• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.185-194
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• 2012

A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.427-430
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• 2001

We prepared 10cm-diameter Si(100)/500 $\AA$-Si$_3$N$_4$/Si(100) wafer Pairs adopting 500 $\AA$ -thick Si$_3$N$_4$layer as insulating layer between single crystal Si wafers. Si3N, is superior to conventional SiO$_2$ in insulating. We premated a p-type(100) Si wafer and 500 $\AA$ -thick LPCVD Si$_3$N$_4$∥Si (100) wafer in a class 100 clean room. The cremated wafers are separated in two groups. One group is treated to have hydrophobic surface and the other to have hydrophilic. We employed a FLA(fast linear annealing) bonder to enhance the bond strength of cremated wafers at the scan velocity of 0.1mm/sec with varying the heat input at the range of 400~1125W. We measured bonded area using a infrared camera and bonding strength by the razor blade crack opening method. We used high resolution transmission electron microscopy(HRTEM) to probe cross sectional view of bonded wafers. The bonded area of two groups was about 75%. The bonding strength of samples which have hydrophobic surface increased with heat input up to 1577mJ/$m^2$ However, bonding strength of samples which have hydrophilic surface was above 2000mJ/$m^2$regardless of heat input. The HRTEM results showed that the hydrophilic samples have about 25 $\AA$ -thick SiO layer between Si and Si$_3$N$_4$/Si and that maybe lead to increase of bonding strength.

• Korean Journal of Medicinal Crop Science
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• v.13 no.3
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• pp.122-125
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• 2005

‘Johyun’ was a new adlay variety which was developed from three way crosses of (Suwon-6xOkayama)x UCN300-25 at the Northern Agricultural Research Station, Gyeonggi Province ARES. This variety had purple sheath and green leaf blade in primitive growth stage and green leaf and culm in heading stage. Colors of pistil and seed coat were milky-white and dark-brown, respectively. Plant height of Johyun was 179 cm and shortened 22 cm less than Yulmoo-1 which was tested by check variety. Johyun shortened 8 days of heading date and 15 days of ripening date compared with Yulmoo-1. Yield of Johyun was 320 kg/10a of hulled grains in three regional yield trials and 18% higher than Yulmoo-1. This variety was adaptable to single cropping in central and northern region of Korea.

• Journal of Acupuncture Research
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• v.15 no.2
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• pp.105-116
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• 1998

Purpose In this study, We observed the recovery process in the ability to move in the hind limbs of the rats whose spinal cord injuries were treated by Radix acouniti(RA). The purpose of this study is to see the effects of Radix acouniti(RA) water extract on the contraction of rat's spinal cord injury. Procedure First, the rats were subjected to hemisectional spinal cord injuries by a scalpel blade. Those rats, then, were divided into three groups: Sham operated rats group and the experimental group, which received the Radix acouniti(RA) water extract, and the control group, which had no treatment. Their recovery in the ability to walk was observed by the Open Field Test (OFT) for 14 days after the injuries. Method The OFT was applied at four points: the hip, knee, ankle joint, and the tail. Each joint was given a movement rating of from 0 to 3, depending on the amount of movement. A movement rating of 0 designates no movement, a 1 designates slight movement, a 2 designates increased movement, and a 3 designates active movement. Slight movement is defined as a joint displaying less than or equal to 30% of that joint range, increased movement is displaying less than or equal to 60% of that joint's range, and active movement is greater than or equal to 90% of that joint's range. Tail movement is also graded on a scale of 0 to 3. A rating of 0 indicates that the tail is down 100% of the time, one of 1 indicates that the tail is down more than 10%, one of 2 shows that the tail is down less than 50% but more than 10% of the time, and one of 3 shows that the tail is down less than 10% of the time. All four ratings were added together and then averaged to arrive at a single score. Results The sham group which did not go through spinal cord injuries showed near normal results on all 3 joints and tail from right after the operation, which one would expect. The RA oral application group showed more effective recovery of movememt function than the control group around 4 days after the spinal cord injuries. However, after 14 days, both groups displayed almost the same degree of movement recovery. The results of this study are summarized as follows: 1. After 14days the spinal cord injuries, movement was recovered in sham operated group, control group, and experimented group in the hip, the knee, the tail and then the ankle of rats, in that order. 2. Around 7 days after the spinal cord injuries, the experimental group proved the effectiveness of the therapy in terms of movement recovery. 3. The level of ALT, ALP, AST in RA treated group was slightly increased. 4. The level of BUN and creatinine in RA treated group was slightly increased. The above results indicate that RA therapy at an early stage can bring about better movement recovery in patients with spinal cord injuries from traffic accidents or industrial disasters. But there is apparent side effect of RA on clinical, therefore the study on this should be continued.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.463-463
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• 2014

