Growth and dielectric properties of KTiOPO4 and K1 - x Rb x TiOPO4 crystals
Gurtovoĭ, V. G.; Sheleg, A. U.; Guretskiĭ, S. A.; Kalanda, N. A.
2008-07-01
Methods of growth of KTiOPO4 and K1 - x Rb x TiOPO4 crystals of high optical quality have been optimized. The dielectric properties (permittivity and conductivity) of the crystals grown have been investigated at frequencies from 102 to 106 Hz in the temperature range from 100 to 350 K, along the [001] crystallographic direction. It is established that partial substitution of K+ ions with Rb+ ions leads to a decrease in the permittivity and conductivity.
Synthesis of LaxK1-xCoO3 nanorod and their catalytic performances for CO oxidation
Institute of Scientific and Technical Information of China (English)
刘坚; 王季秋; 赵震; 徐春明; 韦岳长; 段爱军; 姜桂元
2014-01-01
A series of LaxK1-xCoO3 nanorod oxides with perovskite structure were synthesized by sol-gel method using polyvinyl al-cohol (PVA) as additive. These perovskite-type complex oxide catalysts were characterized by the techniques of X-ray diffraction (XRD), infrared (IR), Brumauer-Emmett-Teller (BET) and scanning electron microscopy (SEM). And the results showed that nano-rods of La1-xKxCoO3 perovskite-type complex oxides were fabricated by sol-gel method when the mass concentration of PVA was 4%and the calcined temperature kept at 700 ℃ for 4 h. The catalytic results of CO oxidation showed that the LaxK1-xCoO3 catalysts had high activity. LaCoO3 nanorods exposed more{110}plane than LaCoO3 nanoparticles, which was beneficial to the catalytic oxi-dation of CO. LaCoO3 nanorods had the best catalytic performance for the oxidation of CO. At 200 ºC, the CO conversion could reach 100%.
Nekrasov, I. A.; Pavlov, N. S.; Sadovskii, M. V.
2013-11-01
We present a detailed LDA' + DMFT investigation of the doping dependence of correlation effects in the novel K1 - x Fe2 - y Se2 superconductor. Calculations are performed at four different hole doping levels, starting from a hypothetical stoichiometric composition with the total number of electrons equal to 29 per unit cell through 28 and 27.2 electrons toward the case of 26.52, which corresponds to the chemical composition K0.76Fe1.72Se2 studied in recent ARPES experiments. In the general case, the increase in hole doping leads to quasiparticle bands in a wide energy window ±2 eV around the Fermi level becoming more broadened by lifetime effects, while correlation-induced compression of Fe-3 d LDA' bandwidths stays almost the same, of the order of 1.3 for all hole concentrations. However, close to the Fermi level, the situation is more complicated. In the energy interval from -1.0 eV to 0.4 eV, the bare Fe-3 d LDA' bands are compressed by significantly larger renormalization factors up to 5 with increased hole doping, while the value of Coulomb interaction remains the same. This fact manifests the increase in correlation effects with hole doping in the K1 - x Fe2 - y Se2 system. Moreover, in contrast to typical pnictides, K1 - x Fe2 - y Se2 does not have well-defined quasiparticle bands on the Fermi levels, but has a "pseudogap"-like dark region instead. We also find that with the growth of hole doping, Fe-3 d orbitals of various symmetries are affected by correlations differently in different parts of the Brillouin zone. To illustrate this, we determine the quasiparticle mass renormalization factors and energy shifts that transform the bare Fe-3 d LDA' bands of various symmetries into LDA' + DMFT quasiparticle bands. These renormalization factors effectively mimic more complicated energy-dependent self-energy effects and can be used to analyze the available ARPES data.
LDA'+DMFT investigation of electronic structure of K1 - x Fe2 - y Se2 superconductor
Nekrasov, I. A.; Pavlov, N. S.; Sadovskii, M. V.
2013-03-01
We investigate electronic structure of the new iron chalcogenide high temperature superconductor K1- x Fe2- y Se2 (hole doped case with x = 0.24, y = 0.28) in the normal phase using the novel LDA'+DMFT computational approach. We show that this iron chalcogenide is more correlated in a sense of bandwidth renormalization (energy scale compression by factor about 5 in the interval ±1.5 eV), than typical iron pnictides (compression factor about 2), though the Coulomb interaction strength is almost the same in both families. Our results for spectral densities are in general agreement with recent ARPES data on this system. It is found that all Fe-3 d( t 2 g ) bands crossing the Fermi level have equal renormalization, in contrast to some previous interpretations. Electronic states at the Fermi level are of predominantly xy symmetry. Also we show that LDA'+DMFT results are in better agreement with experimental spectral function maps, than the results of conventional LDA+DMFT. Finally we make predictions for photoemission spectra lineshape for K0.76Fe1.72Se2.
Origin of giant piezoelectric effect in lead-free K1-xNaxTa1-yNbyO3 single crystals.
Tian, Hao; Meng, Xiangda; Hu, Chengpeng; Tan, Peng; Cao, Xilong; Shi, Guang; Zhou, Zhongxiang; Zhang, Rui
2016-05-10
A series of high-quality, large-sized (maximum size of 16 × 16 × 32 mm(3)) K1-xNaxTa1-yNbyO3 (x = 0.61, 0.64, and 0.70 and corresponding y = 0.58, 0.60, and 0.63) single crystals were grown using the top-seed solution growth method. The segregation of the crystals, which allowed for precise control of the individual components of the crystals during growth, was investigated. The obtained crystals exhibited excellent properties without being annealed, including a low dielectric loss (0.006), a saturated hysteresis loop, a giant piezoelectric coefficient d33 (d33 = 416 pC/N, determined by the resonance method and d33(*) = 480 pC/N, measured using a piezo-d33 meter), and a large electromechanical coupling factor, k33 (k33 = 83.6%), which was comparable to that of lead zirconate titanate. The reason the piezoelectric coefficient d33 of K0.39Na0.61Ta0.42Nb0.58O3 was larger than those of the other two crystals grown was elucidated through first-principles calculations. The obtained results indicated that K1-xNaxTa1-yNbyO3 crystals can be used as a high-quality, lead-free piezoelectric material.
Origin of giant piezoelectric effect in lead-free K1-xNaxTa1-yNbyO3 single crystals
Tian, Hao; Meng, Xiangda; Hu, Chengpeng; Tan, Peng; Cao, Xilong; Shi, Guang; Zhou, Zhongxiang; Zhang, Rui
2016-05-01
A series of high-quality, large-sized (maximum size of 16 × 16 × 32 mm3) K1-xNaxTa1-yNbyO3 (x = 0.61, 0.64, and 0.70 and corresponding y = 0.58, 0.60, and 0.63) single crystals were grown using the top-seed solution growth method. The segregation of the crystals, which allowed for precise control of the individual components of the crystals during growth, was investigated. The obtained crystals exhibited excellent properties without being annealed, including a low dielectric loss (0.006), a saturated hysteresis loop, a giant piezoelectric coefficient d33 (d33 = 416 pC/N, determined by the resonance method and d33* = 480 pC/N, measured using a piezo-d33 meter), and a large electromechanical coupling factor, k33 (k33 = 83.6%), which was comparable to that of lead zirconate titanate. The reason the piezoelectric coefficient d33 of K0.39Na0.61Ta0.42Nb0.58O3 was larger than those of the other two crystals grown was elucidated through first-principles calculations. The obtained results indicated that K1-xNaxTa1-yNbyO3 crystals can be used as a high-quality, lead-free piezoelectric material.
Choukri, E.; Neqali, A.; Abkhar, Z.; Alimoussa, A.; Hajji, L.; Mezzane, D.; Belboukhari, A.; Amjoud, M.; Gagou, Y.; El Marssi, M.; Luk'yanchuk, I.
