• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.865-870
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• 2014

Gold nanoparticles (AuNPs) were synthesized by laser (Nd:YAG, ${\lambda}$ = 1064 nm) ablation of a gold target immersed in various aqueous electrolyte solutions (7 mM of LiCl, NaCl, KCl, NaBr, and NaI) as well as in deionized water. The surface plasmon absorption and EDX of AuNPs so produced as well as their TEM images were analyzed to investigate the effects of ambient ions on the growth and aggregation of NPs. The size of AuNPs was reduced by laser ablation in the presence of chloride and bromide ions while it increased drastically when AuNPs were formed in iodide solution. Interestingly, triangular nanoplates were synthesized only in iodide solution. Surface chemistry on AuNPs in various electrolyte solutions was explored to elucidate the role of ions on the size and stability of AuNPs.

• 한국자동차공학회논문집
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• 제9권4호
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• pp.85-91
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• 2001

LPG has been well known as a clean alternative fuel for vehicles. As a fundamental study on liquid phase LPG injection (hereafter LPLI) system application to heavy-duty engine, engine output and combustion performance were investigated with various operating conditions using a single cylinder engine equipped with the LPLI system. Experimental results revealed that no problems were occurred in application of the LPG fuel to heavy-duty engine, and that volumetric efficiency and engine output, by 10% approximately, were increased with the LPLI system. It was resulted from the decrease of the intake manifold temperature through liquid phase LPG fuel injection. These results provided an advantage in the decrease of the exhaust gas temperature, in the control of knocking phenomena, spark timing and compression ratio. The LPLI engine could normally operated under $\lambda$=1.5 or EGR 30% condition. The optimized swirl ratio for the heavy duty LPG engine was found around R_s$ = 2.0.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.132-142
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• 1999

In this paper, a new formula for primary and secondary thrust of metal belt CVT is proposed considering variation of band tension, block compression and active arc for each of the primary and secondary pulleys. For the secondary thrust, effective friction coefficient is introduced considering the effect of flange deflection. Nondimensional primary and secondary thrust of the metal belt CVT by the new formula agree well with the experimental results except for low torque range, $0\;<\;{\lambda}\;<\;0.2$ at speed ration i = 1.0. The new formula can be used in design of the primary and secondary thrusts control system for the metal belt CVT.

• ETRI Journal
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• 제38권5호
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• pp.879-884
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• 2016

In this paper, an ultra-small marker beacon antenna operated in the VHF-band is proposed. This antenna has a modified linear IFA structure with a lumped capacitor and a capacitive plate for frequency tuning and impedance matching. The capacitive plate is directly connected to the end of a linear radiator and is separated from the antenna ground by 1 mm. The main operating frequency is mainly controlled by the size and dielectric constant of the capacitive plate. The lumped capacitor is useful for fine frequency tuning. Using the proposed structure, an ultra-small marker beacon antenna can be realized with a length of 0.04 ${\lambda}_0$.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.79-92
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• 2015

In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with $0^{\circ}$ orientations in this study. Fiber volume fraction ($v_f$), fiber aspect ratio ($L_f/d_f$), damage length ($L_D$) and its location (${\lambda}/L$), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.

• 전기학회논문지
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• 제57권4호
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• pp.589-595
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• 2008

Detent force of a permanent magnet linear motor(PMLSM) consist of cogging and drag forces, and should be minimized for high precision control purpose applications. This paper shows that the cogging force can be reduced effectively by employing 9 pole 10 slot structure. The drag force is minimized by optimizing the total length and shape of the exterior teeth of armature core simultaneously by using($1+{\lambda}$) evolution strategy coupled with response surface method. After optimization, the optimized PMLSM is proven to reduce 95% and 92.6% of the cogging and total detent forces, respectively, and give 12% and 6.4% higher Back-emf and thrust force, respectively, compared with a conventional 12 pole 9 slot structure under the same condition. Additionally, Simulation results by the proposed optimum design are verified by the experiment results.

• Current Optics and Photonics
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• 제2권5호
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• pp.431-435
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• 2018

A modified setup of a CMD technique for high power coherent beam combining was presented to address an issue of low damage threshold of electro-optic modulators. The feasibility of the modified setup was demonstrated by combining eight fiber beams, and it was successfully performed with ${\lambda}/44$ of residual phase error and 100 Hz of control bandwidth. It is expected that the modified CMD setup facilitates ultra-high power coherent beam combination without a limitation caused by the low damage threshold of electro-optic modulators.

• Journal of Preventive Veterinary Medicine
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• 제41권2호
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• pp.79-83
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• 2017

In this study, we used a choropleth map to explore the spatial variation of the risk of cattle herds being bovine tuberculosis (BTB) positive in Gangwon-do in 2015. The map shows that the risk of being BTB-positive was lower in provinces located in the middle of Gangwon-do (Wonju, Youngwol, Peongchang, and Kangneung) than in other provinces. In addition, one province located in the north (Goseong) had a low risk of BTB. The estimate for the intercept of the spatial lag model was 0.66, and the spatial autocorrelation coefficient (lambda) was 0.20 (Table 1). The Moran's I was 0.33 with p-value of 0.02. In 2015, provinces located in the North West (Hwacheon) and East (Donghae) of Gangwon-do had a higher BTB risk. We identified some specific provinces at low BTB-positive risk, information that may prove useful for control of BTB in the study area.

• 천문학회보
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• 제45권1호
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• pp.29.4-29.4
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• 2020

Structure in the universe forms hierarchically with the small scales forming first and merging into larger scales. Galaxy clusters are at the pinnacle of the formation process. Peering far into the universe, we can observe galaxy clusters early in their evolution. SpARCSJ1049+56 is a galaxy cluster located at a redshift of 1.71. It has been shown to be rich in cluster galaxies, to have intense star formation, and to have a significant amount of molecular gas. Through careful control of systematics, we detected the weak-lensing signal from this distant galaxy cluster. I will present our HST infrared weak-lensing detection of the cluster with a focus on the method. Our lensing analysis found that the cluster is massive and is rare in a LambdaCDM universe. I will also present the Chandra X-ray discovery of cold gas coincident with the intense star formation and discuss the implications of the detection.

• 소성∙가공
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• 제13권3호
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• pp.216-224
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• 2004

In this study, we have developed a new UV$({\lambda}=355nm)$ laser micromachining technology by direct ablation method without masks. This technology allows that 3D micro parts can be fabricated rapidly and efficiently with a low price. And it has a benefit of reducing fabricating process simply. Due to micro parts' fabrication, such technologies need the control of XYZ stages with high precision, the design of optical devices to maintain micron spot sizes of laser beam and the control technology of laser focus. The developed laser manufacturing process for laser micromachining is that, after extracting coordinates of shape data from CAD model data, a beam path considering manufacturing features of laser beam is created by using genetic algorithm. This generated manufacturing process is sent to stage controller. In order to improve the surface quality of micro parts, we have carried out experiments on iteration manufacturing and beam step-over by using a minimum focus size. Moreover, we have fabricated a micro-channel through the developed laser micromachining technology and verified it through the results.