• Korean Journal of Mineralogy and Petrology
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• v.36 no.2
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• pp.135-145
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• 2023

Aggregate is used to produce stable materials like concrete and asphalt and is fundamental to meet the social needs of housing, industry, road, energy and health. A total of 42.35 billion tons of aggregate were produced in 2021 worldwide, an increase of 0.91% compared to the previous year. Among them, 2 billion tons were produced in China, India, European Union and United States, making up to 71.75% of the share. South Korea has witnessed a constant increase in aggregate production, overtaking Mexico and Japan for seventh place with 390 million tons and 0.85% of the share. The industrial sand and gravel produced globally amounted to 352.66 million tons. The top seven countries with the highest production were China, United States, Netherlands, Italy, India, Turkey and France, and their production exceeded 10 million tons and held a share of 74.69%. Exports of natural rock recorded $21.68 billion in 2021, increased by $2.3 billion compared to the previous year, while exports of artificial rock increased by $2.66 billion to $13.59 billion. Exports of sand reached $1.71 billion with United States, Netherlands, Germany and Belgium being the four countries with the highest exports of sand. The four countries exported more than $100 million in sand and took up 57.70% of the total amount. Exports of gravel totaled $2.75 billion, with China, Norway, Germany, Belgium, France and Austria in the lead, making up to 48.30% of the total share. The aggregate quarry started to surge in the 1950s due to the change in people's lifestyle such as population growth, urbanization and infrastructure delvelopment. Demand for aggregate is also skyrocketing to prevent land reclamation and flood caused by sea-level rise. Demand for aggregate, which was around 24 gigatons in 2011, is expected to double to 55 gigatons in 2060. However, it is likely that aggregate extraction will heavily damage the ecosystem and the world will eventually face a shortage of aggregate followed by tense social conflict.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.704-723
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• 2000

This study was undertaken to evaluate the tensile bond strength of In-Ceram alumina core treat-ed by ion assisted reaction(IAR). Ion assisted reaction is a prospective surface modification technique without damage by a keV low energy ion beam irradiation in reactive gas environments or reactive ion itself. 120 In-Ceram specimens were fabricated according to manufacturer's directions and divided into six groups by surface treatment methods of In-Ceram alumina core. SD group(control group): sandblasting SL group: sandblasting + silane treatment SC group: sandblasting + Siloc treatment IAR I group: sandblasting + Ion assisted reaction with argon ion and oxygen gas IAR II group: sandblasting + Ion assisted reaction with oxygen ion and oxygen gas IAR III group: sandblasting + Ion assisted reaction with oxygen ion only For measuring of tensile bond strength, pairs of specimens within a group were bonded with Panavia 21 resin cement using special device secured that the film thickness was $80{\mu}m$. The results of tensile strength were statistically analyzed with the SPSS release version 8.0 programs. Physical change like surface roughness of In-Ceram alumina core treated by ion assistad reaction was evaluated by Contact Angle Measurement, Scanning Electron Microscopy, Atomic Force Microscopy; chemical surface change was evaluated by X-ray Photoelectron Spectroscopy. The results as follows: 1. In tensile bond strength, there were no statistically significant differences with SC group, IAR groups and SL group except control group(P<0.05). 2. Contact angle measurement showed that wettability of In-Ceram alumina core was enhanced after IAR treatment. 3. SEM and AFM showed that surface roughness of In-Ceram alumina core was not changed after IAR treatment. 4. XPS showed that IAR treatment of In-Ceram alumina core was enabled to create a new functional layer. A keV IAR treatment of In-Ceram alumina core could enhanced tensile bond strength with resin cement. In the future, this ion assisted reaction may be used effectively in various dental materials as well as in In-Ceram to promote the bond strength to natural tooth structure.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.329-338
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• 2010

The foundation area for tram contains biotite gneiss, quartzo-feldspathic gneiss, calc-silicate rock, and porphyroblastic gneiss of the pre-Cambrian Kyeonggi gneiss complex. These rocks record at least three stages of deformation, as indicated by fold sets of contrasting orientations (D1-D3). Joints are generally steeply dipping and strike NW-SE to WNW-ESE. The Gonjiam Fault, which strikes WNW-ESE, follows a river in the area. The fault possesses a 3-m-wide fracture zone, a 10-m-wide damage zone, and is 15 km long. Two tunnels have been constructed through the biotite gneiss. The geometric relationship between discontinuities (e.g., joints and foliation) and tunneling direction reveals that set 3 of the AA tunnel is unstable but that BB tunnel is relatively safe.