2016-06-01
Substitution of Pb with Li and K in the Pb2KNb5O15 phases leads to a new composition with chemical composition Pb2- x K1+ x Li x Nb5O15 which crystallizes with tetragonal tungsten bronze-type structure. Ferroelectric ceramics with different compositions were synthesized using solid-state reaction and complex dielectric permittivity measurements in these compounds were performed in a frequency and temperature range of 20 Hz-1 MHz and from 25 to 550 °C, respectively. Special attention was paid to the diffuse phase transition (DPT) that occurs close to the Curie temperature. The empirical equation proposed by Santos-Eiras for a phenomenological description of the temperature dependence of the dielectric permittivity (\\varepsilon_{{r}}^' }}) peak is used to calculate some characteristic parameters of DPT. From the results, it must be assumed that these compounds show a diffuse phase transition with non-relaxor behavior. A basic phase diagram showing the evolution of T m function of composition x is deduced from this study.
Bannikov, V. V.; Ivanovskii, A. L.
2013-09-01
Soon after the discovery of superconductivity in layered Fe-Ch systems, the intense search of related Fe-free materials has been begun. It was found that these systems such as KxNi2(S,Se)2 are cation-deficient, and the superconducting state should be sensitive to the presence of K and Ni vacancies. Herein, using the first principles FLAPW-GGA calculations, we have studied the electronic structure and Fermi surface (FS) topology for cation-deficient K1-xNi2-ySe2. We have found that the presence of potassium vacancies (for K0.8Ni2Se2) as well as the joint effect of K and Ni vacancies (for K0.8Ni1.6Se2) change essentially the topology of their FSs and the character of electronic bands. Unlike 2D-like FS for stoichiometric KNi2Se2, the FSs for cation-deficient compositions demonstrate much more complex topology of mixed 2D-3D type.
Effect of Fe doping on structural and impedance properties of PZTFN ceramics
Kumar, Arvind; Pal, Vijayeta; Mishra, S. K.
2016-05-01
An attempts have been made to synthesis the ceramics Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 abbreviated as (PFZTN) for x = 1-6 mol% and y = 5.5 mol% by a semi-wet route. In the present paper, we have investigated the effect of Fe doping on structural and electrical properties of the PFZTN ceramics. X-ray diffraction (XRD) patterns reveal that PFZTN ceramics are single phase in nature. However, for x = 0.05 and 0.06, a secondary phase appears as discernible from the XRD profiles. Rietveld analysis of the powder diffraction data shows the presence of coexistence of tetragonal (P4mm space group) and rhombohedral phases (R3c space group) occurs near the morphotropic phase boundary (MPB) at x ≥ = 0.05. The log-log plots show that the conductivity increases with increase of temperature. The ac conductivity becomes sensitive at high frequency region and shifted towards higher frequency side with increasing temperature. It is observed that the activation energy (Ea) decreases with increasing frequency. This complex perovskite structure can be used as a multilayer ceramic capacitors and electromechanical transducers.
Flux Compactifications of Projective Spaces and The S-Duality Puzzle
Bouwknegt, P; Jurco, B; Mathai, V; Sati, H
2005-01-01
We derive a formula for D3-brane charge on a compact spacetime, which includes torsion corrections to the tadpole cancellation condition. We use this to classify D-branes and RR fluxes in type II string theory on RP^3xRP^{2k+1}xS^{6-2k} with torsion H-flux and to demonstrate the conjectured T-duality to S^3xS^{2k+1}xS^{6-2k} with no flux. When k=1, H\
The structured controllability radii of higher order systems
National Research Council Canada - National Science Library
Son, Nguyen Khoa; Thuan, Do Duc
2013-01-01
In this paper we shall deal with the problem of calculation of the controllability radius of higher order dynamical systems of the form Ex.sup.(k)(t)=A.sub.k-1x.sup.(k-1)(t)+a[macron]+A.sub.1x.sup.(1)(t)+A.sub.0x(t)+Bu...
Dynamics of a compact operator
Lim, Teck-Cheong
2010-01-01
Let $T:X\\to X$ be a compact linear (or more generally affine) operator from a Banach space into itself. For each $x\\in X$, the sequence of iterates $T^nx, n=0,1,...$ and its averages $\\frac{1}{k}\\sum_{k=0}^nT^{k-1}x, n=0,1,...$ are either bounded or approach infinity.
Yoshii, Kenji; Hayashi, Naoaki; Mizumaki, Masaichiro; Takano, Mikio
2017-04-01
We have investigated the magnetocaloric effect (MCE) of Ba1-xSrxFe4+O3 (x≤0.2), a series of cubic perovskites showing a field-induced transition from helical antiferromagnetism to ferromagnetism. The maximum magnetic entropy change (-ΔSmax) at 50 kOe varies from ˜5.8 J kg-1K-1 (x=0) to ˜4.9 J kg-1K-1 (x=0.2), while the refrigerant capacity remains almost the same at ˜165 J kg-1. Interestingly, the temperature of -ΔSmax decreases from ˜116 K to ˜77 K with increasing x, providing this series of rare-earth-free oxides with potential as a magnetic refrigerant for the liquefaction of nitrogen and natural gas.
Mean-Field Calculations for the Three-Dimensional Holstein Model
Institute of Scientific and Technical Information of China (English)
罗强; 刘川
2002-01-01
The electron-phonon Holstein model is studied in three spatial dimensions. It is argued that this model can be used to account for major features of the high-To BaPb1-xBixO3 and BaxK1-xBiO3 systems. Mean-field calculations are performed via a path integral representation of the model. Charge-density-wave order parameters and transition temperatures are obtained.
Techniques in Data Compression and Maximization of Information Content
1977-01-01
The formulas given beiwr are equivalent and selec- io-n othe sne te use should bc Pmade by de-t-ermining which one is the easiest to calculate. The...B v X Xin ... "!n L on i, 1 -e matriz of n observed values. S matrix of che n Kn xwn points of the k 1., X 1 ’s. S-e - of the k + t coefficients of
年年“题”不同岁岁“法”相似——高考全国卷函数不等式恒成立求参数范围问题的解法分析
Institute of Scientific and Technical Information of China (English)
赵忠平
2012-01-01
2011年全国新课标卷第21题为:已知函数f(x)=alnx/x+1+b/x,曲线y=f(x)在点(1,f(1))处的切线方程x+2y-3=0.(1)求a,b的值;(2)如果当x＞0且x≠1时,f(x)＞lnx/x-1+k/x,求k的取值范围.对于第(2)问,高考命题组提供的标准答案为:(2)由(1)知f(x)=lnx/x+1+1/x,所以f(x)-(lnx/x-1+1/x)=1/1-x(2lnx+(k-1)(x2-1)/x.构造函数h(x):2lnx+(k-1)(x2-1)/x(x＞0),则h′(x)=(k-1)(x2-1)+2x/x2.
Moment Convergence Rates in the Law of the Logarithm for Dependent Sequences
Indian Academy of Sciences (India)
Ke-Ang Fu; Xiao-Rong Yang
2009-06-01
Let $\\{X_n;n≥ 1\\}$ be a strictly stationary sequence of negatively associated random variables with mean zero and finite variance. Set $S_n=\\sum^n_{k=1}X_k,M_n=\\max_{k≤ n}|S_k|,n≥ 1$. Suppose $^2=EX^2_1+2\\sum^∞_{k=2}EX_1X_k(0 < < ∞)$. In this paper, the exact convergence rates of a kind of weighted infinite series of $E\\{M_n-\\sqrt{n\\log n}\\}_+$ and $E\\{|S_n|-\\sqrt{n\\log n}\\}_+$ as $\\searrow 0$ and $E\\{\\sqrt{\\frac{^2 n}{8\\log n}}-M_n\\}_+$ as $\
Stability and convergence of a higher order rational difference Equation
Gazor, Hamid
2011-01-01
In this paper the asymptotic stability of equilibria and periodic points of the following higher order rational difference Equation x_{n+1} =(alpha x_{n-k})/(1+x_{n}...x_{n-k}), k>=1, n=0,1,... is studied where the parameters ?alpha, betta, and gamma are positive real numbers, and the initial conditions x_{-k}, ..., x_{0} are given arbitrary real numbers. The forbidden set of this equation is found and then, the order reduction method is used to facilitate the analysis of its asymptotic dynamics
2014-06-30
12211 Research Triangle Park , NC 27709-2211 ----- REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S ACRONYM(S...One theme that will arise repeatedly in the sequel is the connection between concentration and the rate of conver- gence to equilibrium of Markov...that is open for the weak convergence topology . Then lim inf n!1 1 n log P " 1 n n X k=1 X k 2 O # inf ⌫2O D(⌫||µ). Remark 4.33. We have only
强正则自补图的一个注记%A Note on Strongly Regular Self-complementary Graphs
Institute of Scientific and Technical Information of China (English)
田方
2006-01-01
K(o)tzig put forward a question on strongly-regular self-complementary graphs,that is, for any natural number k, whether there exists a strongly-regular self- complementary graph whose order is 4k + 1, where 4k + 1 = x2 + y2, x and y are positive integers; what is the minimum number that made there exist at least two non-isomorphic strongly-regular self-complementary graphs. In this paper, we use two famous lemmas to generalize the existential conditions for strongly-regular self-complementary circular graphs with 4k + 1 orders.
