• Food Science and Preservation
• /
• v.24 no.4
• /
• pp.505-509
• /
• 2017

Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to $40^{\circ}C$ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of $1/(m-m_0)$ vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters ($E_a$ and $k_0$) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.635-636
• /
• 2006

A self-biased CMOS current reference is described which provides supply and temperature independent bias current. The supply independency is obtained by subtracting two bias currents which have the same supply dependency. Unlike the conventional self-bias CMOS current reference, excellent supply independency can be obtained even with the minimum channel length devices and thus smaller area implementation becomes possible. The supply independent bias current is then applied to a temperature compensating circuit and as a result supply and temperature independent bias current is obtained. The current reference has been implemented in a $0.25{\mu}m$ standard CMOS technology. The active silicon area is only $45{\mu}m{\times}45{\mu}m$. The simulated temperature coefficient is 64ppm/$^{\circ}C$ in temperature range between $0^{\circ}C$ and $120^{\circ}C$. Supply voltage can be as low as 1.3V and the supply dependency of the current reference is measured to be smaller than 4500ppm/V. While providing $10.25{\mu}A$ output current, the current reference consumes $160{\mu}W$.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.12 no.1
• /
• pp.67-77
• /
• 2008

Seismic isolation has been studied continuously as a solution of the seismic engineering to reduce the sectional forces and the damages of structures caused by earthquakes. To certify reliable design and installation of the seismic isolation systems, seismic isolation bearings should be fabricated under well planned quality control process, and proper evaluation tests for their seismic performance should be followed. In this study, shear property evaluation tests for the lead rubber bearings(LRB) and the rubber bearings(RB) were implemented and the temperature dependency tests were also implemented to evaluate the changes of shear properties according to the changes of temperature. After evaluation tests, the measured shear properties were compared to their design values and their deviation was analyzed comparing with the allowable error ranges specified in Highway Bridge Design Specifications. These results showed that a considerable number of isolation bearings have so large deviations from their design values that their error ranges were over or very close to the allowable ranges. And the test results for temperature dependency showed that the shear properties of isolation bearings would be changed in great degree by the change of temperature during their service period. If these two types of changes in their shear properties are superposed, it would possible that the changes of shear properties from their original design values are over than 50%.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.91-112
• /
• 2016

In this paper, post-buckling behavior of sandwich plates with functionally graded (FG) face sheets under uniform temperature rise loading is examined based on both sinusoidal shear deformation theory and stress function. It is supposed that the sandwich plate is in contact with an elastic foundation during deformation, which acts in both compression and tension. Thermo-elastic non-homogeneous properties of FG layers change smoothly by the variation of power law within the thickness, and temperature dependency of material constituents is considered in the formulation. In the present development, Von Karman nonlinearity and initial geometrical imperfection of sandwich plate are also taken into account. By employing Galerkin method, analytical solutions of thermal buckling and post-buckling equilibrium paths for simply supported plates are determined. Numerical examples presented in the present study discuss the effects of gradient index, sandwich plate geometry, geometrical imperfection, temperature dependency, and the elastic foundation parameters.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.23 no.5
• /
• pp.535-541
• /
• 2010

In this paper, we have derived a continuum-based adjoint design sensitivity of general performance functionals with respect to Young' modulus and heat conduction coefficient for steady-state nonlinear thermoelastic problems. An adjoint equation for temperature and displacement fields is defined for the efficient computation of the coupled field design sensitivity. Through numerical examples, we investigated the mesh dependency of the topology optimization method in the thermoelastic problems. Also, comparing the dominant loading cases of thermal and mechanical ones, the loading dependency of topology design optimization in coupled multi-physics problems is investigated.

• Progress in Superconductivity and Cryogenics
• /
• v.17 no.3
• /
• pp.47-50
• /
• 2015

The high temperature superconducting (HTS) magnet has been developed for the high magnetic field applications such as NMR, MRI and other industrial machinery. In designing process of these HTS magnets, the accurate estimation on the critical current (Ic) is essential to predict and secure the electromagnetic performance. The critical current of 2G HTS tape has anisotropic Ic degradation characteristics with the application of magnetic field - angular dependency of critical current. It is known that the perpendicular magnetic field to the face of HTS tape makes dominant degradation on the critical current for conventional 2G HTS tape. However, recently developed 2G HTS tape has more complex characteristics due to the artificial pinning center. Therefore, the method for Ic estimation reflecting such characteristics of 2G HTS tape needs to be devised. The method considering the angular dependency is introduced in this paper. And the result of newly devised method is compared with that of previous method.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.707-710
• /
• 1998

This paper presents a new voltage down converter(VDC) for low power, high speed DRAM. This VDC Consists of RVG(Reference Voltage Generator) and Driver Circuit. And it is independent of temperature variation, and Supply Voltage. Using weak inversion region, this RVG dissipates low power. Internal Voltage Source of this VDC is stable in spite of high speed operation of memory array. This circuit is designed with a $0.65\mu\textrm{m}$ nwell CMOS technology. In HSPICE simulation results, Temperature dependency of this RVG is $20\muV/^{\circ}C,$ supply voltage dependency is $\pm0.17%,$ $VCC=3.3V\pm0.3V,$ and current dissipation is $5.22\muA.$ Internal voltage source bouncing of this VDC is smaller than conventional VDC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.4
• /
• pp.396-403
• /
• 2004

The dielectric properties of Y-ray irradiated and thermally aged polyetheretherketone (PEEK) have been investigated. Results of the temperature dependency of dielectric properties indicated that the glass transition temperature of aged PEEK increased as radiative and thermal ageing. The frequency dependency of dielectric properties implied that the magnitude of radiation and thermal induced dipoles, ions increased as radiative and thermal ageing. The values of relaxation intensity calculated using Cole-Cole's circular arc can be useful for evaluation of degradation level of PEEK.

• Journal of the Korean Ceramic Society
• /
• v.45 no.1
• /
• pp.69-74
• /
• 2008

The effects of $SiO_2$ impurity on the high temperature resistivities of AIN ceramics have been investigated. When $SiO_2$ was added into 1 wt% $Y_2O_3$-doped AIN, DC resistivities have decreased and electrode polarizations disappeared. Impedance spectroscopy showed two semi-circles at $600^{\circ}C$, which were attributed to grain and grain boundary, respectively. $SiO_2$ doping had more significant effects on the grain resistivity than grain boundary resistivity, implying that doped Si acted as a donor in AIN lattice. In addition, voltage dependency of DC resistivity was observed, which might be related to dependency of size of grain boundary semi-circle on the bias voltage in impedance spectroscopy.

• Journal of the Optical Society of Korea
• /
• v.16 no.4
• /
• pp.401-408
• /
• 2012

The amplitude error of phase modulator used in closed-loop fiber optic gyroscope has occurred by the temperature dependency of the electro-optic coefficient, and also can be due to the square-wave dither signal which is generally applied for eliminating the deadzone. This error can cause bias drift and scale factor error. This paper analyzes the temperature dependency of the modulation amplitude and the relationship with the scale factor of the gyroscope, and deals with an amplitude control method. The error calculation logic considering the dither signal is implemented on the signal processing module. The result of experiments from a prototype gyroscope shows the effect of the modulation amplitude control and a considerable improvement on performances.