In this article, we focus on solving a distributed convex optimization problem in a network, where each agent has its own convex cost function and the goal is to minimize the sum of the agents' cost ...functions while obeying the network connectivity structure. In order to minimize the sum of the cost functions, we consider new distributed gradient-based methods where each node maintains two estimates, namely an estimate of the optimal decision variable and an estimate of the gradient for the average of the agents' objective functions. From the viewpoint of an agent, the information about the gradients is pushed to the neighbors, whereas the information about the decision variable is pulled from the neighbors, hence giving the name "push-pull gradient methods." The methods utilize two different graphs for the information exchange among agents and, as such, unify the algorithms with different types of distributed architecture, including decentralized (peer to peer), centralized (master-slave), and semicentralized (leader-follower) architectures. We show that the proposed algorithms and their many variants converge linearly for strongly convex and smooth objective functions over a network (possibly with unidirectional data links) in both synchronous and asynchronous random-gossip settings. In particular, under the random-gossip setting, "push-pull" is the first class of algorithms for distributed optimization over directed graphs. Moreover, we numerically evaluate our proposed algorithms in both scenarios, and show that they outperform other existing linearly convergent schemes, especially for ill-conditioned problems and networks that are not well balanced.
An LCL-type filter is widely used in the grid-connected inverter. However, with only injected grid current control, the current harmonics and low bandwidth caused by the resonance peak cannot be ...tolerated. The active damping (AD) method with an extra feedback provides a high rejection of the resonance so that the dynamic is improved; however, the high-precision sensing circuit for the extra feedback increases the cost. In this paper, with the signal flow graph and response-fitting methods, an AD method based on the feedback of the injected grid current has been proposed. Then, the novel closed-loop current control requires accurately sensing the injected grid current only, while no observation is needed. Compared with the extra feedback methods, the cost and the complexity are reduced while the reliability is improved. Based on the study of the relation between the controller and the system dynamic, a straightforward design has been proposed. The robustness, harmonic rejection, and digital implementation have been studied. Compared with the conventional control methods, the proposed one promises the satisfactory performance with both analog and digital implementations. Simulations and experiments have verified the proposed control and design strategies.
We consider distributed optimization problems in which a number of agents are to seek the global optimum of a sum of cost functions through only local information sharing. In this paper, we are ...particularly interested in scenarios, where agents are operating asynchronously over stochastic networks subject to random failures. Most existing algorithms require coordinated and decaying stepsizes to ensure zero gap between the estimated value of each agent and the exact optimum, restricting it from asynchronous implementation and resulting in slower convergence results. To deal with this issue, we develop a new asynchronous distributed gradient method (AsynDGM) based on consensus theory. The proposed algorithm not only allows for asynchronous implementation in a completely distributed manner but also, most importantly, is able to seek the exact optimum even with constant stepsizes. We will show that the assumption of boundedness of gradients, which is widely used in the literature, can be dropped by instead imposing the standard Lipschitz continuity condition on gradients. Moreover, we derive an upper bound of stepsize within which the proposed AsynDGM can achieve a linear convergence rate for strongly convex functions with Lipschitz gradients. A canonical example of sensor fusion problems is provided to illustrate the effectiveness of the proposed algorithm.
The performance of the grid-connected inverter was affected by the uncertainty of the grid conditions including the background distortion and the grid impedance. Typically, the feedforward of the ...grid voltage at the point of common coupling (PCC) highly suppressed the grid current harmonics caused by the grid voltage distortion; however, the PCC grid usually had a nonnegligible grid impedance, and the PCC voltage feedforward aroused serious grid current harmonics or instability. This study proposes a novel adaptive algorithm for the PCC voltage feedforward to work well with the varied grid impedance. In the proposal, the band-pass filters at the harmonic frequencies are used to detect the variation of the grid impedance as well as to facilitate the adaptive PCC voltage feedforward. It is not necessary to inject an additional harmonic to estimate the grid impedance. The basic principles as well as the realization and logic of the proposed algorithm are detailed, and some selected waveforms are provided to verify the superior performance. Compared with the typical robust design or adaptive control, the proposed algorithm does not have to sacrifice the dynamic or the harmonics rejection performance, or to use the on or offline grid impedance estimation.
