• Advances in aircraft and spacecraft science
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• v.2 no.3
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• pp.303-328
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• 2015

A design methodology is presented to develop the hingeless control surfaces for MAV using adhesively bonded Macro Fiber Composite (MFC) actuators. These actuators have got the capability to deflect the trailing edge surfaces of the wing to attain the required maneuverability, besides achieving the set aerodynamic trim condition. A scheme involving design, analysis, fabrication and testing procedure has been adopted to realize the trailing edge morphing mechanism. The stiffness distribution of the composite MAV wing is tailored such that the induced deflection by piezoelectric actuation is approximately optimized. Through ground testing, the proposed concept has been demonstrated on a typical MAV structure. Electromechanical analysis is performed to evaluate the actuator performance and subsequently aeroelastic and 2D CFD analyses are carried out to see the functional requirements of wing trailing edge surfaces to behave as elevons. Efforts have been made to obtain the performance comparison of conventional control surfaces (elevons) with morphing wing trailing edge surfaces. A significant improvement in lift to drag ratio is noticed with morphed wing configuration in comparison to conventional wing. Further, it has been shown that the morphed wing trailing edge surfaces can be deployed as elevons for aerodynamic trim applications.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.7
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• pp.498-504
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• 2011

As the electronic industry rapidly develops, the heat flux from state-of-the-art electronics increases up to $10^6\;W/m^2$. For this reason, the development of a new cooling technology for high heat flux applications is strongly required. Recently, some cooling technologies using boiling and condensation of working fluid are being adopted to overcome such a technical barrier. In the present study, a smooth boiling surface ($14{\times}14\;mm^2$) was immersed in FC-72 and its vapor was condensed by four different types of condensation surfaces ($30{\times}30\;mm^2$ base). The condensing surfaces were composed of a smooth surface and $1{\times}1\;mm^2$ pin-finned surfaces of 2 mm height with 0.3, 0.5 and 1 mm array spacing. Boiling and condensing characteristics were investigated in detail on their combinations of boiling and condensing surfaces. For a smooth boiling surface the results obtained showed that the pin-finned condensing surface with 1 mm array spacing yielded the best performance and the smooth condensation surface did the worst. Furthermore hysteresis phenomena could be reduced by using enhanced condensing surfaces.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.725-733
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• 2010

A simulator is proposed in this paper for predicting the RF signal level after propagating over sea and land surfaces. Various sea and land types and transmit/receive antenna patterns, as well as the locus of the transmit antenna, are considered for this simulator. At first, microwave reflection characteristics of various sea surfaces have been computed, based on an empirical formula which is developed in this study for the relation between the sea surface roughness and wind speed. Then, microwave reflections from land surfaces such as forests, agricultural areas, and bare surfaces, are computed using the first-order vector radiative transfer theory. Finally, the signal paths over sea and land surfaces are found using the ray tracing technique and the digital elevation model, and the signal level received by a receiving antenna is computed by the using the reflection coefficients of sea and land surfaces and the signal paths.

• Computers and Concrete
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• v.29 no.4
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• pp.247-253
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• 2022

In this study, the problem of discontinuous contact in two functionally graded (FG) layers resting on a rigid plane and loaded by two rigid blocks is solved by the finite element method (FEM). Separate analyzes are made for the cases where the top surfaces of the problem layers are metal, the bottom surfaces are ceramic and the top surfaces are ceramic and the bottom surfaces are metal. For the problem, it is accepted that all surfaces are frictionless. A two-dimensional FEM analysis of the problem is made by using a special macro added to the ANSYS package program The solution of this study, which has no analytical solution in the literature, is given with FEM. Analyzes are made by loading different Q and P loads on the blocks. The normal stress (σy) distributions at the interfaces of FG layers and between the substrate and the rigid plane interface are obtained. In addition, the starting and ending points of the separations between these surfaces are determined. The normal stresses (σx, σy) and shear stresses (τxy) at the point of separation are obtained along the depth. The results obtained are shown in graphics and tables. With this method, effective results are obtained in a very short time. In addition, analytically complex and long problems can be solved with this method.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.161-167
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• 1993

