• Title/Summary/Keyword: Constant frequency

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Study on Mutual Relation between the Level of Deterioration Influenced by the Changes of Chemical and Physical Properties and the Change of Dielectric Constant for Engine Oil - Gasoline Engine Oil (엔진오일의 화학적 및 물리적 변화에 의한 퇴화정도와 유전상수 변화에 관한 상호관계 연구 - 가솔린엔진오일)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.22 no.5
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    • pp.260-268
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    • 2006
  • The dielectric constants of used gasoline engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$ Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz,,and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 4% for gasoline engine oil.

Study on Mutual Relation between the Level of Deterioration Influenced by the Changes of Chemical and Physical Properties and the Change of Dielectric Constant for Engine Oil - Diesel Engine Oil (엔진오일의 화학적 및 물리적 변화에 의한 퇴화정도와 유전상수 변화에 관한 상호관계 연구 - 디젤엔진오일)

  • Chun, Sang-Myung
    • Tribology and Lubricants
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    • v.22 no.5
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    • pp.290-300
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    • 2006
  • The dielectric constants of used diesel engine oils were obtained at a few temperatures and a frequency. Through analyzing the characteristics of dielectric constant, the related correlation between the changes in dielectric constants of oil and the degree of oil deterioration is going to be found. The dielectric constant was calculated using cross capacitances measured by a sensor tube. As results of the measurement of the fresh engine oil's dielectric constant, it was found that the value of dielectric constant was set down below $60^{\circ}C$ regardless changing frequency. Further, above 6 kHz, the dielectric constant was set down even if temperature was above $100^{\circ}C$. Therefore, for the measurement of used oils, it was selected the frequency of 6 kHz, and the temperature of $80^{\circ}C$ preventing a certain ionic-conduction effects on the measured dielectric constant and the evaporation of a certain fluid mixed with engine oil. Specially, the effects of the mixing fluid like coolant, water and fuel on the fresh engine oil's dielectric constant were studied. It was found that the oil mixed with coolant showed the highest value, next water, and the lowest fuel. As results of the measurement of the used engine oil's dielectric constant, it was found that the possible changed rate of the used engine oil's dielectric constant based on the warning limit for engine oil in service was below 10% for diesel engine oil.

Zirconium Titanate Thin FIlm Prepared by Surface Sol-Gel Process and Effects of Thickness on Dielectric Property

  • Kim, Chy-Hyung;Lee, Moon-Hee
    • Bulletin of the Korean Chemical Society
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    • v.23 no.5
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    • pp.741-744
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    • 2002
  • Single phase of multicomponent oxide ZrTiO4 film could be prepared through surface sol-gel route simply by coating the mixture of 100 mM zirconium butoxide and titanium butoxide on $Pt/Ti/SiO_2Si(100)$ substrate, following pyro lysis at $450^{\circ}C$, and annealing it at 770 $^{\circ}C.$ The dielectric constant of the film was reduced as the film thickness decreased due to of the interfacial effects caused by layer/electrode and a few voids inside the multilayer. However, the dielectric property was independent of applied dc bias sweeps voltage (-2 to +2 V).The dielectric constant of bulk film, 31.9, estimated using series-connected capacitor model was independent of film thickness and frequency in the measurement range, but theoretical interfacial thickness, ti, was dependent on the frequency. It reached a saturated ti value, $6.9{\AA}$, at high frequency by extraction of some capacitance component formed at low frequency range. The dielectric constant of bulk ZrTiO4 pellet-shaped material was 33.7 and very stable with frequency promising as good applicable devices.

Improvement of Time Resolution of the Constant Q Transform using Octave Band Filter Banks (옥타브 밴드 필터 뱅크를 이용한 일정 Q 변환의 시간 해상도 개선)

  • Byun, Jeong-Keun;Kim, Dong-Jun;Choi, Do-Ill;Park, Sang-Hui
    • The Journal of the Acoustical Society of Korea
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    • v.14 no.6
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    • pp.32-39
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    • 1995
  • This paper describes a method of musical frequency estimation using tree structured octave band filter banks and the constant Q spectral transform. The performances of the proposed method are compared with those of the conventional constant Q transform using FFT. The performances are evaluated by the estimated fundamental frequency, varying the bandwidth and the frequency resolutions. The results are as follows. With the same frequency resolution of the conventional constant Q transform using FFT, the proposed method gives the better time resolutions, thus, the limit of the processing bandwidth is removed. And, when the bandwidth and the frequency resolution are set high for more accurate results, the computational complexity of the proposed method is less than that of the conventional one.

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Stabilization of the Perovskite Phase and Electrical Properties of Ferroelectrics in the Pb2(Sc,Nb)O6 System

  • Kim, Yeon Jung
    • Applied Science and Convergence Technology
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    • v.24 no.6
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    • pp.224-227
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    • 2015
  • Ferroelectric $Pb_2(Sc,Nb)O_6$ were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were $1350^{\circ}C$ for 25 minutes and $1400^{\circ}C$ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the $Pb_2(Sc,Nb)O_6$ compositions Pyrochlore phase showed about 2% in all $Pb_2(Sc,Nb)O_6$ specimens. It expands the growth of crystals in samples sintered at $1400^{\circ}C$ than $1350^{\circ}C$, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at $1350^{\circ}C$ and $1400^{\circ}C$ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in $Pb_2(Sc,Nb)O_6$ compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.

