Narrow Results

This paper outlines the various driving and control techniques for Light Emitting Diodes (LEDs). LEDs should be driven from a constant current source. High power LEDs are usually driven from a switching regulator, for reasons of efficiency. The types of drivers described include Buck (step-down), Boost (step-up) and Buck-Boost (step-up or step-down). Isolated drivers and Power Factor Correction (PFC) circuits are also described. This brief paper can only describe the basic outline of these circuits, but this should be sufficient to allow the basic principles to be understood.

The document presents a general overview of the electron reconstruction, identification and isolation performance in the ATLAS experiment. The results are obtained using 13TeV proton–proton collision data collected during the LHC Run-2. The electron reconstruction efficiency is higher than 97%, and the ratio of data to Monte Carlo simulation efficiency is close to unity, with associated uncertainties generally smaller than 0.1%. The electron identification is shown for three working points, and depending on the electron $E_T$, it can be as low as 60%, increasing to more than 80% above 50GeV. The correction factors are close to one, generally within 5%. Five isolation working points are recommended in the ATLAS experiment, to successfully reject fake/nonprompt electrons. Their dependency on the electron identification working points is shown and discussed, as well as their pile-up dependency, and their performance versus electron $E_T$ and $\eta$.

To solve the problem that it is difficult to install isolation resistors across each output port, a new five-way microstrip Wilkinson power divider with double-layer topology is developed. The isolation resistors are placed on the second substrate by using half-wavelength microstrip transmission lines with the introduction of Archimedean spirals to reduce the circuit size. To demonstrate the design method, a five-way equal power divider is designed; its size is optimized at the center frequency of 2.45 GHz. The fabricated sample has been tested. Measured results are in good agreement with simulations.

The quarantine of suspected cases and isolation of individuals with symptoms are two of the primary public health control measures for combating the spread of a communicable emerging or re-emerging disease. Implementing these measures, however, can inflict significant socio-economic and psychological costs. This paper presents a deterministic compartmental model for assessing the single and combined impact of quarantine and isolation to contain an epidemic. Comparisons are made with a mass vaccination program. The model is simulated using parameters for influenza-type diseases such as SARS. The study shows that even for an epidemic in which asymptomatic transmission does not occur, the quarantine of asymptomatically-infected individuals can be more effective than only isolating individuals with symptoms, if the associated reproductive number is high enough. For the case where asymptomatic transmission occurs, it is shown that isolation is more effective for a disease with a small basic reproduction number and transmission coefficient of asymptomatically-infected individuals. If asymptomatic individuals transmit at a rate that is at least 20% that of symptomatic individuals, quarantine is always more effective. The study further shows that the reduction in disease burden obtained from a combined quarantine and isolation program can be comparable to that obtained by a vaccination program, if the former is implemented quickly enough after the onset of the outbreak. If the implementation of such a quarantine/isolation program is delayed, however, even for a short while, its effectiveness decreases rapidly.

Optimal control theory is applied to a system of ordinary differential equations modeling the population dynamics of tuberculosis with isolation and immigration of infective. Seeking to minimize the number of infectious individuals and reduce the transmission of the disease, we use controls to represent the screening/medical testing of infected immigrants into the population as well as isolation of infective in the population. The optimal controls are characterized in terms of the optimality system, which is solved numerically for several scenarios using an iterative method with Runge-Kutta fourth order scheme. Parameter values used are those reported for Nigeria.

To fight against Ebola virus disease, several measures have been adopted. Among them, isolation, safe burial and vaccination occupy a prominent place. In this paper, we present a model which takes into account these three control strategies as well as the indirect transmission through a polluted environment. The asymptotic behavior of our model is achieved. Namely, we determine a threshold value ${{ℛ}}_c^c$ of the control reproduction number ${{ℛ}}_c$, below which the disease is eliminated in the long run. Whenever the value of ${{ℛ}}_c$ ranges from ${{ℛ}}_c^c$ and 1, we prove the existence of a backward bifurcation phenomenon, which corresponds to the case, where a locally asymptotically stable positive equilibrium co-exists with the disease-free equilibrium, which is also locally asymptotically stable. The existence of this bifurcation complicates the control of Ebola, since the requirement of ${{ℛ}}_c$ below one, although necessary, is no longer sufficient for the elimination of Ebola, more efforts need to be deployed. When the value of ${{ℛ}}_c$ is greater than one, we prove the existence of a unique endemic equilibrium, locally asymptotically stable. That is the disease may persist and become endemic. Numerically, we fit our model to the reported data for the 2018–2020 Kivu Ebola outbreak which occurred in Democratic Republic of Congo. Through the sensitivity analysis of the control reproduction number, we prove that the transmission rates of infected alive who are outside hospital are the most influential parameters. Numerically, we explore the usefulness of isolation, safe burial combined with vaccination and investigate the importance to combine the latter control strategies to the educational campaigns or/and case finding.