This paper deals with a new method for the machining of a die cavity defined by sculptured surfaces. In machining die cavities or pockets, process planners have been faced with some troulbes. One of the troubles ius to rebove a great deal of material within a given boundary while avoiding cutter interference. Cutter interference is a ciritical problem in NC machining of a die cavity. Even though this cavity machining has been implemented in many CAM systems, most of them can handle limited shapes of cavities or pockets. In this paper, a procedure has been developed to machine die cavity or pocket of a sculptured surface. The offset surfaces of the part surfaces and boundary surfaces are determined to calculate the intersection curves. These intersection curves form a FACE on the part surface, and the interference free tool pathe is generated by eliminating the points outside the FACE when computing the cutter contact (CC) data. Additionally, the cutter location (CL) data obtained from the CC data convert to an NC data. The NC data generated through this algorithm are verified on the CINCINNATI milling machine. A propotype die cavity machining system has been implemented in FORTRAN language and FIGARO graphics library on IRIS workstation.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.2
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• pp.151-158
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• 2010

The purpose of this study was to investigate the tooth surface caries patterns in the primary dentition according to breast or bottle feeding. The subjects of study were 815 children, 36 to 71 months old, in Iksan, Cheongju and Ulsan cities. The caregivers of the children were asked which they fed between the breast milk and the infant formula during the 1st year after birth and the duration of feeding. There was no significant difference in dmfs between the breast milk group and the infant formula group(significance level 0.05, same below). Tooth groups, tooth surface groups, teeth, and tooth surfaces which had significantly higher dmfs in the breast milk group than in the infant formula group were upper anterior teeth(tooth groups), upper incisors' buccal and proximal surfaces(tooth surface groups), upper incisors and upper second molars(teeth), upper central incisors' buccal and distal surfaces, upper lateral incisors' buccolingual and proximal surfaces, upper 2nd molars'lingual, proximal, and occlusal surfaces, and lower 2nd molars' buccal and distal surfaces. In the breast milk group, tooth groups, tooth surface groups, teeth, and tooth surfaces which dmfs significantly increased as the duration of the feeding increased were upper anterior teeth and upper molars(tooth groups), upper anterior teeth's proximal surfaces, upper molars' buccolingual, proximal, and occlusal surfaces, lower molars' proximal surfaces(tooth surface groups), upper anterior teeth, upper molars, lower 2nd molars(teeth), upper anterior teeth's proximal surfaces, upper 1st molars'buccolingual, proximal, and occlusal surfaces, upper 2nd molars' buccal surfaces, and lower 2nd molars'mesial surfaces(tooth surfaces). In the infant formula group, dmfs increased after 3 years of feeding, but the difference was not significant. Caries prevention is necessary in case of breastfeeding more than two years.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.271-275
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• 1998

Controversial observations on the effect of pre-attached bacteria on the attachment of diatoms to artificial surfaces immersed in seawater have been made. Furthermore, it is not known whether or not pre-attached bacteria on artificial surfaces influence attachment of diatoms in natural seawater. In this study, we used various surfaces to which marine bacteria were pre-attached for different incubation periods. In the first experiment, glass slides were initially attached by marine natural bacteria with different exposure time (0-133 hr) and then immersed into seawater for a certain time period. The attachment of diatoms was not affected by the abundance of pre-attached bacteria (p > 0.05). The maximum abundance of attached diatoms was found on control surfaces, and the minimum abundance on surfaces where attached bacterial abundance was highest. In the second experiment, glass slides and acryl slides, either attached by marine natural bacteria for 6 days or coated by agar, were immersed in seawater. Untreated slides were also employed. On the surfaces of acryl slides with the most abundant attached bacteria ($5.4{\pm}0.02{\times}10^5\;cells\;cm^{-2}$), abundances of attached diatoms were less than those on untreated slides. On the surfaces of glass slides with bacterial abundance of $2.5{\pm}1.0{\times}10^5\;cells\;cm^{-2}$, however, abundances of attached diatoms were not different from those of untreated slides. On the agar-coated slides, the immigration rate and immigration coefficient were on average > 2 folds compared to other surfaces, indicating high rates of diatom attachment on mucilage simulated surfaces. Therefore, it seems that pre-attachment of bacteria is not prerequisite for the attachment of diatoms on artificial surfaces.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2001-2011
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• 1993