The choline prolinate (ChPro) as a hydrogen bond acceptor and ethylene glycol (EG) as a hydrogen bond donor are both used to synthesize the deep eutectic solvents (DESs) ChPro-EG to capture CO2. The ...CO2 capacity of ChPro-EG is determined, and the nuclear magnetic resonance (NMR) and infrared (IR) spectrum are used to investigate the CO2 capture mechanism. The results indicate that CO2 reacts with both the amino group of Pro− anion and the hydroxyl group of EG, and the mechanism found in this work is different from that reported in the literature for the ChPro-EG DESs.
Pore structure is an important factor that affects both vapor adsorption and water absorption performances of the expanded perlite insulation mortar. This study aims to explore the change in the pore ...structure of the expanded perlite insulation mortar in heat-rain cycles and investigate the effects on capillary water absorption and vapor adsorption performances. The expanded perlite insulation mortar specimens was subjected to 160 heat-rain cyclic test, and the distribution characteristics of the pore structures of the specimens after different heat–rain cycles in vacuum saturated water absorption, capillary water absorption, and vapor adsorption processes were measured via nuclear magnetic resonance. According to the test results, the pores with a size of greater than 1 μm in the expanded perlite insulation mortar determined the variation in total pores. The pore size can be classified into different ranges according to the performance in capillary water absorption and vapor adsorption. The calculated results of the fractional dimension suggest that the structure variation rules of different types of pores can be characterized by the fractional dimension. The relationship between the macro-performance parameters and the micro-structure can be established by using the fractional dimension as the linkage to provide reference for the hydrothermal evaluation of the whole expanded perlite external thermal insulation composite system.
•The evolution of the pore structure of ETICS EP was measured by NMR.•The variation of adsorption and water absorption properties in aging process was analyzed.•The fractal dimension was used to characterize the pore structure of ETICS EP.
Zoledronic acid (ZA) is one of the most important and effective class of anti-resorptive drug available among bisphosphonate (BP), which could effectively reduce the risk of skeletal-related events, ...and lead to a treatment paradigm for patients with skeletal involvement from advanced cancers. However, the exact molecular mechanisms of its anticancer effects have only recently been identified. In this review, we elaborate the detail mechanisms of ZA through inhibiting osteoclasts and cancer cells, which include the inhibition of differentiation of osteoclasts via suppressing receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK) pathway, non-canonical Wnt/Ca2+/calmodulin dependent protein kinase II (CaMKII) pathway, and preventing of macrophage differentiation into osteoclasts, in addition, induction of apoptosis of osteoclasts through inhibiting farnesyl pyrophosphate synthase (FPPS)-mediated mevalonate pathway, and activation of reactive oxygen species (ROS)-induced pathway. Furthermore, ZA also inhibits cancer cells proliferation, viability, motility, invasion and angiogenesis; induces cancer cell apoptosis; reverts chemoresistance and stimulates immune response; and acts in synergy with other anti-cancer drugs. In addition, some new ways for delivering ZA against cancer is introduced. We hope this review will provide more information in support of future studies of ZA in the treatment of cancers and bone cancer metastasis.
