• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.7
• /
• pp.557-564
• /
• 1998

A low loss x-cut $LiNbO_3$optical waveguide was fabricated by Yi in-diffusion, and the properties of guided-mode and the total insertion loss of the pigtailed waveguide with polarization maintaining fiber(PMF) were measured at optical wavelength 1550nm. for forming the waveguides, the parameters of diffusion, Ti thickness, waveguide line-width, length, diffusion temperature, time and atmosphere were set $1400{\AA}$, $8{\mu}m$, 3.3cm, $1050^{\circ}C$, 8 hours and wet bubbled oxygen, respectively. And then after the polishing and piatailing, it showed that the total insertion loss was -4.1dB for TM mode, -5.5dB for TE mode, and mode size, that is, the horizontal/ vertical size were $13.8{\mu}m/18{\mu}m$ for TM mode, $9.6{\mu}m/6.5{\mu}m$ for TE mode.

• Nuclear Engineering and Technology
• /
• v.49 no.4
• /
• pp.865-872
• /
• 2017

For more than 10 years, the laser process has been studied for dismantling work; however, relatively few research works have addressed the effect of high-power fiber laser cutting for thick sections. Since in the nuclear sector, a significant quantity of thick material is required to be cut, this study aims to improve the reliability of laser cutting for such work and indicates guidelines to optimize the cutting procedure, in particular, nozzle combinations (standoff distance and focus position), to minimize waste material. The results obtained show the performance levels that can be reached with 10 kW fiber lasers, using which it is possible to obtain narrower kerfs than those found in published results obtained with other lasers. Nonetheless, fiber lasers appear to show the same effects as those of $CO_2$ and ND:YAG lasers. Thus, the main factor that affects the kerf width is the focal position, which means that minimum laser spot diameters are advised for smaller kerf widths.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.3
• /
• pp.262-268
• /
• 2014

This research introduces the structural design and the validation results of the flexible high speed coupling for 2MW class wind turbine which transmit and cut off torque between gear box and generator. The high speed coupling requires electrical insulation to prevent electrical surface damages on gear box. Therefore glass fiber reinforced plastics is applied to absorb the vibration and deformation of power train and to transmit required torque. Finite element analysis was performed to optimize the thickness and accumulation number of glass fiber reinforced plastics. Torque limiter which cut off the abnormal torque is designed in frictional disc type. The design of the coupling was validated with the performance test of prototype.

• Membrane Journal
• /
• v.23 no.1
• /
• pp.1-11
• /
• 2013

Poly(ether imide) (PEI)-poly(dimethylsioxane) (PDMS) composite membranes and their modules were prepared, which are capable of selective $CO_2$ separation from the mixture gas. The gas flow rate, concentration, recovery ratio of $H_2$ and removal ratio of $CO_2$ outflowing by stage-cut were characterized at $25^{\circ}C$ and the constant pressure. In addition, to increase the recovery ratio of $H_2$, one stage, two stage series connection, and three stages series + parallel connection tests were carried out. When the stage-cut was 0.32 for the three stages connection operation, the concentration $H_2$ of the produced gas and the recovery ratio of $H_2$ was 97% and 85%, respectively. And also the removal ratio of $CO_2$ was 90% was obtained and the recycled gas concentration was similar with that of the feed gases.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.5
• /
• pp.41-50
• /
• 2014

This study evaluated the bonding property of fiber and flexural behavior of fiber reinforced concrete. Amorphous steel fiber, hooked steel fiber and polyamide fiber was used for evaluation of bonding property and flexural behavior. As a result, the hooked steel fiber was pulled out from matrix when peak stress. However amorphous steel fiber occurred shear failure because bonding strength between fiber and matrix was higher than tensile strength of fiber. Polyamide fibers occurred significantly displacement to peak stress because of elongation of fiber. After that peak stress, fiber was cut off. Amorphous steel fiber reinforced concrete had a greater maximum flexural load compared with hooked steel fiber reinforced concrete because bonding performance between fiber and matrix was high and mixed population of fiber was many. However flexural stress was rapidly reduced in load-deflection curve because of shear failure of fiber. Flexural stress of hooked steel fiber reinforced concrete was slowly reduced because fiber was pulled out from the matrix. In the case of polyamide fiber reinforced concrete, flexural stress was rapidly lowered because of elongation of fiber. However flexural stress was increased again because of bonding property between polyamide fiber and matrix. The pull-out properties of the fiber and matrix has effect on the deformation capacity and flexural strength of fiber reinforced concrete.

