Finding Shortest Paths in a Sequence of Triangles in 3D by the Planar Unfolding

We present an efficient algorithm for finding the shortest path joining two points in a sequence of triangles in three-dimensional space using the concept of funnels associated with common edges along the sequence of triangles and the planar unfolding for each funnel. We show that the unfolded image of a funnel is a simple polygon, it thus is non-overlapping. Therefore, such funnels are determined iteratively to their associated common edges by the planar unfolding and the shortest path joining two points is determined by cusps of these funnels.     

An Integrated Market for Electricity and Natural Gas Systems with Stochastic Power Producers

In energy systems with high shares of weather-driven renewable power sources, gas-fired power plants can serve as a back-up technology to ensure security of supply and provide short-term flexibility. Therefore, a tighter coordination between electricity and natural gas networks is foreseen. In this work, we examine different levels of coordination in terms of system integration and time coupling of trading floors. We propose an integrated operational model for electricity and natural gas systems under uncertain power supply by applying two-stage stochastic programming. This formulation co-optimizes day-ahead and real-time dispatch of both energy systems and aims at minimizing the total expected cost. Additionally, two deterministic models, one of an integrated energy system and one that treats the two systems independently, are presented. We utilize a formulation that considers the linepack of the natural gas system, while it results in a tractable mixed-integer linear programming (MILP) model. Our analysis demonstrates the effectiveness of the proposed model in accommodating high shares of renewables and the importance of proper natural gas system modeling in short-term operations to reveal valuable flexibility of the natural gas system. Moreover, we identify the coordination parameters between the two markets and show their impact on the system’s operation and dispatch.     

荧光共振能量转移测定牛血清白蛋白的研究

随着生物分析技术进入了后基因组时代,生命科学领域里的研究课题不断深入,DNA、RNA、蛋白质和其他生物大分子的检测技术发展十分迅速,生命科学中单分子分析技术不断揭示出生命活动的客观规律.相关的新的分析方法和仪器不断取得进展,成为生命科学的前沿领域.     

球磨法制备异质结型光催化剂ZnO/Bi_4Ti_3O_(12)及催化性能

本文用水作为分散介质,掺杂一定量的ZnO于Bi_4Ti_3O_(12)中,采用高能球磨法制备了异质结型光催化剂ZnO/Bi_4Ti_3O_(12).利用UV-Vis、XRD、SEM和PL等仪器对样品进行了分析与表征.以375 W中压汞灯为光源,通过对亚甲基蓝的氧化来研究其光催化活性.结果表明,对于光氧化亚甲基蓝(MB),异质结型光催化剂ZnO/Bi_4Ti_3O_(12)光催化活性高于钛酸铋的光催化活性.当ZnO的掺杂量分别是0.0和0.5wt.%,异质结型光催化剂ZnO/Bi_4Ti_3O_(12)对亚甲基蓝光氧化率分别达到50.2和80.3 %.     

5-氟胞嘧啶气相及水助质子转移异构化的理论研究

采用密度泛函B3LYP/6-311G**方法,对6种5-氟胞嘧啶异构体孤立分子的稳定性及质子转移引起的酮式-烯醇式、氨基式-亚胺式互变异构反应机理进行了计算研究,获得了零点能、吉布斯自由能及质子转移过程的反应焓、活化能、活化吉布斯自由能和速率常数等参数.计算结果表明,气相中烯醇-氨基式FC4是最稳定的异构体.分子内质子转移设计了FC1→FC2和FC1→FC6两条通道,分别标记为P(1)和P(2),各通道速控步骤的活化能和速率常数分别为155.9 kJ·mol-1,4.70×10-15 s-1和173.1 kJ·mol-1,1.41×10-18 s-1.水助催化时,相应通道P(3) 和P(4) 速控步骤的活化能和速率常数分别为51.0 kJ·mol-1,1.41×103 s-1和88.2 kJ·mol-1,4.53×10-3 s-1.可见,水分子的加入极大地降低了质子转移的活化能垒.另外发现,水分子参与形成协同的双质子转移机理比水助单质子转移机理更利于降低活化能垒.     

On isogeny graphs of supersingular elliptic curves over finite fields

We study the isogeny graphs of supersingular elliptic curves over finite fields, with an emphasis on the vertices corresponding to elliptic curves of j-invariant 0 and 1728.     

Chemical Bonding and Electronic Structure of 4d-Metal Monosulfides

Bond distances, vibrational frequencies, dissociation energies, electron affinities, ionization potentials and dipole moments of the title molecules in neutral and charged ions were studied by use of density functional method. Ground states for each molecule were assigned. The calculated bond distance decreases with the increasing of atomic number of 4d metals, reaches minimum at RhS, then increases. For cationic molecules, the calculated bond distance decreases to the minimum at MoS⁺, then increases. The calculated vibrational frequency decreases from YS(YS⁺) to PdS(PdS⁺) for both neutral and cationic molecules. The bond ionic character decreases from YS(YS⁺) to PdS(PdS⁺) for neutral and cationic molecules. The bonding patterns are discussed and compared with the available studies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cations of halogenated methanes: adiabatic ionization energies, potential energy surfaces, and ion fragment appearance energies

The DFT-B3LYP and G3X model chemistry were used to predict the cation structures and energetics of fluorinated, chlorinated, and brominated methanes. Ion–complex structures between methylene cations and HX (X = F, Cl, Br) were found for all H-containing cations, and [CHF–FH]⁺, [CF₂–FH]⁺, [CCl₂–ClH]⁺, and [CCl₂–FH]⁺ structures are more stable than their normal tetravalent structures. Several cations should also be better described as ion–complex structures between methyl cations and halogen atoms, e.g., [CF₃–Br]⁺. Transition states connecting normal and ion–complex structures were also located, and potential energy diagrams were constructed for decomposition of methane cations and to predict the fragmentation pathways. The G3X energies were used to predict the adiabatic ionization energies (IE_as) and ion fragment appearance energies (AEs) from methanes. Many of the experimental AEs correspond to the energies of transition states instead of the thermodynamic dissociation limits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Relative energy of organic compounds I. Hydrocarbons and their oxygen derivatives

The energies of the following types of compounds are characterized by their calculated relative enthalpies: alkanes and cycloalkanes, alkenes and cycloalkenes, polyolefins and cyclic polyolefins, aromatic hydrocarbons, alcohols and phenols, ethers, peroxides, aldehides and ketones, acetals, carboxylic acids esters, and anhydrides. Stabilization energies of conjugated olefins, benzene, and furan have been estimated.     

Formaldehyde interaction with adsorbed oxygen on open-circuit platinum electrodes in aqueous sulfuric acid solutions

The open circuit potential transients and cathodic potentiodynamic pulses were measured upon formaldehyde (methylene glycol) interaction with pre-adsorbed oxygen (O_ads) on Pt/Pt and pc Pt electrodes in aqueous sulfuric acid solutions. The slowest interaction of CH₂(OH)₂ with O_ads was observed in the high coverage range of the electrode surface (θ_O ～ 0.2 0.8 to 1). The process rate in this range is determined by the direct reaction of O_ads with CH₂(OH)₂ molecules from the bulk solution. In the middle surface oxygen coverage range (θ_O 0.2 to 0.8), CH₂(OH)₂ interaction with O_ads takes place by the mechanism of “conjugated reactions”. The kinetic parameters of reactions for CH₂(OH)₂, HCOOH, and CH₃ OH were compared. The rate of CH₂(OH)₂-O_ads interaction on Pt electrodes in the high oxygen coverage range was found higher by an order of magnitude than that of HCOOH and by two orders of magnitude than in the case of CH₃OH.