• Journal of Life Science
• /
• v.9 no.2
• /
• pp.194-200
• /
• 1999

Grinding aid is a necessary unit operation when the raw materials are handled in solid form, and the purpose is to improve the bioavailability by reducing the particle size. For the particle design of pefloxacin, the dry planetary ball-mill was used. With the drying process, 330 g of zirconia ball with its size of 2 mm in diameter and 10 g of pefloxacin were transferred to the pot and mixed well. The mixture was ground at 112 rpm (60 Hz) for 15, 30, and 60 min, respectively. The most satisfactory grinding products were generated at 15 min of grinding time for their particle size. The volume mean diameter $\X_50$ of the grinding products was 2.97 $\mu$m. X-ray diffraction (XRD), differential scanning calorimeter (DSC), and infrared spectroscopy (IR) patterns were relatively unchanged before pulverizing pefloxacin and in the progress of grinding. Thus, these results suggest that this pulverizing method can be used for grinding products without evident effect on stability of the drug pefloxacin. Dissolution test was carried out to set up the optimal detective condition against residual antibacteria of fish by HPLC. The grinding pefloxacin for 15 min is most effective in dissolution test.

• Journal of the Mineralogical Society of Korea
• /
• v.21 no.2
• /
• pp.129-138
• /
• 2008

The characteristics of beneficiating kaolin mineral by liberation (selective grinding) and air classification have been investigated, comparing the grinding rates of ball mill and impact mill. The ore was ground using a ball mill and a impact mill to evaluate the grindability of the two grinding methods based on the constant production amount of fine particles in size less than 325 mesh. Then, the fine product was further separated into two fractions using an air-classifier and each fraction was chemically analyzed to compare the beneficiation efficiency of the two grinding methods. The chemical grade of kaolin mineral decreased as increasing the grinding rate of both the mills. particularly in the case of ball mill because of overgrinding impurities such as quartz and feldspar. In the case of the ball milling, the fine fraction less than 325 mesh was air-classified at a cutting point of $43\;{\mu}m$. The production rate of the air-classified concentrate was found to be 66.2 wt%, removing 5.3% of $Fe_2O_3$ and 34.6% of CaO. Under the same conditions mentioned above with the impact mill, the production rate of the air-classified concentrate was 64.4 wt%, removing 34.2% of $Fe_2O_3$, 67.6% of CaO and 25.0% of $TiO_2$. Therefore, our results indicate that impact mill is superior to ball mill in terms of impurity removal.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.962-967
• /
• 2003

Recently, environmental pollution has become a serious problem in industry, and many researches have been done in order to preserve the environment. The coolant, which promotes lubrication, cooling and penetration, contains chlorine, sulfur and phosphorus to improve the machining efficiency. These additives, which move around into the air during machining, pollute working. Therefore, many researches on how to reduce the amount of coolant during machining have been carried out. However, to reduce even small amount of coolant causes high temperature of a workpiece and it brings thermal defects. In this study, the experiments of wet & dry grinding using cooling methods (using coolant only, mist and compressed cold air only) are performed to solve the problem of environmental contamination and to get a better surface integrity of a workpiece by comparing surface roughness, roundness and residual stress.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.129-132
• /
• 2003

Used cutting fluid from machining processes is harmful to both environment and human health. Chemical substances that provide the lubrication function in the machining process are toxtc to the environment if the cutting fluid is released to soil and water and caused serious health problems to workers who are exposed to the cutting fluid in both liquid and mist form. Recently. cost of using cutting fluid is increasing as the number and the extensiveness of environmental protection laws and regulations increase. Therefore, the use of cutting fluid in machining processes place an enormous burden on manufacturing companies to cover the additional costs associated with their use and protection of our environment. Current trends in manufacturing are focused on minimizing or eliminating the use of metalworking fluids in machining processes. And the increased costs for the disposal of waste products (swarf, coolants and lubricants), especially in industrially developed countries, has generated interest in dry machining. A variety of new techniques are testimony that new technology has rationalized further efforts to research and implement dry machining processes. This paper presents the developed equipment, the process optimization and the applications in the field of surface grinding for the new cryogenic dry machining using a compressed cooling air. The investigated new machining process method shows many advantages compared to conventional techniques with cutting fluid.

