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In this study, we have used computational fluid dynamics to investigate the blood flow in the stenosed blood vessels. The numerical simulation using commercial software ADINA 8.6 were solved about the stenosed blood vessel according to the percent of stenosis and Reynolds number. The blood flow in the normal and stenosed blood vessel was grasped for the validity of the model. The characteristic of the pulsatile flow changed through the steady state flow and analysis of the pulsatile flow according to the time was grasped. The computational model with the characteristics of the fluid-structure interaction is introduced to investigate the wall shear stress, pressure distribution and axial flow velocity. The results show that axial flow velocity and wall shear stress in the region of stenosis was increased by increasing percent of stenosis and Reynolds number. Also, we can know that in the stenosed blood vessel the possibility of the generation of the aneurysm was increased by increasing Reynolds number and percent of stenosis.

This investigation was to identify the electrochemical corrosion protection conditions to minimize the cavitation damage by generating hydrogen gas with the means of hydrogen overvoltage before the impact pressure of the cavity is transferred to the surface. The hybrid potentiostatic test method is designed to evaluate a complexed cavitation and electrochemical characteristic for ALBC3 alloy that is diverse and its broad applications fields in marine industry. The surface observation showed that neither the cavitation damage nor the electrochemical damage by the hydrogen gas generation occurred in the potential of -2.6 V under the cavitation environment. In the potentiostatic experiments under the cavitation environment, the cavities were reflected or cancelled out by the collision of the cavities with the hydrogen gas generated by the hydrogen overvoltage.

Steel applied in ocean environment is exposed to corrosion and cavitation and is subject to increasing damages. To prevent this, anti-corrosion thermal spray coating technique is widely used. The low-temperature thermal spray coating was performed with 85%Al–14.5%Zn–0.5%Zr for ship materials and various sealing materials were applied to improve its durability, and the electrochemical behavior and cavitation characteristics were observed. The results show that the sealing improves all the properties of the materials. Hybrid ceramic and fluoro-silicon sealing materials show good electrochemical characteristics, and the fluoro-silicon sealing material shows the best anti-cavitation characteristics.

The optimum corrosion protection potentials were examined for 5052-O Al alloy, which is mainly used in ships. Various electrochemical experiments were carried out and the surface morphologies of specimens were observed by scanning electron microscopy (SEM) in order to determine the optimum corrosion protection potential to overcome pitting, corrosion, stress corrosion cracking (SCC), and hydrogen embrittlement in sea water. An optimum protection potential range of −1.3 V to −0.7 V was determined under the application of an impressed current cathodic protection (ICCP) system. The low current densities were shown in the range of −1.3 V to −0.7 V in the electrochemical experiments and good specimen surface morphologies were observed after potentiostatic experiment.

Optical-fiber electronic speckle pattern interferometry (ESPI) is a non-contact, non-destructive examination technique with the advantages of rapid measurement, high accuracy, and full-field measurement. The optical-fiber ESPI system used in this study was compact and portable with the advantages of easy set-up and signal acquisition. By suitably configuring the optical-fiber ESPI system, producing an image signal in a charge-coupled device camera, and periodically modulating beam phases, we obtained phase information from the speckle pattern using a four-step phase shifting algorithm. Moreover, we compared the actual defect size with that of interference fringes which appeared on a screen after calculating the pixel value according to the distance between the object and the CCD camera. Conventional methods of measuring defects are time-consuming and resource-intensive because the estimated values are relative. However, our simple method could quantitatively estimate the defect length by carrying out numerical analysis for obtaining values on the X-axis in a line profile. The results showed reliable values for average error rates and a decrease in the error rate with increasing defect length or pressure.

We report the synthesis, cytotoxicity, and phenotypic analysis of oxazole and thiazole containing fragments. Evaluating the optimal size and heterocycle for growth inhibition and apoptosis showed that activity required at least two thiazoles sequentially connected. This is the first detailed comparison of biological activity between multi-heterocyclic containing fragments.

Comparing a solution phase route to a solid phase route in the synthesis of the cytotoxic natural product urukthapelstatin A (Ustat A) confirmed that a solid phase method is superior. The solution phase approach was tedious and involved cyclization of a ridged heterocyclic precursor, while solid phase allowed the rapid generation of a flexible linear peptide. Cyclization of the linear peptide was facile and subsequent generation of three oxazoles located within the structure of Ustat A proved relatively straightforward. Given the ease with which the oxazole Ustat A precursor is formed via our solid phase approach, this route is amenable to rapid analog synthesis.

