For an ordinary dc-dc converter, the switch is triggered by the use pulse width modulated (PWM) signal. The duty cycle is normally tuned to get the required output voltage from the converter. However, with the change in the input to the converter, it becomes hard to keep in touch with the changes to provide the maximum power to the load . With the use of the MPPT algorithm, the maximum power can easily be tracking as the MPPT tracker is technically configured to respond to the changes in the input. The use of MPPT algorithm along with the dc-dc converter makes it possible to extract maximum power from TEG. In this study, we have applied a boost dc-dc converter topology. A boost converter topology converts from a low voltage to higher voltage and can either be controlled by PWM or MPPT, with the load current smaller than the input current. It is the most commonly used in the middle and low voltage level conversion networks. It is suitable for TEG with unstable internal resistance and output voltage . 3.1. Extremum Seeking Control MPPT Technique
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In the literature there are mainly four types of extremum seeking schemes: perturbation based, sliding mode based, numerical optimization based, and gradient based extremum seeking algorithms. In the perturbation based extremum seeking algorithms studied in  - , a perturbation is added to the search signal. By observing the effect of the pertur- bation on the performance function measurement, it is determined whether to increase or decrease the search signal to reach its optimum value and hence maximize (or minimize) the performance function. It is assumed that the shape, i.e. the gradient of the perfor- mance function is unknown. In the seminal paper of Krstic and Wang , stability proof for this type of extremum seeking control is given with the tools of averaging and singular perturbations.
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Parameter to tune MPP. The turbine power is the cost function for the ES algorithm, and electrical frequency and voltage amplitude of the stator of IG are controlled through the MC to reach desired closed-loop performance. As a result of including the inner loop, the overall design has faster response time, and further more magnetic saturation of the IG is avoided. In comparison with model-based designs, ES better handles model uncertainty in the turbine power map, resulting in improved power extraction. To the best of our knowledge, this is the first work in the literature that combines the MPPT with nonlinear control design that has good performance robustness to uncertainty, and faster transient performance, allowing for power tracking under rapidly varying wind conditions. The rest of this paper is organized as follows. An introduction to modelling of the WECS with concentration on the squirrel-cage IG dynamics in stationary reference frame and the MC is discussed in Section II. Our nonlinear controller design is discussed in Section III, and the ES algorithm in Section IV. Simulation results to verify the effectiveness of the proposed scheme are presented in Section V, and our conclusion is presented in Section VI.
Renewable energy applications have brought a new fo- cus on the capabilities of ES algorithms. In this article we present applications of ES in two types of energy conver- sion systems for renewable energy sources: wind and solar energy. The goal for both is maximum power point track- ing (MPPT), or, the extraction of the maximum feasible energy from the system under uncertainty and in the ab- sence of a priori modeling knowledge about the systems. For the wind energy conversion system (WECS), MPPT is performed by tuning the set point for the turbine speed using scalar ES. The outer ES loop tunes the turbine speed to maximize power capture for all wind speeds within the subrated power operating conditions. The inner-loop non- linear control maintains fast transient response through a matrix converter, by regulating the electrical frequency and voltage amplitude of the stator of the (squirrel-cage) induction generator. Simulation results are presented to show the effectiveness of the proposed design.
power. Unfortunately, the technique suffers of the interference of sunshine variations and a certain complexity in fixing the range of speed sweep. The design of an energy efficient solar pumping system requires to match the motor–pump load curve with the maximum power point locus (on the power vs voltage curve) of the PV source. For small systems, based on DC motors, a DC/DC converter between the PV source and the converter is always inevitably required, since a perfect match is difficult to obtain through a direct connection. A good example is reported in , that uses an hybrid buck/buck- boost DC/DC for a low-power PV pumping application. The power converter is obviously unavoidable when using AC motors. In ,  an additional DC/DC converter is used to boost the DC bus voltage of the induction motor drive. This solution enables operation at higher speeds, but at the expense of an increased circuit complexity. In , a single stage solution is proposed, where an open-end winding induction machine is driven by a dual three-phase converter. This reduces voltage ratings but increases the components count in the conversion system. In general, the design of a stand–alone solar pumping system should guarantee maximum operating efficiency, by foreseeing the implementation of a suitable MPP tracking scheme. A comprehensive review of MPP trackers (MPPTs) for stand–alone PV systems can be found in – . In this paper, a novel stand–alone solar pumping system with a isotropic PMSM is presented. The speed reference is continuously adjusted in the direction that implies an increased power demand to the PV array. This action is performed by an ad–hoc MPPT that operates according to the extremum seeking control principle –, which recalls the Ripple Correlation (RC) scheme . The main difference consists on how the perturbation of the DC bus voltage, required to steer the working point toward the MPP, is generated. Rather than using the intrinsic voltage ripple of the switched power supply, as done in the ripple correlation scheme, in the proposed solution an artificial ripple is generated by purposely injecting a sinusoidal current perturbation in the PMSM. The paper is organised as follows. The architecture of the proposed MPPT is introduced in Sec. II, along with the basic modelling required to understand its working principle. The fundamental dynamics of the PV power regulation process is analysed in Sec. III, with an emphasis on the determination of the stable operating points. The control scheme is described in Sec. IV. The proposed solution has been tested both by simulations and on a full–size prototype, consisting of a 1 kW PV array plus a 5 kW PMSM that drives a virtual load pump, obtained by a 3.7 kW induction motor. The results are reported in Sec. V and Sec. VI. Final conclusions and remarks are reported in Sec. VII.