• Korean journal of food and cookery science
• /
• v.31 no.5
• /
• pp.544-550
• /
• 2015

This study investigated the quality characteristics of English muffins made rice flour created using different grinding methods (DPR: powdered type rice flour by dry milling. DSR: soft type rice flour by dry milling. DHR: hard type rice flour by dry milling. WPR: powdered type rice flour by wet milling. WSR: soft type rice flour by wet milling. WHR: hard type rice flour by wet milling). The volume, volume expansion, and specific volume were the highest in WPR. The shape and cross section indicated that WPR, WSR and DPR were the best quality. The L value was the highest in DHR, the b value was the highest in DPR. Hardness, gumminess and chewiness were the lowest in WPR, and the highest in DHR. According to result of the sensory evaluation, the color, flavor, appearance, texture and overall acceptability were the highest in WPR, while the taste preference was the highest in WSR.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.128-128
• /
• 2010

In this study, we investigated the evolution and reduction of the surface roughness during the high-speed chemical dry thinning process of Si wafers. The direct injection of NO gas into the reactor during the supply of F radicals from NF3 remote plasmas was very effective in increasing the Si thinning rate, due to the NO-induced enhancement of the surface reaction, but resulted in the significant roughening of the thinned Si surface. However, the direct addition of Ar and N2 gas, together with NO gas, decreased the root mean square (RMS) surface roughness of the thinned Si wafer significantly. The process regime for the increasing of the thinning rate and concomitant reduction of the surface roughness was extended at higher Ar gas flow rates. In this way, Si wafer thinning rate as high as $20\;{\mu}m/min$ and very smooth surface roughness was obtained and the mechanical damage of silicon wafer was effectively removed. We also measured die fracture strength of thinned Si wafer in order to understand the effect of chemical dry thinning on removal of mechanical damage generated during mechanical grinding. The die fracture strength of the thinned Si wafers was measured using 3-point bending test and compared. The results indicated that chemical dry thinning with reduced surface roughness and removal of mechanical damage increased the die fracture strength of the thinned Si wafer.

• Restorative Dentistry and Endodontics
• /
• v.25 no.2
• /
• pp.243-253
• /
• 2000

The purpose of this in vitro study was to evaluate dentin bonding by two different dentin bonding systems(DBS) using acetone based primer or adhesive [All Bond 2(AB2), One Step(OS)] when they were applied by wet or dry bonding technique. Morphology of resin-dentin interface and hybrid layer thickness(HLT) were investigated using Confocal Laser Scanning Microscope(CLSM) and compared to shear bond strength(SBS). 72 extracted sound human molars were randomly divided into 4 groups of 18 teeth each - Group 1.(AW); AB2 by wet bonding. Group 2(AD); AB2 by dry bonding. Group 3.(OW); OS by wet bonding, Group 4.(OD); OS by dry bonding. In 6 teeth of each group, notch-shaped class V cavities(depth 2mm) were prepared on buccal and lingual surface at the cementoenamel juction(12 cavities per group). To obtain color contrast in CLSM observation, bonding resins of each DBS were mixed with rhodamine B and primer of AB2 was mixed with sodium fluorescein. Prepared teeth of each group were treated with AB2, OS, respectively according to the manufacturer's instructions except for dentin surface moisture treatment after acid etching. In group 1 and 3, after acid etching, excess water was removed with wet tissue(Kimwipes), leaving consistently shiny, visibly hydrated dentin surface. In group 2 and 4, dentin surface was dried for 10 seconds at 1 inch distance. The treated teeth were then packed with composite resin(${\AE}$litefil) and light-cured. 12 microscopic samples($60{\sim}80{\mu}m$ thickness) of each group were obtained after longitudinal section and grinding(Exakt cutting and grinding system). Morphological investigation of resin-dentin interface and HLT measurement using CLSM were done. For measurement of SBS, remaining 12 teeth of each group were flattened occlusally to remove all enamel and grinded to 500 grit SiC(Pedemet Specimen Preparation Equipment). After applying DBS on the exposed dentin surface, composite resin was applied in the shape of cylinder, which has 5mm diameter, 1.5mm thickness, and light cured. SBS was measured using Instron with a crosshead speed of 0.5mm/min. It was concluded as follows, 1. HLT of AW(mean: $2.59{\mu}m$) was thicker than any other group, and followed by AD, OW, OD in descending order(mean; 2.37, 2.28, $1.92{\mu}m$). Only OD had statistically significant differences(p<0.05) to AW and AD. 2. There were intimate contact of resin and dentin at the interface in wet bonding groups, but gaps or irregular interfaces were observed in dry bonding groups. 3. The length, diameter, density of resin tags were various even in the same group without significant differences between groups and lots of adhesive lateral branches were observed. 4. There were no statistically significant difference of SBS between AB2 and OS, but SBS of wet bonding groups were significantly higher(p<0.05) than dry bonding groups. 5. There were no consistent relationships between HLT and SBS.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.26 no.1
• /
• pp.53-62
• /
• 2006

