• Title, Summary, Keyword: Temperature dependence

Search Result 2,063, Processing Time 0.04 seconds

Temperature Dependence of Energy Gap and Thermodynamic Function Properties of Coblt-doped $Cd_4GeS_6$Single Crystals (Cobalt를 첨가한 $Cd_4GeS_6$ 단결정에서 Energy Gap의 온도의존성 및 열역학적 함수 추정)

  • 김덕태
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.11 no.9
    • /
    • pp.693-699
    • /
    • 1998
  • In this work $Cd_4GeS_6:Co^{2+}$(0.5mole%) single crystals were grown by the chemical transporting reactiov(CTR) method using high purity(6N) elements. The grown single crystals crystallized in a monoclinic structure(space group Cc). The direct optical energy gap of this single crystals was found to be 2.445eV at 300K and the temperature dependence of optical energy gap was fitted well to Varshni equation. But at temperatures lower than 70K an anomalous temperature dependence of the optical energy gap was obtained. This anomalous temperature dependence accored well with the anomalous temperature dependence of the unit cell volume. Also, the entropy, enthalpy and heat capacity were deduced from the temperature dependence of optical energy gaps.

  • PDF

A Study on the Strain Rate and Temperature Dependence of Yield Stress of Al-Li Alloy (Al-Li합금의 항복응력에 대한 변형속도 및 온도의존성에 관한 연구)

  • Oh, Chang-Sup;Han, Chang-Suk
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.24 no.6
    • /
    • pp.311-317
    • /
    • 2011
  • The effect of strain rate on the yield stress of an Al-Li alloy has been investigated at temperatures between 77 and 523 K and over the strain rate range from $1.77{\times}10^{-4}s^{-1}$ to $1.77{\times}10^{-2}s^{-1}$. At testing temperatures below 373 K, the yield stress is almost independent of strain rate at any aging stage. At testing temperatures above 373 K, the yield stress increases linearly with the logarithm of strain rate, and the strain rate dependence increases with increasing testing temperature. The yield stresses of under-aged alloy at temperatures between 373 and 473 K at high strain rates are greater than the yield stress at 77 K. For the alloy under-aged or aged nearly to its peak strength, the temperature range within which the positive temperature dependence of yield stress appears expands to the higher temperature side with increasing strain rate. The strain rate dependence of the yield stress is slightly negative at this aging stage. The yield stress of the over-aged alloy decreases monotonically with decreasing strain rate and with increasing testing temperature above 373 K. The modulus normalized yield stress is nearly constant at testing temperatures below 373 K at any strain rate investigated. And, strength depends largely both on the aging conditions and on the testing temperature. The peak positions in strength vs. aging time curves shift to the side of shorter aging time with increasing testing temperature. For the specimens aged nearly to the peak strength, the positive temperature dependence of yield stress is observed in the temperature range. The shift of peak positions in the aging curves are explained in terms of the positive temperature dependence of cutting stress and the negative temperature dependence of by-passing stress.

Description of Temperature Dependence of Critical Micelle Concentration

  • Kim, Hong-Un;Lim, Kyung-Hee
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.10
    • /
    • pp.1449-1454
    • /
    • 2003
  • A new equation has been derived on the basis of ${\delta}G^o$ = -RT lnK, linear behavior of the enthalpy of micellization with temperature, and the Gibbs-Helmholtz relation. It describes correctly the dependence of critical micelle concentration $(X_{CMC})$ on temperature and has yielded excellent fitting results for various surfactant systems. The new equation results in the linear behavior of the entropy of micellization with temperature and accounts for the compensation phenomena observed for the micellization in aqueous solutions, along with the linear dependence of the enthalpy of micellization on temperature. These results imply that the new equation of $X_{CMC}(T)$ accounts for the temperature dependence of CMC correctly.

Prediction of Temperature Dependence of Lower Explosive Limits for Paraffinic Hydrocarbons (파라핀족탄화수소의 폭발하한계의 온도의존성 예측)

  • 하동명
    • Journal of the Korean Society of Safety
    • /
    • v.15 no.3
    • /
    • pp.71-77
    • /
    • 2000
  • The aim of this study is to investigate the temperature dependence of the lower explosive limit(LEL) at elevated temperature. The temperature dependence of the lower explosive limit is one of the significant indices of flammability and combustibility. By using the literature data, the new equations for predicting the temperature dependence of the lower explosive limits for paraffinic hydrocarbons are proposed. The values calculated by the proposed equations were a good agreement with the literature data. It is hoped eventually that this proposed equations will support the use of the prediction for the lower explosive limit and the flash points of the flammable mixtures.

  • PDF

Validation Test for Transient Hot-wire Method to Evaluate the Temperature Dependence of Nanofluids (나노유체 열전도율의 온도의존성 평가를 위한 비정상열선법의 시험방법)

  • Kang, Kyoung-Min;Lee, Shin-Pyo
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.31 no.4
    • /
    • pp.341-348
    • /
    • 2007
  • One of the controversial research issues on nanofluids is the temperature dependence of the thermal conductivity of nanofluids, that is, whether it will increase or decrease according to the temperature rise. To evaluate precisely the thermal conductivity behavior of nanofluids, a systematic way of validation experiments for the measuring instrument has been highly recommended. In this paper, procedure of the validation test for transient hot-wire method using the temperature dependence of the base fluids was explained comprehensively and the comparison of the temperature dependence of water-$Al_2O_3$ nanofluids is made between the present work and that of Das et al.

