• Journal of Power System Engineering
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• v.22 no.6
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• pp.58-66
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• 2018

The use of external gear pumps is an effective way to achieve adequate performance at low cost when composing hydraulic systems. The biggest drawback, on the other hand, is the accompanying noise. Gears of continuous contact shape are actively used for the pump recently. The continuous contact shape must be the helical type due to the nature of the gear pump that is driven only by the drive gear. In this paper the theoretical shape of continuous contact gear is analyzed using simple rack shape of straight lines and two circular arcs. Using such geometry, the theoretical equation will be developed by envelope curves according to the conjugate gear shape rules. After checking the validity of the theory by the shape of gear rules, the grinding shape was also developed. The 3D shapes using equation can be also drawn. It was also shown that contact ratio and radius of curvature are easily developed by the theoretical equations.

• Resources Recycling
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• v.3 no.2
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• pp.9-16
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• 1994

In this study, the grinding and wet cyclone process of the dust for the effective separation of high purity iron powder and iron oxide were investigated. The results obtained in this study can be summarized as follows: 1. By applying the wet cyclone technique for the iron powder(+200 mesh) produced from EC dust of the Kwangyang 2nd steel making factory, the iron powder of high content more than 99.76% of Fe was obtained with 47.66% yield at grinding time of 5 minutes by attritor. 2. The particle size distribution of the iron powder recovered from converter dust is quite simillar with the iron powder of sweden Hoganas Co.(W40.24, W40.29, W40.37, W40.37OX). 3. By using iron powder, copper ions are all adsorbed and removed in any concentration ranges of copper sulfate solution(Cu:100, 200, 300, 600 ppm).

• Korean Journal of Materials Research
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• v.22 no.9
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• pp.445-449
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• 2012

We investigate the effects of redox reaction on preparation of high purity ${\alpha}$-alumina from selectively ground aluminum dross. Preparation procedure of the ${\alpha}$-alumina from the aluminum dross has four steps: i) selective crushing and grinding, ii) leaching process, iii) redox reaction, and iv) precipitation reaction under controlled pH. Aluminum dross supplied from a smelter was ground to separate metallic aluminum. After the separation, the recovered particles were treated with hydrochloric acid(HCl) to leach aluminum as aluminum chloride solution. Then, the aluminum chloride solution was applied to a redox reaction with hydrogen peroxide($H_2O_2$). The pH value of the solution was controlled by addition of ammonia to obtain aluminum hydroxide and to remove other impurities. Then, the obtained aluminum hydroxide was dried at $60^{\circ}C$ and heat-treated at $1300^{\circ}C$ to form ${\alpha}$-alumina. Aluminum dross was found to contain a complex mixture of aluminum metal, aluminum oxide, aluminum nitride, and spinel compounds. Regardless of introduction of the redox reaction, both of the sintered products are composed mainly of ${\alpha}$-alumina. There were fewer impurities in the solution subject to the redox reaction than there were in the solution that was not subject to the redox reaction. The impurities were precipitated by pH control with ammonia solution, and then removed. We can obtain aluminum hydroxide with high purity through control of pH after the redox reaction. Thus, pH control brings a synthesis of ${\alpha}$-alumina with fewer impurities after the redox reaction. Consequently, high purity ${\alpha}$-alumina from aluminum dross can be fabricated through the process by redox reaction.

• Journal of Life Science
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• v.28 no.4
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• pp.465-471
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• 2018

Bee pollen is one of many types of alternative remedies, and it has been used for a long time throughout the world. It has numerous health effects, including antifungal, antibacterial, and antioxidant properties, immune modulation, enhanced cell proliferation, and even anti-carcinogenic effects. This study was designed to elucidate the effects of bee pollen on benign prostatic hyperplasia in rodents. For this experiment, we used nano-sized bee pollen produced through wet-grinding technology, thereby the extraction efficiency of the active ingredients in the bee pollen was significantly enhanced. First, We found that nano-sized bee pollen significantly reduced the size of prostates enlarged by chronic testosterone administration. In addition, nano-sized bee pollen significantly reduced the plasma concentration of the prostate-specific antigen (PSA). Interestingly, nano-sized bee pollen did not reduce the testosterone-induced increase in the plasma concentration of prostaglandin $E_2$ ($PGE_2$). The beneficial effects of nano-sized bee pollen in reducing both the size of the prostate and the plasma concentration of PSA was comparable to that of dutasteride. Finally, nano-sized bee pollen did not cause damage in LNCaP cells which are androgen-sensitive human prostate adenocarcinoma cells. Together, these data indicate that nano-sized bee pollen may be able to be used as a good alternative remedy for the treatment of benign prostatic hyperplasia.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.595-607
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• 1999