Near infrared reflectance spectroscopy (NIRS) has been increasingly used as a rapid, accurate method of evaluating some chemical compositions in forages. Analysis of forage quality by NIRS usually involves dry ground samples. Costs might be reduced if samples could be analyzed without drying or grinding. The objective of this study was to investigate effect of sample preparations and spectral math treatments on prediction ability of chemical composition for corn silage by NIRS. A population of 112 corn silage representing a wide range in chemical parameters were used in this investigation. Samples of com silage were scanned at 2nm intervals over the wavelength range 400-2500nm and the optical data recorded as log l/Reflectance(log l/R) and scanned in overt-dried grinding(ODG), liquid nitrogen grinding(LNG) or intact fresh(IF) condition. Samples were analysed for neutral detergent fiber(NDF), acid detergent fiber(ADF), acid detergent lignin(ADL), crude protein(CP) and crude ash content were expressed on a dry-matter(DM) basis. The spectral data were regressed against a range of chemical parameters using modified partial least squares(MPLS) multivariate analysis in conjunction with four spectral math treatments to reduce the effect of extraneous noise. The optimum calibrations were selected on the basis of minimizing the standard error of cross validation(SECV). The results of this study show that NIRS predicted the chemical parameters with very high degree of accuracy(the correlation coefficient of cross validation$(R^2cv)$ range from $0.70{\sim}0.95$) in ODG. The optimum equations were selected on the basis of minimizing the standard error of prediction(SEP). The Optimum sample preparation methods and spectral math treatment were for ADF, the ODG method using 2,10,5 math treatment(SEP = 0.99, $R^2v=0.93$), and for CP, the ODG method using 1,4,4 math treatment(SEP = 0.29. $R^2v=0.91$).

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.2
• /
• pp.63-67
• /
• 2008

3D integration technology has been a major focus of the next generation of IC industries. In this study Si wafer ultra-thinning has been investigated especially for the effect of ultra-thinning on the silicon surface. Wafers were grinded down to $30{\mu}m\;or\;50{\mu}m$ thickness and then grinded only samples were compared with surface treated samples in terms of surface roughness, surface damages, and hardness. Dry polishing or wet etching treatment has been applied as a surface treatment. Surface treated samples definitely showed much less surface damages and better roughness. However, ultra-thinned Si samples have the almost same hardness as a bulk Si wafer.

• The Journal of Advanced Prosthodontics
• /
• v.8 no.4
• /
• pp.259-266
• /
• 2016

PURPOSE. The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS. 120 specimens ($10{\times}10{\times}2mm$) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with $125{\mu}m$ grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS. Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION. SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin.