• Transactions of Materials Processing
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• v.31 no.5
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• pp.253-260
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• 2022

In this study, the microstructural characteristics of a high-speed-extruded Mg-5Bi-3Al (BA53) alloy and its tensile, compressive, and high-cycle fatigue properties are investigated. The BA53 alloy is successfully extruded at a die-exit speed of 16.6 m/min without any hot cracking using a large-scale extruder for mass production. The homogenized BA53 billet has a large grain size of ~900 ㎛ and it contains fine and coarse Mg₃Bi₂ particles. The extruded BA53 alloy has a fully recrystallized microstructure with an average grain size of 33.8 ㎛ owing to the occurrence of complete dynamic recrystallization during high-speed extrusion. In addition, the extruded BA53 alloy contains numerous fine lath-type Mg₃Bi₂ particles, which are formed through static precipitation during air cooling after exiting the extrusion die. The extruded BA53 alloy has a high tensile yield strength of 175.1 MPa and ultimate tensile strength of 244.4 MPa, which are mainly attributed to the relative fine grain size and numerous fine particles. The compressive yield strength (93.4 MPa) of the extruded BA53 alloy is lower than its tensile yield strength, resulting in a tension-compression yield asymmetry of 0.53. High-cycle fatigue test results reveal that the extruded BA53 alloy has a fatigue strength of 110 MPa and fatigue cracks initiate at the surface of fatigue test specimens, indicating that the Mg₃Bi₂ particles do not act as fatigue crack initiation sites. Furthermore, the extruded BA53 alloy exhibits a higher fatigue ratio of 0.45 than other commercial extruded Mg-Al-Zn-based alloys.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.243-251
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• 2022

The purpose of this study is to investigate experimentally the effect of polyethylene fibers with different tensile strength and aspect ratio on the properties of cementless composite. Three types of mixtures according to the types of polyethylene fibers and water-to-binder ratio were prepared and density, compressive strength and tension tests were performed. Test results showed that the mixture reinforced by polyethylene fiber with a low tensile strength by 10 % and a high aspect ratio by 8.3 % had a high tensile strain capacity by 11.7 %, a high toughness by 12.4 %, and a low crack width by 9.1 %. It was also observed that high tensile strain capacity and better cracking pattern could be achieved by increasing the water-to-binder ratio of composite although its strength is low.

• Composites Research
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• v.19 no.4
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• pp.15-22
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• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.309-316
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• 2010

This paper proposed a nonlocal anisotropic damage model to simulate the behavior of plain and reinforced concrete structures that are predominantly tensile and compressive load. This model based on continuum damage mechanics, used a symmetric second-order tensor as the damage variable. For quasi-brittle materials, such as concrete, the damage patterns were different in tension and in compression. These two damage states were modeled by damage evolution laws ensuring a damage tensor rate proportional to the total strain tensor in terms of principal components. To investigate the effectiveness of proposed model, the double edge notched specimen experimented by nooru-mohamed and reinforced concrete bending beam were analyzed using the implementation of the proposed model. As the results for the simulation, the nonlocal anisotropic damage model with an adequate control of rupture correctly represented the crack propagation for mixed mode fracture. In the structural failure of reinforced concrete bending beam, the proposed model can be showed up to a very high damage level and yielding of the reinforcements.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.135-142
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• 2024

The purpose of this study is to experimentally investigate the effect of water-binder ratio and fiber type on the compressive strength and tensile performance of fiber reinforced highly ductile composites. To achieve this, four different mixtures were prepared by varying the water-binder ratio and fiber type, and compression and tension tests were conducted. The test results showed that the influence of fiber type on compressive strength was minimal, however, the WB50 series mixture exhibited a 29 % lower strength compared to the WB40 series mixture, indicating a significant effect of the water-binder ratio. On the other hand, the effect of fiber type on tensile properties was found to be more significant than that of the water-binder ratio. Tensile strain capacity ranged from 2.9 % to 6.2 %, with PE series mixtures showing 1.63 to 2.14 times higher performance compared to PVA series mixtures. Additionally, the crack patterns of the PE series mixtures were superior than those of the PVA series mixtures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.98-106
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• 2008

The strengthening in terms of efficiency, easy, economics is very popular method when it is applied to a damaged structures. The purpose of this study develops anchorage system that supports enough strengthening effect without any damage. In addition it is checked whether the method can be conveniently applied to structures. To verify strengthening effect a flexural experiments were performed. Four concrete beams were constructed and tested. Deflections, strains and modes of failure were recorded to examine strengthen of beams. Comparing crack load of each experimental data, yielding load, ultimate load, ductility index, and tendon stress were analyzed.

