬롯에 대한 해석

김병문,조영기,윤리호,손현 경북대학교 전자기술연구소 2000 電子技術硏究誌 Vol.21 No.1

This paper presents the analysis of an offset cross slot in the broad wall of a rectangular waveguide. The problem is formulated in teens of integro-differential equation which is solved using the method of moments with triangular Roop-top basis. For the effective numerical intgral evaluation, the Ewald sum technique is applied to the Green's function of the rectangular waveguide, transforming them into the rapidly convergent form. We have shown that a pair of narrow slots crossed at arbitrary angles and located at the proper point in the broad wall of an ordinary rectangular waveguide will radiate a wave very nearly circularly polarized at the desired direction.

고온변형시 Alloy 718 의 동적 및 준동적 재결정 거동

나영상,김인수,박노광,손성만 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.10

Compression tests were carried out on Alloy 718 to investigate the microstructure development following dynamic recrystallization, meta-dynamic recrystallization and grain growth. Tests were performed in the temperature range of 927∼1066℃ and strain rate range of 5∼5×10^(-4)s^_(-1), with true strains up to 0.8. Dynamically recrystallized grain size decreases consistently with increasing Zener-Hollomon parameter (Z=ε exp(Q/RT)) which is function of strain rate and temperature. The extent of recrystallization increases with a decrease in Zener-Hollomon parameter due to an increase in the critical strain (ε_c) corresponding to the initiation of dynamic recrystallization. The fraction of meta-dynamically recrystallized grain, however, increases with increasing the strain rate from 0.01s^(-1) to 1s^(-1). This paper outlines the microstructural evolution of Alloy 718 during the high temperature deformation.

청정 열처리 기술의 개발동향

손명진 한국열처리공학회 1999 熱處理工學會誌 Vol.12 No.1

Performance and carrier transport analysis of In_0.7Ga_0.3As quantum-well MOSFETs with Al₂O₃/HfO₂ gate stack

Son, S.W.,Park, J.H.,Baek, J.M.,Kim, J.S.,Kim, D.K.,Shin, S.H.,Banerjee, S.K.,Lee, J.H.,Kim, T.W.,Kim, D.H. Pergamon Press ; Elsevier Science Ltd 2016 Solid-State Electronics Vol.123 No.-

In this paper, we have fabricated and characterized In<SUB>0.7</SUB>Ga<SUB>0.3</SUB>As quantum-well (QW) metal-oxide-semiconductor field-effect-transistors (MOSFETs). We have employed the gate dielectric of the Al<SUB>2</SUB>O<SUB>3</SUB>/HfO<SUB>2</SUB> (0.6/2nm) bi-layer stack by ALD. The fabricated device with L<SUB>g</SUB>=4μm exhibits a record maximum transconductance (g<SUB>m_max</SUB>) in excess of 520μS/μm at >1μm region, and reasonably good electrostatic integrity, such as SS=110mV/decade and DIBL=43mV/V. Also, we have investigated the gate length scaling behavior in terms of output, transconductance, and transfer characteristics. In particular, our devices feature very uniform values of the electrostatic integrity, such as SS=100-110mV/decade, V<SUB>T</SUB>=-0.25V to -0.2V and DIBL=40-50mV/V, as L<SUB>g</SUB> decreases from 10μm to 4μm. Furthermore, we have explored the impact of source resistance (R<SUB>S</SUB>) onto the device characteristics of the InGaAs QW MOSFETs. In doing so, we have modeled both measured extrinsic transconductance (g<SUB>m_ext</SUB>) and intrinsic transconductance (g<SUB>m_int</SUB>) as a function of L<SUB>g</SUB>.

Alterations of contractions and L-type Ca²⁺ currents by murrayafoline-A in rat ventricular myocytes

Son, M.J.,Chidipi, B.,Kim, J.C.,Huong, T.T.,Tai, B.H.,Kim, Y.H.,Ahn, J.R.,Cuong, N.M.,Woo, S.H. North-Holland ; Elsevier Science Ltd 2014 european journal of pharmacology Vol.740 No.-

