• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.940-947
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• 2006

A variety of actuators fur an implantable artificial heart have been studied. They, all, however, share the disadvantages of a complicated energy conversion mechanism and of the need to use bearings. A ferrofluidic actuator directly drives magnetic fluids by applying a magnetic field to these fluids; it does not require bearings. In this study, the feasibility of a ferrofluidic actuator for an implantable artificial heart was studied. An way of two Poles of ring solenoids was mounted near the acrylic tube $({\phi}\;7.4mm)$. A rubber sack (volume : $2m{\ell}$ was connected to both ends of the acrylic tube. The sack were encased in a rigid chamber that had inlet and outlet ports. The acrylic tube and the rubber sack were filled with water encased in a rigid chamber magnetic fluid and the iron cylinder were immersed in the water. Two experiment method was conducted. 1) distance between stoppers were 72mm and 2) distance between stoppers were 104mm. A stroke volume was stability and $0.96m{\ell}$ was obtained in the experiment 1 and $1.92m{\ell}$ in the experiment 2. The energy efficiency of Experiment method 2 is about five times than Experiment method 2. A magnetic fluid-driven blood pump could be feasible if the magnetic fluid with high magnetization (3 times yester than the current value) is developed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.686-686
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• 2013

Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. In addition to, there is a mechanical noise caused from movement of an actuator, electronically controlling a wastegate valve. It is called as valve rattle noise. The actuator is connected to a valve through a linkage. The noise occurs only if the valve is open, where the linkage is freely contact to neighbor structures without being constrained by any external forces. This condition allows impacts by the pulsation of exhaust gas, and the vibration from the impacts spreads out through turbine housing, causing the rattle noise. The noise is not in mechanical operating wastegate turbochargers because the linkage of an actuator is strongly connected by actuating force. For the electronic wastegate turbocharger, this paper proposed a test device to show the noise generating mechanism with a small vibration motor having an unbalanced shaft. It also shows how to reduce the noise - reduction of linkage clearances, inserting wave washers into a connection, and applying loose fitting in bushing embracing a valve lever to turbine housing.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.71-71
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• 2018

Sea pollution accidents have been occurred due to the increase of marine ship traffic. Oil spill from the hull hole induced by tanker collision results in the huge sea pollution. Proper and prompt reaction on such oil spill disaster is needed to minimize the damage. Thru-hull emergency wood plug is typically used to manually close small holes, while it is required to develop some mechanical devices for closing large holes in the hull due to huge fluid pressure. Accurate estimation of oil discharge and velocity from such holes are important to develop proper device to control hull hole damage. High resolution CFD modeling investigation on the configurations of hull hole of 7.5 m initial depth and 30 cm diameter, which was observed in the oil spill accident of the Hebei Sprit off the west coast of Korea in 2007, has been carried out to compute the oil spill velocity distribution in terms of flow depth. Friction loss due to the viscous flow and the discharge coefficient of crude oil with specific gravity SG = 0.85 and viscosity of $4-12cP(mPa{\cdot}s)$ at the temperature of $20^{\circ}C-100^{\circ}C$ are presented in terms of Reynolds number based on the results of high-resolution CFD modeling.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.203-211
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• 2021

Octacalcium phosphate(OCP, Ca₈H₂(PO₄)₆·5H₂O) is one of biodegradable calcium phosphate materials with osteoconductivity and biocompatibility. It has the advantage of rapid bone formation and resorption due to the property of stimulating stromal cells to differentiate into osteoblasts. However, if OCP is inserted in body, it is immediately decomposed without maintaining of its shape as scaffolds due to their weak cohesive force between powder. On the other hand, hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂), which has a crystal structure similar to that of OCP, remains in the body without decomposition until the bone defect is restored. In this study, the degradation behavior of OCP/HA disc with different amount of HA in SBF (simulated body fluid) solution was characterized in terms of the weight loss, pH variation and microstructure change with immersion duration in SBF solution. As a result, the OCP/HA disc was not quickly decomposed and maintained its own shape for 2 weeks regardless of HA content. In particular, the surface of 40HA specimen was uniformly dissolved and then CDHA (calcium deficient hydroxyapatite) phase were formed onto the surface of disc after 7 days in SBF solution. It would be suggested that the 40HA specimen would be suitable candidate material as the scaffolds for the restoration of bone defect.

• Industry Promotion Research
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• v.4 no.1
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• pp.11-20
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• 2019

This study relates to a fixing device for gas piping installed in a building such as an apartment or a building. The gas piping is fixed to the inside of the housing so as to buffer the gas piping in all directions, thereby relieving vibration caused by an earthquake or an impact, Disclosed is an earthquake-proof fixing device for a gas pipeline that can minimize damages caused by damage to an earthquake and a gas pipeline by preventing damage and breakage. An apparatus for fixing a gas pipe to a bracket provided on a wall or a wall of a building, the apparatus comprising: a housing coupled to a wall or a bracket and coupled to the inside of the housing; a gas pipe penetrating through the housing to fix the gas pipe; The first plate spring includes a first plate spring formed with a plurality of concave-convex portions that are elastically supported in four directions. The first plate spring is screwed to the front surface or the rear surface of the housing. The lower plate is coupled to one end and the other end, And a pair of first adjusting screws for adjusting the elastic force of the spring. Through this study, damage and damage of gas piping due to earthquake or impact can be minimized.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.467-472
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• 2011

