• Tribology and Lubricants
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• v.32 no.6
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• pp.207-211
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• 2016

To interpret the perception that originates from tactile sensibility during people touch and recognize the object surfaces, this study focuses on the development of a friction model that can describe the interaction of a stylus pen sliding over the counter surfaces. In addition, the study includes several other experimental factors such as the pressure, temperature, and topology of surface, which can have an effect on the emotional user experience concerning various surfaces; this research aims to suggest a method to quantitatively evaluate the relation between these experimental parameters and emotional user experience. Accordingly, the objective of research comprises the friction characteristic technology for measurement of fine tribological behavior and a standard to quantify the emotional feedback. Existing panels or input devices that provide interaction feedback about user actions simply operate with a single frequency vibration or sound response. On the contrary, this research investigates various interaction characteristics including friction force, frequency, and surface topology synthetically. Using the developed model, which can explain the relation between the friction parameters and emotional user experience, developers can design their product in order to provide the user with expected emotional sensibility. Consequently, it can contribute to reduce the development cost about sensitivity model.

• Journal of Integrative Natural Science
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• v.6 no.4
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• pp.215-219
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• 2013

In this study, in order to investigate how consecutive treatments of glass surface with HF acid and water vapor/Ar plasma affect the quality of 3-aminopropyltriethoxysilane self-assembled monolayer (APS-SAM), poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were vapor phase-polymerized immediately after spin coating of FeCl3 and poly-urethane diol-mixed oxidant solution on the monolayer surfaces prepared at various treatment conditions. For the film characterization, various poweful tools were used, e.g., FE-SEM, an optical microscope, four point probe, and a contact angle analyzer. The characterization revealed that a well prepared APS-SAM on a glass surface treated with water vapor/Ar plasma is very useful for uniform coating of FeCl3 and DUDO mixed oxidant solution, regardless of HF treatment. On the other hand, a bare glass surface without APS-SAM but treated with HF and water vapor/Ar plasma generally led to a very poor oxidant film. As a result, PEDOT films vapor phase-polymerized on APS-SAM surfaces are far superior to those on bare glass surfaces in the quality and electrical characteristics aspects.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.5
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• pp.443-450
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• 2006

The present study has been conducted to investigate the effects of rotation on heat/mass transfer and pressure drop characteristics in a two-pass square duct with and without discrete ribs. For stationary cases, the heat/mass transfer on the surfaces with and without discrete ribs is almost the same or reduced. For rotating cases, the gap flow affects differently the heat/mass transfer on leading and trailing surfaces with discrete ribs. On the leading surface of the first pass, the heat/mass transfer is slightly enhanced due to generating strong gap flow. On the trailing surface of the first pass, however, the heat/mass transfer is much decreased because the gap flow disturbs impingement of main flow. The phenomenon, that is, the heat/mass transfer discrepancy between the leading and trailing surfaces is distinctly presented with the increment of rotation number. The friction losses on each surface with discrete ribs are reduced because the blockage ratio decreases for both non-rotating and rotating cases. Therefore, high thermal performance appears in a duct with discrete ribs.

• Journal of Periodontal and Implant Science
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• v.42 no.3
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• pp.81-87
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• 2012

