• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.12
• /
• pp.829-838
• /
• 2022

This study conducts Hypervelocity Impact(HVI) simulations considering space objects with various shapes and different impact angles. A commercial nonlinear structural dynamics analysis code, LS-DYNA, is used for the present simulation study. The Smoothed Particle Hydrodynamic(SPH) method is applied to represent the impact phenomena with hypervelocity. Mie-Grüneisen Equation of State and Johnson-Cook material model are used to consider nonlinear structural behaviors of metallic materials. The space objects with various shapes are modeled as a sphere, cube, cylinder, and cone, respectively. The space structure is modeled as a thin plate(200 mm×200 mm×2 mm). HVI simulations are conducted when space objects with various shapes with 4.119 km/s collide with the space structures, and the impact phenomena such as a debris cloud are analyzed considering the space objects with various shapes having the same mass at the different impact angles of 0°, 30° and 45° between the space object and space structure. Although space objects have the same kinetic energy, different debris clouds are generated due to different shapes. In addition, it is investigated that the size of the debris cloud is decreased by impact angles.

• Journal of the Korean Electrochemical Society
• /
• v.26 no.3
• /
• pp.35-41
• /
• 2023

The carbon-coated silicon monoxide (c-SiO_x), which is a negative electrode active material for lithium-ion batteries (LIBs), has a limited cycle performance due to severe volume changes during cycles, despite its high specific capacity. In particular, the significant volume change of the active material can deform the electrode structure and easily damage the electron transfer pathway. To improve performance and mitigate electrode damage caused by volume changes, we replaced parts of the carbon black conducting agent with carbon nanotubes (CNTs) having a linear shape. The content of the entire conductive material in the electrode was fixed at 10% by mass, and the relative content of CNTs ranged from 0% to 25% by mass to prepare electrodes and evaluate electrochemical performance. As the CNT content in the electrode increased, both cycle life and rate capability improved. Even a small amount of CNT can significantly improve the electrochemical performance of a c-SiO_x negative electrode with large volume changes. Furthermore, dispersing CNTs effectively can lead to achieving the equivalent performance with a reduced quantity of CNTs.

• Journal of International Area Studies (JIAS)
• /
• v.16 no.2
• /
• pp.121-146
• /
• 2012

The purpose of this paper is to study on China's emergence and its influence on international society against the U.S. hegemony. Recently, China's influence has proliferated in Central Asia as well as East Asia at a rapid rate. China, through its soft balancing strategy, increased its influence in Central Asia in response to the U.S. power and behavior. This study analyzes the relationship among China and Central Asia with the view of soft balancing theory. In order to determine whether China's strategy on Central Asia is soft balancing, this paper presents three indicators: 1) Second-tier major power is willing to take a strategy that increase diplomatic cost of hegemony or counter the hegemony influence through using regional and global multilateral cooperation. 2) Second-tier major power is willing to not only increase its influence by strengthening regional economic cooperation, but also check the extension of the hegemony economic influence into its boundary. 3) Second-tier major power intends to prevent expanding hegemony military influence into the region through limited military cooperation and increasing military spending, and denying territory. This paper analyze China's multi-polar strategy, economic and energy cooperation with Central Asia countries, and the military and security cooperation with multilateral organizations such as SCO.

• Environmental and Resource Economics Review
• /
• v.31 no.4
• /
• pp.801-824
• /
• 2022

Recently, United Nations found that 38% of global carbon emissions are generated in the building sector, surpassing other industries (32%) and transportation (23%), and ESG is actively used as a way to reduce carbon emissions in the building sector, led by overseas advanced countries. In Korea, as the National Pension Service announced "Consider ESG with more than 50% of investment assets" this year, the move to introduce ESG in the building sector is accelerating, centering on construction companies and asset management companies. However, as the domestic ESG evaluation system is still mainly focused on corporate governance and social responsibility, interest in the environmental sector is lagging behind that of advanced countries. As ESG in the building sector is expected to grow rapidly over the next 10 years, I would like to suggest the following development directions. The first is the expansion of the incentive system. In order for the government to successfully implement policies related to ESG in the building sector, incentive system such as tax reduction and building standards should be expanded further than now in addition to negative systems such as rent restrictions and punishment taxes due to regulatory violations. Second, standardized ESG standards are established. Rather than creating an independent Korean ESG standard that is far from global standards, it is necessary to organize the common parts of global standards and evaluation methods and create and provide guidelines in the form of standard textbooks that can be used equally by all stakeholders. Third, it is an effort to link ESG in the building sector with Digital Transformation(DX). This is because actual energy savings and carbon emission reduction can be realized only when the operation method of the building sector, which is operated mainly by manpower, is digitalized and converted to an intelligent way.

• Korean Chemical Engineering Research
• /
• v.61 no.1
• /
• pp.80-88
• /
• 2023

Ensuring safety in the designing of manufacturing and handling facilities for low-density polyethylene (LDPE) is difficult because there are no standards for the dust explosion characteristics of LDPE. In this study, a dust explosion test was performed on two dust samples collected from a bag filter (LDPE 1) during the LDPE manufacturing process and sedimentary dust (LDPE 2) leaked outside a facility such as a silo, and the LDPE 2 explosion test results were summarized. Particle size analysis showed that the volume-based particle diameter (median) was 95.04 ㎛ and the number density was 0-1 ㎛. The maximum explosion pressure (P_max) was 6.6 bar, and the maximum rate of explosion pressure rise was 366 [bar/s] at 1500 g/m³. Accordingly, the dust explosion index (K_st) was 99.4 bar·m/s, which was confirmed as ST-1 grade. Moreover, the minimum ignition energy and minimum ignition temperature was 10 mJ and 450 ℃, respectively. Currently, manufacturing and handling design is based on the characteristic values of high-density polyethylene (HDPE). However, as the test results show that LDPE 2 dust has a higher risk than HDPE (particle diameter 61.6 ㎛), caution is required when using the HDPE design criteria in the LDPE manufacturing process.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.11
• /
• pp.87-98
• /
• 2007

