• 한국지열·수열에너지학회논문집
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• 제17권1호
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• pp.14-22
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• 2021

Drilling equipment is an essential part used in various fields such as construction, mining, etc., and it has drawn increasing attention in recent years. The drilling method is generally divided into three types. There are a top hammer method that strikes on the ground, a DTH (Down-The-Hole) method that directly strikes a bit in an underground area, and a rotary method that drills by using rotational force. Among them, the DTH method is most commonly used because it enables efficient drilling compared to other drilling methods. In the conventional DTH hammer, the valve between the piston and the bit is opened and closed using a face to face method. In order to improve the power of the DTH hammer, a DTH hammer with foot valve which is capable of instantaneous opening and closing is used in the drilling field. In this study, we designed a lab-scale DTH hammer with the foot valve, and manufactured an evaluation device for the experiment of the DTH hammer. In addition, we analyzed the performance of the DTH hammer adopted with foot valve according to the pressure range of 3-10 bar. As a result, the internal pressure distribution in the DTH hammer was experimentally analyzed, and then, the movement of the piston according to the pressure was predicted. We believe that this study provides the useful results to explain the performance characteristics of the DTH hammer with the foot valve.

• 대한기계학회논문집A
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• 제36권1호
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• pp.109-116
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• 2012

현재 천공장비 및 천공방법에 대한 많은 연구가 진행되고 있지만 DTH hammer의 타격성능을 규명하고 최적화에 대한 연구는 전무하다. 또한 DTH drilling의 시험 장비를 구축하기 위해서는 막대한 비용과 많은 시간이 요구되기 때문에 성능규명에 있어 시험적으로 접근하기가 매우 곤란한 실정이다. 따라서 본 논문에서는 DTH hammer의 구동원리를 파악 후 공압 해석을 이용하여 구동 특성 및 성능을 규명하였다. 또한 실험계획법을 이용하여 DTH hammer의 성능에 영향력이 있는 설계인자를 도출하고 이를 다구찌 기법에 적용해 DTH hammer의 타격성능인 타격수와 타격에너지의 최적화에 대한 연구를 수행하였다.

• Parasites, Hosts and Diseases
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• 제45권2호
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• pp.103-109
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• 2007

Leishmania tropica and L. major are etiologic agents of human cutaneous leishmaniasis. Delayed type hypersensitivity (DTH) is an immunologic response that has been frequently used as a correlate for protection against or sensitization to leishmania antigen. In BALB/c mice, L. tropica infection results in non-ulcerating disease, whereas L. major infection results in destructive lesions. In order to clarify the immunologic mechanisms of these 2 different outcomes, we compared the ability of these 2 leishmania species in induction of DTH response in this murine model. BALB/c mice were infected with L. major or L. tropica, and disease evolution and DTH responses were determined. The results show that the primary L. major infection can exacerbate the secondary L. major infection and is associated with DTH response. Higher doses of the primary L. major infection result in more disease exacerbation of the secondary L. major infection as well as higher DTH response. L. tropica infection induces lower DTH responses than L. major. We have previously reported that the primary L. tropica infection induces partial protection against the secondary L. major infection in BALB/c mice. Induction of lower DTH response by L. tropica suggests that the protection induced against L. major by prior L. tropica infection may be due to suppression of DTH response.

• 대한기계학회논문집A
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• 제40권6호
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• pp.603-611
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• 2016

광물시장 성장과 함께, 고효율 DTH 해머 필요성이 함께 증가되고 있다. 그러나 DTH 해머는 지하 천공이라는 작동조건의 특성 때문에, 실험 데이터의 직접 취득이 어렵고, 실제 테스트를 하기 위해서는 DTH 드릴 리그와 많은 운용비를 필요로 한다. 본 연구에서는 이러한 DTH 해머의 제품개발 시간과 비용의 문제점을 컴퓨터 시뮬레이션을 이용하여 해결하고자 하였다. 이전 연구에서DTH 해머구조와 동작 원리를 분석하고, 시뮬레이션을 이용한 표준 모델을 제시하고, 그것을 실험과 비교 검증하였다. 이를 바탕으로 본 논문에서는 실험설계법을 이용하여DTH 해머의 타격에너지와 효율에 관한 제어인자를 도출하고, 이에 관한 최적화를 시도하였다. 그 결과 타격에너지를 14.9% 효율은 3.3% 높이는 결과를 얻었다.

