Experimental and Analytical Analysis of Mechanical Properties for Large-Size Lattice Truss Panel Structure Including Role of Connected Structure

The large-size lattice truss panel structure (LTPS) is continually increasing for higher upsizing, but the roles of its connected structures on the mechanical properties are always ignored during the previous structural integrity assessment. Thus, in this paper, a series of mechanical tests, including the fabricating of panel-to-panel LTPSs, monotonous tensile, and three- and four-point bending tests, were performed to comprehensively understand the mechanical behavior. Furthermore, a theoretical model including the role of connected structures was developed to predict both the elastic and plastic deformation behavior of panel-to-panel LTPS. Results show that the connected structure has a very significant effect on the mechanical properties of panel-to-panel LTPS during the three-bending tests, and I-beam element depresses its carrying capacity. The developed theoretical model was proved to accurately predict the experimental results, and the maximum error was limited within 20%. Finally, the dimensional effects of the connection components on mechanical properties were also analyzed by the theoretical model, and indicated that the panel-to-panel LTPS will present better mechanical performance than the intact structure when the width of I-beam element exceeds 12.2 mm or the its length downgrades to 39.1 mm, which provide a comprehensive guidance for the engineering design of large-size LTPS.

A novel connected structure of all-optical high speed and ultra-compact photonic crystal OR logic gate

A new connected structure of an all-optical “OR” logic gate realized with photonic crystals is proposed in this study. The structure is based on coupling the input guides with two microcavities; the unit cell of the structure is designed to achieve a band gap around the communication wavelength (i.e., 1.55 µm). The performance of the structure results in transmission efficiency and low losses. This compact size logic gate is considered an important element in the integration of a nanoscale photonic device.

Multi-user hybrid precoding for mmWave massive MIMO systems with sub-connected structure

Hybrid precoding achieves a compromise between the sum rate and hardware complexity of millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems. However, most prior works on multi-user hybrid precoding only consider the full-connected structure. In this paper, a novel multi-user hybrid precoding algorithm is proposed for the sub-connected structure. Based on the improved successive interference cancellation (SIC), the analog precoding matrix optimization problem is decomposed into multiple analog precoding sub-matrix optimization problems. Further, a near-optimal analog precoder is designed through factorizing the precoding sub-matrix for each sub-array. Furthermore, digital precoding is designed according to the block diagonalization (BD) technology. Finally, the water-filling power allocation method is used to further improve the communication quality. The extensive simulation results demonstrate that the sum rate of the proposed algorithm is higher than the existing hybrid precoding methods with the sub-connected structure, and has higher energy efficiency compared with existing approaches. Moreover, the proposed algorithm is closer to the state-of-the-art optimization approach with the full-connected structure. In addition, the simulation results also verify the effectiveness of the proposed hybrid precoding design of the uniform planar array (UPA).

SCCDNet: A Pixel-Level Crack Segmentation Network

Cracks are one of the most serious defects that threaten the safety of bridges. In order to detect different forms of cracks in different collection environments quickly and accurately, we proposed a pixel-level crack segmentation network based on convolutional neural networks, which is called the Skip Connected Crack Detection Network (SCCDNet). The network is composed of three parts: the Encoder module with 13 convolutional layers pretrained in the VGG-16 network, the Decoder module with a densely connected structure, and the Skip-Squeeze-and-Excitation (SSE) module which connects the feature map shaving the same resolution in the Encoder and Decoder. We used depthwise separable convolution to improve the accuracy of crack segmentation while reducing the complexity of the model. In this paper, a dataset containing cracks collected in different scenes was established, and SCCDNet was trained and tested on this dataset. Compared with the advanced models, SCCDNet obtained the best crack segmentation performance, while F-score reached 0.7763.

On the Post-Ubaid stratigraphy and complex architecture of the Birecik Dam Area (Turkish Euphrates): Surtepe and Tilbes-Körche Late Chalcolithic 1 levels

During the Later Prehistory of the Euphrates and Tigris Rivers and adjacent regions, a great cultural spread took place during the Late/Terminal Ubaid phases of Southern Mesopotamia. In the Northern Mesopotamian regions, it happened during the immediate pre-Late Chalcolithic phases. Excavations in Southeastern Turkey prove a continuity of Ubaid cultural traits at least during the earlier phases of the local Late Chalcolithic (LC1). Two archaeological sites, Surtepe and Tilbes-Körche, close to the Birecik Dam area (Turkish Euphrates) are presented and evaluated here. Surtepe höyük, a 8 ha Late Ubaid settlement that provided Coba bowls, has levels with painted pottery from the late Late Chalcolithic 1 or earlier LC 2 phases in an area of at least 4 hectares in south and southwestern slopes. The small site of Tilbes-Körche has probably a bigger inter-connected structure and no simple isolated buildings. Among the stone foundations we identify at least one tripartite premise with a surface over 90 m2 and two bipartite buildings. From the largest excavated unit (H3-H10) was recovered a stamp seal depicting a crosshatching motif and another token/stamp seal with 8 incised lines. Within LC1 or a transitional phase between it and LC2, the 18 % of the pottery found in the Tilbes-Körche buildings was painted and there is a huge abundance of unpainted bowls, which are about half the ceramic ensemble, many with traces of a wheel or slow-wheel, mass-produced bowls, various variants of LC1 flint scraped, and two that most resemble the so-called “flower pots”.