For the quick rehabilitation of a fire-damaged tunnel structure, it is the most important procedure to investigate the fire-induced damaged zone rapidly. This study aims to propose a new drilling resistance testing method by which mechanical properties of tunnel concrete lining altered by high temperature can be estimated easily and continuously. Especially, it alms to derive the relationships to estimate mechanical properties of mortar and concrete materials from drilling parameters. To obtain the optimum testing condition, a series of drilling resistance tests were carried out for mortar specimens. When the rotation per minute of drill bit, tile penetration rate and the bit diameter were 1,300 rpm, 1.40 mm/sec, and 10 mm respectively, the deviation of measured drilling resistance forces was minimal. Under the optimum testing condition, the relationships between drilling resistance and mechanical properties of mortar specimens were shown to be very favorable. The concept of replacing a mean value of resistance farces measured during drilling with the resistance energy was proposed to consider the effects of randomly distributed aggregates inside a concrete material on drilling resistance. When the concept was applied to concrete materials, a favorable relationship between actual compressive strength and drilling resistance energy was also successfully derived.

• Journal of Convergence for Information Technology
• /
• v.12 no.3
• /
• pp.85-107
• /
• 2022

This study is to analyze the induced effect, network connectivity, and network visualization of the water transportation industry on the overall economy in relation to all industries. For this, various inducement coefficients of the water transportation industry are analyzed using industry linkage analysis and unit structure matrix, and network visualization analysis is performed using network connectivity and NetDraw using Ucinet 6 that utilizes unit structure matrix and inverse matrix function. As a result of the study, analysis results of input coefficient, production inducement coefficient, value-added inducement coefficient, and inter-industry chain effect were presented as various inducement coefficients in the water transportation industry. content was presented. Through this study, the current position and status of the water transportation industry and its relationship with all industries were confirmed, and the strategic relationship with which industries it should be presented was presented. In the future, it is necessary to further analyze the current status and trends of various induced effects, connectivity (centrality), and network visualization analysis using industry-related analysis published since the 2000s.

• The Journal of Engineering Geology
• /
• v.32 no.1
• /
• pp.59-72
• /
• 2022

This study employed a 3-D numerical analysis based on the distinct element method to estimate the strength and deformability of a Cretaceous biotite granitic rock mass at Gijang, Busan, Korea. A workflow was proposed to evaluate the scale effect and the representative elementary volume (REV) of mechanical properties for fractured rock masses. Directional strength and deformability parameters such as block strength, deformation modulus, shear modulus, and bulk modulus were estimated for a discrete fracture network (DFN) in a cubic block the size of the REV. The size of the mechanical REV for fractured rock masses in the study area was determined to be a 15 m cube. The mean block strength and mean deformation modulus of the DFN cube block were found to be 52.8% and 57.7% of the intact rock's strength and Young's modulus, respectively. A constitutive model was derived for the study area that describes the linear-elastic and orthotropic mechanical behavior of the rock mass. The model is expected to help evaluate the stability of tunnels and underground spaces through equivalent continuum analysis.

• The Journal of Engineering Geology
• /
• v.32 no.1
• /
• pp.41-57
• /
• 2022

A workflow is presented to estimate the size of a representative elementary volume and 3-D hydraulic conductivity tensor based on fluid flow analysis for a discrete fracture network (DFN). A case study is considered for a Cretaceous granitic rock mass at Gijang in Busan, Korea. The intensity and size of joints were calibrated using the first invariant of the fracture tensor for the 2-D DFN of the study area. Effective hydraulic apertures were obtained by analyzing the results of field packer tests. The representative elementary volume of the 2-D DFN was determined to be 20 m square by investigating the variations in the directional hydraulic conductivity for blocks of different sizes. The directional hydraulic conductivities calculated from the 2-D DFN exhibited strong anisotropy related to the hydraulic behavior of the study area. The 3-D hydraulic conductivity tensor for the fractured rock mass of the study area was estimated from the directional block conductivities of the 2-D DFN blocks generated for various directions in 3-D. The orientations of the principal components of the 3-D hydraulic conductivity tensor were found to be identical to those of delineated joint sets in the study area.

• Journal of the Korean Society of Floral Art and Design
• /
• no.40
• /
• pp.3-24
• /
• 2019

This study aim to suggest connective potential of eco-therapy in interior therapy for integrative psychotherapy. The study method was literature review on qualitative study. The study scope was ranged as the following three steps: 1) Literature review on integrative psychological therapy; 2) Discussion on therapy and ecology in interior design; and 3) Association between three aspects of integrative psychotherapy(emotion, cognition and behavior) and psychological phases of interviewee (quasi-consideration, consideration, preparation, behavior, and maintenance). The study results are summarized below: 1) Emotional aspect of integrative psychotherapy utilizes installing and sensory aspects of space. 2) Cognitive aspect of integrative psychotherapy utilizes energetic and installing aspects of space. 3) Behavioral aspect of integrative psychotherapy utilizes structural, installing, emotional, and purposive aspects of space. This study has its significance in extending collaborative concept of plants as the decoration to broad sense of eco-therapy available as the psychological factor in organic relationship between human and environment, which will be used as the resource for design therapy training program in the future.