Protocol selection for second-order consensus against disturbance

Noticing that both the absolute and relative velocity protocols can solve the second-order consensus of multi-agent systems, this paper aims to investigate which of the above two protocols has better anti-disturbance capability, in which the anti-disturbance capability is measured by the L2 gain from the disturbance to the consensus error. More specifically, by the orthogonal transformation technique, the analytic expression of the L2 gain of the second-order multi-agent system with absolute velocity protocol is firstly derived, followed by the counterpart with relative velocity protocol. It is shown that both the L2 gains for absolute and relative velocity protocols are determined only by the minimum non-zero eigenvalue of Laplacian matrix and the tunable gains of the state and velocity. Then, we establish the graph conditions to tell which protocol has better anti-disturbance capability. Moreover, we propose a two-step scheme to improve the anti-disturbance capability of second-order multi-agent systems. Finally, simulations are given to illustrate the effectiveness of our findings

Characteristics of metals in the aerosols of Zhongshan Station, Antarctica

Instrumental neutron activation analysis(INAA) was applied to analyze the bulk, high-volume aerosol samples, collected at Zhongshan Station in the Eastern Antarctica, during 1998-2001, to study the chemical species. A graphical technique was applied to the INAA data. Results showed that Na, Cl, Mg, Ca, Sr, Br, I, Sr and Rb were marine elements while Al, Sc, Fe and Mn were crustal elements. Compared to marine and crustal elements, five elements(Se, Co, Sb, Zn, Cr) were highly abundant in the aerosols collected at Zhongshan station, which indicated that they might come from the petroleum burning, heating and equipment operation. The presence of pollutant elements suggested that human activities have affected the local environments in Antarctica

Seasonal variations of sulfur aerosols at Zhongshan Station, East Antarctica

Observations of atmospheric methane-sulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4 2−) from December 2010 to November 2011 at Zhongshan Station are presented in this paper. MSA and nss-SO4 2− average concentrations were 24.2 ± 37.9 ng·m-3 (0.5–158.3 ng·m-3 ) and 53.0 ± 82.6 ng·m-3 (not detected [n.d.]) – 395.4 ng·m-3 ), respectively. Strong seasonal variations of MSA and nss-SO4 2−, with maxima in austral summer and minima in winter, were examined. The high concentrations of sulfur compounds in December may be attributed the dimethyl sulfide (DMS) emissions from the marginal ice zone, when open water near the sampling site was important in impacting the sulfur species of January and February at Zhongshan Station. In austral winter, there was almost no phytoplanktonic activity in offshore waters, and atmospheric sulfur compounds likely had long-range transport sources

Prediction of eukaryotic protein subcellular multi- localisation with a combined KNN-SVM ensemble classifier

Proteins may exist in or shift among two or more different subcellular locations, and this phenomenon is closely related to biological function. It is challenging to deal with multiple locations during eukaryotic protein subcellular localisation prediction with routine methods; therefore, a reliable and automatic ensemble classifier for protein subcellular localisation is needed. We propose a new ensemble classifier combined with the KNN (K-nearest neighbour) and SVM (support vector machine) algorithms to predict the subcellular localisation of eukaryotic proteins from the GO (gene ontology) annotations. This method was developed by fusing basic individual classifiers through a voting system. The overall prediction accuracies thus obtained via the jackknife test and resubstitution test were 70.5 and 77.6% for eukaryotic proteins respectively, which are significantly higher than other methods presented in the previous studies and reveal that our strategy better predicts eukaryotic protein subcellular localisation

Study on low-heat synergistic chemical profile control and flooding technology in Bohai Oilfield

Introduction: Through the combination of hot water and chemical agent, the low-heat synergistic chemical profile control and flooding technology can not only reduce the risks of sand production and string damage caused by high-temperature thermal recovery technology, but also further improve the recovery factor on the basis of hot water flooding.Methods: Based on laboratory testing, the synergism mechanism of thermal energy and chemical agent is studied.Results: The research results showed that in the near wellbore zone of the injection well, crude oil viscosity reduction mainly relies on thermal energy, and chemical agents assist in improving the water oil mobility ratio and reducing the risk of cross flow. After entering the deep formation, due to the decrease in temperature, the thermal energy effect is weakened, but the chemical agents still aggregate at the oil-water interface and continue to act on heavy oil to reduce viscosity. The higher the temperature, the greater the role of heat energy, and the weaker the role of chemical agents. The higher the injection concentration of chemical agent, the more obvious the leading role of chemistry. Based on the comprehensive evaluation index, the optimized temperature is 80°C and the injection concentration is 1500 mg/L. The scheme study of Bohai L Oilfield shows that compared with cold water flooding, hot water flooding can only improve oil recovery by 1.2 percentage points, and low heat collaborative chemical profile control flooding technology can further improve oil recovery by 4.7 percentage points on the basis of hot water flooding, with obvious oil increase effect.Conclusion: It is suggested that Bohai L Oilfield should apply low-heat coordinated chemical profile control and flooding technology to improve the development effect of the oilfield, and provide new technical ideas for safe and economic development of offshore heavy oil

Chemical composition of marine aerosols of the 26th Chinese National Antarctic Research Expedition

The ionic compositions of aerosol samples collected during the 26th Chinese National Antarctic Research Expedition were analyzed and the sources of ions were distinguished. Cl(-), Na(+), SO(2-)4 , NO(-)3 , and Mg2+ were the most abundant ionic components in the marine aerosols. Cl¡ and Na+ contributed over 70% in the total ionic composition, indicating the sea salt is still the primary composition in marine aerosols, followed by the sulfate as the secondary ionic component existed as NH4NO3, NH4HSO4, (NH4)2SO4. The maximal sea salt concentrations were found at around 40±S and could be attributed to greater winds. The concentrations of methane sulfonic acid (MSA) appeared increasing trend from the low to high latitudes, possibly caused by lower temperature in air and higher marine biological processes in the marginal waters in Antarctica. The correlation and factor analyzes were used to investigate possible sources of these ions. Cl(-), Br(-), Na(+), K(+), Mg(2+) and Ca(2+) had predominantly marine sources; while F(-), NO(-)3 and NH(+)4 had mostly anthropogenic sources; MSA had marine biogenic sources. The concentrations of SO2¡ 4 were influenced by both marine and anthropogenic sources