Due to the good corrosion resistance and machinability, copper alloy is commonly employed for shipbuilding, hydroelectric power and tidal power industries. The Cu alloy, however, has poor durability, and the seawater application at fast flow condition becomes vulnerable to cavitation damage leading to economic loss and risking safety. The HVOF(High Velocity Oxygen Fuel) thermal spray coating with WC-10Co4Cr were therefore introduced as a replacement for chromium or ceramic to minimize the cavitation damage and secure durablility under high-velocity and high-pressure fluid flow. Cavitation test was conducted in seawater at and with an amplitude of on HVOF WC-10Co4Cr coatings produced by thermal spray. The cavitation at and exposed the substrate in 12.5 hours and in 10 hours, respectively. Starting from 5 hours of cavitation, the coating layer continued to show damage by higher than 160% over time when the temperature of seawater was elevated from to . Under cavitation environment, although WC-10Co4Cr has good wear resistance and durability, increase in temperature may accelerate the damage rate of the coating layer mainly due to cavitation damage.

In general, aluminum alloys forms the passive film(, ) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

This investigation evaluated the effect of cavitation condition on electrochemical characteristics of 304 stainless steel, which is widely used for marine environment. The cavitation test with time were conducted on 304 stainless steel in seawater solution. Surface morphologies of specimen were observed by scanning electron microscope (SEM) and 3D microscope. Pitting depth, weight loss and damage rate were analyzed after each cavitation experiment. The surface damage was more severe as the current density increased. A dramatical increase in the damage depth and weight loss was observed after 7 hours of cavitation experiment.

The hull of a fast sailing aluminium ship are generally prone to erosion owing to the impact of seawater. At this time, synergistic effects of the erosion and the corrosion by aggressive ions such as chlorides tend to aggravate the damage. There have been various attempts, including selection of erosion-resistant materials, cathodic protection and addition of corrosion inhibitors, to overcome damage by erosion or corrosion under marine environments. These approaches, however, have limits on identifying the damage mechanism clearly, because they depend on analogical interpretation by correlating two damage behaviors after the individual studies are assessed. In this research, it was devised a hybrid testing apparatus that integrates electrochemical corrosion test and cavitation test, and thus the erosion-corrosion behavior by cavitation was investigated more reliably. As a result, the slightest damage was observed at the potentials between -1.6 V and -1.5 V. This is considered to be due to a reflection or counterbalancing effect caused by collision of the cavitation cavities and the hydrogen gas formed by activation polarization.

Among Al alloys, particularly 5000 series Al–Mg and 6000 series Al–Mg–Si often used as marine materials have excellent corrosion resistance, low melting point, and thereby showing recycling availability when compared to other metals. Variety experiments were conducted to select the most suitable material for marine environments. All electrochemical experiments were conducted in natural seawater. The corrosion test was performed in many methods such as anodic/cathodic polarization and Tafel analysis using multi-channel potentio/galvanostat WMPG–1000. As results, anodic and cathodic polarization behaviors indicate the characteristics of passive state and concentration polarization by reduction reaction in dissolved oxygen, which shows excellent electrochemical behaviors. Tafel analysis results show no significant difference but 5052-O alloy of various alloy materials indicates the lowest corrosion current density. Therefore, 5052-O Al alloy presents most anti-corrosion material in marine environment.

To improve the durability of underwater rotating products, the corrosion characteristics in harsh marine environment were evaluated through various electrochemical experiments on the Al 2 O 3 –3TiO 2 and CoNiCrAlY coating layers by atmospheric pressure plasma spray coating process. By evaluating the corrosion resistance of these materials, their applicability to environmentally friendly power generation equipment such as blades of tidal current turbines was examined. According to the Tafel analysis for micro-areas including the coating layer, the coating/metal interlayer and the base metal, the Al 2 O 3 –3TiO 2 coating layer and the CoNiCrAlY coating layer show markedly lower corrosion current density than the base metal. The corrosion current density of the CoNiCrAlY coating layer (9.75316×10 −8 A/cm 2 ) is about 1.6 times more than that of the Al 2 O 3 –3TiO 2 coating layer (6.13139×10 −8 A/cm 2 ).

Among the environmentally friendly marine energies, tidal current power plants require low cost because they do not need to construct a large dam. Tidal power is particularly reliable energy source because the power generation capacity is predictable regardless of weather or season. Composite materials or stainless steel have been used as materials of blades for current power plant. However, their strength and welding performance generated many problems in field application. Copper alloys with excellent cavitation resistance and corrosion resistance were applied as blade materials to improve the durability of copper alloys. They were coated with WC–27NiCr and WC–10Co4Cr using the high velocity oxy-fuel (HVOF) method. The metal spray coating technology has the advantage in terms of the selection of materials for cost effectiveness and environmental effects of corrosion because the properties of the coat layer can be controlled intentionally. Coating with WC–27NiCr and WC–10Co4Cr by HVOF, WC–27NiCr shows better corrosion resistance overall. The reason for this seems to be that corrosion resistance improves and a stable passive film forms due to the effects of Ni and Cr.

