In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding (P-FCAW) process in the horizontal position. The results indicate the presence of a stable “flux pole” during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this “flux pole” was beneficial for droplet transfer in the “axial droplet transfer” mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter, rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position.

This research focused on developing a modified chemical precipitation (MCP) method for treating wet flue gas desulfurization (FGD) waste water by adding a solid powder reagent directly. Simulated wet FGD wastewater was treated by MCP method in simulation experiments. Optimization experiments were carried out with the help of response surface methodology (RSM) and central composite design (CCD) to evaluate the effects and the interactions of experimental variables, including reagent dosage, temperature and pH value. The optimal reagent dosage, temperature and pH value were 3018.0 mg/L, 40.5 °C and 5.7, respectively. The RSM was demonstrated as an appropriate approach for the optimization of wet FGD wastewater treatment with the MCP method. A comparative study between the MCP method and the traditional chemical precipitation (TCP) method on raw wet FGD wastewater treatment was conducted. Results indicate that the MCP had less reagent dosage and variety than the TCP method had. Thus, the MCP method had a lower cost.

To obtain the relationship between use of installment tensioning technology and the bearing capacity of prestressed concrete beams, tensile and cyclic loading tests are conducted on five rectangular prestressed concreted specimens. Two types of prestressed tensioning methods are adopted in the tests, one uses installment tensioning technology to tension beams on days 4, 12, and 8, 12, respectively, and the other adopts the conventional method to tension the beam on day 28 only. The age of concrete, number of times tensioned, and the prestress value of early tensioning are considered in tests. Results show that use of installment tensioning technology has no effect on the bending failure pattern of prestressed concrete beams, but it reduces prestress loss and increases crack and yield loads.

In this paper, the effects of second-order difference-frequency wave forces on the global motion of an offshore wind turbine system with a large displacement under the survival condition are studied. In this case, the hydrodynamic force is the main force because the blades are feathered to reduce the lifting force. The first-order hydrodynamic forces are calculated by WADAM, while the second-order wave forces are calculated by a customized MATLAB module. Then the hydrodynamic coefficients are transferred to the wind turbine analytical code FAST. Through the comparisons of dynamic responses between the first- and second-order numerical models, it is found that the second-order wave forces significantly influence the motion of floating wind turbine under the survival condition. Moreover, neglecting the second-order force significantly underestimates the tension forces in the mooring lines.

As an important element in sustainable building design, the building envelope has been witnessing a constant shift in the design approach. Integrating multi-objective optimization (MOO) into the building envelope design process is very promising, but not easy to realize in an actual project due to several factors, including the complexity of optimization model construction, lack of a dynamic-visualization capacity in the simulation tools and consideration of how to match the optimization with the actual design process. To overcome these difficulties, this study constructed an integrated building envelope design process (IBEDP) based on parametric modelling, which was implemented using Grasshopper platform and interfaces to control the simulation software and optimization algorithm. A railway station was selected as a case study for applying the proposed IBEDP, which also utilized a grid-based variable design approach to achieve flexible optimum fenestrations. To facilitate the stepwise design process, a novel strategy was proposed with a two-step optimization, which optimized various categories of variables separately. Compared with a one-step optimization, though the proposed strategy performed poorly in the diversity of solutions, the quantitative assessment of the qualities of Pareto-optimum solution sets illustrates that it is superior.

Gaining a thorough understanding of the theoretical principles of rock breaking with a disc cutter is a critical issue in tunnel boring machine (TBM) technology. To fully consider the complexity and importance of the basic principles of rock breaking during tunnel excavation, in this paper we use a new method, the smooth particle hydrodynamics (SPH), to study the rock-breaking mechanism and verify its accuracy and feasibility. Using the SPH method, we induce the rock fragmentation process with two cutters in synchronous and sequential orders. The results show that when the cutters act on rock sequentially, the second indentation influences the crack evolution of the first indentation. With increased cutter spacing, the second crack gradually becomes independent of the first crack. Under synchronous action of the two cutters, a bursiform nucleus is generated beneath the cutters and the area of the nucleus increases with increased cutter spacing. Whether the cutters act on the rock sequentially or synchronously, we found the optimum cutter spacing of our chosen rock type to be 60 mm. Our analyses results show that the efficiency of sequential rock cutting is superior to synchronous cutting, both with respect to crack evolution and cutter force.

