Nanochannels for low-grade energy harvesting

The exploit of low-grade energies, such as osmotic energy, thermal energy, and mechanical energy, is of great importance to alleviate the energy crisis. However, current energy harvesting technologies are generally plagued by their low efficiencies. Nanofluidic technology that based on the regulation of ion transport at the nanoscale has shown great potential in energy fields. In this review, we focus on the nanochannel-based energy harvesting, including the selectivity and permeability of the nanochannel, the theoretical output energy, and the difference between single- and multi-pore systems. Three typical energy harvesting modes are then introduced. Finally, the challenges are briefly summarized and an outlook of the nanochannel-based energy harvesting technology is provided.     

Density functional steric analysis of linear and branched alkanes

Branched alkane hydrocarbons are thermodynamically more stable than straight-chain linear alkanes. This thermodynamic stability is also manifest in alkane bond separation energies. To understand the physical differences between branched and linear alkanes, we have utilized a novel density functional theory (DFT) definition of steric energy based on the Weiz?cker kinetic energy. Using the M06-2X functional, the total DFT energy was partitioned into a steric energy term (E(s)[ρ]), an electrostatic energy term (E(e)[ρ]), and a fermionic quantum energy term (E(q)[ρ]). This analysis revealed that branched alkanes have less (destabilizing) DFT steric energy than linear alkanes. The lower steric energy of branched alkanes is mitigated by an equal and opposite quantum energy term that contains the Pauli component of the kinetic energy and exchange-correlation energy. Because the steric and quantum energy terms cancel, this leaves the electrostatic energy term that favors alkane branching. Electrostatic effects, combined with correlation energy, explains why branched alkanes are more stable than linear alkanes.     

Electron kinetic energies from vibrationally promoted surface exoemission: evidence for a vibrational autodetachment mechanism

We report kinetic energy distributions of exoelectrons produced by collisions of highly vibrationally excited NO molecules with a low work function Cs dosed Au(111) surface. These measurements show that energy dissipation pathways involving nonadiabatic conversion of vibrational energy to electronic energy can result in electronic excitation of more than 3 eV, consistent with the available vibrational energy. We measured the dependence of the electron energy distributions on the translational and vibrational energy of the incident NO and find a clear positive correlation between final electron kinetic energy and initial vibrational excitation and a weak but observable inverse dependence of electron kinetic energy on initial translational energy. These observations are consistent with a vibrational autodetachment mechanism, where an electron is transferred to NO near its outer vibrational turning point and ejected near its inner vibrational turning point. Within the context of this model, we estimate the NO-to-surface distance for electron transfer.     

Energy transfer from adenosine triphosphate

We suggest a direct molecular mechanism of energy transfer from adenosine triphosphate (ATP) in hydrolysis and phosphorylation reactions, from chemical energy into mechanical energy. Upon hydrolysis of ATP, say bound to a protein, the electrostatic energy of Coulombic repulsion of the ions adenosine diphosphate and phosphate is available to assert a force on a neighboring molecular group in the protein and can do work on that group, or as the ions recede from each without asserting such a force, they gain relative kinetic energy, which, in the absence of dissipative collisions that turn this kinetic energy into heat, can be converted into any other form of energy and work by an impulse, a collision with a neighboring group, without restrictions. Either possibility can be used as a source of activation energy for reactions, as a source of energy to surmount energy barriers in conformational changes, and as a source of work to be done, as in muscle. In some systems where the Gibbs free energy change is fully utilized, all of this energy is turned into mechanical energy, and we suggest a similar mechanism. From the literature we cite some experimental evidence and several quotations indicative of the possibility of our suggestion.     

纳米孔道动电效应能量转换系统的前沿研究进展

可再生清洁能源的开发和利用对人类社会的可持续发展具有重要意义。 基于动电效应的纳米孔道能量转换系统将流体机械能转化为电能,有望应用于微型电源部件、自驱动纳米机器、微机电体系等领域,为清洁能源发电系统的开发提供了全新的选择。 纳米孔道中的机械能-电能转换过程涉及固体孔道与流体界面间的相互作用,合理设计孔道界面的微观结构,对其进行化学修饰及探讨界面间的相互作用,是提高能量转换效率和输出功率的关键。 近年来,随着纳米技术的迅猛发展及人们对界面物理化学的深入研究,纳米孔道结构和纳流体发电体系能被更精准地设计和集成。 本文主要介绍了基于动电效应的纳米孔道能量转换系统的基本概念,重点关注了纳米孔道中动电效应的最新研究进展,并对该领域进行了展望,为纳米孔道动电效应能量转换系统、纳米发电机、自驱动纳米机器、可穿戴器件等领域的进一步发展和应用提供参考。     