Purpose: The characteristics of oxidized titanium (Ti) surfaces varied according to treatment conditions such as duration time and temperature. Thermal oxidation can change Ti surface characteristics, which affect many cellular responses such as cell adhesion, proliferation, and differentiation. Thus, this study was conducted to evaluate the surface characteristics and cell response of thermally treated Ti surfaces. Methods: The samples were divided into 4 groups. Control: machined smooth titanium (Ti-S) was untreated. Group I: Ti-S was treated in a furnace at $300^{\circ}C$ for 30 minutes. Group II: Ti-S was treated at $500^{\circ}C$ for 30 minutes. Group III: Ti-S was treated at $750^{\circ}C$ for 30 minutes. A scanning electron microscope, atomic force microscope, and X-ray diffraction were used to assess surface characteristics and chemical composition. The water contact angle and surface energy were measured to assess physical properties. Results: The titanium dioxide ($TiO_2$) thickness increased as the treatment temperature increased. Additional peaks belonging to rutile $TiO_2$ were only found in group III. The contact angle in group III was significantly lower than any of the other groups. The surface energy significantly increased as the treatment temperature increased, especially in group III. In the 3-(4,5-Dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay, after 24 hours of incubation, the assessment of cell viability showed that the optical density of the control had a higher tendency than any other group, but there was no significant difference. However, the alkaline phosphatase activity increased as the temperature increased, especially in group III. Conclusions: Consequently, the surface characteristics and biocompatibility increased as the temperature increased. This indicates that surface modification by thermal treatment could be another useful method for medical and dental implants.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.2 s.245
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• pp.126-135
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• 2006

The pressure drop characteristics in a rotating two-pass duct with rib turbulators are investigated in the present study. The square duct has a hydraulic diameter $(D_h)$ of 26.7 mm, and $1.5mm{\times}1.5mm$ square $90^{\circ}-rib$ turbulators are attached on the leading and trailing walls. The pitch-to-rib height ratio (p/e) is 10. The distance between the tip of the divider and the outer wall of the duct is $1.0D_h$ and the width of divider wall is 6.0mm or $0.225D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000 to exclude the Reynolds effect, and the rotation number (Ro) is varied from 0.0 to 0.20. The pressure drop distribution, the friction factor and thermal performance are presented for the leading, trailing and the outer surfaces. It is found that the curvature of the $180^{\circ}$-turn produces Dean vortices that cause high pressure drop in the turn. The channel rotation results in pressure drop discrepancy between leading and trailing surfaces so that non-dimensional pressure drops are higher on the trailing surface in the first-pass and on the leading and side surfaces in the second-pass. In the turning region, Dean vortices shown in the stationary case transform into one large asymmetric vortex cell, and subsequent pressure drop characteristics also change. As the rotation number increases, the pressure drop discrepancy enlarges.

• Tribology and Lubricants
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• v.33 no.3
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• pp.92-97
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• 2017

The understanding of the friction characteristics of micro-textured surface is of great importance to enhance the tribological properties of nano- and micro-devices. We fabricate rectangular patterns with submicron-scale structures on a Si wafer surface with various pitches and heights by using a focused ion beam (FIB). In addition, we fabricate tilted rectangular patterns to identify the influence of the tilt angle ($45^{\circ}$ and $135^{\circ}$) on friction behaviour. We perform the friction test using lateral force microscopy (LFM) employing a colloidal probe. We fabricate the colloidal probe by attaching a $10{\pm}1-{\mu}m$-diameter borosilicate glass sphere to a tipless silicon cantilever by using a ultraviolet cure adhesive. The applied normal loads range between 200 nN and 1100 nN and the sliding speed was set to $12{\mu}m/s$. The test results show that the friction behavior varied depending on the pitch, height, and tilt angle of the microstructure. The friction forces were relatively lower for narrower and deeper pitches. The comparison of friction force between the sub-micro-structured surfaces and the original Si surface indicate an improvement of the friction property at a low load range. The current study provides a better understanding of the influence of pitch, height, and tilt angle of the microstructure on their tribological properties, enabling the design of sub-micro- and micro-structured Si surfaces to improve their mechanical durability.

