Towards SLA Policy Refinement for QoS Management in Software-Defined Networking

The ID-HILS setup considered in this study couples an engine-in-the-loop simulation EILS setup in Ann Arbor, MI, with a driver and vehicle model inWarren, MI. Towards SLA Policy Refinement for QoS Management in Software-Defined Networking the setup at the highest level. Systems with italic labels are modeled, and regular labels denote physical systems. Even though the ultimate goal is to use human drivers, a driver model is considered  in this paper to increase repeatability of simulations and to eliminate the variation due to the human driver. The driver model follows the  drive cycle up through the first two hills of this cycle. The coupling point for this integration is chosen at the end of the transmission, so the physical engine and the transmission model constitute the Ann Arbor site, and the rest of the vehicle and driver models constitute theWarren site.

The coupling variables exchanged by the two sites are the torque and speed of the transmission shaft. More specifically, the Ann Arbor site sends the transmission output torque, andWarren site sends the transmission output speed. In addition, the Warren site also sends the throttle command, which is fed to the drivetrain model and, through an idle controller, to the engine on the Ann Arbor site. The hardware components and models comprising this IDHILS system will be described in detail next. Towards SLA Policy Refinement for QoS Management in Software-Defined Networking The Ann Arbor site uses a  diesel engine in combination with drivetrain, flywheel and idle controller models. A highfidelity AC electric dynamometer couples the physical engine with the models in real time.

Towards SLA Policy Refinement for QoS Management in Software-Defined Networkings

The sole purpose of the flywheel model, which is simply a small inertia element, is to reverse the causality between the drivetrain model and the engine, provide a speed input to the engine and receive torque from the engine. This is done to control the engine speed, which proves to be much more stable than trying to control the engine torque. In addition, an idle controller model, a simple PI controller with anti-windup, is used to override the engine’s own internal idle controller and to idle around to prevent the engine from stalling. The drivetrain model includes the torque converter, transmission, and shift logic. The torque converter model is a static model that takes pump and turbine speeds as inputs and generates pump and turbine torques according to the equations is the speed ratio between turbine and pump speeds, is a piecewise function approximating a desired capacity factor curve, and  is a piecewise linear function approximating a desired torque ratio curve.

The transmission takes into account the transmission shaft inertia, stiffness, and damping, as well as the gear inefficiencies and torque losses due to fluid churning. Specifically, the speed reduction in each gear is assumed to be ideal, while the torque multiplication is assumed to be scaled by an efficiency factor. Furthermore, the torque lost due to fluid churning is modeled as variable nonlinear resistance of the form where are coefficients that change depending on the gear, and  is the angular speed of the transmission shaft at the torque converter end. The inputs to the shift logic, the final element in the drivetrain model, are the transmission output shaft speed and the throttle demanded by the driver. A simple chart, as shown in, determines the current gear number and whether or not an upshift or downshift is to be initiated. The solid and dashed lines indicate upshift and downshift thresholds, respectively.The Warren site includes the driver and vehicle dynamics models. The driver model, which takes the desired and actual vehicle velocities as inputs, is a PI controller with saturation and anti-windup in conjunction with preview. Towards SLA Policy Refinement for QoS Management in Software-Defined Networking The vehicle dynamics model is a point mass representation of the vehicle and includes differentials, wheel inertia, a Coulomb and viscous-friction-based brakemodel, rolling resistance, aerodynamic drag, and tire slip.

Publisher mobility support in content centric networks

Although the effect of delay on transparency is well appreciated, Publisher mobility support in content centric networks the challenge of maintaining transparency despite the information loss when a simulation is distributed is typically an underestimated one. Publisher mobility support in content centric networks To illustrate this challenge a very simple example is given in this section. Consider a second-order linear autonomous system described second-order numerical integration method that calculates the states at the next time step using the formula where h is the integration step size. Publisher mobility support in content centric networks In words, Heun’s method uses Euler’s method to predict the slope at the next time step and uses the average of the slopes at times t and the trapezoidal rule, to correct the estimate of the state at the next time step. As  indicates, this results in a local error that is leading to a global error that is  making Heun’s method a second-order method.

