• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.285-293
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• 2006

Let X be a n-set and let A = [aij] be a $n {\times} n$ matrix for which $aij {\subseteq} X$, for $1 {\le} i,\;j {\le} n$. A is called a generalized Latin square on X, if the following conditions is satisfied: $U^n_{i=1}\;aij = X = U^n_{j=1}\;aij$. In this paper, we prove that every generalized Latin square has an orthogonal mate and introduce a Hv-structure on a set of generalized Latin squares. Finally, we prove that every generalized Latin square of order n, has a transversal set.

• Fashion & Textile Research Journal
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• v.3 no.2
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• pp.174-179
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• 2001

This study investigated the effect of aftertreatments such as using the softener or starch on the mechanical properties of knitted fabrics. The mechanical properties of fabrics, hand value(HV) and total hand value(THV) were measured and calculated by the KES-F system. The main results are as follows: The values of tensile energy(WT), coefficient of friction(MIU) and geometrical roughness(SMD) were increased by softener but decreased by starch treatment. However, the values of tensile linearity(LT), bending(B, 2HB), thickness(T) and weight(W) were increased by starch but decreased by softener treatment. Tensile resilience(RT) was increased not only by softener but also by starch treatment. It showed that the levels of FUKURAMI, NUMERI and SOFUTOSA were increased by the treatment of softener and the levels of KOSHI and SHARI were increased by the treatment of starch. Total hand value(THV) was lower in fabric with starch treatment than fabric with none treatment.

• Korean Journal of Materials Research
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• v.7 no.9
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• pp.744-749
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• 1997

본 연구에서는 고주파 유도경화처리한 중탄소강의 회전접촉 피로거동을 0.44wt.%C강과 0.55wt.%C강을 사용하여 조사하였다. 회전접촉 피로시험은 Polymet RCF-1 시험기에서 탄성유체 윤활 조건으로 회전속도 8,000rpm, 최대 Hertz응력 492kg/m$m^2$을 가하면서 실시하였다. 미세한 lath마르텐사이트가 고주파 유도경화한 0.44wt.%C강과 0.55wt.%C강의 표면경화층에 형성되었고 소량의 페라이트가 일부 형성되었으며 0.44wt.%C강과 0.55wt.%C에 비해 비교적 큰 페라이트가 나타났다. 회전접촉 피로시험 후 표면경도가 거의 유지되는 표면경화층에서 회전접촉 피로시험전에 비해 경도가 상승하였다. 이 경도증가량의 최대치($\Delta$ Hv$_{max}$)와 피로수명과의 관계를 조사한 결과 0.55wt.%C강이 0.44wt.%C강에 비해 회전접촉 피로중에 일어나는 소변형에 대한 높은 저항성에 주로 기인하여 $\Delta$ Hv$_{max}$값은 낮게 나타나고 피로수명은 높게 나타났다.

• Journal of Powder Materials
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• v.9 no.1
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• pp.43-49
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• 2002

Microstructural and mechanical characteristics of P/M 6061 Al alloy subjected to equal channel angular pressing (ECAP) were investigated. The P/M 6061 Al alloy had an intial grain size of approximately $20\mutextrm{m}$. An equiaxed ultra-fine grained structure with the mean grain size of $~50 \mutextrm{m}$ was obtained by four repetitive ECAP at 473 K. The microhardness of P/M 6061 Al alloy was drastically increased from about 40 Hv to 80 Hv by two repetitive ECAP at 373 K. However, the microhardness decreased with increasing ECAP temperature. The tensile stength of as-hot-pressed P/M 6061 Al alloy before ECAP was 95 MPa, whereas it increased to both 248 MPa after two repetitive ECAP at 373 K and 130 MPa after four repetitive ECAP at 473 K. The tensile properties of the ECAPed sample were compared with those of commercial cast 6061-O and 6061-T4 Al alloys.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.262-265
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• 2007

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look Images.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.180-184
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• 2008

Preliminary results are reported on ship detection using coherence images computed from crosscorrelating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, crosscorrelation of multi-look images yields the different degrees of coherence between the images and water. The polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV. In the next step, we examine the technique when the dual-polarization data are split into two multi-look images.

• Tribology and Lubricants
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• v.25 no.3
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• pp.192-196
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• 2009

This paper presents the hardness and wear characteristic of bronze metals, which are manufactured by a sintering process with a high pressuring technology. A bronze metal with a high hardness and anti-wear properties is usually used for a high pressure cylinder and a pin-bush bearing. The new bronze metal in which is manufactured for this experimental study shows very high hardness of 192${\sim}$220 Hv compared with that of a conventional bronze metal of 120${\sim}$140 Hv. The high hardness of new bronze metals is strongly related to the radical reduction of wear volumes and an improved surface roughness of operated worn surfaces. As explained by previous many research works, the improved hardness of nonferrous metals may increase a load-carrying capacity and anti-wear properties of tribological components.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.176-181
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• 2001

Reflow soldering characteristics of Sn-3.5Ag and Sn-37Pb balls for BGA(Ball grid Array) were investigated. Diameter of 0.76mm ball was set on a Cu/Ni/Au-coated pad and reflowed in air with changing peak soldering temperature and conveyor speed. Peak temperatures were changed from 240 to 28$0^{\circ}C$ for Sn-3.5Ag, and from 220 to 26$0^{\circ}C$ for Sn-37Pb balls. As results, heights of solder balls increased and widths decreased with peak soldering temperature. Through aging treatment at 10$0^{\circ}C$ for 1.000 hrs, average hardness of Sn-3.5Ag balls bonded at 25$0^{\circ}C$ cecreased from 14.90Hv to 12.83Hv And with same aging conditions, average shear strength of Sn-3.5Ag balls bonded at 26$0^{\circ}C$ decreased from 1727gf to 1650gf.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.11a
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• pp.21-24
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• 1993

Many attempts have been made to use hydrogel as del ivory systems for various drug and vioactive materials to prolong and control their pharmacological activities. Rectal administration of drugs by using hydrogel bases, such as poloxamer ABA block copolymer (Pluronic F-127) gels, polyacrylic acid (Carbomer 934, 940, or 941) aqueous gels, and polyvilyl alcohol gels, have been reported on the preparation and potential suppository use of new gels(Eudragit L, Eudragit S, and Eudispert) that are block copolymers of methacrylic acid and methyl methacrylate. If) These hydrogel and xerogel preparations, especially Eudispert hv gels, show excellent staying and bioadhesive effects in the lower part of the rectum in rats and rabbits compared with those of polyethylene glycol (PEG)2000 and Witepsol H-15(or S-55) suppositories. Visual and optical microscopic observation of rectal membrances indicated no irritation or abnormality after administration of Eudispert hv tydrogel and xerogel.

• Journal of Welding and Joining
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• v.25 no.3
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• pp.72-77
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• 2007

This study deals with characterizations of microstructure and wear performance of a cladding layer, product on 1.9 mm-thick mild steel plate by the electric resistance welding, of composite metal powder of Coarse WC-6.5%Co and high carbon alloy (SHA). The cladding layer was examined and tested for microstructural features, chemical composition, hardness, and bondability. The cladding layer have two different matrix were observed by an optical microscope and EPMA. The one was the coarse WC-6.5Co structure. The other was the melted SHA with surrounding the WC-6.5Co structure. The hardness of WC-6.5Co was 1210HV. The hardness of SHA was 640HV.