• Journal of Conservation Science
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• v.30 no.4
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• pp.427-438
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• 2014

To measure the depth and extension on the surface cracks of the stone monument, ultrasonic pulse velocity targeted at the Mulgyeseowon Stele in Changnyeong was used in this research. Additionally, to establish a long-term countermeasure of management and conservation for this stele, we have investigated the material properties and damage on it and have conducted a precise diagnosis by a variety of non-destructive techniques. Our research has revealed that stones of the stele are composed mainly of three rock types according to the parts of it, alkali-feldspar granite, gabbro and diorite. The result of the deterioration evaluation has occurred that cracks, which are observed from every direction in the body of the stele, are the significant factors to reduce structural stability. The ultrasonic velocity for an evaluation on the properties of the stele has revealed that the speed was high in the order of body, pedestal and crown. Furthermore, to understand the present condition and occurrences of the cracks which have measured in many different forms on the stele quantitatively, we have estimated from 0.6 to 24.1cm deep of the cracks by To-Tc method using ultrasonic velocity.

• Journal of the Korean earth science society
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• v.28 no.2
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• pp.202-213
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• 2007

The Odaesan earthquake $(M_L=4.8)$ occurred near Mt. Odae, Jinbu-Myon, Pyongchang-Gun, Kangwon Province on January 20, 2007. It has a shallow focal depth about 10 km. Its felt area covers most of the southern peninsula except some southern and western inland area. The maximum MM intensity was VI in the areas including Jinbu, Doam, Kangreung, Jumunjin, and Pyongchang. In these areas, there was a very strong shaking that caused several cracks on the walls of buildings and houses, slates falling off the roof, tiles being off the wall, things falling off the desk, and rock falling from the mountains. In order to get fault plane solutions, grid searches were performed by fitting distributions of P-wave first-motion polarities and SH/P amplitude ratios for each event. The results showed that the main shock represented right-lateral strike-slip sense and two aftershocks, reverse sense. It seems that the seismogenic fault may be the NNE-SSW trending Weoljeongsa fault near the epicenter based on the distribution of epicenters (foreshock, main shock, and aftershocks), damage area, and fault plane solution. The distribution of the epicenters indicates that the length of the subsurface rupture is estimated to be about 2 km.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.243-249
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• 2018

Excessive tooth wear results in unacceptable damage to the occlusal surface and can cause pulpitis, occlusal disharmony, dysfunction, and unesthetic result. Patients with severe attrition have to be classified as several types relative to the vertical dimension of occlusion (VDO) and the interocclusal distance for the prosthetic space. The patient in this case was a 80 - year - old woman who lost support of posterior occlusion and collapsed of the occlusal plane due to confrontation of the opposing teeth, accompanied by an increase in the number of remaining bristles, resulting in a loss of intermaxillary space for prosthesis. In this case, treatment with increased vertical dimension may have stability if the increase in vertical occlusal height is minimized within the required range, and a stable occlusal contact is provided after an increased vertical occlusal height stabilization period. After the new VDO had been confirmed under interim fixed restorations, definitive fixed restorations were produced. Through these treatment processes, we obtain satisfactory results that are functional and aesthetically pleasing.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.4
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• pp.59-69
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• 2007

