• 한국정밀공학회지
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• 제30권5호
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• pp.493-498
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• 2013

The present study treats the optimization process for a non-linear grinding system with dual time delay, mainly from the energetic viewpoint. To this end, the stability of the grinding system is investigated first with regard to the grinding wheel rotation speed. The concept of grinding energy density is newly proposed as the primary figure of merit and this quantity is evaluated at various stable and limit cycle conditions. The computational results show that simple monotonic trend in energy density is observed under stable conditions, whilst rather complicated behaviors can appear when the conditions are associated with limit cycle oscillations. Finally, the relations between the vibration amplitude and the energy density and their implications on the engineering decision/compromise are discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.801-802
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• 2013

• 한국생산제조학회지
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• 제8권3호
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• pp.76-82
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• 1999

This study was carried out to verify finding performance of dental diamond bur and investigate the possibility of AE application in density field. Work pieces were made of acryl and bovine respectively for the experiments in this study. Grinding test was conducted to get the data of grinding resistance and specific finding energy of low different types of diamond bur by using tool dynamometer. AE signal was acquired to verify grinding process in the AE measuring system. AErms value was increased as the grinding velocity and depth were increasing, but it decreased as the feed rate was increasing. The case of the small value of AE signal is due to abnormal grinding in D type diamond bur. By analyzing AErms start and finish time of grinding working, abnormal grinding state can be confined. Abnormal state can be found through the behavior of AE signal in the finding working. As a result, it is expected that forecast of abnormal state is possible using AE equipments under real time process.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.72-77
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• 2005

The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.

• 한국광물학회지
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• 제23권3호
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• pp.227-234
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• 2010

본 연구에서는 라테라이트광의 건식 분쇄가 니켈 및 코발트의 침출에 미치는 영향을 조사하였다. 시료로 사용한 라테라이트광은 주로 $SiO_2$, $Fe_2O_3$, MgO로 이루어져 있으며, 니켈과 코발트의 함량은 0.81% Ni, 0.02% Co이었다. 주 구성 광물은 리자다이트와 석영이며, 미량의 포스터라이트와 엔스터타이트를 함유하고 있었다. 분쇄가 진행됨에 따라 시료의 평균입도, 비표면적, 밀도는 감소하는 경향을 보였으며, X-선 회절분석을 통해 리자다이트의 비정질화가 진행됨을 확인하였다. 분쇄에 의한 석영의 물성변화는 나타나지 않았으나, 리자다이트의 Mg-OH 결합이 파괴됨으로써 니켈 및 코발트의 침출율이 향상됨을 알 수 있었다. 분쇄가 진행됨에 따라 니켈과 코발트의 침출율은 증가하였으며, 60분 분쇄한 시료의 경우, 사용한 무기산의 종류에 관계없이 니켈과 코발트의 침출율은 약 80%로 나타났다.

• Journal of the Korean Wood Science and Technology
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• 제43권2호
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• pp.196-205
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• 2015

The aim of this study was to evaluate the fuel characteristics of thermally treated wood chips of the Larix kaempferi C. As torrefaction temperature was increased ($200^{\circ}C$ to $300^{\circ}C$), the carbon content, calorific value, and mass loss of torrefied wood chips increased significantly. The torrefied wood chips were shown to have hydrophobic properties even when only treated by mild torrefaction. The energy required to grind torrefied wood chips was reduced by the torrefaction process. Different sizes of wood chips were used in this study; however, this produced almost no difference in the fuel characteristics of processed Larix kaempferi C, except in the distribution of ground wood particles. Similar results were observed when the wood chips were torrefied for different lengths of time (15 min to 60 min) at a constant temperature. Torrefaction was shown to have positive effects on the fuel characteristics of Larix kaempferi C, including improved energy density, storage, and grindability.

• 자원리싸이클링
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• 제21권4호
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• pp.44-52
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• 2012

본 연구에서는 고정탄소 20.68%의 석탄으로부터 고품위 석탄 생산의 가능성을 확인하고자 한다. 또한, 광물학적, 물리, 화학적인 방법과 단체분리도의 특성을 파악하여 청정 석탄 기술의 처리과정에서 회분의 함량을 감소하는 데 목적이 있다. 본 연구에서 일반부선과 미립자 처리에 적합한 microbubble column 부선을 적용하여 기포제, 포수제, 억제제의 종류와 첨가량의 변화와 분쇄시간, 공기주입량, 급광량에 따른 영향을 확인하였다. 먼저 광액농도 20%, 포수제 DMU 101 + DDA(100mL/ton), 기포제 pine oil(200mL/ton), 억제제 sodium silicate(1 kg/ton)의 실험조건으로 일반부선을 실시한 결과, 회분제거율 81.55%, 회수율 70.23%를 얻을 수 있었고, 광액농도 5%, 분쇄시간 5분, collector DMU 101 + DDA(100 mL/ton), 기포제 AF65(5.4 L/ton), 억제제 AF65 (5.4 L/ton), 세척수(360 mL/min.)와 공기주입량(1,197 mL/min.)의 조건으로 microbubble column 부선을 실시한 결과, 회분제거율 83.85%, 회수율 70.42%를 얻을 수 있었다.

• 한국재료학회지
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• 제20권11호
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• pp.559-569
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• 2010

The liquid-phase sintering method was used to prepare a glass lens forming core composed of SiC-$Al_2O_3-Y_2O_3$. Spark plasma sintering was used to obtain dense sintered bodies. The sintering characteristics of different SiC sources and compositions of additives were studied. Results revealed that, owing to its initial larger surface area, $\alpha$-SiC offers sinterability that is superior to that of $\beta$-SiC. A maximum density of $3.32\;g/cm^3$ (theoretical density [TD] of 99.7%) was obtained in $\alpha$-SiC-10 wt% ($6Al_2O_3-4Y_2O_3$) sintered at $1850^{\circ}C$ without high-energy ball milling. The maximum hardness and compression stress of the sintered body reached 2870 Hv and 1110 MPa, respectively. The optimum ultra-precision machining parameters were a grinding speed of 1243 m/min, work spindle rotation rate of 100 rpm, feed rate of 0.5 mm/min, and depth of cut of $0.2\;{\mu}m$. The surface roughnesses of the thus prepared final products were Ra = 4.3 nm and Rt = 55.3 nm for the aspheric lens forming core and Ra = 4.4 nm and Rt = 41.9 for the spherical lens forming core. These values were found to be sufficiently low, and the cores showed good compatibility between SiC and the diamond-like carbon (DLC) coating material. Thus, these glass lens forming cores have great potential for application in the lens industry.

• 한국광물학회지
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• 제25권3호
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• pp.123-130
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• 2012

염소-차아염소산 용액을 소성정광에 적용하여 gold와 silver를 효과적으로 용출시키고자 하였다. 염소 : 차아염소산 혼합비율 1.5 : 1, 그리고 NaCl 농도를 1 M으로 적용하였을 때 Au 용출율은 겨우 75%와 81%이였다. 그러나 광액농도를 1%로, 그리고 용출온도를 $65^{\circ}C$로 적용하자 Au 용출율이 100%에 도달되었다. 왕수분해 및 염소-차아염소산 용출 고체 잔유물을 XRD분석을 실시한 결과 석영이 관찰되었다. 따라서 석영 속에 함유된 gold는 염소-차아염소산으로 용출시키지 못할 것으로 사료된다. 따라서 석영 속의 gold를 용출시키기 위해서는 더 작은 미립자로 전처리하거나 더 강력한 산화제를 적용해야 할 것이다.

• 자원리싸이클링
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• 제25권6호
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• pp.98-104
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• 2016

본 연구의 목적은 호주산 저품위 동광을 부유선별하여 정광으로 회수하고자 할 때, 최적의 부유선별 조건을 얻고자 하는데 있다. 본 연구에서는 저품위 동광의 파분쇄 및 분급에 의해 선별에 적절한 입자크기의 시료를 얻은 다음, 이를 대상으로 부유선별 시 포수제, 활성제, 억제제의 첨가량 및 광액의 pH 변화가 부선효율에 미치는 영향을 조사함으로써 품위가 향상된 정광을 얻고자 하였다. 본 연구실험결과 얻은 최적의 부유선별 조건은 광액산도 pH9.0, 활성제 500 g/t $CuSO_4{\cdot}5H_2O$, 포수제 500 g/t K.E.X, 억제제 1500 g/t $Na_2SO_3$, 광액농도는 25 wt.% 이었다. 최적조건하에서 얻은 정광중의 동 품위 및 회수율은 각각 4 wt.%와 65 wt.% 정도이었고 대부분 철 성분을 함유한 광물 이었다.