• Title/Summary/Keyword: dual matrix

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Brass fillers in friction composite materials: Tribological and brake squeal characterization for suitable effect evaluation

  • Kchaou, Mohamed;Sellami, Amira;Abu Bakar, Abd. Rahim;Lazim, Ahmad Razimi Mat;Elleuch, Riadh;Kumar, Senthil
    • Steel and Composite Structures
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    • v.19 no.4
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    • pp.939-952
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    • 2015
  • In this paper, brake pad performance of two organic matrix composites namely, Sample 1 (contains no brass filler) and Sample 2 (contains 1.5% brass filler), is studied based on tribological and squeal noise behavior. In the first stage, a pin-on-disc tribometer is used to evaluate the frictional behavior of the two pads. On the following stage, these pads are tested on squeal noise occurrence using a drag-type brake dynamometer. From the two type of tests, the results show that; (i) brass fillers play a dual role; firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material providing velocity accommodation between the pad and the disc; (ii) brass fillers contribute to friction force stabilization and smooth sliding behavior; (iii) the presence of small weight quantity of brass filler strongly contributes to squeal occurrences; (iv) there is close correlation between pin-on-disc tribometer and brake dynamometer tests in terms of tribological aspect.

2-D Periodic Unsteady Flow Analysis Using a Partially Implicit Harmonic Balance Method (부분 내재적 조화 균형법을 이용한 주기적인 2차원 비정상 유동 해석)

  • Im, Dong-Kyun;Park, Soo-Hyung;Kwon, Jang-Hyuk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.12
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    • pp.1153-1161
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    • 2010
  • An efficient solution method for harmonic balance techniques with Fourier transform is presented for periodic unsteady flow problems. The present partially-implicit harmonic balance treats the flux terms implicitly and the harmonic source term is solved explicitly. The convergence of the partially Implicit method is much faster than the explicit Runge-Kutta harmonic balance method. The method does not need to compute the additional flux Jacobian matrix from the implicit harmonic source term. Compared with fully implicit harmonic balance method, this partial approach turns out to have good convergence property. Oscillating flows over NACA0012 airfoil are considered to verify the method and to compare with results of explicit R-K(Runge-Kutta) and dual time stepping methods.

A Study of Structures and Magnetic Properties of Electrodeposited Fe-45 wt%Ni-P Alloys (전착법에 의한 Fe-45 wt%Ni-P 합금의 조직과 자기적 성질에 관한 연구)

  • 구승현;이흥렬;김동환;황태진;임태홍
    • Journal of the Korean institute of surface engineering
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    • v.36 no.6
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    • pp.461-465
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    • 2003
  • The microstructures and magnetic properties of electrodeposited Fe-45 wt%Ni-P alloys have been investigated. The structures of electrodeposited Fe-45 wt%Ni alloy was FCC i.e. ${\gamma}$ phase and the size of crystallite was 10 nm. The structure of electrodeposited Fe-45 wt%Ni-1 wt%P alloy showed ${\gamma}$ phase and 7 nm sized nanocrystalline. The electrodeposited Fe-45 wt%Ni-P alloys containing 2∼3 wt% of P exhibited ${\gamma}$$\alpha$ dual phases. The electrodeposited Fe-45 wt%Ni-P alloys above 3.5 wt% showed an amorphous structure. P in the alloys acted grain refining and phase changing element. The resistivity of the electrodeposited alloys increased with P contents. Effective permeability at high frequency (above 1 MHz) increased with P contents up to 2 wt% and this was ascribed to the easier magnetization rotation owing to the reduction of eddy current. Effective permeability decreased with P contents above 3 wt% and this was ascribed to the transformation of the ferromagnetism of Fe-45 wt%Ni alloy gradually into paramagnetism with the introduction of P into the electrodeposited alloy matrix.

