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Classification of Ground Subsidence Factors for Prediction of Ground Subsidence Risk (GSR) (굴착공사 중 지반함몰 위험예측을 위한 지반함몰인자 분류)

  • Park, Jin Young;Jang, Eugene;Kim, Hak Joon;Ihm, Myeong Hyeok
    • The Journal of Engineering Geology
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    • v.27 no.2
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    • pp.153-164
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    • 2017
  • The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

Analysis of Elementary Teachers' Understanding Level and Actual State About Scientific Inquiry (초등교사의 과학적 탐구 이해의 수준과 실태 분석)

  • Lee, Dongseung;Park, Jongseok
    • Journal of the Korean Chemical Society
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    • v.63 no.4
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    • pp.280-288
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    • 2019
  • The purpose of this study is to draw implication for scientific inquiry study by investigating level of understanding and actual state regarding the elementary school teachers' scientific inquiry. The survey was conducted toward 42 elementary school teachers who work at the D city by using questionnaire of Views About Scientific Inquiry. Actual state of understanding of scientific inquiry was investigated by categorized the responses to the level of understanding of the eight aspects of scientific inquiry in three levels (informed, mixed, naive) based on analysis criteria. And analyze whether the characteristic of the subjects affect to level of understanding about aspect of scientific inquiry. As a result of the analysis, the two aspects among the eights aspects of scientific inquiry; 'Inquiry procedures are guided by the question asked' and 'Research conclusions must be consistent with the data collected' were appeared to have high rates of informed level of understanding. In the remaining six perspectives, most of elementary school teachers had naive and mixed level of understanding, so informed level of understanding took a relatively low proportion. It implies that elementary school teachers who teach inquiry in the field have limit to understand about scientific inquiry. These results indicated that experiences that have taught students and science related training courses that open sofar have a little influence to increase comprehension about scientific inquiry. Therefore, it is required to reinforce the teachers' understanding about scientific inquiry and to formulate different form of plan unlike existing way of teaching for teaching scientific inquiry.

Evaluation for Rehabilitation Countermeasures of Coal-mined Spoils and Denuded Lands (폐탄광지(廢炭鑛地)의 산림훼손지복구(山林毁損地復舊) 및 폐석유실방지대책(廢石流失防止對策)에 관한 연구(硏究))

  • Woo, Bo-Myeong
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.3 no.2
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    • pp.24-34
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    • 2000
  • The project for rehabilitation and revegetation of the abandoned coal-mine lands is a very important national environmental restoration project in the view point of rehabilitation and revegetation of denuded forest-lands caused by coal mining as well as restoration of disturbed natural environment and control of the variable pollutions. In Korea, because a large number of coal mines had been developed in order to fill up abundantly consumption of coal as a major energy source in the developing period, a lot of denuded forest-lands caused by coal mining had distributed in the whole country. And, due to the absence of effective rehabilitation and revegetation works on the denuded forestlands caused by coal-mining, most of them had been remained with being damaged. In 1990, area of the abandoned coal-mine lands, requiring the rehabilitation and revegetation works, was about 1,437.1 ha. For the past ten years ('90~'99), about 1,081.8 ha out of them had been rehabilitated and revegetated, and the rehabilitation planning area was about 33.0 ha in 2000. So, remaining area out of abandoned coal-mine lands will be about 322.3 ha after 2000. In principle, after abandoning coal-mine, mine owners must carry out the rehabilitation and revegetation works on the abandoned mine lands by themselves. But, most of mine owners were in financial difficulty after abandoning coal-mine, so that principle couldn't have obtained the desired effects. To solve this problem, from 1995, Coal Industry Promotion Board (CIPB) have carried out the rehabilitation and revegetation works on the abandoned coal-mine lands at government budgets, and they have obtained good results in the construction area. However, due to application of the "conventional erosion control measures and techniques" to the rehabilitation and revegetation measures on the abandoned coal-mine lands, the results and effects of the works excuted have not been successful. Therefore, unique measures and techniques for rehabilitation and revegetation of the abandoned coal-mine lands will have to be developed, especially including development of new techniques on the soil-dressing and soil-covering, seed spray and hydro-seeding measures with seed-fertilizer-soil materials as the mechanized measures, and using of new materials for the tree planting and seedling measures.

