• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.243-249
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• 2001

This paper has been presented the hydrodynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing the two row source position of air bearing is different from existed investigations in the side of pressure distribution of air film because of the high speed of journal and the wedge effects by the eccentricity. These optimal chooses of the two row source positions enable us to improve the performance of the film reaction force and loading force as making the high speed spindle. In this paper, the pressure behavior in theory of air film according to the eccentricity of journal and the source positions analyzed. The theoretical analysis have been identified by experiments. The results of investigated characteristics may be applied to precision devices like ultra-precision grinding machine and ultra high speed milling.

• 한국미생물·생명공학회지
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• 제8권2호
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• pp.125-133
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• 1980

토양으로부터 분리한 포도당 이성화효소를 강하게 생산하는 방사균을 Bergey's manual 8판에 따라 동정한 결과 Streptomyces antibioticus 근록의 균주이었다. 본 균의 배양액으로부터 균체를 모아서 해사를 넣고 파쇄 하여 증류수로 추출하고 Mn-처리를 하여 핵단백질을 제거한 후 황산 ammonia 분획침전(0.5∼0.8포화), 수석, DEAE-cellulose column chromatography, DEAE-sephadex (A-50) column chromatography 및 sephadex G-200에 의한 gel filtration을 거쳐 비활성도로 약 380배, 회수율 25％ 정도로 분리 정제하였다.

• 대한기계학회논문집
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• 제17권2호
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• pp.351-358
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• 1993

Recently a high speed spindle system for machine tools has attracted considerable attention to reduce the machining time, to improve the machining accuracy, to perform the machining of light metals and hard materials and to unite the cutting and grinding processes. In this study, a high speed spindle system is developed by applying the oil-air lubrication method, angular contact ball bearings, injection nozzles with dual orifices and so on. And a lubrication experiment for evaluating the performance of the spindle system is carried out. Especially, in order to establish the lubrication conditions related to the development of a high speed spindle system, the effects of oil supply rate, rotational spindle speed and so on are studied and discussed on the bearing temperature rise, bearing temperature distribution and frictional torque. And the effect of spindle system structure on the bearing temperature distribution is investigated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.969-972
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• 1997

Ultrasonic machining technology has been developed over recent years for he manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile application. The past decade has seen a tremendous in the use of ceramic in structural application. The excellent thermal, chemical and wear resistance of these material can be realized because of recent improvement in the overall strength and uniformity of advanced ceramics. Ultrasonic machining, in which abrasive particles in slurry with water are presented to the work surface in the presence of an ultrasonic-vibrating tool, is process which should be of considerable interest, as its potential is not limited by he electrical or chemical characteristics of the work material, making it suitable for application to ceramics. In order to improve the currently used ultrasonic machining using ultrasonic energy, technical accumulation is needed steadily through development of exciting device of ultrasonic machine composed of piezoelectric vibrator and horn. This paper intends to further the understanding of the basic mechanism of ultrasonic machining for brittle material and ultrasonic machining of ceramics based in the fracture-mechanic concept has been analyzed.

• 한국동물학회지
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• 제6권1호
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• pp.15-20
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• 1963

The characteristics of the pharyngeal bones and their teeth in Korean Cyprinids fishes, as a rule, are summarized as follow : 1. The materials 13 genera and 17 species from Nak Dong River. 2. Breadth of bone about 2.8(Cyprinus carpio) to 4.9(Culter brevicauda) in bone length. Length of bone about 8.5(Carassius carassius ) to 20.2 (Pseudogobio esocinus ) in body length. Breadth of pitted surface about 66%(Carassius carassius) to 85%(Acanthorhodeus asmussi ) of breadth of bone. 3. The position and distinct ratio of anterior angle correlated. 4. Posterior limb always longer than anteriro, but posterior edentulous process not shorter than anterior's or equal. 5. Zacco platypus with pitted surface on anterior limb , but Z.temmincki without it. 6. Teeth one to three rowed in accordance with the differences of each genus : a. one rowed genera ..... Carassius , Pseudorasbora, Sarcocheilichthys (Sakiyae), Pungtungia, Acheilognathus, Acanthorhodeus. b. two rowed genera ........ Pseudogobio, Gnathopogon, Tribolodon. c. Three rowed genera .... Cyprinus, Hemibarbus, Zacco , Culter 7. Teeth of main (primary ) row with four or five teeth is symmetrized exceptive three genera (Tribolodon, Zacco, Culter). 8. Grinding surface and bill type correlated. 9. In Acheilognathus, A.Yamatsutae have one or two indistinct serration but each individual is unlike.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.963-966
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• 2000