The integration of  into the first equation of  yields the following equation for the estimation of the first state at the next time step This is the equation the solver would use to calculate , if the equations were solved in an integrated way by a single solver. Now, consider a distributed solution of this problem, as illustrated . The two equations are solved by two separate  solvers that exchange only the information about the states, which are the variables coupling the two state equations.Assume  that the solvers are synchronized and the information exchange is happening without any delay, so that the states are known to both solvers at each time step and there are no sampling and holding effects.

Publisher mobility support in content centric network

Publisher mobility support in content centric networks In this case, becomes an external input for the first solver rather than being a state, and the estimate for the first state at the next time step becomes Notice that the penultimate term in  is missing in Also notice that the missing term includes the second state equation of which is not available to the first solver in the distributed setting. This makes the local error  instead of because the missing term includes  as a multiplier. This increase in error happens despite the fact that a secondorder integrator is being used, and is caused by the distributed architecture. A numerical example can provide further sense of severity of this issue. Consider the system  Aone-step numerical integrationwith a step size of gives an error in whereas the error in the distributed solution is, approximately  times larger than the nondistributed solution.

Publisher mobility support in content centric networks Furthermore, halving the step size brings the nondistributed solution error down to, one-eighth of the previous error, an improvement that is as theoretically promised by Heun’s method. Publisher mobility support in content centric networks However, the error in the distributed solution reduces only to, only one fourth of the error obtained with , an improvement that is only as predicted by This simple example highlights the fact that distribution in and of itself can be an important source of error. Typically, when systems are distributed, each site in the distributed simulation has access to only the coupling variables and not all the states and  state derivates of the other sites, which can reduce the simulation accuracy as illustrated in this example. Thus, distributing the simulation may cause a significant degradation in transparency, and hence receives special attention in this paper. Publisher mobility support in content centric networks

where through tf are the discrete time instances at which output measurements are made. Furthermore, let y0 represent the baseline trajectory that the repeated simulations try to reproduce. Then, the standard deviation σi,j of the ith simulation of the jth configuration is defined as the standard deviation of the residuals from the baseline data,This leads to the following average standard deviations of the  For the purposes of this work, it is proposed that the degradation in transparency be characterized by a statistically significant change in the average standard deviation of the residuals. On the Tradeoff between Performance and User Privacy in Information Centric Networking Formally, the null hypothesis is that all system configurations are transparent for the chosen output signal, there is no statistically significant difference between the This null hypothesis can be checked against the alternative that not all are the same using a one-way analysis of variance matrix of standard deviations On the Tradeoff between Performance and User Privacy in Information Centric Networking, with σi,j being the ith row jth column element. An  ANOVA of  then reveals if there is a statistically significant difference between the The outcome ofANOVAis a p-value, which is the probability of making an observation such as even more diverse than  assuming that the null hypothesis is true. A high p value, typically, thus indicates that there is no statistically significant difference between the different configurations, as the differences between the can be attributed to chance. In that case, it can be concluded that the system configurations are transparent for the particular output variable considered. If the p value is low, typically if p, then the null hypothesis is rejected it is concluded that there is a statistically significant difference between the, and thus, between the configurations. In that case the conclusion is that at least one of the configurations has a statistically significant loss in transparency; however,ANOVAdoes not indicate which one. To determine which configurations are not transparent, a post hoc pairwise comparison test is necessary, and Tukey’s test is one alternative. On the Tradeoff between Performance and User Privacy in Information Centric Networking Tukey’s test considers the confidence intervals of the estimates of the column means, and concludes that two given columns, configurations, are statistically significantly different, if there is no overlap between their confidence intervals. Thus, pairwise comparisons where one of the pairs is the ideal configuration can be used to determine which configuration has a statistically significant loss in transparency. Furthermore, when a configuration is found to have a statistically significant loss in transparency, the distance between theconfidence intervals can be used as a quantification of this loss. It is important to remark that both ANOVA and Tukey’s test are parametric tests and thus, are based on some assumptions about the distributions that the data are obtained from. Specifically, the underlying assumption of both ANOVA and Tukey’s test is that the columns are independent observations coming from normal distributions with equal variances. On the Tradeoff between Performance and User Privacy in Information Centric Networking There are two ways to handle a violation of this assumption. One can either rely on the reported robustness of both tests to violations of this assumption or one can use the nonparametric counterparts of these tests, which are based on ranks and thus, do not rely on assumptions of normality The first approach is adopted in this paper; hence, formal tests of the validity of the underlying assumptions are omitted. Nevertheless, should the robustness of these methods become a concern during an analysis, Kruskal-Wallis for example, can be used instead ofANOVA, andWilcoxon rank sum test with a Bonferroni correction could replace Tukey’s test. It is worth noting, however, that such rank based tests have been found to be very conservative compared to the parametric tests employed here. On the Tradeoff between Performance and User Privacy in Information Centric Networking

