• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.8-13
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• 2001

In the turning process, the feed is usually selected by a machining operator considering workpiece, cutting tool and depth of cut. Even if this selection can avoid power saturation or tool breakage, it is usually conservative compared to the capacity of the machine tools and can reduce the productivity significantly. This paper proposes a selection method of the feed and the reference cutting force based on MRR(material removal rate), maximum spindle power and specific energy. In order to estimate and control cutting force accurately in transient and steady state, this study utilizes a synthesized cutting force estimation method and a Fuzzy controller. The experimental results present that these systems can be useful for the FMS(flexible manufacturing system) and unmanned automation system.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1446-1452
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• 2002

In the turning process, the feed is usually selected by a machining operator considering workpiece, cutting tool and depth of cut. Even if this selection can avoid power saturation or tool breakage, it is usually conservative compared to the capacity of the machine tools and can reduce the productivity significantly. This paper proposes a selection method of the feed and the reference cutting force based on MRR(material removal rate), maximum spindle power and specific energy. In order to estimate and control cutting force accurately in transient and steady state, this study utilizes a synthesized cutting force estimation method and a Fuzzy controller. The experimental results show that these systems can be useful for the unmanned turning process.

• 한국기계가공학회지
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• 제19권10호
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• pp.81-86
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• 2020

A ceramic vacuum chamber feedthrough ceramic insulator is made of Al2O3; the manufacturing process involves filling alumina powder into a urethane mold and pressing it with a rubber press to produce a molded body. Thereafter, manufacturing is completed through primary shape processing, sintering, and secondary shape processing in the green body, which is a pressurized molding body, This work is intended to prevent defects in the first shape processing by improving the ceramic insulator in the green body, and to improve the productivity of the ceramic insulator by determining the optimal processing conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.870-873
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• 2000

This investigation reports the grinding characteristics of quartz. Grinding experiments were performed at various grinding conditions including wheel mesh, table speed and depth of cut. The grinding forces and specific grinding energies were measured to compare the grindability of quartz with those of structural ceramics such as A1$_2$O$_3$, SiC, Si$_3$N$_4$ and ZrO$_2$. Surface roughness was also measured with tracer and the ground surfaces were observed with SEM. The chip formation energy of quartz was about 6J/㎣, which is quite smaller than those of structural ceramics. Although plastic flows are occured in Si$_3$N$_4$ and ZrO$_2$, micro/macro cracks are occured in ground surface of quartz like in A1$_2$O$_3$ and SiC.

• 한국전기전자재료학회논문지
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• 제16권5호
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• pp.385-389
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• 2003

There are four main components of the CMP process: polishing pad, slurry, elastic supporter, and pad conditioner. The polishing pad is an essential component to the reproducibility of polishing uniformity in CMP process. However, the polishing pad in recently using metal CMP raised the several points of high cost caused by the increase of cycle time and the many usage of slurry. It is necessary to develop the novel polishing pad which would lead the cost reduction by the higher pad life-cycle, minimized cycle time and lower slurry usage. The characteristics of polishing pad were studied on the effects of different sets of the Polishing pad, which can be applied to metal chemical mechanical polishing process for global planarization of multilevel interconnection structure. The main purpose of this experiment is cost reduction by the increase of pad life-time, the decrease of cycle time and the lower usage of slurry through the specific hard porous structured pad design. It is confirmed that the novel polishing pad made the slurry usage decrease to 60% as well as the pad life-time increase twice with the 25% improvement of removal rate. The polishing time could be decreased and it also helped the cycle time to diminish. It can be expected that this results will help both the process throughput and the device yield to be improved.

• 한국미생물·생명공학회지
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• 제41권2호
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• pp.215-220
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• 2013

Tobermolite, perlite 및 polyurethane을 충전재로 이용한 바이오필터에 의한 메탄제거 기술이 개발되고 있다. 본 연구에서는 이들 충전재가 메탄산화능에 미치는 영향을 알아보았다. 습지토양과 매립지토양에서 분리한 혼합 메탄산화세균(consortium A, B, C and D)를 접종원으로 하고, 메탄산화속도와 메탄산화세균 수에 미치는 담체(perlite, tobermolite,polyurethane)의 영향을 조사하였다. Perlite를 첨가한 경우 메탄산화속도는 대조군 (담체 미첨가)보다 두 배 이상 증가하였고, 메탄산화세균 수도 10배 이상 증가하였다. Tobermolite를 첨가한 경우에는 일반세균 수 대비 메탄산화세균의 비율이 대조군과 다른 담체에 비해 높았다. 이는 tobermolite가 메탄산화세균이 우점할 수 있는 특이적 담체로 작용함을 시사한다. 이상의 결과로 부터 perlite와 tobermolite는 메탄산화세균의 활성을 증가시키는 서식지를 제공하며 메탄산화 공정시스템에 적용 시 좋은 담체의 역할을 할 수 있을 것으로 기대된다.