In this paper, we propose an epidemic model of SIR type with ratio-dependent impulse control and Beddington–DeAngelis (B–D) incidence. According to the magnitude of the basic reproductive number ${{ℛ}}_0$ and the relation of the endemic equilibrium $(S^{\ast },I^{\ast })$ and the ratio threshold $h$, dynamical analysis of the controlled system is conducted. Under the control strategy, if ${{ℛ}}_0\le 1$, the solutions converge to the disease-free equilibrium. If ${{ℛ}}_0>1$ and $\frac{I^{\ast }}{S^{\ast }}>h$, the impulsive system has periodic solution that is orbitally asymptotically stable, and order-$k(k>2)$ periodic solution does not exist. Furthermore, if ${{ℛ}}_0>1$ and $\frac{I^{\ast }}{S^{\ast }}<h$, the solution converges either to the endemic equilibrium or to a periodic solution, which is proved to be determined by the initial value. Finally, numerical simulations are performed to demonstrate the theoretical results.

Friction pendulum bearing (FPB) shows superior performance in reducing dynamic responses of structures under earthquakes. Though the seismic response of the FPB-isolated structure is well understood, its overturning resistance caused by limited permissible displacement under impact is rarely studied. This paper presents an evaluation and parametric study on the overturning resistance of the FPB-isolated structure under impact, using particularly the coefficient of overturning resistance to evaluate the overturning resistance of the isolated structure. The capacity of the overturning resistance of FPB-isolated structure as well as the seismic response when the isolated structure subjected to pluse-like and no-pluse-like earthquake records were addressed. The influence of various key factors, including the vertical component of impact force, displacement ratio, properties of the FPB, peak ground acceleration (PGA), and mass ratio of the isolation storey, is investigated to give an insight into the potential overturning risk of the entire structure. The results indicate that the overturning resistance of the FPB-isolated structure will be reduced significantly due to the presence of impact. The overturning stability depends mainly on the displacement ratio, impact stiffness, PGA, friction coefficient, and equivalent radius of the FPB, but the mass ratio of the isolation storey shows limited influence on the overturning resistance of the FPB-isolated structure under impact.

Large seismic isolation bearings and/or dampers are currently used to seismically retrofit several long-span bridges. These large devices must be thoroughly tested at full-scale with real-time seismic demands, necessitating new, larger seismic testing facilities. Accurate performance characterisation of these devices depends on thorough characterisation of the seismic testing facility itself. One component of this essential systems' characterisation is a mathematical simulation model. Although linear modelling techniques have traditionally been used to characterise seismic facilities, many of the large system's unique behaviours, parameters and non-linearities significantly reduce the accuracy of linear modelling techniques. These significant characteristics are discussed in detail. A more comprehensive non-linear modelling approach is required for these large facilities, and a simulation model using a non-linear time-history dynamic analysis approach is outlined.

In this paper, we compare the vulnerability of isolated and conventional structures as well as equipment when uncertainty on the excitation and on some of the structural properties is considered. This comparison is performed, mainly, with a series of Monte Carlo simulations. The results clearly show the higher sensitivity of isolated structures and their equipment when submitted to statistically reasonable excitations that are different from those used for their design. This fact is recognised by some, but not all, earthquake regulations, mainly, by considering lower behaviour factors for isolated structures than for conventional ones. Although isolated structures designed according to these recommendations (e.g. FEMA 368) exhibit low damage less frequently than conventional structures, the probability of failure is similar for both types of structure.

It has been observed that after some earthquakes a number of structures resting on spread footings responded to seismic excitation by rocking on their foundation and in some cases this enabled them to avoid failure. Through application to a standard bridge supported by direct foundations, this paper discusses the major differences in response when foundation uplift is taken into consideration. Special focus is given on the modifications of rocking response under biaxial and triaxial excitation with respect to uniaxial excitation. It is found that inelastic rocking has a significant isolation effect. It is also shown that this effect increases under biaxial excitation while it is less sensitive to the vertical component of the earthquake. Finally, parametric analyses show that the isolation effect of foundation rocking increases as the size of the footing and the yield strength of the underlying soil decreases.

