With the increasing proportion of wind power connected to grid, power system dispatching is facing more and more challenges from uncertainty. To cope with this uncertainty, robust optimization has ...been applied in unit commitment (UC) problem. In this paper, a multi-band uncertainty set considering the temporal correlation (MBUSCTC) of wind/load prediction error is proposed firstly, which has two characteristics: (1) The MBUSCTC rigorously and realistically reflect the distribution characteristics of uncertainties in uncertainty intervals, thereby effectively reducing the conservatism of the traditional singe-band uncertainty set; (2) the temporal correlation constraints of wind power/load prediction errors in MBUSCTC could limit the realization of uncertainties fluctuating frequently in uncertain intervals, thereby eliminating scenarios with lower probability in uncertainty sets. Then the proposed MBUSCTC is applied to UC problem, leading a robust UC model based on MBUSCTC, which is solved by Benders decomposition method and C&CG method. Finally, case studies based on the modified IEEE-118 bus system and an actual power system of China demonstrate that the proposed method can effectively reduce the conservativeness of the robust UC model and ensure the robustness of the unit commitment solution.
Background
This systematic review and meta-analysis aimed to investigate local recurrence (LR) rates among the three grades (benign, borderline, and malignant) of phyllodes tumors (PTs). The study ...also assessed various risk factors for LR.
Methods
Electronic articles published between 1 January 1995 and 31 May 2018, were searched and critically appraised. The authors independently reviewed the abstracts and extracted data for LR rates and LR risk factors.
Results
The review incorporated 54 studies with 9234 individual cases. The pooled LR rates were 8% for benign, 13% for borderline, and 18% for malignant PTs. The risk of LR was significantly increased by borderline versus benign PTs (odds ratio OR 2.00; 95% confidence interval CI 1.68–2.38) and malignant versus borderline PTs (OR 1.28; 95% CI 1.05–1.55). The significant risk factors for LR were mitoses, tumor border (infiltrating vs. pushing), stromal cellularity (moderate/severe vs. mild), stromal atypia (severe vs. mild/absent), stromal overgrowth (severe vs. mild/absent), and tumor necrosis (positive vs. negative). Age and tumor size were not associated with LR risk. The subgroup analysis showed that breast-conserving surgery versus mastectomy and positive versus negative surgical margins were significantly associated with an increased LR risk only in malignant PTs.
Conclusions
The risk of LR was significantly increased from benign to borderline to malignant PTs. Mitoses, tumor border, stromal cellularity, stromal atypia, stromal overgrowth, tumor necrosis, type of surgery, and surgical margin status may be risk factors for LR. Different management strategies could be considered for different PT grades.
In this paper, a robust state estimator based on maximum exponential absolute value (MEAV) is proposed by using the maximum correntropy criterion with Laplace kernel function as the objective ...function of state estimation. Since the objective function of MEAV model is continuous but nondifferentiable, its equivalent model is given, which is then solved based on the primal-dual interior point method. To further improve the computational efficiency, a new correction equation with much lower order is presented and the number of fill-ins in the solving process is reduced by a systematic method. Simulations based on the IEEE benchmark systems and two real grids of China demonstrate that the proposed MEAV estimator is very robust with high efficiency.
Works by Celik and Abur suggest a weighted least absolute value state estimation with transformations (WLAV-T) for attaining insensitiveness of state estimation (SE) to bad measurements by mitigating ...the effect of leverage points. To further improve its applicability, this letter proposes a systematic approach to compute the optimal rotation angles and scaling factors of the WLAV-T, deriving a robust WLAV estimation approach with optimal transformations (WLAV-OT). The proposed approach has been preliminarily tested with promising results.
Wetting behavior between hot metal and carbon brick is the first step to explore the erosion of carbon brick. In order to investigate the wetting behavior, wetting experiments between hot metal (with ...carbon content 2.87, 3.47, 4.12, 4.51, and 4.96 mass%) and carbon brick were carried out. The wetting angle under different conditions was measured, the reaction interface morphology and carbon structure were analyzed, the mechanism of hot metal wetting carbon brick was clarified based on interfacial energy and scaling law. The results show that: The wetting angle decreased gradually with the increase of wetting time for all initial carbon content experiments, the wetting angle increased with the increase of initial carbon content in hot metal. The dissolution of carbon occurred during the wetting process, which left a concave on carbon brick. The graphitization degree of carbon in carbon brick increased after the wetting behavior. In the initial stage of the wetting reaction, the change of interfacial energy caused by carbon dissolution reaction was the essential reason for the change of wetting angle. In the final stage of the wetting reaction, the wetting angle mainly depended on the concave shape after the concave was formed. The wetting model was established to explore the wetting behavior with dissolution reaction, the scaling relationship between the spreading radius of iron drop and time was obtained, which was convenient to evaluate the wetting behavior between hot metal and carbon brick.