Community detection in opportunistic networks using memory-based cognitive heuristics

Thus, perfect transparency is achieved when this ratio is for all frequencies. Community detection in opportunistic networks using memory-based cognitive heuristicsThis impedance-based quantification of transparency has been used by other researchers, as well and also been extended to linear time-delay systems As a transparency metric for telesurgery, C¸ avus¸o˘glu et al. suggested a weighted norm of the sensitivity of the transmitted impedance to the environmental impedance whereWs is a is a frequency-dependent weighting function, and  Ze is the nominal environment impedance Rather than using a ratio, De Gersem et al.

proposed to use a difference as a transparency metric Specifically, assuming that the environment can be described as a pure stiffness, they characterize transparency as where Wp is a low-pass weighting function implementing the performance bandwidth requirement, ke is the environment stiffness for an environment with negligible damping and inertial characteristics, and K and σ are constant factors for scaled telemanipulation and enhanced sensitivity, Community detection in opportunistic networks using memory-based cognitive heuristicsrespectively. Rather than using impedances,Yokokohji andYoshikawa proposed to use the correspondence between the position and force signals as a metric for transparency Specifically, they define the integrals where ωmax is the manipulation bandwidth of human operators, T is time constant of first order lag, and Gmp, Gsp , Gmf , and force, and slave force, respectively.

Community detection in opportunistic networks using memory-based cognitive heuristic

The index is zero, if themaster and slave positions forces perfectly match. Therefore, formaximum transparency, both indices are desired to be zero. Griffiths et al., on the other hand, proposed the distortion metric, which is defined as the difference between the desired and actual rendered dynamics in an haptic device normalized with respect to the desired dynamics where Rd is the desired dynamics and P is the actual rendered dynamics Therefore, maximum transparency is achieved when distortion is equal to zero. This metric allows to frame the problem as a general control configuration, a configuration in which the performance variable is different than the feedback variable, and takes advantage of the knowledge about the fundamental limitations of the general control configuration as first highlighted by Freudenberg These metrics are useful in linear, deterministic frameworks, but the nonlinear, stochastic nature of ID-HILS systems, in general, limits their utility. Therefore, a statistical characterization of transparency is proposed in the next section. Any HILS setup will have some inherent variation in it due to the hardware components involved. Distribution over the Internet will introduce additional variation.

It is important to know whether this additional variation is negligible or significant relative to the inherent variation in the output signals of interest. If it is negligible, then the system can be considered transparent with respect to the chosen outputs; otherwise there is a noticeable degradation in transparency. This section formalizes this statistical approach to characterizing transparency. Let n denote the number of different configurations of a system to be compared, each with a different level of distribution. To capture the inherent variation in the setup, one of these configurations needs to be the ideal case, direct integration without distribution and without the Internet. The remaining configurations need to capture the effects that are being analyzed for their impact on transparency. Community detection in opportunistic networks using memory-based cognitive heuristics Thus, to differentiate between the inherent variation in the setup, the variation due to distribution, and the variation due to the Internet QoS, for example, at least three different configurations need to be considered. These are the ideal case the case, which considers a distributed system, but with a negligible delay the Internet-distributed case that captures the impact of Internet QoS, as well. Community detection in opportunistic networks using memory-based cognitive heuristics