The purpose of this in vitro study was to evaluate the efficacy of self-etching primer which was developed to simplify the bonding procedures by measuring the shear bond strength and observing the interfacial morphology. 90 flat dentinal surfaces were prepared by grinding the buccal and lingual areas of caries-free human deciduous molars. After bonding of composite resin to sample surfaces according to the manufacturer's direction and thermocycling, shear bond strengths were measured using Universal testing machine(Instron). Another groups of specimens were treated by hydrochloric acid to secure the resin only and those tags were evaluated under SEM for their length and forms and the morphology of the bonding sites were also observed. The result as follows. 1. Group III showed higher shear bond strength than group I and II but no statistically significant difference was founded between group I and II(p>.05). 2. Adhesive failure was predominant in group II whereas dentin detachment was the main failure pattern in group I and III. 3. Relating long resin tags of $100-200{\mu}m$ were observed in samples of all groups under SEM. In group I, homogeneously long resin tags were arranged rather tight whereas rather loosely arranged resin tags of various length were found in group II. Lateral branching of resin tags was the characteristic finding observed in group III.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.8-13
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• 2012

The flexography ink has disadvantage in a deinking process because it tends to form too fine particles in alkali condition to be removed in flotation deinking. The influence of pH conditions on the particle size of phthalocyanine cyan ink used for flexo-printing was investigated to see the effect of pH conditions on flexography ink dispersion. Flexography ink particles prepared by grinding dried ink films were used in this experiment. Greater reduction of the ink particle size was noticed under alkaline pH condition, which was attributed to dissolution of resin component of the ink. Adsorption behavior of flexography ink onto pigment particles was examined using clay and talc as substrate pigments. Pretreatment of inorganic pigments with a cationic poly-DADMAC increased the surface adsorption of flexography ink particles, which improved the removal of the inks by centrifugal sedimentation of inorganic pigments. Most efficient removal of the ink particles was achieved when an optimal addition level of the cationic polymer was used for pretreatment of inorganic pigments, and this optimal addition level corresponds to the surface saturation point of the polyelectrolyte. Adsorption of flexography ink particles onto inorganic pigments improved the ink removal in flotation deinking since the pigment particles has the optimal particle size for flotation deinking.

• Journal of Pharmaceutical Investigation
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• v.2 no.1
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• pp.5-13
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• 1972

There are some repels in which they studied on the change of acid-consuming capacity of aluminium hydroxide resulted from the passing of time. However, the relationship between grain sizes(particle sizes) and the acid-consuming capacity of dried aluminium hydroxide gel was not been studied. And studies on the grain sizes of aluminium hydroxide gel qualified by pharmacopoeia of Korea has not been reported. For the purpose of studying these two problems, the author prepared two-kinds of aluminium hydroxide gel as follows : $Na_2OAl_2O_3+CO_2------{\longrightarrow}Al(OH)_3{\cdots}{\cdots}{\cdots}$sample 1 $Al_2(SO_4)_318H_2O+6NaHCO_3{\longrightarrow}Al(OH)_3{\cdots}{\cdots}{\cdots}$sample 2 Both of sample 1 and 2 are found to be amorphous by X-ray diffraction methods, and their acid-consuming capacities were determined by the method of pharmacopeia of Korea. The grain size was measured by X-ray diffraction method, the particle sizes observed by electron microscopy, and the change of acid-consuming capacity with passing of time was determined by the method of pharmacopoeia of Korea. The results of these studies are summerized as follows: 1. The grain size was linearly enlarged as the time goes by. The aluminium hydroxide gel gradually crystallized in a certain period of time. 2. The acid-consuming capacity was in exponential function, decreased as the grain size of them enlarged. 3. One particle consists of tens of grains.4. Grinding the Sample obtained in any period of testing time in mortar did not change both their grain size and their acid-consuming capacity. 5. The grain size of dried aluminium hydroxide gel ought to be micronized less than $100{\AA}$ for maintaining the ability such as consumes 250m1 of 0. 1N-HC1 solution per Is of $Al(OH)_3$ described in pharmacopoeia of Korea.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.4
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• pp.114-119
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• 2003

