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971.
Xiaojiang Tan 《数学学报(英文版)》1995,11(3):232-246
LetX be a generic smooth irreducible complex projective curve of genusg withg4. In this paper, we generalize the existence theorem of special divisors to high dimensional indecomposable vector bundles. We give a necessary and sufficient condition on the existence ofn-dimensional indecomposable vector bundlesE onX with det(E)=d, dimH
0(X,E)h. We also determine under what condition the set of all such vector bundles will be finite and how many elements it contains.Project partly supported by the National Natural Science Foundation of China. 相似文献
972.
Currently available approaches to molecular-scale logic gates are summarized and compared. These include: chemically-controlled fluorescent and transmittance-based switches concerned with small molecules, DNA oligonucleotides with fluorescence readout, oligonucleotide reactions with DNA-based catalysts, chemically-gated photochromics, reversibly denaturable proteins, molecular machines with optical and electronic signals, two-photon fluorophores and multichromophoric transient optical switches. The photochemical principles of electron and energy transfer are involved in several of these approaches. More complex molecular logic systems with reconfigurability and superposability provide contrasts with current semiconductor electronics. Integration of simple logic functions to produce more complex ones is also discussed in terms of recent developments. 相似文献
973.
Small metal clusters, like Au55(PPh3)12Cl6, which fall in the size regime of 1–2 nm are colloidal nanoparticles with quantum properties in the transitional range between metals and semiconductors. These chemically tailored quantum dots show regarding the Quantum Size Effect (QSE) a level splitting between 20 and 100 meV, increasing from small particle sizes to the molecular state. The organic ligand shell surrounding the cluster acts like a dielectric spacer generating capacitances between neighboring clusters down to 10–18 F. Therefore, charging effects superposed by level spacing effects can be observed. The ligand-stabilized colloidal quantum dots in condensed state can be described as a novel kind of artificial solid with extremely narrow mini or hopping bands depending on the chemically adjustable thickness of the ligand shell and its properties. Since its discovery, the Single Electron Tunneling (SET) effect has been recognized to be the fundamental concept for ultimate miniaturization in microelectronics. The controlled transport of charge carriers in arrangements of ligand-stabilized clusters has been observed already at room temperature through Impedance Spectroscopy (IS) and Scanning Tunneling Spectroscopy (STS). This reveals future directions with new concepts for the realization of simple devices for Single Electron Logic (SEL).
Part I presents the fundamental aspects of small ligand-stabilized metal clusters as well as their physical properties, emphasizing their electronic and optical properties with respect to dielectric response at ambient temperatures. 相似文献
974.
为解决化学审美教育空洞、肤浅、窄化的问题,提出"审美逻辑树"的思维工具。审美逻辑树包括美的产生(树干)、美的感受(一级分枝)、美的鉴赏(二级分枝)、美的延伸(三级或更高级分枝)等多条逻辑链(树枝)。三级分枝的内涵分别是:从实验现象中获得美感、分析美产生的原因、联想其他事物相近的美,核心分别是:外在形态、内在规律、普遍联系,层层递进。审美逻辑树以"美"为内在逻辑,因此可以跨越学科边界无限延伸,将实验现象、科学规律,甚至万事万物联系起来,促进化学与美学的联姻,甚至各学科各领域的大融合。 相似文献
975.
976.
This research studies urban soundscapes through the comparative analysis of twelve public open spaces in the city of Córdoba (Argentina), taken as case studies. The work aims to examine selection of indicators and assessment tools intended to characterize soundscape quality. The field study was carried out through surveys and acoustic and psychoacoustic indicators, that are used together to objectively describe the sound quality of urban spaces. 相似文献
977.
PLC逻辑控制是HL-2A中央控制系统的重要组成部分,改造前的逻辑控制系统基本使用硬连接,维护耗时耗力。结合新一代实时工业以太网PROFINET为HL-2A逻辑控制系统的改造设计了环形冗余网络。采用8台西门子交换机SCALANCE X200通过光纤依次连接成环,交换机的电口连接S7-400和上位机,与等离子体放电相关的重要信号仍走硬连接,其他所有信号都走网络传送。中控系统作为管理站对其他7个子系统进行集中化管理,中控可以轻松快速地获取每个子系统的状态,在等离子体放电错误时能很快的预测事故地点和故障分析。根据放电实验结果表明,光纤环网非常适用于设备分散的慢控制系统,整个控制系统逻辑关系清楚,后期扩展和改造也非常方便。改造后的逻辑控制系统能满足HL-2A和HL-2M两套装置的慢控制,维护简便,事故定位快准,提高了放电效率。 相似文献
978.
Ruthenium‐Amine Conjugated Organometallic Materials for Multistate Near‐IR Electrochromism and Information Storage 下载免费PDF全文
Jian‐Hong Tang Chang‐Jiang Yao Bin‐Bin Cui Yu‐Wu Zhong 《Chemical record (New York, N.Y.)》2016,16(2):754-767
Monometallic and dimetallic complexes with the ruthenium‐amine conjugated structural unit have been prepared. These complexes display consecutive redox waves with low potentials and rich and intense absorptions in the near‐infrared region. The electrochemical and spectroscopic properties can be modulated using substituents or auxiliary ligands with different electronic natures. Through simple functionalization, electropolymerized or monolayer thin films of these complexes have been prepared. These films display multistate near‐infrared electrochromism with good contrast ratios and long optical retention times. In addition, flip‐flop and flip‐flap‐flop memories have been demonstrated on the basis of these thin films.
979.
Khatereh Rezaeian 《Supramolecular chemistry》2016,28(3-4):256-266
A novel azoimine dye-based colorimetric chemosensor (1) has been designed and synthesised for dual recognition of copper(II) and fluoride ions in aqueous media. Significantly, the outstanding dual-ion recognition properties along with the excellent reversibility prompted us to consider 1 as an ideal candidate for fabrication of multiple logic circuits. According to the response profile of 1 towards Cu2+ and F? inputs, we developed a unique tunable system integrated with one INHIBIT logic gate as well as one OR gate. Also, 1 behaved as a molecular keypad lock with sequential addition of Cu2+ and F? inputs. In accession, a reversible ‘Write–Read–Erase–Read’ function with complementary ‘IMP/INH’ logic gate has been demonstrated through a feedback loop using F? and trifluoroacetic acid as two chemical inputs. To the best of our knowledge, this is the first report where the symmetrical bis azo-azomethine dye has been exploited as a molecular keypad lock. 相似文献
980.