• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.329-338
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• 2006

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the mode.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.395-398
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• 2001

Recently, the increasing need for internet and the activation of hiring business of communication line makes the demand for OPGW cable which can construct the optical communication network in the basis of existing overhead power transmission line. Especially, the demand is focused on the high fiber count OPGW due to high capacity transmission. In step with the trend toward high fiber count cable we have developed the Stainless Steel Loose Tube type OPGW within which have 144core firstly in KOREA. This paper describes the cable design and manufacturing process which gives the stable operation in very severe conditions and the long-term reliability test results conducted in according to dominant specification IEEE Std. 1138-1194.

• ETRI Journal
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• v.38 no.1
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• pp.9-17
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• 2016

We demonstrate a time- and wavelength-division multiplexed passive optical network system employing a vertical-cavity surface-emitting laser array-based optical line terminal transceiver and a tunable bidirectional optical subassembly-based optical network terminal transceiver. A packet error-free operation is achieved after a 40 km single-mode fiber bidirectional transmission. We also discuss an arrayed waveguide grating, a photo detector array based on complementary metal-oxide-semiconductor photonics technologies, and low-cost key devices for deployment in access networks.

• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.59-71
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• 2002

Photonic band gap structures have a high potential for nearly zero-threshold lasers. This paper describes new-types of low-threshold photonic crystal lasers fabricated in InGaAsP slab waveguides free-standing in air. Two-types of photonic crystal lasers are studied. One is a single-cell nano-cavity laser formed in a square array of air holes. This photonic band gap laser operates in the smallest possible whispering gallery mode with a theoretical Q >30000 and exhibits low threshold pump power of 0.8 mW at room temperature. The nther laser does not have any cavity structure and the lasing operation originates from the enhanced optical density of states near photonic band edges. A very low threshold of 35 $\mu$W (incident pump power) is achieved from this laser at 80 K, one of the lowest values ever reported. This low threshold is benefited from low optical losses as well as enhanced material gain at low temperature.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.222-227
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• 1995

A single mode, 100-mW diode laser was injection-locked by the master laser which was spectrally narrowed with Littman-type grating feedback. In the incomplete-injection-locking, we observed that two frequencies were simultaneously generated from the slave laser. The power ratio and frequency shift of two frequency components were proportional to the square of injected laser intensity. When the ratio of the injection intensity to the slave laser intensity was about $10^{-3}$, the injection-locking bandwidth was to be about 1.4 GHz. The bandwidth proportionally increased to the square root of the injection intensity, which was in good agreement with the theoretical predictions. The Iinewidth of the locked-laser was about 2.5 MHz, which was five times as narrow as that of free-running operation. ation.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.543-553
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• 2007

It is becoming increasingly difficult for engines using conventional fuels and combustion techniques to meet stringent emission norms. The homogeneous charge compression ignition(HCCI) concept is being evaluated on account of its potential to control both smoke and NOx emissions. However, HCCI engines face problems of combustion control. In this work, a single cylinder water-cooled diesel engine was operated in the HCCI mode. Diesel was injected during the suction stroke($0^{\circ}$ to $20^{\circ}$ degrees aTDC) using a special injection system in order to prepare a nearly homogeneous charge. The engine was able to develop a BMEP(brake mean effective pressure) in the range of 2.15 to 4.32 bar. Extremely low levels of NOx emissions were observed. Though the engine operation was steady, poor brake thermal efficiency(30% lower) and high HC, CO and smoke were problems. The heat release showed two distinct portions: cool flame followed by the main heat release. The low heat release rates were found to result in poor brake thermal efficiency at light loads. At high brake power outputs, improper combustion phasing was the problem. Fuel deposited on the walls was responsible for increased HC and smoke emissions. On the whole, proper combustion phasing and a need for a well- matched injection system were identified as the important needs.

• Membrane Journal
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• v.7 no.4
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• pp.175-182
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• 1997

Membrane-bioreactor process which combines anaerobic-aerobic bioreactor and membrane process, was used to remove refractory organic susbstances and dye molecule in textile wastewater effectively. Direct feeding of raw feed water to membrane process caused serious fouling on membrane. On the other hand, pretreated feed by bioreactor before the membrane process remarkably reduced the fouling and prolonged the membrane life. Removal efficiency and fouling were more dependent on the material property of the membrane rather than the membrane pore size and structure. Operation mode of hollow fiber membrane module and linear velocity in the hollow fiber influenced the ramoval efficiency and the water flux of the membrane. The combined membrane- bioreactor process was more effective in treating the textile wastewater than each single process.

• Current Optics and Photonics
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• v.1 no.1
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• pp.65-72
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• 2017

We propose a nearly lossless, compact, electrically modulated vertical directional coupler, which is based on the controllable evanescent coupling in a previously proposed graphene-assisted total internal reflection (GA-FTIR) scheme. In the proposed device, two single-mode waveguides are separate by graphene-$SiO_2$-graphene layers. By changing the chemical potential of the graphene layers with a gate voltage, the coupling strength between the waveguides, and hence the coupling length of the directional coupler, is controlled. Therefore, for a properly chosen, fixed device length, when an input wave is launched into one of the waveguides, the ratio of their output powers can be controlled electrically. The operation of the proposed device is analyzed, with the dispersion relations calculated using a model of a one-dimensional slab waveguide. The supermodes in the coupled waveguide are calculated using the finite-element method to estimate the coupling length, realistic devices are designed, and their performance was confirmed using the finite-difference time-domain method. The designed $3{\mu}m$ by $1{\mu}m$ device achieves an insertion loss of less than 0.11 dB, and a 24-dB extinction ratio between bar and cross states. The proposed low-loss device could enable integrated modulation of a strong optical signal, without thermal buildup.

• Korean Journal of Optics and Photonics
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• v.29 no.6
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• pp.247-252
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• 2018

We report amplification of a small signal in a diode-pumped Cs vapor cell with 500 torr of ethane buffer gas, in the low-pump-power regime of 200 mW or less. For efficient amplifier operation, the pump and signal beams were coupled to a single-mode optical fiber, and completely overlapped in the Cs vapor cell. We investigated the amplification of the small signal according to cell temperature, signal power, and pump power. An amplification factor of 56 was achieved under the conditions of cell temperature of $115^{\circ}C$, signal power of 0.1 mW, and pump power of 200 mW.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.1-8
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• 2019

Breath analysis using a portable device is better than the classical breath analysis system in terms of installation and operation. There is an increasing need to develop cost-effective equipment for testing gas sensors from the viewpoint of functionalities that can be applied applicable to portable devices. In the present study, an economical gas chamber for in-situ gas measurement is implemented with a single gas chamber without using expensive gas storage and control equipment; the gas response characteristics are analyzed using the above-described chamber. The main features of the implemented gas chamber are simple injection procedure, improved gas diffusion, easy measurement and cleaning, support for low-power mode measurement function for portable devices, and open source platform. Moreover, an analysis of gas response characteristics based on changes in sensor voltage show that the sensitivity and 90% response time are affected by the sensor voltage. Furthermore, the sensitivity graph has an inflection point in a specific range. The gas sensor applied in this study showed fast response speed and high sensitivity for sensor voltages of 3.0-3.5 V, regardless of the concentration of acetone gas, the target gas used in this study.