We examined the effects of murrayafoline-A (1-methoxy-3-methylcarbazole, Mu-A), which is isolated from the dried roots of Glycosmis stenocarpa, on cell shortenings and L-type Ca<SUP>2+</SUP> currents (I<SUB>Ca,L</SUB>) in rat ventricular myocytes. Cell shortenings and I<SUB>Ca,L</SUB> were measured using the video edge detection method and patch-clamp techniques, respectively. Mu-A transiently increased cell shortenings in a concentration-dependent manner with an EC<SUB>50</SUB> of ~20μM. The maximal effect of Mu-A, approximately 175% of the control, was observed at ≥100μM. The positive inotropic effect of Mu-A (25μM) reached a maximum after ~2-min exposures, and then decayed after a ~1-min steady-state. During the Mu-A-induced positive inotropy, the rate of contraction was accelerated, whereas the rate of relaxation was not significantly altered. To understand the possible mechanism for the Mu-A-induced positive inotropy, the I<SUB>Ca,L</SUB> was assessed. Mu-A transiently enhanced the I<SUB>Ca,L</SUB>. Concentration-dependence of the increase in I<SUB>Ca,L</SUB> by Mu-A was similar to that of positive inotropic effect of Mu-A. The maximal effect of Mu-A (25μM) on I<SUB>Ca,L</SUB> was observed at 2-3min after the application of Mu-A. A partial inhibition of I<SUB>Ca,L</SUB> using verapamil (1μM) induced a right shift of concentration-response curve of the positive inotropic effect of Mu-A and significantly attenuated the effect. These results suggest that Mu-A may transiently enhance contractility, at least in part, by increasing the Ca<SUP>2+</SUP> influx through the L-type Ca<SUP>2+</SUP> channels in rat ventricular myocytes.

Aluminizing and Boroaluminizing Treatments of Mar-M247 and Their Effect on Hot Corrosion Resistance in Na₂SO₄-NaCl Molten Salt

Cho, J.H.,Kim, T.W.,Son, K.S.,Yoon, J.H.,Kim, H.S.,Leisk, G.G.,Mitton, D.B.,Latanision, R.M. 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.3

The effect of surface modifications of Mar-M247 superalloy on hot corrosion resistance was examined in Na₂SO₄-NaCl molten salt. The Mar-M247 was aluminized and boroaluminized by pack cementation in Ar and underwent a cyclic hot corrosion test in Na₂SO₄-NaCl molten salt. The XRD results showed that a Ni2Al3 phase was formed between the aluminized layer and the substrate when the surface modification temperature was below 1273 K. However, a NiAl phase formed when the temperature was above 1273 K. The intensity of the XRD peak in the NiAl phase increased after post heat treatment. Hot corrosion resistance increased for the specimens containing NiAl rather than Ni₂Al₃ phase. The ductile NiAl phase suppressed the potential for crack initiation during thermal cycling. Post heat treatment increased the corrosion resistance of the aluminized layer for Mar-M247, which underwent surface modification at 1273 K and above. In the boroaluminized Mar-M247 specimens, corrosion resistance decreased as a result of the blocking of outward diffusion of Cr by boron and decreased cohesion between the oxide scale and the aluminized layer during thermal cycling.

Evolution of carbides in cold-work tool steels

Kim, H.,Kang, J.Y.,Son, D.,Lee, T.H.,Cho, K.M. Elsevier 2015 Materials characterization Vol.107 No.-

This study aimed to present the complete history of carbide evolution in a cold-work tool steel along its full processing route for fabrication and application. A sequence of processes from cast to final hardening heat treatment was conducted on an 8% Cr-steel to reproduce a typical commercial processing route in a small scale. The carbides found at each process step were then identified by electron diffraction with energy dispersive spectroscopy in a scanning or transmission electron microscope. After solidification, MC, M<SUB>7</SUB>C<SUB>3</SUB> and M<SUB>2</SUB>C carbides were identified and the last one dissolved during hot compression at 1180<SUP>o</SUP>C. In a subsequent annealing at 870<SUP>o</SUP>C followed by slow cooling, M<SUB>6</SUB>C and M<SUB>23</SUB>C<SUB>6</SUB> were added, while they were dissolved in the following austenitization at 1030<SUP>o</SUP>C. After the final tempering at 520<SUP>o</SUP>C, fine M<SUB>23</SUB>C<SUB>6</SUB> precipitated again, thus the final microstructure was the tempered martensite with MC, M<SUB>7</SUB>C<SUB>3</SUB> and M<SUB>23</SUB>C<SUB>6</SUB> carbide. The transient M<SUB>2</SUB>C and M<SUB>6</SUB>C originated from the segregation of Mo and finally disappeared due to attenuated segregation and the consequent thermodynamic instability.

