基于XRD和FTIR的香樟木质部提取物处理材褐腐的光谱学分析

植物源防腐剂因其环保、广谱、高效等特点越来越受到木材防腐行业的重视,从微观层面探索香樟提取物影响木材腐朽的机理是发展利用植物源防腐剂的重要基础。试验采用香樟木质部的四种溶剂提取物、ACQ及樟脑配制成防腐剂进行防腐试验,结果表明:10%浓度的香樟木质部甲醇提取物以及4%浓度的ACQ处理试件均达到I级强耐腐水平,4%樟脑、10%香樟乙酸乙酯和10%丙酮提取物处理的试件达到Ⅱ级耐腐水平。通过XRD对比发现结晶区2θ衍射强度由大到小的顺序为:10%蒸馏水提取物处理材、马尾松素样、10%丙酮提取物处理材、10%甲醇提取物处理材、10%乙酸乙酯提取物处理材,四种香樟木质部提取物的防腐效果与相对结晶度大小呈正相关。通过FTIR研究发现表征纤维素和半纤维素的特征峰值越低,则被降解的量也越大,相对应的防腐剂防腐效果越差。处理试件中表征木质素的一系列特征峰峰高与未处理材相比有所升高。香樟甲醇提取物以及ACQ处理试件的I1 510/I1 738,I1 510/I1 374,I1 510/I1 160的比值最小,证明褐腐菌对其综纤维素的降解能力最弱,防腐效果最好。     

离子注入对ZnTe:O中间带光伏材料的微观结构及光学特性的影响

II-VI和III-V族高失配合金半导体是新型高效中间带太阳电池的优选材料体系,但中间带的形成及其能带调控等关键问题仍未得到有效解决.采用氧离子注入方式,在非平衡条件下对碲化锌(Zn Te)单晶材料实现了等电子掺杂,深入研究了离子注入对Zn Te:O材料的微观结构和光学特性的影响.研究表明:注入合适浓度的氧离子(2.5×1018cm-3)将会形成晶格应变,并诱导1.80 e V(导带下0.45 e V)中间带的产生;而较高浓度(2.5×1020cm-3)的氧离子会导致Zn Te注入层表面非晶化,并增强与锌空位相关的深能级(～1.6 e V)发光.时间分辨光致发光结果显示,离子注入诱导形成的中间带主要是和氧等电子陷阱束缚的局域激子发光有关,载流子衰减寿命较长(129 ps).因此,需要降低晶格紊乱度和合金无序,实现电子局域态向扩展态的转变,从而有效调控中间带能带结构.     

En route to Background Independence: Broken split-symmetry,and how to restore it with bi-metric average actions

The most momentous requirement a quantum theory of gravity must satisfy is Background Independence, necessitating in particular an ab initio derivation of the arena all non-gravitational physics takes place in, namely spacetime. Using the background field technique, this requirement translates into the condition of an unbroken split-symmetry connecting the (quantized) metric fluctuations to the (classical) background metric. If the regularization scheme used violates split-symmetry during the quantization process it is mandatory to restore it in the end at the level of observable physics. In this paper we present a detailed investigation of split-symmetry breaking and restoration within the Effective Average Action (EAA) approach to Quantum Einstein Gravity (QEG) with a special emphasis on the Asymptotic Safety conjecture. In particular we demonstrate for the first time in a non-trivial setting that the two key requirements of Background Independence and Asymptotic Safety can be satisfied simultaneously. Carefully disentangling fluctuation and background fields, we employ a ‘bi-metric’ ansatz for the EAA and project the flow generated by its functional renormalization group equation on a truncated theory space spanned by two separate Einstein–Hilbert actions for the dynamical and the background metric, respectively. A new powerful method is used to derive the corresponding renormalization group (RG) equations for the Newton- and cosmological constant, both in the dynamical and the background sector. We classify and analyze their solutions in detail, determine their fixed point structure, and identify an attractor mechanism which turns out instrumental in the split-symmetry restoration. We show that there exists a subset of RG trajectories which are both asymptotically safe and split-symmetry restoring: In the ultraviolet they emanate from a non-Gaussian fixed point, and in the infrared they loose all symmetry violating contributions inflicted on them by the non-invariant functional RG equation. As an application, we compute the scale dependent spectral dimension which governs the fractal properties of the effective QEG spacetimes at the bi-metric level. Earlier tests of the Asymptotic Safety conjecture almost exclusively employed ‘single-metric truncations’ which are blind towards the difference between quantum and background fields. We explore in detail under which conditions they can be reliable, and we discuss how the single-metric based picture of Asymptotic Safety needs to be revised in the light of the new results. We shall conclude that the next generation of truncations for quantitatively precise predictions (of critical exponents, for instance) is bound to be of the bi-metric type.     

Synthesis of resonant cavities having continuum spectra by genetic algorithm

This paper proposes a novel method for generating continuum spectra with possible applications in WDM access networks. This new method would allow the development of a simple continuum laser structure with better performances in terms of cost and simplicity than those of present supercontinuum sources. In this aim, we will analyze the possibility to broaden the resonant modes of a Fabry–Perot cavity by operating only on the design of one of the cavity's Bragg mirrors. Firstly we considered the conditions which a Bragg grating must satisfy in order to broaden the resonant modes of a resonant cavity. Because an exact solution is not physical possible, the genetic algorithm is the best available tool for the design of such a grating. An active medium is then added inside the cavity and its behavior below threshold is simulated. The spectra thus simulated are continuum over 5–15 nm.     

