358 research outputs found
Depth-first and breadth-first search based multilevel SGA algorithms for near optimal symbol detection in MIMO systems
Get PDFThe multilevel structure of the N-QAM modulation constellations is exploited to significantly reduce the complexity of the sequential Gaussian approximation (SGA) algorithm for near optimal symbol detection in spatial multiplexing multiple- input multiple-output (MIMO) system. We propose two multilevel SGA algorithms (MSGA) which are based on depth- first search (DFS) and breadth-first search (BFS) respectively. Additionally, an important methodological contribution to this multilevel technique is proposed where the mismatch between the pseudo symbols and the true symbols is taken into consideration for the computation of posterior probabilities of symbol combinations. We justify this from a theoretical perspective as well as with numerical results. Simulation results show that the performance of the two proposed multilevel algorithms can approach that of the optimal a posteriori probability (APP) detector while its total computation cost is at most 81% and 48% of that of the original SGA algorithm for 16QAM and 64QAM modulation MIMO systems with 4 transmit/receive antennas respectively.The multilevel structure of the N-QAM modulation constellations is exploited to significantly reduce the complexity of the sequential Gaussian approximation (SGA) algorithm for near optimal symbol detection in spatial multiplexing multiple- input multiple-output (MIMO) system. We propose two multilevel SGA algorithms (MSGA) which are based on depth- first search (DFS) and breadth-first search (BFS) respectively. Additionally, an important methodological contribution to this multilevel technique is proposed where the mismatch between the pseudo symbols and the true symbols is taken into consideration for the computation of posterior probabilities of symbol combinations. We justify this from a theoretical perspective as well as with numerical results. Simulation results show that the performance of the two proposed multilevel algorithms can approach that of the optimal a posteriori probability (APP) detector while its total computation cost is at most 81% and 48% of that of the original SGA algorithm for 16QAM and 64QAM modulation MIMO systems with 4 transmit/receive antennas respectivel
Development of polynorbornenes and polypeptides as versatile functional biomaterials
Get PDFPolymer chemistry is an essential connection between organic chemistry, chemical biology and materials science. This living world has presented us many examples of the usages of polymers, such as delivery vehicle, recognition unit, support materials, information storage,5 and so on. Scientists have been trying to create synthetic polymers that can mimic such functionalities and bring widespread applications in different fields. For all synthetic polymers, their properties and potential applications are all based on their chemical nature. This is especially true for synthetic polymeric materials for bio-related applications, because of the delicate and complicated working environments and mechanisms of such biomaterials. Consequently, more facile and delicate controls over the polymers’ chemical nature are in great demand, and bottom-up strategy for the synthesis of smart polymers have been more common in the recent decades.
In this thesis paper, multiple bottom-up syntheses of useful polymeric materials are recorded. In the first part of the thesis, a new approach to prepare functional organic nanoparticles (ONPs) from linear polymers is described. The nanoparticles were obtained by consecutive ring-opening metathesis polymerization and ring-closing metathesis. This flexible and mild synthesis allowed preparation of organic- and aqueous-soluble particles with controllable size and narrow molecular weight distributions. The use of functional monomer(s) and/or chain-transfer agents had led to controllable synthesis of nanoparticles containing single, dual, or multiple reactive functional groups. Such non-toxic ONPs with many controllable parameters could be used to study the effect of surface functional groups on the cellular uptake of corresponding nanoparticles. In addition, dye-functionalized ONPs could serve as water-soluble fluorophores with highly enhanced photostability. Moreover, other functional materials such as DNAs could be conjugated onto the ONPs, bringing in new hybrid materials with applications. The ONPs and ONP-DNA conjugates could also serve as templates for the synthesis of metal nanoparticles, providing a direct and facile synthetic route for functional metal nanoparticles.
