• Particle and aerosol research
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• v.13 no.4
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• pp.159-164
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• 2017

The detection efficiency and characteristics of an optical particle counter (OPC), with various sample nozzle outlet diameters, were experimentally investigated. The OPC system, which was built with original design, was made up of a diode laser, two photodetectors, and a variety of optics such as a beam splitter and a concave mirror. The cone-shaped sampling nozzle was designed to be changeable to alter the outlet diameter, within the range of 1 to 3 mm. For samples, sets of polystyrene latex (PSL) standard particle with various sizes of 1 to $3{\mu}m$, were used. As a result, detection efficiency of the OPC greatly decreased with larger nozzle outlet diameter. Moreover, increased nozzle outlet diameter means broader sample flow, thus caused light interference and multiple scattering which results in abnormal high peaks in scattered light signal. The ratio of abnormal peaks to regular signal of single particle increased with larger nozzle outlet diameter.

• ETRI Journal
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• v.13 no.4
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• pp.2-9
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• 1991

Buried-heterostructure lasers are more difficult to fabricate than weakly index guided or gain guided lasers. However, these strongly index guided structures are most suitable for a source of lightwave transmission systems. But, for conventional etched mesa buried heterostructure lasers, the regrowth of InP blocking layer is difficult and irreproducible. So, there are inevitable leakage currents flowing outside the active region resulting poor performance. To eliminate these problems, we used a planar buried heterostructure. As a results, the average threshold current was 28mA and the differential quantum efficiency was about 20% per facet for $1.3\mum$ GaInAsP/InP PBH-LD. The initial forward leakage current was not exceeding $1\muA$ and the reverse voltage for $-10\muA$ was -3V~-5V, these are improved figure of 1mA~10mA and -1V~-3V for EMBH laser diode. The chip modulation bandwidth was more than 2.4GHz for $1.5I_th$.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.71-78
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• 2007

There have been continuous efforts to automate welding processes. This automation process could be said to fall into two categories, weld seam tracking and weld quality evaluation. Recently, the attempts to achieve these two functions simultaneously are on the increase. For the study presented in this paper, a vision sensor is made, and using this, the 3 dimensional geometry of the bead is measured in real time. For the application in welding, which is the characteristic of nonlinear process, a fuzzy controller is designed. And with this, an adaptive control system is proposed which acquires the bead height and the coordinates of the point on the bead along the horizontal fillet joint, performs seam tracking with those data, and also at the same time, controls the bead geometry to a uniform shape. A communication system, which enables the communication with the industrial robot, is designed to control the bead geometry and to track the weld seam. Experiments are made with varied offset angles from the pre-taught weld path, and they showed the adaptive system works favorable results.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.256-261
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• 2013

Power conversion efficiency of the red and green phosphors was measured and analyzed. Two different samples of phosphors of thickness 50 ${\mu}m$ were prepared: one was the phosphor layer coated on the transparent substrate and the other was prepared on the reflective substrate. The 445 nm blue laser diode beam was used as the exciting beam. The conversion efficiencies of the red and green phosphor layers were 41.4% and 46%, respectively. The quantum efficiencies of the red and green phosphors were 60.4% and 53.5%, respectively.

• ETRI Journal
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• v.29 no.5
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• pp.633-640
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• 2007

We report an experimental demonstration of 40 Gbps all-optical 3R regeneration with all-optical clock recovery based on InP semiconductor devices. We also obtain alloptical non-return-to-zero to return-to-zero (NRZ-to-RZ) format conversion using the recovered clock signal at 10 Gbps and 40 Gbps. It leads to a good performance using a Mach-Zehnder interferometric wavelength converter and a self-pulsating laser diode (LD). The self-pulsating LD serves a recovered clock, which has an rms timing jitter as low as sub-picosecond. In the case of 3R regeneration of RZ data, we achieve a 1.0 dB power penalty at $10^{-9}$ BER after demultiplexing 40 Gbps to 10 Gbps with an eletroabsorption modulator. The regenerated 3R data shows stable error-free operation with no BER floor for all channels. The combination of these functional devices provides all-optical 3R regeneration with NRZ-to-RZ conversion.

