• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.841-848
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• 2008

DME(Di-methyl Ether) has been expected to be one of the promising alternative fuels for compression ignition engines due to its low emission characteristics for particulate matter. However, its physical properties such as density, bulk modulus and viscosity are not comparable to those of conventional diesel fuel. Especially, problems caused by low lubricity and high compressibility need to be understood more thoroughly, when a DME fuel is used for compression ignition engine, especially with mechanical fuel supply system. In this study, measurement and calculation of DME's bulk modulus were carried out over the range of temperatures from $-3^{\circ}C$ to $53^{\circ}C$, and pressures from 50 bar to 250 bar using an experimental apparatus built in this work. The results show that DME is prone to be compressed more easily compared to diesel fuel. A comparison of bulk modulus with butane and propane were also made in this work.

• Macromolecular Research
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• v.11 no.4
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• pp.267-272
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• 2003

The isothermal cure reactions of blends of epoxy (DGEBA, diglycidyl ether of bisphenol A)/anhydride resin with polyamide copolymer (poly(dimmer acid-co-alkyl polyamine)) or PEI were studied using differential scanning calorimetry (DSC). Rheological measurements have been made to investigate the viscosity and mechanical relaxation behavior of the blends. The reaction rate and the final cure conversion were decreased with increasing the amount of thermoplastics in the blends. Lower values of final cure conversions in the epoxy/thermoplastic blends indicate that thermoplastics hinder the cure reaction between the epoxy and the curing agent. Complete miscibility was observed in the uncured blends of epoxy/thermoplastics up to $120^{\circ}C$ but phase separations occurred in the early stages of the curing process at higher temperatures than $120^{\circ}C$. According to the rheological measurement results, a rise of G' and G" at the onset of phase separation is seen. A rise of G' and G" is not observed for neat epoxy system since no phase separation is seen during cure reaction. At the onset of phase separation the rheological behavior was influenced by the amount of thermoplastics in the epoxy/thermoplastic blends, and the onset of phase separation can be detected by rheological measurements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.231-234
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• 2004

Chemical mechanical polishing(CMP) process was studied in terms of tribology in this paper. CMP performed by the down force and the relative motion of pad and wafer with the slurry is typically tribological system composed of friction, wear and lubrication. The piezoelectric quartz sensor for friction force measurement was installed and the friction force was detected during CMP process. Various coefficient of friction was attained and analyzed with the kind of pad, abrasive and the abrasive concentration. The lubrication regime is also classified with ${\eta}v/p(\eta,\;v\;and\;p;$ the viscosity, relative velocity and pressure). Especially, the co-relation not only between the friction force and the removal per unit distance but also between the coefficient of friction and within-wafer-nonuniformity was estimated.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.5
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• pp.62-66
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• 2010

Cellulosic materials were dissolved by NMMO(N-methylmorpholine-N-oxide) and CED (Cupriethylene diamine), respectively, to measure their DPs (degrees of polymerization) by using viscometer. We changed cellulose DPs by applying various amounts of low intensity electron-beam radiation to the cellulosic materials. NMMO is environmental-friendly, non-toxic, and biodegradable organic cellulose solvent and used industrially because of its high cellulose dissolving power and high solvent recovery ratio. The cellulose DP measurement results using these two different chemicals were correlated highly ($R^2$ >0.95). It was also found that cellulose with high DP was dissolved more easily in NMMO than CED. In addition, NMMO method gave more higher resolution in the measurement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.71-77
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• 2021

An impeller identification technique that is essential for adding viscosity measurement functions to overhead stirrers is presented in this study. Previous studies have revealed that using magnets facing the same poles arranged in a row can aid in distinguishing the types of impellers by detecting the number of magnets in a non-contact manner. However, as these previous studies measured the magnetic fields using analog Hall sensors, a converting circuit for the digital signals is required that can interface with the MCU. In this study, it was demonstrated that the number of magnets can be distinguished without using a separate conversion circuit by using a Hall sensor with a digital output. Owing to the unique hysteresis characteristics of digital Hall sensors, it was confirmed through experiments that the complex and diverse outputs appear depending on the direction of the magnetic field, the arrangement of magnetic poles, and the moving direction of the magnet. The measurement of the magnetic field showed that an edge signal equal to the number of magnets inserted into the impeller was detected when the radial direction was used, and the south pole was first approached.

