• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.1-10
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• 2009

The safe and reliable performance of fusion and fission plants depends on the choice of suitable materials and an assessment of long-term materials degradation. These materials are degraded by their exposure to extreme conditions; it is necessary, therefore, to address the issue of long-term damage evolution of materials under service exposure in advanced plants. The empirical approach to the study of structural materials and fuels is reaching its limit when used to define and extrapolate new materials, new environments, or new operating conditions due to a lack of knowledge of the basic principles and mechanisms present. Materials designed for future Gen IV systems require significant innovation for the new environments that the materials will be exposed to. Thus, it is a challenge to understand the materials more precisely and to go far beyond the current empirical design methodology. Breakthrough technology is being achieved with the incorporation in design codes of a fundamental understanding of the properties of materials. This paper discusses the multi-scale, multi-code computations and multi-dimensional modelling undertaken to understand the mechanical properties of these materials. Such an approach is envisaged to probe beyond currently possible approaches to become a predictive tool in estimating the mechanical properties and lifetimes of materials.

• International Journal of Highway Engineering
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• v.14 no.5
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• pp.57-65
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• 2012

PURPOSES: It is important to consider the long-term performance of concrete pavement, because concrete pavement is more exposed to the various environmental conditions than any other concrete structures. One of the several methods to evaluate the long-term performance of concrete during winter is KS F 2456. Relative dynamic modulus of elasticity shows the resistance to freezing and thawing. METHODS: To measure relative dynamic modulus of elasticity, ultra sonic is generally used. But in this study, to measure the relative dynamic modulus of elasticity, both ultra sonic and shear wave were used and then compared each other. RESULTS: The results from the measurement by ultrasonic wave and shear wave were divided into three types. Type 1 : Specimens are good and relative dynamic modulus of elasticity did not decrease until 300 cycle. Type 2 : The relative dynamic modulus of elasticity decreased from the late cycle.(about 150 cycle later) Type 3 : The relative dynamic modulus of elasticity consistently decreased from the beginning. As a result of ANOVA, there is no difference according to measuring method, in type 2 and 3. But there is a difference according to measuring method, in type 1's relative dynamic modulus of elasticity. CONCLUSIONS: It is proved that shear wave can be used to understand the damage tendency of relative freezing and thawing and to measure the relative dynamic modulus of elasticity.

• Korean Journal of Bronchoesophagology
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• v.1 no.1
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• pp.129-135
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• 1995

The superiorly based flap tracheostomy(SBFT) has been advocated as an new technique of tracheostomy to manage a wide variety of causes of upper airway obstruction. This technique has particular applicability in patients who require long term tracheostomy such as in bilateral vocal cord paralysis and severe obstructive sleep apnea. SBFT has numerous advantages such as shortening of the gap between the skin and trachea : construction of a self-sustaining tract ; circumferential mucocutaneous junction to reduce infection, granulation tissue, bleeding, and stenosis of the tract : avoidance of the laryngotracheal damage : easy placement of a tracheostomal stent to promote speech, coughing and swallowing. Most of all, this technique can reduces the suprastomal buckling by the support of the superiorly based tracheal flap, and thus prevents the stenosis of suprastomal airway. The disadvantage of SBFT is more time-consuming procedure than the conventional tracheostomy, A retrospective analysis of 8 patients undergoing SBFT between June, 1994 and March, 1995 in Dankook University Hospital was performed to present the surgical technique and com-plication rates. The average duration of follow up was 11 months. The complications were consisted of a wound infection and a sternal granulation. The other complications including wound dehiscence, tracheitis, pneumonia, tracheal granulation, sternal narrowing and subglottic stenosis were not experienced.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.196-203
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• 2008

Durability of geosynthetics for soil reinforcement is accounted for creep and creep rupture, installation damage and weathering, chemical and biological degradation. Among these, the long-term creep properties have been considered as the most important factors which are directly related to the failure of geosynthetic-reinforced soil(GRS). However, the creep test methods and strain limits are too various to compare the test results with each other. The most widely used test methods are conventional creep test, time-temperature superposition and stepped isothermal method as accelerated creep tests. Recently developed design guidelines recommend that creep-rupture curve be used to determine the creep reduction factor($RF_{CR}$) which is a conservative approach. In this study, the different creep test methods were compared and the creep reduction factors were estimated at different creep strain limits of 10% of total creep strain and creep rupture. In order to minimize the impact of creep strain to the GRS structures, the various creep reduction factors using different creep test methods should be investigated and then the most appropriated one should be selected for incorporating into the design.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.1073-1081
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• 2021