• The Journal of Advanced Prosthodontics
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• v.2 no.4
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• pp.142-147
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• 2010

PURPOSE. One of the major keys to achieve successful osseointegration of the implant is its surface properties. The aim of this study was to investigate the bone response to dental implants with different surface characteristics using the rabbit tibia model. Tricalcium phosphate (TCP) coated, anodic oxidized and turned (control) surfaces were compared. MATERIALS AND METHODS. Seventy two implants were placed in the tibia of eighteen rabbits. Nine rabbits were sacrificed at 3 weeks of healing and the remaining nine were sacrificed at 6 weeks of healing. The bone-to-implant contact (BIC) and the bone volume density (BVD) were assessed by light microscope after 3 and 6 weeks of healing. RESULTS. Statistical analysis showed that no significant differences in the BIC and BVD were observed between the different implant surfaces and the control group at 3 weeks and 6 weeks of healing. Data also suggested that the BVD of all the surfaces showed significant difference at 3 and 6 weeks. CONCLUSION. The present study has showed that osseointegration occurred in all investigated types of surface-treated implants. In the current study all of the threads of the implants were observed to calculate BIC and BVD values (instead of choosing some of the threads from the bone cortex for example), which didn't make BIC or BVD percentage values better than in the control group, therefore the clinical relevance of these results remains to be shown.

• Tribology and Lubricants
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• v.33 no.2
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• pp.52-58
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• 2017

An ultra-high precise ejection process is essential in a dispensing system for fabricating various precision parts such as a semiconductor, LED, and camera module. The size of such parts has been decreasing, which implies that a precise ejecting technique is required. A phosphor-containing liquid is ejected via a dispenser using dual piezoelectric actuators that are used for generating a high-speed dispensing mechanism. The rod and nozzle continuously contact in high speed to eject the liquid. However, the high-strength filler or phosphor in the liquid causes wear on the surfaces of the rod and nozzle during the dispensing process. As a result, the ejection reliability decreases as the wear on the surfaces increases. Therefore, it is necessary to estimate the wear characteristics of the rod and nozzle via an experiment and FE analysis. Reliability rests up to 1,000 cycles are conducted under relatively severe conditions. The flow rate and surfaces roughness of the rod and nozzle are measured in each ejection cycle. The surface images and wear volume are obtained before and after the tests and the ejection reliability is confirmed by measuring the flow rate of the liquid. The experimental results show that the ejection reliability is maintained up to 1,000k cycles; these results are validated by the simulation results.

• Korean Journal of Remote Sensing
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• v.16 no.1
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• pp.65-72
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• 2000

Scattering coefficients of randomly rough lossy dielectric surfaces were computed by using the FDTD(Finite-Difference Time-Domain) method and the Monte Carlo method in this paper. The FDTD method was applied to compute electromagnetic wave scattering characteristics at any incident angles, any linear polarizations by dividing the computation region into the total-field region and the scattered-field region. The radar cross sections(RCS) of conducting cylinders have been computed and compared with theoretical results, measurement data and the results from the method of moment(MoM) to verify the FDTD algorithm. Then, to apply the algorithm to compute scattering coefficients of distributed targets, a two-dimensionally rough surface was generated numerically for given roughness characteristics. The far-zone scattered fields of 50 statistically independent dielectric rough surfaces were computed and the scattering coefficient of the surface was calculated from the scattered fields by using the Monte Carlo method. It was found that these scattering coefficients agree well with the SPM(Small Pertubation Method) model in its validity region.

• Composites Research
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• v.22 no.6
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• pp.39-44
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• 2009

The effect of exposure times on the aging characteristics of carbon fiber/epoxy composite ring specimen was evaluated using an accelerating aging tester. Combined exposure conditions, such as temperature, moisture, and ultraviolet, were applied up to 3000 hours. Tensile properties and flexural properties including the effect of curvature were evaluated on the specimens subject to various exposure times through a material testing system. Their aging surfaces were observed through a scanning electron microscope. According to the results, tensile modulus was little affected by the exposure times. However, tensile strength, at the early stage of the exposure times, increased due to physical aging and curing reaction, but tensile strength slightly decreased due to degradation as the exposure times increased. The flexural modulus and flexural strength increased at the early stage of the exposure times, but slightly decreased as the exposure times increased. Aging surfaces of the specimens examined using the scanning electron microscope revealed a different morphology in various exposure times and provided useful information for identifying the degradation in mechanical properties of the composite subject to various exposure times.