Copper alloys are widely used for casting materials including ship`s propellers and pump impellers as they provide high corrosion resistance. In addition, the demand for these alloys is increasing with rapid growth of offshore structures and exploitation of various substitute energy sources. However, they require regular maintenance because of erosion and cavitation damages induced by exposure to marine environment at high speed flows for a long period of time. Water cavitation peening have received attention as one of surface modifications for durability improvement of the copper alloys. This is a environment friendly technology without influence of heat and easily applicable to casting materials. In this research, water cavitation peening was employed in distilled water for copper alloy castings as a function of time and evaluation of corrosion resistance was followed in seawater for the modified surface by using electrochemical methods. The result suggests that the water cavitation peening for 2 minutes was found to be the optimal peening parameter in terms of durability and corrosion resistance.

Cu alloy is widely used for marine applications due to its excellent ductility and high resistance for corrosion as wells as cavitation. However, long term exposure of the material to marine environments may result in damages caused by cavitation and corrosion. Water cavitation peening has been introduced in order to improve resistance of Cu alloy to corrosion and cavitation. The technology induces compressive residual stress onto the surface, and thus enhances the fatigue strength and life. In this study, the characteristics of the material were investigated by using water cavitaiton peening technique, and results showed that 2minutes of water cavitation peening indicated the considerable improvement in hardness. On the other hand, over 10 minutes of water cavitation peening accelerated damages to the surface. In the case of ALBC3, water cavitation peening in the range of 2 to 10 minutes has shown the excellent durability and corrosion resistance while minimizing surface damages.

Division of Marine Engineering, Mokpo National Maritime University, Mokpo, 530-729, KoreaDepartment of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, 464-8601, Japan요 약 : 최근 FRP 선박의 폐선 처리문제, 환경 규제의 강화, 자원 재활용 등의 관점에서 소형 알루미늄 합금 선박의 건조가 증가하는 추세이다. 그러나 알루미늄은 가볍기 때문에 해양에서 고속으로 운행 가능한 알루미늄 선박은 캐비테이션이 발생되어 기포붕괴에 따른 큰 충격압력에 의해 캐비테이션 침식이 일어남으로서 재료의 수명에 있어 문제점을 드러내고 있다. 따라서 본 연구에서는 캐비테이션에 의한 손상을 방지하여 내구 수명을 연장시키기 위한 방법으로 워터 캐비테이션 피닝 기술을 선박용 알루미늄 합금에 적용하였다. 이를 위하여 워터 캐비테이션 피닝을 실시하여 내캐비테이션 특성이 가장 우수한 적용 시간을 규명하였다. 선박용 알루미늄 합금 5456-H116, 5083-H321 그리고 5052-O는 워터캐비테이션 피닝을 실시함으로써 내캐비테이션 특성이 워터 캐비테이션 피닝을 하지 않은 시편보다 무게감소량이 각각 42.11%, 50.0% 그리고 25.7% 개선되었다.핵심용어 : 알루미늄 선박, 워터 캐비테이션 피닝, 캐비테이션, 무게감소량, 5000 계열 알루미늄 합금Abstract : Recently, the construction of the small Al alloy ships is an increasing trend in viewpoint such as the disposal issue of a retired ship, the enhancement of environmental regulation and resources recycling etc. for FRP ships. However, Al alloy ship which can achieve high speed by light weight in marine environment is exposed to a problem on materials damage by cavitation-erosion which is generated by large impact pressure with the collapse of air bubbles due to cavitation. Consequently, in this study, water cavitation peening technology was applied in Al alloy for ship to enhance durability life by preventing cavitation damage. So, the water cavitaton peening application time that presented the excellent cavitation characteristic investigated. The weight-loss of 5456-H116, 5083-H321 and 5052-O Al alloy at the optimum water cavitation peening time were improved to 42.11%, 50.0% and 25.7%, respectively.Key Words : Al ship, Water cavitation peening, Cavitation, Weightloss, 5000 series Al alloy

【With recent advances in engineering and technology, a damage on industrial machineries performing high-speed and high-power requirements has become a problem. There is an increasing possibility of cavitation damage, especially in pumps, propellers and high-speed vessels in a flowing liquid accordingly. There are several factors affecting cavitation damage on materials, including viscosity, pressure, temperature, amplitude applied. In this study, effects of cavity pressure in seawater on the damage for 5083-O aluminium alloy were evaluated by modulating amplitude. Trend of the damage with respect to time and amplitude was analyzed comparatively, and surface degradation of specimens was investigated by using Scanning Electron Microscope(SEM) and 3D microscope. The result reveals that the amount of the damage increased consistently with the increase in time and amplitude while the plastic deformation zone where no appreciable damage occurred was in less than 30 minutes.】

The painting and sacrificial anode method are only used on the hull of an aluminum ship to be exposed to marine environment due to aluminum’s excellent corrosion resistance. However, Cl-ion in sea water destroys the passive state film on the surface of aluminum alloy. In addition, corrosion and cavitation due to fast sea speed of an aluminum ship inflict damage on the hull of the aluminum ship. Thus, for the purpose of lengthening the life cycle of an aluminum alloy, there have been a number of investigations to improve durability and corrosion resistance of an aluminum alloy by heat treating the aluminum alloy or adding various chemical compositions. However, aluminum ships under the marine environment are sustaining a lot of corrosion due to lack of proper maintenance. Especially, cavitation damage is very severe and thus, to prevent this, surface treatment technique needs to be applied. Therefore, this study conducted water cavitation peening(WCP) on aluminum alloy for ships using the piezoelectric effect of ultrasonic and cavitation effect. By conducting WCP with time, optimal WCP time was verified excellent corrosion resistance under the sea water. As a result, optimum WCP time, showing the lowest corrosion current density, was 3.5 min for 5456-H116 and 4.0 min for 5083-H321.