When firms have higher environmental performance, they can provide sustainable business that allows firms to build the value of credibility and ethics, higher reputation, higher productivity, and lower costs. The advantages of environmental responsibilities help firms to maintain their earnings level over a long-term period. This research aims to examine the effect of environmental performance on earnings persistence. Research samples include 413 manufacturing firms-years listed in the Indonesian Stock Exchange and the PROPER evaluation in 2013-2019. Environmental performance is measured by PROPER evaluation rating. The result shows that environmental performance has a positive effect on earnings persistence. The advantage of environmental responsibilities allows firms to enjoy performance sustainability and persistence in a long-term period, not only periodically. Also, the positive effect of environmental performance on earnings persistence occurs more in the environmentally sensitive industry than non-sensitive ones. Since an environmentally-sensitive industry brings more environmental damage, higher environmental performance is more valuable to provide sustainability. This research has limitations to use all the Indonesian Stock Exchange-listed firms since not all firms participate in the PROPER evaluation. This research implies firms' management should maintain earnings persistence and sustainability by implementing higher-quality environmental responsibility, especially for firms in an environmentally-sensitive industry.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.188-189
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• 2020

In the field of architecture, concrete and steel bars are the most common and popular combinations. The relationship between the two in a structure is a complementary good that increases in utility when consuming both materials at the same time. However, the combination of the two, which has been perceived as semi-permanent, often faces repairs or reconstruction without its lifespan reaching decades. There are a number of deterioration factors at work for the reason for this phenomenon. Among them, the neutralization of concrete in particular refers to the process in which calcium hydroxide inside concrete reacts with carbon dioxide and loses alkalinity, which creates a corrosive environment for rebars inside concrete, causing serious damage to concrete. In this study, we intend to use a multi-physical analysis program using finite element analysis method to analyze the degree of carbonation according to the internal temperature and concentration of carbon dioxide in concrete, thereby contributing to the prediction of long-term neutralization of concrete and the research related to measures for neutralization of concrete.

• Wind and Structures
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• v.36 no.6
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• pp.379-392
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• 2023

Structural health monitoring is used to ensure the well-being of civil structures by detecting damage and estimating deterioration. Wind flow applies external loads to high-rise buildings, with the horizontal force component of the wind causing structural displacements in high-rise buildings. This study proposes a deep learning-based predictive model for measuring lateral displacement response in high-rise buildings. The proposed long short-term memory model functions as a sequence generator to generate displacements on building floors depending on the displacement statistics collected on the top floor. The model was trained with wind-induced displacement data for the top floor of a high-rise building as input. The outcomes demonstrate that the model can forecast wind-induced displacement on the remaining floors of a building. Further, displacement was predicted for each floor of the high-rise buildings at wind flow angles of 0° and 45°. The proposed model accurately predicted a high-rise building model's story drift and lateral displacement. The outcomes of this proposed work are anticipated to serve as a guide for assessing the overall lateral displacement of high-rise buildings.

• Computers and Concrete
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• v.4 no.2
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• pp.101-117
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• 2007

A new model predicting the nonlinear basic creep behaviour of concrete structures subjected to high multi-axial stresses is proposed. It combines a model based on the thermodynamic framework of the elasto-plastic continuum damage theory for time-independent material behaviour and a rheological model describing phenomenologically the long-term delayed deformation. Strength increase due to ageing is regarded. The general 3D solution for the creep theory is derived from a rate-type form of the uniaxial formulation by the assumption of associated creep flow and a theorem of energy equivalence. The model is able to reproduce linear primary creep as well as secondary and tertiary creep stages under high compressive stresses. For concrete in tension a simple viscoelastic formulation is applied. The material law is then incorporated into a finite element solution procedure for analysis of reinforced concrete structures. Numerical examples of uniaxial creep tests and concrete members show excellent agreement with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.244-249
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• 2011

The potential hazards resulting from a low-velocity impact (bird-strike, tool drop, runway debris, etc.) on aircraft structures, such as engine nacelle or a leading edges, has been a long-term concern to the aircraft industry. Certification authorities require that exposed aircraft components must be tested to prove their capability to withstand low-velocity impact without suffering critical damage. In most of the past research studies unloaded specimens have been used for impact tests, however, in reality it is much more likely that a composite structure is exposed to a certain stress state when it is being impacted, which can have a significant effect on the impact performance. And the radiated impact sound induced by impact is analyzed for the damage detection evaluation. In this study, an investigation was undertaken to evaluate the effect in-plane loading on the impact force and sound of composite laminates numerically.

• Neonatal Medicine
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• v.15 no.1
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• pp.94-99
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• 2008

Although neonatal hypoglycemia is a common metabolic abnormality in newborn infants, brain injuries resulting from isolated neonatal hypoglycemia are rare. Many infants who are hypoglycemic do not exhibit clinical manifestations, while other infants are symptomatic and at risk for permanent brain damage. There is no disagreement that hypoglycemia can cause neonatal encephalopathy and result in permanent brain injury. Occipital brain injury associated with neonatal hypoglycemia can result in long-term disability, epilepsy, and visual impairment. Infants should receive ongoing developmental and visual surveillance for lateonset epilepsy, and visual or cognitive impairment. We report two cases of newborn infants with abnormal visual evoked potentials (VEP) caused by neonatal hypoglycemic encephalopathy.