• Journal of Biosystems Engineering
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• 제25권1호
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• pp.39-46
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• 2000

This work was conducted to study the operating characteristics of a grinding system designed to obtain fine rice husk ash powder. To find better utilizing of rice husk, a valuable by-product from rice production, once the rice husk was incinerated and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement manufacturing . The rice husk ash grinding system consisted of a high speed centrifugal fan for the preliminary coarse milling and a dry-type stirred ball mill for the subsequent fine grinding . Total grinding time 9 5, 15, 30, 45 min), impeller speed (250, 500, 750 rpm) , and mixed ratio (4.8, 7.9, 14.9) were three operating factors examined for the performance of a stirred ball mill used for the fine grinding of ash. With the stirred ball mill used in this study, the minimum attianable mean diameter of rice husk ash powder appeared to be 2 ${\mu}{\textrm}{m}$. During the find grinding, the difference in specific surface area of powder showed an increase and the grinding energy efficiency decreased with the increase in total grinding time, impeller speed ,and mixed ratio. For the operating conditions employed , the resulting mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of 1.79 --16.04${\mu}{\textrm}{m}$, 0.072-5.226kWh/kg, an d1.11-12.15$m^2$/Wh, respectively. Grinding time of 30 min , impeller speed of 750 rpm, and mixed ratio of 4.8 were chosen as the best operating conditions of the stirred ball mill for fine grinding . At these conditions, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughtput, and specific energy input were 2.73${\mu}{\textrm}{m}$, 3.95$m^2$/Wh, 0.25kg/h, and 1.22kWh/kg, respectively.

• Journal of Biosystems Engineering
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• 제31권1호
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• pp.33-38
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• 2006

This work was conducted to find the operating characteristics of an efficient wet grinding system designed to obtain fine rice husk ash powder. Once the rice husk was combusted and the thermal energy was recovered from the furnace, the ash was fed and pulverized in the grinding system resulting a fine powder to be used as a supplementary adding material to the portland cement. Grinding time (15, 30, 45 min), impeller speed (250, 500, 750 rpm), and mixed ratio (6.7, 8.4, 11.l, 20.9) were three operating factors examined for the performance of a wet-type stirred ball mill grinding system. For the operating conditions employed, mean diameter of fine ash powder, specific energy input, and grinding energy efficiency were in the range of $2.83{\sim}9.58{\mu}m,\;0.5{\sim}6.73kWh/kg,\;and\;0.51{\sim}3.27m^2/Wh$, respectively. With the wet-type stirred ball mill grinding system used in this study, the grinding energy efficiency decreased with the increase in total grinding time, impeller speed, and mixed ratio. The difference in specific surface area of powder linearly increased with logarithm in total number of impeller revolution and the grinding energy efficiency linearly decreased. Grinding time of 45 min, impeller speed of 500 rpm, and mixed ratio of 6.7 were chosen as the best operating condition. At this condition, mean particle diameter of the fine ash, grinding energy efficiency, grinding throughput, and specific energy input were $2.84{\mu}m,\;2.28m^2/Wh,\;0.17kg/h$, and 2.03kWh/kg, respectively. Wet fine grinding which generates no fly dust causing pollution and makes continuous operation easy, is appeared to be a promising solution to the automatization of rice husk ash grinding process.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.234.2-234.2
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• 2003

Recently, the need for ultra-fine particles, especially nano-sized particles has increased in the fields preparing raw powders such as pharmaceutical additive and high value added products in the Nano-Technology processes. Therefore, the research in ultra-fine grinding is very important, especially, in nanometer grinding. In the previous paper, a series of wet grinding experiments using grinding aids using a stirred ball mill have been performed on grinding rate constant based on grinding kinetics. (omitted)

• 반도체디스플레이기술학회지
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• 제10권3호
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• pp.35-42
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• 2011

This paper describes the characteristics of high speed grinding and the influence of wheel surface speed V and a grindability of the grinding materials. The various fine ceramics pieces was ground by metal and vitrified bonded diamond wheel. The surface roughness of fine ceramics(Zirconia($ZrO_2$), Silicon Carbide(SiC), Silicon Nitride($Si_3N_4$), Alumina($Al_2O_3$)) decreases from $0.05{\mu}m(R_{max})$ to $0.025{\mu}m(R_{max})$ when the wheel speed at grinding point increases the wheel speed. Relation between the temperature at grinding point and surface roughness was linear. Abrasive jet machining(AJM), a specialized from of shot blasting, is considered one of the most helpful micro machining methods for hard and brittle materials such as glasses and ceramics by constant pressure grinding.

• 한국생산제조학회지
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• 제9권2호
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• pp.138-143
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• 2000

The establishment of a practical ultra-precision grinding technique using Diamond and CBN wheels is one of the major key technolo-gies to improve production techniques for machine-to-difficult materials without finishing process such as lapping and polishing. But the special efficient dressing technique for ultra-fine grit type grinding wheels to stabilize the grinding ability was not developed. Recently electrolytic in-process dressing technique is proposed to ultra-fine grit type metal bonded diamond wheels to protrude abra-sives continuously from the tool surface. This technology can be widely used to surface grinding and cylindrical grinding but cannot be used efficiently to internal grinding because of the electrode attachment trouble. This paper describes the effect of interval type electrolytic dressing as proposed newly to cast iron bonded diamond wheel for efficient internal grinding with mirror type high quality ground surface.