• Korean Journal of Bronchoesophagology
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• v.16 no.2
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• pp.154-156
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• 2010

We report a case of actinomycotic infection in epiglottis. Actinomycosis in the head and neck area is relatively rare but extremely rare in the larynx. A 63-year old man presented with continuous discomfort of the throat while swallowing. He had a history of oral injury caused by a fish bone a few weeks prior. Upon Examination with a flexible laryngoscope, a whitish round mass was noted at the lingual surface of the epiglottis. Under local anesthesia, a punch biopsy was performed and showed the typical features of actinomycosis. The mass was removed using a Diode laser under suspension laryngoscope. Additive oral antibiotic therapy was done for 2 weeks. No definite recurrence was noted at the operation site and the patient is now free of disease.

• Journal of Navigation and Port Research
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• v.34 no.5
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• pp.305-309
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• 2010

This paper is provided to improve the discrimination of the towing line for tug-barge at the night sailing. As tugboat industry develops, marine accidents by tugboats are increasing. The main cause of accidents by tugboats is operators' negligence, and that portion is over 70 percent in total marine casualties by tugboats. The biggest cause of negligence is the passing through the towing line at night time. This paper suggests the ways to hinder operators' transit and improve discrimination of towing line(s) at night time.

• Transactions of the Society of Information Storage Systems
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• v.10 no.2
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• pp.32-38
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• 2014

Heat emission from the laser diode used in the optical disc drive and the defects from the increased temperature at the system have attracted attentions from the field of the information storage device. Thermoelectric refrigerator is one of the fine solutions to solve these thermal problems. The refrigeration performance of thermoelectric device is dependent on the thermoelectric material's figure-of-merit. Meanwhile, high electrical contact resistivity between metal electrode and p- and n-type thermoelectric materials in the device would lead increased total electrical resistance resulting in the degeneracy in performance. This paper represents the manufacturing process of the PbTe-based material which has one of the highest figure-of-merit at medium-high-temperature, ~ 600K to 900 K, and the nickel contact layer for reduced electrical contact resistance at once, and the results showing the decent contact structure and figure-of-merit even after the long-term operation environment.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.229-231
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• 1996

We are studied the stability of amorphous and crystalline $Te_{100-x}Ge_x$ (x=10, 15. 25, 40, 50, 60 at.%) thin films by observing the degradation in 8O%RH/$66^{\circ}C$ environment and the reflectance ratio. The degradation was observed with the transmittance and reflectance, the reflectance was measured at 780nm in the wavelength range of diode laser. In amorphous $Te_{100-x}Ge_x$ thin films of below x=4O at.%, the degradation was observed, the thin film of x=10 at.% was shown the degradation degree of 12.5%. In crystalline $Te_{100-x}Ge_x$ thin films of x=10, 40 at.%, the degradation degree were 12.8%, 13%, respectively. The reflectance ratio were shown above 20% in. all composition ratio. Therefore, we are expected that $Te_{100-x}Ge_x$ thin films of x=50, 60 at.% has the long life for the optical recording media.

• Transactions of the Society of Information Storage Systems
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• v.3 no.4
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• pp.191-195
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• 2007

The optical disc drive has used a high NA objective lens and a shorter wavelength laser diode for high recording density. But high NA and shorter wavelength cause several margins to become short. Focusing and tracking servo has to be more accurate and active tilt compensation mechanism is also needed for coma aberration compensation. In this paper, we proposed 3-axis moving magnet type actuator. For 3-DOF motion, moving coil actuator has to be equipped with 6 wires for supplying 3 independent signals. However, moving magnet type actuator doesn't need to change the configuration of wires because coils are in stator. So, we added a tilt mechanism to the 2-axis moving magnet actuator which is designed in previous research. Addition of the tilt mechanism cuts down the focus sensitivity. So, maximization the tilting sensitivity and securing the focusing sensitivity are objectivities of this research. DOE (design of experiments) procedures of electromagnetic circuit are performed for parameter study and the optimization is also performed to maximize the tilt sensitivity. And then the final design is suggested and its performance is verified by FE simulation.