The fermentative conversion of food wastes into probiotic feed was investigated by seeding of mixed inoculum of Lactobacillus acidophilus and Saccharomyces cerevisiae. After grinding finely, optimal fermentation conditions for aeration was investigated at $30^{\circ}C$, The viable cell count of lactic acid bacteria and yeast during fermentation were monitored by controlling aeration rate at each different aeration degree of 0v.v.m 0rpm, 0.25v.v.m 100rpm, 0.5v.v.m 200rpm, and 1v.v.m 500rpm respectively. The most active growth of the yeast was shown at 0.5v.v.m 200rpm as $4.5{\times}10^9CFU/m{\ell}$. By controlling aeration rate, the pH of the probiotics feed could be controlled between 4-5 for the enhancement of preservation characteristics and acceptability for cattle feeding.

• Advanced Composite Materials
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• v.18 no.2
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• pp.187-195
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• 2009

Much attention has been paid to the processing of inorganic whisker, especially calcium carbonate whisker, which can be used as reinforcement materials of polymer composite due to its low price. Unfortunately, the present synthesis technique of calcium carbonate whisker starts from calcinations of limestone, which involves high energy consumption and furthermore is a highly environment polluting reaction. In this report, needle-like aragonite was synthesized with a reversible solution reaction from limestone without calcination. Optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to characterize the morphology and crystal structure of intermediates as well as that of the product, aragonite. GCC (grinding calcium carbonate) powder was dissolved in an aqueous solution of magnesium sulfate with reflux and air flush. EDTA titration was used to evaluate reaction rate of the dissolution. A kinetics equation of the dissolution reaction was constructed, which displayed second-order kinetics with respect to the concentration of magnesium sulfate. A rate constant of $0.0015\;l^{-3}{\cdot}mol^{-1}{\cdot}h^{-1}$ was obtained. The dissolution reaction gave fiber-like magnesium hydroxide sulfate and gypsum crystal. Then needle-like aragonite with a length of $9.13\;{\pm}\;1.02\;{\mu}m$ and an aspect ratio of $5.64\;{\pm}\;1.37$ was synthesized from the dissolution product with $CO_2$ bubbling at $70^{\circ}C$.

• Journal of Ginseng Research
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• v.44 no.1
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• pp.154-160
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• 2020

Background: Korean ginseng (Panax ginseng Meyer) powder is in rising demand because powder forms of foods are convenient to handle and are highly preservable. However, ginseng powder (GP) manufactured using the conventional process of air drying and dry milling suffers nutrient destruction and a lack of microbiological safety. The objective of this study was to prepare GP using a novel process comprised of UV-TiO₂ photocatalysis (UVTP) as a prewashing step, wet grinding, high hydrostatic pressure (HHP), and freeze-drying treatments. Methods: The effects of UVTP and HHP treatments on the microbial population, ginsenoside concentration, and physiological characteristics of GP were evaluated. Results: When UVTP for 10 min and HHP at 600 MPa for 5 min were combined, initial 4.95 log CFU/g-fw counts of total aerobes in fresh ginseng were reduced to lower than the detection limit. The levels of 7 major ginsenosides in UVTP-HHP-treated GP were significantly higher than in untreated control samples. Stronger inhibitory effects against inflammatory mediator production and antioxidant activity were observed in UVTP-HHP-treated GP than in untreated samples. There were also no significant differences in CIELAB color values of UVTP-HHP-treated GP compared with untreated control samples. Conclusion: Combined processing of UVTP and HHP increased ginsenoside levels and enhanced the microbiological safety and physiological activity of GP.