A microstrip folded compact wideband band-pass filter with wide upper stopband

  • Hoseini, Seyyed Mojtaba Seyyed Najjar;Zaker, Reza;Monfaredi, Khalil
    • ETRI Journal
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    • v.43 no.6
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    • pp.957-965
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    • 2021
  • A miniaturized wideband band-pass filter with a 3-dB fractional bandwidth of 109.3% (1.53 GHz to 5.22 GHz), high out-of-band attenuation greater than 25 dB, and wide upper stopband up to 14 GHz is proposed. The design consists of a dual-composite right/left handed resonator, embedded open-circuited stub, and a pair of quarter-wavelength short-circuited stubs. These elements are coupled in the near distance to form a miniature filter with a compact occupied area of 0.21 λg×0.19 λg (≈ 0.013 cm2). The optimized filter has multitransmission poles in the passband, substantially improving the return loss and insertion loss characteristics. The behavior of the passband and stopband is verified against the results of a lumped element model and matrix analysis with a full-wave moment-based analysis and actual measurements. The results of this verification and a comparison with the performance of filters in other references indicate that the proposed filter is very efficient and applicable to compact microwave systems.

Parent Materials Effect on the Mechanical Property of the Friction Welded Spindle Valve Parts for Marine Engines (선박 엔진용 밸브 스핀들 모재에 따른 마찰 용접 후 기계적 특성 변화)

  • J. W. Shin;J. Y. Park;J. G. Kim
    • Transactions of Materials Processing
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    • v.32 no.3
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    • pp.107-113
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    • 2023
  • The importance of dual-fuel engines has increased for reducing CO2 emissions. However, the low operating temperature of this engine may induce low-temperature corrosion at combustion parts, which reduces the engine service life. To overcome this problem, NiCr38Al4 alloy was developed for valve spindle, but the cost of this alloy is expensive due to its high Cr content. For reducing the manufacturing cost of valve spindle, in the present work, NiCr38Al4 alloy was welded with Nimonic80A alloy by conducting friction welding. The tensile test results show that the strength of friction-welded specimens follows the properties of the lower-strength parent materials, without severe cracks at the interface. The large shear strain and frictional heat from friction welding not only reduce grain size but also induce solute element diffusion at the interfacial region. Because of the low Cr diffusivity compared with Ti, Cr carbides were not observed in the Nimonic80A matrix, while Ti carbides were distributed in both the Nimonic80A and SNCrW matrices.

Nondestructive Evaluation and Microfailure Mechanisms of Single Fibers/Brittle Cement Matrix Composites using Electro-Micromechanical Technique and Acoustic Emission (Electro-Micromechanical 시험법과 Acoustic Emission을 이용한 단섬유/시멘트 복합재료의 미세파괴 메커니즘과 비파괴적 평가)

  • 박종만;이상일;김진원;윤동진
    • Composites Research
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    • v.14 no.3
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    • pp.18-31
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    • 2001
  • Interfacial and microfailure properties of the modified steel, carbon and glass fibers/cement composites were investigated using electro-pullout test under tensile and compressive tests with acoustic emission (AE). The hand-sanded steel composite exhibited higher interfacial shear strength (IFSS) than the untreated and even neoalkoxy zirconate (Zr) treated steel fiber composites. This might be due to the enhanced mechanical interlocking, compared to possible hydrogen or covalent bonds. During curing process, the contact resistivity decreased rapidly at the initial stage and then showed a level-off. Comparing to the untreated case, the contact resistivity of either Zr-treated or hand-sanded steel fiber composites increased to the infinity at latter stage. The number of AE signals of hand-sanded steel fiber composite was much more than those of the untreated and Zr-treated cases due to many interlayer failure signals. AE waveforms for pullout and frictional signals of the hand-sanded composite are larger than those of the untreated case. For dual matrix composite (DMC), AE energy and waveform under compressive loading were much higher and larger than those under tensile loading, due to brittle but well-enduring ceramic nature against compressive stress. Vertical multicrack exhibits fur glass fiber composite under tensile test, whereas buckling failure appeared under compressive loading. Electro-micromechanical technique with AE can be used as an efficient nondestructive (NDT) method to evaluate the interfacial and microfailure mechanisms for conductive fibers/brittle and nontransparent cement composites.

