• 반도체디스플레이기술학회지
• /
• 제18권1호
• /
• pp.92-96
• /
• 2019

In the presence of ${\mu}-tip$ embedded in a slot-die head for stripe coatings, there arises the capillary flow that limits an increase of the stripe density, which is required for the potential applications in organic light-emitting diode displays. With an attempt to suppress it, we have employed a computational fluid dynamics software and performed simulations by varying the ${\mu}-tip$ length and the contact angles of the head lip and ${\mu}-tip$. We have first demonstrated that such a capillary flow phenomenon (a spread of solution along the head lip) observed experimentally can be reproduced by the computational fluid dynamics software. Through simulations, we have found that stronger capillary flow is observed in the hydrophilic head lip with a smaller contact angle and it is suppressed effectively as the contact angle increases. When the contact angle of the head lip increases from $16^{\circ}$ to $130^{\circ}$, the distance a solution can reach decreases sharply from $256{\mu}m$ to $44{\mu}m$. With increasing contact angle of the ${\mu}-tip$, however, the solution flow along the ${\mu}-tip$ is disturbed and thus the capillary flow phenomenon becomes more severe. If the ${\mu}-tip$ is long, the capillary flow also appears strong due to an increase of flow resistance (electronic-hydraulic analogy). It can be suppressed by reducing the ${\mu}-tip$ length, but not as effectively as reducing the contact angle of the head lip.

• 한국분무공학회지
• /
• 제3권4호
• /
• pp.8-15
• /
• 1998

The spray characteristics of emulsified fuel of W/O type has been experimentally investigated. The mixture of light oil and water by using ultrasonic energy adding system is used as the emulsified fuel. The SMD of sprayed droplet of emulsified fuel is measured by using the particle size analyzer. Major parameters of the present experimental study are the volume fraction of water in emulsified fuel, $0\sim30%$ by 5%, injection pressure, $10kg_f/cm^2\sim18kg_f/cm^2$ by $2kg_f/cm^2$, and the measurement distance, $10\sim100mm$, between injection nozzle tip and analyzer beam. Compared with light oil, the SMD of emulsified fuel is larger gradually by increasing the volume fraction of water in emulsified fuel, heightening injection pressure and increasing the spray distance. Also, In considering the fact that the pattern of drop size distribution of emulsified fuel is alike that of light oil, the real time spray in coincidence with making emulsified fuel by adding ultrasonic energy can stabilize spray pattern without modificating the injection system used by now.

• 한국진공학회지
• /
• 제8권4B호
• /
• pp.530-535
• /
• 1999

W made a near-field optical microscope(NSOM) apparatus and evaluated it. To control the distance between a tip and a sample, we used a piezoelectric translator and a He-Ne laser, and consequently obtained the spatial resolution better than 100nm. For the semiconductor spectroscopic applications, we performed photoluminescence and photocurrent experiments on the GaAs/AlGaAs MQWs samples. In the case of PL experiment, we obtained the low signal to nose ration due to the extremely small power of a light source passing through the nanometric optical fiber tip. However photocurrent experiment shows a hundred times better signal to noise than that of PL experiment. This suggests that photocurrent experiment using NSOM have the possibility to provide the spatial resolution better than 10nm.

• 한국가시화정보학회지
• /
• 제6권2호
• /
• pp.9-13
• /
• 2008

The reproducibility of water droplet formation which is indispensible in the investigation of a drop-on-demand piezoelectrically driven inkjet was verified by checking the size of droplet and distance from the nozzle tip of inkjet head to droplet. Based on the reproducibility of droplet formation, we visualized the formation of micro-scale droplets by acquiring consecutive images at the jetting frequency of 500 Hz for which air bubbles were not generated. Two different electric waveforms were used to drive the piezoelectric actuator. The visualization system consists of a high-speed camera that can capture images up to 250,000fps, a long-distance microscope and a halogen lamp as a light source.

• 대한기계학회논문집B
• /
• 제20권6호
• /
• pp.1941-1947
• /
• 1996

Droplet size measurement technique was established for the sprayed viscous fluid by virtue of the installation of the sprayed-droplet size measurement system employing light scattering method. Atomization test results showed that the mean droplet size of the sprayed viscous fluid is decreased with the increase of the mass ratio of air to fuel and in case of the same air/fuel ratio, also with the increase of viscous fluid flow rate, and is increased with the distance from atomizer tip. Basic design data for the manufacture of external-mixing type, Y-Jet type, and internal-mixing type atomizers was acquired from the atomization tests.

• 센서학회지
• /
• 제13권3호
• /
• pp.213-217
• /
• 2004

The general method to find a H. pylori in the stomach is the rapid urease test but it is only used to decide the infection with H. pylori. In this study, it is tried to develope fiber-optic pH sensor which can be used with gastroscop to quantify H. pylori. To measure the degree of infection with H. pylori, the color change of phenol red according to the degree of pH is measured by optical fibers with different light sources and the optimum distance from a sample to the end of sensor tip is decided by measuring the maximum reflectivity from a sample. Also the sensitivity study is carried out to decide the optimum light source which has sensitive change of reflectivity to the change of pH. It is expected that the fiber-optic pH sensor which measures the degree of infection with H. pylori exactly can be developed.

