• Resources Recycling
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• v.10 no.2
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• pp.41-49
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• 2001

In this study, the properties of cement mortar and concrete using ceramic wastes as fine aggregates and coarse aggregates are considered experimentally. Flow value of mortar using ceramic waste as fine aggregates is increased more or less, and the com- pressive strength of mortar using ceramic wastes as fine aggregates is increased with elapsed age. The slump value of concrete using ceramic wastes fine aggregates and coarse aggregates is somewhat decreased. The compressive strength of concrete using ceramic wastes as fine aggregates and coarse aggregates is lower than that of OPC concrete in early age, but has gradually increased in long ages.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.4
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• pp.323-336
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• 2003

Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.179.2-179.2
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• 2011

바이오매스 가스화 프로세스 개발에 있어서 가장 기본적인 해결과제는 고발열량의 합성가스 제조, 냉가스 효율의 향상, 타르 발생량 저감 및 제거이다. 가스화 효율 향상에 대한 연구는 국내외 적으로 많이 이루어지고 있으나, 타르 발생량 저감에 대한 연구는 많이 이루어져 있지 않다. 타르는 분자량이 큰 방향적 탄화수소로 응축되면 점성이 높아 배관폐쇄, 정제설비의 압력손실 증가로 인해 운전정지 및 가스화율 저하의 원인이 된다. 가스화로에서 타르 발생량을 저감시키는 방법 중에는 Ni계 촉매를 이용하는 방법이 있으나, 카본 누적에 의한 활성저하, 알칼리금속에 의한 응집 등의 문제가 발생할 수 있다. 한편 철산화물은 합성가스 중의 C2-C3계의 타르를 분해하는데 효과가 알려져 있다. 따라서 본 연구에서는 적벽돌, 염색슬러지 회재 등에는 철산화물이 다량 함유되어 있는 것에 착안하여 폐기물중의 폐금속을 이용한 바이오매스 가스화에 대한 연구를 수행하였다. 점토광물계 폐기물인 적벽돌 파쇄물($SiO_2$ 67.2%, $Al_2O_3$ 19.7%, $Fe_2O_3$ 8.7%, $K_2O$ 2.0%, $TiO_2$ 1.2%, MgO 0.7%)을 전처리 한 후 유동매체로하여 우드펠렛을 가스화한 결과, 가스 생성량이 증가하고, 타르 및 탄화수소류가 감소하는 경향을 나타내었다. 특히 타르는 후단의 타르 트랩에서 타르가 거의 검출이 되지 않았다. 전처리를 하지 않은 적벽돌 파쇄물은 반응시간이 경과한 후에 가스화율이 증가함에 따라 철화합이 가스화로내에서 환원되어 타르를 분해하는데에는 어느 정도의 반응시간이 필요한 것을 확인하였다.

• Journal of Practical Agriculture & Fisheries Research
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• v.3 no.1
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• pp.132-141
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• 2001

This study was conducted to determine effects of whole and processed corns on attachment characteristics of rumen microbes in Hanwoo. Whole corn(WC) was processed into four different types; ground corn(GC), cracked corn(CC), flaked corn(FC), and soaked corn(SC). After each processed corns was incubated in the rumen of Hanwoo for 12 h and 24 h, attachment characteristics of rumen microbes and morphological changes of feed substrates was examined by utilizing scanning electron microscopy(SEM). In this study, the treatment group of GC and CC showed the highest in the attachment of rumen microbes. On the other hand, microbial attachments to the starch particle of WC and SC were hardly detected. However, with the increase of incubation time the surface of WC and SC was covered by many microbes, resulting in enhancing the surface degradation.

• Korean Journal of Construction Engineering and Management
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• v.6 no.4 s.26
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• pp.142-151
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• 2005

Several advanced countries have been continually developed PHC pile cutting automation machines for improving productivity, safety and quality of the conventional PHC pile cutting work. However, the target work of the previously developed PHC pile cutting automation machines is only crushing the head of PHC pile. Dangerous grinding work is still performed by workers with seven inch hand grinder. In domestic construction industry, the PHC pile cutting work is usually performed by a crusher and three to four skilled workers. Recent analysis results of the PHC pile cutting work reveal that it frequently makes a lot of cracks which significantly reduce the strength of the pile and is labor-intensive work. The primary objective of this study is to propose the end-effector which can effectively break PHC pile without any longitudinal cracks and to develop an automated pile cutting machine having unified grinder and crusher parts through a wide variety of laboratory and field tests. It is anticipated that the development of the automated pile cutting machine would be able to bring improvements in safety, productivity, quality as well as cost saving.