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Art and Collectivity (미술과 집단성)

  • Kwok, Kian-Chow
    • The Journal of Art Theory & Practice
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    • no.4
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    • pp.181-202
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    • 2006
  • "When it comes to art, nationalism is a goodticket to ride with", says the title of a report in the Indian Express (Mumbai, 29 Oct 2000). The newspaper report goes on to say that since Indian art was kept "ethnic" by colonialism, national liberation meant opening up to the world on India's own terms. Advocacy, at the tail end of the 20th century, would contrast dramatically with the call by Rabindranath Tagore, the founder of the academy at Santiniketan in 1901, to guard against the fetish of nationalism. "The colourless vagueness of cosmopolitanism," Tagore pronounced, "nor thefierce self-idolatry of nation-worship, is the goal of human history" (Nationalism, 1917). This contrast is significant on two counts. First is the positive aspect of "nation" as a frame in art production or circulation, at the current point of globalization when massive expansion of cultural consumers may be realized through prevailing communication networks and technology. The organization of the information market, most vividly demonstrated through the recent FIFA World Cup when one out of every five living human beings on earth watched the finals, is predicated on nations as categories. An extension of the Indian Express argument would be that tagging of artworks along the category of nation would help ensure greatest reception, and would in turn open up the reified category of "art," so as to consider new impetus from aesthetic traditions from all parts of the world many of which hereto fore regarded as "ethnic," so as to liberate art from any hegemony of "international standards." Secondly, the critique of nationalism points to a transnational civic sphere, be it Tagore's notion of people-not-nation, or the much mo re recent "transnational constellation" of Jurgen Habermas (2001), a vision for the European Union w here civil sphere beyond confines of nation opens up new possibilities, and may serve as a model for a liberated sphere on global scale. There are other levels of collectivity which art may address, for instance the Indonesian example of local communities headed by Ketua Rukun Tetangga, the neighbourhood headmen, in which community matters of culture and the arts are organically woven into the communal fabric. Art and collectivity at the national-transnational level yield a contrasting situation of, on the idealized end, the dual inputs of local culture and tradition through "nation" as necessary frame, and the concurrent development of a transnational, culturally and aesthetically vibrant civic sphere that will ensure a cosmopolitanism that is not a "colourless vagueness." In art historical studies, this is seen, for instance, in the recent discussion on "cosmopolitan modernisms." Conversely, we may see a dual tyranny of a nationalism that is a closure (sometimes stated as "ethno-nationalism" which is disputable), and an internationalism that is evolved through restrictive understanding of historical development within privileged expressions. In art historical terms, where there is a lack of investigation into the reality of multiple modernisms, the possibility of a democratic cosmopolitanism in art is severely curtailed. The advocacy of a liberal cosmopolitanism without a democratic foundation returns art to dominance of historical privileged category. A local community with lack of transnational inputs may sometimes place emphasis on neo-traditionalism which is also a double edged sword, as re kindling with traditions is both liberating and restrictive, which in turn interplays with the push and pull of the collective matrix.

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A STUDY ON THE BONE MINERAL DENSITY OF ILIAC AND TIBIAL BONE USING DUAL ENERGY X-RAY ABSORPTIOMETRY (이중에너지 방사선 흡수계측법을 이용한 성인 남녀의 장골 및 경골의 골밀도에 관한 연구)

  • Cho, Yong-Seok;Kim, Kyoung-Won;Lee, Keong-Ho;Park, Hyun-Jin;Seo, Sang-Su;Oh, Sang-Youp
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.22 no.3
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    • pp.265-273
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    • 2000
  • Purpose : The aim of this study was to evaluate the bone mineral density of iliac and tibial bone which are frequently selected as autogenic bone graft donor sites, and to evaluate the efficiency of this method as a guideline for the selection of bone graft donor site. Materials and Methods : In this study 61 male and 70 female volunteers at Chungbuk National University Hospital were involved between Jan. 1998 to Sept. 1999. We measured bone mineral density of the iliac and the tibial bone using dual energy X-ray absorptiometry. We evaluated the data using the SAS system for Windows and bone mineral density of the lumbar was used for control. Results : Age showed the highest correlation in correlation matrix between physical and bone variables. Height and weight showed lower correlation of linear increment. In man, the change of bone density according to age demonstrated linear decrease irrespective of the lumbar, ilium, and tibia. In woman, the change of bone density according to age showed cubic form, which increased in the third and forth decade. So it had a peak bone mass on about 35 year-old, thereafter, the change of bone density slowly decreased until 50 year-old, but it rapidly decreased after 50 year-old and it slowly decreased again after 65 year-old. Both in all subjects and subject with osteoporosis, the change of bone mineral density according to age showed statistically significant decrease in lumbar and tibia, but ilium was irrespective. Conclusion : In patients of aged or with osteoporosis, ilium demonstrated less tendency of decrease in bone mineral density than tibia. So this preliminary study suggested that ilium seemed better donor site for autogenic bone graft than tibia.

