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Although mega-watt class onshore and offshore wind power systems are used to generate power due to their cost-effectiveness, small wind power systems are important for household usages. Researchers have focused on aerodynamic characteristics as a conceptual design from their previous studies on Archimedes spiral wind turbines. Here, we verified the design of a small wind turbine AWM-750D (100 W capacity) via both numerical simulation and experimentation. We used commercial code ANSYS CFX for numerical simulation and compared turbulence models and surface roughness for determining the performance. To obtain reliable and robust blades, we analyzed the effective manufacturing method with Moldflow. Through a test with an open-suction type atmospheric boundary layer wind tunnel, we varied wind speed from 4.0 m/s to the rated value of 12.5 m/s and obtained 106 W, equivalent to a power coefficient of 0.205. In addition, we compared the numerical and experimental power vs. rotational speed and found the former is 6.5% lower than the latter. In this study, we proved that numerical simulations can act as design verification methods to predict wind turbine performances and reliable manufacturing. Through our research, we provided the prototype of a small wind turbine with 100 W to act as an efficient electric power supplier for households and also the stable manufacturing process for complex spiral blades using injection molding.

In this study, the authors attempted to enhance the crack resistance of a carbon/epoxy composite by adding carbon nanotubes (CNTs) into the resin formulation. Prior to applying CNTs, a chemical surface treatment, amino-functionalization, was conducted to enhance the interfacial bonding between CNTs and epoxy resin. The resultant increase in tensile strength was attributed to good interfacial bonding quality. Two kinds of 3-phase carbon/CNT-epoxy unidirectional prepregs were fabricated via a hot-melting process with the addition of CNTs. The CNT-reinforcing and -functionalizing effects were investigated through DCB tests and measurement of the acoustic emission (AE) signal of a cross-ply specimen both at RT and at −150 °C. The carbon/epoxy composite containing functionalized-CNTs showed improved interlaminar fracture toughness and transverse crack resistance at the cryogenic temperature.

Multi-wall carbon nanotube (MWNT) added carbon fiber reinforced plastics (CFRP) and thin-ply composites are suggested as solutions to improve resistance against low earth orbit (LEO) environment and mechanical properties. Accelerated ground simulation experiments were performed for CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP. The used ground simulation facility can simulate high vacuum, atomic oxygen, ultraviolet (UV) light and thermal cycling simultaneously. The aging experiment was performed for 20 h. After the aging experiment, total mass loss (TML) and tensile properties were measured. As a result, by applying thin-ply thickness and MWNT fillers, the tensile strength was improved at ground conditions. Under an LEO space environment, while thin-ply composites cannot relieve the degradation rate, the composites with MWNT can do so. Highly improved tensile strength was observed by simultaneously applying the thin-ply techniques and MWNT under both LEO aged and LEO non-aged conditions.

In this study, the tensile properties of carbon fiber reinforced polymer (CFRP) composites with different resin compositions were investigated in order to develop advanced composite materials for cryogenic use. Thermo-mechanical cyclic loading (up to 6 cycles) was applied to CFRP unidirectional laminate specimens from room temperature to –150°C. Tensile tests were then performed at –150°C using an environmental test chamber. In addition, matrix-dominant properties such as the transverse and in-plane shear characteristics of each composite model were measured at –150°C to examine the effects of resin formulation on their interfacial properties. The tensile tests showed that the composite models with large amounts of bisphenol-A epoxy and CTBN modified rubber in their resin composition had good mechanical performance at cryogenic temperatures (CTs).

The improvement of crack resistance is essential to the application of fiber reinforced composites for cryogenic use. In this study, the authors attempted to enhance the crack resistance of a carbon/epoxy composite by adding multi-walled carbon nanotubes (MWNTs) into the resin formulation. Prior to assessing the effect of MWNTs, the effect of a toughened epoxy resin on the mode I interlaminar fracture toughness was investigated at −150 °C using double cantilever beam (DCB) specimens. It was found that the degree of fracture toughness enhancement obtained from application of the toughened epoxy at cryogenic temperature was less than that at room temperature, due to embrittlement of the epoxy resin. MWNT-added carbon/epoxy unidirectional prepregs were fabricated via a filament winding method with different concentrations of MWNTs (0.0 wt% for baseline, 0.2 wt% and 0.7 wt%). Material systems blended with 0.2 wt% and 0.7 wt% of MWNTs showed enhanced fracture toughness and low crack density at the cryogenic temperature.