• 한국정밀공학회지
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• 제18권3호
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• pp.35-39
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• 2001

The precision grinding process is carried out with fine-cutting operation after coarse-cutting operation. So, the laminated grinding wheel has been developed to reduce the ineffectiveness induced by changing the operations. In this study, to investigate the possibility of the practical use of the laminated grinding wheel, the surface residual stress of the workpiece ground by the laminated grinding wheels was compared with that ground by the general grinding wheel, and the influence of the difference in grain sizes, between the coarse grit and fine grit of the laminated grinding wheel, on the surface roughness of the workpiece was investigated.

• 한국정밀공학회지
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• 제19권6호
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• pp.145-154
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• 2002

CMP (Chemical mechanical polishing) process was used to control the fine grinding process induced mechanical damage of Cz Silicon wafer. Characterization of mechanical damage was carried out using Nomarski microscope, magic mirror and also using angle lapping and lifetime scanner evaluation after heat treatment. Magic mirror and lifetime scanner were very useful for the residual damage pattern characterization and CMP process was effective on the reduction of fine grinding induced mechanical damage.

• 한국정밀공학회지
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• 제7권4호
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• pp.40-54
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• 1990

Recently, Fine Ceramics have been concerned significantly with some excellent properties and many functions as new industrial materials to the industry at alrge. For the manufacture of Fine Ceramics, sintering is essential process. Thus the most of a Fine Ceramics used for precision parts are in need of machining proces. It is, however, very difficult to manufacture the Advanced Ceramics with high efficiency because they have not only high strength and brittl- eness but also high hardness. In present research, experiments are carried out to obtain the basic knowledge of Fine Ceramics grinding with high efficiency. Representative advanced ceramics, such as A1/sub 2/0/sub 3/, Z/sub r/O/sub 2/SiC snd Si/sub 2/N/sub 4/are ground with diamond wheels using conventional surface grinding machine. This research is carried out for the purpose of saving machining technology required for manufactiring Fine Ceramics parts

• 한국식품조리과학회지
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• 제27권1호
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• pp.85-99
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• 2011

Grinding is an indispensible step in preparation of espresso coffee. The purpose of this study was to evaluate physicochemical and sensory characteristics of espresso according to the grinding grades of coffee beans. Specifically, physicochemical characteristics according to the grinding grades of coffee beans were tested based on foam index, persistence of foam, total solids, concentration, extraction yield, pH, viscosity, total soluble solid content and density. With regard to sensory characteristics, QDA were carried out by 10 trained panels. Persistence of foam, total solids, concentration, extraction, pH and viscosity in physicochemical test showed significant differences among the three categories of the samples. In other words, the finer the size of particles was, the higher value was, at the p=0.001 value. Meanwhile, the value of foam index and total soluble solid content to the grinding grades was the highest in 'fine', at the p=0.001 value. Tiger-skin effect in crema, an important attribute for excellent espresso coffee, was perceived by all of the panels in 'fine'. Also, intensity of flavor was perceived as to the strongest in 'fine'. Moreover, 'fine' had the sweetness to balance the acids and bitters. In conclusion, according to the grinding grades, it was identified that there were differences in the physicochemical and sensory characteristics. Furthermore, when the size of particles was 'fine', it brought to the most positive result.

• 한국식품저장유통학회지
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• 제21권1호
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• pp.75-81
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• 2014

초미세 분쇄를 하였을 때 입자가 작아질수록 추출수율이 높아져 약 2.5배 높은 추출수율을 나타내었다. 일반 분쇄한 시료 추출물에서 69.8%의 전자공여능 억제효과가 관찰되었고, 미세분쇄와 초미세분쇄 추출물에서는 각각 70.7과 83.8%의 억제효과를 나타내었다. 일반분쇄 추출물과 미세분쇄 및 초미세분쇄 후 추출물 모두 97% 이상의 높은 ABTS 억제효과를 나타내어 분쇄 방법에 따른 항산화력의 차이는 거의 없었다. 일반 분쇄한 시료 추출물 보다 미세분쇄와 초미세분쇄 추출물에서 더 높은 PF값을 확인하였으며, 50% ethanol 초미세분쇄 추출물에서 1.8 PF로 가장 높은 항산화력을 나타내었다. 미세분쇄와 초미세분쇄 추출물에서는 일반분쇄 추출물에 비해 입자크기가 작아질수록 TBARS 억제율이 높아지며, 물 추출물보다 ethanol 추출물의 효과가 더 우수한 것으로 확인되었다. Xanthin oxidase 저해의 경우 초미세분쇄 후 효소억제 증대 효과를 확인할 수 있었다. Angiotensin converting enzyme 억제활성은 일반분쇄 추출의 경우 물 추출물에서는 억제활성이 나타나지 않았고, 50% ethanol 추출물에서 24%의 억제율이 확인되었다. 또한, ethanol 추출물의 억제효과가 물 추출물에 비해 상대적으로 우수하였다. 50% ethanol 초미세분쇄 추출물에서 Staphylococcus aureus, Escherichia coli에 대해서 아주 약한 항균효과를 나타내었을 뿐 나머지 추출물에서의 항균효과는 거의 관찰되지 않았다.