• The Journal of Korean Academy of Prosthodontics
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• v.38 no.1
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• pp.1-11
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• 2000

Relining and rebasing are essential for long-term success and oral health in removable prosthodontics. Major features of failures between metal base and relining resins are adhesive failure due to lack of chemical bonding. The purpose of this study was to find a better metal primer and metal surface treatment method that enhance the bonding strength with relining resin materials. The surfaces of ticonium alloys were treated with $25{\mu}m$ sandblasting (Group A), stone wheel(Group B), stone wheel and EZ oxisor(Group C), $75{\mu}m$ sandblasting(Group D) and EZ oxisor application after $75{\mu}m$ sandblasting(Group E). They were subdivided into no primer application (Group I), MR bond application(Group II) and Metafast bonding liner (Group III). Then specimens were completed though being bonded with relining resins. The specimens were stored in $38^{\circ}C$ water for 48 hours and tensile strength was measured using the universal testing machine. The results were as follows, 1. Primer application groups showed higher bond strength than no primer application group(p<0.05). 2. In comparison with primer application groups, MR bond group showed higher bond strength than Meta fast bonding liner application group(p<0.05). 3. In comparison with surface treatment methods, Bond strengths of group A and B were significantly different with group C, D, and E, and group C were significantly different with group D, and E in no primer application group()(0.05). In primer application groups, group A, B, C were significantly different with group D and E(p<0.05). According to results of this study, Metal primer application and metal surface roughening were considered to be advantageous for relining of metal base dentures.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.114-125
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• 1993

In the present study the newly developed CAD/CAM system is applied to the process of the molding design, machining for mini-sized and precise processive die, and the production of press-stamped parts. When the design of a die was completed by means of CAD, wire cut NC data were generated with the aid of a design drawing in the CAD system and then inputed into the wire cut machine, and with the aid of a hole chart which had been made for this purpose, all the data were classified into the categories of CNC milling, jig boring, jig grinding, and machine center, and then developing a program of generating NC data, errors in process were reduced and programming time was shortened. The program was developed by using Autolisp language which was built-in the CAD, and realizing the intergation of designing a die, generating and processing NC data directly by a designer, designing time and machinery processing time were shorted. And the traditionally required working time for design. NC program required 6 days of work becomes 4 days of work by using the developed CAD/CAM system so that the efficiency shows 150% of the reduction working time. The prpgram of the design of the automation a progressive die mold was developed in the PC-Class Autocad system, therefore development expense could be reduced, and the integration of the CAD/CAM of the progressive die mold with the standard DB being built could be realized.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.675-696
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• 2023

Terpenoids, also referred to as terpenes, are a large family of naturally occurring chemical compounds present in the essential oils extracted from medicinal plants. In this study, a nondestructive methodology was created by combining ATR-FT-IR (attenuated total reflectance-Fourier transform infrared), and Raman spectroscopy for the terpenoids assessment in medicinal plants essential oils from ten different geographical locations. Partial least squares regression (PLSR) and support vector regression (SVR) were used as machine learning methodologies. However, a deep learning based model called as one-dimensional convolutional neural network (1D CNN) were also developed for models comparison. With a correlation coefficient (R²) of 0.999 and a lowest RMSEP (root mean squared error of prediction) of 0.006% for the prediction datasets, the SVR model created for FT-IR spectral data outperformed both the PLSR and 1 D CNN models. On the other hand, for the classification of essential oils derived from plants collected from various geographical regions, the created SVM (support vector machine) classification model for Raman spectroscopic data obtained an overall classification accuracy of 0.997% which was superior than the FT-IR (0.986%) data. Based on the results we propose that FT-IR spectroscopy, when coupled with the SVR model, has a significant potential for the non-destructive identification of terpenoids in essential oils compared with destructive chemical analysis methods.

