• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.433-441
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• 2004

국내 발파 현장에서 사용되고 있는 폭약류에 강력한 폭굉력을 충분하게 발휘하기 위해서는 뇌관(Blasting cap, Detonator)의 역할이 중요하다. 그리고 이 뇌관의 정밀성에 따라 발파 효율의 차이가 있게된다. 초기의 도화선 및 공업뇌관에서 시작하여 현재 정밀성 면에서는 MS(Milli Second)뇌관의 경우 20ms또는 25ms의 정밀한 시차로 순차적으로 기폭함으로써 발파효과의 극대화와 소음 및 진동제어에 큰 효과를 이루었으나, 최근 개발된 진자뇌관의 경우 자체 IC회로를 내징하여 $1{\sim}2ms$의 초정밀시차(오차범위 $0.1{\sim}0.2ms$이내)의 구현이 가능해짐에 따라 이를 적절히 조합하여 설계함으로써 각종 제어발파, 파쇄도 향상, 암손상영역 저감 등의 효과에 대해 국외에서 연구가 진행되고 있는 것으로 알려지고 있다. 그러나 우리나라와 같이 도심지 발파 및 터널이나 노천 현장 근거리에 보안물건이 위치해 있어 진동제어가 절실히 필요한 상황에서 진동제어에 효과가 있는 것으로 알려진 전자뇌관에 대한 연구가 이루어지고 있지 않은 상황에서 본 연구는 앞으로 이루어질 전사뇌관에 대한 수많은 연구에 기초자료를 제공하고자 실시하였다. 본 연구에서는 이를 위해 국내에서 최초로 2003년 9월 23일 강원도 양구 지역읜 00터널에 전자뇌관을 이용한 시험발파를 실시하였고, 발파에 의한 진동 등을 조사하여 그 효율성을 검토하였다. 이를 위해 전자뇌관의 특성과 장점을 최대한 살리기 위하여 각공을 발파하는 방식, 즉 1지발에 1공을 발파하는 방식을 채택하고 비전기 뇌관과 전자뇌관으로 설계를 하여 각각의 발파효율을 비교하여 보았다. 그 결과 발파신동의 경우 비전기뇌관을 이용하여 1공씩을 1지발로 발파를 한 경우에는 18${\sim}$56%의 진동저감 효과가 있었고, 번 설계에 의해 진해오딘 발파에 비하여는 최대 70% 이상의 진동저감 효과가 있는 것으로 나타났다.

• Explosives and Blasting
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• v.26 no.2
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• pp.29-37
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• 2008

In general, the size of tunnel cross section in construction site is $50{\sim}200m^2$. But, electric cable tunnel, telecommunication cable tunnel, mine tunnel. Waterproof tunnel have small cross section less than $20m^2$. There are so many problem at small sectional tunnel: restriction of equipment, dead pressure by precompression, loss of efficiency, increase of work time. Especially, explosives remainder by precompression of previous detonation is serious problem. To find its measures of dead pressure (explosives remainder), the following series of progress have been conducted: (1) survey of previous study (2) investigate causes of dead pressure (3) set up of its measures (4) application and appraisal at tunnel site. The measures, change of cut pattern, hole space over 40cm, adjustment of delay time, are proved by experimental results.

• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.35-44
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• 2005

Recently, underground cavities such as limestone cavity and abandoned mine give rise to a lot of damage in SOC facilities. But there are many difficult problems such as delay of the working terms and enormous economic losses in finding a new method and changing construction design. In this study, a new filling material for underground cavities was developed using the stone-dust classified as industry waste polluting environment. As a result of test, filling material properties was that a compressive strength was $34{\~}60\;kgf/cm^2$, a change ratio in length was $0.268{\~}0.776\%$ and water absorption was $34.3{\~}46.9\%$. Also as a result of suspended mass test and pH test, it was confirmed that the developed filling material has a characteristic of non-separating in water and it was an environmentally friendly material.

• Explosives and Blasting
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• v.17 no.1
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• pp.27-55
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• 1999

The excavation works for deep foundation in urban areas have recently increased complaints of blasting vibration and settlement of ground level. Foundation must be excavated approximately up to 24-28m depths from the surface. The roads and subway line pass through the excavation area. The Dae-chung station is also located at the nearest distance 5-35m from the working site. To protect subway station and adjacient some structures from blasting and settlement, the level of ground vibration, displacements and stress were monitored and analyzed. The results can be summarized as follows ; 1. An empirical particle velocity equation were obtained by test blasts at Nassan Missi 860 Office tel construction site. $V{\;}={\;}K(D/\sqrt{W})^{-n}$, where the values for n and k are estimated tobe 0.371 and 1.551. From this ground vibration equation, the max. charge weight per delay time against distance from blasting point is calculated. Detailed blasting method is also presented. 2. To measure the horizontal displacement in directions perpendicular to the borehole axis, 6 inclinometers installed around working sites. The displacement at the begining was comparatively high because the installation of struts was delayed, but after its installation the values showed a stable trend. Among them, the displacement by 3 inclinometers installed on a temporary parking area showed comparatively high values, for example, the displacement measured at hole No. IC-l recoded the max. 47.04mm for 6 months and at hole No. IC-2 recorded the max. 57.33mm for 7 months. So, all of these data was estimated below a safe standard value 103mm. 3. Seven strain gauge meter was installed of measure the magnitude and change of stress acted on structs. The measured value of maximum stress was $-465{\;}kgf/\textrm{cm}^2,{\;}-338.4{\;}kgf/\textrm{cm}^2,{\;}302.3{\;}kgf/\textrm{cm}^2$ respectively. In compareto the allowable stress level of steel, they are estimated to be safe.