We report our progress toward the synthesis of Urukthapelstatin A (Ustat A) and two analogues. Our retrosynthetic strategy involved the synthesis of three fragments: a tri-heteroaromatic moiety, a phenyl oxazole fragment, and a dipeptide. Described are the syntheses of three unique tri-heteroaromatic moieties. In addition, the corresponding linear precursors of Ustat A and two analogues are presented.

The use of Al alloys instead of fiber-reinforced plastic(FRP) in ship construction has increased because of the advantages of Al-alloy ships, including high speed, increased load capacity, and ease of recycling. This paper describes the effects of probe diameter on the optimum friction stir welding conditions of 5456-H116 alloy for leisure ship, measured by a tensile test. In friction stir welding using a probe diameter of 5 ㎜ under various travel and rotation speed conditions, the best performance was achieved with a travel speed of 61 ㎜/min. Using a probe diameter of 6 ㎜, rotation speeds of 170-210 rpm, and a travel speed of 15 ㎜/min produced a rough surface and voids because of insufficient heat input produced by the low rotation speed. At 500-800 rpm, chips were observed, although there were no voids, and the weld surface was excellent. However, at 1100-2500rpm, many chips were produced due to excessive heat input. Heat effects were very evident on the bottom. For a travel speed of 15 ㎜/min, heat input caused by friction increased as the rotation speed increased. The mechanical characteristics were degraded by accelerated softening due to increasing heat input.

동맥경화는 혈관 안에서 콜레스테롤의 침착 때문에 혈관이 좁아지거나, 딱딱해 지거나, 두꺼워 지게 되는데, 이런 현상이 심해지게 되면 동맥은 단단해져서 혈액이 원활히 통과하지 못하게 되고 심하면 사망 까지 이르게 되는 것이다. 본 연구에서는 복대동맥에서의 동맥경화가 진행되는 것을 탄성 혈관 일 때와 강성 혈관 일 때 각각 협착률이 혈관 직경의 20과 45%로 설정하고 속도와 압력 변화를 살펴보기 위하여 유한 요소 해석을 이용하여 모델링을 하였다. 혈관이 탄성 혈관일 때 속도와 압력 값은 협착률이 혈관 직경의 20%일 때 보다 45%일 때 더 높게 나타났으며, 강성 혈관에서 속도와 압력 값은 협착률이 혈관 직경의 20%일 때보다 45%에서 더 높았다. 협착률이 혈관 직경의 20과 45%인 탄성 혈관에서 재순환영역이 나타났다. 본 연구결과 혈관 협착에 따른 혈류역학적 특징을 이해하는데 도움이 될 것으로 판단된다. 【This study is about atherosclerosis which occupies the highest rate in many diseases people have and we have studied about atherosclerosis for abdominal aorta. Atherosclerosis is the phenomenon which blood vessel gets narrower, harder and thicker due to the stenosis of colesterol in blood vessel. If it becomes worse, arteries will be hard and blood can't flow smoothly, and even it can reach to death. In this study, the geometric models of the considered stenotic blood flow are two different types of constriction of cross-sectional area of blood vessel; 20 and 45% of constriction in each elastic wall and rigid wall. We have modeled by using finite element method to observe the changes of velocity and pressure. In case of the diameter of blood vessel decreased 45% in elastic wall model, the values of velocity and pressure were higher than the case of 20% and in case of the diameter of blood vessel decreased 45% in rigid wall model, the values of velocity and pressure were higher than the case of 20%. In cases of elastic wall models of the diameters of blood vessels decreased each of 20% and 45%, recirculation zones appeared. This results show understanding of hemodynamic properties depending on stenosed blood vessels.】

This study evaluated the effectiveness of antioxidants in animal models with damaged lungs such as inflammatory mediator-induced acute respiratory distress syndrome (ARDS) and established an ARDS therapy technique by suppressing active oxygen with membrane oxygenator. When inflammatory mediator that has an endotoxin, such as LPS, was injected directly into the airway, inflammatory pulmonary edema developed in the lung, and could induce ARDS. To treat such endotoxin-induced ARDS, the antioxidants such as taurine and dexamethasone were injected and their antioxidant effects were evaluated. They turned the blood pH to the normal condition, increased blood hemoglobin and hemocrit concentration and oxygen partial pressure (PO2), and improved survival. When a membrane oxygenator was used alone on the animal models with ARDS, similar antioxidant effects were identified. When a membrane oxygenator and antioxidants were used simultaneously, synergistic antioxidant effects were revealed. Therefore, the simultaneous use of antioxidants and membrane oxygenator is more effective than the use of either of them in treating the animal models with ARDS. This result indicates that bilateral use of antioxidants and membrane oxygenator may be useful as a potential therapy technique for the treatment of acute respiratory distress syndrome.

