• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.121-134
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• 1994

Shock tube investigation of ethylene oxide-$0_{2}-N_{2}$ mixture have been performed to reveal detonation characteristics of the mixture in terms of detonation pressure and speed. Theoretical calculation of thermodynamic parameters at the Chapmann-Jouguet detonation of the mixture has been also performed. A comparision of the observed results with the calculated ones can lead us to predict the detonation parameters of ethylene oxide in an artificial air. In addition, we have observed ignition delay times of ethylene oxide mixtures. The best fit of the observed delay times to Arrhenius gas kinetic relation gives : ${\tau}=10^{-144}{e{xp}}(E_a/RT)[C_{2}H_{4}O]^{-4.8}[O_{2}]^{-12.4}[N_{2}]^{-14.1}$ $E_a=3.67kcal/mole$ The observed activation energy is markedly reduced, compared with the case of ethylene oxide diluted in Ar. It could be due to the factor that $N_2$ play a role as detonation promoter yielding very reactive NOx radicals.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.204-210
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• 1995

The characteristics of the internal circuits and the load capacitance should be included to optimize the size of BiCMOS buffer. In order to get the optimum size and delay time of the BiCMOS buffer, new size plane is suggested. By using the size plane, the optimum characteristics of CMOS buffer according to the number of stages can be obtained. From this method, delaytime, .tau.$_{D}$, is obtained 2.39 nsec with $V_{\var}$=5V, $C_{L}$=5pF, W=30.mu.m and $A_{e}$=135.mu. $m^{2}$.>..>...>.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.99-105
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• 1997

This paper analyzes DLL(Delay lock loop) under the multipath fading effects. The evaluated performance measures include the steady-state timing error probability density function (PDF) and the mean-time-to-lose-lock (MTLL) under multipath fading effects. The discriminator characteristic S(${\epsilon}$) is shown to be zero at the point of timing error ${\epsilon}_{0}$ that is not zero, and the MTLL decreases as the delayed signal power $g_{2}$ and delayed time ${\tau}_{d}$ increase. We approximate the steady-state timing error PDF linearly with these variables and evaluate the steady-state timing error PDF and MTLL. The severe multipath fading effects result lower MTLL, in this case we make MTLL larger by increasing the early-late discriminator offset ${\Delta}$. First, we calculate the timing error point ${\epsilon}_{0}$, and present the performance of DLL under multipath fading. The timing error PDF, MTLL and the performance of DLL with ${\Delta}$ are also investigated. And we conclude that the larger ${\Delta}$ makes a higher MTLL and a better performance of DLL under multipath fading effects.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.661-665
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• 2006

This study investigates objective and subjective evaluations of refrigerator noise. To describe the fluctuations like a click, a rapid increase of sound level, a change of pitch, a transition into the stationary and ending phase, the psychoacoustical and autocorrelation function(ACF) parameters have been employed. First, subjective evaluation of the noisiness of 24 kinds of refrigerators was conducted. Then, the relationship between objective measures of the refrigerator noise on perceived noisiness was examined with multiple regression analyses. Sound Quality Indices using the psychoacoustical and ACF parameters were also developed. The important psychoacoustical parameters for evaluating noisiness are loudness and roughness of stationary phase. The relationship between the noisiness and the ACF parameters shows that sound energy ${\Phi}(0)$ and its fluctuations are important. Also, refrigerator sounds that had a fluctuation of pitch were rated as more annoying. The fluctuation of pitch is expressed by ${\tau}_1\;and\;{\Phi}_1$ defined by the delay time and the amplitude of the first peak of the ACF.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1993-2001
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• 2006

The piezoelectric bimorph film, which, as an actuator, can generate more effective displacement than the usual PVDF film, is used to control the turbulent boundary-layer flow. The change of wall pressures inside the turbulent boundary layer is observed by using the multi-channel microphone array flush-mounted on the surface when actuation at the non-dimensional frequency $f_b^+$:=0.008 and 0.028 is applied to the turbulent boundary layer. The wall pressure characteristics by the actuation to produce local displacement are more dominantly influenced by the size of the actuator module than the actuation frequency. The movement of large-scale turbulent structures to the upper layer is found to be the main mechanism of the reduction in the wall- pressure energy spectrum when the 700$700{\nu}/u_{\tau}$-long bimorph film is periodically actuated at the non- dimensional frequency $f_b^+$:=0.008 and 0.028. The biomorph actuator is triggered with the time delay for the active forcing at a single frequency when a 1/8' pressure-type, pin-holed microphone sensor detects the large-amplitude pressure event by the turbulent spot. The wall-pressure energy in the late-transitional boundary layer is partially reduced near the convection wavenumber by the open-loop control based on the large amplitude event.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.172-178
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• 2016

In this paper, we propose a sub-10 nm Ge/GaAs heterojunction-based tunneling field-effect transistor (TFET) with vertical band-to-band tunneling (BBT) operation for ultra-low-power (LP) applications. We design a stack structure that is based on the Ge/GaAs heterojunction to realize the vertical BBT operation. The use of vertical BBT operations in devices results in excellent subthreshold characteristics with a reduction in the drain-induced barrier thinning (DIBT) phenomenon. The proposed device with a channel length ($L_{ch}$) of 5 nm exhibits outstanding LP performance with a subthreshold swing (S) of 29.1 mV/dec and an off-state current ($I_{off}$) of $1.12{\times}10^{-11}A/{\mu}m$. In addition, the use of the highk spacer dielectric $HfO_2$ improves the on-state current ($I_{on}$) with an intrinsic delay time (${\tau}$) because of a higher fringing field. We demonstrate a sub-10 nm LP switching device that realizes a good S and lower $I_{off}$ at a lower supply voltage ($V_{DD}$) of 0.2 V.