• 약학회지
• /
• 제34권5호
• /
• pp.302-310
• /
• 1990

A study has been made of the Korean bentonite aqueous suspension contrast with American bentonite by means of XRD IR swelling, gel formation and rheogram at various conditions such as concentration, temperature and pH. The Korean bentonite was identified as montmorillonite clay containig a small proprotion of crystoballite and mordenite, and its swelling power were acceptable for requirements of Korean pharmacopeia regulations though its values were not satisfied. Korean bentonite swelled to 10 times and American one did to 15 times compared to its bulkiness of powder. The rheogram of Korean bentonite suspension reveals bulged pseudoplatic flow with yield value at higher concentration and pseudoplastic flow without yield value at lower concentration. The higher the concentration, the greater were the apparent viscosity and hysteresis loop. Korean bentonite suspension showed insignificant temperature dependence on both apparent viscosity and hysteresis loop and it was more temperature dependent on viscosity but less on hysteresis loop than those of American sample. The pH dependence was so high on viscosity that apparent minimum value was near pH 7 and maximum value at pH 3 or 7. The hysteresis loop appeared minimum over the pH range 5-7 and maximum near pH 3 or 11. The Korean bentonite was inferior to the American bentonite in swelling volume, gel formation, thioxotropy, however, it would be possible to improve the quality of Korean bentonite by developing the method of purification for bentonite clay.

• 환경영향평가
• /
• 제29권5호
• /
• pp.323-337
• /
• 2020

국내 최대 상수원인 팔당호를 대상으로 기온과 수온의 변화를 살펴보고 장기간 기온과 수온의 연속 자료를 활용하여 이력 현상을 살펴보았다. 계절 Mann-Kendall을 적용한 팔당호 인근 양평의 기온 변화 추세는 지난 47년간(1973~2019) 증가(0.048 ℃/yr)에 비하여 최근 27년간(1993~2019) 기온의 증가(0.060 ℃/yr)가 컸다. 팔당호와 유입 하천에서 수온은 기온과의 상관성이 높으나(R > 0.9, p < 0.005) 호소인 팔당댐앞 지점에서의 수온은 하천 수온 상승에 비하여 느리고 기온 하강기에 들어서 수온이 서서히 감소하였고 수심 평균 수온도 상승기와 하강기 모두 호소 표층보다 변화가 더디게 나타났다. 이는 호소가 하천보다 수체 규모 면에서 크고 체류시간이 길기 때문에 열에너지를 흡수하고 감소하는데 시간이 걸리는 수온의 이력 현상이 크게 작용하는 것으로 판단된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 C
• /
• pp.1472-1475
• /
• 1996

D-E hysteresis loops have been measured for the 65/35 mole % copolymer of vinylidene fluoride and trifIuoroethyIene over wide temperature range. The results were analyzed and discussed. The remanent polarization and the coercive field at room termperature were estimated to be 75 $mC/m^3$ and 55 MV/m respectively. D-E hysteresis loops were observed even below the glass transiation temperature$-20^{\circ}C$) and the remanent polarization and the coercive field were larger than larger, as the temperature lower. It seems that the remanent polarization and the coercive field depend on the amorphous region as well as crystalline region in this copolymer. And the ferroelectric-to-paraelectric phase transition was observed at $90^{\circ}C$ on heating and $80^{\circ}C$ on cooling. Double hysteresis loops were observed at the temperature($85^{\circ}C$) of paraelectric phase.

• Tribology and Lubricants
• /
• 제14권4호
• /
• pp.44-50
• /
• 1998

This paper describes the simulation of the levitation force between permanent magnet and high Tc(critical temperature) superconductor(HTSC). Levitation force is evaluated numerically on the basis of the magnetic vector potential method and the critical state model. The superconductor is approximated to 2-D slab model. By performing computations, the following characteristics have been investigated: the process of the generation of hysteresis, the various hysteretic behaviors. The characteristics of hysteresis are important for the application to magnetic bearing, for the damping and the nonlinear stiffness is related to hysteresis.

• 한국세라믹학회지
• /
• 제51권6호
• /
• pp.591-597
• /
• 2014

A poled lead zirconate titanate (PZT) rectangular parallelepiped specimen was subjected to through-thickness electric fields at five loading rates and four temperatures. The rates of the electric field were 0.01, 0.10, 0.25, 0.50, and $1.00MVm^{-1}s^{-1}$; the temperatures were 20, 50, 80, and $110^{\circ}C$. From the measured polarization hysteresis responses, the so-called reference remnant polarization and strains were calculated. Using the calculated reference remnant polarization hysteresis loops, the effects of loading rates and temperature were discussed; using the calculated reference remnant strains, strain butterfly loops were calculated and compared with observations.

• 한국군사과학기술학회지
• /
• 제18권2호
• /
• pp.109-114
• /
• 2015

A method to compensate a bias hysteresis error of the ring laser gyro using the rate of temperature is proposed in this paper. Until now, we generally have measured and compensated the error of gyro and accelerometer using the temperature. However, we utilize the measured values of the temperature dependent error elements on the temperature rate in navigation system level. We show through experiments that the proposed method can improve the navigation performance and be very effective.