Aluminum alloys for ships have high mechanical strength and light, and their specific strength is higher than steel ships, enabling high speed and light weight. To lengthen the life of aluminum alloy ships, many studies are being conducted to improve durability through heat treatment and the addition of various elements, but they are still exposed to the harsh ocean environment. As the possibility of cavitation damage is getting higher because of the high speed of aluminum ships, it is critical to select aluminum alloys for ships that have excellent characteristics in ocean environment. For this purpose, cavitation experiments were conducted for the Al-Mg alloy of the 5000 series as hull materials that directly contact seawater, and their behaviors were examined and compared. The cavitation experiments revealed that the 5083-O and the 5083-H116 alloys showed the largest and the smallest weight loss, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

The objective of this study was to scrutinize the involvement of nitric oxide (NO) and the diagnosis of blood in ARDS in a rat model determined by the sequential exposure to lipopolysaccharide (LPS). Also, the present study was designed to evaluate the effects of taurine and dexamethasone on ARDS induced by LPS. Measurements of nitrite/nitrate were elevated in BAL of LPS challenged rats, indicative of an induction of the NO synthase. Taurine and dexamethasone abrogated the extent of endotoxin-induced ARDS, as evidenced by the decreases BAL nitrate/nitrite, BALF protein and lung pathology. T+L+D-group had higher PaO2 and lower PaCO2 values than L-group and T+Lgroup. But, ionized Ca2+ and Mg2+ both were not shown significant change. Also, T+L and T+L+D-group showed significant increase compared with L-group, but for the other side no significant difference was seen between T+L and T+L+D group. We suggest that taurine and dexamethasone may be a drug of choice for preventing ARDS.

In this study, to evaluate the corrosion resistance in the case of the identical welding by the gas metal arc welding with the STS 304 and STS 316L alloys, the double wall gas pipe materials, using the ER 308L electrode, the corrosion characteristics of the base metal and the welding zone were compared and evaluated by various electrochemical experiments in 10% oxalic acid solution, and the corrosion behavior was analyzed by observing the process of the corrosive damage. The STS 304 identical welding zone was a small cathode-large anode cell where the base metal played the role of an anode and protected the welding zone. However, corrosion took place preferentially in the STS 316L welding zone because the welding zone played the role of an anode. Copyright © 2012 John Wiley & Sons, Ltd.

Al-bronze used in this study is the alloy that has good strength, ductility and excellent corrosion resistance, oxidation resistance at high temperature, containing 9–12% of aluminum. This alloy is appropriate for large castings such as huge propeller, impeller, valves, high strength bearings and gear materials for ships, and widely used as the mechanical parts for chemical engineering. It was investigated the cavitation characteristics with temperature and cavitation time parameters for the ALBC3 in sea water environment. As a result, the cavitation surface damage showed a decreasing tendency with temperature and time increasing. Copyright © 2012 John Wiley & Sons, Ltd.

Previously, the ship was operated at a low speed, and erosion by the cavitation did not become a problem. Therefore, most of the hulls are being coated anti-corrosion painting. However, the corrosion in which accompanied physical erosion was accelerated while the ship became bigger and faster. Ship's stern is exposed to more severe environment such as tide, speed, cavitation and erosion corrosion. Accordingly, this study applied for thermal spray coating to provide better electrochemical characteristics and corrosion resistance in marine environment. The steel used for ship constructions was spray-coated with 85%Al-14.5%Zn-0.5%Zr wire, and additionally, the spray distance was diversified. Results of electrochemical and cavitation test, the case of 30 cm was determined as the optimum spray distance. Copyright © 2012 John Wiley & Sons, Ltd.

Development of new efficient, high voltage switching devices with wide safe operating area and low on-state losses has received considerable attention in recent years. One of those structures with a very effective geometrical design is the trench gate Insulated Gate Bipolar Transistor(IGBT).power IGBT devices are optimized for high-voltage low-power design, decided to aim. Class 1,200 V NPT Planer IGBT, 1,200 V NPT Trench IGBT for class has been studied.

The galvanostatic tests for corrosion protection are conducted at various applied current densities during 93,600 sec, and evaluated in terms of the variations in current density with time and in the potential at the applied current density. In addition, the corrosion damage depth is analyzed with 3D analysis optical microscope after galvanostatic tests. In this study, it was investigated to decide condition of the corrosion protection gavalnostatic method for Cu-Al alloy that has an excellent corrosion resistance. In the galvanostatic test under the cavitation environment, the energy was reflected or cancelled out by the collision with the oxygen gas generated by the oxygen reduction action. The surface observation showed neither the cavitation damage nor the electrochemical damage in the current density over 0.01 in the dynamic state under the cavitation environment.

