• 한국건축시공학회지
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• 제6권2호
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• pp.91-98
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• 2006

The purpose of this study is to investigate the problem of crack repair materials and methods in existing concrete structure and to propose the effective injection method on crack repair by packer type. The result of this study is as follows. It is investigated that the crack width in the inner matrix of concrete structure is decreased about 30-40% than that in the sulfate of the concrete structure. Also it is showed that the possibility which could be monolithic with injection part became higher if the injection part if installed near to surface of concrete on the punching method to vertical direction against crack area. The injection of repair material can be poured smoothly under about $10N/mm^2$ pressure on the condition that cracks are monolithic with injection part without dust by drill. The effective method to pour the injection repair material is the punching method by coredrill but several research to minimize injection pressure should be continually.

• 한국터널지하공간학회 논문집
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• 제4권1호
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• pp.13-25
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• 2002

영동터널의 굴착공법은 다음과 같은 세밀한 위험도 분석기법을 통하여 결정되었다. 본 논문에서는 실드 TBM 과 같은 형태의 기계화 굴착공법과 천공 및 발파에 의한 굴착공법에 따른 공사중 특정의 위험도를 분석 하였다. 공사 민감도 및 현장 경험등의 기타 중요인자를 고려한 위험도 분석결과에 따라 본 현장여건을 고려하면 천공 및 발파공법이 영동선 터널의 굴착공법으로 가장 적합하다고 제안 되었다.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.95-103
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• 2008

Diamond core drills are applied to drill difficult-to-cut materials. This paper proposes basic understanding of ceramic drilling mechanics and characteristics of main factors affecting tool life, tool wear, cutting force, and chipping thickness. In contrast to conventional drilling, the core drilling process make deep grooves on the workpiece. One difficulty of it is the evacuation of chips from the drilled groove. As the drilling depth increases, an increased amount of chips tend to cluster together and clog the groove. Eventually severe wear develops and diamond grits are separated from the drill body. To relieve the clogging problem and to evacuate chips from the groove easily, the helical drilling process is applied for the core drilling process. To analyze drilling characteristics and derive optimal drilling conditions, tool life, tool wear, cutting force, and chipping thickness are quantified through the monitoring system and the Taguchi method. Mathematical models for the tool life and chipping thickness are derived from the response surface method. Optimal drilling database has been constructed through the experimental models.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.200-206
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• 2002

영동터널의 굴착골법은 다음과 같은 세밀한 위험도 분석기법을 통하여 결정되었다. 본 논문에서는 실드 TBM과 같은 형태의 기계화 굴착공법과 천공 및 발파에 의한 굴착공법에 따른 공사중 특정의 위험도를 분석하였다. 공사 민감도 및 현장 경험등의 기타 중요 인자를 고려한 위험도 분석결과에 따라 본 현장여건을 고려하면 천공 및 발파공법이 영동선 터널의 굴착공법으로 가장 적합하다고 제안되었다.

• 대한산업공학회지
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• 제39권3호
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• pp.149-155
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• 2013

Electric discharging machining (EDM) is commonly adopted to machine the precise and tiny part when it is difficult to meet the productivity and the tolerance by the conventional cutting method. The die-sinking EDM method works well to machine the micro-parts and the perpendicular wall of die and mould, whereas EDM drilling, called super drill, is excellent to machine the deep and narrow hole regardless the material hardness and the hole location. However, the electrode wear is rapid compared to the conventional cutting tool and makes it difficult to control the electrode feeding and to machine precisely. This paper presents an efficient method to estimate the electrode wear using hole pass-through experiment while the stochastic method is used to compensate for the estimation model. To validate the proposed method, the commercial EDM drill machine is used. The experiment result shows that the electrode wear amount can be predicted very precisely.