• Korean journal of communication and information
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• v.41
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• pp.75-107
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• 2008

The paper aims to figure out the meaning of money in terms of communication in which we can find the specific communicative and cultural form of money. In the modern capitalist society, we cannot limit money within the economical terms - for example, store of value, medium of exchange, unit of account and means of payment - because money mediates all human activities beyond the economic boundary and conveys specific meaning in the social and the cultural area. Money can be the medium of the cultural and the communicational as well as the medium of the economic. In this respect, we've try to articulate money with linguistic or semiotic insight. Through this theoretical dialogue, we find two significations of money as a medium of communication. The first signification is meta-signification which drives the individual to the unlimited accumulation of the money. Meta-signification displace the second signification of the money that is the singular, over-determined and the mosaic significations. In this process money can be the signifier without signification. And then, money is the Master signifier which all sign should be identified imaginary. Finally, Money is not only the re-presense (Darstellung) of all sings but also the representative (Vertretung) of all signs. But this double position creates some tensions and makes master signifier of money unstable. Man's analysis of Bonapartism, which shares the linguistic or semiotic insight, shows the crack of the re-presence between the representative. Like Marx's analysis, the money has the tension between two signification which makes the room for the struggle to signify.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.175-181
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• 2017

The purpose of this study is evaluating the characteristics of tensile strength of UHPC and examining tensile performance of notched specimens by direct tensile test. For test variables, 120, 150, and 180MPa of target design standard strength were aimed at. With general water curing and $90^{\circ}C$ high temperature steam as curing conditions, the properties were reviewed. Overall, it was represented that the specimens of notch-type direct tensile strength concrete was effective in inducing central cracks compared with existing direct tension specimens. Through this, it was judged that data construction with high reliability was possible. Above all, in a graph of direct tensile strength and strain, in the case of steam curing at high temperature, there was great difference of initial tensile strength compared with water curing. As passing of ages, an aspect that the difference gradually decreased was shown. Maximum tensile strength was found to increase steadily with increasing age for all target design strengths in water curing, in the case of steam curing, the tendency to increase significantly due to the initial strength development effect at 7 days of age. The initial crack strength increases with age in case of underwater curing, in the case of steam curing, it was higher than that of water curing in 7 days, while the strength of 28 days was lowered. In this part, it is considered necessary to examine the arrangement condition of the steel fiber.

• Strategy21
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• s.33
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• pp.113-147
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• 2014

While China's military rise is an issue of growing importance to regional security, it is worthwhile to note that it is not China's military modernization per se, but its capacity to project and sustain power along and beyond its borders--in particular, the possibility to resolve forcefully its outstanding maritime disputes and various contingencies. This essay argues that China's "anti-access capability"--a U.S.-coined term originally developed for a Taiwan contingency--is equally applicable to other major regional cases such as the Spratly disputes and a North Korean contingency. Furthermore, notwithstanding China's continuos efforts to develop and deploy various types and classes of weapons/platforms, it is the Russian systems and technologies that are most capable and thus likely assigned to the highest mission-critical areas. In assessing China's current and likely future military capability as well as their implications for the region, it is necessary to take note of the following: • There exists asymmetry of military capability between China and its weaker neighbors. While the PLAN is weak in several important aspects, for instance, many of its neighbors' navies are weaker still. • Some have argued that China's foreign policy behavior apparently became more "assertive" in 2009-2013, but it is wiser to keep in mind that China has almost always been assertive and aggressive when it comes to what China defines as "sovereignty and territorial issues" as well as its newest "core interests." • On the South China Sea disputes it is the function of U.S. presence in the theater--in the form of overseas bases and the freedom of navigation--and the PLA's own limitations to project and sustain power for an extended period of time that have largely prevented armed. • While Taiwan remains the idee fixe of China's diplomacy and military, it is and will be a tough nut to crack. China's recent creeping attempts for economic integration with Taiwan should be seen in this context. • China and Japan, the two regional heavyweights and traditional rivals, will likely have a bilateral relationship that is replete with difficulties and tension. China's unilateral announcement of its ADIZ in November 2013 as well as the occasional yet persistent disputes with Japan over the Senkaku/Diaoyudao/Diaoyutai islands are only the latest manifestation of this deeper and difficult relationship. • For Korean security it is imperative to take into account the geostrategic and historical factors. On top of the existing military threats from North Korea, the ROK should be able to employ a) hedging strategy, b) "limited defense sufficiency" strategy, and c) rock-solid relations with the United States.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.2
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• pp.83-93
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• 1988

Recent Experimental results show that the J integral can be effectively used to obtain a valid parameter for predicting plane strain and plane stress fracture. However, only a few research results have been reported for the effect of thickness where the plane strain state can not be assumed. A purpose of this study is to find the behavior of fracture touhness and tearing modulus varing the specimen thickness. The type of specimen in the present study is compact tension (CT). The thicknesses of the low carbon steel specimens that are used in the experiments are 5, 10, 15, 20 and 25mm. The measurement of crack length is taken by optical measurements method. From the study, the followings are found; 1) The fracture toughness and the tearing modulus which are obtained by using Yoon's and Simpson's formula show more conservative than that by using Rice's and Merkel's. 2) The fracture toughness is increase in specimen thickness which is reached 15mm. Beyond this thickness the fracture toughness is decreased in specimen thickness. 3) In the case of CT specimen with the thickness ranging from 5 to 25mm, the tearing modulus which is applied the same J integral equation is almost constant. 4) By using Yoon's formula, the correlation of the plane slress fracture toughness J sub(C) with specimen thickness B is expressed as the following formula. J sub(C)/J sub(IC)=1.7-15.1(B/W)+112.9(B/W) super(2) -301.3(B/W) super(3) +260.6(B/W) super(4)