In the present paper, the influence of a {101¯2}–{101¯2} secondary twin on detwinning of a {101¯2} primary twin is systematically investigated by compression along the normal direction (ND) of ...pre-strained samples at room temperature. Samples containing both a {101¯2} primary twin and a {101¯2}–{101¯2} secondary twin are prepared by pre-compression along the transverse direction (TD) and subsequent re-compression along the rolling direction (RD) of a hot-rolled AZ31 Mg alloy plate at room temperature. Our results show that the introduction of a {101¯2}–{101¯2} secondary twin into the primary twin can enhance the compression yield strength along the ND. During compression along the ND, the {101¯2}–{101¯2} secondary twin mainly deforms by {101¯2} twinning, forming a {101¯2}–{101¯2}–{101¯2} ternary twin, while detwinning of the {101−2} primary twin also takes place. When a {101¯2}–{101¯2} secondary twin happens to totally separate a {101¯2} primary twin from the matrix, it can serve as a barrier to impede detwinning of this {101¯2} primary twin. The {101¯2} twinning in a {101¯2}–{101¯2} secondary twin can induce a preferred distribution of prismatic planes in twinned regions, which is closely related to the activation of preferential twin variants.
The effect of interaction between {101̅2} twin boundaries (TBs) and 〈a〉 dislocations on deformation behavior of TBs migration process was studied. This TB-dislocation interaction greatly enhances ...activation stress for TB motion and retards TB migration during reloading. Interestingly, a severe TB-dislocation interaction improves strain hardening at the early stage, while reduces the peak hardening rate at the latter stage. High resolution transmission electron microscopy results indicate that severe TB-dislocation interaction greatly damages the coherence of TBs and might induce curving of TBs. Migration of the TBs that intensively interact with dislocations leaves behind low angle boundaries at the initial TBs.
•The widening and growth of DRXed regions induce the formation of shear bands.•Both equiaxed and elongated DRXed grains in submicron scale exist in shear bands.•Deformation twins mainly appear in the ...regions outside of the shear bands.
A Mg–6Zn–0.5Zr alloy (ZK60) plate with a strong basal texture was rolled at 400°C to reductions of 9–48%. Microstructure and texture of the hot-rolled plates were systematically studied with the aim to disclose the formation mechanism of shear bands during hot rolling. Our results show that dynamic recrystallization (DRX) prefers to occur at grain boundaries in a large amount at low rolling reductions. With increasing reductions, the DRXed regions cluster and widen by consumption of the parent grains. Finally, large shear bands appear in the form of symmetric pairs, inclining at an angle of±40° from the rolling direction (RD). Both equiaxed and elongated DRXed grains in submicron scale exist in the shear bands. Deformation twins mainly appear in the regions outside of the shear bands. Both micron-scaled and submicron-scaled {101¯1} contraction twins or {101¯1}-{101¯2} double twins are detected. It seems that those deformation twins do not play an important role in the formation of shear bands during hot-rolling at 400°C. The DRXed grains in the vicinity of grain boundaries have similar orientations to that of their parent grains, while basal poles of the DRXed grains in double twins greatly incline from that of their parent twins. The hot rolling results in scattering of basal poles toward the transverse direction (TD). The maximum intensity of basal poles varies with rolling reductions.
A {101¯2} twinning predominant deformation of polycrystalline Mg alloys is often characterized by a low yield stress and a high degree of strain hardening. In this study, an interrupted ...compression-unloading-annealing-recompression experiment of pure Mg extruded rod was used to study the role of dislocations in strain hardening of compression along the extrusion direction. A quantified contribution of dislocations to strain hardening is analyzed. Our results show that dislocations associated mechanisms play an important role in strain hardening. Below a strain of 2.7%, the dislocation associated mechanisms are the main strain hardening mechanism, generating a hardening of about 8–10MPa. Other mechanisms, e.g. grain refinement and texture hardening by {101¯2} twinning, are not important at this stage. Upon further strain, both the work hardenings from the dislocations and other mechanisms rise. At a strain of 7.2%, the hardening from dislocations associated mechanisms reaches 22MPa, accounting for 45% of the total hardening. It is also found that the grain refinement by twin boundaries is not an important mechanism in work hardening. The work hardening from texture hardening is important in the condition of a high twin volume fraction. With a twin fraction below 20%, the texture hardening mechanism hardly induces an obvious hardening.