Xi Hongjian; Sun Taixiang; Hong Liang
2006-01-01
We study the global asymptotic behavior of the positive solutions of the system of rational difference equations xn+1 = f(xn,yn-k), yn+1 = f(yn, xn-k), n = 0,1,2,..., under appropriate assumptions, where k ∈ {1,2,...} and the initial values x-k, x-k+1,...,x0, y-k, y-k+1, ..., y0 ∈ (0,+∞). We give sufficient conditions under which every positive solution of this equation converges to a positive equilibrium. The main theorem in [1] is included in our result.
Limits of zeros of polynomial sequences
Zhu, Xinyun; Grossman, George
2007-01-01
In the present paper we consider $F_k(x)=x^{k}-\\sum_{t=0}^{k-1}x^t,$ the characteristic polynomial of the $k$-th order Fibonacci sequence, the latter denoted $G(k,l).$ We determine the limits of the real roots of certain odd and even degree polynomials related to the derivatives and integrals of $F_k(x),$ that form infinite sequences of polynomials, of increasing degree. In particular, as $k \\to \\infty,$ the limiting values of the zeros are determined, for both odd and even cases. It is also ...
New Binomial Bent Function over the Finite Fields of Odd Characteristic
Helleseth, Tor
2009-01-01
The $p$-ary function $f(x)$ mapping $\\mathrm{GF}(p^{4k})$ to $\\mathrm{GF}(p)$ given by $f(x)={\\rm Tr}_{4k}\\big(x^{p^{3k}+p^{2k}-p^k+1}+x^2\\big)$ is proven to be a weakly regular bent function and the exact values of its Walsh transform coefficients are found. The proof is based on a few new results in the area of exponential sums and polynomials over finite fields that may also be interesting as independent problems.
Dielectric relaxation and charged domain walls in (K,Na)NbO3-based ferroelectric ceramics
Esin, A. A.; Alikin, D. O.; Turygin, A. P.; Abramov, A. S.; Hreščak, J.; Walker, J.; Rojac, T.; Bencan, A.; Malic, B.; Kholkin, A. L.; Shur, V. Ya.
2017-02-01
The influence of domain walls on the macroscopic properties of ferroelectric materials is a well known phenomenon. Commonly, such "extrinsic" contributions to dielectric permittivity are discussed in terms of domain wall displacements under external electric field. In this work, we report on a possible contribution of charged domain walls to low frequency (10-106 Hz) dielectric permittivity in K1-xNaxNbO3 ferroelectric ceramics. It is shown that the effective dielectric response increases with increasing domain wall density. The effect has been attributed to the Maxwell-Wagner-Sillars relaxation. The obtained results may open up possibilities for domain wall engineering in various ferroelectric materials.
Xi Hongjian; Sun Taixiang; Hong Liang
2006-01-01
We study the global asymptotic behavior of the positive solutions of the system of rational difference equations xn+1 = f(xn,yn-k), yn+1 = f(yn, xn-k), n = 0,1,2,..., under appropriate assumptions, where k ∈ {1,2,...} and the initial values x-k, x-k+1,...,x0, y-k, y-k+1, ..., y0 ∈ (0,+∞). We give sufficient conditions under which every positive solution of this equation converges to a positive equilibrium. The main theorem in [1] is included in our result.
The Impact of Delayed Topology Information in Proactive Routing Protocols for MANETs
2008-11-28
to obtain information about the change in topology. Let Pfe (l) the probability of failure to received a �ooding message by a node l hops away from the...information inconsistency between a node l 1 hops from the originator of the information and its neighbor at l hops. pic (i; l) is given by pic (i; l) = Pfe ...1) i1 (1 Pfe (1)) ; if l = 1 Pif (l) Pfe (l) i1 (1 Pfe (l)) ; if l > 1 : DT (l 1; l;K;) is then found using DT (l 1; l;K;) = 1X i=1 DT (l
Neilson, James R; McQueen, Tyrel M
2012-05-09
Here, we study the nature of metal-metal bonding in the ThCr(2)Si(2) structure type by probing the rate-limiting steps in the oxidative deintercalation of KNi(2)Se(2). For low extents of oxidation, alkali ions are removed exclusively to form K(1-x)Ni(2)Se(2). For greater extents of oxidation, the rate of the reaction decreases dramatically, concomitant with the extraction of both potassium and nickel to form K(1-x)Ni(2-y)Se(2). The appreciable mobility of transition metal ions is unexpected, but illustrates the relative energy scales of different defects in the ThCr(2)Si(2) structure type. Furthermore, the fully oxidized compounds, K(0.25)Ni(1.5)Se(2), spontaneously convert from the tetrahedral [NiSe(4)]-containing ThCr(2)Si(2) structure to a vacancy-ordered NiAs structure with [NiSe(6)] octahedra. From analysis of the atom positions and kinetic data, we have determined that this transformation occurs by a continuous, low-energy pathway via subtle displacements of Ni atoms and buckling of the Se sublattice. These results have profound implications for our understanding of the stability, mobility, and reactivity of ions in materials.
Institute of Scientific and Technical Information of China (English)
徐昌进
2012-01-01
The dynamical behavior of a discrete competition and corporation dynamical model of two enterprises χ,(k+l)=χ1(k)exP(r1(ki)-a1(k)χ,(k)-b1(k)(χ2i(k)-c2(k))2},χ:2(k+l)=χ2(k)exp{r2(k)-a2(K)χ2（k)+b2(k)× Cχ1(k)— ci(k))2} ,k∈Z is investigated. By suing the coincidence degree and the related continuation theorem and prior estimates, we obtain an easily verifiable sufficient condition for the existence of positive periodic solutions.%研究一个两企业竞争与合作的离散动力学模型:x1 (k+1)=x1(k)exp{r1(k)-a1(k)x1(k)-b1(k)×(x2(k)-c2(k))2},x2(k+1)=x2(k)exp{r2(k)-a2(k)x2(k)+b2(k)(x1(k)-c1(k))2},k∈Z的动力学行为.运用重合度及相关的延拓定理和先验估计,得到系统存在正周期解的易于检验的充分条件.
Energy Technology Data Exchange (ETDEWEB)
Dehghan, Mehdi [Department of Applied Mathematics, Faculty of Mathematics and Computer Science, Amirkabir University of Technology, No. 424, Hafez Ave., Tehran (Iran, Islamic Republic of)]. E-mail: mdehghan@aut.ac.ir; Mazrooei-Sebdani, Reza [Department of Applied Mathematics, Faculty of Mathematics and Computer Science, Amirkabir University of Technology, No. 424, Hafez Ave., Tehran (Iran, Islamic Republic of)]. E-mail: mazrooei@aut.ac.ir
2007-05-15
We obtain some results about the global attractivity of bounded solutions of difference equation x{sub n+1}=f(x{sub n},x{sub n-1},...,x{sub n-k}), n=0,1,... where f is non-increasing or non-decreasing in each argument and every point in I is an equilibrium point of above equation where I is an invariant interval for this equation. By our results we prove that when k is an odd positive integer and p>=1 is a real number, every positive solution ofx{sub n+1}=p+x{sub n-k}1+x{sub n},n=0,1,...converges to a period-two solution of this equation. We also apply our results to the rational difference equationx{sub n+1}=1+x{sub n-2k+1}x{sub n-2l},n=0,1,...where k,l-bar {l_brace}0,1,...{r_brace}, and we show that every positive solution of this equation converges to a period-two solution of this equation.
