基于自适应多类中心和半异构网络的三维模型草图检索

草图具有易于构建且不受语言、专业、年龄限制等优势,基于手绘草图的三维模型检索受到越来越多的关注。然而在三维模型草图检索任务中,三维模型具有复杂性,草图具有类内多样性,同时三维模型与草图之间又具有巨大的域间差异性,这些特点的相互作用严重影响检索的准确性。针对以上问题,提出了一种基于自适应多类中心和半异构网络的三维模型草图检索方法。首先,通过异构网络分别提取草图和三维模型的初始特征:设计了基于自适应多类中心的草图特征嵌入子网络以捕捉草图数据的类内多样性,采用了基于多视图特征融合的三维模型特征嵌入子网络适应三维模型的复杂性。然后,以包含丰富语义信息的语义标签为指引,构建同构网络实现草图-三维模型的跨域共享特征嵌入,缩小域间的差异性。在大型公开数据集SHREC2013和SHREC2014上的对比实验表明,该算法获得了和当前最好算法一致的检索性能。

基于隐状态排序的半异构无线定位方法

针对室内Wi-Fi环境的信号缺失问题,提出一种基于隐状态排序的半异构无线定位方法。介绍隐马尔可夫模型、隐状态排序方法,设计包含离线训练阶段和在线定位阶段的定位方法。实验结果表明,该方法在1 m误差范围内准确率达96.3%,能解决半异构特征向量的信号缺失问题,提高实际应用能力。

Electronic and Shallow Impurity States in Semiconductor Heterostructures Under an Applied Electric Field

With the use of variational method to solve the effective mass equation, we have studied the electronic and shallow impurity states in semiconductor heterostructures under an applied electric field. The electron energy levels are calculated exactly and the impurity binding energies are calculated with the variational approach. It is found that the behaviors of electronic and shallow impurity states in heterostructures under an applied electric field are analogous to that of quantum wells. Our results show that with the increasing strength of electric field, the electron confinement energies increase, and the impurity binding energy increases also when the impurity is on the surface, while the impurity binding energy increases at first, to a peak value, then decreases to a value which is related to the impurity position when the impurity is away from the surface. In the absence of electric field, the result tends to the Levine's ground state energy (-1/4 effective Rydberg) when the impurity is on the surface, and the ground impurity binding energy tends to that in the bulk when the impurity is far away from the surface. The dependence of the impurity binding energy on the impurity position for different electric field is also discussed.

Reciprocal Effects of Plant-Soil Relationships at Two Spatial Scales in a Semiarid Land of Central Mexico

We studied the influence of soil heterogeneity on plant community structure in a semiarid region of Central Mexico using Bray-Curtis Ordination. The results showed that some edaphic factors, such as soil depth, organic matter, and potassium and calcium content, explained 80% of the total variation in structure of the studied communities. We found that soil resources were heterogeneously distributed in the study area, indicating that the edaphic variables considered in this study explain the existing plant community variability, moreover the presence of some shrubs as Krameria cytisoides influences the soil properties, suggesting that there is a reciprocal effect between plant and soil.

Calculations of electric quadrupole moments and charge radii for high-K isomers

Configuration-constrained potential-energy-surface calculations are performed to investigate high-K isomers in97Y,130Ba,176Yb,177Lu,and178Hf that were observed to have increased electric quadrupole moments but decreased charge radii relative to the states on which they are built.Taking into account the efects of deformation change and unpaired protons,our calculations can reproduce the enhancement of electric quadrupole moments for the isomers in97Y,130Ba,176Yb,177Lu and the Kπ=8 isomer in178Hf,and can reproduce the reduction of charge radii for the Kπ=27/2 isomer in97Y and the Kπ=16+isomer in178Hf.

Bandgap-tunable lateral and vertical heterostructures based on monolayer Mo1-xWxS2 alloys

The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.

Excellent photothermal conversion of core/shell CdSe/ Bi2Se3 quantum dots

Water-dispersed CdSe/Bi2Se3 core/shell QDs with a photothermal conversion coefficient of 27.09% have been synthesized by a cation exchange reaction. The microstructure and crystal structure of the QDs, which were confirmed by TEM and XRD, showed that partial cation exchange occurred inside the CdSe QDs. Two main mechanisms are responsible for the excellent photothermal conversion： inhibition of radiative recombination of carriers due to the formation of type-II semiconductor heterostructures, and the large surface-to-volume ratio of the QDs. Photothermal conversion experiments indicated that the CdSe/Bi2Se3 QDs showed high photothermal conversion efficiency and excellent NIR photostability.

Monitoring disulfide bonds making and breaking in biological nanopore at single molecule level

Monitoring subtle changes in ionic current flow through a nanopore could be applied to observe single molecule reaction. Here,we introduced cysteine to substitute for lysine at position 238 constructing a mutant aerolysin K238 C. It could be regarded as a nanoreactor to efficiently visualize chemical bonds making and breaking. The compound 5,5′-dithiobis-(2-nitrobenzoic acid)(DTNB) was selected as a reactant coming into collisions on the interface of the pore to occur a reversible reaction. Our results showed that the mutant aerolysin could respond to three molecules of DTNB simultaneously and reflect corresponding levels with distinguishable current signals. Therefore, this method constitutes a simple, generic tool for monitoring single molecule reaction, which evokes a guidance for the mutant aerolysin towards the application of tracking other more reactions at single molecule level.

Experimental demonstration of the three-phase-shifted DFB semiconductor laser with buried heterostructure using common holographic exposure

In this article, we report the first experimental demonstration of the three-phase-shifted （3PS） DFB semiconductor laser with buried heterostructure based on the Reconstruction-Equivalent-Chirp （REC） technique. The simulation results show that the performances of the equivalent 3PS DFB semiconductor laser are nearly the same as those of the true 3PS laser. Compared with the quarter-wave-phase shift （QWS） DFB semiconductor laser, the 3PS DFB semiconductor laser shows better single-longitude-mode （SLM） property even at high injection current with high temperature. However, it only changes the ~un-level sampling structures but the seed grating is uniform using the REC tech- nique. Therefore, its fabrication cost is low.

Superheating and melting behaviors of Ag clusters with Ni coating studied by molecular dynamics and experiments

Using molecular dynamics with embedded-atom-type interatomicpotentials, we simulated the melting behavior of a spherical Ag3055 cluster coated with Ni. The semi-coherent Ag/Ni interface formed at low temperatures acts as an effective barrier against the surface melting and leads to a substantial superheating of the Ag cluster. The melting point was found to be about 100 K above the equilibrium melting point of the bulk Ag crystal (1230 K±15 K) and about 290 K above that (1040 K) of the free Ag3055 cluster. A superheating of 70 K was observed in the high-temperature differential scanning calorimetry measurement for Ag particles with a mean size of 30 nm embedded in Ni matrix prepared by means of melt-spinning. Melting is initiated locally at the defective interfacial area and then propagates inwards, suggesting a heterogeneously nucleated melting event at the Ag/Ni interface.