Biaxial and triaxial braided composites are modeled using finite element methods to predict effective material properties: for biaxial braids, diamond pattern (1/1), regular pattern (2/2), and Hercules pattern (3/3) are modeled, while for triaxial braids, a regular pattern (2/2) is modeled. A micromechanical approach is adopted to calculate material properties of the tows, which are critical compositions of braided composites. By applying periodical boundary conditions (PBC), four representative unit cells (RUC) in correspondence to the four types of braids are analyzed and compared. Subsequently, effective material properties are obtained with the braiding angle varying from 15° to 75° with an increment of 5°, from which the variation of the engineering constants with the braiding angle is studied. The prediction results are compared with the experimental values for two material systems, and good agreement is achieved.

Pressure vessels in vehicle industries, power plants, and chemical industries are often affected by flaw and defect generated inside the pressure vessels due to production processes or being used. It is very important to detect such internal defects of pressure vessel because they sometimes bring out serious problems. In this paper, an optical defect detection method using digital shearography is used. This method has advantages that the inspection can be performed at a real time measurement and is less sensitive to environmental noise. Shearography is a laser-based technique for full-field, non-contacting measurement of surface deformation (displacement or strain). The ultimate goal of this paper is to detect flaws in pressure vessels and to measure the lengths of the flaws by using unwrapping, phase images which are only obtained by Phase map. Through this method, we could decrease post-processing (next processing). Real length of a pixel can be calculated by comparing minimum and maximum unwrapping images with shearing angle. Through measuring several specimen defects which have different lengths and depths of defect, it can be possible to interpret quantitatively by calculating gray level.

In this study, the cavitation test and electrochemical experiments were conducted for ALBC3(Cu-Al) alloy that has an excellent corrosion resistance and cavitation characteristic in sea water. Based on the ASTMG32 regulation, the cavitation test was performed with the cavitation and cavitation erosion tester using piezoelectric effect. The electrochemical characteristics are evaluated with potentiostatic experiments in activation polarization potential range. As a result, cavitation damage is increased proportionally to temperature and time at amplitude. It is appeared that acceleration period in weight loss presented over 6 hours under the cavitation environment in sea water. In addition, corrosion damages were observed at the potential range of -3.2~-1.4 V as the result of potensiostatic experiments during 12 hours in activation polarization potential range.

Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al–Zn alloy wire material. Thereafter, and sealed specimens with F–Si sealer on Al–Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al–85%Zn seems to be appropriate not only in static environment but also in dynamic environment.

본 연구에서는 대용량 액화천연가스(LNG 즉 Liquefied Natural Gas) 저장탱크의 앵커스트랩(anchor strap)의 설계를 위한 구조해석이 수행되었다. 본 논문에 고려된 LNG 저장탱크는 반경이 40m 의 완전방호식 저장탱크로 크게 외조와 내조로 구성되고, 둘 사이의 공간은 단열재인 블랑켓과 펄라이트로 채워져있다. 앵커스트랩은 내조, 외조 및 코너프로텍션과 연결되어 있어 지진하중에 의한 내조의 파손을 방지하는 역할을 한다. 본 연구에서는 앵커스트랩만 고려한 단일모델과 실제 형상을 고려하여 앵커스트랩, 내조, 외조 및 코너프로텍션을 동시에 고려한 확장모델에 대해서 각각 유한요소해석을 수행하여 비교, 분석하였다. 하중조건으로는 LNG 의 유출상태 및 지진하중을 고려한 다섯 가지 경우를 고려하였고, 각 하중조건에 대한 두 모델의 Tresca 응력분포를 구하여 설계기준과 비교해 보았다.

Electrochemical behavior of 5083-H116 Al alloy with flow velocity of seachest material for Al ship was evaluated. To examine the electrochemical characteristics of flow velocity and its effects on the performance of the alloy, experiments were conducted at four flow velocity variables using static state with an agitator. An ultrasonic vibration generator using piezoelectric effect was used in cavitation test according to the requirements of in ASTM-G32. The results show that the corrosion current density and damage were increased by applying the flow velocity compared to static state. Therefore, it is determined that the case of applying flow velocity is weaker to the corrosion.

Ships and offshore structures are exposed to harsh marine environments, and maintenance and repair are becoming increasingly important to the industry and the economy. The major corrosion phenomenons of metals and alloys in marine environment are pitting corrosion, stress corrosion cracking, crevice corrosion, fatigue corrosion, cavitation-erosion and etc. due to the effect of chloride ions and is quite serious. Methods of protection against corrosion can generally be divided into two groups: anodic protection and cathodic protection. Anodic protection is limited to the passivity characteristics of a material in its environment, while cathodic protection can apply methods such as sacrificial anode cathodic protection and impressed current cathodic protection. Sacrificial anode methods using Al and Zn alloys are widely used for marine structures and vessels intended for use in seawater. Impressed current cathodic protection methods are also widely used in marine environments, but tend to generate problems related to hydrogen embrittlement caused by hydrogen gas generation. Therefore, it is important to the proper maintenance and operation of the various corrosion protection systems for ship in the harsh marine environment.