Wang, Dongyang; Wang, Guangtao
2017-02-01
Based on first-principles calculations we systematically studied the electronic structure and thermoelectric properties of Zr1 - xHfxNiPb (x = 0, 0.25, 0.5, 0.75, 1) compounds with TB-mBJ and TB-mBJ plus spin-orbit coupling methods. Our results indicate that these compounds are thermodynamic stabled narrow-gap semiconductors. The low frequency optical branches intersect with the acoustic modes below 75cm-1 for these artificial compounds, which enhance the phonon scattering and then decrease thermal conductivity. The Hf substitution significantly decreases the lattice thermal conductivity from 13.1Wm-1K-1 (x = 0) to 0.23Wm-1K-1 (x = 0.25) at 300 K. We confirmed that the Hf doping hardly influences the power factors S2 Tσ in both of p- and n-type, but greatly decreases the thermal conductivity κ, i.e. improving the figure of merit ZT =S2 Tσ / κ. The Zr0.75Hf0.25 NiPb , Zr0.5Hf0.5 NiPb and Zr0.25Hf0.75 NiPb , with ultra low thermal conductivity (0.23, 2.2 and 0.48Wm-1K-1 at 300 K) and higher power factor, may become new candidates of high performance thermoelectric materials in both of p- and n-type.
Limit law of the iterated logarithm for -valued trimmed sums
Indian Academy of Sciences (India)
Ke-Ang Fu; Yuyang Qiu; Yeling Tong
2015-05-01
Given a sequence of i.i.d. random variables $\\{X,X_{n};n≥ 1\\}$ taking values in a separable Banach space $(B,\\|\\cdot \\|)$ with topological dual *, let $X^{(r)}_{n}=X_{m}$ if $\\| X_{m}\\|$ is the -th maximum of $\\{\\| X_{k}\\|; 1≤ k≤ n\\}$ and $^{(r)}S_{n}=S_{n}-(X^{(1)}_{n}+\\cdots+X^{(r)}_{n})$ be the trimmed sums when extreme terms are excluded, where $S_{n}=\\sum^{n}_{k=1}X_{k}$. In this paper, it is stated that under some suitable conditions, $$ \\lim\\limits_{n→ ∞}\\frac{1}{\\sqrt{2\\log \\log n}}\\max\\limits_{1≤ k≤ n}\\frac{\\| {}^{(r)}S_{k}\\|}{\\sqrt{k}}=(X)\\quad\\text{a.s.,} $$ where $^{2}(X)=\\sup_{f\\in B^{*}_{1}}\\text{\\sf E}f^{2}(X)$ and $B^{*}_{1}$ is the unit ball of *.
Kovrugin, Vadim M; Colmont, Marie; Siidra, Oleg I; Mentré, Olivier; Al-Shuray, Alexander; Gurzhiy, Vladislav V; Krivovichev, Sergey V
2015-06-11
Chemical vapor transport (CVT) reactions were used to prepare three modular mixed-valent Cu(I)-Cu(II) compounds, (Pb2Cu(2+)9O4)(SeO3)4(Cu(+)Cl(2))Cl5 (1), (PbCu(2+)5O2)(SeO3)2(Cu(+)Cl2)Cl3 (2), and (Pb(x)Cu(2+)(6-x)O2)(SeO3)2(Cu(+)Cl2)K(1-x)Cl(4-x) (x = 0.20) (3). In their crystal structures chains of anion-centered (OCu(2+)4) and (OCu(2+)3Pb) tetrahedra form honeycomb-like double layers with cavities occupied by linear [Cu(+)Cl2](-) groups.
A uniform Berry--Esseen theorem on $M$-estimators for geometrically ergodic Markov chains
Hervé, Loïc; Patilea, Valentin; 10.3150/10-BEJ347
2012-01-01
Let $\\{X_n\\}_{n\\ge0}$ be a $V$-geometrically ergodic Markov chain. Given some real-valued functional $F$, define $M_n(\\alpha):=n^{-1}\\sum_{k=1}^nF(\\alpha,X_{k-1},X_k)$, $\\alpha\\in\\mathcal{A}\\subset \\mathbb {R}$. Consider an $M$ estimator $\\hat{\\alpha}_n$, that is, a measurable function of the observations satisfying $M_n(\\hat{\\alpha}_n)\\leq \\min_{\\alpha\\in\\mathcal{A}}M_n(\\alpha)+c_n$ with $\\{c_n\\}_{n\\geq1}$ some sequence of real numbers going to zero. Under some standard regularity and moment assumptions, close to those of the i.i.d. case, the estimator $\\hat{\\alpha}_n$ satisfies a Berry--Esseen theorem uniformly with respect to the underlying probability distribution of the Markov chain.
Thurnauer, Marion C.; Brown, James W.; Gast, P.; Feezel, Laura L.
Suggestions that the electron acceptor, A 1, in Photosystem I is a quinone have come from both optical and epr experiments. Vitamin K 1 (phylloquinone) is present in the PSI complex with a stoichiometry of two molecules per reaction center. In order to determine if A 1 can be identified with vitamin K 1, X-band and Q-band epr properties of the vitamin K 1 radical anion in frozen alcohol solutions are examined. The results are compared to the epr properties that have been observed for the reduced A 1 acceptor in vivo. The g-values obtained for the vitamin K 1 radical anion are consistent with identifying A 1 with vitamin K 1.
Novel Ammonium Metal Borohydrides
DEFF Research Database (Denmark)
Grinderslev, Jakob; Jepsen, Lars Haahr; Cerny, Radovan
, it cannot store hydrogen reversibly. Recently, the first ammonium metal borohydride, NH4Ca(BH4)3 was published, which may be considered as substitution of K+ by NH4+ in KCa(BH4)3, due to the similar sizes of NH4+ and K+[1]. This compound successfully stabilizes NH4BH4. In the present work, a series of novel......, and the crystal structures and thermal decompositions are investigated. Mixtures of NH4BH4 - NaBH4 do not react, while solid solutions, K1-x(NH4)xBH4, are formed for NH4BH4 - KBH4. For the other composites, novel ammonium metal borohydrides are formed. Several of these structures have been solved from high...
Microwave oven: how to use it as a crystalloid fluid warmer.
Chittawatanarat, Kaweesak; Akanitthaphichat, Siriwasan
2009-11-01
Hypothermia is a common complication in the hypovolemic patient. Warm intravenous fluids have proven valuable at preventing this complication during volume replacement. The microwave oven is considered an applicable alternative method for warming fluids but no protocol has been established. To evaluate the efficacy and affected variables of the microwave oven in warming crystalloid fluids and to determine the appropriate formula for calculating the warming duration. The important variables influencing the operation of the microwave oven include the difference between the crystalloid fluid and room temperature, the microwave oven's capability, variations in microwave irradiation, and fluid shaking. The appropriate formula for calculating warming duration is: Duration (sec) = Volume (cc) x 4.2j.g(-1).K(-1) x Raised temperature DeltaT (K) x 1.1 (Adjusted power) / Mivcwrowave power (W). The microwave oven is a safe and practical method for warming crystalloid fluids.
Multiscale dynamics in relaxor ferroelectrics
Energy Technology Data Exchange (ETDEWEB)
Toulouse, J. [Lehigh University, Bethlehem, PA; Cai, L [Lehigh University, Bethlehem, PA; Pattnaik, R. K. [Lehigh University, Bethlehem, PA; Boatner, Lynn A [ORNL
2014-01-01
The multiscale dynamics of complex oxides is illustrated by pairs of mechanical resonances that are excited in the relaxor ferroelectric K1 xLixTaO3 (KLT). These macroscopic resonances are shown to originate in the collective dynamics of piezoelectric polar nanodomains (PND) interacting with the surrounding lattice. Their characteristic Fano lineshapes and rapid evolution with temperature reveal the coherent interplay between the piezoelectric oscillations and orientational relaxations of the PNDs at higher temperature and the contribution of heterophase oscillations near the phase transition. A theoretical model is presented, that describes the evolution of the resonances over the entire temperature range. Similar resonances are observed in other relaxors and must therefore be a common characteristics of these systems.