This paper proposes an algorithm for the conversion of raster data to hexagonal DGGSs in the GPU by redevising the encoding and decoding mechanisms. The researchers first designed a data structure ...based on rhombic tiles to convert the hexagonal DGGS to a texture format acceptable for GPUs, thus avoiding the irregularity of the hexagonal DGGS. Then, the encoding and decoding methods of the tile data based on space-filling curves were designed, respectively, so as to reduce the amount of data transmission from the CPU to the GPU. Finally, the researchers improved the algorithmic efficiency through thread design. To validate the above design, raster integration experiments were conducted based on the global Aster 30 m digital elevation dataDEM, and the experimental results showed that the raster integration accuracy of this algorithms was around 1 m, while its efficiency could be improved to more than 600 times that of the algorithm for integrating the raster data to the hexagonal DGGS data, executed in the CPU. Therefore, the researchers believe that this study will provide a feasible method for the efficient and stable integration of massive raster data based on a hexagonal grid, which may well support the organization of massive raster data in the field of GIS.
Existing 3d modeling methods for urban buildings suffer from the problem that data acquisition cost and model accuracy are difficult to balance. In this paper, we propose a method for 3D building ...modeling that is driven by knowledge rules using multi-source data. We summarize building structure knowledge rules by analyzing the building design standards, and these knowledge rules are applied to assist the process of extracting modeling information from topographic map DLG and airborne laser point cloud data and reconstructing single building 3D models. Our method achieves an efficient extraction of building models with a level of detail that can meet the needs of urban management. Based on an experiment using real data from the Muyan area of Nanjing, it is demonstrated that this method can balance the data acquisition cost and model accuracy within a certain range. This provides a low-cost and high-efficiency technical route for large-scale acquisition of 3D models of urban buildings.
•3D modeling of buildings is a key issue for real-world 3D construction and city information modeling (CIM).•LoD-2.2 building models can meet the practical urban management needs.•We propose a method for 3D building modeling that is driven by knowledge rules using multi-source data.
In cold regions with high daily temperature gradients (>20 °C), the durability of cement-stabilized macadam (CSM) base materials is poor and prone to cracking. To effectively reduce the cracking of ...semi-rigid base layers in cold regions with high daily temperature gradients and extend fatigue life, this study focused on cracking and fatigue characteristics of CSM with a 10% commercial early strength agent (ESA) added by the external mixing method under different curing conditions. The ESA was manufactured by Jiangsu Subote New Materials Co., Ltd. (Nanjing, China). The curing conditions were divided into variable temperature (0–20 °C) and standard temperature (20 °C). CSM curing was carried out through a programmable curing box. The research results indicated that the variable temperature curing conditions reduced the strength and fatigue resistance of CSM and accelerated the modulus attenuation rate of CSM. At the same time, the drying shrinkage of CSM was greater. The temperature shrinkage coefficient and strain of CSM under variable temperature conditions were smaller than those under standard temperature conditions. The effect of variable temperature conditions on the cracking and durability of CSM could not be ignored in cold regions. Compared to standard temperature curing conditions, the indirect tensile strength of CSM reduced by 31.04% under variable temperature conditions, the coefficient of variation increased by 2.97 times, and the discrete type significantly increased. Compared with CSM without ESA, the dry and temperature shrinkage strains of CSM with 10% ESA were reduced by 24.65% and 26.10%, respectively. At a stress level of 0.6, compared to standard temperature curing conditions, the fatigue life of CSM decreased by 97.19% under variable temperature conditions. Under variable temperature conditions, the fatigue life of CSM with 10% ESA increased by 196 times compared to 0% ESA. Adding ESA enhanced the anti-shrinkage cracking, strength, and durability of CSM under variable temperatures. ESA incorporation effectively compensated for the weakened characteristics of CSM under variable temperature conditions. The study proposed a practical approach for boosting the durability of CSM in cold environments.
