• Title/Summary/Keyword: D/N value

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A study on the fatigue and fracture characteristics of localized nuclear reactor vessel material (국산 원자로용기 재료의 피로 및 파괴특성 연구)

  • Jeong, Sun-Eok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1626-1635
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    • 1997
  • It is important to ensure the reliability of the first localized reactor vessel steel. To satisfy with this purpose, a study on the impact/hardness, low cycle fatigue(LCF), crack growth rate(da/dN) and fracture toughness( ) of base material(BM) and weld metal(WM) were performed under room temperature air and corrosion conditions. A summary of the results is as folows : (1) Charpy impact absorbed energy of BM was the highest value, heat affected zoon(HAZ) and the lowest, WM. The hardness of BM was similar to HAZ. (2) Coefficients of Manson equation using the monotonic tensile test data were obtained for the present material. (3) The effects of stress ratio and ambient (120.deg. C and NaCl) condition on da/dN were investigated, da/dN with NaCl condition expressed the highest value. (4) The results of Charpy V-notch impact test had good correlation with KIC characteristics and the lowest curve of KIC for BM was derived, more researches about WM and HAZ are required hereafter.

A Bottleneck Search Algorithm for Digraph Using Maximum Adjacency Merging Method (최대 인접 병합 방법을 적용한 방향 그래프의 병목지점 탐색 알고리즘)

  • Lee, Sang-Un
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.5
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    • pp.129-139
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    • 2012
  • Given digraph network D=(N,A),nN,a=c(u,v)A with source s and sink t, the maximum flow from s to t is determined by cut (S, T) that splits N to sS and tT disjoint sets with minimum cut value. The Ford-Fulkerson (F-F) algorithm with time complexity O(NA2) has been well known to this problem. The F-F algorithm finds all possible augmenting paths from s to t with residual capacity arcs and determines bottleneck arc that has a minimum residual capacity among the paths. After completion of algorithm, you should be determine the minimum cut by combination of bottleneck arcs. This paper suggests maximum adjacency merging and compute cut value method is called by MA-merging algorithm. We start the initial value to S={s}, T={t}, Then we select the maximum capacity maxc(u,v) in the graph and merge to adjacent set S or T. Finally, we compute cut value of S or T. This algorithm runs n-1 times. We experiment Ford-Fulkerson and MA-merging algorithm for various 8 digraph. As a results, MA-merging algorithm can be finds minimum cut during the n-1 running times with time complexity O(N).

Mechanical Properties of DLP-type Dental 3D Printing Temporary Tooth Material (DLP방식의 치과용 3D프린팅 임시치아 소재의 기계적 특성)

  • Jung, Hyo-Kyung;Lee, Seung-Hee;Jung, Hyo-Kyung
    • Journal of the Korean Society of Industry Convergence
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    • v.24 no.3
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    • pp.373-376
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    • 2021
  • Tested the flexural strength and maximum load of two types of dental 3 D printed temporary tooth materials of the DLP method. The average flexural strength was 206.98 MPa in the test group and 139.77 MPa in the control group. The average flexural strength of the experimental group was 67.21 MPa higher than that of the control group. In the maximum load experiment, an average of 44.16N in the experimental group and 37.31N in the control group were measured. The average value of 6.85N was higher in the experimental group, and the durability of the artificial tooth restoration was improved.

A Study on the Correlation Between Nugget Diameter and Contact Diameter of Sheets by Electrode Force (點熔接 의 너깃지름 과 板間接觸지름 의 關聯性)

  • 송삼홍;김부동
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.7 no.3
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    • pp.313-318
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    • 1983
  • It is required in designing a spot welding to get in advance an estimated figure of nugget diameter. A method of estimating nugget diameter of low carbon steel sheets is suggested in tesms of utilizing elastic calculation in theory and of making a sectional observation of specimen of spot welding in experiment. The resultant findings are summarized as follows: 1) A contact diameter of sheet, 2.gamma.o=d sub e/+(1.1)t, wheer de is the electrode tip diameter and t is the thickness of sheets. 2) The practical measurement of the nugget diameter reveals that dn=(1.05) de+(0.9)t, and db is less by 0.8-4.3% than 2.gamma.o. 3) The more dn is as compared with t, the less the difference between a theoretical value and an experimental value is. 4) In the spot welding of thin steel sheets less than 3mm in thickness that are commonly used in sheet metal works, the contact diameter equals the nugget diameter. In this case, either the theoretical or experimental approach can be used for estimating the nugget diameter.meter.ter.r.

RF High Power Amplifier Module using AlN Substrate (AlN 기판을 이용한 RF 고전력 증폭기 모듈)

  • Kim, Seung-Yong;Nam, Choong-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.10
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    • pp.826-831
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    • 2009
  • In this paper, a high power RF amplifier module using AlN substrate of high thermal conductivity has been proposed. This RF amplifier module has the advantage of compact size and effective heat dissipation for the packaging of high power chip. To fabricate the thru-hole and scribing line on AlN substrate, the key parameters of CO2 laser were experimented. And then, microstrip lines and spiral planar inductors were fabricated on an AlN substrate using the thin-film process. The fabricated microstrip lines on the AlN substrate has an attenuation value of 0.1 dB/mm up to 10 GHz. The fabricated spiral planar inductor has a high quality factor, a maximum of about 62 at 1 GHz for a 5.65 nH inductor. Packaging of a RF power amplifier was implemented on an AlN substrate with thru-hole. From the measured results, the gain is 24 dB from 13 to 15 GHz and the output power is 33.65 dBm(2.3 W).