Limits of zeros of polynomial sequences
Zhu, Xinyun
2007-01-01
In the present paper we consider $F_k(x)=x^{k}-\\sum_{t=0}^{k-1}x^t,$ the characteristic polynomial of the $k$-th order Fibonacci sequence, the latter denoted $G(k,l).$ We determine the limits of the real roots of certain odd and even degree polynomials related to the derivatives and integrals of $F_k(x),$ that form infinite sequences of polynomials, of increasing degree. In particular, as $k \\to \\infty,$ the limiting values of the zeros are determined, for both odd and even cases. It is also shown, in both cases, that the convergence is monotone for sufficiently large degree. We give an upper bound for the modulus of the complex zeros of the polynomials for each sequence. This gives a general solution related to problems considered by Dubeau 1989, 1993, Miles 1960, Flores 1967, Miller 1971 and later by the second author in the present paper, and Narayan 1997.
UV-C photolysis of endocrine disruptors. The influence of inorganic peroxides
Energy Technology Data Exchange (ETDEWEB)
Rivas, Javier, E-mail: fjrivas@unex.es [Departamento de Ingenieria Quimica y Quimica Fisica, Facultad de Ciencias, Avenida de Elvas S/N, 06071 Badajoz (Spain); Gimeno, Olga; Borralho, Teresa; Carbajo, Maria [Departamento de Ingenieria Quimica y Quimica Fisica, Facultad de Ciencias, Avenida de Elvas S/N, 06071 Badajoz (Spain)
2010-02-15
Norfloxacin, doxycycline and mefenamic acid have been photolysed with UV-C radiation (254 nm) in the presence and absence of inorganic peroxides (hydrogen peroxide or sodium monopersulfate). Quantum yields in the range (1.1-4.5) x 10{sup -3} mol Einstein{sup -1} indicate the low photo-reactivity of these pharmaceuticals. Inorganic peroxides considerably enhanced the contaminants conversion, although no appreciable mineralization could be obtained. A simplistic reaction mechanism for the hydrogen peroxide promoted experiments allowed for a rough estimation of the rate constant between hydroxyl radicals and norfloxacin (k > 1 x 10{sup 9} M{sup -1} s{sup -1}), doxycycline (k > 1.5 x 10{sup 9} M{sup -1} s{sup -1}) and mefenamic acid (k > 11.0 x 10{sup 9} M{sup -1} s{sup -1}).
Sequential unconstrained minimization algorithms for constrained optimization
Byrne, Charles
2008-02-01
The problem of minimizing a function f(x):RJ → R, subject to constraints on the vector variable x, occurs frequently in inverse problems. Even without constraints, finding a minimizer of f(x) may require iterative methods. We consider here a general class of iterative algorithms that find a solution to the constrained minimization problem as the limit of a sequence of vectors, each solving an unconstrained minimization problem. Our sequential unconstrained minimization algorithm (SUMMA) is an iterative procedure for constrained minimization. At the kth step we minimize the function G_k(x)=f(x)+g_k(x), to obtain xk. The auxiliary functions gk(x):D ⊆ RJ → R+ are nonnegative on the set D, each xk is assumed to lie within D, and the objective is to minimize the continuous function f:RJ → R over x in the set C=\\overline D , the closure of D. We assume that such minimizers exist, and denote one such by \\hat x . We assume that the functions gk(x) satisfy the inequalities 0\\leq g_k(x)\\leq G_{k-1}(x)-G_{k-1}(x^{k-1}), for k = 2, 3, .... Using this assumption, we show that the sequence {f(xk)} is decreasing and converges to f({\\hat x}) . If the restriction of f(x) to D has bounded level sets, which happens if \\hat x is unique and f(x) is closed, proper and convex, then the sequence {xk} is bounded, and f(x^*)=f({\\hat x}) , for any cluster point x*. Therefore, if \\hat x is unique, x^*={\\hat x} and \\{x^k\\}\\rightarrow {\\hat x} . When \\hat x is not unique, convergence can still be obtained, in particular cases. The SUMMA includes, as particular cases, the well-known barrier- and penalty-function methods, the simultaneous multiplicative algebraic reconstruction technique (SMART), the proximal minimization algorithm of Censor and Zenios, the entropic proximal methods of Teboulle, as well as certain cases of gradient descent and the Newton-Raphson method. The proof techniques used for SUMMA can be extended to obtain related results for the induced proximal
Institute of Scientific and Technical Information of China (English)
杨战民; 吴明鑫; 任小红; 刘利华
2003-01-01
主要讨论了广义离散线性系统Ex(k+1)=Gx(k)+Hu(k)y(k)=Cx(k)+Du(k)的状态观测器,利用矩阵的奇异值分解和矩阵的广义逆,将广义线性系统化为奇异值标准形∑x1(k+1)=G11x1(k)+G12x2(k)+H1u(k)0=G21x1(k)+G22x2(k)+H2u(k)y(k)=C1x1(k)+C2x2(k)+Du(k)再引入状态补偿反馈u(k)=K1x2(k)+v(k),使得广义系统变为正常系统,从而设计出广义离散线性系统的全维状态观测器.(k+1)=(-K)V(k)+(-K)u(k)u(k+1)+Ky(k)
Prathap Reddy, K.
2016-11-01
An ‘electrostatic bathtub potential’ is defined and analytical expressions for the time period and amplitude of charged particles in this potential are obtained and compared with simulations. These kinds of potentials are encountered in linear electrostatic ion traps, where the potential along the axis appears like a bathtub. Ion traps are used in basic physics research and mass spectrometry to store ions; these stored ions make oscillatory motion within the confined volume of the trap. Usually these traps are designed and studied using ion optical software, but in this work the bathtub potential is reproduced by making two simple modifications to the harmonic oscillator potential. The addition of a linear ‘k 1|x|’ potential makes the simple harmonic potential curve steeper with a sharper turn at the origin, while the introduction of a finite-length zero potential region at the centre reproduces the flat region of the bathtub curve. This whole exercise of modelling a practical experimental situation in terms of a well-known simple physics problem may generate interest among readers.
Reduced order multiport parallel and multidirectional neural associative memories.
Bhatti, Abdul Aziz
2009-05-01
This paper proposes multiport parallel and multidirectional intraconnected associative memories of outer product type with reduced interconnections. Some new reduced order memory architectures such as k-directional and k-port parallel memories are suggested. These architectures are, also, very suitable for implementation of spatio-temporal sequences and multiassociative memories. It is shown that in the proposed memory architectures, a substational reduction in interconnections is achieved if the actual length of original N-bit long vectors is subdivided into k sublengths. Using these sublengths, submemory matrices, T ( s ) or W ( s ), are computed, which are then intraconnected to form k-port parallel or k-directional memories. The subdivisions of N-bit long vectors into k sublengths save ((k-1) x 100) / k % of interconnections. It is shown, by means of an example, that more than 80% reduction in interconnections is achieved. Minimum limit in bits on k as well as maximum limit on subdivisions in k is determined. The topologies of reduced interconnectivity developed in this paper are symmetric in structure and can be used to scale up to larger systems. The underlying principal of construction, storage and retrieval processes of such associative memories has been analyzed. The effect of complexity of different levels of reduced interconnectivity on the quality of retrieval, signal to noise ratio, and storage capacity has been investigated. The model possesses analogies to biological neural structures and digital parallel port memories commonly used in parallel and multiprocessing systems.
Structural and optical properties of sol-gel deposited proton conducting Ta{sub 2}O{sub 5} films
Energy Technology Data Exchange (ETDEWEB)
Ozer, N.; Lampert, C.M.
1995-08-01
Proton conducting tantalum oxide films were deposited by spin coating using a sol-gel process. The coating solutions were prepared using Ta(OC{sub 2}H{sub 5}){sub 5} as a precursor. X-ray diffraction studies determined that the sol-gel films, heat treated at temperatures below 400 C, were amorphous. Films heat treated at higher temperatures were crystalline Ta{sub 2}O{sub 5}. The solar transmission values (T{sub s}) of tantala films on glass generally range from 0.8--0.9 depending on thickness. The refractive index and the extinction coefficient were evaluated from transmittance characteristics in the UV-VIS-NIR regions. The refractive index values calculated at 550 nm increased from 1.78 to 1.97 with increasing heat treatment from 150 to 450 C. The films heat treated at different temperatures showed low absorption with extinction coefficients of less than k=1x10{sup -3} in the visible range. Spectrophotometric and impedance spectroscopic investigations performed on Ta{sub 2}O{sub 5} films revealed that these films have protonic conductivity of 3.2x10{sup -6} S/cm. The films are suitable for proton conducting layers in electrochromic (EC) devices.