Conditions and evidence for non-integrability in the Friedmann-Robertson-Walker Hamiltonian

This is an example of application of Ziglin-Morales-Ramis algebraic studies in Hamiltonian integrability, more specifically the result by Morales, Ramis and Simó on higher-order variational equations, to the well-known Friedmann-Robertson-Walker cosmological model. A previous paper by the author formalises said variational systems in such a way allowing the simple expression of notable elements of the differential Galois group needed to study integrability. Using this formalisation and an alternative method already used by other authors, we find sufficient conditions whose fulfilment for given parameters would entail very simple proofs of non-integrability – both for the complete Hamiltonian, a goal already achieved by other means by Coelho et al, and for a special open case attracting recent attention.     

Fractional cyclic integrals and Routh equations of fractional Lagrange system with combined Caputo derivatives

In this paper, we develop a fractional cyclic integral and a Routh equation for fractional Lagrange system defined in terms of fractional Caputo derivatives. The fractional Hamilton principle and the fractional Lagrange equations of the system are obtained under a combined Caputo derivative. Furthermore, the fractional cyclic integrals based on the Lagrange equations are studied and the associated Routh equations of the system are presented. Finally, two examples are given to show the applications of the results.     

Nonlinear spectral-like schemes for hybrid schemes

In spectral-like resolution-WENO hybrid schemes,if the switch function takes more grid points as discontinuity points,the WENO scheme is often turned on,and the numerical solutions may be too dissipative.Conversely,if the switch function takes less grid points as discontinuity points,the hybrid schemes usually are found to produce oscillatory solutions or just to be unstable.Even if the switch function takes less grid points as discontinuity points,the final hybrid scheme is inclined to be more stable,provided the spectral-like resolution scheme in the hybrid scheme has moderate shock-capturing capability.Following this idea,we propose nonlinear spectral-like schemes named weighted group velocity control(WGVC)schemes.These schemes show not only high-resolution for short waves but also moderate shock capturing capability.Then a new class of hybrid schemes is designed in which the WGVC scheme is used in smooth regions and the WENO scheme is used to capture discontinuities.These hybrid schemes show good resolution for small-scales structures and fine shock-capturing capabilities while the switch function takes less grid points as discontinuity points.The seven-order WGVC-WENO scheme has also been applied successfully to the direct numerical simulation of oblique shock wave-turbulent boundary layer interaction.     

有限温度张量重正化群方法及其在阻挫量子磁性研究中的应用

阻挫量子磁体中的新奇物态与效应是凝聚态物理研究的重要前沿方向,因其与高温超导、拓扑量子计算等的密切联系,近年来吸引了人们浓厚的研究兴趣。实验上,阻挫自旋液体候选材料的 新进展层出不穷,人们系统地研究了若干三角晶格、笼目晶格和六角Kitaev 阻挫磁体等材料,发 现其在一定条件下展现出自旋液体态的特征,但澄清其中的量子物态是充满挑战的量子多体问题。 作者最近的工作指出,可以从有限温度张量重正化群多体计算入手,开展热力学性质的精确计算 与分析,确定阻挫磁体的微观自旋模型,做出进一步理论预言并开展实验验证,从而建立量子磁性 系统的多体计算精确研究方案。有限温度张量重正化群方法是计算大尺寸二维阻挫量子自旋模型 有限温度性质的有力工具,在本文中作者首先介绍新近发展的系列张量重正化群方法,包括线性 和指数张量重正化群等。随后,作者讨论有限温度张量方法在三角晶格量子伊辛磁体TmMgGaO4 和六角晶格Kitaev 磁体α-RuCl3 的微观自旋模型中的具体应用：通过高精度和全面的多体计算, 揭示出其中存在演生U(1) 对称性与拓扑相变,以及高场量子自旋液体态等新颖的结论,这些理 论预言也陆续被实验所证实。通过上述实例,作者展示了有限温度张量重正化群计算方法在自旋 液体候选材料研究中的应用价值,并期待这些方法能在强关联量子物质研究中发挥重要作用。     

Local stability analysis of a low-dissipation cyclic refrigerator*

We study the local stability near the maximum figure of merit for the low-dissipation cyclic refrigerator,where the irreversible dissipation occurs not only in the thermal contacts but also the adiabatic strokes.We find that the bounds of the coefficient of performance at a maximum figure of merit or maximum cooling rate in the presence of internal dissipation are identical to those in the corresponding absence of internal dissipation.Using two different scenarios,we prove the existence of a single stable steady state for the refrigerator,and clarify the role of internal dissipation on the stability of the thermodynamic steady state,showing that the speed of system evolution to the steady state decreases due to internal dissipation.     

Crystal Structure Analysis of Betti Base 1-((2-hydroxynaphthalen-1-yl)(2-hydroxyphenyl)methyl)urea•2DMF Solvate

A novel Betti base compound, 1-((2-hydroxynaphthalen-1-yl)(2-hydroxyphenyl)methyl)urea, UBB, was synthesized and characterized by spectral, structural and thermal studies. Single crystal X-ray diffraction studies reveal that the racemic mixture of the compound, when crystallized from DMF, yields R-isomer preferentially (prismatic crystals), whereas, when crystallized from 5:1 (v/v) mixture of DMF-THF, it yields S-isomer (rectangular shaped crystals) with two molecules of DMF, included in both the cases. The crystal structure is discussed in terms of supramolecular interactions and molecular modeling. Both R and S enantiomeric DMF solvate crystals are in their chiral triclinic P1 space group.