FABRICATION AND ELECTRICAL PROPERTIES OF PZT-PVDF 0-3 TYPE COMPOSITE FILM

Son, Y. H.,Kweon, S. Y.,Kim, S. J.,Kim, Y. M.,Hong, T. W.,Lee, Y. G. Taylor Francis 2007 Integrated ferroelectrics Vol.88 No.1

<P> A film speaker was fabricated with 0-3 type piezoelectric composite. The 0-3 type composite was developed to incorporate the advantages of both ceramic and polymer. The pastes of PZT-PVDF composite were made with various mixing ratio. The paste was printed by conventional screen-printing method on ITO (Indium Tin Oxide) bottom electrode which was deposited on PET (polyethylene terephthalate) polymer film. The prepared composite film was about 80 μm in thickness. After printing the top-electrode of silver-paste, 4 kV/mm of DC field was applied at 120°C for an hour to align the electric dipole in the 0-3 composite film. The piezoelectric charge constant of d33 was increased with increasing the PZT weight percent. The maximum value was 24 pC/N at 70 wt% of PZT. But the piezoelectric voltage constant of g33 had the maximum value about 32 mV · m/N at 65 wt% of PZT. The SPL (Sound Pressure Level) of the speaker fabricated with the 65:35 composite film was tested at various driving voltages of 1 ∼ 100Vrms. The SPL was saturated at the driving voltage of 70Vrms and the value was about 68 dB at 1 kHz.</P>

Long-channel In_0.7Ga_0.3As/In_0.52Al_0.48As quantum-well MOSFETs on InP substrate with record <i>μ_{n_eff}</i> = 6960 cm²/V-s

Son, S.-W.,Shin, S.H.,Park, J.H.,Baek, J.-M.,Kim, D.-K.,Lee, J.-H.,Kim, T.-W.,Kim, D.-H. IET 2017 Electronics letters Vol.53 No.18

<P>Long-channel In0.7Ga0.3As/In0.52Al0.48As quantum-well (QW) metaloxide- semiconductor field-effect-transistors (MOSFETs) on InP substrate have been fabricated and characterised. The fabricated device with L-g = 4 mu m exhibits excellent maximum transconductance (g(m_ max)) in excess of 0.48 mS/mu m at V-DS = 0.95 V, together with reasonably good electrostatic integrity of drain-induced-barrier-lowering < 40 mV/V and subthreshold-swing < 100 mV/decade. Besides, the effective mobility (mu(n_eff)) of the same device has been extracted, revealing that the device in this work yields excellent mu(n_eff) = 6960 cm(2)/V-s at room temperature. To the knowledge of the authors, the value of mu(n_eff) in this work is the highest in any surface-channel InGaAs MOSFET technology.</P>

The Use of Collagen Content as Determined by Spectral Domain Polarization-Sensitive Optical Coherence Tomography to Assess Colon Anastomosis Healing in a Rat Model

Son, K.H.,Jeong, H.-W.,Jung, W.-W.,Kim, H.-S.,Lee, S.K.,Kim, K.T.,Ahn, C.B.,Park, K.Y.,Kim, B.-M.,Lee, S.H. S. Karger AG 2014 European surgical research Vol.52 No.1

<P>Abstract</P><P><B><I>Background/Purpose:</I></B> Many studies have been undertaken to prevent anastomosis leakage of the colon, and several methods have been used to assess anastomosis healing, such as measurement of bursting pressure or hydroxyproline (a marker of collagen) content at the anastomosis site. However, these methods are inappropriate for comparing anastomosis healing at two time points in the same animals. In the present study, we measured the collagen level by spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) to assess anastomosis healing. <B><I>Methods:</I></B> Sprague-Dawley rats were divided into groups C (saline-administered controls; study group) and M [a 5-fluorouracil (5-FU)-administered experimental group]. Immediately after end-to-end anastomosis of the colon, SD-PS-OCT images of anastomoses were taken (baseline). Animals were administered saline or 5-FU for 7 days. On the 7th postoperative day, SD-PS-OCT images were acquired, a histopathologic exam was performed, and hydroxyproline levels as well as mRNA expressions of collagen-1 and collagen-3 were measured at the anastomosis site. <B><I>Results:</I></B> Fibroblast proliferation and inflammatory cell infiltration were greater in group C than in group M. The mRNA expressions of collagen-1 and collagen-3 were substantially higher in group C. Hydroxyproline levels were higher in group M than in group C. Though collagen levels measured by SD-PS-OCT at 7 days were elevated compared with baseline in group C, no such changes were observed for group M. <B><I>Conclusion:</I></B> Collagen levels at the colon anastomosis site, measured with SD-PS-OCT, were not increased at 7 days postoperatively versus baseline when 5-FU was injected, but were increased in saline-treated controls. The measurement of collagen content by SD-PS-OCT was found to provide a good means of assessing anastomosis healing, because it allows in situ assessment of collagen contents at baseline and during the postoperative period.</P><P>© 2014 S. Karger AG, Basel</P>