• Resources Recycling
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• v.23 no.3
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• pp.30-36
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• 2014

A large amount of waste copper slag containing about 35 ~ 45% iron has been generated and discarded every year from pyrometallurgical processes for producing copper from copper concentrate. Thus, recovery of iron from the waste copper slag is of great interest for comprehensive use of mineral resource and reduction of environment problems. In this study, a physico-chemical separation process for upgrading iron from the waste copper slag discharged as an industrial waste has been developed. The process first crushes the waste copper slag below 1 mm (first crushing step), followed by carbon reduction at $1225^{\circ}C$ for 90 min (carbon reduction step). And then, resulting material is again crushed to $-104{\mu}m$ (second crushing step), followed by wet magnetic separation (wet magnetic separation step). Using the developed process, a magnetic product containing more than 66 wt.% iron was obtained from the magnetic separation under a magnetic field strength of 0.2 T for the waste copper slag treated by the reduction reaction. At the same conditions, the percentage recovery of iron was over 72%. The iron rich magnetic product obtained should be used as a iron resource for making pig iron.

• Journal of Practical Agriculture & Fisheries Research
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• v.3 no.1
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• pp.116-131
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• 2001

Experiments were conducted to determine effects of whole and processed corns on in situ disappearance rates of nutrients in the rumen and in vitro degradability of dry matter by rumen microorganisms. Whole corn(WC) was processed into four different types; ground corn(GC), cracked corn(CC), flaked corn(FC), and soaked corn(SC). In the in situ experiment, the rate of ruminal DM disappearance after 48 hour incubation was highest in GC(76.1%) and lowest in WC and SC(12% ; P<0.01). The rate of ruminal CP disappearance after 48 hour incubation was highest in GC and CC(48 and 38%, respectively; P<0.01). The rate of ruminal OM disappearance after 48 hour incubation was highest in GC(76.14%) and lowest in WC and SC(11.82 and 12.26%, respectively; P<0.01). In the in vitro experiment, the two-stage incubation technique was used to measure digestibilities of whole and processed corns. The digestibility of DM was higher in GC, CC and FC(86.95, 85.84 and 82.29%, respectively) than in WC(15.36%; P<0.01).

• Explosives and Blasting
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• v.19 no.3
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• pp.39-47
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• 2001

Bulk-Emulsion system은 미주나 서구 유럽 등지의 발파분야에 있어 선구적인 역할을 수행하여 왔던 나라에서는 이미 보편화된 시스템으로 ANFO 다음으로 노천이나 터널 굴진에 널리 적용되고 있다. Bulk-Emulsion system은 제조, 저장, 운반 및 사용에 있어서 극히 안전하고 장전밀도를 증가시켜 효과적인 파쇄와 굴진률 향상을 기대할 수 있으며 발파 후가스가 매우 양호한것을 비롯하여 기계화 장전에 따른 시공 능률 향상과 작업 안전성 강화 등 많은 장점을 가지고 있다. 본 연구에서는 고속도로 터널 현장에 국내 최초로 터널용 Bulk-Emulsion system을 이용하여 총 15회에 걸쳐 시험발파를 실시하였으며 이 결과를 토대로 하여 Bulk-Emulsion system 적용에 따른 효과와 문제점을 알아보고자 하였다.

• Cement Symposium
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• s.36
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• pp.110-115
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• 2009

2,3,4호 시멘트밀은 기존의 Tube MiIl 단독의 시멘트 분쇄 밀에 예비분쇄기(이하 "Polycom", Polysius 1992년 공급)를 설치, 합리화하여 운영되고 있는 Combi grinding type의 시멘트밀이다. 생산능력은 일 생산성 4,800T/D, Blaine $3,200cm^2/g$ 품질로 설계되었다. 금번 공정개선 부문인 예비분쇄공정의 Polycom 출구 Bucket Elevator(이하 "B/E") 및 Disagglomerator(이하 "DISA")로 위치는 Fig.1과 같다. Polycom 출구 B/E 및 DISA는 Polycom에서 분쇄된 원료를 분급기로 이송 및 cake 상태의 원료를 파쇄하는 설비이다. 상기 설비는 시멘트밀 공정에서 반드시 필요한 설비이나 - 잦은 고장에 따른 설비 가동율 저하 - 순환량 증가시 제한운전에 따른 생산효율저하를 일으키는 주된 설비로써 원단위 절감 및 설비가동효율 향상을 위하여 개선이 불가피한 설비임.

• Korean Journal of Soil Science and Fertilizer
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• v.16 no.2
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• pp.92-97
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• 1983

This experiment was designed to establish the soil physical improvement practice to increase the rice yields at fine textured fluvio-marine paddy field. After chiseling and trenching the paddy soil, the rice growth and soil physical properties were investigated for 4 years. The results are summarize as follows; 1. The soil physical properties, such as bulk density, hardness, porosity and permeability were prominently improved by trenching and chiseling. 2. There were significant relationships among the soil physical properties, root developments and rice yields. 3. The increasing rates of rice yields by soil physical improvement were about 10%, which is better than 5% of drainage effects. 4. The effects of trenching and chiseling on rice yields were continued to fourth year. Even if trenching effects was better than chiseling the chiseling was considered as a useful treatment for its simple working practice by using a heavy machine. 5. In case of trenching, straw application were increased the rice yields.