• Journal of Multimedia Information System
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• 제6권2호
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• pp.67-74
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• 2019

Bone density is one of the factors in the early failure of dental implants and doctors should make a preoperative assessment of jaw bone density using patient's CT data before dental implant surgery in order to find out whether the patient has osteoporosis and osteopenia. The main goal of this study was to propose a method that based on image processing techniques in order to provide accurate information about where to drill and place an abutment screw of implants in the jaw bone for doctors and reduce human activity for the estimation of the local cancellous bone density of mandible using CT data. The experiment was performed on a computed tomography data of the jaw bone of two different individuals. We assumed that the result of the estimation of jaw bone density depends on the angle of drilling and average HU (Hounsfield Unit) values were used to evaluate the quality of local cancellous bone density of mandible. As a result of this study, we have been developed a toolbox that can be used to estimate jaw bone density automatically and found a positive correlation between the angle of the drill and time complexity but a negative correlation between the diameter of the drill and time complexity.

• Tribology and Lubricants
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• 제39권1호
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• pp.13-20
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• 2023

Large drill bits may face high hardness ore and high working pressure when working. To optimize the use effect of large drill bits and prolong the use time, it is necessary to add a layer of pressure-resistant, wear-resistant, and low-friction coating on the surface of the drill bit. In this study, CoCrNiAlTi high-entropy alloy coatings and CoCrNiAlTi (70 wt%)-TiC (30 wt%) composite coatings are successfully prepared on Q235 steel by plasma spraying. The CoCrNiAlTi (70 wt%)-TiC (30 wt%) coating consists of FCC solid solution and a small amount of TiC phase. The effect of TiC on the composition phase, microhardness, and elastic modulus of HEA coating is studied by X-ray diffractometer (XRD) and microhardness tester. The effect of TiC on the friction and wear properties of HEA coatings is investigated using a wear tester. By improving the process parameters, the metallurgical bonding between the coating and the substrate is well combined, and a coating without pores and cracks is obtained. The experimental results confirm that the microhardness, elastic modulus, and wear resistance of CoCrNiAlTi-TiC composite coating are better, and the friction coefficient is lower.

• 생물정신의학
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• 제20권3호
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• pp.86-90
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• 2013

Objectives The aim of this study was to find out the psychological changes associated with internet addiction between before and after the military drill among the young male army recruits. Methods All 1091 participants were army recruits aged from 19 to 22 years who participated in the 5-week military drill. They were assessed with some self-reported questionnaires [Sociodemographic questionnaires, Young's Internet Addiction Scale (IAS), the State-Trait Anxiety Inventory (STAI), the Beck Depression Inventory (BDI), the Barratt Impulsiveness Scale (BIS), the Attention-Deficit/Hyperactivity Disorder Self-Rated Scale (ASRS)]. They were divided into two groups, One is the internet addiction tendency group and the other is non-addiction group according to the IAS score. And the severity of the internet addiction tendency, depression, anxiety and impulsiveness were evaluated by the IAS, the STAI, the BDI, the BIS, the ASRS before and after military drill. Results The result of the paired t-test shows that the IAS, the STAI, the BDI, the BIS, the ASRS scores decreased after military drill in both non-addiction group and internet addiction tendency group. The result of the repeated measures ANOVA shows that there is an interaction effect between the changes of ASRS-hyperactivity (F = 23.437, p < 0.001), ASRS-impulsiveness (F = 4.896, p = 0.027), BIS-total (F = 4.057, p = 0.044), BIS-motor impulsiveness (F = 13.609, p < 0.001) scores and groups. The result of the generalized estimating equation shows that internet addiction tendency is associated with ASRS-inattention (${\beta}=0.075$, p < 0.001), ASRS-hyperactivity (${\beta}=0.092$, p = 0.002), STAI-trait anxiety (${\beta}=0.046$, p < 0.001), BIS-motor impulsiveness (${\beta}=0.119$, p = 0.028). Conclusions The results show that psychopathologies such as internet addiction tendency, depression, anxiety, impulsiveness may improve after military drill regardless of the groups. Internet addiction tendency may be related to the ASRS-inattention, ASRS-hyperactivity, STAI-trait anxiety, motor-impulsiveness. So these findings may be considered in the treatment of internet addiction in terms of the impulsiveness control.

