Mg_(17)Al_(12)相电子结构计算与键络分析

基于EET理论,计算了Mg-Al系合金中主要的强化相γ-Mg17Al12的价电子结构,分析了其键络空间分布。Mg17Al12空间键络由Al-Al原子集团主键络、Al-MgIII次键络和Al-MgII、Al-MgI弱键络及MgII-MgIII层状键络组成,其中Al-MgIII原子形成的弱键G是整个键络的薄弱环节。Mg17Al12晶内、晶界弥散析出,钉扎位错运动,阻碍晶界滑移传递的强化作用主要依靠Al-Al原子集团主键络。通过合金化增强Mg17Al12弱键G是改善其热稳定性,提高Mg-Al基合金工作温度的有效途径。

高岭石电子结构计算及键络分析

基于"固体与分子经验电子理论(EET)"计算了高岭石的价电子结构,分析了相的空间键络分布,指出了存在的薄弱环节。硅氧四面体中最强键nA=1.37457和次强键nB=1.45692构成了坚固的网状结构;相对而言,铝氧八面体的键合较弱,键强分别为nC=0.38433、nD=0.39188;弱键集中于八面体与四面体的一侧连接上,造成了OI-OⅢ层间键合强度最弱,易于拆散。

Al-Ag合金GP区的价电子结构与界面能

运用固体经验电子理论,对Al-Ag合金GP区?相的价电子结构进行计算,并且在此基础上计算了GP区和基体的界面能。从计算得到的价电子成键的结果中,发现Ag-Ag原子之间的结合倾向最大,表明时效过程中,Ag-Ag原子容易出现偏聚。GP区有较强的共价键络,是Al-Ag合金时效硬化的重要本质原因。从电子成键角度阐明GP区与基体的共格界面能较低,是GP区能够生成长大的重要原因。

钨的价电子结构与硬度和熔点的关系

基于固体与分子经验电子理论(EET),计算了金属钨的价电子结构及晶体中各键上的键能值,研究了相的空间键络分布及键能与熔点的关系。结果表明,钨晶胞中最强键(nA=0.43579)和次强键(nB=0.08562)交织构成了坚固的网状结构,使得晶体具有较高的硬度;最强键的键能EA=113.86587kJ/mol,使金属表现为较高的熔点。

Cu对Zn—27%Al合金组织转变及性能影响的研究

本文首先分析 Cu 对 ZA27合金微观组织的影响;其次依据固体与分子经验电子理论,对 Cu 置换 Al 后面心立方α(或β)晶胞键络进行计算,结果表明,Cu 对α(或β)晶胞的稳定性的影响是比较复杂的。从理论上说明 ZA27合金中Cu 的加入量应有一个适量范围。

Fe_3Al金属间化合物的价电子结构分析

依据固体与分子经验电子理论,对Fe_3Al金属间化合物进行了价电子结构分析,建立了DO_3型晶胞的键络模型,为揭示合金成分—结构—性能与Fe_3Al合金相价电子结构的关系作了一些初步的尝试。

Mg对Zn—27%Al合金组织转变的价电子结构分析

本文首先分析了 ZA27合金的铸态组织,指出其组织组成相为α、β和η。α和β相在固态下将发生一系列转变,η相仅发生长大、粗化和粒化过程。依据“固体与分子经验电子理论”,建立 Al—Zn 二元和 Al—Zn—Mg 三元α(或β)面心立方晶胞的价电子键络模型。计算结果表明:Mg 原子无论是位于面心立方晶胞的面心或是顶角位置,都将加强面心立方晶胞的键络,提高α(或β)晶胞的稳定性,从微观电子结构解释了 Mg 强化合金组织的本质。

Key Environmental Factors Monitoring System of Low-power Greenhouse Based on WSN Technology

A low-power environmental monitoring system based on WSN technology is proposed to effectively monitor the environmental status and ensure the healthy growth of greenhouse crops in the greenhouse. The system performs dynamic mon- itoring on the environmental data of temperature, humidity, illumination, soil tempera- ture and humidity of the greenhouse, and it reduces the energy consumption by us- ing solar energy and lithium battery as the power supply mode and dynamic power management algorithm combined with improved routing protocol. Stable and reliable, the system could effectively monitor the key environmental factors in the green- house, making it of certain promotion value.