势阱中粒子能级与波函数微扰计算的代数递推公式

利用超位力定理(HVT)和Hellmann-Feynman 定理(HFT),导出了由有精确解的势阱的能级值用微扰法直接计算一维势阱的各级近似能级的普遍代数公式,并导出了由能级近似值计算定态波函数近似表达式的代数公式.给出了代数公式具体应用的几个典型一维势阱实例.此法可推广到二维势阱与三维势阱的情形.     

Energy transfer and energy absorption in photon interactions with matter revisited: A step-by-step illustrated approach

A clear understanding of energy transfer and energy absorption in photon interactions with matter is essential for the understanding of radiation dosimetry and development of new dosimetry techniques. The concepts behind the two quantities have been enunciated many years ago and described in many scientific papers, review articles, and textbooks. Data dealing with energy transfer and energy absorption as well as the associated mass energy transfer coefficient and the mass energy absorption coefficient are readily available in web-based tabular forms. However, tables, even when available in detailed and easy to access form, do not lend themselves to serve as visual aid to promote better understanding of the dosimetric quantities related to energy transfer and energy absorption as well as their relationship to the photon energy and absorber atomic number. This paper uses graphs and illustrations, in addition to well-known mathematical relationships, to guide the reader in a systematic manner through the various stages involved in the derivation of energy absorbed in medium and its associated quantity, the mass energy absorption coefficient, from the mass attenuation coefficient.     

外电场下氮化铝分子结构和光谱研究

以6-311＋G(2DF)为基函数, 采用密度泛函B3P86的方法研究了外电场作用下氮化铝(AlN)基态分子的几何结构、HOMO能级、LUMO能级、能隙及谐振频率. 结果表明, 外电场的大小和方向对AlN分子基态的这些性质有明显影响. 在所加的电场范围内, 随着外电场的增大分子键长减小, 谐振频率增大, 总能量升高, 在F＝0.02 a.u.时能量达到最大, 为－297.4217 a.u., 此后继续增大电场强度, 系统总能量则开始降低; EH 和EL 随着电场的增加均逐渐增大, 在 F＝0.01 a.u.时, EH 和EL均取得最大值, 分别为－0.2776和－0.0828 a.u., 随着电场的继续增大, 能级EH和EL均逐渐减小, 而能隙在外电场增大的过程中始终处于减小趋势.     

Energiebestimmung von Alphateilchen mit Festkörperspurdetektoren

Recently a method using solid state track detectors for the energy determination of alpha-particles has been developed in the Central Institute for Nuclear Research at Rossendorf. The method shows a good accuracy and has an energy resolution which is sufficient for the application in several disciplines. The method is based on a determination of the particle ranges in the detector material. The particle energy can be calculated by the known energy—range relationship. In the energy range from 3 to 6 MeV, which is the energy region of the most alpha-emitters, the energy resolution is 50 keV. The accuracy under optimum conditions is about ±50 keV. The efficiency of the method depends on the particle energy and the energy resolution desired. The method can be used for the energy determination of alpha-particles above 2.7 MeV.     

Energy transfer of highly vibrationally excited naphthalene. I. Translational collision energy dependence

Energy transfer between highly vibrationally excited naphthalene and Kr atom in a series of translational collision energies (108-847 cm(-1)) was studied separately using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene in the triplet state (vibrational energy: 16,194 cm(-1); electronic energy: 21,400 cm(-1)) was formed via the rapid intersystem crossing of naphthalene initially excited to the S(2) state by 266 nm photons. The collisional energy transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. At low collision energies a short-lived naphthalene-Kr complex was observed, resulting in small amounts of translational to vibrational-rotational (T-->VR) energy transfer. The complex formation probability decreases as the collision energy increases. T-->VR energy transfer was found to be quite efficient at all collision energies. In some instances, nearly all of the translational energy is transferred to vibrational-rotational energy. On the other hand, only a small fraction of vibrational energy is converted to translational energy. The translational energy gained from vibrational energy extend to large energy transfer (up to 3000 cm(-1)) as the collision energy increases to 847 cm(-1). Substantial amounts of large V-->T energy transfer were observed in the forward and backward directions at large collision energies.     