Plasma display panel (PDP) is a type of flat panel display utilizing the light emission that is produced by gas discharge. Barrier Ribs of PDP separating each sub-pixel prevents optical and electrical crosstalk from adjacent sub-pixels. Mold for forming barrier ribs has been newly researched to overcome the disadvantages of conventional manufacturing process such as screen printing, sand-blasting and photosensitive glass methods. Mold for PDP barrier ribs have stripes of micro grooves transferring stripes of glass-material wall. In this paper. Stripes of grooves of which width 48 um, depth 124um, pitch 274um was acquired by machining the material of WC with dicing saw blade. Maximum roughness of the bottom and sidewall of the grooves was respectively 120 nm, 287 nm. Maximum tilt angle caused by difference between upper-most width and lower-most width was 2$^{\circ}$. Maximum Radius of curvature of bottom was 7.75 ${\mu}{\textrm}{m}$. This results meets the specification for barrier ribs of 50 inch XGA PDP. Forming the glass paste will be followed by using mold in the near future.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.541-544
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• 2001

Orthorhombic $LiMnO_2$ was synthesized by solid-state reaction using $LiOH{\cdot}H_{2}O$ and $Mn_{2}O_{3}$ as starting material. Its electrochemical properties as cathode in lithium batteries were examined. X-ray diiffraction revealed that the $LiMnO_2$ compound showed a well-defined orthorhombic phase of a space group with Pmnm. The capacity of $LiMnO_2$ agreed well with its specific surface area and grinding treatment was effective in improving cycling performance. For lithium polymer battery applications. the $LiMnO_2$ cell was characterized electrochemically by charge-discharge experiments. And the relationship between the characteristics of powder and electrochemical properties was studied in this research. A maximum discharge capacity of $160-170mAhg^{-1}$ for $LiMnO_2/Li$ cell was achieved.

• 한국정밀공학회지
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• 제25권12호
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• pp.47-54
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• 2008

Hard turning process can be defined as a single-point machining process carried out on "hard" materials. The process is intended to replace or limit traditional grinding operations that are expensive, environmentally unfriendly, and inflexible. The purpose of this study is to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, tool wear shape and chip formation by the outer cutting of a kind of wear resistant tungsten carbide V30. Hard turning experiments were carried out on this alloy using the PCD (Poly Crystalline Diamond), cBN (cubic Boron Nitride) and PcBN (Polycrystalline cubic Boron Nitride) cutting tools. The PcBN and the usual cBN tools were used to be compare with the PCD tool and the dry turning was carried out. The PcBN is attractive as the tool material which replaces the PCD. The tool wear width and cutting force were measured, and the worn tool and chip were observed. The difference of the tool wear mechanism among the three tool materials was investigated.

• 펄프종이기술
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• 제47권2호
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• pp.42-52
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• 2015

In this study, cellulose nanofibrils (CNF) were modified through carboxymethylation or TEMPO-mediated oxidation and their effects on ionicity and characteristics of sheet, film, and foam were investigated. Carboxymethylation was carried out on pulp fibers as a pre-treatment before preparation of CNF. The gel-like and translucent CNF hydrogel was obtained by grinding of carboxymethylated cellulose fibers. Carboxymethylated CNF film and freeze dried sheet showed higher transparency than that of untreated CNF. The CNF sheet with high strength and the CNF foam without large ice crystals were obtained by using the carboxymethylated CNF. TEMPO-mediated oxidation was carried out as a post-treatment of CNF. The zeta potential and charge demand of TEMPO-oxidized CNF were increased with an increase in oxidation time and addition amount of NaClO. The density of sheet made of TEMPO oxidized CNF was increased with the amount of oxidizing agent. The TEMPO oxidized cellulose nanofiber (TOCN) which was obtained from supernatant after centrifugation could be converted to transparent film.

• Bulletin of the Korean Chemical Society
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• 제25권3호
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• pp.357-360
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• 2004

We developed in the present study molecular imprinted polymers (MIPs), using single templates (pentoxifylline, caffeine and theophylline) and mixed-templates (pentoxifylline-caffeine, pentoxifylline-theophylline and caffeine-theophylline). The MIPs were prepared with methacrylic acid (MAA) as the monomer, ethylene glycol dimetharylate (EGDMA) as the crosslinker and 2,2'-azobis(isobutyronitrile) (AIBN) as the initiator. The obtained polymer particles (particle size after grinding was about 25-35 ${\mu}$m) were packed into a HPLC column (3.9 mm i.d. ${\times}$ 150 mm). The selectivity and chromatographic characteristics of the MIPs were studied using acetonitrile as the mobile phase at a flow rate of 0.8 mL/min. UV detector wavelength was set at 270 nm. Different single template MIPs showed different molecular recognitions to the templates and the structurally analogues, according to the rigidity and steric hindrance of the compounds. Recognition was improved on the mixed-template MIPs as a result of the cooperation or sum effect of the templates, whereas on the pentoxifylline-theophylline imprinted polymer, the highest selectivity and affinity were obtained. Separations of the test compounds on different polymers were also investigated.