Cause Analysis of Consumer‑Grade UAV Accidents Based on Grounded Theory‑Bayesian Network

In order to reduce the accident rate of consumer-grade unmanned aerial vehicles(UAVs)in daily use scenarios,the accident causes are analyzed based on the accident cases of consumer-grade UAVs.By extracting accident causing factors based on the Grounded theory,the relationship between these factors is analyzed.The Bayesian network for consumer-grade UAV accidents is constructed.With the Grounded theory-Bayesian network,the probability of four types of accidents is inferred:fall,air collision,disappearance,and personal injury.With the posterior probability of each factor being reversely reasoned,the causal chain with the maximum probability of each accident is obtained.After the sensitivity of each factor is analyzed,the key nodes in the network accordingly are inferred.Then the causing factors of consumer-grade UAV accidents are analyzed.The results show that the probability of fall accident is the highest,the fall accident is associated with the probabilistic maximum causal chain of personal injury,and the sensitivity analysis results of each type of accident as the result node are inconsistent.

Optimization of air quantity regulation in mine ventilation networks using the improved differential evolution algorithm and critical path method

In mine ventilation networks, the reasonable airflow distribution is very important for the production safety and economy. Three basic problems of the natural, full-controlled and semi-controlled splitting were reviewed in the paper. Aiming at the high difficulty semi-controlled splitting problem, the general nonlinear multi-objectives optimization mathematical model with constraints was established based on the theory of mine ventilation networks. A new algorithm, which combined the improved differential evaluation and the critical path method （CPM） based on the multivariable separate solution strategy, was put forward to search for the global optimal solution more efficiently. In each step of evolution, the feasible solutions of air quantity distribution are firstly produced by the improved differential evolu- tion algorithm, and then the optimal solutions of regulator pressure drop are obtained by the CPM. Through finite steps iterations, the optimal solution can be given. In this new algorithm, the population of feasible solutions were sorted and grouped for enhancing the global search ability and the individuals in general group were randomly initialized for keeping diversity. Meanwhile, the individual neighbor- hood in the fine group which may be closely to the optimal solutions were searched locally and slightly for achieving a balance between global searching and local searching, thus improving the convergence rate. The computer program was developed based on this method. Finally, the two ventilation networks with single-fan and multi-fans were solved. The results show that this algorithm has advantages of high effectiveness, fast convergence, good robustness and flexibility. This computer program could be used to solve lar^e-scale ~eneralized ventilation networks o^timization problem in the future.

KRBKSS: a keyword relationship based keyword-set search system for peer-to-peer networks

may incur significant bandwidth for executing more com- plicated search queries such as multiple-attribute queries. In order to reduce query overhead, KSS (keyword-set search) by Gnawali partitions the index by a set of keywords. However, a KSS index is considerably larger than a standard inverted index, since there are more word sets than there are individual words. And the insert overhead and storage overhead are obviously un- acceptable for full-text search on a collection of documents even if KSS uses the distance window technology. In this paper, we extract the relationship information between query keywords from websites’ queries logs to improve performance of KSS system. Experiments results clearly demonstrated that the improved keyword-set search system based on keywords relationship (KRBKSS) is more efficient than KSS index in insert overhead and storage overhead, and a standard inverted index in terms of communication costs for query.

Infrared Photodisssociation Spectroscopy of Boron Carbonyl Cation Complexes

The boron carbonyl cation complexes B（CO）3＋, B（CO）4＋ and B2（CO）4＋ are studied by infrared photodissociation spectroscopy and theoretical calculations. The B（CO）4＋ ions are characterized to be very weakly bound complexes involving a B（CO）3＋ core ion, which is predicted to have a planar D3h structure with the central boron retaining the most favorable 8-electron configuration. The B2（C0）4＋ cation is determined to have a planar D2h structure involving a B-B one and half bond. The analysis of the B-CO interactions with the EDA- NOCV method indicates that the OC→B cr donation is stronger than the B-＋CO π back donation in both ions.

Preparation and Crystal Structure of Sarcosine 5-Nitrosalicylic Acid Organic Adduct

The title compound (C10H12N2O7, Mr = 272.22) crystallizes in triclinic, space group P1 with a = 5.532(2), b = 9.760(4), c = 11.731(5) ?, α = 68.107(7), β = 89.179(7), γ = 77.830(7)o, V = 573.1(4) ?3, Z = 2, Dc = 1.578 g/cm3, F(000) = 284 and μ(MoKa) = 0.136 mm-1. The final R = 0.0400 and wR = 0.0951 for 1468 observed reflections with I > 2σ(I). The title compound is a 1:1 adduct of sarcosine and 5-nitrosalicylic acid. The nitrogen atom of sarcosine is protonated, and the proton is from the carboxyl group of sarcosine and 5-nitrosalicylic acid with the probability of 50 percent for each. The 5-nitrosalicylic acid and sarcosine molecule of the title adduct are ABAB arranged along the c axis. There exist a lot of hydrogen bonds in the structure, linking sarcosine and 5-nitrosalicylic acid to form a three-dimensional network.

