To study the abnormal failure of magnesium anodes for buried pipelines in marine engineering in the unique environment of mudflats, a strain of a sulfate-reducing prokaryote (SRP) was isolated from pipe-laying soil, and identified as Desulfovibrio sp. HQM3. Weight-loss test, electrochemical measurements, SEM, EDS, XRD, and CLSM techniques were used to study the effect of corrosion on the AZ31B magnesium alloy. Under the influence of SRP, the magnesium alloy corroded severely at rates up to 1.31 mm/year in the mudflat environment. SRP accelerated corrosion by 0.3mm/year. Pitting occurred on the samples in both abiotic and biotic systems. The pitting depth reached 163.47 μm in the biotic system after 14 days. The main composition of a petal-like corrosion product was Mg(OH)2. The results show that a mudflat environment can lead to an accelerated corrosion of magnesium alloys.
Electricity metering is more and more widely used in social life, and the traditional mode of manual detection methods have a large number of shortcomings, which is difficult to meet people's needs for electricity consumption. In order to improve the level of intelligence and automation, this paper introduces the goal and significance of combining artificial intelligence technology and electric energy flow monitoring system to realize unattended management, analyzes and compares the advantages and disadvantages of several mainstream intelligent algorithms in power operation status monitoring, finally proposes a method to build an artificial grid load prediction model based on genetic algorithm, neural network and other computational models, and applies it to the traditional mode for simulation experimental research.
The problem of reconstructing a sparse signal vector from magnitude-only measurements (a.k.a., compressive phase retrieval), emerges naturally in diverse applications, but it is NP-hard in general. Building on recent advances in nonconvex optimization, this paper puts forth a new algorithm that is termed compressive reweighted amplitude flow and abbreviated as CRAF, for compressive phase retrieval. Specifically, CRAF operates in two stages. The first stage seeks a sparse initial guess via a new spectral procedure. In the second stage, CRAF implements a few hard thresholding based iterations using reweighted gradients. When there are sufficient measurements, CRAF provably recovers the underlying signal vector exactly with high probability under suitable conditions. Moreover, its sample complexity coincides with that of the state-of-the-art procedures. Finally, substantial simulated tests showcase remarkable performance of the new spectral initialization, as well as improved exact recovery relative to competing alternatives.
Large-scale unanchored vertical liquid storage tanks are being applied extensively,its dynamic parameters,such as the natural frequency and mode shape,are very often used in seismic engineering.The natural mode of 15×104m3 storage tank was analyzed by ADINA finite element technique using spring element to simulate foundation,and considering the liquid-structure interaction effect.The results show that: there is small difference between the finite element technique and the well-known code formula on mode analysis of tanks;the vibration forms of the low-frequency segment of 15×104m3 storage tank are various,among which cosnθ、sinnθ beam vibrations are the leading one,the vibration forms of the liquid are simple,namely cosnθ、sinnθ beam vibration;the frequencies of liquid-structure coupled vibration are sensitive to foundation stiffness,are followed by the liquid height and the ratio of tank height to radius,and are insensitive to the thickness of tank wall;sloshing frequencies of liquid are insensitive to foundation stiffness as well as the thickness of tank wall,and are sensitive to liquid height as well as the ratio of tank height to radius.
Although electric vehicles are considered a viable solution to reduce greenhouse gas emissions, their uncoordinated charging could have adverse effects on power system operation. Nevertheless, the task of optimal electric vehicle charging scales unfavorably with the fleet size and the number of control periods, especially when distribution grid limitations are enforced. To this end, vehicle charging is first tackled using the recently revived Frank-Wolfe method. The novel decentralized charging protocol has minimal computational requirements from vehicle controllers, enjoys provable acceleration over existing alternatives, enhances the security of the pricing mechanism against data attacks, and protects user privacy. To comply with voltage limits, a network-constrained EV charging problem is subsequently formulated. Leveraging a linearized model for unbalanced distribution grids, the goal is to minimize the power supply cost while respecting critical voltage regulation and substation capacity limitations. Optimizing variables across grid nodes is accomplished by exchanging information only between neighboring buses via the alternating direction method of multipliers. Numerical tests corroborate the optimality and efficiency of the novel schemes.
