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- 저자 : Popov, I. (검색결과 110 건)
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Popov, Alexey A.,Schiemenz, Sandra,Avdoshenko, Stanislav M.,Yang, Shangfeng,Cuniberti, Gianaurelio,Dunsch, Lothar American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.31
<P>While the role of asymmetric nitride clusters on the cage size and symmetry in fullerene-based structures is already well-known, the role of the asymmetric arrangement of metals in nitride clusters on the nitrogen is studied in detail in this work. It is discovered that asymmetric mixed-metal nitride clusters give sufficiently narrow <SUP>14</SUP>N NMR signals to make NMR the method of choice to characterize the endohedral cluster from the inside. In the series of mixed-metal nitride clusterfullerenes Lu<SUB><I>x</I></SUB>Sc<SUB>3–<I>x</I></SUB>N@C<SUB>80</SUB> and Lu<SUB><I>x</I></SUB>Y<SUB>3–<I>x</I></SUB>N@C<SUB>80</SUB> (<I>x</I> = 0–3) the δ(<SUP>14</SUP>N) values are found to be linear functions of <I>x</I> showing that <SUP>14</SUP>N chemical shifts are additive values with specific increment for each kind of metal atoms. Density functional theory calculations are performed to interpret the experimentally measured spectra. To reveal the main factors affecting <SUP>14</SUP>N chemical shifts in nitride clusterfullerenes, shielding tensor components are analyzed in terms of Ramsey theory both in localized and canonical molecular orbitals. <SUP>14</SUP>N chemical shifts in M<SUB>3</SUB>N@C<SUB>80</SUB> and related systems are shown to be determined solely by nitrogen-localized orbitals and in particular by the p<SUB><I>x,y,z</I></SUB> atomic orbitals of nitrogen. As a result, the peculiarities of the nitrogen shielding in nitride clusterfullerenes can be interpreted by the simple analysis of the nitrogen-projected density of states and its variation in different chemical environments.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-31/jp204290f/production/images/medium/jp-2011-04290f_0004.gif'></P>
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Experimental Investigation of Impact-Echo Method for Concrete Slab Thickness Measurement
Popovics John S.,Cetrangolo Gonzalo P.,Jackson Nicole D. The Korean Society for Nondestructive Testing 2006 한국비파괴검사학회지 Vol.26 No.6
Accurate estimates of in place thickness of early age (3 to 28 days after casting) concrete pavements are needed, where a thickness accuracy of ${\pm}6mm$ is desired. The impact-echo method is a standardized non-destructive technique that has been applied for this task. However, the ability of impact-echo to achieve this precision goal is affected by Vp (measured) and ${\beta}$ (assumed) values that are applied in the computation. A deeper understanding of the effects of these parameters on the accuracy of impact-echo should allow the technique to be improved to meet the desired accuracy goal. In this paper, the results of experimental tests carried out on a range of concrete slabs are reported. Impact-echo thickness estimation errors caused by material property gradients and sensor type are identified. Correction factors to the standard analysis method are proposed to correct the identified errors and to increase the accuracy of the standard method. Results show that improved accuracy can be obtained in the field by applying these recommendations with the standard impact-echo method.
