• Tunnel and Underground Space
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• v.11 no.1
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• pp.30-35
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• 2001

Focusing on the bench length, this paper presents the results of 3-dimensional elafto-plastic FE Analysis un tunnels of full face, mini-bench and short bench excavated in weathered rock. Influences of unsupported span, horizontal to vertical stress ratio, thickness of shotcrete on the behavior of rock and support were a1so studied. Results showed that displacements of mini-bench tunnels responded more sensitively to bench lengths than those of short bench. The effects of bench excavation on upper half displacement increased with longer unsupported span. Horizontal to vertical stress ratio showed a greater influence on displacement and preceding displacement ratio or sidewall rather than those of crown and invert.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.192-204
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• 2011

In this study, 3-D analyses were conducted while taking every construction stage into account. Then 2-D analyses were conducted which yield the same results with the 3-D results. The crown settlement normalized by the ultimate value was compared during the process to overcome the discrepancy caused by different dimensions. When a bench or a core is left uncut to give extra support to the face and eventually the whole excavation boundary, this extra supporting effect also has to be included in the analysis. In this study, this effect is also implemented in terms of the load distribution factor. When the length of the bench is very short compared to the diameter of the tunnel in such cases as in short bench cut or in mini-bench cut, the supporting effect of the face does not disappear even after the bench is completely excavated and supported since the face is still too close to the point of interest. The 4th load distribution factor was defined to stand for the advance of the face after the completion of the excavation cycle. The 4th load distribution factor turned out to be very useful in determining the load distribution factors when a tunnel is excavated by bench cut with various bench lengths under different initial conditions.

• Venture DIGEST
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• s.71
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• pp.14-15
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• 2005

델 컴퓨터, 로레알, 월마트 등은 세계적으로도 손꼽히는 내로라하는 기업들이다. 과연 이들은 어떤 경영전략을 펼쳤기에 오늘날 글로벌 기업으로서 당당히 자리매김할 수 있었을까? 최근 KOTRA에서 발간한 <글로벌 기업의 경영전략에서 배운다>는 그 해답을 명쾌하게 제시하고 있다. 세계 50대 글로벌 기업의 경영전략을 꼼꼼히 조사, 분석한 이 보고서 내용을 벤치마킹한다면 우리나라 기업들도 세계시장으로 진출할 수 있는 길이 열릴 것이다.

• Explosives and Blasting
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• v.21 no.1
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• pp.19-27
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• 2003

국내 석회석 광산에서는 벤치 발파패턴을 현장의 KNOW-HOW에 따라 가장 경제저인 발파패턴을 적용하고 있다. 그러나 인건비 재료비등 제반경비가 상승함에 따라 좀 더 효율적인 발파방법의 개선이 요구되고 있는 바, 현 석회석 광산에서의 발파패턴을 보다 개선하여 경제적인 발파패턴을 적용하고, 그에 따른 고려해야 할 사항들을 본 논문에서 연구 하고자 한다. 따라서 국내 석회석 광산의 발파 패턴과 외국의 광산발파 패턴을 비교하고, 수치해석을 적용하여 기존의 발파 패턴에서 장약길이, 공간격, 장약량의 변화, 천공경은 102mm에서 115mm로 변화하고 장양방법을 단일장약에서 이중장약으로 변화하여 동해 쌍용자원에서 시험을 실시하였다. 연구 결과 장약길이의 20% 감소는 Power Factor를 (20%)낮게 하나, 파쇄효과는 28% 감소하고 Back Break가 (7%)이상 발생하였으며, 천공경을 115mm로 적용하고, 장약길이를 11% 감소를 위하여 이중장약을 적용하여 Power Factor를 10% 낮게 하였을 때 파쇄효과는 22.45%가 증대되었으며, 기존 동일 패턴에 Booster를 추가로 적용하였을 때 파쇄효과는 13.21% 가 증대되었고, Power Factor는 11% 가 감소되는 것을 알 수 있었다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.435-450
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• 2020

The divergence section of a double-deck tunnel can be divided into a 'widening pre-divergence section', a large cross-section with a cap shape and a 'post-divergence section' where the separation between the main and the branch tunnel is made. Since the cross-section of the widening pre-divergence section is considerably larger than that of the post-divergence section, the influence of excavation due to the different sizes and shapes in the cross-section should be considered in the examination of the tunnel stability. In this study, the effect of the preceding excavation, that is the excavation of the widening pre-divergence section, on excavation stability of the post-divergence section was examined by varying the excavation methods and bench lengths through 3D finite element analysis. The results showed that although the effects of the excavation methods and the bench lengths are not significant on the variation of principal stresses, the preceding excavation causes a relatively large variation on the stresses which may have an impact on the stability of the post-divergence section from the comparison of Stress-Strength Ratio (SSR) between the cases with and without the consideration of the preceding excavation effect by 2D finite element analysis.