• 드라이브 ㆍ 컨트롤
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• 제12권2호
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• pp.34-38
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• 2015

Research and development of mineral resource related products has progressed with the increased need to develop mineral resources. The DTH hammer is one a resultant product. However, due to particular work conditions of underground drilling, it is difficult to obtain direct data on the DTH Hammer. A DTH drill rig requires a lot of money and time for actual testing. This thesis aimed to resolve this problem by using CAE. First, the structure of the DTH hammer and the movement was analyzed. Next, a standard model based on simulation was proposed and then experimentation and comparison verification was conducted. In addition, the verified models were applied to products of various sizes, and the models used in simulation were compared by conducting field tests.

• 약학회지
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• 제43권1호
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• pp.98-103
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• 1999

Effects of Astragali Radix extract (AG) on the cell mediated-and nonlpecific immunotoxic responses of zinc chloride (Zn) were studied usign ICR mice. Mice were divided into 4 groups (10 mice/group), and Zn was given to the mice 1 hr after i.p. injection with 0.5g/kg of AG by i.p. injection daily for 10 days at a dose of 25 mg/kg. Immune responses on the responses on the relative weight of thymus, delayed-type hypersensitivity to SRBC (DTH), phagocytic activity and circulating leukocytes were evaluated. Zn treatment decreased body weight gain, the relative weight of thymus, DTH and circulating leukocytes compared with those in controls. AG treatment increased DTH, phagocytic activity and circulating leukocytes compared with those in controls. Combination of AG and Zn increased DTH and circulating leukocytes compared with those in controls, but decreased body weight gain and the relative weight of thymus. These findings indicated that AG decreased immunotoxicity of Zn on the DTH and circulating leukocytes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1287-1288
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• 2011

• 대한미생물학회지
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• 제21권1호
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• pp.145-149
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• 1986

The development of delayed-type hypersensitivity(DTH) reaction to Staphylococcus aureus in mice was studied, Mice received 3 injections of $10^8$ viable S. aureus subcutaneously showed a marked footpad swelling when mice were challenged with $10\;{\mu}g$ staphylococcal protein antigen into footpad(The percent increase of footpad thickness at 24 h after challenge wsa 35% approximately). Histological observation of footpad of immunized mice showed a marked thickness of subcutaneous tissue due to edematous reaction and massive infiltration of lymphocytes and neutrophils which are characteristic cells in DTH reaction. Intensity of DTH reaction of mice immunized with viable bacteria was much higher than that of mice immunized with staphylococcal protein or heat-killed bacteria. The DTH reaction to S. aureus could be transferred to normal recipient mice by both spleen cells and lymph node cells.

• 대한미생물학회지
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• 제21권4호
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• pp.455-460
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• 1986

This study was undertaken to investigate to know whether spleen and lymph node cells from immunized mice can transfer systemically the delayed-type hypersensitivity(DTH) reaction to Salmonella typhimurium and to characterize the lymphoid cells using glass, nylon wool and rabbit anti-mouse thymocyte serum. Mice, C57BL/6 or ICR, were immunized subcutaneously at 11, 8 and 2 days before adoptive systemic transfer with $100{\mu}g$ of protein antigen from S. typhimurium in complete Freund adjuvant. It was found that DTH reaction to S. typhimurium could be transferred to normal recipient systemically by both spleen and lymph node cells($10^8\;cells$, respectively) from immunized mice. The cells responsible for this transfer of DTH reaction were glass nonadherent T lymphocytes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.599-600
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• 2010