• Tribology and Lubricants
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• v.20 no.5
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• pp.225-230
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• 2004

Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the tribological characteristics of a certain lubricant, it is also important to get the information of traction behaviors as well. In this work, we developed a device for measuring the friction force of ehl contact condition as well as the film thickness. To verify the validity of the measuring system, the friction forces and film thicknesses under ehl condition are simultaneously measured with the variations of additive ratios of viscosity index improvers which cause non-linear tendencies of film thickness to contact velocity.

• Journal of the Korean Ceramic Society
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• v.31 no.8
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• pp.823-828
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• 1994

Dispersion condition of Si3N4 powder in molten wax was established by comparing relative viscosity of mixture with 20 vol% solids loading, while the evaluation of compression-molded sample was demonstrated as an effective method for developing a binder system for injection molding. The best dispersion of Si3N4 powder in molten wax was achieved when Si3N4 powder was treated with 5% stearic acid, and the critical powder volume fraction was determined to be about 0.51 from density measurement of compression-molded samples. Samples containing polar secondary binder showed markedly improved green strength, higher thermal expansion and increased wicking rate in the early stage.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.88-89
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• 2003

A series of novel spinning acrylic polymer containing silk protein were synthesized by copolymerization of acrylonitrile (AN) and silk fibroin peptide (SFP) modified by acryloyl chloride (AC) with vinyl groups. The viscosity values of these copolymers showed that the copolymers have good spinnability, which are synthesized under the condition of putting a micro amount of metal ions into synthesizing solvent. The fiber based on the poly (AN-co-SFP) was prepared and characterized by SEM, FTIR measurement of its shell and core flakes, and moisture absorption. The fiber appeared a smooth surface and could be assumed to have excellent adhesive between SFP and PAN. Furthermore, these fibers showed a shell-core structure and excellent moisture absorption.

• Korea-Australia Rheology Journal
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• v.15 no.3
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• pp.109-115
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• 2003

Rheometry testing and the DSC measurement of five thermotropic liquid crystalline polymers (TLCP) have been carried out. The dynamic viscosities of the five TLCPs show a typical shear-thinning behaviour obeying the power-law with the power indices from 0.2 to 0.3. When these TLCPs are heated above the melting temperatures determined by the DSC measurements, the dynamic viscosities first rapidly decrease by 2～3 orders of magnitude then level off, finally increase gradually with the further increasing of temperature. The steady shearing exhibited the same behaviour as the dynamic shearing, but serious edge fracture of material slippage out of the plates occurred. The abnormal temperature dependence of the viscosities can be explained by the nematic-isotropic transition. By using the concept of activation energy, we propose a simple model which can fit the shear-thinning behaviour quite well and predict qualitatively correct temperature effects.

• Textile Coloration and Finishing
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• v.17 no.1
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• pp.52-59
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• 2005

The purpose of this study is to establish the scientific data of cotton fabric pretreated with skim milk powder and to improve the dyeability. The surface monophology, add on, whiteness, stiffness, air permeability, moisture regain and absorption of cotton fabrics were evaluated by varying concentration of SMP to get the optimal conditions in pretreatment. FT-IR of cotton fabrics pretreated with SMP were measured. Amino acid compositions, viscosity of SMP were evaluated. The K/S values by varying concentration of cinnamon cassia and subtract of dyed SMP-C were measured. I attempted to evalute the color fastness of untreated and AI. The results are as follow; The optimal concentration of SMP was 9%(w/v) to be pretreated with cotton fabrics. From FT-IR spectrum, formation of -NH$_2$ and -COOH was verified by SMP-C. Denaturalization of protein and condensation of carbohydrate, fat, etc. were found in a measurement of amino acid and viscocity. The K/S value of cotton fabrics pretreated with SMP was higher than that of untreated. Most of the color fastnesses were great.