GIS-Based Simulation of Engineering Construction Schedule

For its complexity, engineering construction schedule design is limited by various factors.Simulation-based engineering construction schedule takes critical path method (CPM) network as frame and calls complex cyclic operation network (CYCLONE) simulation model enclosed in advance for its simulation nodes. CYCLONE simulation model takes charge of simulating stochastic duration of activity and efficiency of resources, while CPM model performs project scheduling. This combination avoids the shortcomings of both models. Furthermore, geographic information system (GIS) technique is utilized to visualize the construction processes which are otherwise difficult to be understood by static results described. Application in practical project verifies the feasibility and advantage of the technique.

Self-organized Criticality in an Earthquake Model on Random Network

A simplified Olami-Feder-Christensen model on a random network has been studied. We propose a new toppling rule -- when there is an unstable site toppling, the energy of the site is redistributed to its nearest neighbors randomly not averagely. The simulation results indicate that the model displays self-organized criticality when the system is conservative, and the avalanche size probability distribution of the system obeys finite size scaling. When the system is nonconservative, the model does not display scaling behavior. Simulation results of our model with different nearest neighbors q is also compared, which indicates that the spatial topology does not alter the critical behavior of the system.

T-IP: A Self-Trustworthy and Secure Internet Protocol

IPsec has become an important supplement of IP to provide security protection. However, the heavyweight IPsec has a high transmission overhead and latency, and it cannot provide the address accountability. We propose the self-trustworthy and secure Internet protocol(T-IP) for authenticated and encrypted network layer communications. T-IP has the following advantages:(1) Self-Trustworthy IP address.(2) Low connection latency and transmission overhead.(3) Reserving the important merit of IP to be stateless.(4) Compatible with the existing TCP/IP architecture. We theoretically prove the security of our shared secret key in T-IP and the resistance to the known session key attack of our security-enhanced shared secret key calculation. Moreover, we analyse the possibility of the application of T-IP, including its resilience against the man-in-the-middle attack and Do S attack. The evaluation shows that T-IP has a much lower transmission overhead and connection latency compared with IPsec.

Hydrogen-bond organized 2D metal–organic microsheets:direct ultralong phosphorescence and color-tunable optical waveguides

Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence(RTP). Here, we have designed Zn-IMDC(IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional(2D)hydrogen-bond organized metal–organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal–organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro-and nano-scales.

Surface hydrogen bond network spatially confined BiOCl oxygen vacancy for photocatalysis

Rational engineering of oxygen vacancy(VO) at atomic precision is the key to comprehensively understanding the oxygen chemistry of oxide materials for catalytic oxidations. Here, we demonstrate that VO can be spatially confined on the surface through a sophisticated surface hydrogen bond(HB) network.The HB network is constructed between a hydroxyl-rich Bi OCl surface and polyprotic phosphoric acid,which remarkably decreases the formation energy of surface VO by selectively weakening the metal–oxygen bonds in a short range. Thus, surface-confined VO enables us to unambiguously distinguish the intrafacial and suprafacial oxygen species associated with NO oxidation in two classical catalytic systems.Unlike randomly distributed bulk VO that benefits the thermocatalytic NO oxidation and lattice O diffusion by the dominant intrafacial mechanism, surface VOis demonstrated to favor the photocatalytic NO oxidation through a suprafacial scheme by energetically activating surface O2, which should be attributed to the spatial confinement nature of surface VO.

Heterogeneous self-healing assembly of MXene and graphene oxide enables producing free-standing and self-reparable soft electronics and robots

Self-healing materials(SHMs)with unique mechanical and electronic properties are promising for self-reparable electronics and robots.However,the self-healing ability of emerging two-dimensional(2D)materials,for instance,MXenes,has not been systematically investigated,which limits their applications in self-healing electronics.Herein,we report the homogeneous self-healing assembly(homoSHA)of MXene and the heterogeneous self-healing assembly(hetero-SHA)of MXene and graphene oxide(GO)under moisture treatments.The self-healing mechanism has been attributed to the hydration induced interlayer swelling of MXene and GO and the recombination of hydrogen bond networks after water desorption.The multiform hetero-SHA of MXene and GO not only enables facile fabrication of free-standing soft electronics and robots,but also endows the resultant devices with damage-healing properties.As proof-of-concept demonstrations,free-standing soft electronic devices including a generator,a humidity sensor,a pressure sensor,and several robotic devices have been fabricated.The hetero-SHA of MXene and GO is simple yet effective,and it may pioneer a new avenue to develop miniature soft electronics and robots based on 2D materials.