• Polymer(Korea)
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• v.38 no.3
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• pp.286-292
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• 2014

The rheology of highly concentrated polymer bonded explosive (PBX) simulant was studied. An energy material, polyethylene plastomer (Exact$^{TM}$) having similar properties to poly(BAMO-AMMO) was selected as a binder. Dechlorane with similar properties to RDX (Research Department eXplosive) was chosen as a filler. Mixing behavior in a batch melt mixer was investigated. During mixing a large amount of heat of viscous dissipation was generated and a continuous decrease in torque was observed when the filler content was above 70 v%. It was believed due to wall slip phenomena. From the SEM images, the fillers were well dispersed and the effect of mixing condition affected slightly on the dispersion. Owing to distinct shear thinning behavior of the suspensions, measuring viscosity of highly filled suspensions was possible in a high shear rate capillary rheometer though it was impossible even in a low shear rate plateplate rheometer.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.365-368
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• 2008

This research is related to 240MPa ultra-high strength concrete(UHSC) with extremely loss W/B ratio. For this development, High flow cement is mainly used which has a short reaction rate due to the high blaine and high early strength, which can make greater fluidity in case of very low W/C ratio. It made the best mixture using the mineral admixtures silica fume, slag powder and special admixture. For dispersibility and homogeneity of cement binder, cement of premix type is produced using omni-mixer. Moreover, it ensures the fluidity of ultra-high strength concrete(UHSC). For having a good fire performance, we made an experiment special coarse aggregate. As a result, we got 180MPa in case of water curing, 200MPa in case of steam curing and uniform UHSC of 240MPa in case of a special curing method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.551-561
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• 2001

In this paper, the large signal unified model is established for H4O GaAs pHEMT of GEC-Marconi using modified Curtice model. This unified model includes DC characteristic, small signal, and noise characteristic as various bias. Particularly, the model can simply and physically explain trans-conductance $(g_m)$ of pHEMT using modified Curtice model, and can tell the difference $g_m$, $R_ds$ at DC and these at AC through inclusion of internal RF-choke. The results of the established model built up using SDD in HP-Eessof show good agreement to the S/W measured data in DC, small signal, and noise characteristic. This model can also be applied to various computer aided analysis, such as linear simulation, 1-tone harmonic balance simulation, and multi-tone harmonic balance simulation, so the LNA(Low Noise Amplifier), oscillator, and mixer design has been shown using this model library.

• Journal of electromagnetic engineering and science
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• v.14 no.2
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• pp.61-67
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• 2014

This paper presents a zero-IF CMOS RF receiver, which supports three channel bandwidths of 5/10/40MHz for LTE-Advanced systems. The receiver operates at IMT-band of 2,500 to 2,690MHz. The simulated noise figure of the overall receiver is 1.6 dB at 7MHz (7.5 dB at 7.5 kHz). The receiver is composed of two parts: an RF front-end and a baseband circuit. In the RF front-end, a RF input signal is amplified by a low noise amplifier and $G_m$ with configurable gain steps (41/35/29/23 dB) with optimized noise and linearity performances for a wide dynamic range. The proposed baseband circuit provides a -1 dB cutoff frequency of up to 40MHz using a proposed wideband OP-amp, which has a phase margin of $77^{\circ}$ and an unit-gain bandwidth of 2.04 GHz. The proposed zero-IF CMOS RF receiver has been implemented in $0.13-{\mu}m$ CMOS technology and consumes 116 (for high gain mode)/106 (for low gain mode) mA from a 1.2 V supply voltage. The measurement of a fabricated chip for a 10-MHz 3G LTE input signal with 16-QAM shows more than 8.3 dB of minimum signal-to-noise ratio, while receiving the input channel power from -88 to -12 dBm.

