EFFECT OF SILICON CARBIDE PASSIVATION FILM ON THE RESONANCE CHARACTERISTICS OF CANTILEVER

ABSTRACT

We have used silicon carbide (SiC) thin films as an insulating material of the PZT micro cantilevers for electrical and biological passivation. The use of SiC thin films as a passivation layer of the PZT microcantilevers is also seemingly viable to insure the high mass sensitivity as well as the stable passivation. In this study, we report the effect of SiC passivation layer on the performance of the PZT microcantilevers. The micromachined PZT microcantilevers having a structure of SiN_x/Ta/Pt/PZT/Pt were fabricated through MEMS processes. In order to improve the mass sensitivity and the passivation, SiC thin films of the high elasticity material were deposited on the cantilever using plasma enhanced chemical vapor deposition (PECVD) at the temperature of 400°C. Plane-strain modulus of SiC thin film was measured by nanoindentation. We observed that SiC thin films showed higher Young's modulus than Si and SiO₂. Before and after the deposition of SiC thin films, the end-tip deflection and the resonant frequency change of microcantilevers were measured by a confocal microscope and an impedance analyzer. It was confirmed that end-tip deflection of microcantilever was reduced by 13～18% through the deposition of SiC thin films, indicating the stress relaxation of the microcantilevers.     

Physicochemical properties of mung bean starches in different Korean varieties and their gel textures

To compare the mung bean starches (MBS) and starch gel properties, Korean varieties, ‘Geumsung‘, ‘Dahyeon‘, ‘Sohyeon’ and ‘Eohul‘, were purified using water and alkaline steeping methods. The physicochemical properties of starches, the texture and structure of starch gels were investigated. The apparent amylose and protein contents were significantly different depending on varieties and steeping mediums. Water binding capacities were higher in ‘Geunsung’ and ‘Eohul‘. The granule sizes were ranged 7.8–23.3 μm and the shapes were oval and jelly bean, and ‘Dahyeon’ granule had a distinct hilum. The trough, final, and setback viscosities were significantly different and the viscosities of ‘Sohyeon’ showed lowest values. MBS gels formed a regular shaped 3-dimensional network. The gel structure of ‘Sohyeon’ changed irregularly during storage, but the structures of ‘Geumsung‘, ‘Dahyeon‘, and ‘Eohul’ retained regular shaped networks with decreasing inner cells. Resilience of MBS gels was higher in ‘Dahyeon’ and ‘Eohul’ than in ‘Geumsung’ and ‘Sohyeon‘.     

Changes in Flavor Components of Garlic Resulting from Gamma Irradiation

Formation of diallyl disulfide, identified as a main flavor component of garlic, was gradually decreased by irradiation of 0.05-0.5 kGy, but increased slightly at higher doses of 1.0-3.0 kGy. In garlic stored for 5 months, a dose of 0.1 kGy had little influence on the amount of diallyl disulfide, but higher dose irradiation caused an apparent reduction in the amount of the component.     

A case study of customer satisfaction for information technology solutions

There are numerous information technology solutions including hardware and software. A company that provides the solution should have knowledge of the customer needs in the purpose of sailing strategy or upgrade policy. The needs are also directly connected to the user satisfaction. However, the users have respective points of view in the needs as well as they may not identify the requirements to improve the solution. SERVQUAL can be an appropriate method to define and measure the customer satisfaction for the information technology solutions. As a case study of the customer satisfaction, the modified SERVQUAL items and scoring method are applied to a cyber-infrastructure system named CyberL ab in Korea. The measurement results of user satisfaction for CyberL ab are provided to confirm that our proposed method performs as we intended. From the results, we can score the satisfaction level of users and identify their needs in the various aspects. The total user satisfaction level for CyberL ab is scored by 88.3.     