• Current Optics and Photonics
• /
• 제5권3호
• /
• pp.229-237
• /
• 2021

The capabilities of the near-field scanning optical microscope (NSOM) for obtaining high resolution lateral topographical images as well as for mapping the spectroscopic and optical properties of a sample below the diffraction limit of light have made it an attractive research field for most researchers dealing with optical characteristics of materials in nano scales. The apertured NSOM technique involves confining light into an aperture of sub-wavelength size and using it to illuminate a sample maintained at a distance equal to a fraction of the sub-wavelength aperture (near-field region). In this article, we present a setup for developing NSOM using a cantilever with a sub-wavelength aperture at the tip. A single laser is used for both cantilever deflection measurement and near-field sample excitation. The laser beam is focused at the apex of the cantilever where a portion of the beam is reflected and the other portion goes through the aperture and causes local near-field optical excitation of the sample, which is then raster scanned in the near-field region. The reflected beam is used for an optical beam deflection technique that yields topographical images by controlling the probe-sample in nano-distance. The fluorescence emissions signal is detected in far-field by the help of a silicon avalanche photodiode. The images obtained using this method show a good correlation between the topographical image and the mapping of the fluorescence emissions.

• 대한치과보철학회지
• /
• 제44권1호
• /
• pp.1-9
• /
• 2006

Purpose: The purpose of this study was to evaluate the efficacy and substitute possibility of a newly developed flowable composite resins as a luting cement for translucent fiber post. Material & Method: Two kinds of 12 mm translucent fiber Post (D.T. Light-Post (Bisco, USA) and FRC Postec (Ivoclar vivadent, Liechtenstein) was inserted into the teflon mold (7 mm diameter, 9 mm long) and Filtek-Flow (3M ESPE. USA), a light activated flowable composite resin, was polymerized for 60 seconds through the post. Also, the post was cut from the tip to 9 mm, 6 mm, 3 mm, and Filtek-Flow was light cured according to each length. For comparison, 60 seconds light-cured and 24 hours self-cured two dual cured resin cement (Duo-cement (Bisco, USA) and 2 Panavia-F (Kuraray, Japan)) samples were prepared as control group. Also cavities (1 mm in width, 1 mm in depth and 12 mm in length) were prepared using acrylic plate and aluminum bar, and flowable composite resin was flied and light cured by the diffused light from the fiber post's side wall. The degree of polymerization was measured according to the distance from curing light using Vickers' hardness test. Result: Within the limitation of this study, the following conclusions were drawn: 1. Vickers' hardness of light cured dual cured resin cement and flowable composite resin decreased from Panavia-F, Filtek-Flow and Duo-cement accordingly (p<0.05). In the dual curing resin cement, light curing performed group showed higher surface hardness value than self cured only group (p<0.05). 2. Surface hardness ratio (light cured through fiber post /directly light cured) of D.T. Light-Post using Filtek-Flow showed about 70% in the 6 mm deep and about 50% in the 12 mm deep FRC Postec showed only 40% of surface hardness ratio. 3. Surface hardness ratio by diffused light from the post's side wall showed about 50% at 6 mm and 9 mm deep, and about 40% at 12 mm deep in D.T. Light-Post. However, FRC Postec showed about 40% at 6 mm deep, and almost no polymerization in 9 mm and 12 mm deep.

• 한국분무공학회지
• /
• 제13권4호
• /
• pp.212-219
• /
• 2008

To develop the twin-fluid atomizer having the excellent performance of painting, the spray characteristics of how a wide area can be painted efficiently by one time spraying were studied in this paper. Spray phenomena are affected by the many factors determining the spray field such as the spraying pressure of gas, the spraying pressure and viscosity of liquid paints, the opening duration of needle valve, the design dimension of nozzle, and so on. As the results of experiments, these factors affecting on spray characteristics were suggested as followings; 1) The optimum spraying pressure of gas was $0.015{\sim}0.02\;kPa$, and the appropriate spraying pressure of liquid paint was 0.01kPa, In these situations, the setting up pressures must be compensated as much as the losing amount of pressure because a decompression occurred when operating valves. 2) The duration of opening the needle valve must be sustained for $1{\sim}2$ seconds to inject gas after spraying the liquid paint. This operating of the needle valve was necessary to avoid the affect on the changing of liquid column length, and to prevent the droplet deposit at the initial time of spraying. 3) The spray tip penetration was gained form the experimental equation, and the effective spraying angle was $85^{\circ}{\pm}5^{\circ}$ just at he appropriate spraying pressure of gas. The distribution of the area sprayed had the variation in $350{\pm}50\;mm$ because of the spraying pressure of gas, the its distance from the spray tip, and the lift of the needle valve.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.110-110
• /
• 2011

The nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value for lithiated silicon nanowire and a higher value for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value than that of the Si nanowire substrate by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The Young's modulus obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively higher value than lithiated silicon nanowire due to the elastically soft amorphous structures. The frictional forces acting on the tip sliding on the surface of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process.