In the second part of this paper, major focus is set on a polymeric approach to enhance the efficacy of toxic r(CUG)n-binding compounds for potential Myotonic Dystrophy Type I (DM1) treatment. Also using a bottom-up living polymerization strategy, cell-penetrating polymers bearing active r(CUG)n binding ligands are prepared. The synthetic polypeptide binder was shown to have excellent performance in both molecular and cell studies, giving much enhanced binding to the toxic RNA. The ligand-polypeptide conjugates could successfully disperse ribonuclear foci caused by r(CUG)n-MBNL1 complex, and could fully reverse the mis-splicing of Insulin receptor (IR) mRNAs in the model cells. In addition, potentially due to the polymer-mediated catalytic degradation, r(CUG)n level in the model cells could be greatly reduce by low concentration treatment of the ligand-bearing polymeric material.Submission published under a 24 month embargo labeled 'U of I only', the embargo will last until 2017-08-01The student, Yugang Bai, accepted the attached license on 2015-07-08 at 09:49.The student, Yugang Bai, submitted this Dissertation for approval on 2015-07-08 at 10:41.This Dissertation was approved for publication on 2015-07-09 at 16:04.DSpace SAF Submission Ingestion Package generated from Vireo submission #8366 on 2015-09-29 at 14:59:11Made available in DSpace on 2015-09-29T20:49:45Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-07-09Embargo set by: Seth Robbins for item 89446
Lift date: 2017-09-29T20:50:34Z
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Correction: Li, Y.; He, Y. Unraveling Korea’s Energy Challenge: The Consequences of Carbon Dioxide Emissions and Energy Use on Economic Sustainability. Sustainability 2024, 16, 2074
No full textThe original reference 162 has been retracted and its contents are no longer of reference value [...
Effects of He irradiation on Ti3AlC2: Damage evolution and behavior of He bubbles
No full textIn present investigation, Ti3AlC2 ceramic was irradiated at room temperature using 50 keV He ions with
doses ranging from 8 1016 cm 2 to 1 1018 cm 2 and the corresponding peak values of dpa varying
from 4 to 52. The damage evolution of nanolaminated crystalline structure as well as the formation
and the growth of He bubbles induced by He irradiation were investigated by grazing incidence X-ray diffraction
(GIXRD), atomic force microscope (AFM) and transmission electron microscopy (TEM). GIXRD
analysis showed serious structural disorder but no obvious amorphization even at the highest dose,
which was consistent with the selected area electron diffraction (SAED) results. AFM results demonstrated
that serious blistering and exfoliation appeared on the surfaces at high doses. TEM observations
revealed the formation of spherical He bubbles, string-like bubbles and ‘‘faulting zones’’ at various doses
respectively
Enhanced structural stability of nanoporous zirconia under irradiation of He
No full textThis work reports a greatly enhanced tolerance for He irradiation-induced swelling in nanocrystalline zirconia film with interconnected nanoporous structure (hereinafter referred as to NC-C). Compared to bulk yttria-stabilized zirconia (YSZ) and another nanocrystalline zirconia film only with discrete nano voids (hereinafter referred as to NC-V), the NC-C film reveals good tolerance for irradiation of high-fluence He. No appreciable surface blistering can be found even at the highest fluence of 6 x 10(17) cm(-2) in NCC film. From TEM analysis of as-irradiated samples, the enhanced tolerance for volume swelling in NCC film is attributed to the enhanced diffusion mechanism of deposited He via widely distributed nano channels. Furthermore, the growth of grain size is quite small for both nanocrystalline zirconia films after irradiation, which is ascribed to the decreasing of area of grain boundary due to loose structure and low energy of primary knock-on atoms for He ions. (C) 2012 Elsevier B.V. All rights reserved.Materials Science, MultidisciplinaryNuclear Science & TechnologyMining & Mineral ProcessingSCI(E)EI5ARTICLE1-3225-23242
Ab initio study of irradiation tolerance for different M(n+1)AX(n) phases: Ti3SiC2 and Ti3AlC2
No full textLayered ternary M(n+1)AX(n) (MAX) materials are recently proposed to be promising candidates for future fission and fusion programmes because of their unique properties inherited from both ceramics and metals. However, different M(n+1)AX(n) materials demonstrate different behaviors when exposed to energetic neutron or ion irradiations. Based on first-principles calculations, we have investigated the irradiation tolerance of two typical M(n+1)AX(n) materials: Ti3SiC2 and Ti3AlC2 from two aspects. First, we make a detailed analysis on the interatomic bonding characters, which are believed to be responsible for the resistance to radiation-induced amorphization. Second, the formation energies of various intrinsic and antisite