• Korean Journal of Weed Science
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• v.14 no.4
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• pp.258-264
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• 1994

The weed survey in lowland rice field in 1992 was conducted to identify weed population change as affected by different elevation, soil type and cultivation pattern at Gangweon province. There were more perennial weeds in plain and east coastal area while more annual weeds in mid alpine and alpine area. Meanwhile, perennial weed species was more dominant at ordinary and sandy soil but annual weed species was more dominant at poorly drained soil. In general, hand and machine(30 day old seedling) transplanting would result in higher dominant weed species of perennial while there was more annual weed species in machine (10 day old seedling) transplanting and dry seeding, respectively. Also, annual weed species was more predominant at spring plowing time compared to autumn plowing time. Particularly, there was change in dominant weed species with time. In 1971 annual weed species was more predominant but perennial weed species was highly dominant in 1981 and 1992.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.221-225
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• 2009

A solar thermal collector is a solar collector specifically intended to collect heat: that is, to absorb sunlight to provide heat. A flat plate is the most common type of solar thermal collector, and is usually used as a solar hot water panel to generate solar hot water. A flat plate collector consists basically of an insulated metal box with a glass or a plastic cover and a dark-colored copper absorber plate. Solar radiation is absorbed by the copper absorber plate and transferred to water that circulates through the collector in copper tubes. Ultrasonic welding is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to work pieces being held together under pressure to create a solid-state weld. In this study, we developed solar collector ultrasonic welding machine with digital controlled power supply and tested various welding conditions such as welding pressure, welding amplitude, welding speed. Welding speed was considered in 2~12m/min. The width of ultrasonic welds was increased with welding amplitude by 2.2~2.5mm. The fracture load of ultrasonic welds showed 20% higher than domestic products.

• Advances in concrete construction
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• v.16 no.6
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• pp.317-325
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• 2023

Strength prediction and correlation of concrete is done using experimental and analytical methods. Main objective is to correlate the experimental and simulated values of compressive strength of concrete mix using Fly Ash (FA) and Silica Fume (SF) by partial replacement of cement in concrete. Mix proportion was determined using IS method for M40grade concrete. Hundred and forty-seven cubes were cast and tested using Universal Testing Machine (UTM). Genetic Algorithm (GA) model was developed using C++ program to simulate the compressive strength of concrete for various proportions of FA and SF replacements individually at 3% increments. Experiments reveal that 12 percent silica fume replacement produced maximum compressive strength of 35.5 N/mm², 44.5 N/mm² and 54.8 N/mm² moreover 9 percent fly ash replacement produced a maximum strength of 31.9 N/mm², 37.6 N/mm² and 51.8 N/mm² during individual material replacement of concrete mix. Correlation coefficient for each curing period of fly ash and silica fume replaced mix were acquired using trend lines. The correlation coefficient is found to be approximately 0.9 in FA and SF replaced mix irrespective of the mix proportion and age of concrete. A higher and positive correlation was found between the experimental and simulated values irrespective of the curing period in all the replacements.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.4
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• pp.195-201
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• 2002

We propose a new scheme of high-resolution heterodyne interferometer that employs the two-axial mode He-Ne laser with an inter-mode beat frequency of 600~1000 MHz. An electronic RF-heterodyne circuit lowers the beat frequency down to 5 MHz, so that the phase change of the interferometer output is precisely measured with a displacement resolution of 0.1 nanometer without significant loss of dynamic bandwidth. A thermal control scheme is adopted to stabilize the cavity length with ainus to suppress frequency drifts caused by the phenomena of frequency pulling and polarization anisotropy of the two-axial made laser to a stability level of 2 parts in $10^9$. The two-axial mode HeNe laser yields a high output power of 2.0 mW, which allows us to perform multiple measurements of up to 10 machine axes simultaneously.