• Journal of Oral Medicine and Pain
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• v.18 no.1
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• pp.73-82
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• 1993

To investigate the changes in aerobic and facultative anaerobic oral microflora during remission-induction chemotherapy in patients with acute myeloid leukemia, 10 consecutive patients were studied during a period of 28 days. One day before, during and after the induction therapy, patients were given 10% Betadine solution for mouthrinses after breakfast and kept from eating and drinking. After 3 hours, paraffin-stimulated whole saliva was obtained for 2 minutes and transported to the laboratory. The samples were dispersed and homogenized by use of vortex mixer for 20 seconds. From these samples 10-fold serial dilutions (from 10-1 through 10-3) were prepared. Each dilution of 0.1 ml was plated on duplicate set of one nonselective medium (Blood agar) and four selective media (Sabourauds dextrose agar, Mannitol salt agar, Mac-Conkey agar, SF medium ) using applicator woods. All agar plate were incubated at 37$^{\circ}C$ for 48 hours. The total number of microorganisms was calculated and the percentage distribution of the various microorganisms from each specimen was drawn. 1. The salivary flow rate decreased by 66%, going from 5.38 ml/2min to 1.81 ml/2min over two days during the chemotherapy. 2. The total number of microorganisms in saliva increased by 22%, going from 4.88$\times$105/ml to 6.00$\times$105/ml over two days during the chemotherapy. 3. The salivary flow rate and the total number of microorganisms in saliva were recovered within 28 days after the chemotherapy. 4. The quantitative alteration in oral Enterobacteria, Enterococci, Staphylococci, Cndida during the chemotherapy had no statistical significance. 5. In saliva of the patients with acute myeloid leukemia who ahd intraoral ulcer, Enterobacteria was quantitatively predominent. Our study suggests that chemotherapy-induced transient xerostomia may induce acute oral infection. Consequently, the use of saliva substitute, the removal of intraoral infection source and the consistent oral hygiene care seem to be required to avoid the transmission of potential pathogenes in this group of patients.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.3
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• pp.310-320
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• 2007

Statement of the problem. The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. But problems such as poor workability, rough surface, poor adhesion of glass fiber resin complex are not solved yet. Purpose. The aim of the present study was to investigate the effect of short glass fibers on the transverse strength of heat-polymerized denture base acrylic resin and roughness of resin complex after abrasion test. Material and methods. To avoid fiber bunching and achieve even fiber distribution, glass fiber bundles were mixed with acrylic resin powder in conventional mixer with a non-cutting blade, to produce the glass fiber($10{\mu}m$ diameter, 3mm length, silane treated) resin composite. Glass fibers were incorporated at 0%, 3%, 6% and 9% by weight. Transverse strength were measured. After abrasion test, surface roughness was evaluated and scanning electron microscope view was taken for clinical application. Results. 1. 6% and 9% incorporation of 3mm glass fibers in the acrylic resin enhanced the transverse strength of the test specimens(p<0.05). 2. Before abrasion test, incorporation of 0%, 3%, 9% glass fiber in the resin showed no dirrerence in roughness statisticaly(p>0.05). 3. After abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically(p>0.05). 4. In SEM, surface roughness increased as the percentage of the fibers increased. 5. In the areas where glass fiber bunchings are formated, a remarkably high roughness was noticed. Conclusion. 6% and 9% addition of silane-treated short glass fibers into denture base acrylic resin increased transverse strength significantly. Before and after abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.3
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• pp.346-351
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• 2009

This study was carried out to determine the rheological properties of bread doughs containing flour-ferments prepared with seed mash obtained by Koji incubation, yeast, and lactic acid bacteria, using farinograph, extensograph, amylograph, and large scale-dough mixer. According to farinograph, the addition of the flour-ferments did not influence the water-absorption rate of doughs, regardless of the kinds of flour-ferments, however, it increased development time and decreased stability of doughs. According to extensograph, both dough resistance and resistance-to-extensibility ratio increased with the addition of flour-ferments. Especially the dough containing the flour-ferments prepared with seed mash, S. cerervisiae, and L. brevis showed the highest resistance-to-extensibility ratio. According to amylograph, although the doughs containing the flour-ferments did not show the differences in gelatinization temperature and temperature at maximum viscosity with the control which does not contain the flour-ferments, they showed lower maximum viscosity than the control. They also showed lower development value and faster development time.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.8
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• pp.365-370
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• 2005