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A Study on Service Quality Information in Service Industries -Focused on Kano Model and PCSI Index- (산업별 서비스품질정보 측정에 관한 연구 -Kano모형과 PCSI지수의 활용을 중심으로-)

  • Kim, Hee-Kyung;Lee, Chang-Won
    • Management & Information Systems Review
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    • v.35 no.3
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    • pp.249-272
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    • 2016
  • This study based on dual aspects of service quality aims at classifying service quality attributes by Kano model and also providing the necessity to decide which service quality would be carried out preferentially in the service industries(hotel service, repair service, education service, medical service). The first purpose of this study, therefore, is assorting the service quality by the Kano model about four service industries based on Schmenner's service process matrix. Secondly, this has an intention of drawing preferred considerations and putting forward measures to increase the customer satisfaction by Timko and PCSI Index. The result of this study is as follows. First of all, it was found that tangible attributes classified the attractive quality and Timko's score also was very high in four service industry. That is to say that tangible attributes in service industries could be interpreted into having very high importance at standards on service quality estimation of customer. Second, all but repair service of the service industries suggested empathy dimension to have flexibility solving and understanding the customer's problem could be improve the customer satisfaction. Finally, the common result between them was empathy dimension classified attractive quality in all industries. That is because present satisfaction was not reached customer expectation so there would be a improvement of empathy dimension preferentially.

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Implant Breast Reconstruction Using Porcine Dermal Matrix ($Permacol^{(R)}$): A Comparative Study with Acellular Cadaveric Dermis ($AlloDerm^{(R)}$) (돼지진피조직(Porcine Dermal Matrix, $Permacol^{(R)}$)을 이용한 보형물 유방재건술: 무세포성 사체 진피 (Acellular Cadaveric Dermis, $AlloDerm^{(R)}$)와 비교 연구)

  • Jeong, Bo-Rham;Roh, Tai-Suk;Kim, Young-Seok;Hong, Jong-Won;Rah, Dong-Kyun
    • Archives of Plastic Surgery
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    • v.38 no.5
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    • pp.559-566
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    • 2011
  • Purpose: The use of tissue expander/implant in breast reconstruction using tissue expander-implant is one of the most common surgical procedures. The use of AlloDerm as a sling to reestablish the lower pole of the pectoralis major muscle results a decrease in morbidity compared with more invasive procedures. However the use of AlloDerm is more expensive than other options. We decided to compare AlloDerm with Permacol, which has been safely used in human body reconstruction and is less costly than AlloDerm. Methods: After mastectomy, the inferolateral origin of the pectoralis major muscle was elevated. Either AlloDerm or Permacol was sutured to the chest wall at the level of the previously marked inframammary fold. The lower border of the pectoralis major muscle and the upper portion of the crescent-shaped piece of either AlloDerm or Permacol was sutured together using a tension free technique, and a tissue expander was subsequently inserted into the subpectoral-subAlloDerm (or Permacol) dual pocket. Results: AlloDerm was used in twenty-one patients (28 breasts) and Permacol was used in six patients (11 breasts) for tissue expander-implant breast reconstruction. During the mean follow-up period of 17 months (8~25 months). Two infections (7%) occurred in AlloDerm cases and four infections (36%) occurred in Permacol cases. Conclusion: This study is the first comparison of tissue expander/implant breast reconstruction using AlloDerm and Permacol. The use of Permacol resulted in more postoperative infection compared with the use of AlloDerm. This report is still limited with the small number of cases studied.