• Membrane and Water Treatment
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• v.15 no.4
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• pp.163-176
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• 2024

Asymmetric flat sheet poly(vinylidene fluoride) (PVDF) membranes were fabricated using the phase inversion technique, employing four distinct solvents with varying solubility power: N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), Dimethyl sulfoxide (DMSO), and N-Methyl-2-pyrrolidone (NMP). The influence of these solvents on the crystalline properties of the polymers was investigated using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) to elucidate their role in PVDF polymorphism during membrane formation. Our findings revealed significant variations in membrane crystalline phase due to the dissolution of PVDF in different solvents, with α-polymerization predominant in membranes cast with NMP and DMSO, while DMF and DMAc solvents favored β-type polymerization. Further, various additives including PEG-400, TiO2, LiCl, LiBr, acetone, ethanol, propanol, and water were employed to evaluate their impact on membrane morphology and properties. Scanning electron microscopy (SEM) and Ultimate testing machine (UTM) were utilized to analyze membrane morphology, while the tensile strength, contact angle, pore size, and porosity were estimated using the sessile drop method, imageJ, and gravimetric method, respectively. Our results demonstrated that all additives exerted influence on membrane morphology and properties depending on their characteristics and interactions with solvents and polymers. Notably, acetone, being volatile, facilitated the formation of a thin PVDF layer on the membrane surface, resulting in a reduced average pore size (0.18㎛). Conversely, LiCl and LiBr acted as pore-forming additives, yielding membranes with distinct pore characteristics and porosity. Moreover, water as a non-solvent additive induced pregelation during the nonsolvent-induced phase separation (NIPS) process, thereby promoting pore formation (53% porosity) and enhancing membrane hydrophobicity (104° contact angle). To evaluate the quality of synthesized membranes, permeate flux ranging from 16.2 L/m².hr to 27.9 L/m².hr with a salt rejection rate of 98 %, was evaluated using Vacuum Membrane Distillation (VMD).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.119-125
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• 1999

At Wire Rod Mill Plant, wire is made of the billet produced at continuous casting machine, or rolled bloom produced at billeting mill, and the product can be classified of wire of 5.5${\Phi}$ and bar in coil of 14∼42${\Phi}$ in diameter(bar in coil will be referred to as coil as below). At present, wire is produced at POSCO No.1, 2, 3 WRM, coil at garret line of No. 2 WRM. Head and tail of coil are properly cut and treated to scrap to fulfill the customer's satisfaction. This above cutting is done off line, and small size coil can be cut manually with clipper, large size coil with hydraulic cutter. Nowadays, it is being investigated to cut automatically in line with trimming shear after passing mill stand. At the moment, Because the coil produced at the garret line of No.2 WRM is hot 400∼600$^{\circ}C$ and trimming is done manually with cutter, there are always interference from manual operation or safety problem of bad working condition. Not only because of the diversity of the coil size 14∼42${\Phi}$ in diameter, but because of the rolling speed 2.5∼22m/sec, it is required to be equipped with several trimming shear. But this can be accomplished with only one shear installed proper place at this paper.

• Advances in materials Research
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• v.2 no.4
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• pp.181-193
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• 2013

Description and theory of spin coating technique has been elaborately outlined and a spin coating machine designed and fabricated using affordable components. The system was easily built with interdisciplinary knowledge of mechanics, fluid mechanics and electronics. This equipment employs majorly three basic components and two circuit units in its operation. These include a high speed dc motor, a proximity sensor mounted at a distance of about 15 mm from a reflective metal attached to the spindle of the motor to detect every passage of the reflective metal at its front and generate pulses. The pulses are transmitted to a micro-controller which process them into rotational speed (revolution per minute) and displays it on a lead crystal display (LCD) which is also a component of the micro-controller. The circuit units are a dc power supply unit and a PWM motor speed controlling unit. The various components and circuit units of this equipment are housed in a metal casing made of an 18 gauge black metal sheet designed with a total area of 1, $529.2cm^2$. To illustrate the use of the spin-coating system, ZnO sol-gel films were prepared and characterized using SEM, XRD, UV-vis, FT-IR and RBS and the result agrees well with that obtained from standard equipment and a speed of up to 9000 RPM has been achieved.