The dissolutive wetting between hot metal and carbon brick is a complex problem from the viewpoint of carbon brick erosion. The current work aims to clarify the mechanism of dissolutive wetting at ...the interface between hot metal and carbon brick. The interfacial morphology is analyzed using SEM and EDS, and the change in wetting angle is studied using CCD camera and ImageJ software. Also, the interface shape model is established, the coupling control mechanism of dissolution and wetting is explored. The results reveal that the concave-like interface is formed after dissolutive wetting and the concave depth decreases with the increase of carbon content in hot metal. Moreover, a large amount of graphite flakes appear at the interface between hot metal and carbon brick after dissolutive wetting. The upper wetting angle initially exhibits a rapid decrease with time, followed by a gradual decrease. The lower wetting angle increases with time. The overall wetting angle initially decreases with time, followed by a stable trend. Hence, the dissolutive wetting can be divided into two stages.
Furthermore, the interface shape model is established based on the scaling law and Noyes-Whitney equation to describe the dissolutive wetting. The variation of interface shape can be obtained by the interface shape model. The governing equation is obtained through the Onsager principle to clarify the coupling control mechanism of dissolutive wetting. Finally, wetting is determined by the relative situation of interfacial energy and dissolution free energy. The liquid structure of hot metal is changed due to the migration of carbon atoms from carbon brick to hot metal during dissolutive wetting, altering the free energy and facilitating the transition from the first stage to the second stage.
This study characterized the pollution levels and potential ecological risk of heavy metals in combined sewer overflows (CSOs) and their effects on microbial diversity in nearby riparian sediments. ...The chemical fractionations of Zn, Cd, Cr, and Cu in dry-weather flows, wet-weather flows (CSO discharges), sewer sediments, and surface runoffs were determined. Geo-accumulation (Igeo) and ecological risk (RI) indexes were employed for metal risk assessment. DNA extraction and polymerase chain reaction (PCR) amplification on the Illumina MiSeq platform were conducted. The results show that heavy metals contents in fine-sized fractions have higher values than those in coarse-sized fractions. Chemical fractionation analysis suggests that Zn and Cd are two of the most bioavailable metals impacted by anthropogenic activities. Cr and Cu contents in CSOs are relatively stable and could exist for extended periods. According to the RI analysis, CSOs pose a considerable risk (RI-G2) to receiving waters due to the higher bioavailability of Cd, which was consistent with the Igeo index. Furthermore, under the stress of the highly-bioavailable Cd and Cu, Gram +ves in the riparian benthic sediment gradually became dominant with metal-tolerance property. Therefore, long-term exposure to highly bioavailable metals could exhibit great impacts on microbial diversity.
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•The influence of heavy metals in CSOs on microbial diversity was investigated.•Potential ecological risk generated by particulate metals in CSOs was assessed.•Particulate Cd in CSOs poses a considerable risk to receiving waters.•Highly bioavailable Cd and Cu promotes Gram +ves in the benthic riparian sediment.
Transient stability and short-term voltage stability have successively attracted the attention of electric power industry. This paper proposes a novel systematic approach for dynamic VAR planning to ...improve short-term voltage stability level and transient stability level. The dynamic VAR planning problem is formulated as a multi-objective optimization (MOO) model with objectives including investment cost, short-term voltage stability level, and transient stability level. To reduce the complexity of the proposed MOO model, K-means clustering-based severe contingencies selection and global sensitivity analysis-based potential buses selection are employed, leading to a simplified MOO model. The combination of a surrogate modeling technique called support vector regression and the multi-objective evolutionary algorithm (MOEA) are then used to solve the simplified MOO model, considering both the accuracy of models and the optimization computation cost. This combination makes it feasible to perform multiple runs of MOEAs for weakening the effect of the MOEA's randomness to optimal results and offering more diverse Pareto-optimal solutions for decision makers. Simulations are carried on the IEEE 39-bus system and a real power grid of China, illustrating that our methodology is reliable with high efficiency.
The three-dimensional architecture of the genome affects genomic functions. Multiple genome architectures at different length scales, including chromatin loops, domains, compartments, and lamina- and ...nucleolus-associated regions, have been discovered. However, how these structures are arranged in the same cell and how they are mutually correlated in different cell types in mammalian tissue are largely unknown. Here, we develop Multiplexed Imaging of Nucleome Architectures that measures multiscale chromatin folding, copy numbers of numerous RNA species, and associations of numerous genomic regions with nuclear lamina, nucleoli and surface of chromosomes in the same, single cells. We apply this method in mouse fetal liver, and identify de novo cell-type-specific chromatin architectures associated with gene expression, as well as cell-type-independent principles of chromatin organization. Polymer simulation shows that both intra-chromosomal self-associating interactions and extra-chromosomal interactions are necessary to establish the observed organization. Our results illustrate a multi-faceted picture and physical principles of chromatin organization.
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