A Novel Scheme for Sliding-Mode Control of DC-DC Converters with a Constant Frequency Based on the Averaging Model

  • He, Yiwen;Xu, Weisheng;Cheng, Yan
    • Journal of Power Electronics
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    • v.10 no.1
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    • pp.1-8
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    • 2010
  • A new scheme for sliding-mode control (SMC) of DC-DC converters with a constant switching frequency is proposed. The scheme is based on the averaging model and the output signal of the controller is $d^+$ or $d^-$ instead of the on or off signal of a direct sliding-mode (SM) controller or the continuous signal d = $u_{eq}$ of an indirect SM controller. Two approaches using the new scheme are also proposed and the design procedures for a buck converter are given in detail. The first approach called constant $d^+$ and $d^-$ SMC is simple, cost effective and dynamically fast. In order to improve the dynamic characteristics of the reaching phase and to alleviate chattering, the second approach called reaching law SMC is also presented. Analyses and simulation results demonstrate the feasibility of the proposed scheme.

Free Vibrations of Tapered Columns with Constant Volume (일정체적 변단면 기둥의 자유진동)

  • 이병구;이태은;최규문;송주한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.417-422
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    • 2002
  • The main purpose of this paper is to determine the dynamic optimal shapes of tapered column with constant volume. The linear, parabolic and sinusoidal tapers with the regular polygon cross-section are considered, whose material volume and span length are always held constant. The ordinary differential equation including the effect of axial load is applied to calculate the natural frequencies. The Runge-Kutta method and Regula-Falsi methods are used to integrate the differential equation and compute the frequencies, respectively. Then the dynamic optimal shape whose lowest natural frequency is highest is determined by reading the critical value of the frequency versus section ratio curve plotted by the frequency data. In the numerical examples, the tapered columns are analysed and the numerical result of this study are shown in table and figures.

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A new low dielectric constant barium titanate - poly (methyl methacrylate) nanocomposite films

  • Upadhyay, Ravindra H.;Deshmukh, Rajendra R.
    • Advances in materials Research
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    • v.2 no.2
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    • pp.99-109
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    • 2013
  • In the present investigation, nanocomposite films with poly(methyl methacrylate) (PMMA) as a polymer matrix and barium titanate as a filler were prepared by solution casting method. Barium titanate nano particles were prepared using Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide as precursors and tetra methyl ammonium hydroxide (TMAH) as a base. The nanocomposite films were characterized using XRD, FTIR, SEM and dielectric spectroscopy techniques. Dielectric measurements were performed in the frequency range 100 Hz-10 MHz. Dielectric constant of nanocomposites were found to depend on the frequency, the temperature and the filler fraction. Dissipation factors were also influenced by the frequency and the temperature but not much influenced by the filler fractions. The 10 wt% of BT-PMMA nanocomposite had the lowest dielectric constant of 3.58 and dielectric loss tangent of 0.024 at 1MHz and $25^{\circ}C$. The dielectric mixing model of Modified Lichtenecker showed the close fit to the experimental data.

Influence of Effective Piezoelectric Properties on Performance of Piezoelectric Accelerometer for Vibration Measurements (진동 측정용 압전형 가속도센서의 압전특성 효과)

  • 권정락
    • Journal of the Korean Ceramic Society
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    • v.32 no.8
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    • pp.945-949
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    • 1995
  • In order to investigate the performance of compression-type accelerometer on piezoelectric properties, PZT materials have been studied. The ring-shaped piezoelectric elements were prepared using commercial PZT powders by conventional ceramic process. Their estimated relative dielectric constant, piezoelectric charge constant (d33) and voltage constant (g33) values showed 390∼3400, (90∼593)×10-12 C/N and (19.5∼40.5)×10-3 V-m/N, respectively. The charge sensitivity of accelerometer is proportional to the piezoelectric charge constant value (d33) of PZT, but its voltage sensitivity is related with the piezoelectric voltage constant (g33). Since the mounted resonance frequency and sensitivity are dependent on the seismic mass as well as physical charateristics and size of PZT elements, the suitable considerations between two components are required for accelerometer's design.

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Quasi-Resonant PWM Converter Controlled by Constant Frequency (일정한 주파수로 제어되는 쿼지 공진형 PWM 컨버터)

  • Joung, Gyubum
    • Journal of Satellite, Information and Communications
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    • v.12 no.2
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    • pp.28-32
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    • 2017
  • In this paper, a quasi-resonant PWM converter, which is controlled by constant frequency, has been suggested. As quasi-resonant converter, the switches of the suggested converter has soft switching characteristics, which can operate to high frequency with high efficiency. Comparing with varied controlled frequency of quasi-resonant converter for controlling output voltage, the suggested converter has advantages which optimize filter and EMI filter design at constant switching frequency. The converter has been analyzed by switch mode analysis which verified soft switching operation. Also, the PWM operation and characteristics of the converter are verified by simulation and experiment of 100 kHz DC-DC converter.