Real-Time Model of a Large-scale Water Distribution System

AbstractThis paper presents a real-time WDS hydraulic model combining with field measurements provided by supervisory control and data acquisition systems (SCADA). The system is composed of three parts, namely SCADA, state estimation server and client terminal. For the real-time demand estimation, a weighted least-squares scheme based recursive state estimator and local linear matrix transform algorithm are applied. The WDS model system is applied in Guangzhou city, which is one of the largest cities in China, and proves that the proposed nodal demand correction algorithms are effective for real-time WDS model

Heavy cycles in k-connected weighted graphs with large weighted degree sums

AbstractA weighted graph is one in which every edge e is assigned a nonnegative number w(e), called the weight of e. The weight of a cycle is defined as the sum of the weights of its edges. The weighted degree of a vertex is the sum of the weights of the edges incident with it. In this paper, we prove that: Let G be a k-connected weighted graph with k⩾2. Then G contains either a Hamilton cycle or a cycle of weight at least 2m/(k+1), if G satisfies the following conditions: (1) The weighted degree sum of any k+1 pairwise nonadjacent vertices is at least m; (2) In each induced claw and each induced modified claw of G, all edges have the same weight. This generalizes an early result of Enomoto et al. on the existence of heavy cycles in k-connected weighted graphs

The Paperelectrophoresis of serum protein in pregnancy

1. Using paper electrophoresis, the normal value of each fraction of serum protein was estimated in 10 nonpregnant normal Taiwanese women. 2. The paper electrophoresis of serum protein in each group of 10 pregnant women in each pregnancy month totalling 90 women, showed a progressive decrease of plasma protein and albumin and an increase of α-and β-globulin as the pregnancy advanced. 3. 11 cases of ectopic gestation, 6 cases of hydatidiform mole, 6 cases of abruptio placentae, 5 cases of eclampsia, 11 cases of preeclampsia and 4 cases of choriocarcinoma were studied in comparison with the normal pregnant women. It was noted that the change of the serum protein was proportional to the severity of toxemia of pregnancy. 4. With paper electrophoresis of serum protein, afibrinoganemia in abruptio placentae cases was easily detected, thus making a great contribution to the diagnosis and treatment of this clinical entity. 5. The figures of paper electrophoresis of the intraabdominal blood in ectopic gestation cases roughly corresponded to those of the peripheral blood of the patients

The good, the bad and the ugly on COVID-19 tourism recovery

© 2020 Elsevier Ltd This paper is to produce different scenarios in forecasts for international tourism demand, in light of the COVID-19 pandemic. By implementing two distinct methodologies (the Long Short Term Memory neural network and the Generalized Additive Model), based on recent crises, we are able to calculate the expected drop in the international tourist arrivals for the next 12 months. We use a rolling-window testing strategy to calculate accuracy metrics and show that even though all models have comparable accuracy, the forecasts produced vary significantly according to the training data set, a finding that should be alarming to researchers. Our results indicate that the drop in tourist arrivals can range between 30.8% and 76.3% and will persist at least until June 2021

Flight Mechanics and Control of Escape Manoeuvres in Hummingbirds. I. Flight Kinematics

Hummingbirds are nature’s masters of aerobatic manoeuvres. Previous research shows that hummingbirds and insects converged evolutionarily upon similar aerodynamic mechanisms and kinematics in hovering. Herein, we use three-dimensional kinematic data to begin to test for similar convergence of kinematics used for escape flight and to explore the effects of body size upon manoeuvring. We studied four hummingbird species in North America including two large species (magnificent hummingbird, Eugenes fulgens, 7.8 g, and blue-throated hummingbird, Lampornis clemenciae, 8.0 g) and two smaller species (broad-billed hummingbird, Cynanthus latirostris, 3.4 g, and black-chinned hummingbirds Archilochus alexandri, 3.1 g). Starting from a steady hover, hummingbirds consistently manoeuvred away from perceived threats using a drastic escape response that featured body pitch and roll rotations coupled with a large linear acceleration. Hummingbirds changed their flapping frequency and wing trajectory in all three degrees of freedom on a stroke-by-stroke basis, likely causing rapid and significant alteration of the magnitude and direction of aerodynamic forces. Thus it appears that the flight control of hummingbirds does not obey the ‘helicopter model’ that is valid for similar escape manoeuvres in fruit flies. Except for broad-billed hummingbirds, the hummingbirds had faster reaction times than those reported for visual feedback control in insects. The two larger hummingbird species performed pitch rotations and global-yaw turns with considerably larger magnitude than the smaller species, but roll rates and cumulative roll angles were similar among the four species

Flight Mechanics and Control of Escape Manoeuvres in Hummingbirds. II. Aerodynamic Force Production, Flight Control and Performance Limitations