Video surveillance systems have been widely used in public security and urban management. Following the increasing demand for video surveillance in various countries worldwide, the number of outdoor ...surveillance cameras is rising. Their unified management and layout optimization have become a great challenge in the construction of video surveillance. Although there is a large number of outdoor surveillance cameras, there exists a lack of spatial location information, leading to difficulties regarding their quantification, space management, and construction status analysis. Hence, a method for estimating the location and orientation of outdoor surveillance cameras based on spatial segmentation and the use of a rapid survey device was proposed. Using the position information obtained from the movement of a designed marker and surveillance images simultaneously captured by each camera, we constructed an initial camera space and segmentation plane using binary space partitioning. By recursive segmentation, the real location of each camera is gradually approximated, and the azimuth angle of the camera orientation is calculated, achieving the rapid estimation of the spatial location and orientation of all surveillance cameras. A city area spanning 2.8 km2 was selected as an experimental area to verify the method proposed here, yielding an average error of 1.78 m between the estimated and actual locations of the cameras and a maximum error of 3.87 m. The average offset between the estimated and actual orientation was 3.13°, with a maximum offset of 6°. Thus, the target of the surveillance camera's estimated deviation is still in the visible range of the operator. The proposed method represents a new way for the rapid investigation of outdoor surveillance cameras and provides a basis for their unified management and layout optimization.
An indoor navigation network, simplified from complex building structures, is of primary importance for indoor navigation. Methods for generating such networks are becoming increasingly important as ...buildings are becoming larger and more complex. However, studies based on the geometry and topology of indoor spaces do not sufficiently account for the key and decision nodes of human wayfinding. This is mainly because the visible perception of pedestrians regarding the corridor path structure is not taken into consideration. In this study, we first propose the indoor visibility map (IVM), calculate the visibility of corridor space, and analyze the relationship between different types of corridors and quantitative visibility parameters of IVM. Based on the visibility analysis, corresponding network construction strategies are suggested for different types of indoor corridors that contain nodes and edges. The experimental results show that the proposed network identifies key locations in the corridor structure that have a decisive role in navigation. Furthermore, the network is simplified to some extent.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
With the continuous development of road construction and maintenance, SBS(Styrene-butadiene-styrene)-modified asphalt is widely used. However, there is no mature method for restoring aged ...SBS-modified asphalt. This study proposes the use of SBR(polymerized styrene butadiene rubber) and bio-oil for the restoration of aged SBS. In this study, five kinds of recycled asphalt were prepared by adding 5% bio-oil, 10% bio-oil, 6% SBR, 6% SBR + 5% bio-oil, and 6% SBR + 10% bio-oil to long-term aged SBS-modified asphalt. Softening point, penetration, and rotational viscosity experiments were tested to evaluate the conventional properties. Rheological tests revealed the performance of asphalt. Fourier transform infrared spectroscopy (FTIR), and atomic force microscope (AFM) tests were tested to demonstrate the microscopic characteristics of asphalt. Conventional tests investigated that aged asphalt viscosity will increase. Bio-oil could well recycle the asphalt viscosity. SBR could also soften aged asphalt, but its modification effect is limited compared with bio-oil. Rheological tests presented that the SBR and bio-oil have little impact on the temperature sensitivity of SBS-modified asphalt. SBR and bio-oil could decrease the asphalt stiffness. However, SBR and bio-oil could ameliorate the anti-cracking behavior of aged asphalt. The microscopic tests exhibited that SBR and bio-oil could decrease the asphaltene and colloid. Meanwhile, bio-oil could supplement alcohols and ethers at wave number 1000 cm
-1270 cm
. Alcohols and ethers are hard to oxidize, something which has a beneficial role in the anti-aged of recycled asphalt.