Extreme Value of Moving Average Processes with Negative Binomial Noise Distribution

  • Park, You-Sung
    • Journal of the Korean Statistical Society
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    • v.21 no.2
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    • pp.167-177
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    • 1992
  • In this paper, we investigate the limiting distribution of Mn=max(X1,X2,,Xn) in the infinite moving average process Xt=ciZti generated from i.i.d. negative binomial variables Zi's. While no limit result is possible, nonetheless asymptotic bounds are derived. We also present the tail behavior of Xt, i.e., weighted sum of i.i.d. random variables. This continues a study made by Rootzen (1986) for discrete innovation sequences.

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A Heuristic Algorithm for n/m/D/F/Fmax (Flow Shop에서 준비시간이 작업순서에 종속적인 경우의 휴리스틱 알고리듬의 개발)

  • 최성운
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.8 no.11
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    • pp.79-83
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    • 1985
  • This paper is to develop four heuristic algorithms for n/m/D/F/Fmax. A study present numerical example for (H1) algorithm. Among the sequence generated, the best sequence is J2, J1, J6, J7, J4, J3, J5 and makespan is 528. The optimal makespan of this numerical example can be found as 528 as also, and the worst value of heuristic solution is only 7.2 % away from it.

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A Use of Heterotrophic Denitrification for the Supply of Alkalinity during Sulfur-utilizing Autotrophic Denitrification (황-이용 독립영양 탈질시 알칼리도 저감을 위한 종속영양 탈질의 이용방안)

  • Lee, Dong-Uk;Park, Jae-Hong;Bae, Jae-Ho
    • Journal of Korean Society of Environmental Engineers
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    • v.22 no.11
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    • pp.1995-2005
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    • 2000
  • The use of heterotrophic denitrification as an alternative method for supplying alkalinity during sulfur-utilizing autotrophic denitrification was evaluated by examining the effects of external carbon source (both type and concentration) and HRT on denitrification efficiency. Concentrations of NO3N and CODCr of nitrified landfill leachate used for experiment were 700-900mg/L and 900-2500mg/L. respectively, All experiment was conducted with sulfur packed bed reactors (SPBRs) which were operated at 35C. The fraction of NO3N removed by heterotrophic denitrification (HDNRfraction) to balance the alkalinity consumption by autotrophic denitrification varied with the type of external carbon source. When methanol and sodium acetate was added at theoretical HDNRfraction value. 100% denitrification was achieved without alkalinity addition. However, glucose and molasses require HDNRfraction value greater than theoretical value for complete denitrification. The EBCT and volumetric loading rate at which 100% denitrification efficiency could be achieved were 6.76 h and 2.84kgNO3N/m3d, respectively, based on the fact that 100% denitrification occurred within the bottom 11.5 cm layer of the SPBR. The maximum nitrogen removal rate occurred with 89% removal efficiency at loading rate of 5.05kgNO3N/m3d. However, at short EBCT, clogging of SPBR was observed with excess growth of heterotrophic denitrifiers. This problem may be eliminated by back washing or by separating of heterotrophic denitrification from sulfur-utilizing denitrification.

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First-principles Study on the Half-metallicity and Magnetism for the Heusler Based Compounds of N(2-0.5n)O0.5nKCa (n=0~4) (호이슬러 구조 기반의 N(2-0.5n)O0.5nKCa (n = 0~4) 화합물의 반쪽금속성 및 자성에 대한 제일원리 연구)

  • Bialek, Beata;Lee, Jae Il
    • Journal of the Korean Magnetics Society
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    • v.23 no.6
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    • pp.179-183
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    • 2013
  • The half-metallicity and magnetism for compounds of the N(20.5n)O0.5nKCa (n = 0~4), which was based on the d0 Heusler half-metals of N2KCa and O2KCa, were investigated by means of first-principles band calculation method. From the calculated total magnetic moments and the density of states, we found that these three compounds have the half-metallicity. The magnetic moments of the N and O atoms in these compounds were considerably increased compared to those of pure N2KCa and O2KCa. The K atoms have a large negative magnetic moments. The relationship between the value of magnetic moments for each atom and density of states are discussed.

Brazing of Aluminium Nitride(AlN) to Copper with Ag-based Active Filler Metals (은(Ag)계 활성금속을 사용한 질화 알미늄(AlN)과 Cu의 브레이징)

  • Huh, D.;Kim, D.H.;Chun, B.S.
    • Journal of Welding and Joining
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    • v.13 no.3
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    • pp.134-146
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    • 1995
  • Aluminium nitride(AlN) is currently under investigation as potential candidate for replacing alumium oxide(Al2 O3) as a substrate material for for electronic circuit packaging. Brazing of aluminium nitride(AlN) to Cu with Ag base active alloy containing Ti has been investigated in vacuum. Binary Ag98 Ti2(AT) and ternary At-1wt.%Al(ATA), AT-1wt.%Ni(ATN), AT-1wt.% Mn(ATM) alloys showed good wettability to AlN and led to the development of strong bond between brate alloy and AlN ceramic. The reaction between AlN and the melted brazing alloys resulted in the formation of continuous TiN layers at the AlN side iterface. This reaction layer was found to increase by increase by increasing brazing time and temperature for all filler metals. The bond strength, measured by 4-point bend test, was increased with bonding temperature and showed maximum value and then decreased with temperature. It might be concluded that optimum thickness of the reaction layer was existed for maximum bond strength. The joint brazed at 900.deg.C for 1800sec using binary AT alloy fractured at the maximum load of 35kgf which is the highest value measured in this work. The failure of this joint was initiated at the interface between AlN and TiN layer and then proceeded alternately through the interior of the reaction layer and AlN ceramic itself.

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