The corrosions resulting from defects in painting layers frequently occur in Al alloys, so the application of corrosion preventing systems is also very important. Optimum conditions in terms of electrochemistry in relation to solution treatment, quenching and artificial aging treatment were established in order to optimize precipitation strengthening conditions intended to enhance the strength of Al alloys. Slow strain rate tests (SSRT) at various applied potentials were conducted in potential range from −1.8 to −0.5 V. The results show that the maximum tensile strengths, elongations and time-to-fracture are shown to be high values. After precipitation strengthening heat treatment, a tendency appear that time-to-fracture increases as elongation increases. In the potential range from −1.3 V to −0.7 V, the specimens show excellent mechanical properties, and thus this range is considered to be a corrosion prevention range.

전북대학교 수의과대학 약리학교실·인수공통전염병연구소561-756 전북 전주시 덕진구 덕진동1가 664-14*전북대학교 대학원 화학공학과561-756 전북 전주시 덕진구 덕진동1가 664-14**전북대학교 공과대학 바이오메디칼공학부561-756 전북 전주시 덕진구 덕진동1가 664-14***전북대학교 공과대학 화학공학부561-756 전북 전주시 덕진구 덕진동1가 664-14****전북대학교 의학전문대학원 흉부외과학교실561-756 전북 전주시 덕진구 덕진동1가 664-14(2010년 8월 11일 접수, 2010년 11월 1일 채택)

In this study, we attempted a structural analysis in order to design a balloon type extracorporeal membrane oxygenator that can induce blood flow without using blood pumps for the purpose of complementing the weakness in the existing extracorporeal membrane oxygenator. To analyze the flow characteristic of the blood flow within the virtual model of extracorporeal membrane oxygenator, computational fluid dynamics(CFD) modeling method was used. The operating principle of this system is to make the surface of the extracorporeal membrane oxygenator keep contracting and dilating regularly by applying pressure load using a balloon, and the `ime Function Value`that changes according to the time was applied by calculating a half cycle of sine waveform and a cycle of sine.waveform Under the assumption that the uni-directional blood flow could be induced if the balloon type extracorporeal membrane oxygenator was designed as per the method described above, we conducted a structural analysis accordingly. We measured and analyzed the velocity and pressure of blood flow at both inlet and outlet of the extracorporeal membrane oxygenator through CFD simulation. As a result of the modeling, it was confirmed that there was a flow in accord with the direction of the blood by the contraction/dilation. With CFD simulation, the characteristics of blood flow can be predicted in advance, so it is judged that this will be able to provide the most optimized design in producing an extracorporeal membrane oxygenator.

In this study, we have developed shear horizontal(SH) surface acoustic wave(SAW) sensors for the detection of immunoglobulin G(IgG) on the gold coated delay line of SH-SAW devices. As the result of the experiment, we could uniformly immobilize anti-MIgG(mouse IgG) conjugate on the surface of gold. When displaying results of immobilization on the surface of gold using G-anti MIgG conjugate and blocking buffer in frequency shift, G-anti MIgG conjugate showed frequency shift of 75.1 kHz in the initial frequency, and blocking buffer showed frequency shift of 215.7 kHz. When various concentrations of MIgG was added in 100MHz type sensor, the sensor showed 46.3, 127.45, 161.21 and 262.39 kHz frequency shift at 25, 50, 75 and 100 MIgG concentration, respectively.

Use of Al alloy in the shipping industry has been increased due to various advantages such as high speed by lightness, increased load capacity by high strength and environmental-friendly compared with fiber-reinforced plastic (FRP) material. The welding of Al alloys have been conducted with MIG or TIG welding. However, the strength decrease by heat, become a serious problem in the process of ship construction. It can cause the deterioration of corrosion resistance at the heat-affected zone (HAZ) and the decrease in mechanical properties. The mechanical properties of dissimilar Al alloys (5052-O: 5083-H321) by FSW under various parameters such as rotating speed, traveling speed and the location of materials. First of all, the welding is conducted to find optimum FSW condition for dissimilar Al alloy with various parameters.

The structural steel demands are surging by the industry development. Among them, the demands of stainless steel has excellent anti-corrosion properties are expanding to various fields including the ship, offshore structure, petrochemical industry and living appliance. The stainless steel has some advantages that can change the property due to add chemical elements, various heat treatments and processing. However, in the STS 304, which makes up the majority of demands currently, involves a lot of risks the possibility of occurring stress corrosion cracking and hydrogen embrittlement of marine structure exposed to external forces and lower corrosion protection properties as destruction of passive layer in chloride environment. In this paper, we discuss the results of our investigations using potentiostatic slow strain rate test to estimate the durability of STS 304 against stress corrosion cracking (SCC) and hydrogen embrittlement (HE) under corrosive conditions of chloride ion exposure and tensile stress applied from external force. The optimum corrosion protection range without stress corrosion cracking and hydrogen embrittlement was concluded with the potential range of −0.5 ∼ −0.2 V (vs. Ag/AgCl).