• Explosives and Blasting
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• v.35 no.4
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• pp.36-47
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• 2017

Due to civil complaints on vibrations and noises arising from blasting, mechanical excavation has been widely used for tunneling rather than the method of blasting, especially in the case of being in a close-proximity of 10M-20M range to a safety-thing. However, mechanical excavation, though less, it does increase the cost of whole construction project as the period of excavation is much prolonged from lack of constructability. This study aims to research and develop an effective blasting method that can ensure the constructability of shortened excavation period whilst not compromising the safety of the safety-things in a proximity to the blasting site by using a combination of an electronic detonator that can accurately control its delay period and a Low Vibration Explosives(LoVEX) that is effective on vibration control.

• Fire Science and Engineering
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• v.25 no.4
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• pp.1-7
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• 2011

Recently the interest in disaster prevention on super tall buildings is increasing. Especially in fire, against increasing of evacuation time due to high-rise, It is being tried to minimize the fire spread in building. Fire compartments using the fire-resistant wall and door, typical method to control the fire spread in buildings, delay the fire spread to other compartments and consequently evacuation time increases. But the existing provisions adjure only 2-hour fire resistance with maximum limit regardless of the super tall buildings, so this is a obstacle for research and development of the fire resistance wall in super tall buildings. In this study, we reviewed the fire resistance ratings of the wall, and presented the development directions for the fire resistance wall in super tall buildings considering fire resistance, construction and application of the wall.

• Journal of Korean Society of Transportation
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• v.29 no.5
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• pp.79-89
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• 2011

Though many studies regarding roundabout have been recently conducted, most of them have focused on operational aspect. Moreover, majority of the previous researches analyzes operational effects of single roundabout, but seldom investigate the effects of multi-roundabouts constructed on road networks. In this study, we seek ways to construct multiple roundabouts on road network maximizing their operational effects. The analysis investigate influence of both adjacent signalized and unsignalized intersections as well as influence of the distance from those intersections to roundabouts. The results show that the optimal distance between two adjacent intersections were calculated to be 150m, and any two intersections located within 150m apart influence each other thus imposing operational restrictions on each other. In addition, those results are confirmed using simulation analysis conducted on the real urban network in Nonheon regional area, Incheon City.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.377-385
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• 2010

In this paper, we propose a SInk-initiated geographic Multicast (SIM) protocol to reduce frequent location updates from mobile sinks to a source and to achieve fast multicast tree construction and data delivery. The proposed protocol allows sinks to construct their own data delivery paths to a source node and a multicast tree to be atomically constructed by merging the paths. Then, the source forwards data to the destinations down the multicast tree. This paper also propose a round-based virtual infrastructure with a radial shape for increasing the merging probability of data delivery paths and reducing reconstruction ratio of the multicast tree due to mobility of sinks. Simulation results show that the proposed protocol is superior to previous SOurce-initiated geographic Multicast (SOM) protocols in term of average data delivery delay and average energy consumption.

• Journal of the Korea Society of Computer and Information
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• v.17 no.3
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• pp.1-10
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• 2012

A low-complexity Multiplication over GF(2m) and multiplier circuit has been proposed by using cyclic-shift coefficients and the irreducible trinomial. The proposed circuit has the parallel input/output architecture and shows the lower-complexity than others with the characteristics of the cyclic-shift coefficients and the irreducible trinomial modular computation. The proposed multiplier is composed of $2m^2$ 2-input AND gates and m (m+2) 2-input XOR gates without the memories and switches. And the minimum propagation delay is $T_A+(2+{\lceil}log_2m{\rceil})T_X$. The Proposed circuit architecture is well suited to VLSI implementation because it is simple, regular and modular.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.61
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• pp.273-302
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• 2014

Project finance ("PF") is a method of raising long-term debt financing based on lending against the cash flow generated by the project alone. Project finance is a nonrecourse or limited recourse financing structure against the sponsors(or the investors). The debt terms in a project finance are not based on the creditor's credit support or on the value of the assets of the project. Lenders rely on the future cash flow to be generated by the project for debt repayment and interest, rather than the value of the project or the credit ratings of the sponsors. The non-recourse or limited recourse financing usually prompt potential project finance lenders to assess carefully all possible risks that might arise in a project to ensure that those risks are mitigated and controlled. In this respect, project finance is a opposite financing method of corporate finance. Project finance has rapidly grown over the last 20 years due to the worldwide process of privatization of public sector and development of natural resources. Global project finance volume reached the record USD 406.5 billion in 2011. In 2012, however, Global project finance volume dropped 6% to USD 382.3 billion. Infrastructure overtook Energy to lead all sectors with USD 113.6 billion. It is generally recognized that there are more and higher risks in project finance compared with corporate finance. Project finance is exposed to commercial risks as well as political risks. The main commercial risks are completion risks, environmental risks, operating risks, input supply risks, revenue risks, etc, and the main political risks are currency convertibility and transfer risks, expropriation risks, war and civil disturbance risks, risks of breach of government concession agreement, etc. Completion risks include permits risks, risks relating to the EPC Contractor, construction cost overrun, delay in completion, inadequate performance on completion, etc.