defects in these two compounds are calculated in order to elucidate their amorphization mechanism. Our results show that the absence of orbitals overlap of Al-C in Ti3AlC2 renders it more resistant to amorphization compared to Ti3SiC2. In addition, the antisite defects Al-Ti(1) and Al-Ti(2) in Ti3AlC2 have much lower formation energies compared to Si-Ti(1) and Si-Ti(2) in Ti3SiC2, which implies that the replacement of Ti with Al is easier than Si, thus providing an alternative way to accommodate the defects resulted from irradiation damage cascades. These results indicate that Ti3AlC2 is more irradiation tolerant than Ti3SiC2, in accordance with experimental observations. Our results have profound implications for the choice of appropriate MAX phase with best performance to be used in next reaction reactors. (C) 2014 AIP Publishing LLC
Damage evolution of yttria-stabilized zirconia induced by He irradiation
No full textThe study presents an investigation of damage evolution of yttria-stabilized zirconia (YSZ) induced by irradiation of 100 key He ions at room temperature as a function of fluence. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic force microscopy (AFM) were used in order to study the nature and evolution of structural damage at different levels. Our study shows that various kinds of defects are formed with the increasing fluence. Firstly, at low fluences, from 1 x 10(16) to 4 x 10(16) cm(-2), of which maximum values of displacement per atom (dpa) range from 0.29 to 1.17, an elastic strain which is attributed to the accumulation of irradiation-induced discrete point defects, is presented. Secondly, in the intermediate fluences ranging from 8 x 10(16) to 1 x 10(17) cm(-2) with corresponding dpa varying from 2.33 to 2.91, a large drop of elastic strain occurs accompanied by presence of an intensive damage region, which is comprised by large and interacted defect clusters. Thirdly, at the two high fluences of 2 x 10(17) and 4 x 10(17) cm(-2). of which dpa are 5.83 and 11.65 respectively, a great amount of ribbon-like He bubbles with granular structure and cracks are presented at the depth of maximum concentration of deposited He atoms. The structural damage evolution and the mechanism of formation of He bubbles are discussed. (C) 2011 Elsevier B.V. All rights reserved.Materials Science, MultidisciplinaryNuclear Science & TechnologyMining & Mineral ProcessingSCI(E)EI11ARTICLE1-3430-43642
Effects of thermal annealing on the evolution of He bubbles in zirconia
No full textSingle crystals of yttria-stabilized zirconia were implanted with 100 keV He ions at two fluences of 9 x 1016 and 3 x 10(12) cm(-2) (5 and 17 He at.%). In order to investigate the effect of thermal annealing on the evolution of both zirconia lattice and implanted He, the samples were annealed at several temperatures ranging from 500 degrees C to 1400 degrees C. Three complementary analysis techniques, RBS/C, AFM and TEM were used to study structural damage and surface morphology of the crystal before and after implantation. Results show different He evolution phenomena under the two implantation fluences. It is inferred that, at the lower fluence, the migration and agglomeration of He ions lead to bubble formation after annealing. These bubbles jack up sample surface causing the deformation of surface region and the damage level of surface region increase accordingly. As the temperature continues to increase, He gradually releases and the damage recovers. However, at the higher fluence, the He concentration is sufficient to induce bubble precipitation without annealing. He release and damage recovering is less efficient upon annealing. (C) 2014 Elsevier B.V. All rights reserved.Instruments & InstrumentationNuclear Science & TechnologyPhysics, Atomic, Molecular & ChemicalPhysics, NuclearSCI(E)[email protected]
A Comparative Study on the Current Account in China under Pegged Exchange Rate Regime and Floating Exchange Rate Regime
Get PDFThe purpose of this paper is to explore the behaviors of current account under pegged exchange rate regime and floating exchange rate regime. The quarterly data from 1994 to 2016 is applied to establish a vector auto regression model to analyze the operating mechanism among current account, real exchange rate, real GDP and interest rate. The empirical analysis results show that the terms of trade and real exchange rate have a little effect on current account under the pegged exchange rate regime. However, the results also show that the terms of trade and real exchange rate have relative greater effect on current account under the floating exchange rate regime. Even though its behavior is bigger than that of pegged exchange rate regime, it is still not very significant. Therefore, this paper provides a new suggestion that always imputing the current account deficit to impact of exchange rate regime is unreliable
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