The stress intensity factor (SIF) is a critical parameter associated with the fracture behaviour of materials. In this paper, we select the displacement function around a crack tip as the shape function of the digital image correlation (DIC), which makes it possible to directly calculate the SIF by the correlation scheme. Moreover, we use a non-rectangular subset, which can reduce the influence of plastic deformation and crack width on the DIC measurement accuracy. We measured the SIF of a mode I crack in a super-hard aluminium alloy specimen to verify the performance of the proposed method. Our experimental results show that a DIC with a specific shape function can be used to accurately and efficiently calculate the SIF. Furthermore, we also present a practical application of our proposed method for determining the SIF, crack propagation angle and crack tip displacement.

A double photodiode (PD) constructed by p⁺/N-well junction and N-well/p-sub junction was designed and fabricated in a UMC 0.18-μm CMOS process. Based on the device structure and mechanism of double PD, a novel small-signal equivalent circuit model considering the carrier transit effect and the parasitic RC time constant was presented. By this model with complete electronic components, the double PD can be incorporated in a commercial circuit simulator. The component values were extracted by fitting the measured S-parameters using simulated annealing algorithm, and a good agreement between the measurement and the simulation results was achieved.

A 0.18 µm CMOS low noise amplifier (LNA) by utilizing noise-canceling technique was designed and implemented in this paper. Current-reuse and self-bias techniques were used in the first stage to achieve input matching and reduce power consumption. The core size of the proposed CMOS LNA circuit without inductor was only 128 µm × 226 µm. The measured power gain and noise figure of the proposed LNA were 20.6 and 1.9 dB, respectively. The 3-dB bandwidth covers frequency from 0.1 to 1.2 GHz. When the chip was operated at a supply voltage of 1.8 V, it consumed 25.69 mW. The high performance of the proposed LNA makes it suitable for multi-standard low-cost receiver front-ends within the above frequency range.

A structured low-rank matrix recovery model for RGBD salient object detection is proposed. Firstly, the problem is described by a low-rank matrix recovery, and the hierarchical structure of RGB image is added to the sparsity term. Secondly, the depth information is fused into the model by a Laplacian regularization term to ensure that the image regions which share similar depth value will be allocated to similar saliency value. Thirdly, a variation of alternating direction method is proposed to solve the proposed model. Finally, both quantitative and qualitative experimental results on NLPR1000 and NJU400 show the advantage of the proposed RGBD salient object detection model.

Random phase masks play a key role in optical image encryption schemes based on double random phase technique. In this paper, a mixed chaotic method is proposed, which can efficiently solve some weaknesses that one-dimensional (1-D) single chaotic maps encounter to generate random phase masks. Based on the chaotic random phase masks, optical image encryption and decryption are realized with a single-shot digital holographic technique. In the proposed encryption scheme, the initial value and parameters of mixed chaotic maps serve as secret keys, which is convenient for the key management and transmission. Moreover, it also possesses high resistance against statistical attack, brute-force attack, noise attack and shear attack. Simulation results and security analysis verify the validity and security of the proposed encryption scheme.

This paper proposes a novel registration method for augmented reality (AR) systems based on Oriented FAST and Rotated BRIEF (ORB) and Fast Retina Keypoint (FREAK) natural features. In the proposed ORB-FREAK method, feature extraction is implemented based on the combination of ORB and FREAK, and the feature points are matched using Hamming distance. To get good matching points, cross-checks and least median squares are used to perform outlier filtration, and camera pose is estimated using the matched points. Finally, AR is rendered. Experiments show that the proposed method improves the speed of registration to be in real time; the proposed method can accurately register the target object under the circumstances of partial occlusion of the object; and it also can overcome the effects of rotation, scale change, ambient light and distance.