This study deals with the machining of sculptured surfaces on 5-axis CNC milling machine with end mill cutter. The study (I) has the following contents. In 5-axis CNC milling, CL-data consist of CC-data and cutter axis direction vector at the CC-point. Thus, in machining of the sculptured surface on 5-axis CNC milling machine, determination of the direction vector of the milling cutter is very important. The direction vector is obtained by the fact that bottom plane of the milling cutter must not interfere with the free-form surface being machined. The interference is checked by the z-map method which can be applied in all geometric types of the sculptured surfaces. After generating NC part programs from 5-axis post-processing algorithms, sculptured surfaces were machined with 5-axis CNC milling machine (CINCINNATI MILACRON, 20V-80). From these machining tests, it was shown that the machining of the free-form surfaces on 5-axis CNC milling machine with the end mill has smaller cusp heights and shorter cutting time than on 3-axis CNC milling machine with the ball-end mill. Thus, 5-axis CNC end milling was effective machining method for sculptured surfaces. The study (II) deals with the prediction of cusp height and the determination of tool path interval for the 5-axis machining of sculptured surfaces on the basis of study(I).

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.133-138
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• 2013

Acrylonitrile-butadiene-styrene (ABS) plastic is a polymer material extensively used in electrical and electronic applications. Nickel (Ni) thin film was deposited on ABS by electroless plating, after its surface was treated and modified with atmospheric plasma generated by means of dielectric barrier discharges (DBDs) in air. The method in this study was developed as a pre-treatment for electroless plating using DBDs, and is a dry process featuring fewer processing steps and more environmentally friendliness than the chemical method. After ABS surfaces were modified, surface morphologies were observed using a scanning electron microscope (SEM) to check for any physical changes of the surfaces. Cross-sectional SEM images were taken to observe the binding characteristics between metallic films and ABS after metal plating. According to the SEM images, the depths of ABS by plasma are shallow compared to those modified by chemically treatment. The static contact angles were measured with deionized (DI) water droplets on the modified surfaces in order to observe for any changes in chemical activities and wettability. The surfaces modified by plasma showed smaller contact angles, and their modified states lasted longer than those modified by chemical etching. Adhesion strengths were measured using 3M tape (3M 810D standard) and by 90° peel-off tests. The peel-off test revealed the stronger adhesion of the Ni films on the plasma-modified surfaces than on the chemically modified surfaces. Thermal shock test was performed by changing the temperature drastically to see if any detachment of Ni film from ABS would occur due to the differences in thermal expansion coefficients between them. Only for the plasma-treated samples showed no separation of the Ni films from the ABS surfaces in tests. The adhesion strengths of metallic films on the ABS processed by the method developed in this study are better than those of the chemically processed films.

• Analytical Science and Technology
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• v.30 no.2
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• pp.75-81
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• 2017

5-methylthioninhydrin (5-MTN) is an amino acid sensitive reagent used for the development of latent fingermarks deposited on porous surfaces such as paper and wood. The present study demonstrates that the 5-MTN can be used as a latent footwear impression enhancement reagent, by reacting with trace multivalent metal ions, which are the main components of the latent footwear impression. 5-MTN and L-alanine complex (MTN-ALA) used for the latent footwear impression development was prepared, by mixing $4.5{\times}10^{-3}M$ 5-MTN (in methanol) and $4.5{\times}10^{-3}M$ L-alanine (in methanol) in 1:1 ratio, and keeping undisturbed at room temperature for 24 h. The latent footwear impressions were deposited on white and black non-porous surfaces (glass plate, polyethylene panel, polypropylene panel, acryl panel, polyvinyl chloride (PVC) panel, poly(methyl methacrylate) (PMMA) panel, acrylonitrile-butadiene-styrene (ABS) panel, tile), and a semi-porous surfaces (painted wood). The latent footwear impressions on these surfaces were treated with MTN-ALA complex by spraying. The fluorescence of footwear impressions (occurred due to the reaction between MTN-ALA and metal complexes) was observed under a 505 nm forensic light source and an orange barrier filter. The enhancement of latent footwear impression was achieved from black surfaces without any blurring. However, the fluorescence (enhancement) of footwear impression was not observed on the white PVC, PMMA, and ABS surfaces, because the incident light interfered and reflected on the surface. The sensitivity of MTN-ALA was superior to 2,2'-dipyridil, which is a representative non-fluorescing footwear impression enhancement reagent, and similar to 8-hydroxyquinoline, which is a representative fluorescing footwear impression enhancement reagent.