In this study, the characteristics of filament wound composite/aluminum ring specimens were investigated at cryogenic temperature. Ring specimens were manufactured using carbon fiber and Type B epoxy resin which had been developed for cryogenic use. By measuring the thermal strain at −150 °C, it was found that compressive thermal stress was induced in the composite part, while the tensile thermal stress in aluminum part, which was about 32% of yield stress, in turn caused aluminum to yield at a lower load level. In addition, the thermal strain from a finite element analysis showed good agreement with this measure in an experiment. After six mechanical loading cycles were applied to the ring specimen at −150 °C, tensile tests were performed at −150 °C using split disk fixtures. The results of these tests showed that the composite strength in a liner-composite tank structure for use in a cryogenic propellant tank is decreased by the applied auto-frettage pressure.

In this study, effects of curing temperature and autofrettage pressure on a Type 3 cryogenic propellant tank, which is composed of composite hoop/helical layers and a metal liner, were investigated by thermo elastic analysis using finite element method. The temperature field of a Type 3 tank was obtained by solving the heat transfer problem and, in turn, was used as the nodal temperature boundary conditions during the elastic analyses for curing temperature and autofrettage pressure effects. Progressive failure analysis was also introduced in this procedure. As a result, it was shown that the higher the curing temperature was, the more residual compressive stress and tensile stress were induced in composites and metal liner, respectively. On the contrary, autofrettage pressure brought the reduction of these residual thermal stresses caused by cryogenic environments to the tank structure and these trends were verified from the composite/aluminum ring specimen tests at cryogenic temperature, which is suitable for preliminary tests of filament wound structures. This tradeoff for curing temperature and autoprettage pressure must be considered in the design and manufacturing stages for a Type 3 cryogenic tank.

Nowadays, researches for replacing material systems for cryotanks by composites have been being performed for the purpose of lightweight launch vehicle. In this paper, a type 3 propellant tank, which is composed of the composite developed for cryogenic use and an aluminum liner, was fabricated and tested considering actual operating environment, that is, cryogenic temperature and pressure. For this aim, liquid nitrogen (LN2) was injected into the fabricated tank and in turn, gaseous nitrogen (GN2) was used for pressurization. During this test procedure, strains and temperatures on the tank surface were measured. The delamination between hoop layer and helical one, was detected during the experiment. Several attempts were followed to investigate the cause analytically and experimentally. Thermo-elastic analysis in consideration of the progressive failure was done to evaluate the failure index. Experimental approach through a LN2 immersion test of composite/aluminum ring specimens suitable for simulating the Type 3 tank structure.

In this study, the tensile properties of a T700/epoxy composite, which had been cycled with thermo-mechanical loads at low temperatures, were measured using an environmental test chamber. Thermo-mechanical tensile cyclic loading (up to 10 cycles) was applied to T700/epoxy unidirectional laminates at room temperature (RT) to −50 °C, RT to −100 °C, and RT to −150 °C (CT), respectively. Results showed that tensile stiffness significantly increased as temperature decreased, while the thermo-mechanical cycling had little influence on it. Tensile strength, however, decreased as temperature decreased down to CT, while the decreasing rate of strength was reduced after CT cycling. For the analysis of the test results, the coefficients of thermal expansion (CTEs) of the laminate composite specimen, both at RT and CT, were measured, and the interface between fiber and matrix was observed using SEM images.

The present study aimed to develop a security evaluation methodology and criteria for a ubiquitous healthcare (u health) system. For this purpose, first, we classified the components of a u-health system. Second, security core technologies were selected that could be applied to a u-health system in three aspects, such as administrative safeguards dealing with the operator, policies, documents, systems, and user education, physical safeguards, dealing with control of entrance and exit, and screens or shared instruments, and technical safeguards, dealing with computer system-related technological elements. Then, each security core technology was assigned to each component of a u-health system, and the relative significance of each was determined. Finally, a methodology and criteria for the evaluation of security and privacy were developed. In conclusion, the outcome can be used for enhancing the security level in the design of a u-health system and setting authentication standards for authorization processes for security.

The present study analyzed the current state and related issues of standardization of personal medical information security by probing information security standards, guidelines, related statutes and certification programs in order for Korea to take initiatives in international standardization of security for ubiquitous healthcare (u-health). We chose essential elements of privacy, security and safety to investigate the international standardization status; in user privacy, user authentication, user ID security, and user identification, in health information security, data security, security infrastructure, accountability assurance, communication security, ID management and access control, non-repudiation, security management, and backup, storage, archiving, disposal, in safety, risk management, technology for emergency access, disassemble prevention and fixation, and equipment error check. As a result, we came up with the conclusion that Korea must immediately take the initiative of developing an international standard that addresses the overall safety of medical equipment, including emergency access, electrical malfunctioning management, and operational condition check.