This study investigated illite/polypropylene (PP) composite filament formation via melt-spinning and evaluated their physical properties to prepare functional fibers using natural materials. When composite filaments were formed, the composite filaments exhibited smaller fiber diameters compared to that of neat PP filament because of the lubricant effect of illite induced by its layered structure. Moreover, fluorination effect increased interfacial affinity and dispersion in the polymer, resulting in smaller diameter of fluorinated illite/PP composite filament, which was 2/3 of the neat PP filament diameter. Addition of raw and fluorinated illite improved thermal stability of illite/PP composite filament. Raw illite/PP composite filament cannot be used for a practical application, because it broke during drawing process, whereas the fluorinated illite/PP composite filament can be used for a practical application, because it exhibited similar tensile strength of the neat PP filament and 50% increased modulus. Even with improved illite/PP interfacial affinity and illite dispersion in the polymer, illite/PP composite filament formed microcomposite, because non-expandable illite had strongly bound layers, resulting in only a little illite exfoliation and PP intercalation into illite.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.398-406
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• 2022

The outer membrane of Gram-negative bacteria is the outermost layer of cellular environment in which numerous biophysical and biochemical processes are in action sustaining viability. Advances in cell engineering enable modification of bacterial genetic information that subsequently alters membrane physiology to adapt bacteria to specific purposes. Surface display of a functional molecule on the outer membranes is one of strategies that directs host cells to respond to a specific extracellular matter or stimulus. While intracellular expression of a functional peptide or protein fused to a membrane-anchoring motif is commonly practiced for surface display, the method is not readily applicable to exogenous or large proteins inexpressible in bacteria. Chemical conjugation at reactive groups naturally occurring on the membrane might be an alternative, but often compromises fitness due to non-specific modification of essential components. Herein, we demonstrated two distinct approaches that enable site-specific decoration of the outer membrane with a fluorescent agent in Escherichia coli. An unnatural amino acid genetically incorporated in a surface-exposed peptide could act as a chemoselective handle for bioorthogonal dye labeling. A surface-displayed α-helical domain originating from a part of a selected heterodimeric coiled-coil complex could recruit and anchor a green fluorescent protein tagged with a complementary α-helical domain to the membrane surface in a site- and hetero-specific manner. These methods hold a promise as on-demand tools to confer new functionalities on the bacterial membranes.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.7-15
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• 2023

Recently, as interest in air quality in vehicles increases, the use of fine dust detection sensors for air quality measurement is becoming common. An axial-flow fan is inserted in the fine dust sensor installed in the air conditioning system in the vehicle to prevent dust from sinking directly on the sensor. When the sensor operates, the flow noise caused by the rotation of the axial-flow fan acts as a major noise source of the fine dust sensor. flow noise is recognized as one of the product competitiveness of fine dust sensors. In this study, the noise was gradually reduced at the same flow rate by improving the flow performance of the small axial flow fan. First, a virtual fan performance tester consisting of about 20 million grids was developed to analyze the aerodynamic performance of the target small axial-flow fan. In addition, the flow field was simulated by using compressible Large Eddy Simulation for direct computation of flow noise as well as high-accurate prediction of flow rate. The validity of numerical method are confirmed through the comparison of predicted results with experimental ones. After the effects of pitch angle on flow performance were analyzed using the verified numerical method, the pitch angle was determined to maximize the flow rate. It was found that the flow rate was increased by 8.1 % and noise was reduced by 0.8 dBA when the axial-flow fan with the optimum pitch angle was used.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.535-549
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• 1999

The Purposes of this study were to investigate the initial tissue changes on the teeth and surrounding tissues under contraction and intrusive force by contraction UTA. A control and experimental dogs, 10-months in age, were studied. Contraction and intrusive force(60gm) were applied at upper four incisors by contraction UTA. Experimental dogs were sacrificed at 2 weeks and 4 weeks after force application, respectively. In this study, 2 experimental groups were designed by the duration of force applied(E1, E2). The specimens were taken around the upper first and second incisor in each groups and were prepared for the H-E and MT stain for light microscopic observation. From the results of the study, the following conclusions may be drown. : 1. In control group, the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third, oblique in middle third and apical third. In alveolar bond, smooth appearance was shown with osteoblast. 2. In experimental group 1, in proportion to force was concentrated at labial middle third and apical third of root of the upper first and second incisors, root of these tooth tipped labially and intruded at a time. 3. In experimental group 2, periodontal ligament width and arrangement was similar to control and observed strong calcified response at the labial middle third of root. But, alveolar bond resorption and cementum resorption were as before seen at labial middle third and apical third of root that force was concentrated.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.497-506
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• 1998

The expression in Escherichia coli of a cloned insecticidal protein (ICP) gene from Bacillus thuringiensis var. kurstaki HD1 in pHLN1-80 (+) and pHLN2-80(-) plasmids was investigated through deletions in promoters, transcription start point, and termination region. Six recombinant plasmids were constructed in an attempt to analyze the overexpression of the ICP in relations to its gene structure. The amounts of ICP produced from the recombinants were measured by SDS-PAGE and confirmed by Western blot analysis. One clone was not overexpressed which having only -80 bp (contained BtI promoter) part of the ICP gene promoter (without Plac promoter), the right-oriented ICP gene and the termination region. Removal of 350 bp from upstream region of the Plac of the clone pHLN2-80 (-) resulted in overexpression of the ICP. One clone was not overexpressed in which the clone consisted of -72 bp part of the ICP promoter without the transcription start point and the transcriptional termination region, and having the right-oriented ICP gene sequence. One clone consisting of the inverted ICP gene sequence, the -72 bp ICP gene promoter, and without the termination region caused overexpression. One clone which consisted of the inverted ICP gene, the -72 bp ICP gene promoter and the termination sequence was overexpressed. These results indicated that the Plac promoter, transcription termination region, the inverted ICP gene insertion, and the -80 bp or -72 bp part of the ICP gene promoters were concerned in the overexpression of the ICP gene in the recombinant plasmid, and also the overexpression mechanism might result from the disruption of the transcription-suppressing regions in the promoter regions.