连接件位置和数量对冷弯薄壁型钢-混凝土组合梁的影响

冷弯薄壁型钢截面板件宽厚比大,因此连接件位置和数量会对冷弯薄壁型钢-混凝土组合梁的变形产生较大的影响。本文用非线性有限元法,分析了弹性阶段和弹塑性阶段连接件数量和位置对组合梁变形以及应力分布的影响。结果表明,冷弯薄壁型钢-混凝土组合梁在不同的连接件数量和位置的情况下,都具有较高的抗弯承载力,变形能力都相当好;连接件位置和数量对冷弯薄壁型钢-混凝土组合梁的变形和应力分布有一定的影响,对极限承载力影响较小。

数据库连接池技术及其在JAVA中的实现

给出了数据库连接池技术的工作原理及流程,旨在使应用系统具有更高的延展性和较高的执行效率,同时可以通过其自身的管理机制来监视数据库连接的数量、使用情况。通过应用实例,讨论了在Java下的开发方法,并得出最终结论:恰当的使用连接池技术将重用消耗的内存资源,节省机器内存,大大提高程序的效率。

普通铸铁双立管通水能力试验研究

介绍了常流量法测试普通铸铁双立管排水系统的测试结果,研究普通铸铁双立管排水系统的通水能力和气压波动情况,利用排水系统水膜流理论分析通气立管与排水立管连接数量的不同对系统压力波动的影响,得到普通铸铁双立管通水能力的相关结论。

2018年中国物联网市场发展现状分析及未来五年发展趋势预测

文中对中国物联网市场发展现状及未来五年发展趋势进行分析预测。预计到2020年,中国LPWA连接数将达6亿部,全球物联网连接数接近200亿部,同时还对比了国内外连接方式的技术参数与连接数占比,指出物联网是运营商拓宽业务的重要方向。

A Quantitative Structure Property Relationship for Prediction of Flash Point of Alkanes Using Molecular Connectivity Indices

Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices （Х）, modified molecular connectivity indices （ ^mХ^v ） and valance molecular connectivity indices （ ^mХ^v ）, with ^mХ^v calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression （MLR） method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.

Guaranteed Rendezvous Algorithms for Cognitive Radio Networks

Rendezvous is a blind process establishing a communication link on a common channel between a pair of nodes in cognitive radio networks. We propose two guaranteed rendezvous algorithms for cognitive radio networks under both single-radio and multi-radio scenarios with an asynchronous setting. For single-radio scenario, each cycle length is a prime number associated with a channel hopping sequence.The rendezvous can be guaranteed as long as the IDs of the two nodes are different. For multi-radio scenario, we propose a cycle length and rotation based rendezvous algorithm. Each node generates a channel hopping sequence with only one cycle length. Then these radios of each nodes rotate on the generated sequence with different rotation numbers at each hopping cycle. The rendezvous between two nodes is guaranteed as long as they have different cycle lengths or the same cycle length with different number of rotations. We conduct simulations on three metrics and the results show that the proposed algorithms outperform the existing ones.

Extending self-organizing maps for supervised classification of remotely sensed data

An extended self-organizing map for supervised classification is proposed in this paper. Unlike other traditional SOMs, the model has an input layer, a Kohonen layer, and an output layer. The number of neurons in the input layer depends on the dimensionality of input patterns. The number of neurons in the output layer equals the number of the desired classes. The number of neurons in the Kohonen layer may be a few to several thousands, which depends on the complexity of classification problems and the classification precision. Each training sample is expressed by a pair of vectors ： an input vector and a class codebook vector. When a training sample is input into the model, Kohonen＇s competitive learning rule is applied to selecting the winning neuron from the Kohouen layer and the weight coefficients connecting all the neurons in the input layer with both the winning neuron and its neighbors in the Kohonen layer are modified to be closer to the input vector, and those connecting all the neurons around the winning neuron within a certain diameter in the Kohonen layer with all the neurons in the output layer are adjusted to be closer to the class codebook vector. If the number of training sam- ples is sufficiently large and the learning epochs iterate enough times, the model will be able to serve as a supervised classifier. The model has been tentatively applied to the supervised classification of multispectral remotely sensed data. The author compared the performances of the extended SOM and BPN in remotely sensed data classification. The investigation manifests that the extended SOM is feasible for supervised classification.

The varieties of Heisenberg vertex operator algebras

For a vertex operator algebra V with conformal vector w, we consider a class of vertex operator subalgebras and their conformal vectors. They are called semi-conformal vertex operator subalgebras and semi- conformal vectors of （V, w）, respectively, and were used to study duality theory of vertex operator algebras via coset constructions. Using these objects attached to （V,w）, we shall understand the structure of the vertex operator algebra （V,w）. At first, we define the set Sc（V,w） of semi-conformal vectors of V, then we prove that Sc（V,w） is an aiYine algebraic variety with a partial ordering and an involution map. Corresponding to each semi-conformal vector, there is a unique maximal semi-conformal vertex operator subalgebra containing it. The properties of these subalgebras are invariants of vertex operator algebras. As an example, we describe the corresponding varieties of semi-conformal vectors for Heisenberg vertex operator algebras. As an application, we give two characterizations of Heisenberg vertex operator algebras using the properties of these varieties.

Mott insulator-superfluid phase transition in a detuned multi-connected Jaynes-Cummings lattice

The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-connected Jaynes-Cummings lattice, which can be constructed with superconducting circuits. This model is composed of alternatively connected qubits and cavity modes.Using a numerical method, we show that by varying the detuning between the qubits and the cavities, a phase transition from the superfluid phase to the Mott insulator phase occurs at commensurate fillings in a one-dimensional array. We study the phase transition in lattices with symmetric and asymmetric couplings, respectively.

Energy of a solid sphere under nonstationary oscillations

Analytical solution for spherically symmetric nonstationary oscillations of acoustic and elastic solid sphere is given.Time dependence of potential,kinetic and internal energy of a solid sphere is analyzed.The received results are of practical importance for a wide range of problems connected to testing of material dynamic strength parameters and to the problems of optimizing(minimizing)energy needed for fracture of solids.

Digital output compensation for precise frequency transfer over commercial fiber link

An ultra-highly precise and long-term stable frequency transmission system over 120 km commercial fiber link has been proposed and experimentally demonstrated. This system is based on digital output compensation technique to suppress phase fluctuations during the frequency transmission process. A mode-locked erbium-doped fiber laser driven by a hydrogen maser serves as an optical transmitter. Moreover, a dense wavelength division multiplexing system is able to separate forward and backward signals with reflection effect excluded. The ultimate fractional frequency instabilities for the long-distance frequency distributed system are up to 3.14×10^(-15) at 1 s and 2.96×10^(-19) at 10 000 s, respectively.