Synergistic approach to improve "alchemical" free energy calculation in rugged energy surface

The authors present an integrated approach to "alchemical" free energy simulation, which permits efficient calculation of the free energy difference on rugged energy surface. The method is designed to obtain efficient canonical sampling for rapid free energy convergence. The proposal is motivated by the insight that both the exchange efficiency in the presently designed dual-topology alchemical Hamiltonian replica exchange method (HREM), and the confidence of the free energy determination using the overlap histogramming method, depend on the same criterion, viz., the overlaps of the energy difference histograms between all pairs of neighboring states. Hence, integrating these two techniques can produce a joint solution to the problems of the free energy convergence and conformational sampling in the free energy simulations, in which lambda parameter plays two roles to simultaneously facilitate the conformational sampling and improve the phase space overlap for the free energy determination. Specifically, in contrast with other alchemical HREM based free energy simulation methods, the dual-topology approach can ensure robust conformational sampling. Due to these features (a synergistic solution to the free energy convergence and canonical sampling, and the improvement of the sampling efficiency with the dual-topology treatment), the present approach, as demonstrated in the model studies of the authors, is highly efficient in obtaining accurate free energy differences, especially for the systems with rough energy landscapes.     

How the stabilization of INK4 tumor suppressor 3D structure evaluated by quantum chemical and molecular mechanics calculations corresponds well with experimental results: interplay of association enthalpy, entropy, and solvation effects

The folding free energy of the INK4c tumor suppressor core, consisting of 10 helices, was determined as the sum of gas-phase interaction enthalpy, gas-phase interaction entropy, and dehydration and hydration free energy. The interaction energy and the hydration free energy were determined using the nonempirical density functional theory (DFT) method, augmented by a dispersion-energy correction term, the semiempirical density-functional tight-binding method covering the dispersion energy, and the density functional theory/conductor-like screening model (DFT/COSMO) procedure, whereas the interaction entropy was calculated with the empirical Cornell et al. force field. Alternatively, all contributions were evaluated consistently using empirical methods. All the values of the interaction energy of helix pairs are stabilizing, and the dominant stabilizing terms stem from the London dispersion energy and, in the case of charged systems, the electrostatic energy. The stabilization energy of the core, determined as the difference of the energy of the core and 10 separate helices, amounts to approximately 450 kcal/mol. Systematically, the difference in the hydration free energy of a helix pair and its separate components is smaller in magnitude than the interaction energy, and it is negative for some pairs while positive for others. The average total free energy of a core formation amounts to -29.6 kcal/mol (yielded by scaled quantum-chemical methods) and +13.9 kcal/mol (resulting from empirical methods). These values are considerably smaller than their single components, which are dominated by the interaction energy. The computationally predicted interval encloses the experimental value of the folding free energy (-2.8 kcal/mol).     

Energy transfer of highly vibrationally excited naphthalene. II. Vibrational energy dependence and isotope and mass effects

The vibrational energy dependence, H and D atom isotope effects, and the mass effects in the energy transfer between rare gas atoms and highly vibrationally excited naphthalene in the triplet state were investigated using crossed-beam/time-sliced velocity-map ion imaging at various translational collision energies. Increase of vibrational energy from 16 194 to 18 922 cm(-1) does not make a significant difference in energy transfer. The energy transfer properties also remain the same when H atoms in naphthalene are replaced by D atoms, indicating that the high vibrational frequency modes do not play important roles in energy transfer. They are not important in supercollisions either. However, as the Kr atoms are replaced by Xe atoms, the shapes of energy transfer probability density functions change. The probabilities for large translation to vibration/rotation energy transfer (T-->VR) and large vibration to translation energy transfer (V-->T) decrease. High energy tails in the backward scatterings disappear, and the probability for very large vibration to translation energy transfer such as supercollisions also decreases.     