The scale of a natural disaster grows bigger and bigger every year. The government spends much of its budget on recovering the resulting damage on a national scale. It is important to shift the paradigm from taking measures after a disaster to that of taking preventive actions before a disaster in order to bring a fundamental resolution to such problems. In taking preventive actions and policies, it is necessary to integrate various kinds of advanced technologies including IT, high-tech information gathering technology and operational technology, and to predict and evaluate natural disasters on a comprehensive level. Although Korea is a country with a strong IT sector, most information gathering is still performed in paper. In particular, information about the areas of previous landslide occurrences and slopes remains on paper, which makes it difficult to share the information and to discern the contents, and also raises the possibility of missing documents. Thus this study set out to develop an information gathering and management system for cutting slopes using PDA from the perspective of information gathering, system compatibility, and information management. As a result, field information may be gathered in a variety of forms (location, photos, and texts) real-time. A rough judgment was also made of the stability of rock slopes using the SMR method on the field.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.166-172
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• 1997

In order to exterminate effectively starfish, Asterias amurensis inhabited a village fishing grounds and shellfish farms on coast of Korea, Mop and sledge gear were made and sea trials for capture efficiency of starfish by each gear and towing distance were carried out by commercial dredger on the coast of Keojedo from April to May in 1995. As Starfish mop and sledge were slowly dragged over the bottom at the same time, starfish became entangled in bunches of twine and netting respectively. The gears were hauled up at intervals to remove the starfish and hand-picking operations on vessel were conducted. The results obtained are as follows : Two gears were smoothly slidden over the sea bottom and captured numerous starfish. The optimal towing distance by each gear was 300 to 500 m.The capture efficiency of starfish species by sledge was 57% compared with 43% of that by mop but mixed rate with fish or shellfish of the former was 21 times as high as that of the letter. It was concluded from sea trials that moping was effective in shellfish farms, because the mop outfit causes little damage to useful shellfishes and the mixture of starfish with fish or shellfish was low, whereas sledging can be used to clean uncultivated areas free of shellfish where starfish population is very heavy and common fishing grounds in which bottom material is rock or gravel.

• Journal of the Korean GEO-environmental Society
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• v.17 no.12
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• pp.35-43
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• 2016

With the development of construction technology, constructions of dam and levee (dike) as well as the environmental problems are becoming issues. Recently, many countries have tried to develop and used CSG (Cemented Sand and Gravel), which needs fewer requirements than others in aggregates, constructability and ground condition during the dam construction. Mixing up with small amount of cement, CSG is able to increase the strength and proceed accelerated construction without artificial gradation adjustment of riverbed aggregate and crushed rock on construction site. Thus, CSG can minimize environmental damage resulted from quarries mining and reduce cost of construction. Unlike heat of hydration condition that regular concrete usually met, CSG exposes to repeated dry-wet and freezing and thawing environment. Thus, consider the importance of structure of dam or levee, intensive study on the durability of CSG is needed. In this study, freezing and thawing experiment was carried out to evaluate the durability of CSG. In results, the durability factor of CSG is 30~40 or >40 when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. The unconfined compressive strength is reduced to 30~50% or 40~70% when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. Taken together, the strength and durability of CSG is reliable when the amount of cement is over $0.8kN/m^3$.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.2
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• pp.23-33
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• 2011

In this study, a CFPBS (Cone-type Friction Pendulum Bearing System) was developed which controls the acceleration delivered to the structure to prevent damage and degradation of the critical communication equipment in case of an earthquake. The isolation performance of the CFPBS was evaluated by numerical analysis. The CFPBS was manufactured in the shape of a cone differenced from the existing FPS (Friction Pendulum System), and a pattern was engraved on the friction surface. The natural frequencies of the CFPBS were evaluated from a free-vibration test with the seismic isolator system consisting of four CFPBSs. In order to verify its earthquake-resistant performance, a numerical analysis program was created from the equation of the CFPBS induced from the equations of motion. A simplified theoretical equation of the CFPBS was proposed to manufacture the equipment which could demonstrate the necessary performance. Artificial seismic waves satisfying the maximum earthquake scale of the Korean Building Code-Structural (KBC-2005) were created and verified to review the earthquake-resistant performance of the CFPBS by numerical analysis. The superstructural mass of the CFPBS and skew angle of the friction surface were considered for numerical analysis with El Centro NS (1940), Kobe NS (1995) and artificial seismic waves. The CFPBS isolation performance evaluation was based on the results of numerical analysis and the executed comparative analysis between the results from numerical analysis and the simplified theoretical equation under the same conditions.