In the first part of this paper the objectives of an isolation system for a bridge structure are discussed, in relation to modelling options and modification of the traditional capacity design principles. A displacement-based design approach is then presented, using a linear equivalent single degree-of-freedom model. The preliminary design of an isolation system for existing bridges is based on the definition of a "structure regularity" which allows the estimation of whether the response of the real structure will be similar to that predicted in the preliminary design phase. The efficiency of the approach is shown in designing the isolation system for a highly irregular bridge.

A disease outbreak with 71% (cumulative) mortality was reported in a freshwater hybrid sturgeon farm located in Hualien County, Taiwan. The moribund fish showed signs of lethargy, anorexia, diffuse external hemorrhages around mouth and anus, and on the base of fin and abdomen surface accompanied with abdomen swelling. Post-mortem examination revealed multiple red patches ranging from 1 to 5 cm in size on the liver. The histopathology revealed extensive coagulative to liquefied necrosis of various sizes in the liver and spleen. Focal necrosis of kidney was also evident. The lesions were positive with Ziehl-Neelsen acid fast staining. A rapid growth of nontuberculous mycobacteria (NTM) was isolated from liver of moribund sturgeon and the polymerase chain reaction (PCR) studies using primer sets derived from Mycobacterium sp. suggested this NTM was closely related to Mycobacterium marinum. There was only one bacterial colony been isolated in brain heart infusion agar (BHI Agar) and been identified as Streptococcus iniae. These findings suggest that a bacterium identified as belonging to M. marinum might cause heavy mortality.

The isolation of surface wave-induced vibration using periodically modulated piles in soil is investigated. We demonstrate through simulations the dependence of complete bandgaps on the lattice symmetries, geometric parameters of the piles and material properties of the soil. The simulated results suggest that the piles modulated with square and hexagonal lattices are much more favorable for the formation of complete bandgaps than those modulated with honeycomb lattice. The height of the piles also plays a significant role in governing the evolution of complete bandgaps. Besides, complete bandgaps can be tuned by tailoring the volume fraction of the piles and the geometries of the pile cross section. Our results indicate that the contrast in the Young's modulus and the density is vital for the evolution of complete bandgaps and the viscosity of the soil should be considered as well. The analysis of surface wave propagation in a finite number of piles confirms the simulated complete bandgaps and also reveals that the complete bandgaps stem from Bragg interferences. This paper not only demonstrates the promising application of periodically modulated piles as wave barriers but also provides design guidelines for civil engineers.

In this research work, we have developed and analyzed a deterministic epidemiological model with a system of nonlinear differential equations for controlling the spread of Ebola virus disease (EVD) in a population with vital dynamics (where birth and death rates are not equal). The model examines the disease transmission dynamics with isolation from exposed and infected human class and effect of vaccination in susceptible human population through stability analysis and bifurcation analysis. The model exhibits two steady state equilibria, namely, disease-free and endemic equilibrium. Next generation matrix method is used to find the expression for $R_0$ (the basic reproduction number). Local and global stability of diseases-free equilibrium are shown using nonsingular M-matrix technique and Lyapunov’s theorem, respectively. The existence and local stability of endemic equilibrium are explored under certain conditions. All numerical data entries are supported by various authentic sources. The simulation study is done using MATLAB code 45 which uses Runge–Kutta method of fourth order and we plot the time series and bifurcation diagrams which support our analytical findings. Stability analysis of the model shows that the disease-free equilibrium is locally as well as globally asymptotically stable if $R_0<1$ and endemic equilibrium is locally asymptotically stable in absence of vaccination if $R_0>1$. Using central manifold theorem, the presence of transcritical bifurcation for a threshold value of the transmission rate parameter $\beta$ when $R_0$ passes through unity and backward bifurcation (i.e. transcritical bifurcation in opposite direction) for some higher value of $R_0$ are established. Our simulation study shows that isolation of exposed and infected individuals can be used as a more effective tool to control the spreading of EVD than only vaccination.