光助燃料电池的研究进展

化石燃料的大量开采和利用所导致的能源与环境问题是当今社会可持续发展必须面对的两大挑战. 燃料电池通过电化学反应将燃料中的化学能直接转化为电能, 是目前清洁高效的可再生能源转化装置. 光助燃料电池将光响应成分引入到燃料电池中, 可以实现光能/电能和化学能/电能的双重转化, 从而有效提高能源利用效率, 是未来能源转化装置的发展方向, 在实际应用方面具有重要意义和广阔前景. 本文对光助燃料电池进行了简要综述, 重点介绍了我们小组近些年来在该领域的相关研究进展, 总结了目前存在的一些问题, 并对其发展趋势进行了展望.     

Multiple discrete energy levels and the bistable state of weak anchoring NLC cells

The weak anchoring nematic liquid crystal (NLC) cell is investigated with regard to energy. Because the Gibbs free energy of liquid crystal system used in theory does not include temperature and entropy, and because the equations and boundary conditions for δG=0 are also the mechanical equilibrium conditions of the continuum, the Gibbs free energy G is equivalent to the energy E of the liquid crystal continuum. There are multiple solutions which satisfy these equations and boundary conditions, each solution corresponding to a certain energy value. We call these discrete energy values and energy levels. Adopting a simple liquid crystal cell model, the energy levels are calculated in detail by means of analytical and numerical methods. The results show that there are three energy levels (or more in certain cases). The values and sequence of the energy levels are related to the external field and anchoring parameters. The relationships between the energy level structure and the bistable. Fréedericksz transition are disussed, together with their influence on the response time. The physical condition for the existence of more than three energy levels is also given.     

高能量激发的发光材料

从不同材料在高能量密度激发下在激发、传递和发光等不同阶段中的效率变化,了解各种材料在高密度激发时的能量损失的主要环节,分清基质和发光中心的选择原则。为投影电视荧光粉和细管灯粉寻找具有较高效率的发光材料,在X线影像板的光激励材料的研制和γ线影像板的可行性分析方面也得到了一些结果。     

碳离子碰撞单壁碳纳米管的动力学

采用分子动力学方法研究了碳离子碰撞碳纳米管中顶位、键中心和六元环中心的动力学过程。通过分析低、中、高3种入射能分别对碰撞过程的影响,探索了典型缺陷形成的微观演化过程。研究结果表明,碰撞碳纳米管中不同空间位置,其碰撞结果差异较大,其中顶位碰撞阈能最低,约为20 eV;碰撞六元环中心时碳管会发生严重变形,损伤最为严重。通过分析入射离子动能,碳纳米管热动能、质心动能以及势能随时间的演化规律,阐述了碰撞过程中的能量转移机制。     

论化学学习中的能量观建构

能量观是中学化学学习中的核心观念。能量观的建构有利于学生形成核外电子运动的能量思维方式,了解从能量的角度研究物质及其转化的思维方法等。能量观建构的基本策略是:(1)在物质的微粒性认识学习中形成物质的微粒具有热能的观念;(2)在原子结构学习中形成核外电子运动的能量思维方式;(3)在元素及其化合物学习中发展高能量的最外层电子不稳定的认识;(4)在化学变化现象的积累学习中强化物质转化伴随有能量变化的认识;(5)通过化学键概念及其理论学习理解物质转化过程中伴随有能量变化;(6)在影响化学反应速率的条件讨论中深化理解有效碰撞理论;(7)在化学热力学问题研究中进一步理解能量守恒;(8)利用概念图技术帮助化学能量观的建构。     

面向能源领域的石墨烯研究

化石能源枯竭以及地球环境污染已经成为并且在未来相当长一段时期内都将是人类面临的最严峻的危机之一.因此,寻找清洁的替代能源形式、有效的能量存储方式以及高效的能源利用途径是目前科学研究的热点.自从其高质量样品被制备和研究以来,石墨烯一直吸引着全世界科研工作者的兴趣;它的一系列独特的物理化学性质,为其在能源领域的应用提供了无限前景.本文对石墨烯在能源领域的最新研究进展以及其工业化应用作了简要综述,具体内容包括石墨烯材料在以下领域的应用：能源储存器件类,如超级电容器和锂离子电池;能源转化装置类,如燃料电池和太阳能电池.     

Recent development and progress of structural energy devices

In order to fully replace the traditional fossil energy supply system, the efficiency of electrochemical energy conversion and storage of new energy technology needs to be continuously improved to enhance its market competitiveness. The structural design of energy devices can achieve satisfactory energy conversion and storage performance. To achieve lightweight design, improve mechanical support, enhance electrochemical performance, and adapt to the special shape of the device, the structural en...