The further identification of fault types for single line-to-ground faults (SLGFs) in distribution networks is conducive to determining the cause of grounding faults and formulating targeted measures ...for hidden danger treatment and fault prevention. For the six types of SLGFs generated in the actual power grid, this paper deeply studies their fault characteristics. Firstly, the classification criterion of fault transition resistance is derived by the generation mechanism of fault zero sequence voltage (ZSV). At the same time, by comparing and analyzing the same and different characteristics between faults, three criteria for fault classification are obtained. Based on the above four criteria, a multilevel and multicriteria fault classification method is proposed to judge six types of SLGFs. Then, the proposed method is verified by various fault state simulations of the distribution network model with a balanced topology and unbalanced topology. The engineering application of the method is demonstrated by the verification of actual power grid data. Finally, noise and data loss interference test results show the robustness of the method.
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During the last decade, the deluge of multimedia data has impacted a wide range of research areas, including multimedia retrieval, 3D tracking, database management, data mining, machine learning, ...social media analysis, medical imaging, and so on. Machine learning is largely involved in multimedia applications of building models for classification and regression tasks, etc., and the learning principle consists in designing the models based on the information contained in the multimedia dataset. While many paradigms exist and are widely used in the context of machine learning, most of them suffer from the ‘curse of dimensionality’, which means that some strange phenomena appears when data are represented in a high-dimensional space. Given the high dimensionality and the high complexity of multimedia data, it is important to investigate new machine learning algorithms to facilitate multimedia data analysis. To deal with the impact of high dimensionality, an intuitive way is to reduce the dimensionality. On the other hand, some researchers devoted themselves to designing some effective learning schemes for high-dimensional data. In this survey, we cover feature transformation, feature selection and feature encoding, three approaches fighting the consequences of the curse of dimensionality. Next, we briefly introduce some recent progress of effective learning algorithms. Finally, promising future trends on multimedia learning are envisaged.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In order to make the grid-connected composite device (GCCD) controller meet the requirements of different operating modes and complex working conditions of power grid, this paper proposes to ...introduce sliding mode control (SMC) into GCCD controller. Firstly, the mathematical model of MMC converter is established, and the sliding mode controller is designed based on the SMC principle. Then, aiming at the problems of complex controller structure and difficult parameter tuning in multiple modes of the GCCD, this paper proposes a controller parameter optimization method based on improved Month Flame optimization (IMFO) algorithm. This method improves the
algorithm by introducing good point set (GPS) initialization and Levy flight strategy, which accelerates the convergence speed of the algorithm while avoiding falling into local optimization, and realizes the optimization of converter controller parameters. Under a variety of standard test functions, the advantages of the proposed IMFO algorithm are verified by comparing it with the traditional algorithm. Finally, in order to realize the automatic tuning of control parameters, the Python-PSCAD joint simulation method is studied and implemented. Taking the comprehensive integral of time and absolute error (
) index as the objective function, the parameters of the sliding mode controller are optimized. The simulation results show that the controller parameters optimized by the IMFO algorithm can make the GCCD have better dynamic performance.
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The Gongguan deposit in southern Qinling district, central China, is characterized by a Hg and Sb metal association, with proven reserves of 7,543 t Hg and 17,100 t Sb. The Hg-Sb mineralized veins ...are primarily hosted by local Lower Devonian dolomite. Three primary paragenetic stages have been identified, including (I) pyrite-dolomite-quartz, (II) stibnite-cinnabar-quartz-calcite and (III) post-ore calcite. Dominant mercury and antimony mineralization occurred in stage II. Fluid inclusion microthermometry of quartz and calcite reveal that the Hg-Sb mineralization is associated with a low temperature (142° to 240 °C) and low salinity (< 8.6 wt% NaCl equivalent) fluid, belonging to a H
2
O-NaCl ± CO
2
system. The H–O isotope compositions (
δ
D
H2O
= −84 to −63‰,
δ
18
O
H2O
= 1.3 to 12.7‰) of the hydrothermal fluid suggest a mixture of metamorphic fluid and meteoric water. In situ sulfur isotope results of cinnabar (
δ
34
S = 3.4 to 14.5‰), stibnite (
δ
34
S = 4.9 to 10.5‰) and pyrite (
δ
34
