• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.326-331
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• 2001

In this study. CT specimens were prepared from ASME SA5l6 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C$, -3$0^{\circ}C$, -6$0^{\circ}C$, -8$0^{\circ}C$, -10$0^{\circ}C$ and -12$0^{\circ}C$ in the range of stress ratio of 0.1 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ΔKsub/th/ in the early stage of fatigue crack growth ( Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth ( Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm da.dN -ΔK in RegionII, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate da/dN is rapid in proportion to descend temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.196-202
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• 2004

The development of new materials with light weight and high strength has become vital to the machinery, aircraft and auto industries. However, there are a lot of problems with developing such materials that require expensive tools, and a great deal of time and effort. Therefore, the improvement of fatigue strength and fatigue life are mainly focused on adopting residual stress(in this thesis). The compressive residual stress was imposed on the surface according to each shot velocity(57, 70, 83, 96 m/sec) based on Shot-peening, which is the method of improving fatigue life and strength. By using the methods mentioned above, the following conclusions have been drawn. 1. The fatigue crack growth rate(da/dN) of the Shot-peened material was lower than that of the Un-peened material. And in stage I, ΔKth, the threshold stress intensity factor, of the shot-peen processed material is high in critical parts unlike the Un-peened material. Also m, fatigue crack growth exponent and number of cycle of the Shot-peened material was higher than that of the Un-peened material. That is concluded from effect of da/dN. 2. Fatigue life shows more improvement in the Shot-peened material than in the Un-peened material. And compressive residual stress of surface on the Shot-peen processed operate resistance force of fatigue crack propagation.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.234-237
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• 2000

In this paper, a method to implement new Quasi-SOI LDMOSFET is introduced and the electrical characteristics of the device are studied. Key process steps of the device are explained briefly. By performing process and device simulations, electrical characteristics of the device are investigated, with emphasis on the optimization of the tilt angle of p$\^$0/ channel region. The electrical properties of the Quasi-SOI device are compared with those of bulk and SOI devices with the same process parameters. Simulated device characteristics are threshold voltage, off-state leakage current, subthreshold swing, DIBL, output resistance, lattice temperature, I$\_$D/-V$\_$Ds/, and cut-off frequency.

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.105.1-105.1
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• 2000

• Proceedings of the KOR-BRONCHOESO Conference
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• 1979.05a
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• pp.4.4-5
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• 1979

The degree of hearing impairment of chronic otitis media will indicate the nature and severity of middle ear pathology especially condition of ossicular chain, size of ear drum perforation and location of granulation tissue in the middle ear cavity. The subjects were 189 ears of tympanoplasty for chronic otitis media and divided into four groups as follows: Normal ossicular chain with only ear drum perforation (group I), normal ossicular chain with granulation tissue only around the ossicles regardless of any other region (group II), ossicular ankylosis or fixation of handle of malleus to promontory with or without granulation tissue around the ossicle (group III) and ossicular interruption by partial or complete destruction(groupf IV). The results were concluded as follows: 1) The average hearing threshold of chronic otitis media was 44.6 dB and hearing threshold was closely related to the condition of ossicular chain. Hearing threshold became greater in order of normal ossicular chain, ankylosis and interruption. 2) The average hearing threshold of ossicular interrupted group was 49.1 dB and it was greater in the cases of total destruction than that of partial destruction. 3) The hearing loss in the cases of normal ossicular chain with only tympanic membrane perforation was within 45 dB and this level was presumed to represent normal ossicular function. The degree of hearing loss was in proportion to the size of ear drum perforation and when over 45 dB, other middle ear pathology was suggested. 4) In the cases of small ear drum perforation with normal ossicular function, the hearing threshold was within 30 dB. 5) In the type of audiogram, flat type was 30.2% and ascending type 35.4%. Descending type was more frequent in the cases of normal ossicular mobility with granulation tissue around the ossicle and flat type was observed frequently in the cases of ossicular ankylosis. 6) Carhart's notch was seen in 14 cases (7.4%) and observed mainly in ossicular ankylosis. 7) There was no relation between hearing threshold and histopathological type of granulation tissue in chronic otitis media. However the degree of hearing impairment was related to the location of granulation tissue in the middle ear cavity. 8) Authors recognized the granulation tissue compensated the function of interrupted ossicular chain.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.3-6
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• 1992

A new analytical expression for the saturated I-V characteristics of hydrogenerated amorphous silicon thin film transistors(a-si:H TFT) is presented and experimentally verified. The results show that the experimental transfer and output characteristics at several temperatures are easily modeled. The model is based on three functions obtained from the experimental data of $I_D$ versus $V_G$. Theoretical results confirm the simple form of the model in terms of the device geometry. It was determined that the saturated drain current increased at a fixed gate voltage and the device saturated at increasingly larger drain voltages while the threshold voltages decreased.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.6
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• pp.21-27
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• 1998