• 한국작물학회지
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• 제40권6호
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• pp.697-704
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• 1995

벼 무논 골뿌림 재배시 물관리방법 및 생장조절기 처리가 생육 및 도복에 미치는 영향을 구명하고자 1994년에 미사질양토(전북통)인 호남 농업시험장 시험포장에서 동진벼를 5월 11일에 골깊이 4cm에 파종하고 중간낙수 회수 및 생장조절제를 처리하여 생육 및 도복형질을 검토한 결과를 요약하면 다음과 같다. 1. 상시심수에 비하여 2회 낙수구에서 간장이 짧았으며 생장조절제에는 Inbenfide G. > IMP G. > 무처리 순으로 간장이 단축되었다. 2. 상시심수에 비하여 2회 낙수구에서 간벽이 두껍고 뿌리량 및 뿌리의 심층분포 비율이 높았으나 생장조절제간에는 일정한 경향이 없었다. 3. 도복지수는 상시심수보다 2회 낙수구가 적고 생장조절제에는 세리타드 > 키타진 > 무처리의 순으로 적었으며 도복은 2회 낙수구에서는 생장조절제 무처리에서만 약간 발생하였으나 상시심수구에서는 무처리 > IBP G.> Inabenfide G.의 순으로 도복발생이 심하였다. 4. 쌀수량은 상시심수구의 생장조절제 무처리에서만 감수하였고 기타 처리에는 별 차이가 없었다 5. 따라서 벼 무논골뿌림 재배시는 생장조절제를 처리하지 않아도 2회(파종후 30일과 50일)에 실금갈 정도로 중간낙수만 하면 도복을 방지 할 수 있을 것으로 생각된다.

• 한국작물학회지
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• 제40권5호
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• pp.548-555
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• 1995

보리의 재배양식을 협폭파, 드릴파, 휴립광산파의 3양식으로 하여 이들 재배양식별 유효분얼의 생태반응과 수량성에 대하여 비교시험을 수행하였던 바 얻어진 결과는 다음과 같다. 1. 출아율은 드릴파 > 협폭파 > 휴립광산파의 순위였으나 m$^2$당 입모본수는 휴립광산파가 334본/m 으로 가장 많았고 다음으로, 협폭파, 드릴파의 순이었다. 2. 유효개화한 분얼은 3재배양식 모두 주간, 1차분얼의 1, 2 이고 2차분얼의 11은 휴립광산파에서만 유효경화하였다. 얼자별 유효경율은 주간은 3처리 모두 100%이나 1차분얼의 1과 2는 드릴파 > 휴립광산파 > 협폭파의 순으로 많았다. 3. 평균1수 영화수는 드릴파가 39.5립으로 가장 많았고 다음으로 휴립광산파, 협폭파의 순이었고 얼자별로는 주간 > 1 > 2 > 11이었다. 1수 임실율은 드릴파 > 휴립광산파 > 협폭파의 순으로 높았다. 4. 평균1수임실립수는 드릴파 > 휴립광산파 > 협폭파의 순이었고 평균 1수 완성립수도 같은 경향이었다. 그러나 천립중은 재배양식 또는 분얼경간에 크게 차이가 없었다. 5. 1수당 자실량은 드릴파가 가장 무거웠고 다음으로 휴립광산파, 협폭파의 순이었으며 분얼시험의 m 당 자실량은 협폭파 679.8g에 비하여 드릴파 874.7g, 휴립광산파 794.3g로 각각 29%와 17%가 증수되었다. 6. 실제평예조사시험의 유효경율은 46.2~54.1%로, 드릴파재배구가 가장 높았고 협폭파재배구에서 가장 낮았다. 7. 평예조사자실중은 협폭파 567.6kg에 비하여 드릴파 31%, 휴립광산파 15%가 각각 증수하였다.