To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of computational fluid dynamics, and eight cases with pantographs fixed on different positions and in different operational orientations were considered. The pantographs were fixed on the front or the rear end of the first middle car or fixed on the front or the rear end of the last middle car. The external flow fields of the high-speed trains were numerically simulated using the software STAR-CCM+. The results show that the pantograph fixing position has little effect on the aerodynamic drag force of the head car and has a large effect on the aerodynamic drag force of the tail car. The influences of the pantograph fixing position on the aerodynamic lift forces of the head car, tail car and pantographs are obvious. Among the eight cases, considering the total aerodynamic drag force of the train and the aerodynamic lift force of the lifted pantograph, when the pantographs are fixed on the rear end of the last middle car and the lifted pantograph is in the knuckle-upstream orientation, the aerodynamic performance of the high-speed train is the best.
Time-varying renewable energy generation can result in serious under-/over-voltage conditions in future distribution grids. Augmenting conventional utility-owned voltage regulating equipment with the reactive power capabilities of distributed generation units is a viable solution. Local control options attaining global voltage regulation optimality at fast convergence rates is the goal here. In this context, novel reactive power control rules are analyzed under a unifying linearized grid model. For single-phase grids, our proximal gradient scheme has computational complexity comparable to that of the rule suggested by the IEEE 1547.8 standard, but it enjoys well-characterized convergence guarantees. Adding memory to the scheme results in accelerated convergence. For three-phase grids, it is shown that reactive injections have a counter-intuitive effect on bus voltage magnitudes across phases. Nevertheless, when our control scheme is applied to unbalanced conditions, it is shown to reach an equilibrium point. Yet this point may not correspond to the minimizer of a voltage regulation problem. Numerical tests using the IEEE 13-bus, the IEEE 123-bus, and a Southern California Edison 47-bus feeder with increased renewable penetration verify the convergence properties of the schemes and their resiliency to grid topology reconfigurations.
Objective
To analyze the dosimetric effect of inconsistent bladder filling states between the CT simulation and treatment for prostate cancer patients undergoing intensity-modulated radiotherapy (IMRT).
Methods
A total of 42 prostate cancer patients treated with IMRT were selected. After vacuum pad immobilization and simulation CT scan, the delineation of targets and organs-at-risk (OARs), treatment planning and dose calculation were performed on treatment planning system (TPS). The cone-beam-CT (CBCT) acquired before the first treatment was registered to planning CT, on which the target contours were duplicated and OARs were delineated. After dose recalculation on the CBCT using the same plan, the dosimetric differences on the CT and CBCT were compared, including mean dose of the planning target volume (PTV), homogeneity index (HI), conformity index (CI); the mean dose, V30, V40, V50, V60, and V65 of bladder and rectum respectively.
Results
Relative to the bladder volumes at simulation, the patients were divided into two groups with larger (15 cases) or smaller (27 cases) bladders at the first treatment. Comparing the parameters obtained from simulation CT with that from CBCT, the differences of the following parameters were of statistical significance: the bladder volume, PTV HI, PTV CI in both groups (t=6.838, -4.372, -3.553, -3.462, 6.380, 5.037, P<0.05), the bladder V30, V40, V50, V60, V65 (t=-5.004, -4.092, -3.124, -2.707, -2.489, P <0.05) and rectal V40, V50, V60, V65, mean dose in the group with smaller bladders (t=-2.946, -2.643, -2.426, -3.127, -2.530, P <0.05), and the bladder V30, V40, V50 and mean dose in group with larger bladders (t=5.107, 4.204, 3.777, 4.155, P<0.05).
Conclusions
For prostate cancer patients undergoing IMRT, the inconsistent bladder filling states between the planning and treatment will cause disimetric differences of targets and OARs.
Key words:
Bladder volume; Prostate cancer; CBCT; Dosimetric parameters
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