• 한국자동차공학회논문집
• /
• 제25권1호
• /
• pp.66-73
• /
• 2017

In this work, graphene platelets were introduced into wax in an automotive electronic controlled thermostat for the purpose of enhancing its thermal-conductive property and improving response performance. Graphene content ranging from 10 % to 20% was added into and mixed with the wax to investigate the effect of graphene amounts on the performance of an automotive electronic controlled thermostat in terms of response time, hysteresis and melting temperature. The experimental results revealed that graphene in wax contributed to a reduction in the response time and hysteresis of an automotive electronic controlled thermostat. As a consequence, important improvement in thermal sensitivity, full lift, melting temperature and hysteresis were obtained. The thermal response of wax with graphene content of 20 % was improved by 25 %, as compared to that of wax with Cu content of 20 %. Hysteresis of wax with graphene was reduced by $0.6^{\circ}C$ as compared to that of wax with Cu content. The melting temperature of wax is lowered and hysteresis is also improved with increased graphene content of wax in an electronic controlled thermostat. We hope that this study can help further the transition of nano-fluid technology from small-scale research laboratories to industrial application in the automotive sector.

• 한국산림과학회지
• /
• 제1권1호
• /
• pp.1-6
• /
• 1962

Hysteresis Loops explaining relationship between E.M.C. and relative humidities of some commercial woods grown in Korea which have not been inspected were studied. Because of Hysteresis Loops are differently constructed among species, the loop of each species is necessary to plot in order to apply for seasoning of wood directly. Therefore relationship between E.M.C. and relative humidities, and Hysteresis Loops were inspected and compaired between species. Small sized ($3{\times}3{\times}1.3cm$) twenty pieces of wood blocks for each species were taken from log which cut few years ago and already attained air dry condition. Five relative humidity conditions (9, 32, 58, 82 and 91%) were controlled to keep constant in the cabinet under temperature $25^{\circ}C$. According to the results, it is concluded that there are considerable differences on the E.M.C. among two types of sorption, eight species and five different relative humidity conditions. Adsorption and desorption curves are showing characteristic Sigmeid Curves and desorption curves always are on the adsorption curves at all compaired species. Average hysteresis ratio is 0.75, the constructed loops of tested species are showing open hysteresis generally and flatten loop constructions of Qnerets aemitissima and Robinia pseudoaeaeia of hard wood species than other soft wood are considered to be established by differences of stability between hard and soft wood.

• 한국정보전자통신기술학회논문지
• /
• 제2권1호
• /
• pp.3-9
• /
• 2009

AMOLED 디스플레이는 LCD에 비해 넓은 시야각, 빠른 응답 속도, 박막화의 용이성 등의 많은 장점들을 갖고 있으나 불균일한 TFT의 전기적 특성과 전원선의 전압 강하에 의한 휘도 불균일, 잔상 현상 및 수명 등과 같은 많은 문제점들이 있다. 이 중에서 본 논문에서는 구동 TFT 소자의 hysteresis 현상에 의해 발생하는 가역적 잔상 현상을 개선하고자 한다. TFT의 hysteresis 특성을 개선하기 위해 게이트 산화막 증착 전에 표면 처리 조건을 변경하였다. 게이트 산화막 증착 전에 실시한 자외선 및 수소 플라즈마 표면 처리는 게이트 산화막과 다결정 실리콘 박막 사이의 계면 trap 밀도를 $3.11{\times}10^{11}cm^{-2}$로 감소시켰고, hysteresis 레벨을 0.23 V로 줄였으며 출력 전류 변화율을 3.65 %로 감소시켰다. 자외선 및 수소 플라즈마 처리를 행함으로써 AMOLED 디스플레이의 가역적 잔상을 많이 개선할 수 있을 것으로 기대된다.

• Journal of the Korean Wood Science and Technology
• /
• 제44권2호
• /
• pp.191-203
• /
• 2016

To investigate the dynamic sorptive and hygroexpansive behaviors of wood by different cyclic hygrothermal changing effects, poplar (populus euramericana Cv.) specimens, were exposed to dynamic sorption processes where relative humidity (RH) and temperature changed simultaneously in sinusoidal waves at 75-45% and $5-35^{\circ}C$ (condition A) and where RH changed sinusoidally at 75-45% but temperature was controlled at $20^{\circ}C$ (condition B), both for three cyclic periods of 1, 6, and 24 h. Moisture and dimensional changes measured during the cycling gave the following results: Moisture and transverse dimensional changes were generally sinusoidal. Moisture and dimensional amplitude increased with increasing cyclic period but all were lower for thicker specimens. The amplitude ratio of condition A to condition B ranged from 1.0 to 1.6 with the maximum value of 1.57 occurring at the shortest cyclic period, not as much as expected. T/R increased as cyclic period increased or specimen thickness decreased. T/R from condition B was weaker than that from condition A. Sorption and swelling hysteresis existed in both conditions. Sorption hysteresis was negatively related to cyclic period but in positive correlation with specimen thickness. Sorption hysteresis was found more obvious in condition B, while moisture sorption coefficient and humidity expansion coefficient showed the opposite results.