• Computers and Concrete
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• v.7 no.2
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• pp.159-167
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• 2010

This paper demonstrates numerical techniques for complex large-scale modeling with microplane constitutive theories for reinforced high strength concrete, which for these applications, is defined to be around the 7000 psi (48 MPa) strength as frequently found in protective structural design. Applications involve highly impulsive loads, such as an explosive detonation or impact-penetration event. These capabilities were implemented into the authors' finite element code, ParaAble and the PRONTO 3D code from Sandia National Laboratories. All materials are explicitly modeled with eight-noded hexahedral elements. The concrete is modeled with a microplane constitutive theory, the reinforcing steel is modeled with the Johnson-Cook model, and the high explosive material is modeled with a JWL equation of state and a programmed burn model. Damage evolution, which can be used for erosion of elements and/or for post-analysis examination of damage, is extracted from the microplane predictions and computed by a modified Holmquist-Johnson-Cook approach that relates damage to levels of inelastic strain increment and pressure. Computation is performed with MPI on parallel processors. Several practical analyses demonstrate that large-scale analyses of this type can be reasonably run on large parallel computing systems.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3196-3206
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• 2021

For the Korean design of the PCCS (passive containment cooling system) in an innovative PWR, the overall thermal resistance around a condenser tube is dominated by the heat transfer coefficient of steam condensation on the exterior surface. It has been reported, however, that the calculated heat transfer coefficients by thermal-hydraulic system codes were much lower than measured data in separate effect tests. In this study, a new empirical model of steam condensation in the presence of a noncondensable gas was implemented into the MARS-KS 1.4 code to replace the conventional Colburn-Hougen model. The selected correlation had been developed from condensation test data obtained at the JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube) facility, and considered the effect of the Grashof number for naturally circulating gas mixture and the curvature of the condenser tube. The modified MARS-KS code was applied to simulate the transient response of the containment equipped with the PCCS to the large-break loss-of-coolant accident. The heat removal performances of the PCCS and corresponding evolution of the containment pressure were compared to those calculated via the original model. Various thermal-hydraulic parameters associated with the natural circulation operation through the heat transport circuit were also investigated.

• The Research Journal of the Costume Culture
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• v.29 no.5
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• pp.651-664
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• 2021

The purpose of this study is to first examine the relationship between appearance-enhancing beauty practices and feminism, and secondly, to analyze public images of contemporary women using this paradigm. Through the lens of this relationship, we present a literature review and empirical research focusing on the evolution of public image trends among girl groups, with special attention to the Refund Sisters, a South Korean supergroup currently drawing mainstream attention as female icons. The scope of analysis includes girl groups dating from the 1990's to the year 2020 and photos of the Refund Sisters. Our results indicate that firstly, free sexual expression is evident based on active use of sexuality; images contain bold demonstrations of females desire, expressions previously considered taboo. Secondly, we note deviations from more standardized female images, unique adornment of outward appearance, and rejection of normative female images through freer forms of self-presentation. Lastly, there is greater cultural and racial diversity, rejection of modern race and gender binaries, and increased representation of queer identities. However, the relationship between appearance-enhancing beauty practices and feminism is sometimes considered paradoxical, with some arguing that beautifying one's outward appearance is a compulsory strategy and that it should be rejected in order to resist aesthetic pressure.

• Geomechanics and Engineering
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• v.16 no.5
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• pp.483-493
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• 2018

Experimental study of the deterioration of high-temperature rock subjected to rapid cooling is essential for thermal engineering applications. To evaluate the influence of thermal shock on heated granite with different temperatures, laboratory tests were conducted to record the changes in the physical properties of granite specimens and the dynamic mechanical characteristics of granite after rapid cooling were experimentally investigated by using a split Hopkinson pressure bar (SHPB). The results indicate that there are threshold temperatures ($500-600^{\circ}C$) for variations in density, porosity, and P-wave velocity of granite with increasing treatment temperature. The stress-strain curves of $500-1000^{\circ}C$ show the brittle-plastic transition of tested granite specimens. It was also found that in the temperature range of $200-400^{\circ}C$, the through-cracks induced by rapid cooling have a decisive influence on the failure pattern of rock specimens under dynamic load. Moreover, the increase of crack density due to higher treatment temperature will result in the dilution of thermal shock effect for the rocks at temperatures above $500^{\circ}C$. Eventually, a fitting formula was established to relate the dynamic peak strength of pretreated granite to the crack density, which is the exponential function.

• Journal of TMJ Balancing Medicine
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• v.8 no.1
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• pp.6-10
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• 2018

In order to propose a fundamental and appliable theories for balancing therapy of temporomandibular joint (TMBT), evolutionary proofs and up-down theories in evolutionary biology and Korean medicine were investigated. Balancing therapy of temporomandibular joint treats disorder and diseases of the whole body through straightening of the abnormal linking between temporomandibular joint and axis. Although the mechanism of this therapy contains many merits like multicellular integrity and coadjustment, ease of balance and alert forward mobility by the bipedal stepping and evolution to Homo sapiens, increasing disadvantages of balancing pressure of right and left in the lengthened perpendicular axis and the balancing load of temporomandibular joint and axis following the reactional change of dental occlusion are deeply related and considered in this therapy. As for up-down theory, crossing of heavenly qi and earth qi centering on cervical joint is presented as the first mechanism for TMBT, and the other ones like in-out and up-down qi activity of tripple energizer, up-down of essence-qi-spirit in the three backbone barrier and three cinnabar field, up-down of yin-yang-water-fire of viscera and bowels can be related too.