Broadband light-scattering spectroscopy on fractal and non-fractal relaxors
Koreeda, Akitoshi; Ogawa, Tomohiro; Katayama, Daisuke; Fujii, Yasuhiro; Tachibana, Makoto
2016-10-01
We show the quasi-elastic light scattering (QELS) spectra of two groups of relaxors: the first group includes relaxors that exhibit glasslike low-temperature thermal conductivity and heat capacity, namely, Pb(Mg1/3Nb2/3)O3 (PMN), (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT), Pb(Zr1/3Nb2/3)O3 (PZN), and (Na1/2Bi1/2)TiO3 (NBT). The other group consists of relaxors exhibiting a normal (crystal) temperature dependence of the thermal conductivity and heat capacity, namely, K1- x Li x TaO3 (KLT) and KTa1- x Nb x O3 (KTN). The crystals of the first group yielded self-similar (power-law) QELS spectra, indicating the existence of fractal networks/clusters of polar nanoregions, while those of the second group did not show any self-similarity in the QELS spectra. These results imply that the glasslike low-temperature thermal conductivity and heat capacity in relaxors can be attributed to the vibrational modes specific to fractal networks/clusters formed by polar nanoregions.
DEFF Research Database (Denmark)
Park, J S; Wood, P M; Davies, Michael Jonathan
1997-01-01
The reaction of Fe(II) oxalate with hydrogen peroxide and dioxygen was studied for oxalate concentrations up to 20 mM and pH 2-5, under which conditions mono- and bis-oxalate complexes (Fe[II](ox) and Fe[II](ox)2[2-]) and uncomplexed Fe2+ must be considered. The reaction of Fe(II) oxalate...... with hydrogen peroxide (Fe2+ + H2O2 --> Fe3+ + .OH + OH-) was monitored in continuous flow by ESR with t-butanol as a radical trap. The reaction is much faster than for uncomplexed Fe2+ and a rate constant, k = 1 x 10(4) M(-1) s(-1) is deduced for Fe(II)(ox). The reaction of Fe(II) oxalate with dioxygen...... by oxalate. Further ESR studies with DMPO as spin trap reveal that reaction of Fe(II) oxalate with hydrogen peroxide can also lead to formation of the carboxylate radical anion (CO2-), an assignment confirmed by photolysis of Fe(II) oxalate in the presence of DMPO....
A First-order Augmented Lagrangian Method for Compressed Sensing
Aybat, Necdet Serhat
2010-01-01
In this paper, we propose a first-order augmented Lagrangian algorithm (FAL) that solves the basis pursuit problem min{|x|_1: Ax = b} by inexactly solving a sequence of problems of the form min{lambda(k) |x|_1+ |Ax-b-lambda(k)theta(k)|_2^2}, for an appropriately chosen sequence of multipliers {lambda(k),theta(k)}. Each of these subproblems are solved using Algorithm 3 in [19] by Paul Tseng wherein each update reduces to "shrinkage" [12] or constrained "shrinkage". We show that FAL converges to an optimal solution x* of the basis pursuit problem, i.e. x*=argmin{|x|_1: Ax= b} and that there exist a priori fixed sequence {lambda(k)} such that for all epsilon>0, iterates x(k) computed by FAL are epsilon-feasible, i.e. |Ax(k) - b|_2 <= epsilon, and epsilon-optimal, | |x(k)|_1 - |x*|_1 | <= epsilon, after O(1/epsilon) iterations, where the complexity of each iteration is O(n log(n)). We also report the results of numerical experiments comparing the performance of FAL with SPA [1], NESTA [18], FPC [10, 11], FP...
[Research on Raman spectra of isooctane at ambient temperature and ambient pressure to 1. 2 GPa].
Zhang, Fei-fei; Zheng, Hai-fei
2012-03-01
The experimental study of the Raman spectral character for liquid isooctane (2,2,4-trimethylpentane, ATM) was con ducted by moissanite anvil cell at the pressure of 0-1.2 GPa and the ambient temperature. The results show that the Raman peaks of the C-H stretching vibration shift to higher frenquencies with increasing pressures. The relations between the system pressure and peaks positions is given as following: v2 873 = 0.002 8P+2 873.3; v2 905 = 0.004 8P+2 905.4; v2 935 = 0.002 7P+ 2 935.0; v2 960 = 0.012P+2 960.9. The Raman spectra of isooctane abruptly changed at the pressure about 1.0 GPa and the liquid-solid phase transition was observed by microscope. With the freezing pressure at ambient temperature and the melting temperature available at 1 atm, the authors got the liquid-solid phase diagram of isooctane. According to Clapeyron equation, the authors obtained the differences of volume and entropy for the liquid-solid phase transition of isooctane: deltaV(m) = 4.46 x 10(-6) m3 x mol-1 and deltaS = -30.32 J x K(-1) x mol(-1).
Bietti, Massimo; Capone, Alberto
2008-01-18
A product and time-resolved kinetic study on the one-electron oxidation of 2-(4-methoxyphenyl)-2-methylpropanoic acid (2), 1-(4-methoxyphenyl)cyclopropanecarboxylic acid (3), and of the corresponding methyl esters (substrates 4 and 5, respectively) has been carried out in aqueous solution. With 2, no direct evidence for the formation of an intermediate radical cation 2*+ but only of the decarboxylated 4-methoxycumyl radical has been obtained, indicating either that 2*+ is not formed or that its decarboxylation is too fast to allow detection under the experimental conditions employed (k > 1 x 10(7) s(-1)). With 3, oxidation leads to the formation of the corresponding radical cation 3*+ or radical zwitterion -3*+ depending on pH. At pH 1.0 and 6.7, 3*+ and -3*+ have been observed to undergo decarboxylation as the exclusive side-chain fragmentation pathway with rate constants k = 4.6 x 10(3) and 2.3 x 10(4) s(-1), respectively. With methyl esters 4 and 5, direct evidence for the formation of the corresponding radical cations 4*+ and 5*+ has been obtained. Both radical cations have been observed to display a very low reactivity and an upper limit for their decay rate constants has been determined as k or=10, with the latter process that becomes the major fragmentation pathway around pH 12.
On Higgs-exchange DIS, physical evolution kernels and fourth-order splitting functions at large x
Energy Technology Data Exchange (ETDEWEB)
Soar, G.; Vogt, A. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Moch, S. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Vermaseren, J.A.M. [NIKHEF, Amsterdam (Netherlands)
2009-12-15
We present the coefficient functions for deep-inelastic scattering (DIS) via the exchange of a scalar {phi} directly coupling only to gluons, such as the Higgs boson in the limit of a very heavy top quark and n{sub f} effectively massless light flavours, to the third order in perturbative QCD. The two-loop results are employed to construct the next-to-next-to-leading order physical evolution kernels for the system (F{sub 2},F{sub {phi}}) of flavour-singlet structure functions. The practical relevance of these kernels as an alternative to MS factorization is bedevilled by artificial double logarithms at small values of the scaling variable x, where the large top-mass limit ceases to be appropriate. However, they show an only single-logarithmic enhancement at large x. Conjecturing that this feature persists to the next order also in the present singlet case, the three-loop coefficient functions facilitate exact predictions (backed up by their particular colour structure) of the double-logarithmic contributions to the fourth-order singlet splitting functions, i.e., of the terms (1-x){sup a} ln{sup k}(1-x) with k=4,5,6 and k=3,4,5, respectively, for the off-diagonal and diagonal quantities to all powers a in (1-x). (orig.)
Magnetic properties of Y3 - x - yPrxLuyFe5O12 garnet films
Azevedo, A.; Cinbis, C.; Kryder, M. H.