The effect of different isolator parameters on earthquake response of base-isolated liquid storage tanks is investigated herein. Mechanical analog, with three lumped masses, is used to model ground supported base-isolated liquid storage tank, and analyzed for recorded earthquake ground accelerations. The nonlinear force–deformation behavior of the isolator is mathematically modeled in two different ways, represented by (a) equivalent linear elastic-viscous and (b) bi-linear hysteretic behaviors. The equations of motion for the base-isolated tank are derived and solved in the incremental form using Newmark's step-by-step method of integration. Two different configurations of liquid storage tank (i.e. broad and slender) are considered to show the effect of the equivalent linear and bi-linear modeling of the isolator on the important earthquake response quantities. Effect of nonlinear hysteretic modeling of the isolator on peak response of the base-isolated liquid storage tanks is also investigated. The effect on earthquake response of the base-isolated liquid storage tank is studied for different parameters of the isolator for a range of slenderness ratio of the tank. The parameters considered include the characteristic strength of the isolator, isolation time period, isolator yield displacement etc. Significant difference is observed in the earthquake response of the base-isolated liquid storage tanks owing to the equivalent linear and bi-linear modeling approaches of the isolator. However, for bi-linear and nonlinear hysteretic modeling of the isolator, difference between the peak earthquake response of base-isolated liquid storage tanks are insignificant. The earthquake response of base-isolated liquid storage tanks is significantly influenced by the variation in the isolator parameters and slenderness ratio of the tank.

A 500-kV power transformer substation was focused on for seismic performance examination. Finite element models of the power transformer, isolation layers, site soil, bus bars and support structure were established under various analysis conditions. By inputting typical ground motions into the models, seismic time history responses were obtained. First, the seismic performance, critical position and failure modes of a single power transformer without isolation were examined. Then, the effect on the power transformer by arranging isolation bearings was confirmed. Moreover, the influence of site soil dynamic characteristics on the isolating performance of the power transformer was examined. Finally, the influence of the length margin of the bus bars on the seismic response of the isolated power transformer was analyzed. It was revealed that the bottom of the transformer bushings which were made of porcelain was a weak part. Installing isolation bearings effectively reduced the maximum stress response of the bushing for most ground motions. The dynamic characteristics of the site soil significantly affected the isolation efficiency of the power transformer, and the expected isolation effect was achieved when the soil was soft. The displacement response of the transformer was largely increased by isolation, the pulling effect of the bus bars on the porcelain bushing was significant. When the length margin of the bus bars was enlarged to 1.0m, the influence on the bushing decreased to a low level that could be ignored.

By means of asymptotically stable theory and infection model theory of ordinary differential equation, we do research on SIQS model with nonlinear and isolation. Firstly, we obtain the existence of threshold value R₀ of disease-free equilibration point and local disease equilibration point. Secondly, we prove disease-free equilibration point is locally asymptotically stable when R₀ < 1, and local disease equilibration point is locally asymptotically stable when R₀ > 1. Furthermore, we have disease-free equilibration point and local disease equilibration point are globally asymptotically stable with the help of Liapunov function. Lastly, we explain at the point of biology.

There has been a global attack of A/H1N1 virus in 2009, which widely affected the world's normal stability and economic development. Since the emergence of the first diagnosed A/H1N1 influenza infected person in 11 May 2009 in China, very strict policy including quarantine and isolation measures were widely implemented to control the spread of this disease before the vaccine appeared. We propose a compartmental model that mimics the infection process of A/H1N1 under control strategies taken in mainland China. Apart from theoretical analysis, using the statistic data of Shaanxi Province, we estimated the unknown epidemiological parameters of this disease in Shaanxi via least-squares fitting method. The estimated control reproductive number of H1N1 for its first peak was (95% CI: 2.362–2.748) and that for the second peak was (95% CI: 1.765–2.001). Our findings in this paper suggest that neither quarantine nor isolation measures could be relaxed, and the implementation of these interventions can reduce the pandemic outbreak of A/H1N1 pandemic significantly.

More than 20 outbreaks of Ebola virus disease have occurred in Africa since 1976, and yet no adequate treatment is available. Hence, prevention, control measures and supportive treatment remain the only means to avoid the disease. Among these measures, contact tracing occupies a prominent place. In this paper, we propose a simple mathematical model that incorporates imperfect contact tracing, quarantine and hospitalization (or isolation). The control reproduction number ${{ℛ}}_c$ of each sub-model and for the full model are computed. Theoretically, we prove that when ${{ℛ}}_c$ is less than one, the corresponding model has a unique globally asymptotically stable disease-free equilibrium. Conversely, when ${{ℛ}}_c$ is greater than one, the disease-free equilibrium becomes unstable and a unique globally asymptotically stable endemic equilibrium arises. Furthermore, we numerically support the analytical results and assess the efficiency of different control strategies. Our main observation is that, to eradicate EVD, the combination of high contact tracing (up to 90%) and effective isolation is better than all other control measures, namely: (1) perfect contact tracing, (2) effective isolation or full hospitalization, (3) combination of medium contact tracing and medium isolation.