Electrical and optical characteristics of ZnS:Mn/ZnS:Tb multilayer TFEL devices were investigated for multi-color electroluminescent display applications. Emission spectra of M $n^{2+}$ and T $b^{3+}$ ions were observed from ZnS:Mn/ZnS:Tb multi-layer TFEL devices, and were very broad from 540 nm to 640 nm. Saturation luminance measured at 155 V was 1025 Cd/$m^2$. C-V, $Q_{t}$ - $V_{p}$ curves showed that the phosphor capacitance ( $C_{p}$ ) and the insulator capacitance ( $C_{i}$ ) were 13.5nF/$\textrm{cm}^2$ and 60 nF/$\textrm{cm}^2$, respectively. Threshold voltage( $V_{thl}$) was shown to decrease from 126 V to 93 V due to the increase of the applied voltage from 155 V to 185 V, which was attributed to the increase of the polarization charge. The equation for the calculation of the threshold voltage as a function of the applied voltage was proposed for the first time. The calculated threshold voltage agreed well with the data obtained from the measurement.t.t.t.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.250-253
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• 2013

In this paper, we fabricated 3D pillar type silicon-oxide-nitride-oxide-silicon (SONOS) devices for high density flash applications. To solve the limitation between erase speed and data retention of the conventional SONOS devices, bandgap-engineered (BE) tunneling oxide of oxide-nitride-oxide configuration is integrated with the 3D structure. In addition, the tunneling oxide is modulated by another method of $N_2$ ion implantation ($N_2$ I/I). The measured data shows that the BE-SONOS device has better electrical characteristics, such as a lower threshold voltage ($V_{\tau}$) of 0.13 V, and a higher $g_{m.max}$ of 18.6 ${\mu}A/V$ and mobility of 27.02 $cm^2/Vs$ than the conventional and $N_2$ I/I SONOS devices. Memory characteristics show that the modulated tunneling oxide devices have fast erase speed. Among the devices, the BE-SONOS device has faster program/erase (P/E) speed, and more stable endurance characteristics, than conventional and $N_2$ I/I devices. From the flicker noise analysis, however, the BE-SONOS device seems to have more interface traps between the tunneling oxide and silicon substrate, which should be considered in designing the process conditions. Finally, 3D structures, such as the pillar type BE-SONOS device, are more suitable for next generation memory devices than other modulated tunneling oxide devices.

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.65-72
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• 2010

We propose the asymmetric 2.5Gbps/622Mbps PON(Passive Optical Network) in order to reduce the bandwith of filter at receiver with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation. I theoretically analyze BER(Bit Error Rate) performance and the power sensitivity with the optimal threshold level by performing simulation with MATLAB according to the types of downstream data. The results have shown that the optimal threshold level at the optical receiver could be saturated at 0.33 as the optical received power increase more than -26dBm to keep $10^{-12}$ of BER to a minimum. Also the power sensitivity is more improved by about 3dB by fixing the threshold level at 0.33 than the conventional receiver. The proposed system can be a useful technology for optical access networks with asymmetric upstream and downstream data rates because the optical receiver can be used without controlling threshold levels and that does not require a light source in optical network unit (ONU) and its control circuits in the optical line termination (OLT).

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.549-555
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• 2004

Cement of three alkalinities (equivalent alkalinities of 0.36,0.52 and 0.97) was employed in fabricating a set of classical G109 type specimens. To-date, these have been subjected to a one week wet-one week dry cyclic pending using 15 w/o NaCl solution. At the end of the dry period, potential and macro-cell current were measured to indicate whether the top reinforcing steel was in the passive or active state. Once this bar became active, the specimen was autopsied and the extent of corrosion was documented. Subsequent to visual inspection, concrete powder samples were collected from the upper region of the top rebar trace; and at a certain times concrete cores were taken from non-reinforced specimens. Using these, determinations were made of (1) critical chloride concentration for corrosion initiation ($Cl_{th}^-$), (2) effective chloride diffusion coefficient ($D_e$), and (3) pore water alkalinity ($[OH^-]$). The pore water alkalinity was strongly related to the alkali content of cement that was used in the mix. The chloride concentration, ($Cl^-$), was greater at active than at passive sites, presumably as a consequence of electro migration and accumulation of these species at active site subsequent to corrosion initiation. Accordingly, ($Cl^-$) at passive sites was considered indicative of the threshold concentration fur corrosion initiation. The $Cl_{th}^-$ was increased with increasing Time-to-corrosion ($T_i$). Consequently, the HA(High Alkalinity) specimens exhibited the highest $Cl_{th}^-$ and the NA(Normal Alkalinity) was the least. This range exceeds what has previously been reported in North America. In addition, the effective diffusion coefficient, $D_e$, was about 40 percent lower for concrete prepared with the HA cement compared to the NA and LA(Low Alkalinity) ones.