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M. I. Pech-Canul,M. Rodríguez-Reyes3,M. A. Pech-Canul,J. C. Rendón-Angeles 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.6
In this work, SiC_P and SiC_P/SiO_2 porous preforms were infiltrated without assistance in Ar→N_2 atmosphere with the alloy Al-10.3 Mg-12.04 Si (wt.%) at 1050 and 1100 °C, for 20, 40 and 60 min. It was found that a decrease in residual porosity and an increase in elastic modulus by about 22 % with respect to composites produced without SiO_2 additions to the preforms are associated with the formation of magnesium aluminate spinel (MgAl_2O_4). A concurrent increase of the matrix hardness is ascribed to a strengthening mechanism by MgAl_2O_4 formation, similar to the strengthening observed with Mg_2Si in aluminum alloys. Therefore, the spinel can be considered as a co-reinforcement of SiC_p in the aluminum matrix composites. Reactions for spinel formation and possible mechanisms for hardness enhancement are outlined.
Substrate Integrated Waveguide Quasi-Elliptic Filter with Arbitrary Termination Impedances
PECH PHANAM,KIMPHIRUN,CHAUDHARYGIRDHARI,정용채 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.4
This paper presents a quasi-elliptic filter (QEF) with arbitrary termination impedances (ATI). The proposed QEF is designed by adding cross-coupling between the first and last resonators of an ATI bandpass filter (BPF) with the Chebyshev response. The proposed QEFs with ATI can be designed in even-order resonators and the location of the pair transmission zeros (TZs) is controllable. To prove the validity of the proposed design, the fourth-order QEFs with ATI were implemented on a single-layer substrate-integrated waveguide (SIW) cavity at a center frequency ( ) of 10 GHz with the pair TZs at 10 ± 1.4 GHz. These SIW QEFs with ATI improve frequency selectivity and effectively suppress the out-of-band signal with high power handling. The measured maximum insertion loss (|S21|) and minimum return loss (|S11|) of the SIW QEF with unequal real-to-real ATI are 0.93 dB and 17.4 dB, respectively, in the passband. Simi- larly, the maximum |S21| and minimum |S11| of the SIW QEF with complex-to-real ATI are 1.2 dB and 18 dB, respectively.
Carlos Omar Trejo-Pech,Sharon Thach 한국마케팅과학회 2021 마케팅과학연구 Vol.31 No.1
This is a review of four articles published in the JGSMS 2019 special issue on Marketing Management in International Contexts. All papers published in this special issue were peer-reviewed, with oversight from the authors of this document in the role of Guest Editors. Three articles examine aspects of digital communication influences on behavior and attitudes, while one studies consumer preferences in the context of differing cultural and technological backgrounds. Generational cohorts and cultural clusters are examined through these studies. Overall, the articles in this special issue contribute to our knowledge of how younger persons use and are shaped by the digital world they have been born into, but also to the persistence of underlying cultures.
A Proactive Nonlinear Disturbance Compensator for the Quarter Car
Johannes N. Strohm,Dominik Pech,Boris Lohmann 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.8
A new Proactive Nonlinear Disturbance Compensator (PNDC) for vibration damping in a quarter car is presented. A Flatness Based Disturbance Compensator (FBDC) for a nonlinear quarter car model is derived that decouples the chassis acceleration completely from the known road disturbance. This leads to a high level of driving comfort but to a loss in driving safety. Therefore a Proactive Linear Disturbance Compensator (PLDC) is added. This controller uses knowledge of the future road disturbance to reach a compromise between driving safety and driving comfort. The sensitivity of the nonlinear, proactive disturbance compensator to varying parameters or measurement noise is examined in simulations, and the tuning of the design parameters is shown. Furthermore, results from experiments on the institute’s quarter car test stand are discussed. These have shown that the performance of the proposed method exceeds a linear quadratic regulator in simulations and experiments and that the driving comfort can be increased by more than fifty percent without a decrease in driving safety.
Sequencing in Customs Union Formation : Theory and Application to the Eurasian Economic Union
( Aidos Alimbekov ),( Eldar Madumarov ),( Gerald Pech ) 세종대학교 경제통합연구소 2017 Journal of Economic Integration Vol.32 No.1
In the model of optimal sequencing in economic integration, an agenda setter chooses between two bargaining protocols that correspond to two different integration paths. With multilateral negotiations, the union is formed immediately, whereas with sequential negotiations, a core union is formed before all other countries in the region integrate. The latter is preferred if formation of a core union has negative externalities on a candidate country. The agenda setter improves her bargaining position, but an efficiency loss from delayed integration is incurred. We demonstrate that the threat of delayed entry will not be carried out if an open-rule protocol is available, i.e., if the agenda setter can propose to form a core union and amend this proposal before it is adopted. Yet, if bargaining is time consuming, this result can be overturned and there may be a delay that incurs a temporary efficiency loss. Our model explains the sequential formation of the Eurasian Customs Union.
A Novel, Reactive Green Iron Sulfide (Sulfide Green Rust) Formed on Iron Oxide Nanocrystals
Jones, Christopher J.,Chattopadhyay, Soma,Gonzalez-Pech, Natalia I.,Avendano, Carolina,Hwang, Nina,Lee, Seung Soo,Cho, Minjung,Ozarowski, Andrew,Prakash, Arjun,Mayo, J. T.,Yavuz, Cafer,Colvin, Vicki. American Chemical Society 2015 Chemistry of materials Vol.27 No.3
<P>Iron oxide nanocrystals are of great scientific and technological interest. In this work, these materials are the starting point for producing a reactive nanoparticle whose surface resembles that of natural green rusts. Treatment of iron oxide nanoparticles with cysteamine leads to the reduction of iron and the formation of a brilliant green aqueous solution of nanocrystals rich in iron(II). These materials remained crystalline with magnetic and structural features of the original iron oxide. However, new low-angle X-ray diffraction peaks as well as vibrational features characteristic of cysteamine were found in the nanocrystalline product. X-ray absorption spectroscopy (XAS), X-ray photoemission (XPS) and Mössbauer spectroscopies indicated the presence of an iron(II)-rich phase with high sulfur content analogous to the iron–oxygen structures found in natural green rusts. Electron microscopy found that these structural components remained associated with the nonreduced iron oxide cores. These sulfur-rich analogs of natural green rusts are highly reactive and were able to rapidly degrade a model organic dye in water. This observation suggests possible actuation with a cysteamine treatment of inert and magnetic iron oxide particles at the point-of-use for environmental remediation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-3/cm5028942/production/images/medium/cm-2014-028942_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5028942'>ACS Electronic Supporting Info</A></P>