• Tribology and Lubricants
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• v.37 no.5
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• Corrosion Science and Technology
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• v.21 no.2
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• pp.138-146
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• 2022

The cavitation and potentiodynamic polarization experiments were conducted simultaneously to investigate the effect of cavitation amplitude on the super austenitic stainless steel (UNS N08367) electrochemical behavior in seawater. The results of the potentiodynamic polarization experiment under cavitation condition showed that the corrosion current density increased with cavitation amplitude increase. Above oxygen evolution potential, the current density in a static condition was the largest because the anodic dissolution reaction by intergranular corrosion was promoted. In the static condition, intergranular corrosion was mainly observed. However, damage caused by erosion was observed in the cavitation environment. The micro-jet generated by cavity collapse destroyed the corrosion product and promoted the repassivation. So, weight loss occurred the most in static conditions. After the experiment, wave patterns were formed on the surface due to the compressive residual stress caused by the impact pressure of the cavity. Surface hardness was improved by the water cavitation peening effect, and the hardness value was the highest at 30 ㎛ amplitude. UNS N08367 with excellent mechanical performance due to its high hardness showed that cavitation inhibited corrosion damage.

• Wind and Structures
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• v.37 no.2
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• pp.79-94
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• 2023

This paper traces the drafting of the new EN 1991-1-4 Eurocode 1 - Actions on structures - Part 1-4: General actions - Wind actions within Mandate M/515 of the European Commission to CEN, for the evolution of structural Eurocodes towards their Second Generation. Work of the Project Team started in August 2017 and ended in April 2020, with delivery of a final draft for public enquiry. The revised document contains several modifications with respect to the existing 2005 version, and new sections were added, covering aspect not dealt with in the previous version. It has a renovated structure, with a main text limited in size and containing only fundamental material; all the remaining information, either normative or informative is arranged into thirteen annexes. Common to other Eurocode Parts, general requests from CEN were those of reducing the number of Nationally Determined Parameters and of enhancing the ease of use. More specific requests were those of (a) the drafting of a European design wind map, (b) improving wind models, (c) reviewing force and pressure coefficients, (d) reviewing the procedures for evaluation of the dynamic response, as well as (e) making editorial improvements aimed at a more user friendly document. The author had the privilege to serve as Project Team member for the drafting of the new document, and this paper brings his personal view concerning some general aspects of wind code writing, and some more specific aspects about the particular document.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.39.1-39.1
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• 2019

We trace the cosmological origin of satellites around isolated dwarf galaxies using a very high resolution (12 pc/h) cosmological hydrodynamic zoom simulation. To realistically describe the formation and evolution of small-mass stellar satellites, our model includes a full baryonic physics treatment. We find that the mini-halos form objects resembling dwarf galaxies. The majority of their star forming gas is accreted after reionization, thus the survival of a mini-halo's gas to reionization is not an important factor. Instead, the key factor seems to be the ability for a mini-halo to cool its recently accreted gas, which is more efficient in more massive halos. Although the host galaxy is only a dwarf galaxy itself, we find that ram pressure is an efficient means by which accreted mini-halos lose their gas content, both by interacting with hot halo gas but also in direct collisions with the gas disk of the host. The satellites are also disrupted by the tidal forces near the center of the host galaxy. Compared to the disrupted satellites, surviving satellites are relatively more massive, but tend to infall later into the host galaxy, thus reducing the time they are subjected to destructive environmental mechanisms and dynamical friction.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.779-791
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• 2023

Long-termly used in water supply, an underground concrete pipe is easily subjected to the coupled action of pressure loading and flowing water, which can cause the chemo-mechanical damage of the pipe, resulting in its premature failure and lifetime reduction. Based on the leaching characteristics and damage mechanism of concrete pipe, this paper proposes a coupled chemo-mechanical damage and failure model of underground concrete pipe for water supply, including a calcium leaching model, mechanical damage equation and a failure criterion. By using the model, a numerical simulation is performed to analyze the failure process of underground concrete pipe, such as the time-varying calcium concentration in concrete, the thickness variation of pipe wall, the evolution of chemo-mechanical damage, the distribution of concrete stress on the pipe and the lifetime of the pipe. Results show that, the failure of the pipe is a coupled chemo-mechanical damage process companied with calcium leaching. During its damage and failure, the concentrations of calcium phase in concrete decrease obviously with the time, and it can cause an increase in the chemo-mechanical damage of the pipe, while the leaching and abrasion induced by flowing water can lead to the boundary movement and wall thickness reduction of the pipe, and it results in the stress redistribution on the pipe section, a premature failure and lifetime reduction of the pipe.