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Popov, I.K.,Kwon, T.,Crossman, D.K.,Crowley, M.R.,Wallingford, J.B.,Chang, C. Academic Press 2017 Developmental Biology Vol.426 No.2
<P>During early vertebrate embryogenesis, cell fate specification is often coupled with cell acquisition of specific adhesive, polar and/or motile behaviors. In Xenopus gastrulae, tissues fated to form different axial structures display distinct motility. The cells in the early organizer move collectively and directionally toward the animal pole and contribute to anterior mesendoderm, whereas the dorsal and the ventral-posterior trunlc tissues surrounding the blastopore of mid-gastrula embryos undergo convergent extension and convergent thickening movements, respectively. While factors regulating cell lineage specification have been described in some detail, the molecular machinery that controls cell motility is not understood in depth. To gain insight into the gene battery that regulates both cell fates and motility in particular embryonic tissues, we performed RNA sequencing (RNA-seq) to investigate differentially expressed genes in the early organizer, the dorsal and the ventral marginal zone of Xenopus gastrulae. We uncovered many known signaling and transcription factors that have been reported to play roles in embryonic patterning during gastrulation. We also identified many uncharacterized genes as well as genes that encoded extracellular matrix (ECM) proteins or potential regulators of actin cytoskeleton. Co expression of a selected subset of the differentially expressed genes with activin in animal caps revealed that they had distinct ability to block activin-induced animal cap elongation. Most of these factors did not interfere with mesodermal induction by activin, but an ECM protein, EFEMP2, inhibited activin signaling and acted downstream of the activated type I receptor. By focusing on a secreted protein kinase PKDCC1, we showed with overexpression and knockdown experiments that PKDCC1 regulated gastrulation movements as well as anterior neural patterning during early Xenopus development. Overall, our studies identify many differentially expressed signaling and cytoskeleton regulators in different embryonic regions of Xenopus gastrulae and imply their functions in regulating cell fates and/or behaviors during gastrulation. (C) 2016 Elsevier Inc. All rights reserved.</P>
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On the Spectrum Discreteness for the Magnetic Schrödinger Operator on Quantum Graphs
Popov, Igor Y.,Belolipetskaia, Anna G. Department of Mathematics 2021 Kyungpook mathematical journal Vol.61 No.2
The aim of this work is to study the discreteness of the spectrum of the Schrödinger operator on infinite quantum graphs in a magnetic field. The problem was solved on a set of quantum graphs of a special kind.
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Portable Exoskeleton Glove With Soft Structure for Hand Assistance in Activities of Daily Living
Popov, Dmitry,Gaponov, Igor,Ryu, Jee-Hwan IEEE 2017 IEEE/ASME transactions on mechatronics Vol.22 No.2
<P>This paper presents a new portable exoskeleton glove developed for assistance in activities of daily living ( ADL). The proposed glove is soft, adjustable, allows unconstrained motion of the wrist, and leaves the palm free for object grasping and manipulation. In the proposed design, both flexion and extension motions of the thumb and three fingers ( excluding the little finger) are supported by respective bidirectional actuators. The kinematics of the device were derived and are presented along with an experimental evaluation. The developed glove system is compact and light, with the weights of the wearable part and the whole system being 250 and 340 g, respectively. The maximum pinch force provided by the device was experimentally measured to be 16 N, which gives the proposed device one of the highest power-to-weight ratio among existing portable devices for hand ADL assistance. The usability of the developed device was verified in a series of indoor and outdoor tests. The glove allowed test subjects to hold and manipulate versatile objects with diameters up to 90 mm and weighing 300 g. When powered by a conventional 3000-mAh battery, the glove could operate continuously performing grasping task for 4 h.</P>
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Which Economic Model is more Competitive? The West and the South after the Covid-19 Pandemic
Vladimir Popov 서울대학교 경제연구소 2020 Seoul journal of economics Vol.33 No.4
China and other East Asian countries were able to deal with the coronavirus pandemic much better than most Western countries. Both the number of infections and the mortality rate were lower than in Western countries by two orders of magnitude. Besides, economic recession associated with the pandemic is likely to be much deeper in the West than in the South. These developments give new arguments to the views that East Asian economic and social model is more viable than the Western model. This paper argues that East Asian model is superior to the other models in the Global South at least in the catch up development and possibly even in the innovations beyond the technological frontier. The crucial features of the East Asian economic model are relatively low income and wealth inequalities, strong state institutional capacity (as measured by the murder rate and the share of shadow economy), high patriotism and trust in the government institutions. In short, the East Asian model is based on solidarity and priority of collective interests more than on guarantees of individual rights and competition.
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Dmitry Popov,이광현,Igor Gaponov,유지환 한국로봇학회 2013 로봇학회 논문지 Vol.8 No.3
This paper presents a new concept of a 1-DOF elbow exoskeleton driven by a twisted strings-based actuator. A novel joint actuation mechanism is proposed and its kinematic model is presented along with its experimental evaluation, and guidelines on how to choose the strings suitable for such an exoskeleton are given. We also proposed and experimentally verified a human intention detection method which takes advantage of intrinsic compliance of the mechanism. The study showed that the developed twisted strings-driven elbow exoskeleton is light, compact and have a high payload-to-weight ratio, which suggests that the device can be effectively used in a variety of haptics, teleoperation, and rehabilitation applications.
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