S = 3.8 to 5.4‰) indicate sulfur sources from decomposition of diagenetic pyrite and/or the thermochemical sulfate reduction in local sedimentary rocks. In situ obtained
206
Pb/
204
Pb,
207
Pb/
204
Pb and
208
Pb/
204
Pb ratios (18.006 to 18.362, 15.445 to 15.610 and 37.871 to 38.288, respectively) of stibnite and pyrite substantially differ from those for the regional Carlin Au-Sb and SEDEX Pb–Zn ore deposits. The lead isotope results indicate that the underlying Paleozoic (Silurian to Cambrian) strata and Precambrian metamorphic basement supplied substantial metals for the studied Hg-Sb deposit, whereas the host Devonian carbonates did not contribute significant metals. In summary, we propose that fluid mixing between metamorphic fluid and meteoric water was the main cause for carbonate-hosted Hg-Sb deposition at Gongguan, which reduced the stibnite solubility, oxidized mercury (Hg
0
to Hg
2+
), favoring the process of dedolomitization.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Information on the clinical staging of coronavirus disease 2019 (COVID-19) is still limited. This study aimed to propose a clinical staging proposal of the disease course in non-severe ...patients with COVID-19. In this retrospective study, 108 non-severe patients with COVID-19 were grouped according to the duration from symptoms onset to hospital admission: ≤ 1 week, > 1 to 2 weeks, > 2 to 3 weeks, > 3 to 5 weeks, respectively. The dynamic changes of clinical signs were profiled across the four groups. A clinical staging proposal of the disease course over time was proposed from the perspective of the interaction between the virus and host. The prodromal phase, characterized by pneumonia, significant lymphopenia, and slightly elevated inflammatory markers, occurred in the first week after symptoms onset. In the second week, all the hematological and inflammatory markers were at the peak or bottom. Meanwhile, progressive pneumonia as well as the secondary damage of other organs (e.g. cardiac damage, coagulopathy, etc.) was significant during this period, making the disease progress into the apparent manifestation phase. In the third week, the improvement of the majority of clinical signs accompanied by a relatively high degree of inflammatory response defined the remission phase. After 3 weeks, patients were in the convalescent phase, in which all the indicators were maintained at a relatively normal level. We concluded that the disease course over time in non-severe patients with COVID-19 could be divided into four phases: the prodromal phase (in the first week), the apparent manifestation phase (in the second week), the remission phase (in the third week), and the convalescent phase (after 3 weeks), respectively. In clinical practice, tailored therapies should be considered seriously in different stages of the disease course.
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Compared with traditional EDM, ultrasonic vibration assisted EDM (UEDM) shows better performance in machining efficiency and surface quality. However, the material removal process of UEDM is complex, ...and there are many influencing factors. It is difficult to describe the material removal process accurately. In this study, based on the voltage variation during UEDM processing and combined with the heat transfer theory, the material removal model of TC4 titanium alloy under the condition of single pulse vertical UEDM is established. The material removal process of UEDM under different amplitudes is analyzed. The machining efficiency and surface quality of UEDM with different amplitude of ultrasonic vibration under the condition of vertical ultrasonic vibration are verified by UEDM experiments. The best material removal rate (MRR) can be obtained by adjusting the current and ultrasonic amplitude, which can improve the efficiency of UEDM.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Multi-Point Relay (MPR) is one of the core technologies for Optimizing Link State Routing (OLSR) protocols, offering significant advantages in reducing network overhead, enhancing throughput, ...maintaining network scalability, and adaptability. However, due to the restriction that only MPR nodes can forward control messages in the network, the current evaluation criteria for selecting MPR nodes are relatively limited, making it challenging to flexibly choose MPR nodes based on current link states in dynamic networks. Therefore, the selection of MPR nodes is crucial in dynamic networks. To address issues such as unstable links, poor transmission accuracy, and lack of real-time performance caused by mobility in dynamic networks, we propose a comprehensive evaluation algorithm of MPR based on link-state awareness. This algorithm defines five state evaluation parameters from the perspectives of node mobility and load. Subsequently, we use the entropy weight method to determine weight coefficients and employing the method of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) for comprehensive evaluation to select MPR nodes. Finally, the Comprehensive Evaluation based on Link-state awareness of OLSR (CEL-OLSR) protocol is proposed, and simulated experiments are conducted using NS-3. The results indicate that, compared to PM-OLSR, ML-OLSR, LD-OLSR, and OLSR, CEL-OLSR significantly improves network performance in terms of packet delivery rate, average end-to-end delay, network throughput, and control overhead.