Strain Dependence of Stress Relaxation in Nylon 6 (Nylon 6의 곤장대변화영역에 있어 응력완화거동의 실험적 고찰)

  • 장동호
    • Textile Science and Engineering
    • /
    • v.10 no.1
    • /
    • pp.14-17
    • /
    • 1973
  • Stress relaxation measurements under the various strains ranging from 5% to 20% have been carried out for Nylon 6 filaments at various temperatures of 18$^{\circ}C$ to 160$^{\circ}C$. The results are as follows. 1) Strain dependence upon stress relaxation decreases as the temperature increases. 2) Temperature dependence upon relative relation is found to be great and the relative relaxation increases as the temperature increases. 3) Degree of strain dependence can be modified by changing the relation and the temperatures. (Received Feb. 10, 1973)

  • PDF

Statistical Analysis on the Temperature Dependence and Long-Term Change of Relative Humidity Sensors (상대습도계의 온도 의존성과 경년변화의 통계적 분석)

  • Kim, Jong Chul;Choi, Byung Il;Woo, Sangbong;Yang, Inseok
    • Journal of Sensor Science and Technology
    • /
    • v.21 no.6
    • /
    • pp.420-424
    • /
    • 2012
  • We have investigated temperature dependence and long-term change of humidity measurement from 32 relative humidity sensors. The readings of the humidity sensors depended not only the reference humidity, but also temperature of the chamber. Approximately, the temperature dependence of the humidity sensor in average was 0.05 %R.H./$^{\circ}C$ in the temperature range from $5^{\circ}C$ to $55^{\circ}C$. For humidity sensors that have an internal temperature compensation circuit, the resulting temperature dependence was weaker by 20%. It should be also noted that for the humidity sensors used in this work underwent ${\pm}3$ %R.H. change per year for level of confidence of 95%. The users of relative humidity sensors may refer this value as a minimum change when they set the calibration interval of the humidity sensors.

Temperature Dependence of the Electro-optic Characteristics in the Liquid Crystal Display Switching Modes

  • Jeon, Eun-Jeong;Srivastava, Anoop Kumar;Kim, Mi-Young;Jeong, Kwang-Un;Choi, Jeong-Min;Lee, Gi-Dong;Lee, Seung-Hee
    • Journal of Information Display
    • /
    • v.10 no.4
    • /
    • pp.175-179
    • /
    • 2009
  • As the physical properties of nematic liquid crystals vary with respect to temperature, the performances of liquid crystal displays (LCDs) are highly dependent on temperature. Additionally, it is well known that the electro-optic characteristics of LCDs, such as transmittance and threshold voltage, also rely on the LCD switching modes. The temperature dependence of the electro-optic characteristics of the wide-viewing-angle LCD modes, such as in-plane switching (IPS), multidomain vertical alignment by patterned electrode (PVA), and fringe-field switching (FFS), have been studied, and the results showed that the FFS mode has lower temperature dependence compared to the IPS and PVA modes. Since the liquid crystal (LC) reorients in different ways in each mode, this result is associated with the temperature dependence of LC's bend and twist elastic constants, and also with the position of the main reorientation, either in the middle or on the surface of the LC layer.

Temperature dependence and Voltage dependence of Aramide Paper (아라미드계 절연지(Aramid paper)의 온도의존성과 전압의존성)

  • Park, Hyoung-Jun;Lee, Jong-Pil;Park, Hee-Doo;Sin, Jong-Yeol;Lee, Soo-Won;Hong, Jin-Woong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.465-468
    • /
    • 2004
  • In this paper, the properties of temperature dependence and voltage dependence of Aramid paper were studied to understand electrical characteristics, to be regarded as the excellent insulation. Aramid paper and pressboard had being applied various motor, generator. We used to Finite Elemental Method of simulation tool, and improved optimal insulating design of insulating Aramid according to calculated those.

  • PDF

Temperature Dependence of Dielectric Properties of BaTiO$_3$ doped with Nb$_2$O$_5$ and CoO (Nb$_2$O$_5$와 CoO의 복합첨가가 BaTiO$_3$ 유전특성의 온도안전성에 미치는 효과)

  • 최광휘;황진현;한영호
    • Journal of the Korean Ceramic Society
    • /
    • v.35 no.8
    • /
    • pp.864-870
    • /
    • 1998
  • The effect of {{{{ {{Nb }_{2 }O }_{5 } }} and CoO addition on the temperature dependence of the {{{{ {BaTiO }_{3 } }}-based ceramic capa-citor has been studied. X7R with moderate temperature dependence has been developed by means of pre-cisely controlled {{{{ {{Nb }_{2 }O }_{5 } }}/CoO ratio. Dielectric constant(K) and dissipation factor(DF) were 3500 and 1.5% respectively. As the content of {{{{ {{Nb }_{2 }O }_{5 } }} was increased the curie temperature(Tc) was shifted to lower tem-perature and the dielectric constant at Tc was decreased. The proper addition of CoO with {{{{ {{Nb }_{2 }O }_{5 } }} improved the temperature dependence of dielectric properties of the {{{{ {BaTiO }_{3 } }}-based ceramic capacitor.

  • PDF