• Journal of Bio-Environment Control
• /
• v.27 no.2
• /
• pp.158-165
• /
• 2018

The effects of different kinds of supplementary lighting or heating lamps on the yield, cut flower life, and leaf color of cut rose were compared and analyzed. For this purpose, light emitting diode lamp (LED), metal halide lamps (MH), and high-pressure sodium lamps (HPS) as the supplementary lamps, and carbon fiber infrared lamp (NCFI) were installed on hydroponic cultivation bed in a cut rose farm. The yield of cut flower rose and the number of marketable flowers were greatly increased in spring and autumn by HPS treatment, but not in winter. The length of flower stalk was longer than that of control in the spring but decreased in winter. It seemed likely that the shorter flower stalk in winter was due to the shortened period of vegetative growth compared to the control because flowering was promoted by supplementary lighting. Vase life was not different among treatments in the autumn when the lighting time was short, but in winter, it was prolonged to 3 more days by only HPS, compared with the control. Leaf color was significantly affected by light treatment in winter rather than autumn. Leaf color was darkened in all supplementary lamps (LED, MH, HPS) treatment, whereas NCFI was similar to the control in leaf color. In conclusion, HPS is considered to be a very good supplementary lamp because it increases the length of flower stalk and the yield and prolongs vase life in cut roses. Even though NCFI could function as a heating lamp radiating a lot of heat, it was considered that the role as a supplementary light is unsatisfactory because the number of marketable flowers decreases and the quality index of cut rose deteriorates by NCFI.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.03a
• /
• pp.409-416
• /
• 2002

In order to apply seismic isolators to the low-cost buildings, seismic isolators have to be low-cost and light. In this paper fiber reinforced strip form isolator in which the steel plates of conventional rubber bearing was replaced by fiber was proposed. The proposed fiber reinforced strip form isolator was designed, fabricated, cut and subjected to vertical test and harizontal test. Therefore fiber reinforced strip form isolator was to be shown valid in the view point of fabrication and application to desired size. The harizontal test and vertical test have shown that fiber reinforced strip form isolator could replace the rubber isolator. By these results, low-cost and light seismic isolator can be applied to the low-cost building. These fiber reinforced strip form isolator can be applied to the low-cost building.

• Composites Research
• /
• v.16 no.2
• /
• pp.26-32
• /
• 2003

Optical fibers, for splice, are stripped of their plastic coatings with a plastic stripper and cut off at the end. Therefore, stripped fibers often receive accidental damages and sustain small flaws or cracks. As a result, the breaking strength of a fiber splice made under normal conditions is reduced to about 0.4∼1 ㎏ on the average, nearly one-tenth of the fiber's strength. This makes it necessary to reinforce the splice. One of the most practical and reliable methods for optical fiber splicing is fusion splicing, comprising the steps of tripping the plastic coatings from the two fiber ends to be splice, placing the two bare fiber ends in an end-to-end position, and of fusion splicing, such as are fusion. Generally, steel bar (SB) sleeve is used to reinforce this fusion-splicing region. However, this type of sleeve has a critical defect to keep optical lose after bent by a sudden load. New type of composite spring (CS) sleeve is developed to make up for the weak points in the SB sleeve. This sleeve has an effect on restoration to the original state after eliminating the bending load. The optical spectrum analyzes results show the availability of reinforcement for the fusion splicing optical fiber using small diameter composite springs under the various loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.3
• /
• pp.347-352
• /
• 2010

Under harsh environments in which remote control is impossible, wire-guided control technology is effective for controlling distant underwater vehicles that serve mother ships in missions, such as exploration and installation. When the fiber is unwound from the spool, tension fluctuations occur in the fiber because of the relative velocity of the moving vehicles and unwinding velocity of the fiber. As a result, fiber cables exhibit complicated behaviors, become entangled, and may get cut. In this study, a spool-like design for winding tens of kilometers of fiber cables is proposed by analyzing cable winding. The unwinding performance of the designed spool is estimated by performing nonlinear dynamics analysis of the nonlinear behavior and tension fluctuations observed during the unwinding of the fiber.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.322-322
• /
• 2010

For boron doping on n-type silicon wafer, around $1,000^{\circ}C$ doping temperature is required, because of the relatively low solubility of boron in a crystalline silicon comparing to the phosphorus case. Boron doping by fiber laser annealing and lamp furnace heat treatment were carried out for the uniformly deposited p-a-Si:H layer. Since the uniformly deposited p-a-Si:H layer by cluster is highly needed to be doped with high temperature heat treatment. Amorphous silicon layer absorption range for fiber laser did not match well to be directly annealed. To improve the annealing effect, we introduce additional lamp furnace heat treatment. For p-a-Si:H layer with the ratio of $SiH_4:B_2H_6:H_2$=30:30:120, at $200^{\circ}C$, 50 W power, 0.2 Torr for 30 min. $20\;mm\;{\times}\;20\;mm$ size fiber laser cut wafers were activated by Q-switched fiber laser (1,064 nm) with different sets of power levels and periods, and for the lamp furnace annealing, $980^{\circ}C$ for 30 min heat treatment were implemented. To make the sheet resistance expectable and uniform as important processes for the $p^+$ layer on a polished n-type silicon wafer of (100) plane, the Q-switched fiber laser used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the fiber laser treatment showed the trade-offs between the lifetime and the sheet resistance as $100\;{\omega}/sq.$ and $11.8\;{\mu}s$ vs. $17\;{\omega}/sq.$ and $8.2\;{\mu}s$. Diode level device was made to confirm the electrical properties of these experimental results by measuring C-V(-F), I-V(-T) characteristics. Uniform and expectable boron heavy doped layers by fiber laser and lamp furnace are not only basic and essential conditions for the n-type crystalline silicon solar cell fabrication processes, but also the controllable doping concentration and depth can be established according to the deposition conditions of layers.