The superior manoeuvrability of hummingbirds emerges from complex interactions of specialized neural and physiological processes with the unique flight dynamics of flapping wings. Escape manoeuvring is an ecologically relevant, natural behaviour of hummingbirds, from which we can gain understanding into the functional limits of vertebrate locomotor capacity. Here, we extend our kinematic analysis of escape manoeuvres from a companion paper to assess two potential limiting factors of the manoeuvring performance of hummingbirds: (1) muscle mechanical power output and (2) delays in the neural sensing and control system. We focused on the magnificent hummingbird (Eugenes fulgens, 7.8 g) and the black-chinned hummingbird (Archilochus alexandri, 3.1 g), which represent large and small species, respectively. We first estimated the aerodynamic forces, moments and the mechanical power of escape manoeuvres using measured wing kinematics. Comparing active-manoeuvring and passive-damping aerodynamic moments, we found that pitch dynamics were lightly damped and dominated by the effect of inertia, while roll dynamics were highly damped. To achieve observed closed-loop performance, pitch manoeuvres required faster sensorimotor transduction, as hummingbirds can only tolerate half the delay allowed in roll manoeuvres. Accordingly, our results suggested that pitch control may require a more sophisticated control strategy, such as those based on prediction. For the magnificent hummingbird, we estimated that escape manoeuvres required muscle mass-specific power 4.5 times that during hovering. Therefore, in addition to the limitation imposed by sensorimotor delays, muscle power could also limit the performance of escape manoeuvres

Occupational exposure assessment for power frequencyelectromagnetic fields

Exposure assessment is the determination or estimate of the magnitude, frequency of occurrence, and rate of exposure of an individual or a group to an environmental agent. The agents of interest in this case are the electric and magnetic fields (EMF) in the extreme low frequency range that includes the power frequency of 50/60 Hz. There are an increasing concern that exposure to EMF may be associated with biological and health effects. This concern has prompted numerous measurement projects and the development of instrumentation, methodologies, and exposure models and simulations. This paper identifies the status of EMF exposure assessment research related to occupational exposures. It draws the results to emphasize the unique aspects of EMF exposures in the home and utilities environments, and highlights the research needs. The intensities of electromagnetic fields have been measured under power transmission and distribution lines, at substations and industrial plants and near various electric devices including domestic electrical equipment. The field intensities have been related to the exposure time (duration of staying) in the different areas and have been compared with the international established standards. The data presented are useful for understanding the levels of electromagnetic fields that can be encountered in various places and also for estimating possible occupational and residential exposure level

Occupational exposure assessment for power frequencyelectromagnetic fields

Exposure assessment is the determination or estimate of the magnitude, frequency of occurrence, and rate of exposure of an individual or a group to an environmental agent. The agents of interest in this case are the electric and magnetic fields (EMF) in the extreme low frequency range that includes the power frequency of 50/60 Hz. There are an increasing concern that exposure to EMF may be associated with biological and health effects. This concern has prompted numerous measurement projects and the development of instrumentation, methodologies, and exposure models and simulations. This paper identifies the status of EMF exposure assessment research related to occupational exposures. It draws the results to emphasize the unique aspects of EMF exposures in the home and utilities environments, and highlights the research needs. The intensities of electromagnetic fields have been measured under power transmission and distribution lines, at substations and industrial plants and near various electric devices including domestic electrical equipment. The field intensities have been related to the exposure time (duration of staying) in the different areas and have been compared with the international established standards. The data presented are useful for understanding the levels of electromagnetic fields that can be encountered in various places and also for estimating possible occupational and residential exposure level

Interfacial breakdown on contaminated electrolytic surfaces

The insulation of overhead transmission lines and substations is subjected to several basic types of abnormal conditions that can cause flashovers and outages of long duration. One of these types is abnormal voltage gradients in the insulation system caused by the contamination of solid insulator surfaces. The number of insulators needed to protect against contamination is uncertain, because there is a wide range in the severity of contamination, and there is considerable uncertainty as to the basic mechanisms by which contamination affects the insulation level of a given configuration. This paper outlines the results of investigations of interfacial breakdown on electrolytic surfaces. Models are used to simulate such plotted insulator problems. Effects of the chemical nature of the contaminants and contamination levels on the critical flashover voltage are studied. In order to study such effects, different salts and salts combinations were used on the laboratory model. A single-arc and multiple-arc models are introduced where the phenomena of multiple discharges existing simultaneously on an electrolytic surface is also investigated. Mathematical models are suggested which include the successive formation of multiple-arcs. The results obtained based on the new model agree quite well with the experimental value

Interfacial breakdown on contaminated electrolytic surfaces

The insulation of overhead transmission lines and substations is subjected to several basic types of abnormal conditions that can cause flashovers and outages of long duration. One of these types is abnormal voltage gradients in the insulation system caused by the contamination of solid insulator surfaces. The number of insulators needed to protect against contamination is uncertain, because there is a wide range in the severity of contamination, and there is considerable uncertainty as to the basic mechanisms by which contamination affects the insulation level of a given configuration. This paper outlines the results of investigations of interfacial breakdown on electrolytic surfaces. Models are used to simulate such plotted insulator problems. Effects of the chemical nature of the contaminants and contamination levels on the critical flashover voltage are studied. In order to study such effects, different salts and salts combinations were used on the laboratory model. A single-arc and multiple-arc models are introduced where the phenomena of multiple discharges existing simultaneously on an electrolytic surface is also investigated. Mathematical models are suggested which include the successive formation of multiple-arcs. The results obtained based on the new model agree quite well with the experimental value