• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.235-238
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• 2009

This paper describes the mechanical properties of poly (Polycrystalline) 3C-SiC thin films with $N_2$ in-situ doping. In this work, the poly 3C-SiC film was deposited by APCVD (Atmospheric Pressure Chemical Vapor Deposition) method using single-precursor HMDS (Hexamethyildisilane: $Si_2(CH_3)_6)$ at $1200^{\circ}C$. The mechanical properties of doped poly 3C-SiC thin films were measured by nono-indentation according to the various $N_2$ flow rate. In the case of 0 sccm $N_2$ flow rate, Young's Modulus and hardness were obtained as 285 GPa and 35 GPa, respectively. Young's Modulus and hardness were decreased according to increase of $N_2$ flow rate. The crystallinity and surface roughness was also measured by XRD (X-Ray Diffraction) and AFM (Atomic Force Microscopy), respectively.

• Korean Journal of Metals and Materials
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• v.50 no.10
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• pp.735-743
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• 2012

The aim of this study was to analyze the effect of the cooling rate after heat treatment on the microstructure and mechanical properties of 2507 duplex stainless steels. Heat treatment was carried out at $1050^{\circ}C$ for 1 hr, followed by controlled cooling. The cooling rates were $175.6{\times}10^{-3}^{\circ}C/s$, $47.8{\times}10^{-3}^{\circ}C/s$, $33.3{\times}10^{-3}^{\circ}C/s$, $16.7{\times}10^{-3}^{\circ}C/s$, $11.7{\times}10^{-3}^{\circ}C/s$, $5.8{\times}10^{-3}^{\circ}C/s$ and $2.8{\times}10^{-3}^{\circ}C/s$, which resulted in variations of the microstructure, such as the fractional change of the ferrite phase and sigma phase formation. Fatigue, hardness, impact and tensile tests were performed on the specimens with different cooling rates. The precipitation of the ${\sigma}$ phase caused a hardness increase and a sharp decrease of toughness and tensile elongation. The fatigue limit of the sample with a cooling rate of $5.8{\times}10^{-3}^{\circ}C/s$ was 26 MPa higher than that of the sample with a cooling rate of $175.6{\times}10^{-3}^{\circ}C/s$. Our observations of the fracture surface confirmed that the higher fatigue resistance of the specimen with a cooling rate of $5.8{\times}10^{-3}^{\circ}C/s$ was caused by the delay of the fatigue crack growth, in addition to higher yield strength.

• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.92-97
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• 2000

An AMR(Adaptive Multi-Rate) speech coding algorithm has been adopted as a standard speech codec for IMT-2000. It is based on the algebraic CELP, and consists of eight speech coding modes having the bit rate from 4.75 kbit/s to 12.2 kbit/s. It also contains the VAD(Voice Activity Detector), SCR (Source Controlled Rate) operation, and error concealment scheme for robustness in a radio channel. The bit rate of AMR is changed on a frame basis depending on the channel condition. In this paper, we introduced AMR speech coding algorithm and performed the real-time implementation using TMS320C6201, i.e., a Texas Instrument's fixed-point DSP. With the ANSI C source code released from ETSI and 3GPP, we convert and optimize the program to make it run in real time using the C compiler and assembly language. It is verified that the decoded result of the implemented speech codec on the DSP is identical with the PC simulation result using ANSI C code for test sequences. Also, actual sound input/output test using microphone and speaker demonstrates its proper real-time operation without distortions or delays.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.73-80
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• 1987

During PWHT, it is well known that residual stress in weld HAZ is one of the reasons for PWHT embitterment. In case of static loading, it was experimentally found that fracture toughness of weld HAZ was dependant upon PWHT conditions. However, the effects of PWHT on fatigue behavior are not clearly verified. Therefore, in this paper, the effects of heating rate PWHT conditions and residual stress simulated in weld HAZ of Cr-Mo steel on fatigue crack propagation behavior were evaluated by fatigue Testing and SEM observation. The obtained results are summarized as follows; 1. Applied stress($10 Kgf/mm^2$) in weld HAZ during PWHT tneded to decrease fatigue strength and to increase fatigue crack growth rate. 2. Applied stress and slow heating rate of 60.deg. C/hr during PWHT contributed to precipitin of impurity elements as well as carbide, which promoted the fatigue crack growth. 3. Fatigue crack growth rate decreased at the heating rate of 220.deg. C/hr in contrast with 600.deg. C/hr and 60.deg. C/hr.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.299-304
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• 2004

In recent years, silicon carbide has emerged as an important material for MEMS application. In order to fabricate an SiC film based MEMS structure by using chemical etching method, high operating temperature is required due to high chemical stability Therefore, dry etching using plasma is the best solution. SiC film was deposited by thermal CVD at the temperature of 100$0^{\circ}C$ and pressure of 10 torr. SiC was dry etched with a reactive ion etching (RIE) system, using SF$_{6}$/O$_2$ and CF$_4$/O$_2$ gas mixture. Etch rate has been investigated as a function of oxygen concentration in the gas mixture, rf power, working pressure and gas flow rate. Etch rate was measured by surface profiler and FE-SEM. SF$_{6}$/O$_2$ gas mixture showed higher etch rate than CF$_4$/O$_2$ gas mixture. Maximum etch rate appeared at RF Power of 450W. $O_2$ dilute mixtures resulted in an increasing of etch rate up to 40％, and the superior anisotropic cross section was observe