1994-05-01
In this work we report on the magnetic and low-field ferromagnetic resonance properties of iron garnet films of general composition Y3-x-yPrxLuyFe5O12 for 0≤x≤0.3 and 0≤y≤0.7. The films were grown onto [111] gadolinium gallium garnet substrates by liquid phase epitaxy. Both growth-induced and cubic anisotropies were investigated by means of torque magnetometry and ferromagnetic resonance at room temperature. The growth-induced anisotropy constant Ku and the first order magnetocrystalline cubic constant K1 exhibit a linear dependence with the praseodymium content. The addition of Lu with Pr enhances both Ku and K1 dependence on the doping, yielding ΔKu/x˜-2.4×105 erg/cm3 and ΔK1/x˜-1.1×105 erg/cm3. The addition of praseodymium in the garnet films significantly improves the soft magnetic properties. In-plane coercivity is about 0.1 Oe and there is a negligible anisotropy in the plane of the film. The effect of the doping by praseodymium and lutetium on the saturation magnetization is insignificant at room temperature.
Estimating kinetic parameters in TGA using B-spline smoothing and the Friedman method
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiaojie; Preto, Fernando [CANMET Energy Technology Centre (CETC), Natural Resources (Canada); de Jong, Wiebren [Faculty 3mE, Department of Process and Energy, ET Section, Delft University of Technology, Leeghwaterstraat 44, 2628 CD Delft (Netherlands)
2009-10-15
The pyrolysis of biomass occurs via several parallel/serial decomposition reactions. The kinetic parameters, namely the activation energy (E) and the pre-exponential factor (k{sub o}), do not remain constant during the pyrolysis process. A modified empirical method is introduced for calculating the activation energy (E) and the pre-exponential factor (k{sub 0}) based on the Friedman analysis [Friedman HL. Kinetics of thermal degradation of char-forming plastics from thermogravimetry - application to a phenolic plastic. [J Polym Sci C 1963;6: 183-95]. The kinetic parameters are expressed as a function of the conversion (x) during the biomass pyrolysis process. The reactions are assumed to be of first order. At least three data sets obtained at different dynamic heating rates are required. From the Friedman analysis, the conversion (x) related functions E = E(x) and k{sub o} = k{sub o}(x) can be obtained by a B-spline regression method. The pyrolysis can hence be described as: dx/ dt=k(1-x)=k{sub o}(x). exp (-E(x)/RT)(1-x). In this paper, the adapted method is applied to pyrolysis of cellulose and two biomass fuels (meat and bone meal, chicken litter). Experiments were carried out at 2, 10 and 50 K min{sup -1} by thermogravimetric analysis. A good fit of the calculated conversion with experimental data was found. (author)
Energy Technology Data Exchange (ETDEWEB)
Abad, M.D. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla), Avda. Americo Vespucio 49, 41092-Sevilla (Spain); Sanchez-Lopez, J.C., E-mail: jcslopez@icmse.csic.e [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla), Avda. Americo Vespucio 49, 41092-Sevilla (Spain); Brizuela, M.; Garcia-Luis, A. [Fundacion Inasmet-Tecnalia, Mikeletegui Pasealekua 2, 20009 Donostia-San Sebastian (Spain); Shtansky, D.V. [State Tecnological University ' Moscow Institute of Steel and Alloys' , Leninsky pr. 4, 119049-Moscow (Russian Federation)
2010-07-30
The tribological performance of nanocomposite coatings containing Ti-B-C phases and amorphous carbon (a-C) are studied. The coatings are deposited by a sputtering process from a sintered TiB{sub 2}:TiC target and graphite, using pulsed direct current and radio frequency sources. By varying the sputtering power ratio, the amorphous carbon content of the coatings can be tuned, as observed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The crystalline component consists of very disordered crystals with a mixture of TiB{sub 2}/TiC or TiB{sub x}C{sub y} phases. A slight increase in crystalline order is detected with the incorporation of carbon in the coatings that is attributed to the formation of a ternary TiB{sub x}C{sub y} phase. An estimation of the carbon present in the form of carbide (TiB{sub x}C{sub y} or TiC) and amorphous (a-C) is performed using fitting analysis of the C 1s XPS peak. The film hardness (22 to 31 GPa) correlates with the fraction of the TiB{sub x}C{sub y} phase that exists in the coatings. The tribological properties were measured by a pin-on-disk tribometer in ambient conditions, using 6 mm tungsten carbide balls at 1 N. The friction coefficients and the wear rates show similar behavior, exhibiting an optimum when the fraction of C atoms in the amorphous phase is near 50%. This composition enables significant improvement of the friction coefficients and wear rates ({mu} {approx} 0.1; k < 1 x 10{sup -6} mm{sup 3}/Nm), while maintaining a good value of hardness (24.6 GPa). Establishing the correlation between the lubricant properties and the fraction of a-C is very useful for purposes of tailoring the protective character of these nanocomposite coatings to engineering applications.
Institute of Scientific and Technical Information of China (English)
邓聚成
1992-01-01
本文讨论含有溶质的流体在两层多孔介质中的渗流问题，即（θ（x，U）t=（K（x，U）Ux-K（x，U））x，（x，t）∈GT，（θ（x，U）V（x，t）t=（DθVx）x-（V（KUx-K））x，（x，t）∈GT，U（x，0）=U0（x），V（x，0）=V0（x），0≤x≤2，U（0，t）-h0（t），U（2，t）=h2（t），0≤t≤T，V（0，t）=g0（t），V（2，t）=g2（t），0≤t≤T。其中θ（x,U)=θ1(x,U)，当（x,t)∈D1=｛0≤x≤1,0≤t≤T｝；θ（x,U)=θ2(x,U)当（x,t）∈D2＋1｛1＜x≤2，0≤t≤T｝。K（x,U)=K1(x,U)当（x,t)∈D1;K(x,U)=K2(x,U)，当(x,t)∈D2。θi，Ki分别是Di上的介质含水率及水力传导率，V是溶质的浓度，此外还要求U，V，K（x,U)(Ux-1)及DθVx+V(KUx-K)在x=1连续。
一类修正的阻尼牛顿法%A Modified Damped Newton Method
Institute of Scientific and Technical Information of China (English)
庞军彦; 李秦
2015-01-01
Based on the methods of Marquardt -Levenber and Goldstein -Price,the damped Newton method x(k+1) =x(k) -λk ["2 f(x(k))]-1 "f(x(k))is improved properly to propose a new algorithm which can avoid the singularity and non-positive definite-ness of two order derivative matrixes in the original algorithm.Thus the iteration can continue under the singular and non-positive defi-nite conditions of two order derivative matrixes.The convergence analysis and steps of the new algorithm are also given.Finally,the numerical tests are conducted.%在 Marquardt ！ Levenber 方法和 Goldstein ！ Price 方法的基础上对阻尼牛顿法 x（k＋1）＝x（k）－λk ["2 f（x（k））]－1"f（x（k））作了适当改进，得出了一种新的算法。与原来算法相比较，新算法避免了二阶导数矩阵的奇异性和非正定性，从而使迭代在二阶导数矩阵奇异和非正定的条件下也能进行。文章还给出了新算法的收敛性分析和算法步骤，最后给出了数值试验。
Directory of Open Access Journals (Sweden)
José Geilson Alves Demétrio
2013-03-01
Full Text Available Geological maps and stratigraphic charts of the Amazon and Solimões sedimentary basins were reviewed, emphasizing the formations Alter do Chão, Içá and Solimões, the largest reserves of fresh groundwater in these basins. The lack of information on these formations was minimized by sample probe and stratigraphic profiles of construction, lithological and geophysical water and oil wells, obtained in the Base Operacional Geólogo Pedro de Moura, Urucu region, about 650 km southwest of Manaus (AM. In the Amazon Basin, the Aquifer System Alter do Chão is characterized by unconfined and confined aquifers, with transmissivity between 1.5 and 9.1 x 10-3 m2/s, indicated for public supply. In the Solimões Basin, this system is confined by Aquiclude Solimões, recovered by the I-Solimões Aquifers. The reserve is estimated as 33,000 km3. The Aquifer System Içá-Solimões, in Urucu, is unconfined-confined, with two aquifers hydraulically connected: the superficial, with top and bottom at depths near 20 and 70 m, respectively; and the deeper, between 50 and 120 m. With an outcrop area of 948,600 km2 in the Solimões Basin, the reservation of this system was estimated as 7,200 km3, less expressive than the Aquifer System Alter do Chão. The average hydrodynamic parameters were: T = 3 x 10-3 m2/s, S = 5 x 10-4 and K = 1 x 10-4 m/s, orders of magnitudes similar to those found in the aquifer Alter do Chão. Assessing the interrelationships and potential of these two regional aquifers sought to contribute to the hydrogeological knowledge in the Amazon Basin region, where researches on groundwater are still incipient.