Dye-sensitized solar cells (DSSCs) have generated a strong interest in the development of solid-state devices owing to their low cost and simple preparation procedures. Effort has been devoted to the study of electrolytes that allow light-to-electrical power conversion for DSSC applications. Several attempts have been made to substitute the liquid electrolyte in the original solar cells by using (2,2',7,7'-tetrakis (N,N-di-p-methoxyphenylamine)-9-9'-spirobi-fluorene (spiro-OMeTAD) that act as hole conductor [1]. Although efficiencies above 3% have been reached by several groups, here the major challenging is limited photoelectrode thickness ($2{\mu}m$), which is very low due to electron diffusion length (Ln) for spiro-OMeTAD ($4.4{\mu}m$) [2]. In principle, the $TiO_2$ layer can be thicker than had been thought previously. This has important implications for the design of high-efficiency solid-state DSSCs. In the present study, we have fabricated 3-D Transparent Conducting Oxide (TCO) by growing tin-doped indium oxide (ITO) nanowire (NWs) arrays via a vapor transport method [3] and mesoporous $TiO_2$ nanoparticle (NP)-based photoelectrodes were prepared using doctor blade method. Finally optimized light-harvesting solid-state DSSCs is made using 3-D TCO where electron life time is controlled the recombination rate through fast charge collection and also ITO NWs length can be controlled in the range of over $2{\mu}m$ and has been characterized using field emission scanning electron microscopy (FE-SEM). Structural analyses by high-resolution transmission electron microscopy (HRTEM) and X-Ray diffraction (XRD) results reveal that the ITO NWs formed single crystal oriented [100] direction. Also to compare the charge collection properties of conventional NPs based solid-state DSSCs with ITO NWs based solid-state DSSCs, we have studied intensity modulated photovoltage spectroscopy (IMVS), intensity modulated photocurrent spectroscopy (IMPS) and transient open circuit voltages. As a result, above $4{\mu}m$ thick ITO NWs based photoelectrodes with Z907 dye shown the best performing device, exhibiting a short-circuit current density of 7.21 mA cm-2 under simulated solar emission of 100 mW cm-2 associated with an overall power conversion efficiency of 2.80 %. Finally, we achieved the efficiency of 7.5% by applying a CH3NH3PbI3 perovskite sensitizer.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.261-271
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• 1993

Functionally Gradient Materials(FGM) of 4.5Pb($Ni_{1/3}Nb_{2/3})O_3$-55PZT and PLZT(lO/70 /30, 11/60/40) were prepared. Its dielectric and piezoelectric strain properties were investigated. The FGM were pressed into A/B/ A configuration using two kinds of films, one layer(A) was eliminated from FGM by polishing after sintering at $l250^{\circ}C$, 2 hrs. The acrylic binder system was successfully applied for crack free film through doctor blade method. The thickness of gradent layer in FGM was about 30${\mu}$m. Dielectric properties of FGM show the average value of each side layer. The strain-electric field characteristics of FGM were significantly improved comparison with the other single compositions. The prepared FGM piezoelectric actuator shows about 3${\mu}$m/IOOV displacement.

• Advances in aircraft and spacecraft science
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• v.9 no.5
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• pp.415-431
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• 2022

Secondary flows have a huge impact on losses generation in modern low pressure gas turbines (LPTs). At design point, the interaction of the blade profile with the end-wall boundary layer is responsible for up to 40% of total losses. Therefore, predicting accurately the end-wall flow field in a LPT is extremely important in the industrial design phase. Since the inlet boundary layer profile is one of the factors which most affects the evolution of secondary flows, the first main objective of the present work is to investigate the impact of two different inlet conditions on the end-wall flow field of the T106A, a well known LPT cascade. The first condition, labeled in the paper as C1, is represented by uniform conditions at the inlet plane and the second, C2, by a flow characterized by a defined inlet boundary layer profile. The code used for the simulations is based on the Discontinuous Galerkin (DG) formulation and solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the Spalart Allmaras turbulence model. Secondly, this work aims at estimating the influence of viscosity and turbulence on the T106A end-wall flow field. In order to do so, RANS results are compared with those obtained from an inviscid simulation with a prescribed inlet total pressure profile, which mimics a boundary layer. A comparison between C1 and C2 results highlights an influence of secondary flows on the flow field up to a significant distance from the end-wall. In particular, the C2 end-wall flow field appears to be characterized by greater over turning and under turning angles and higher total pressure losses. Furthermore, the C2 simulated flow field shows good agreement with experimental and numerical data available in literature. The C2 and inviscid Euler computed flow fields, although globally comparable, present evident differences. The cascade passage simulated with inviscid flow is mainly dominated by a single large and homogeneous vortex structure, less stretched in the spanwise direction and closer to the end-wall than vortical structures computed by compressible flow simulation. It is reasonable, then, asserting that for the chosen test case a great part of the secondary flows details is strongly dependent on viscous phenomena and turbulence.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.334-342
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• 2016

