Deuk-Young Han

Effect of kimchi powder level and drying methods on quality characteristics of breakfast sausage

This study was conducted to determine the effect of the addition of kimchi powder on the quality characteristics of meat batter and breakfast sausage. Breakfast sausages were supplemented with freeze dried kimchi powder (FKP) or hot air dried kimchi powder (HKP) at levels of 1% (FKP-1 and HKP-1) or 2% (FKP-2 and HKP-2). The emulsion stability, cooking yield, and apparent viscosity in meat batters improved with increments of kimchi powder (p<0.05). Increased levels of kimchi powder in breakfast sausage decreased the L(∗) value, pH, and springiness, and increased the a(∗) value, b(∗) value, hardness, chewiness, and gumminess (p<0.05). Sensory evaluations indicated that a higher overall acceptability was attained when the kimchi powder was added to breakfast sausage at a level of 2%.

Design and fabrication of piezoelectric ceramic transformers for the LCD backlight

This paper describes a type of piezoelectric transformer with improved design principles. It consists of a thin rectangular piezoelectric ceramic plate having two input electrodes and one output electrode. The length of each input and output electrode is nearly one third of piezoelectric transformer itself. In the driving section, the ceramic plate is poled in the thickness direction reversely with each other, and has electrodes on both main faces. The electric input near its fundamental resonance frequency is applied to the driving section in parallel and the output voltage from the generating section is connected to the resistor load. Its equivalent circuit is derived from the Masons model. The frequency characteristics near the resonance frequency under no load have been investigated. Moreover, using this piezoelectric transformer, we measured the LCD backlight characteristics.

A TRANSIENT MODEL FOR INSULATED GATE BIPOLAR TRANSISTORS (IGBTs)

In this paper, we present a physics-based model for the non punch-through (NPT) insulated gate bipolar transistor (IGBT) during transient turn off period. The steady state part of the model is derived from the solution of the ambipolar diffusion equation in the drift region of the NPT IGBT. The transient component of the model is based on the availability of a newly developed expression for the excess carrier concentration in the base. The transient voltage and current are obtained both numerically and analytically from this model. The theoretical predictions of both approaches are compared with experimental data and found to be in good agreement.

D.C. characteristic of MESFETs at High Temperatures

Abstract The ability of GaAs MESFET to operate over a wide temperature range requires accurate models to simulate the temperature dependence of various device parameters. In this paper, a new analytical model for the threshold voltage of MESFETs operating beyond 250°C is introduced. The model takes into account the effect of the gate leakage current on threshold voltage and is used successfully to overcome the shortcomings of existing models in the literature in matching the experimental data at temperatures higher than 250°C. The model is used to predict the drain current dependence on temperature in both the subthreshold and saturation region.

Operation Characteristics of Bypass Diode for PV Module

In this paper, an I-V characteristics of bypass diode has been studied by counting the shading effect in photovoltaic module. The shadow induces hot spot phenomenon in PV module due to the increase of resistance in the current path. Two different types of PV module with and without bypass diode were fabricated to expect maximum output power with an increasing shading rate of 5 % on the solar cell. Temperature distribution is also detected by shading the whole solar cell for the outdoor test. From the result, the bypass diode works properly over 60 % of shading per cell with constant output power. Maximum power generation in case of solar cell being totally shaded with bypass diode decreases 41.3 % compared with the one under STC(Standard Test Condition). On the other hand, the maximum output power of the module without bypass diode gradually decreases by showing hot spot phenomenon with the increase of shading ratio on the cell and finally indicates 95.5 % of power loss compared with the output under STC. Finally the module temperature measured increases around higher than that under STC due to hot-spots which come from the condition without bypass diode. It has been therefore one of the main reasons for degrading the PV module and shortening the durability of the PV system.

The study on optimal design and optical properties of LED module for full-color displays

In this paper, design principle for the optimization of the full-color display is suggested to show nearest white light by mixing high radiance R,G,B LEDs with appropriate proportional indices. By counting these three colors to be additive mixing and producing white light color contrasted to negative mixing, each number of LEDs is theoretically deduced and designed with several shapes of chips for the full-color displays. Finally theoretical predictions are compared with the measured data for different type of display designs.

Consideration of Electrical Properties in Field-aged Photovoltaic Module

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16 % drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20 % mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to 3 and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around 15 at the encapsulant discoloration spot of PV array.

Bender Typed Piezoelectric Multilayer Actuator

A Bender typed Multilayer Actuator(BMA) for decreasing the depolarization effect was designed and fabricated. Unlike bimorph and multimorph actuators in which depolarization occurred, the BMA did not generate depolarization because the polarization and the electric field directions are the same. The simulated results indicate that higher displacement of the BMA can be achieved by increasing input voltage. Compared with the multimorph actuator, the proposed actuator is expected to extend a life time as well as acceptable voltage range.

Design and fabrication of SAW gas sensor with resonator structure

In this paper, SAW (Surface Acoustic Wave) resonator is used to detect flammable and explosive gases. SAW resonators are designed by using COM (Coupled Mode) theory and made through IC fabrication processes. The gases used in this experiment are CH/sub 4/, and H/sub 2/. Substrate of SAW device is 128/spl deg/ X rotated LiNbO/sub 3/. Resonant frequency of resonator is designed to match at 99.8 Hz. A dual resonator oscillator circuit, composed of reference SAW resonator and sensing SAW resonator is used to compensate for the effects of temperature and humidity. Finally, device performances have been examined and proved to be in excellent agreement with theoretical predictions.

A Simulation of Photocurrent Loss by Reflectance of the Front Glass and EVA in the Photovoltaic Module

The solar cell is a device to convert light energy into electric, which supplies power to the external load when exposed to the incident light. The photocurrent and voltage occurred in the device are significant factors to decide the output power of solar cells. The crystalline silicon solar cell module has photocurrent loss due to light reflections on the glass and EVA(Ethylene Vinyl Acetate). These photocurrent loss would be a hinderance for high-efficiency solar cell module. In this paper, the quantitative analysis for the photocurrent losses in the 300-1200 wavelength region was performed. The simulation method with MATLAB was used to analyze the reflection on a front glass and EVA layer. To investigate the intensity of light that reached solar cells in PV(Photovoltaic) module, the reflectance and transmittance of PV modules was calculated using the Fresnel equations. The simulated photocurrent in each wavelength was compared with the output of real solar cells and the manufactured PV module to evaluate the reliability of simulation. As a result of the simulation, We proved that the optical loss largely occurred in wavelengths between 300 and 400 nm.