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Shear Strength of Interface between Natural Aggregate Concrete and Recycled Aggregate Concrete (천연골재 콘크리트와 순환골재 콘크리트 접합면의 전단강도)

  • Moon, Hoon;Choi, Ik-Je;Kim, Ji-Hyun;Chung, Chul-Woo;Kim, Young-Chan
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.8 no.1
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    • pp.26-32
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    • 2020
  • Concrete recycling is becoming mandatory rather selective due to depletion of constructional materials and increase of concrete waste. Studies on recycling concrete are conducted in various point of view for long time. However, standard or guideline of many countries for the application of recycled aggregate concrete(RAC) has restrictions such as low replacement rate of coarse aggregate and no fine aggregate allowed due to inferior material properties of recycled aggregate. This study intends to figure out the feasibility of casting natural aggregate concrete(NAC) and RAC separately in a structural member. In making RAC, replacement rate of coarse aggregate was 50, 100% in RAC and treatment of interface of two concretes is introduced. RAC treatment of recycled aggregate or inclusion of additives was not done as it can increase embodied energy of concrete work. Double-shear test with uniformly distributed loading was adopted to evaluate shear strength at the interface of two concretes. After curing it was hard to distinguish interface of two concretes. Experimental result revealed that specimen with higher replacement rate showed higher shear-to-compressive strength ratio, which is possibly attributed to coarse aggregate size and roughness of sheared section. Further study on the effect of various parameters is required and subsequent research activity is on-going.

Low-temperature synthesis of nc-Si/a-SiNx: H quantum dot thin films using RF/UHF high density PECVD plasmas

  • Yin, Yongyi;Sahu, B.B.;Lee, J.S.;Kim, H.R.;Han, Jeon G.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.341-341
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    • 2016
  • The discovery of light emission in nanostructured silicon has opened up new avenues of research in nano-silicon based devices. One such pathway is the application of silicon quantum dots in advanced photovoltaic and light emitting devices. Recently, there is increasing interest on the silicon quantum dots (c-Si QDs) films embedded in amorphous hydrogenated silicon-nitride dielectric matrix (a-SiNx: H), which are familiar as c-Si/a-SiNx:H QDs thin films. However, due to the limitation of the requirement of a very high deposition temperature along with post annealing and a low growth rate, extensive research are being undertaken to elevate these issues, for the point of view of applications, using plasma assisted deposition methods by using different plasma concepts. This work addresses about rapid growth and single step development of c-Si/a-SiNx:H QDs thin films deposited by RF (13.56 MHz) and ultra-high frequency (UHF ~ 320 MHz) low-pressure plasma processing of a mixture of silane (SiH4) and ammonia (NH3) gases diluted in hydrogen (H2) at a low growth temperature ($230^{\circ}C$). In the films the c-Si QDs of varying size, with an overall crystallinity of 60-80 %, are embedded in an a-SiNx: H matrix. The important result includes the formation of the tunable QD size of ~ 5-20 nm, having a thermodynamically favorable <220> crystallographic orientation, along with distinct signatures of the growth of ${\alpha}$-Si3N4 and ${\beta}$-Si3N4 components. Also, the roles of different plasma characteristics on the film properties are investigated using various plasma diagnostics and film analysis tools.

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A Study on Integrated Approaching Factors of Environmentally-Friendly Companies Certification Scheme and Environmental Impact Assessment of Korea (환경친화기업지정제도와 환경영향평가제도에서의 통합적 환경관리 요소에 대한 기초적 연구)

  • Hong, Jun-Suk;Kim, Kyu-Yeon;Kwon, Oh-Sang
    • Journal of Environmental Impact Assessment
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    • v.17 no.2
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    • pp.113-124
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    • 2008
  • A worldwide trend of permitting system for industrial installation to achieve a high level of protection of the environment has been moved from single media to multimedia in approach. The Council of the European Community issued the Directive 96/61/EC, the IPPC Directive, concerning integrated pollution prevention and control in 1996. The IPPC Directive is one of the most ambitious legal measures that the European Union (EU) has initiated with a view to applying the prevention principle for industrial activities. The IPPC aims to achieve the integrated prevention and reduction of environmental pollution emitted by those industrial installations with a higher potential of emissions to the environment. Organization for Economic Cooperation and Development (OECD) recommended on Environmental Performance Reviews of Korea in 2006 that IPPC permitting concept should be considered for large stationary sources at the national and regional levels. Any Korean law doesn't provide for integrated pollution control with a single process covering all pollution from economic activities. However, one exception might be the "environmentally-friendly companies" certification scheme, introduced in 1995, in which participants agree to meet targets beyond the legal emission limit values in exchange for government technical and financial support to operate environmental management systems. The other exception might be Environmental impact assessment (EIA) of projects, in 1977, which has been strengthened and reinforced to be more preventive through development of the prior environmental review system (PERS) in 1999. The aim of this work is to introduce the contents of IPPC Directive at the viewpoint of Korea policy and to survey the integrated approaching concept of Environmentally-Friendly Companies (EFC) Certification Scheme and EIA policy of Korea. The study will be helpful in the future to prepare the infrastructure of integrated permitting system and to enforce the integrated permit which the authorities of local government issues on industrial activities. It can be said that the data calculated through both EFC Certification Scheme and EIA will be discussed as worthful information to determine Korean BAT reference notes for integrated permitting process.