Zhang, Rong-Zhen; Gashev, Anatoliy A; Zawieja, David C; Davis, Michael J
2007-04-01
The passive and active length-tension relationships of isolated rat mesenteric lymphatics ( approximately 150 microm ID), and adjacent small arteries ( approximately 240 microm) and veins ( approximately 275 microm) were compared under isometric conditions using a wire myograph. About 60% of the lymphatic vessels developed spontaneous contractions in physiological saline solution at nominal preload. To maximally activate smooth muscle, 145 mM K(+) + 5 x 10(-5) M norepinephrine was used for arteries, and 145 mM K(+) + 1 x 10(-6) M substance P was used for lymphatics and veins. In response, arteries exhibited monotonic force development to a plateau level, whereas lymphatics and veins showed biphasic force development, consisting of a transient force peak followed by partial relaxation to a plateau over approximately 5 min. The passive and the active length-tension curves were similar in shape among all three vessels. However, the maximal active tension of arteries (3.4 +/- 0.42 mN/mm) was significantly greater than peak active tension (0.59 +/- 0.04 mN/mm) or plateau tension (0.20 +/- 0.04 mN/mm) in small veins and greater than peak active tension (0.34 +/- 0.02 mN/mm) or plateau tension (0.21 +/- 0.02 mN/mm) in lymphatics. Maximal active medial wall stress was similar between lymphatics and veins but was approximately fivefold higher in small arteries. For lymphatics, the pressure calculated from the optimal preload was significantly higher than that found previously in isobaric studies of isolated lymphatics, suggesting the capacity to operate at higher than normal pressures for increased responsiveness. Our results represent the first mechanical comparisons of arterial, venous, and lymphatic vessels in the same vasculature.
Todd, B A; Inman, C; Sedgwick, E M; Abbott, N J
2000-08-01
The isolated sciatic nerve of the frog Rana temporaria was used for a parallel electrophysiological and electron microscopic examination of the ionic permeability of the perineurium, one component of the blood-nerve barrier. Nerves mounted in a grease-gap chamber for electrophysiological recording showed negligible changes in DC potential (Delta DC) or compound action potential on challenge with 100 mM K(+) Ringer, evidence that the perineurium was tight to K(+). In preparations then fixed and exposed to 5 mM lanthanum in the fixative, and examined in the electron microscope, electron-dense lanthanum deposits were seen between perineurial lamellae, but lanthanum was not detectable within the endoneurium, confirming that the perineurium was also tight to lanthanum. Absence of lanthanum penetration was confirmed by X-ray analysis of electron microscopic sections. In nerves exposed to 2 mM sodium deoxycholate (DOC) in the recording chamber, then challenged with high [K(+)], a moderate increase in perineurial K(+) permeability (P(K)) was observed, but lanthanum was still excluded. Exposure of nerves to 4 mM DOC caused a greater increase in perineurial potassium permeability, and the two nerves with the greatest permeability (P(K) > 1 x 10(-5) cm x sec(-1)) also showed detectable lanthanum within the endoneurium. The results indicate that DOC causes a dose-dependent increase in tight junctional permeability in the perineurium, and that the electrophysiological monitoring of K(+) penetration is a more sensitive measure of small ion permeability than electron microscopical analysis using lanthanum as tracer. Vesicular profiles observed in perineurial lamellae did not form open channels for ion flux across the perineurium in control nerves, or in those exposed to DOC. In preparations where lanthanum reached the endoneurium, lanthanum was observed in dense deposits in the extracellular spaces around nodes of Ranvier, and in the outer mesaxon cleft, but did not penetrate the
Mattei, Jean-Luc; Le Guen, Emmanuel; Chevalier, Alexis; Tarot, Anne-Claude
2015-01-01
This study investigates the magnetocrystalline anisotropy constants (K1) and the saturation magnetostriction constants (λS) of Ni1-xZnxFe2O4 (NiZn) and Ni0.8-xZnxCo0.2Fe1.98O4-δ (NiZnCo) ferrites intended to be used for antenna downsizing. Composite materials constituted of soft ferrite nanosized particles (NiZn or NiZnCo ferrites) embedded in an epoxy matrix are realized. Measurements of their magnetic permeability in the frequency range of 200 MHz-6 GHz are performed. The influence of compressive stress (in the range of 32-96 MPa) on their Ferrimagnetic Resonance (FMR) is demonstrated. An analytical modeling of stress-induced FMR changes is proposed that allows simultaneous determinations of the Natural Ferrimagnetic Resonance (NFMR, F0), K1 and λS of Ni1-xZnxFe2O4 and Ni0.8-xZnxCo0.2Fe1.98O4-δ ferrites. The obtained results for NiZn ferrites are in agreement with literature data, validating both the experimental process and the proposed modeling of the stress-induced FMR changes. Regarding NiZnCo ferrites, extended data on K1 and λS are presented for the first time. Increasing zinc content (x) induces a spin disorder that reduces in a same time K1 and the magnetization at saturation MS. The rapid variation of K1(x) is related to that of the magnetization MS(x) through a power law. The single-ion anisotropy model allows a satisfactory interpretation of K1 dependence on zinc content. The unexpected low values of λS got for NiZnCo ferrites, compared to those got for NiZn ferrites, are also discussed. Application of compressive stress lowers noticeably magnetic losses of Ni0.6Zn0.2Co0.2Fe1.98O4-δ at given frequency, thereby enhancing the ability of this spinel ferrite to be used as a substrate in the aim of antenna miniaturization.
倒向P-推理与属性剩余发现-应用%Backward P-reasoning and Attribution Residual Discovery-Application
Institute of Scientific and Technical Information of China (English)
林宏康; 范成贤; 史开泉
2011-01-01
Using P-reasoning(P= Packet) .backward P-reasoning was presented,which is abbreviated to P '-reasoning. P-1-reasoning is consisted of internal P-1-reasoning and outer P-1-reasoning,or "if ((x)f/k+1, (x)f/k)=>((x)f/k, (x)F/k+1 ), then (αF/k,αf/k+0)=>(αF/k+1,αF/k)" is P-1- reasoning. P-1-reasoning is the dual form of P-reasoning. Internal P-1-reasoning is the dual form of internal P-reasoning. Outer P-1-reasoning is the dual form of outer P-reasoning. P-1-reasoning will be restored into general reasoning if a certain condition is satisfied. P-1 -reasoning is got from inverse problem of P-1-reasoning. Internal P-1-reasoning, outer P-1-reasoning and their structure were given. P-1-reasoning structure and P-1-reasoning theorem were got. The relation of P-1-reasoning and general P-1-reasoning was given. The attribution residual generated by P-1- reasoning was given. Using the studies, the application in information system was given. P-1-reasoning and P-reasoning are two type of dynamic reasoning forms generated by P-sets, which are applied in different area of information system.%利用P-推理(P=Packet),提出倒向P-推理；倒向P-推理简称p-1-推理.P-1推理由内p-1推理(internal P-1 - reasoning)与外p-1推理(outer p-l-reasoning)共同构成；或者,if((x)Fk+1,(x)Fk)(=>)((x)Fk,(x)Fk+1),then(aFk,aFk+1)(=>)(aFk+1,aFk)是p-1-推理.p-1-推理是P-推理的对偶形式；内p-l-推理是内p-推理的对偶形式；外p-1-推理是外P-推理的对偶形式.在一定的条件下,p-1-推理能够被还原成普通推理.p-1-推理是从P-推理的反问题中得到的.给出内P-1-推理、外p-1-推理及其推理结构；给出p-1-推理结构与p-1-推理定理、p-1-推理与普通推理的关系以及p-1-推理与它生成的属性剩余；利用这些研究,给出p-1-推理在信息系统中的应用.p-1-推理与P-推理是P-集合生成的两类动态推理形式,它们在信息系统的不同领域中获得应用.