A 59-year-old male patient was admitted to our hospital because of mild exertional dyspnea. A chest radiograph showed mesocardia (Fig. 1). The electrocardiogram showed a sinus rhythm with a rate 59 bpm, first degree AV block and T-wave inversion in the V2-6 leads. Physical examination revealed a blood pressure of 120/80 mm Hg and a respiratory rate of 20 bpm. There was no history of trauma, diabetes, or any operations. The patient also had no connective tissue disorders or any other systemic anomalies, and there was no significant family history of disease. ECG-gated 64-slice multidetector computed tomography (MDCT) was performed. The ascending aorta was anterior and to the left of the main pulmonary artery (Fig. 2a). The aorta arises from the ventricle that is positioned on the left. The noncoronary cusp was anterior and to the left of both the left and right coronary cusps (Fig. 2b). The left sided ventricle has a muscular outflow tract (infundibulum) that separated the atrioventricular and aortic valves (Fig. 3). Four-chamber view from 64-slice MDCT showed a normal atrial situs but abnormal apical displacement of the left sided atrioventricular valve (Fig. 4a). Moreover, the left sided

This paper deals with the damping properties of a viscoelastic three-layered cantilever with partial delamination. The expression for the loss factor of this cantilever is presented as the ratio of the dissipation energy to the strain energy. In analysis, the loss factors due to shearing and bending are determined independently, and the total loss factor is derived from their collective sum. According to this analysis, the effects of the delamination length, delamination position and thickness of each layer on the loss factor corresponding to each vibration mode are investigated. As a result, it is clarified that delamination makes the magnitude of the loss factor larger than in the case of no delamination, and that the value of the loss factor increases as the delamination length becomes large. In experiments, it was ascertained that the experimental values of the loss factor were in good agreement with the theoretical ones.

This paper deals with damping characteristics of a laminated cantilever. In order to determine the loss factor of a three-layered cantilever with arbitrary thickness, an analytical method of evaluating the position of the neutral plane is presented when it exists in the middle layer. Using both this method presented here and Ross' method applicable to the case wherein the neutral plane exists in the first layer, it was found that the position of the neutral plane can be obtained accurately. In addition, it is shown that its position leads to the determination of the loss factor of the three-layered cantilever. From experiments, it was ascertained that these theoretical values of the loss factor agreed well with the experimental values. Moreover, it was clarified which cantilever has better damping characteristics between three-layered and two-layered cantilevers.

Background Bone marrow derived stem/progenitor cell transplantation after acute myocardial infarction is safe and effective for improving left ventricular systolic function. However, the improvement of left ventricular systolic function is limited. This study will evaluate novel stem/progenitor cell therapy with combination cytokine treatment of the long-acting erythropoietin analogue, darbepoetin, and granulocyte colony-stimulating factor (G-CSF) in patients with acute myocardial infarction. Methods The 'MAGIC Cell-5-Combination Cytokine Trial' is a multicenter, prospective, randomized, 3-arm, controlled trial with blind evaluation of the endpoints. A total of 116 patients will randomly receive one of the following three treatments: an intravenous darbepoetin infusion and intracoronary infusion of peripheral blood stem cells mobilized with G-CSF (n = 58), an intracoronary infusion of peripheral blood stem cells mobilized with G-CSF alone (n = 29), or conventional therapy (n = 29) at phase I. Patients with left ventricular ejection fraction < 45% at 6 months, in the patients who received stem cell therapy at phase I, will receive repeated cell therapy at phase II. The objectives of this study are to evaluate the safety and efficacy of combination cytokine therapy with erythropoietin and G-CSF (phase I) and repeated progenitor/stem cell treatment (phase II). Discussion This is the first study to evaluate the safety and efficacy of combination cytokine based progenitor/stem cell treatment. Trial registration http://www.ClinicalTrials.gov identifier: NCT00501917.

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OBJECTIVE To investigate the circadian variation of plasma antidiuretic hormone (ADH) and urine output in patients with severe nocturia (> three times per night) and to assess the effect of oral desmopressin on nocturnal urine output in these patients. PATIENTS AND METHODS Twelve patients with severe nocturia and five age-matched controls without were assessed over 24 h (circadian sampling) during a 72-h hospital admission. Blood levels of ADH and changes of urine output were measured in the patients before and after the oral administration of desmopressin (0.2 mg, at 22.00 hours in the second day), and in the controls not treated with desmopressin. RESULTS Compared with the normal control, the patients had no diurnal variation in urine output and greater nocturnal urine production, associated with a lack of nocturnal increase in ADH level. Compared with the baseline urine output, desmopressin significantly decreased night-time (23.00–08.00 hour) urine output in the patients (P