Microwave diagnostics have been widely utilized to measure the important parameters of high temperature and high density plasmas. Reflectometry is known as a promising microwave diagnostic which has a number of merits to measure electron density profiles. In the KSTAR device, X-mode FM reflectometry is planned to measure the plasma density profiles. FM reflectometry is required to extract phase information on raw mixer IF signals, thereby obtaining time-of-flight of reflectometry signals. It is known that the data analysis method is crucial to determine the performance of FM reflectometry In fact, there are several analysis programs which have been utilized in various FM systems. Since each program was developed for a specific device, however, it is difficult to directly apply it to a different reactor like the KSTAR device. It is necessary, therefore, to develop a data analysis program for the KSTAR FM reflectometry. In this paper, complex digital demodulation (CDM) and wavelet transformation are examined in terms of the performance of density profile reconstruction. For the comparison of both methods, FM reflectometry signals are generated on the basis of assumed profiles and the interaction of the X-mode wave and the plasma. In order to see how well both methods work under various conditions, three types of profiles are assumed and noise effects are included. As a result, both methods work well under the condition of gentle density gradient and small noise level. As density gradient becomes steeper and noise level gets higher. the reconstruction performance of wavelet is better than that of CDM.

• Elastomers and Composites
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• v.48 no.1
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• pp.18-23
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• 2013

Nylon 12 elastomer was slightly crosslinked in molten state by the addition of small amount of dicumyl peroxide (DCP) as a crosslink agent and triallycyanuate (TAC) as a co-agent during melt compounding at $160^{\circ}C$ in an internal mixer. The effect of the peroxide crosslinking on mechanical, dynamic mechanical and rheological properties of the nylon 12 elastomer was investigated by means of tensile testing, dynamic mechanical analysis (DMA) and small amplitude oscillating rheometer, respectively. With modification, there is an improvement in tensile modulus and Young's modulus with decease in elongation at break. DMA results for peroxide modified nylon 12 elastomers demonstrated that the glass transiaiton temperature of PTMG segment shifted to higher temperature and the storage modulus remained constant above the melting temperature of nylon 12 segments. Melt rheological studies revealed that the peroxide modified nylon 12 elastomer exhibited a more solid like behavior and stronger shear thinning behavior compared to neat nylon 12 elastomer, which was more prominent at higher TAC content in the polymer matrix. The peroxide modified nylon 12 elastomer exhibited good elastic recoverability and improved mechanical properties without sacrificing melt processibilty, and especially the service temperature range increased as compared to neat nylon 12 elastomer.

• Archives of Pharmacal Research
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• v.28 no.4
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• pp.493-501
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• 2005

Effect of solvents on physical characteristics and release characteristics of monolithic acetaminophen (APAP) hydroxypropylmethylcellulose (HPMC) matrix granules and tablets were examined. Various types and amounts of solvents were employed for granulation and coating. APAP and other excipients were mixed and were then wet-granulated in a high-speed mixer. The dried granules were then directly compressed and film-coated with low viscosity grade HPMC. As the amount of water increased, the size of granules also increased, showing more spherical and regular shape. However, manufacturing problems such as capping and lamination in tableting occurred when water was used alone as a granulating solvent. The physical properties of HPMC matrix granules were not affected by the batch size. The initial release rate as well as the amount of APAP dissolved had a tendency to decrease as the water level increased. Addition of nonaqueous solvent like ethanol to water resulted in good physical properties of granules. When compared to water/ethanol as a coating solvent, the release rate of film-coated HPMC matrix tablets was more sensitive to the conditions of coating and drying in methylene chloride/ethanol. Most of all, monolithic HPMC matrix tablet when granulated in ethanol/water showed dual release with about $50\%$ drug release immediately within few minutes followed by extended release. It was evident that the type and amount of solvents (mainly water and ethanol) were very important for wet granulation and film-coating of monolithic HPMC matrix tablet, because the plastic deforming and fragmenting properties of material were changed by the different strengths of the different solvents.