• Tunnel and Underground Space
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• v.18 no.6
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• pp.427-435
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• 2008

In this paper, review was made for the excavation method and optimum bench length for unstable tunnel face in case of rock classification type V in order to make the best use of in-situ bearing capacity. 3D FEM analyses were performed to investigate the influences on the tunnel face and adjacent area with regard to the pattern and number of bolts when face bolts were used as a supplementary measure. As a result of this study, full section excavation method with sub-bench is effective in reducing the displacement greatly due to early section closure. Displacement-resistant effects in accordance with the bolting patterns are grid type, zig-zag type and then circular type in order of their effect. And horizontal extrusion displacement of tunnel face reduces as the number of bolts increase. A grid type face bolt covering $1.5m^2$ of tunnel face could secure the face stability in case of full section excavation method with sub-bench.

• Journal of Korea Port Economic Association
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• v.28 no.1
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• pp.53-82
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• 2012

The purpose of this paper is to show the clustering trend by using the context-dependent and measure-specific models for 38 Asian ports during 10 years(2001-2009) with 4 inputs and 1 output. The main empirical results of this paper are as follows. First, clustering results by using context-dependent and measure-specific models are same. Second, the most efficient clustering was shown among the Hong Kong, Singapore, Ningbo, Guangzhou, and Kaosiung ports. Third, Port Sultan Qaboos, Jeddah, and Aden ports showed the lowest level clustering. Fourth, ranking order of attractiveness is Guangzhou, Dubai, HongKong, Ningbo, and Shanghai, and the results of progressive scores confirmed that low level ports can increase their efficiency by benchmarking the upper level ports. Fifth, benchmark share showed that Dubai(birth length), and HongKong(port depth, total area, and no. of cranes) have affected the efficiency of the inefficient ports.

• Explosives and Blasting
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• v.19 no.4
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• pp.5-10
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• 2001

발파시 공벽 주변에서 방사상으로 발생하는 무수한 균열들을 제어하고 일정한 방향으로 절단면을 형성하기 위해서 split tube를 이용한 발파 방법에 대한 현장 실험을 실시하였다. 현장 실험결과 절단면을 발달시키고자 하는 방향으로 제어할 수 있었다. 계산에 의한 발파압력과 제어된 균열면의 길이를 비교하였다. 현장 벤치 벽면에서 에멀젼 계열 폭약의 발파 압력이 700㎫이상일 경우 균열을 원하는 방향으루 제어할 수 있었을 뿐만 아니라, 공경의 30배까지 균열이 전파되었다.

• Journal of Korea Port Economic Association
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• v.29 no.1
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• pp.143-175
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• 2013

The purpose of this paper is to show the clustering trend by using the variable group benchmarking(VGB) and categorical variable(CV) models for 38 Asian ports during 9 years(2001-2009) with 4 inputs(birth length, depth, total area, and number of crane) and 1 output(container TEU). The main empirical results of this paper are as follows. First, clustering results by using VGB show that Shanghai, Qingdao, and Ningbo ports took the core role for clustering. Second, CV analysis focusing on the container throughputs indicated that Singapore, Keelong, Dubai, and Kaosiung ports except Chinese ports are appeared as the center ports of clustering. Third, Aqaba, Dubai, Hongkong, Shanghai, Guangzhou, and Ningbo ports are recommended as the efficient ports for the target of clustering. Fourth, when the ports are classified by the regional location, Dubai, Khor Fakkan, Shanghai, Hongkong, Keelong, Ningbo, and Singapore ports are the core ports for clustering. On the whole, other ports located in Asia should be clustered to Dubai, Khor Fakkan, Shanghai, Hongkong, Ningbo, and Singapore ports. The policy implication of this paper is that Korean port policy planner should introduce the VGB model, and CV model for clustering among the international ports for enhancing the efficiency of inputs and outputs.

• Journal of KIISE:Software and Applications
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• v.30 no.3_4
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• pp.259-267
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• 2003

Though naive Bayes text classifiers are widely used because of its simplicity, the techniques for improving performances of these classifiers have been rarely studied. In this paper, we propose and evaluate some general and effective techniques for improving performance of the naive Bayes text classifier. We suggest document model based parameter estimation and document length normalization to alleviate the Problems in the traditional multinomial approach for text classification. In addition, Mutual-Information-weighted naive Bayes text classifier is proposed to increase the effect of highly informative words. Our techniques are evaluated on the Reuters21578 and 20 Newsgroups collections, and significant improvements are obtained over the existing multinomial naive Bayes approach.