• Journal of Welding and Joining
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• v.23 no.2
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• pp.52-58
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• 2005

This study was carried out to investigate the effect of bonding temperature and heating rate on transient liquid phase diffusion bonding of Ni-base superalloy. The heating rate was varied by $0.1^{\circ}C$/sec, $1^{\circ}C$/sec, $10^{\circ}C$/sec to the bonding temperatures $1100^{\circ}C,\;1150^{\circ}C,\;1200^{\circ}C$ under vacuum. As bonding temperature increased, maximum dissolution width of base metal increased, but a dissolution finishing time decreased. The eutectic width of insert metal in the bonded interlayer decreased linearly in proportion to the square root of holding time during isothermal solidification stage. The bonding temperature was raised, isothermal solidification rate slightly increased. As the heating rate decreased and the bonding temperature increased, the completion time of dissolution after reaching bonding temperature decreased. When the heating rate was very slow, the solidification proceeded before reaching bonding temperature and the time required for the completion of isothermal solidification became reduced.

• Journal of the Korean Ceramic Society
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• v.35 no.7
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• pp.749-756
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• 1998

TiC-Ni and TiC-Ni-Mo cermet powders were produced by Self-propagating High temperature Synthesis (SHS) process. The cooling rate of synthesized powders were controlled by using the V-shaped copper jig and the carbide size decreased with increasing the cooling rate I. e decreasing the width of copper jig Round shape carbide particles were produced after SHS reaction in TiC-Ni as well as TiC-Ni-Mo powders. Local segregation of Mo rich phases was observed in SHS powder of TiC-Ni-Mo and the uneven dis-triobution of Mo promoted the faster growth rate of carbide particles during sintering compared to the same composition specimen with commercial TiC powder. Howogeneous microstructure of TiC-Ni-Mo cermet was obtained when the elemental Mo powder was mixed with the SHS powder of TiC-Ni.

• Journal of Bio-Environment Control
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• v.9 no.4
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• pp.185-192
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• 2000

This study was conducted to develop mathematical model of respiration rate of cucumber plant under varying environmental conditions. 8.55% of gross photosynthesis of individual cucumber plant was used as respiration. Growth respiration coefficient was estimated as 0.0935. Maintenance respiration rate was estimated as 0.00158g CH$_2$g$^{-1}$ .h$^{-1}$ at 24$^{\circ}C$ of air temperature and it increased exponentially as air temperature became higher. Respiration rate decreased poportionally as content of storage carbohydrate became lower. Ion uptake respiration rate of roots was estimated as 0.6648g C$H_2O$.(gN)$^{-1}$ .

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.84-90
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• 2008

The mass loss rate and heat release rate of puzzle mats were analysed using variable external irradiation level. Five samples of puzzle mat were tested in this study : Type A, B, C, D and E. Type A, B and C are all general grades whereas Type D and E are both Flame retardant grades. Incident heat fluxs of $25kW/m^2$, $35kW/m^2$, $50kW/m^2$ and $70kW/m^2$ were selected for these experiments. All samples were tested in the horizontal orientation and were wrapped in a single layer of aluminum foil. Each sample was nominally 20mm thick and 100mm square. The combustion heat and mass loss rate were carried out from Oxygen bomb calorimeter and mass loss calorimeter according to ISO 5660-1 respectively. Heat release rates were calculated using the equation ${\dot{Q}}=A_f{\dot{m}}"_X{\Delta}H_c=0.75A_f{\dot{m}}"{\Delta}H_c$. where $A_f$ is the horizontal burning area of the sample, $\dot{m}"$ is mass loss rate per unit area, ${\Delta}H_c$ is complete heat of combustion and 0.75 is combustion efficiency.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.9
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• pp.1285-1289
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• 2000

This study investigated the lipogenesis capacity of hepatocytes and lipolysis rate of adipocytes of broilers as affected by different fatty acids (trial one) and different linoleic acid (C18:2) levels (trial two). Twenty 6-wk old broilers were used; their hepatocytes and adipocytes were isolated for the in vitro study. In trial one, four treatments were tested. The control group in which no fatty acid was added, and the test groups to which were added $300{\mu}M$ of C16:0, C18:1 and C18:2, respectively. For trial two, different levels (0, $300{\mu}M$ and 1 mM) of C18:2 combined to fatty acid-free bovine serum albumin (BSA) were added to the medium. According to results of trial one, added fatty acids significantly reduced the incorporation by hepatocytes of [U,$^{14}C$]glucose into total lipid (p<0.05); the lipogenesis capacity in C18:2 group was the lowest. Although a similar pattern was found with [l,$^{14}C$]acetate, the groups only slightly differed in terms of lipogenesis capacity (p=0.11). In addition, the C18:2 group had a significantly (p<0.05) greater lipolysis rate than the C16:0 and control groups. Results of trial two indicated that C18:2 significantly (p<0.05) reduced lipogenesis capacity both for [U,$^{14}C$]glucose and [l,$^{14}C$]acetate, and markedly stimulated the lipolysis rate (p<0.05), displaying a dose response. Results presented herein demonstrate that C18:2 can reduce lipogenesis capacity and stimulate the lipolysis rate in broilers.