Decision problems for inverse monoids presented by a single sparse relator

We study a class of inverse monoids of the form M=Inv 〈X∣w=1〉, where the single relator w has a combinatorial property that we call sparse. For a sparse word w, we prove that the word problem for M is decidable. We also show that the set of words in (X∪X ⁻¹)^* that represent the identity in M is a deterministic context free language, and that the set of geodesics in the Schützenberger graph of the identity of M is a regular language.     

Observation of two new N* peaks in J/psi-->ppi-n and ppi+n decays

The decay J/psi-->NNpi provides an effective isospin 1/2 filter for the piN system due to isospin conservation. Using 58x10(6) J/psi decays collected with the Beijing Electromagnetic Spectrometer at the Beijing Electron Positron Collider, more than 100 thousand J/psi-->ppi-n+c.c. events are obtained. Besides the two well-known N* peaks at around 1500 MeV/c2 and 1670 MeV/c2, there are two new, clear N* peaks in the ppi invariant mass spectrum around 1360 MeV/c2 and 2030 MeV/c2 with statistical significance of 11sigma and 13sigma, respectively. We identify these as the first direct observation of the N*(1440) peak and a long-sought missing N* peak above 2 GeV/c2 in the piN invariant mass spectrum.     

Stability and bifurcation analysis of a delayed predator-prey model of prey dispersal in two-patch environments

In this paper, a class of delayed predator-prey model of prey dispersal in two-patch environments is considered. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulation for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given.     

An Inventory Model for Deteriorating Items with?Two?Levels of Trade Credit Taking Account of Time Discounting

This paper presents an extended inventory model of Huang (J. Oper. Res. Soc. 54, 1011–1015, 2003), which investigated the retailer’s optimal inventory policy under two levels of trade credit. Herein, we consider the impact of a replenishment policy on the timing of the cash flows associated with payments to suppliers and revenue streams from customers. That is, the same cash amount will possess different money value at different future time. To see this, we adopt the more appropriate net present value (NPV) object instead of the average cost objective. In addition, the deteriorating effects will be incorporated in this inventory model, and the time to deterioration of each item follows an exponential distribution. The discounted cash flow (DCF) approach is used to derive the optimal solution in this study. Furthermore, we first show that the optimal solution not only exists bus also is unique. Then, we provide a theorem to locate the optimal ordering policy. Finally, a numerical example for illustration is provided.     

Absorption/Scattering of Scalar Waves by Dilatonic Black Hole

We investigate the scattering and absorption cross sections of scalar waves by Garfinkle-Horowitz-Strominger (GHS) black hole spacetime with partial wave method. We find that the total absorption cross section oscillates around the geometric optical value, and the scattering angle width becomes narrower and the damping oscillation pattern becomes more complex as l increases. With fixed frequency ω, the main glory peak value becomes higher and the glory width becomes wider as the magnetic parameter a increases.     

Assessment of dispersion corrections in DFT calculations on large biological systems

The performance of empirical dispersion corrections in DFT calculations has been assessed for several large, genuine biological systems that include MbAB, H64L(AB), and V68N(AB) (AB?=?CO, O₂), where Mb stands for a wild-type myoglobin, H64L is the (histidine64?→?leucine) mutated myoglobin, and V68N is the (valine68?→?asparagine) mutated myoglobin. The effects of the local protein environment are accounted for by including the five nearest surrounding residues in the calculated systems and they are examined by comparing the binding energies of AB to the myoglobin and to the porphyrin (Por) without residues. Three versions of Grimme's dispersion correction methods, labeled as DFT-D1, DFT-D2, and DFT-D3, were all tested. In the first version (-D1), the dispersion correction (E_disp) is calculated only for noncovalent interactions between molecular fragments and E_disp within a covalent molecule is not calculated. For the DFT functionals, for which the calculated Por–AB binding energies are already too large, only further overestimation occurs when a dispersion correction is made. The geometry optimizations show that the DFT-D2 and DFT-D3 approaches give too short distances between the residues and the heme moiety in the myoglobins and their calculated relative binding energies ΔE_bind(myoglobin-AB/Por–AB) are in poor agreement with experiment in most cases. DFT-D1 performs very well, ensuring structural and energetic features in close agreement with experiment.     

X波段过模弯曲圆波导TM01-HE11模式变换器研究

在波束波导和反射面天线的馈源应用中, 为了产生低副瓣且方向图等化的高斯波束, 需要将高功率微波转换为准高斯模HE₁₁模辐射. 本文利用弯曲圆波导可同时从TM₀₁模产生TE₁₁模和TM₁₁模的原理, 提出了采用双弯曲过模圆波导结构直接将TM₀₁转换为HE₁₁的模式变换器, 避免了常规微波领域中首先将TM₀₁转换为TE₁₁再用波纹式或半径渐变式TE₁₁-HE₁₁转换器转换为准高斯波束功率容量不足或尺寸过长的不足. 基于模式耦合理论和Taguchi优化算法对模式变换器的弯曲半径、相移直端长度及引入位置进行了优化, 使输出的TE₁₁和TM₁₁成一定比率, 以组成HE₁₁模式, 并对设计的模式变换器进行了全电磁波仿真分析, 结果表明输出波束的标量高斯含量在9.05–9.8 GHz范围内均高于99%, 理论功率容量可达4.5 GW. 关键词： 高功率微波 模式耦合理论 Taguchi优化算法 模式变换器     

ESR and Theoretical Studies of Bis-Benzene-1, 2-Diselenolate Nickel and Related Complexes

Abstract

ESR and theoretical studies of the transition metal complexes of [Co and Ni (Se₂C₆H₄)₂]^? (n-C₄H₉)₄N⁺ are reported and compared with closely related systems. Room temperature single crystal X-ray studies reveal the Nickel complex is orthorhombic. ESR studies of the polycrystalline powders of the Ni complex as a function of temperature from 108 K to room temperature show a series of spectral envelopes which can arise only from a paramagnetic site which possesses axial symmetry. At ca 160 K, there is an abrupt change in the value of the principal components of the anisotropic g-tensor of the Ni complex which is discussed. Low temperature ESR studies of polycrystalline samples of the ground state triplet Cobalt complex which is isomorphous with the Nickel complex reveal an orthorhombic g-tensor. From the field position of the half-field resonance, it is possible to calculate a mean separation, of the two electrons which make up the triplet state, of 4.3 (±0.5) A.     

Threshold concepts in finance: conceptualizing the curriculum

Graduates with well-developed capabilities in finance are invaluable to our society and in increasing demand. Universities face the challenge of designing finance programmes to develop these capabilities and the essential knowledge that underpins them. Our research responds to this challenge by identifying threshold concepts that are central to the mastery of finance and by exploring their potential for informing curriculum design and pedagogical practices to improve student outcomes. In this paper, we report the results of an online survey of finance academics at multiple institutions in Australia, Canada, New Zealand, South Africa and the United Kingdom. The outcomes of our research are recommendations for threshold concepts in finance endorsed by quantitative evidence, as well as a model of the finance curriculum incorporating finance, modelling and statistics threshold concepts. In addition, we draw conclusions about the application of threshold concept theory supported by both quantitative and qualitative evidence. Our methodology and findings have general relevance to the application of threshold concept theory as a means to investigate and inform curriculum design and delivery in higher education.