In order to evaluate the modified installation methods of roof ventilation devices, derived from the previous experiment ('investigation into the optimum capacity of roof ventilation devices and their deployment'), the conventional and modified (improved) roof ventilation systems were installed in the single-span plastic greenhouse for growing oriental melons. The roof vents ($60{\varphi}$) and roof fans (maximum air capacity of $38m^3/min$) were installed in the spacing of 15m (FT, modified 'side vent+roof fan' ventilation) and 6m (TT, modified 'side vent+roof vent' ventilation) respectively on the roof of greenhouses for the modified roof ventilation treatments, and 20m (FC, conventional 'side vent+roof fan' ventilation) and 8m (TC, conventional 'side vent+roof vent' ventilation) for the conventional ones. The stem diameter, leaf blade lengh, petiole length, and leaf width were lower in the FT and TT treatments than those in the conventional treatments, FC and TC. Although the fruit weight and total yields were slightly lower in the FT and TT treatments, the marketable fruit ratio (%) were higher, as a result of increased fruiting ratio (%) in these treatments, than those of FC and TC. The marketable yields (kg/10a) in the FT and TT treatments were 8,391 kg/10a and 7,283 kg/10a, which were respectively 661 kg/10a and 487 kg/10a higher than those in the treatments of FC and TC. The modified installation methods of roof fan resulted in production of more female flowers and lower fruit drop ratio (%) compared to conventional meathods. In the treatment of the conventional ventilation with roof vent, the fruit weight, fruit length & width, and flesh thickness were higher than in other treatments, but there were no significant differences in the fruit width and flesh thickness among the treatments.

• Korean Journal of Environmental Biology
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• v.38 no.3
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• pp.404-415
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• 2020

We investigated the seasonal variations in growth and physiological responses of the kelp species Ecklonia cava to different nitrogen sources to establish indoor culture conditions for mass production. Ecklonia cava was cultivated for 10 days in 16 combinations of seawater temperatures (15, 17, 21, and 25℃) and different nitrogen sources (control; NH-NH₄⁺ 100 μM; NO-NO₃^- 100 μM; and NHNO-NH₄⁺ 50 μM+NO₃^- 50 μM). The growth and growth rate of the blade were affected by temperature. The mean fresh weight and area-based daily growth rate were the highest (5.8±0.5 and 6.6±0.5% day^-1, respectively) at 15℃ and the lowest (2.2±0.2 and 3.0±0.3% day^-1, respectively) at 25℃. The daily growth rate was the highest in the NH and NO treatments and lowest in the control. The nitrate reductase activity of E. cava varied with water temperature (season). The highest activity was in the control (1.32±0.10 μmol NO₂^- g^-1 dry weight h^-1) and the lowest was in the NH treatment (0.25±0.02 μmol NO₂^- g^-1 dry weight h^-1). The photosynthetic pigment concentrations reached a maximum value in the NHNO treatment and a minimum value in the control. These results showed that water temperature played an important role in the cultivation of E. cava and that a single supply of NH₄⁺ or NO₃^- may induce the accelerated growth of E. cava. The growth and physiological responses of E. cava to different nitrogen sources during each season provide valuable information for determining the optimal nitrogen source in E. cava cultivation under indoor conditions.

• Applied Microscopy
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• v.39 no.1
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• pp.57-64
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• 2009

The trapping leaves of Drosera capture insects by secreting sticky mucilage from numerous glandular trichomes (GTs) that are developed on the leaf epidermis. The present study examines and compares the structural features of those trichomes in Drosera binata and D. pygmy with the use of light and electron microscopy. The study focuses primarily on the development and differentiation pattern of the GTs during growth. Upon examination, the upper and lower epidermis were readily distinguishable by the features of GTs in developing leaves. In particular, the GTs were dense in the upper epidermis and along the leaf margin. In D. binata, the capitate GTs with elongated stalk and sessile peltate GTs were found most commonly, whereas only capitate GTs with varying degrees of the stalk length were observed in D. pygmy. Up to ca. $2.2{\sim}3.4\;mm$ long capitate GTs were seen in the leaf margins of D. binata and ca. $3.7{\sim}4.2\;mm$ long GTs having racket-like head with adaxial hemispheric structures, otherwise known as tentacles, were noted in the leaf margin of D. pygmy. The peltate GTs were found to be distributed in the lower epidermis of D. binata. In both species, head cells were dense with cytoplasm containing high numbers of Golgi bodies, ER, mitochondria and small vesicles. Secretory materials accumulated within numerous small vacuoles, then fused together to form a single large vacuole, which serves as a secretory cavity. Flection movement of the marginal GTs and leaf blade GTs, and increased mucilage secretion from the head cells upon contact with prey during the capturing process are considered to be major factors in their active insectivorous mechanism. The findings of this study will be useful in comparisons to similar findings in other species that form adhesive trapping leaves, such as Drosophyllum or Pinguicula., further contributing a better understanding of the function and structure of the trapping leaves of carnivorous plants.