• 한국전기전자재료학회논문지
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• 제31권6호
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• pp.417-421
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• 2018

$TiO_2$ has excellent photocatalytic properties and several studies have reported the increase in its specific surface area. The structure of $TiO_2$ nanofibers indicates promising improved photocatalytic properties and these nanofibers can thus potentially be applied in air pollution sensors and pollutant removal filters. In this study, a $TiO_2$ nanofiber was fabricated by the electrospinning method. The fabrication processing factors such as the applied voltage, the distance between nozzle and collector, and the inflow rate of solution were controlled. The precursor was titanium (IV) isopropoxide and as-spun $TiO_2$ nanofibers were heated at $450^{\circ}C$ for 2 h to obtain an anatase crystalline structure. The microstructure was analyzed using field emission scanning electron microscope (FE-SEM) and X-ray diffraction analysis (XRD). The anatase phase was observed in the $TiO_2$ nanofibers after heat treatment. The diameter of $TiO_2$ nanofibers increased with the flow rate, but decreased with decreasing applied voltage and nozzle to collector distance. The diameter of $TiO_2$ nanofibers was controlled in the range of 364 nm to 660 nm. These nanofibers are expected to be very useful in photocatalytic applications.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.86-92
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• 2002

In this study, experiments were carried out to investigate the characteristics of grinding and wear process of diamond wheel far ceramic materials. Normal component of grinding resistance of $Al_2$O$_3$ was less then that of $Si_3 N_4$ and $ZrO_2$. This seems to be the characteristics of ceramic tools on work pieces both of high hardness. For the case of $Si_3 N_4$ and $ZrO_2$, as the mesh number of wheel increases, the surface roughness decreases. For the case of $Al_2 O_3$, the surface roughness does not decreases. Specific binding energy decreases as the material removal rate per unit time increases. For the case of $Si_3 N_4$ and $ZrO_2$, grinding is carried out by abrasive wear processes. For the case of $Al_2 O_3$, grinding is carried out by grain shedding process due to brittle fracture.

• Korean Chemical Engineering Research
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• 제50권4호
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• pp.754-757
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• 2012

본 연구에서는 embossing 공정과 진공여과법에 의해서 제조된 다공성 그래핀 필름을 슈퍼캐패시터의 전극활물질로 사용하여 우수한 전기화학적 특성을 증명하였다. 그래핀 시트사이에서 Polystyrene 입자들의 삽입/제거 공정을 이용하여 기공 구조들을 제공함으로써 그래핀의 재적층(restacking)을 효과적으로 제어할 수 있었다. 상기 제조된 다공성 그래핀 필름은 넓은 표면적, 상호 연결된 기공 구조, 높은 전기전도도 및 우수한 기계적 물성을 나타내었다. 본 다공성 그래핀 필름을 슈퍼캐패시터의 전극물질로 사용하여 황산 수용액과 이온성 액체 전해질 기반의 3상 전극 시스템에서 전기화학적 특성을 살펴보았다. 다공성 그래핀 필름은 높은 비축전용량(284.5 F/g)을 나타내었으며, 이는 적층 그래핀 필름(138.9 F/g) 보다 두 배 정도 높았다. 또한, 그래핀 필름내의 이온 이동속도 향상 효과로 다공성 그래핀 필름의 충방전 속도(98.7% retention)와 충방전 수명(97.2% retention)이 크게 향상되었다.

• Transactions on Electrical and Electronic Materials
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• 제2권2호
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• pp.37-41
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• 2001

Photo catalytic characteristics of nano-sized TiO$_2$ powder with rutile phase produced using homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 powder by Degussa Co. The TiO$_2$ powder by HPPLT showed very higher photoactivity in the removal rate, showing lower pH values in the solution, than the P-25 powder when eliminating metal ions such as Pb and Cu from aqueous metal-EDTA solutions. This can be inferred the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of electron-hole pair formed on the surface of TiO$_2$ particle, under UV light irradiation. Also, in the view of the TiO$_2$ particle morphology, compared to the well-dispersed spherical P-25 particle, the agglomerated TiO$_2$ particle by HPPL T consists of acicular typed primary particle with the thickness ranged of 3∼7 nm, which would be more effective to the photocatalytic reactions without electron-hole recombination on the surface of the TiO$_2$ particle under the UV light irradiation. It is, therefore, thought that the higher photo activity of the rutile TiO$_2$ powder by HPPLT in the aqueous solutions resulted from having its higher specific surface area as well as acicular shape primary particle with very thin thickness.