This knowledge could then guide thedevelopment of appropriate strategies to improve transparency and could even indicate some fundamental limitationsFinally, the third goal of the paper is to investigate whether transparency is an independent property of the system, or if different output signals in the system can experience different levels of transparency. The significance of this goal is that it will help find out whether or not establishing the transparency in a set of output signals would also automatically ensure the transparency in other signals in the system, as well. You: What Generation Y Thinks about Corporate Social Networking Applications? In summary, the goals of this paper can be listed as follows. Development of a statistical transparency analysis method. Comparing the relative impact of Internet QoS versus distribution on transparency using the developed transparency analysis method on a sample ID-HILS system. Experimentally investigating whether transparency is an independent property of the system or an output-signal dependent property. Previous work on ID-HILS systems concentrated on investigating observer-based and observer-free alternatives to integrating HILS systems over the Internet, but did not address the aforementioned goals of this paper. For example, Compere et al. proposed an observer-based method to overcome the adverse affects of Internet QoS and distributed simulation and achieve a stable ID-HILS system Specifically, they successfully integrated a ride motion simulator in Warren, MI, with a hybrid power system in Santa Clara, CA, You: What Generation Y Thinks about Corporate Social Networking Applications?over the Internet. A rigorous transparency analysis, however, was not performed. A similar integration has been achieved by Ersal with an engine-in-the-loop simulation EILS setup in Ann Arbor, MI and the aforementioned ride motion simulator in Warren, MI but without relying on observers and using an event-based framework However, a rigorous experimental analysis of transparency was not feasible due to the infeasibility of directly coupling the two HILS setups. The paper explores its second and third research goals on a new ID-HILS system. Specifically, the Internet-distributed integration of the aforementioned EILS setup in Ann Arbor with simple vehicle and driver models in Warren is considered. In addition, the same event-based framework mentioned above is utilized. The transparency of this setup has been previously analyzed in simulation in which the EILS setup was modeled so that the only source of stochasticity was the Internet. This paper considers the actual hardware and the proposed statistical analysis method helps distinguish the variation introduced by the distribution over the Internet from the inherent variation in the hardware. The rest of the paper is organized as follows. Section first reviews the transparency metrics proposed in the literature and then presents the proposed statistical transparency analysis. Section illustrates on a simple example how significant the impact of distributing the simulation on transparency can be, You: What Generation Y Thinks about Corporate Social Networking Applications? even if there are no sampling or delay effects. This section motivates the special attention given in the paper to characterizing the effect of distributing the simulation. Section describes the ID-HILS setup considered in this study in detail. Section describes the four system configurations devised for this study, each aimed to capture the effect of a different source of variation. Section applies the proposed statistical transparency analysis to the ID-HIL setup and discusses the findings. Finally, Section summarizes the work, its conclusions, and original contributions. You: What Generation Y Thinks about Corporate Social Networking Applications? To quantify transparency, the literature presents many frequency-domain metrics within the context of telerobotics and haptics. In a linear analysis, for example, Lawrence defines the transmitted impedance ratio as the ratio of the transmitted impedance, Zt , over the impedance of the environment, Ze, in a teleoperation device

Wide-area overlay networking to manage science DMZ accelerated flows

HARDWARE-IN-THE-LOOP simulation  HILS  is a tool that combines the high fidelity of physical prototyping with the cost effectiveness of model-based simulation  It strongly promotes concurrent system engineering and has therefore become indispensable in many application areas, such as automotive aerospace  manufacturing Wide-area overlay networking to manage science DMZ accelerated flows robotics and defense To fully exploit the benefits of HILS, it may be desirable to integrate multiple HILS setups Recent efforts have focused on achieving this integration over the Internet to allow for integration of setups that the current on the transformer primary and secondary, respectively.

A bigger ringing spike occurs in the dead time zero-voltage length if the duty cycle is not  for the noninterleaving arrangement due to the fact that the energy stored in the leakage inductance oscillates with the other parasitic elements in the circuit. The improved arrangement has the best high-frequency property in the ringing problem, which can bring low switching losses and low EMI problem. The are geographically dispersed and unfeasible to couple physically An important concept with Internet-distributed HILS  IDHILS is transparency a measure of how close the dynamics of the distributed system are to those of the directly coupled system, a measure of fidelity.