Machinability investigation and sustainability assessment in FDHT with coated ceramic tool

  • Panda, Asutosh;Das, Sudhansu Ranjan;Dhupal, Debabrata
    • Steel and Composite Structures
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    • v.34 no.5
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    • pp.681-698
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    • 2020
  • The paper addresses contribution to the modeling and optimization of major machinability parameters (cutting force, surface roughness, and tool wear) in finish dry hard turning (FDHT) for machinability evaluation of hardened AISI grade die steel D3 with PVD-TiN coated (Al2O3-TiCN) mixed ceramic tool insert. The turning trials are performed based on Taguchi's L18 orthogonal array design of experiments for the development of regression model as well as adequate model prediction by considering tool approach angle, nose radius, cutting speed, feed rate, and depth of cut as major machining parameters. The models or correlations are developed by employing multiple regression analysis (MRA). In addition, statistical technique (response surface methodology) followed by computational approaches (genetic algorithm and particle swarm optimization) have been employed for multiple response optimization. Thereafter, the effectiveness of proposed three (RSM, GA, PSO) optimization techniques are evaluated by confirmation test and subsequently the best optimization results have been used for estimation of energy consumption which includes savings of carbon footprint towards green machining and for tool life estimation followed by cost analysis to justify the economic feasibility of PVD-TiN coated Al2O3+TiCN mixed ceramic tool in FDHT operation. Finally, estimation of energy savings, economic analysis, and sustainability assessment are performed by employing carbon footprint analysis, Gilbert approach, and Pugh matrix, respectively. Novelty aspects, the present work: (i) contributes to practical industrial application of finish hard turning for the shaft and die makers to select the optimum cutting conditions in a range of hardness of 45-60 HRC, (ii) demonstrates the replacement of expensive, time-consuming conventional cylindrical grinding process and proposes the alternative of costlier CBN tool by utilizing ceramic tool in hard turning processes considering technological, economical and ecological aspects, which are helpful and efficient from industrial point of view, (iii) provides environment friendliness, cleaner production for machining of hardened steels, (iv) helps to improve the desirable machinability characteristics, and (v) serves as a knowledge for the development of a common language for sustainable manufacturing in both research field and industrial practice.

An Empirical Study on the Strategic Alternative for the Internationalization of Korean Ventures - Based on the Theories of International Entrepreneurship and Effectuation - (한국 벤처기업의 국제화를 위한 전략적 대안에 대한 실증분석 - 국제적 창업가정신과 실현화 이론을 중심으로 -)

  • Lee, Giwhan;Bang, Hoyeol
    • International Commerce and Information Review
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    • v.15 no.2
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    • pp.129-162
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    • 2013
  • The purpose of this work is to explore the role of international entrepreneurship(IE) in explaining internationalization process of Korean ventures and to structure the model of IE with the logics of effectuation. The internationalization of entrepreneurial company is regarded as the realization of entrepreneurship which find out and use opportunities across borders in this point of view, and the realization process gets more realistic and applicable to the internationalization of ventures by effectuation. So we constructed the new concepts of the generating-internationalization-outcome capability(GIOC), which is the effectual capability allowing ventures to go international despite their lack of internal resources and experiences. Its sub-capabilities of GIOC are extemporaneous coping capability, perform-resource-in-hand capability and network-use capability. The empirical analyses of the relations among the capabilities and the performances of internationalization are performed in order to prove the rationale of the model, which provides finally significant evidences of the relationships. The key contribution of this study is that it highlights the important role of IE in internationalization of ventures and shows the possible role of effectuation in explaining the realization process of IE.