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Evaluating the risk exposure of a financial/insurance company when some extreme scenario occurs is one of the fundamental aspects of risk management. Well-known tail risk measures, such as the ...Conditional Tail Expectation and the Marginal Expected Shortfall, are used for measuring a massive downside in adverse scenarios. Most of these risk measures are based on the conditional expectation of a specific loss function, subject to the assumption of an extreme loss event. In this paper, we study the loss-based tail risk measures under the condition that an extreme loss event has occurred. Asymptotic approximations are derived under a regularly varying loss function for individual and multivariate heavy-tailed risks. Some further examples with applications are given to show how our asymptotic approximations can be used to approximate many other loss-based tail risk measures.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Shangdan district in the North Qinling Orogenic Belt hosts the largest pegmatite-type uraniferous province in China. The Xiaohuacha U mineralization in this district occurs along the contact zone ...between biotite pegmatite and its host rock of biotite gneiss, adjacent to the composite Huichizi batholith, which is composed mainly of biotite monzogranite and syenogranite. Zircon UPb dating of these granitoids reveals two-stage magmatism, namely, the early Silurian for biotite monzogranite (438.5 ± 4.4 Ma) and the early Devonian for syenogranite (417.8 ± 3.2 Ma). The biotite pegmatite shows an age of 415.8 ± 3.8 Ma for the mineralized marginal zone, and similar ages of 414.6 ± 4.3 Ma and 413.2 ± 3.5 Ma are obtained for the barren marginal and intermediate zones, respectively.
The biotite monzogranite exhibits a restricted range of positive zircon εHf(t) values of +5.3 to +7.8, with TDM2 ages of 0.93–1.08 Ga, suggesting magma derivation from mainly pre-existing basaltic rocks in the orogenic root. Magmatic oxygen fugacity (fO2) was estimated by Ti-in-zircon thermometry and Ce incorporation within zircons. The biotite monzogranite was emplaced at a temperature of 736 ± 24 °C with log fO2 values of −22.28 to −14.19. In contrast, the syenogranite zircons have εHf(t) values of −1.4 to +2.4 and TDM2 ages of 1.25–1.49 Ga, indicating a derivation from the Mesoproterozoic crust with some mantle input. Pristine zircon domains from different zones of the biotite pegmatite display εHf(t) values of −2.8 to +1.8 and TDM2 ages of 1.29–1.58 Ga, similar to those of the syenogranite, indicating they share a common magma source. Combination of petrographical, geochronological, isotopic, and mineral chemical data supports a petrogenetic relationship between the high-T (842 ± 14 °C) syenogranite and biotite pegmatite (756 ± 21 °C and 709 ± 26 °C for the uncontaminated marginal and intermediate zones respectively) through magmatic differentiation from the same magma source during a period of tectonic extension.
Processes of segregation and emplacement of the pegmatitic magma are consistent with open-system assimilation and fractional crystallization (AFC) leading to decreasing log fO2 values from the syenogranite (−11.23 to −7.02) to biotite pegmatite through a fractionation trajectory. However, log fO2 values increase from the uncontaminated pegmatite marginal (−15.88 to −10.9) to intermediate (−17.86 to −6.14) zones with closed-system pegmatite internal evolution. The interaction (hybridization) between magma and gneiss induced decrease of oxidation state and (K + Na)/Al, as well as modifications to zircon compositions in the mineralized pegmatite marginal zone. We propose a model with decreasing of fO2 and (K + Na)/Al during AFC being the main controls on the formation of the U deposit.
•Early Silurian and early Devonian granitoids occur in the Shangdan uraniferous province.•Ore-forming pegmatitic magma is derived from a high Si and K granitic source.•Decrease of fO2 and (K + Na)/Al during magma AFC process are key U metallogenic factors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flexible endoscopy requires a lot of skill to manipulate both the endoscope and the associated instruments. In most robotic flexible endoscopic systems, the endoscope and instruments are controlled ...separately by two operators, which may result in communication errors and inefficient operation. Our solution is to enable the surgeon to control both the endoscope and the instruments. Here, we present a novel tele-operation robotic endoscopic system commanded by one operator using the continuous and simultaneous movements of their two hands and one foot. This 13-degree-of-freedom (DoF) system integrates a foot-controlled robotic flexible endoscope and two hand-controlled robotic endoscopic instruments, a robotic grasper and a robotic cauterizing hook. A dedicated foot-interface transfers the natural foot movements to the 4-DoF movements of the endoscope while two other commercial hand interfaces map the movements of the two hands to the two instruments individually. An
ex-vivo
experiment was carried out by six subjects without surgical experience, where the simultaneous control with foot and hands was compared with a sequential clutch-based hand control. The participants could successfully teleoperate the endoscope and the two instruments to cut the tissues at scattered target areas in a porcine stomach. Foot control yielded 43.7% faster task completion and required less mental effort as compared to the clutch-based hand control scheme, which proves the concept of three-limb tele-operation surgery and the developed flexible endoscopic system.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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