Wide-area overlay networking to manage science DMZ accelerated flow

Wide-area overlay networking to manage science DMZ accelerated flows A high transparency indicates that the dynamics do not change significantly when the system is distributed over the Internet, and is therefore desired. The transparency metrics proposed in the literature are reviewed in detail in Section and are useful for linear deterministic systems. However, systems will, in general, be nonlinear and stochastic, as will be illustrated by the sample system considered in this work. Therefore, the first goal of this paper is to develop a time-domain statistical analysis of transparency that will enable the handling of nonlinear stochastic systems. Using this analysis, the second goal of this paper is to experimentally compare the relative impact of two sources of degradation in transparency. The first one is the Internet’s quality of service QoS., the intrinsic delay, jitter, and loss associated with the Internet. Much of the delay is related to routing and processing in the network. Jittermeans that the delay is variable, and loss occurs because not every packet sent through the Internet  necessarily arrives at its destination. The adverse effects of delay on stability and transparency of dynamic systems are well known and present challenges that are still subject to research, in the field of teleoperation. Wide-area overlay networking to manage science DMZ accelerated flows Thus, maintaining stability and transparency despite delay, jitter, and loss is amajor challenge in using the Internet to couple HILS setups. The second source of degradation in transparency that is considered in this paper is distributed real-time simulation.

In general, the distributed sites will employ models that need to be co-simulated in real time. This is typically done by communicating the variables at the coupling points over the Internet. Such a communication will inevitably introduce sampling effects, which will degrade transparency. In addition, it will not be possible to ensure the accuracy theoretically established for the numerical integration scheme employed on a given site without having access to all the states and state derivatives of the othe sites. Wide-area overlay networking to manage science DMZ accelerated flows Therefore, such an integration of the models will cause a degradation of simulation accuracy, and may reduce transparency. Since this point, compared to time delay issues, has received less attention in the literature, it may be less obvious, and hence, will be illustrated on a simple example in Section. This second goal is important to identify the major cause of transparency degradation

Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks

Winding arrangements can also, in part, bring an optimal behavior in the tradeoffs without any sacrifices, which play an important role in optimizing PT. Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks In the following work, four typical winding arrangements are compared to illustrate their advantages and disadvantages. individually shows their models. A full-bridge buck dc–dc converter employing these PTs has been built with the specifications presented in Model A Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks: Noninterleaving has very high ac resistance and leakage inductance, compared with other arrangements, as . However, it merits the stray capacitance because of only one intersection between the primary and the secondary.

Table II shows that the lowest stray capacitance can be achieved in the noninterleaving arrangement.Model BSpectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networksBased on ac resistance and leakage inductance are dramatically reduced in general full-interleaving A lower MMF ratio m causes a weaker proximity effect in the adjacent layers, which contributes a lower ac resistance. The energy associated with leakage inductance is reduced due to the fact that the magnetizing force is reduced in each layer, as shown in However, seven intersections between the primary and the secondary can be found, which is caused by a higher stray capacitance.

Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical network

As shown in Table II, the stray capacitance in is almost ten times that in noninterleaving. Model is another kind of fully interleaving arrangement, because the MMF ratios m in each layer are still equal to, as shown in Comparing with the general full-interleaving, Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks it has similar ac resistance and leakage inductance, because their MMF distributions have the same functions. However, it is very noteworthy that stray capacitance is getting better without sacrificing any other behaviors leakage inductance or ac resistance due to the fact that fewer intersections four between the primary and the secondary can be found. Model Model d represents an improved interleaving arrangement that constructs the top layer paralleling with the bottom layer and then in series with the other turns of the primary, so that the MMF ratio m can further be reduced. shows the analytical MMF distribution of  . Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks Since the unavoidable error of impedances on the top and bottom layers, the currents in each branch are probably not equal, and hence, the MMF ratios m may not be Anyhow, a lower MMF ratio m below  can be achieved.

Thereby, as shown in, a lower ac resistance appears in a high-frequency situation, and a slow increasing tendency can clearly be identified when the frequency is above. The most impressive thing is that not only ac resistance and leakage inductance can be reduced but stray capacitance can also be benefited, compared with other interleaving arrangements Spectrum defragmentation implementation based on software defined networking SDN in flexi-grid optical networks The paper proposed that quadruple interleaving also achieves by splitting the secondary. However, the even turn ratio is limited in this construction, and the stray capacitance might not be improved. the measured impedance with opening secondary winding in, and  arrangements, respectively. The noninterleaving has the best parallel LC resonance frequency magnetizing inductance stray capacitance of primary, and the worst case occurs in the full-interleaving. Because the magnetizing inductance in the four arrangements are the same, the parallel LC resonance frequencies reflect the magnitude of the stray capacitors as the same results, as shown in Table kW full-bridge converter prototype employing the improved PT structure has been constructed, as shown in show the plots of the transformer primary voltage, primary winding current, and secondary voltage and current in different winding arrangements. In these figures, represent the voltage across the transformer

Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisioning

Combining with the analysis of winding loss, core loss, leakage inductance, and stray capacitance, some overlapping occur in affecting each other, as described here. Number of turns N. The lesser the N, the lesser the winding loss but the more the core loss that will be produced due to higher peak flux density; furthermore, a lower leakage inductance can also be obtained. The stray capacitance is also probably benefited, depending on the winding configuration. The choice of N will have to be a key in optimizing design.