Groundwater contaminated by Cr(VI) requires effective remediation to prevent adverse environmental impacts. The biodegradation of Cr(VI) has been documented for several decades, but little remains ...known about the removal fate of chromium, including the main species of reductase (sites) and functional genes involved in Cr(VI) reduction in mixed bacterial consortium. Cr(VI) reduction in this study was verified to be an enzyme-mediated process. Meanwhile, Cr(VI) reduction of different cell components demonstrated that the extracellular enzyme was the main active substance, and the distribution of Cr after experiment was quantified using mass balance calculation. Furthermore, the optimal pH for reduction was 8.0, with the reduction rate decreasing with increasing initial Cr(VI) concentrations. The co-existing oxyanions had little effect on Cr(VI) reduction, while the presence of other heavy metals had a relatively significant influence. The evolutionary behavior of microbial community structure and functional genes affected by Cr(VI) were also analyzed, which provided new insights on the underlying mechanisms involved in bioreduction in this study. These results generated new understanding of the reduction mechanisms on the Cr-relevant bacterial species and genes, which would be helpful in designing strategies for the bioremediation of Cr(VI) contaminated water.
Display omitted
•The main location of reductase and valence state changes of Cr during Cr(VI) reduction were investigated.•The distribution of Cr after experiment was quantified by mass-balance.•The evolution of microbial communities and genes was deciphered for reduction.
Display omitted
•Galangin has been demonstrated to be effective in the treatment of hepatocellular carcinoma.•Galangin prevents hepatocellular carcinoma through multiple anti-cancer mechanisms.•The ...anti-cancer effects of galangin mainly include anti-proliferation, induction of apoptosis and autophagy, inhibition of metastasis.•Moreover, it could protect normal cells and prevent the effects of genotoxic carcinogens.
Hepatocellular carcinoma (HCC) is one of the most common cancers and has a high mortality rate in less developed countries, especially in China. Galangin (GA), one of the most important and naturally active flavonoids, extracted primarily from the root of Alpinia officinarum Hance, has been demonstrated to be effective in the treatment of HCC. It is a substance with defensive actions and a broad range of biological properties, including inhibitory effects on bacteria, fungi, viruses, the control of hypertension and diabetes, and chemoprevention of several cancers. Experiments have shown that GA prevents HCC through multiple anti-cancer mechanisms, anti-genotoxic activity against environmental and dietary carcinogens; anti-proliferative effects through reversal of the Warburg effect in HCC; arrest of the cell cycle in the G0/G1 phase; induction of apoptosis via stimulation of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and the mitochondrial-dependent apoptosis pathway; induction of autophagy; and inhibition of angiogenesis, metastasis, and multidrug resistance (MDR). In addition, synergistic effects with other chemotherapy drugs have been demonstrated. Therefore, this review is focused on the anti−HCC mechanisms of GA.
This study aimed to compare the survival rates after lobectomy, segmentectomy, and wedge resection for the eighth edition of the tumor, node, metastasis classification for stage IA non-small cell ...lung cancer (NSCLC).
Patients who underwent lobectomy, segmentectomy, or wedge resection for stage IA NSCLC were identified from the Surveillance, Epidemiology, and End Results database. A Cox regression model and propensity-matched analysis were used. The overall survival (OS) rates and lung cancer-specific survival (LCSS) rates among the three groups were compared by tumor size.
A total of 16,819 patients met our criteria. Although the OS rate was better for lobectomy than for wedge resection, no statistical differences in the LCSS rate were identified among the three treatment groups of patients with tumors that were 1.0 cm or smaller. For tumors from 1.1 to 2.0 cm, lobectomy and segmentectomy showed no statistical differences in the LCSS rate, but both conferred better OS and LCSS rates than wedge resection. For tumors from 2.1 to 3.0 cm, the OS and LCSS rates were better for lobectomy than for segmentectomy or wedge resection, but similar for segmentectomy and wedge resection.
Lobectomy, segmentectomy, and wedge resection are comparable oncologic procedures for patients with stage IA NSCLC that is 1.0 cm or smaller. For tumors from 1.1 to 2.0 cm, lobectomy and segmentectomy could lead to equivalent survival rates but showed better survival rates than that observed with wedge resection. For tumors from 2.1 to 3.0 cm, lobectomy is still the standard surgical procedure; for patients who are unsuitable candidates for lobectomy, segmentectomy and wedge resection show similar survival rates.
PDF