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Habitat Characteristics and Distribution of Cymbidium kanran Native to Jejudo, Korea (제주한란의 자생환경 특성 및 분포에 관한 연구)

  • Lee, Jong Suk
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.1
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    • pp.40-49
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    • 2004
  • This work carried out to define the characteristic of Cymbidium kanran habitat at Mt. Halla in Jejudo, Korea from the ecological point of view including geological and topographical features, air and soil temperature, relative humidity, fluctuations of light intensity, habitat vegetation, distribution altitude, area limit, and etc. And another goal of this study consider the conservation counterplan of the cymbidium habitat. Natural distribution areas of the cymbidium were observed more abundantly on the well drained south and east-facing slopes. Soil acidity was ranged from pH 4.1 to 5.3, and electric conductivity was ranged from 176.4 to 299.9 us/cm (average 215.3 us/cm). Base-saturation percentage of the habitat soil was below 50%, bulk density 0.42g/$cm^2$, particle density 2.05g/$cm^2$, humus content 26%, total nitrogen 0.82%, available phosphate 4.2 mg/kg, exchangeable potassium 0.63 Cmol/kg, calcium 0.44 Cmol/kg and magnesium 0.67 Cmol/kg. Annual mean air temperature was $15.4^{\circ}C$, however, air temperature was ranged $11.7{\sim}18.2^{\circ}C$ in spring, $21.2{\sim}23.8^{\circ}C$ in summer, $12.8{\sim}22.0^{\circ}C$ in fall and $5.5{\sim}7.8^{\circ}C$ in winter season. Annual mean soil temperature at depth of 10cm was $13.2^{\circ}C$ And minimum value was recorded $4.7^{\circ}C$ on January, and maximum value $22.5^{\circ}C$ on August. Relative humidity was ranged 90.8~94.7% in summer, 80.8~91.5% in fall and 77.6~84.2% in winter season. Minimum value was 56.5% on December, and maximum value was 100% on July and August. Light intensities were ranged from 400 to 1,800 lux at the greater part of Cymbidium kanran sites in Jejudo. Summer regarded as an lower light intensities was recorded to be range of 500~600 lux; however, autumn and winter were shown higher light regimes ranged from 3,500 to 3,800 lux. Therefore, one must be suprised that the cymbidium grow at the light condition of 6 lux (minimum) or 10,000 lux (maximum). Tree species keeping higher frequency rate and density were Eurya japonica, Camellia japonica, Castanopsis cuspidata, Carpinus laxiflora and Pinus densiflora. Number of trees growing in a 5${\times}$5m quardrat was 35 as an average, and proportion of evergreen versus deciduous was 5:1. Distribution altitude of the orchid habitat was ranged from 120m (low) to 840m (high) from sea level on the south facing slope of Mt. Halla, and was ranged eastern borderline of Gujwaup, Bukjejugun to western boundaries of Jungmundong, Seogwipo city. For the stable conservation of Cymbidium kanran habitat, sunlight regimes must be increased more by means of cutting trees or twigs in the site.

Phase Behavior of Simvastatin Drug in Mixtures of Dichloromethane and Supercritical Carbon Dioxide and Microparticle Formation of Simvastatin Drug Usins Supercritical Anti-Solvent Process (디클로로메탄과 초임계 이산화탄소의 혼합용매에서 Simvastatin 약물의 상거동과 초임계 역용매 공정을 이용한 Simvastatin 약물 미세입자의 제조)

  • Oh, Dong-Joon;Lee, Byung-Chul
    • Clean Technology
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    • v.13 no.1 s.36
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    • pp.34-45
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    • 2007
  • Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dichloromethane and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing dichloromethane as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of dichloromethane and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the dichloromethane composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature. The second half of this work is focused on the particle formation of the simvastatin drug by a supercritical anti-solvent recrystallization process in a cylindrical high-pressure vessel equipped with an impeller. Microparticles of the simvastatin drug were prepared as functions of pressure (8 MPa to 12 MPa), temperature (303.15 K, 313,15 K), feed flow rate of carbon dioxide, and stirring speed (up to 3000 rpm), in order to observe the effect of those process parameters on the size and shape of the drug microparticles recrystallized.

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