Semantic Segmentation of Surface Cracks in Urban Comprehensive Pipe Galleries Based on Global Attention.

Cracks inside urban underground comprehensive pipe galleries are small and their characteristics are not obvious. Due to low lighting and large shadow areas, the differentiation between the cracks and background in an image is low. Most current semantic segmentation methods focus on overall segmentation and have a large perceptual range. However, for urban underground comprehensive pipe gallery crack segmentation tasks, it is difficult to pay attention to the detailed features of local edges to obtain accurate segmentation results. A Global Attention Segmentation Network (GA-SegNet) is proposed in this paper. The GA-SegNet is designed to perform semantic segmentation by incorporating global attention mechanisms. In order to perform precise pixel classification in the image, a residual separable convolution attention model is employed in an encoder to extract features at multiple scales. A global attention upsample model (GAM) is utilized in a decoder to enhance the connection between shallow-level features and deep abstract features, which could increase the attention of the network towards small cracks. By employing a balanced loss function, the contribution of crack pixels is increased while reducing the focus on background pixels in the overall loss. This approach aims to improve the segmentation accuracy of cracks. The comparative experimental results with other classic models show that the GA SegNet model proposed in this study has better segmentation performance and multiple evaluation indicators, and has advantages in segmentation accuracy and efficiency.

Hysteresis modeling of magnetic shape memory alloy actuator based on Krasnosel'skii-Pokrovskii model.

As a new type of intelligent material, magnetically shape memory alloy (MSMA) has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP) model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.

catena-Poly[[[diaqua-terbium(III)]-µ-6-carboxy-nicotinato-µ-pyridine-2,5-di-carboxyl-ato] dihydrate].

The title compound, {[Tb(C(7)H(3)NO(4))(C(7)H(4)NO(4))(H(2)O)(2)]·2H(2)O}(n), is isotypic with the analogous Tm(III) compound [Li, Zhang, Wang & Bai (2009). Acta Cryst. E65, m411]. The Tb(III) atom is octa-coordinated by two water mol-ecules and by four carboxyl-ate O atoms and two pyridyl N atoms from two pyridine-2,5-dicarboxyl-ate (2,5-pydc) and two 6-carboxy-nicotinate (2,5-Hpydc) ligands. The 2,5-pydc and 2,5-Hpydc ligands bridge Tb(III) atoms, generating helical coordination polymers along [001]. An extensive network of O-H⋯O hydrogen bonds is formed between the coordination polymers and the uncoordinated water mol-ecules. The refined Flack parameter of 0.54 (2) suggests inversion twinning.

catena-Poly[[(2,2'-bipyridine-κN,N')nickel(II)]-µ-oxalato-κO,O:O,O].

The title compound, [Ni(C(2)O(4))(C(10)H(8)N(2))](n), is isostructural with its Mn(II), Fe(II), Cu(II) and Zn(II) analogues. Each Ni(II) atom is chelated by two oxalate ligands and one 2,2'-bipyridine, forming a slightly distorted octa-hedral geometry. Oxlate acts as a bridge to link neighbouring pairs of Ni(II) cations, forming a one-dimensional wave-like chain. The crystal showed partial inversion twinning.

Tetra-kis(µ-2,4-difluoro-benzoato)bis-[(2,4-difluoro-benzoato)(1,10-phenanthroline)gadolinium(III)].

In the title compound, [Gd(2)(C(7)H(3)F(2)O(2))(6)(C(12)H(8)N(2))(2)], the asymmetric unit comprises one Gd(3+) cation chelated by two 2,4-difluoro-benzoate and one 1,10-phenanthroline ligands. Two cations are linked into a centrosymmetric dimer via three bridging carboxyl-ate groups of 2,4-difluoro-benzoate ligands. Each Gd(3+) ion is nine-coordinated by seven O atoms and two N atoms.

Bis{µ-2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolato}bis-[(thio-cyanato)manganese(III)].

The reported structure is a monoclinic polymorph of the title compound, [Mn(2)(C(16)H(14)N(2)O(2))(2)(NCS)(2)], which has been characterized previously in an ortho-rhom-bic form. Each Mn(III) atom is chelated by a tetra-dentate 2,2'-[ethane-1,2-diylbis(nitrilo-methyl-idyne)]diphenolate ligand and by the N atom of a thio-cyanate anion, in a square-pyramidal arrangement. The complexes form centrosymmetric dimers, with an Mn-O contact of 2.557 (3) Štrans to each thio-cyanate anion, completing a distorted octa-hedral coordination geometry.

Tris[2-(propyl-imino-meth-yl)phenolato-κN,O]cobalt(III).

The title compound, [Co(C(10)H(12)NO)(3)], was synthesized from cobalt(III) fluoride and 2-(propyl-imino-meth-yl)phenol in refluxing methanol. The Co(III) ion is hexa-coordinated by three N and three O atoms from three bidentate Schiff base ligands in an octa-hedral geometry.

µ-Oxido-bis-{chlorido[tris-(2-pyridylmeth-yl)amine]chromium(III)} bis(hexafluoridophosphate).

The title compound, [Cr(2)Cl(2)O(C(18)H(18)N(4))(2)](PF(6))(2), is isostructural with the V(III) analogue. Each Cr(III) atom is chelated by the tetra-dentate tris-(2-pyridylmeth-yl)amine ligand via four N atoms, and further coordinated by one Cl atom and one bridging O atom, giving a slightly distorted octa-hedral coordination geometry. The dinuclear complex is centrosymmetric, with the bridging O atom lying on a centre of inversion.

Diazido-bis(2,2'-biimidazole)cobalt(II).

In the title compound, [Co(N(3))(2)(C(6)H(6)N(4))(2)], the Co(II) atom lies on a centre of inversion and is bonded to two azide ions and two bidentate 2,2'-biimidizole ligands, giving a slightly distorted octa-hedral CoN(6) coordination geometry. In the crystal structure, inter-molecular N-H⋯N hydrogen bonds exist between the 2,2'-biimidizole ligands and the azide ions, linking the complexes into sheets.