Excitation frequency f. Although a higher frequency can cause a lower core loss as mentioned before, ac resistance will be increased due to eddy current effect. The leakage inductance slightly decreases with increased frequency because of a small change in the permeability of conductors. The designed frequency has to be considered the carrying capacity of the switching devices and the switching losses. Thickness of conductors h and insulator h. Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisioning The optimal thickness h for winding loss has been introduced in Section A larger h also causes a larger leakage inductance.

Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisionings

There is a contradiction for hΔ between the leakage inductance and the stray capacitance. The larger the hΔ, the larger the leakage inductance and the smaller the capacitance. It is impossible to achieve both low values by optimizing the physical parameters. The only way to obtain optimal behaviors of both leakage inductance andstray capacitance is to change the winding configurations. Considering the loss in parasitic elements, a low leakage inductance has priority over a low stray capacitance in high-current low-voltage application. Reversely, Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisioning in lowcurrent high-voltage application, a low stray capacitance has to be required rather than a low leakage inductance. Core geometry. For a certain number of turns, a bigger cross section Ae of core can bring a lower core loss, but the length of windings will have to be sacrificed, which increases the winding loss.

In order to facilitate a clear understanding of tradeoffs in turn ratio transformer will be analyzed as an example of simplification. The assumed specification of a full-bridge buck dc–dc converter with primary excitation of duty cycle, and a switching frequency of is used. Full interleaving is employed to make the MMF ratios m in each layer equal to According to the analysis of winding loss and mm-thick conductors are chosen in this example. The authors write a small program in virtue of Matlab to figure out the tradeoffs. shows that the total loss, the winding loss, and the core loss vary as a function of different numbers of turns when the other parameters are fixed. The red curve and blue curve individually represent the total loss for the core. The core losses decrease with the increased number of turns; this is due to the fact that the flux density is reduced. The winding losses, however, increase, because higher dc resistances are achieved. Apparently, an optimal number of turns in this example can be found. In addition, reflects a relationship between losses and frequency. Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisioning An optimal frequency for the total loss can be found as well. Taken together as the intersection points between the red line and the blue line illuminate the tradeoff also caused by the core geometry. Holistic Modeling and Performance Evaluation for Converged Network-Cloud Service Provisioning Following the analysis of ac resistance and core loss, the relationship between the losses and the number of turns N can be written

Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking

In fact, stray capacitances significantly affect the magnetic component performance in such a way that the current Equivalent circuit of the transformer model with self-capacitances and mutual capacitance and with a single lumped stray capacitance referred to the primary side. waveform on the excitation side would be distorted and the overall efficiency of converters would be decreased. Subjected to high-voltage stresses, Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking stray capacitance between windings causes leakage currents and consequently contributes EMI Considering an equivalent model of two-winding PT, as and Cpso are used to account for the self-capacitances of the primary and the secondary windings and the mutual capacitance between the two windings, respectively.

It is desirable to keep Cpso to be as small as possible, and good EMI results could be achieved. The equivalent capacitors referred to the primary side can approximately be determined by the following relations where k is the turns ratio. Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking The mutual capacitance Cpso due to the electrical coupling between the primary and secondary windings can approximately be measured directly by shorting both primary and secondary sides. The single equivalent capacitance referred to the primary side Cstr in can approximately be computed In the case of PTs, static layer capacitances can easily be estimated since the windings consist of parallel and flat conductors.

Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networkings

Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking The formula for the capacitance between two parallel conductive plates is given by where ε0 is the permittivity of free air space, and εr is the relative permittivity of the material. In addition, S represents the overlapping surface area of the two plates. The distance between the plates is shows an equivalent potential distribution model in dependence on the internal two layers of the same winding with opposite directions. Assuming that the potential distribution along the turns linearly varies, where n is the number of turns in each layer, and Ui represents the potential in each pair of plates. U is the voltage potential between the two terminations of the winding. The turn-to-turn capacitance can be ignored by comparing with the layer-tolayer capacitance due to a very small overlapping surface area. The total energy associated with the electric field in the two layers is given by The equivalent capacitance of the same winding can be expressed If there are m layers in series for the same winding as the same connection the overall equivalent capacitance could be deduced by equating the electric energy stored in all layer capacitors for the connection in which provides an equivalent constant voltage distribution along the turns in each layer. Hereby, a lower equivalent capacitance Co in the winding with the same direction has been shown.

Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking Regarding stray capacitance in different windings, the voltage difference between the high potential side and the low potential side can be expressed by with the assumption that the linear distributed voltage along different windings is still valid. With the same procedure, the equivalent stray capacitance referred to the primary winding can be deduced by Based on the preceding analysis for the stray capacitance, the optimal solutions can be concluded as follows reducing static layer capacitance by enhancing the distance or lowering the overlapping surface area between the two conductor plates; Cooperative cache sharing among ISPs for reducing inter-ISP transit cost in content-centric networking reducing the number of turns in each layer or/and increasing the number of layers reducing the number of intersections between the primary and the secondary arranging the winding configurations to obtain the minimal energy associated with the electric field.

Ther is Not all the magnetic flux generated by ac current excitation on the primary side follows the magnetic circuit and link with the secondary winding. The flux linkage between two windings or parts of the same winding is never complete. Some flux leaks from the core and returns to the air, winding layers, and insulator layers; thus, these flux causes imperfect coupling. The energy associated with leakage inductance can be calculated according to analytical MMF distribution and energy distribution. From the differential volume of each turn is therefore, the total energy is the sum of the energy stored in each elementary layer, which can be given by where lw is the length of each turn, bw is the width of each turn, and h represents the thickness of each winding layer. Understanding Members’ Attachment to Social Networking Sites: An Empirical Investigation of Three Theories The thickness dx is situated at a distance x from the inner surface of conductor. The field strength H depends on the number of ampere turns linked by the leak flux path. Since the flux rapidly disperses on leaving the winding, the associated energy is much reduced, and the reluctance of the path within the magnetic core can be ignored, compared with that of the path in the windings; thus, the flux path can be expressed by the width bw rather than the full closed flux path According Understanding Members’ Attachment to Social Networking Sites: An Empirical Investigation of Three Theories to for where are the lay thicknesses of the primary and the secondary, respectively, and hΔ is the height of the insulator layer. However, as for fully interleaving arrangement in with the same approach, leakage inductance can be deduced as follows: Apparently, the fully interleaving arrangement provides a significant advantage in reducing leakage inductance. As a conclusion, aside from winding structures, leakage inductance in PT can be changed by adjusting some physical parameters, including conductor thickness and its width, insulator thickness, and the number of turns. As a parasitic element exists in transformers, the leakage inductance causes the main switch current at the device input to vary at a low slope between zero and the rated value and reduces the rate of commutation between the output diodes. In addition, the stored energy in the leakage inductance leads to a generation of voltage spikes on the main switch, which, aside from creating electromagnetic interference EMI problems, increases the switching losses and lowers the efficiency. Understanding Members’ Attachment to Social Networking Sites: Understanding Members’ Attachment to Social Networking Sites: An Empirical Investigation of Three Theories An Empirical Investigation of Three Theories However, in some applications such as a phase-shift-modulated soft-switching dc/dc converter, the magnitude of leakage inductance determines the achievable load range under zero-voltage-switching operation, and a relatively large leakage Understanding Members’ Attachment to Social Networking Sites: An Empirical Investigation of Three Theories inductance is desirable. In order to avoid an additional magnetic component, a leakage layer with low permeability has been inserted between the primary and the secondary to form a resonant inductor Stray capacitance in designing PT cannot be ignored. The potential between turns, between winding layers, and between windings and core create this parasitic element. In most papers about optimizing PT, the main Understanding Members’ Attachment to Social Networking Sites: An Empirical Investigation of Three Theories purpose is to reduce leakage inductances, but stray capacitances have not seriously been considered.