Dielectric and field-induced strain behaviour of (Pb1−xBax) ZrO3 ceramics

The effects of Ba2+ substitution on the dielectric properties and induced strain behaviour of the (Pb1–xBax) ZrO3 ceramics (0.05x0.3) have been investigated as a function of x. A new phase diagram of the (Pb1–xBax) ZrO3 system, indicating the field effect on the phase transition, is also presented. As the Ba2+ content increases, the Curie temperature decreases linearly, whereas maximum dielectric constant increases for up to 20 mol% Ba2+ addition, and then decreases with further Ba2+ addition. Based on the hysteresis loops, the temperature range of the ferroelectric phase as an intermediate phase between the antiferroelectric and paraelectric phases, increases with increasing electric field and Ba2+ content. The ferroelectric loops are induced at room temperature for the specimens containing above 10 mol% Ba2+ by applying an electric field up to 25 kV cm–1. However, for the 5 mol% Ba2+-substituted specimen, no ferroelectric loop is induced, even with applied fields up to 55 kV cm–1. The phase transition due to electric field and Ba2+ addition is also confirmed by the measurement of the field-induced longitudinal strain.     

Mechanical characteristics of fused cast basalt tube encased in steel pipe for protecting steel surface

Because of the various excellent characteristics of cast basalt materials, such as, anti-corrosion, anti-wearing, good hardness, high chemical stability, of which steel may not possess, the steel-basalt composite pipes are used in severe environments for compensating the defects of steel. The limit of bending moment with which steel-basalt composite pipe may safely endure was calculated and the limit curvature of the composite pipe in the safe range was presented. The application temperature of steel-basalt pipe was examined due to a different coefficient among basalt, mortar and mild steel.     

ANALYSIS of BUTTERFAT EXTRACTION and FRACTIONATION USING SUPERCRITICAL CARBON DIOXIDE

A flow through extraction reactor was used to study supercritical fraction-ation of butterfat. the rate of extraction of butterfat was constant for an initial period followed by a decreasing rate of extraction. DSC and GC analyses showed that more soluble triglycerides extracted preferentially in the initial stages exhibited lower melting behavior. the chemical and physical properties of the fractions changed with extraction time. Residual butterfat concentration in the bed was obtained as a function of distance from the bed entrance. the breakthrough curves had a sigmoidal shape, with the ascent-portion of the curves advancing through the bed with the degree of extraction. At the highest extents of extraction, the lower acyl carbon number triglycerides were totally depleted from the lowest portions of the bed, where fresh CO₂ was introduced.     

Effect of Grain Growth on Pore Coalescence During the Liquid-Phase Sintering of MgO-CaMgSiO4 Systems

During the liquid-phase sintering of MgO-CaMgSiO₄ systems in N₂ atmosphere, the total porosity and the average pore size increase while the number of pores decreases. The negligible permeability of entrapped nitrogen through the liquid matrix and the observed linear relationship between the number of pores and that of the MgO grains suggest that the pores coalesce as a consequence of grain growth during sintering. An analysis of the balance between the pressure of the entrapped N₂ gas and the capillary pressure shows that pore coalescence in turn causes the observed porosity increase. When Fe₂O₃ or Cr₂O₃ is added to MgO-CaMgSiO₄, the pore size and the total porosity become larger or smaller, because the grain growth is accelerated or retarded, respectively.     

Heat and mass transfer characteristics of a helical absorber using LiBr and LiBr + LiI + LiNO3 + LiCl solutions

An experimental study has been performed to investigate the heat and mass transfer performance in a falling film absorber of a small-sized absorption chiller/heater. The components of the chiller/heater were concentrically arranged in a cylindrical form with a low temperature generator, an absorber and an evaporator from the center. The arrangement of such a helical-type heat exchanger makes the system more compact compared to a conventional one. As a working fluid, LiBr + LiI + LiNO₃ + LiCl solution is used to get improved heat transfer effect. The heat and mass transfer coefficients of the helical absorber provide similar values compared with the data obtained for horizontal absorbers at similar solution flow rates. The heat and mass transfer coefficients of LiBr + LiI + LiNO₃ + LiCl solution increase as the solution flow rate per unit length increases. However, if the solution flow rate is larger than 0.03 kg/m s, the heat and mass transfer increase is minimal. Thus, 0.03 kg/m s is recommended as an optimal solution flow rate. The heat and mass flux performance of LiBr + LiI + LiNO₃ + LiCl solution shows the tendency of 2-5% increase compared with that of LiBr solution.