With no annealing treatment, cathodic polarization trends in 5083F Al alloy revealed concentration polarization and activation polarization. However, the annealed specimens have lower current densities at corrosion protection potential compared to the non-annealed specimen. The results of SSRTs conducted in seawater at the applied potential range of −1.8 V to −0.5 V indicated that the maximum tensile strength, elongation, and time-to-fracture had high values at applied potentials of −0.7 to −1.4 V. The maximum tensile strength, elongation, and time-to-fracture decreased when the potential values were beyond this range in either anodic or cathodic direction. In general, the increased shear lip caused by annealing treatment indicates elongation. Time-to-fracture would likely increase with elongation. Potentials between −0.5 V to −0.6 V were found to be in the region of stress corrosion cracking. The corrosion protection zone was determined to be −0.7 V to −1.4 V because these potential ranges produced good mechanical properties. Potential less than −1.4 V produced a fractured surface with a mixture of dimples (ductile fractures) and a quasi-cleavage pattern resulting from the effects of hydrogen gas.

The specific strength of Al ships is higher than that of steel ships. They are capable of high speed, have increased load capacities, greater ease of recycling, and high anticorrosion properties. We report a number of electrochemical experiments undertaken to determine the optimum corrosion protection potential conditions for MIG welded for protecting 5083-H116 (Al–Mg alloy) in natural seawater. Cathodic polarization results in concentration polarization by dissolved oxygen reduction and activation polarization as a result of hydrogen generation. The maximum tensile strength, elongation and time-to-fracture decreased when the potential shifted beyond the potential range of − 1.2 V to − 0.7 V in either the anodic or cathodic directions.

Recent developments in high-technology experimental equipment and semiconductor micro fabrication technology have made it possible to study various characteristic quantum phenomena such as quantized conductance and coulomb-blockade effects at the nano-scale level. One recent study attempted to fabricate a normal-super-normal double tunneling junction in a split-gate wire. In this study, we describe the results of transmission electron microscopy (TEM) observation of a single 100 nm wide and 200 nm high Ni dot, which had been fabricated using scanning tunneling microscopy (SEM), placed on the top of the bridge of a Si-doped GaAs epitaxial layer grown by molecular beam epitaxy using a Riber 32 apparatus. The results from the successful use of TEM to observe the results of a SEM fabrication procedure support the contention that the fabricated Ni dot became a poly-crystal that was amorphous between GaAs crystal and a surface dot fabricated by applying voltage pulse to a STM tip, covered by an oxygenated film approximately 20 nm thick.

Interest in Al alloys for ship construction has increased because of the advantages of high speed with lightweight, increased load capacity, and ease of recycling compared to fiber-reinforced plastic. This study determined that the optimum traveling and rotation speeds for friction stir welding of 5052-O and 6061-T6 Al alloys for shipbuilding applications are 61 mm/min and 1600 RPM, respectively.

Austenitic stainless steels have problem such as pitting, intergranular corrosion and stress corrosion cracking, which causes severe damage of structure in spite of high toughness and mechanical strength. To minimize these disadvantages in offshore structures demand of STS 316L which has small amount of C and has Mo is increasing. In this paper, the electrochemical experiments are executed to evaluate the durability at various protection potentials on stress corrosion cracking and hydrogen embrittlement of STS 316L in natural sea water environment. The polarization trend for STS 316L shows the effects of concentration polarization due to dissolved oxygen reduction reaction and activation polarization due to hydrogen gas generation. The turning point of two reactions in the polarization curve presented -0.92 V (vs. Ag/AgCl). The lowest current densities in the potentostatic test and non-correded surface condition of specimens by SEM analysis presented at potentials of 0 ~ -0.9 V and 0.4 ~ -0.9 V, respectively. Synthetically, the optimum corrosion protection range without stress corrosion cracking and hydrogen embrittlement is concluded with the potential range of -0.56 V ~ -0.92 V.

Friction stir processing (FSP) was used to improve the mechanical characteristics and microstructure of AC7AV cast Al–Mg alloy. The mechanical characteristics of AC7AV deteriorated due to significant defects caused by excessive friction heat after being subjected to multi-pass FSP. An alternative method of multi-pass FSP with two traveling directions was used to solve the defect problems in multi-pass FSP for cast AC7AV Al alloy. The results of various multi-pass FSP experiments showed that the mechanical properties of the cast AC7AV Al alloy specimens subjected to this alternative multi-pass FSP were better than those produced by the conventional multi-pass FSP method.