wind energy conversion systems (WECS) has caught a big attention from early days. The methods widely used are model based power optimization algorithms as the outer loop and linear control methods in the inner loop. The method of extremum seeking control is a non model based optimization concept to extract maximum power from WECS in their subrated region. Induction generators are used widely in WECS since they are relatively inexpensive, robust and require a little maintenance.. When operated using vector control techniques fast dynamic response and accurate torque control is obtained with the help of a matrix converter. In this paper, inner loop nonlinear control based on the principle of field oriented control (FOC) and feedback linearization is used along with maximum power point tracking (MPPT) in the outer loop. The proposed MPPT method is Fractional Order Extremum Seeking Control (FOESC).The convergence speed of FOESC is faster than the Integer Order ESC. Simulation results are presented to show the effectiveness of the proposed model .
Maximizing the power capture is an important issue to the turbines that are installed in low wind speed area. In this paper, we focused on the modeling and control of variable speed wind turbine that is composed of two-mass drive train, a Squirrel Cage Induction Generator (SCIG), and voltage source converter control by Space Vector Pulse Width Modulation (SPVWM). To achieve Maximum Power Point Tracking (MPPT), the reference speed to the generator is searched via Extremum Seeking Control (ESC). ESC was designed for wind turbine region II operation based on dither-modulation scheme. ESC is a model-free method that has the ability to increase the captured power in real time under turbulent wind without any requirement for wind measure- ments. The controller is designed in two loops. In the outer loop, ESC is used to set a desired reference speed to PI controller to regulate the speed of the generator and extract the maximum electrical power. The inner control loop is based on Indirect Field Orientation Control (IFOC) to decouple the cur- rents. Finally, Particle Swarm Optimization (PSO) is used to obtain the op- timal PI parameters. Simulation and control of the system have been accom- plished using MATLAB/Simulink 2014.
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Capability control is the fourth managerial topic: minimizing role ambiguity and role conflict can contribute to reducing emotional exhaustion, which consequently will contribute to increasing job satisfaction and commitment to the organization . Employee training that lower role ambiguity could reduce as a result opportunistic behaviors (Ramaswami, 2002) however, sometimes is advisable letting emotionally exhausted salesperson leaves the team and replace him/her with someone who is more emotionally in tune with the organization (Babakus et al. 1999). Moreover, salesperson selling skills’ positive effect on performance in a customer orientation environment justifies the role of coaching and training as a means to improve these capabilities. Training of junior salespeople or other groups with weaker selling skills, should focus on identifying needs, matching products to needs, and translating features to benefits, rather than in customer-orientation, which would be a better long-term investment, but will not succeed until the salesperson acquires the required capabilities (Wachner et al., 2009). Sales manager training to improve activity and capability control skills, as well as the thorough evaluation of salespeople organizational citizenship behavior, should be a focus for sales executives concerned with enhancing salesperson in-role performance. The reciprocity between observed organizational support, with organizational citizenship and organizational commitment, highlights the need for managers to increase the perception and actual existence of organizational support to the sales teams (Piercy et al., 2006). Sales control systems should deploy in a complementary manner, in order not to lead to undercuts with each other. If a control system goal concurs with those of others, it is likely to decrease the affective commitment and the task clarity, which likely will result in a lower performance and a lower customer orientation (Joshi and Randall, 2001). Based on Fang et al.’s study (2005), in a low-context country (U.S.) when end-outputs are the main concern of managers, higher levels of outcome control along with fairly demanding specific goals seems to be the best option. When behavioral performance is the central subject, high rates of capability and activity control together with mild and nonspecific goals should be the choice. However, in a high-context culture (China), when managers seek end- results, an outcome control plus moderately hard, nonspecific objectives would be pertinent, while capability and activity control, with easy, generic goals, with high levels of participation, should be adopted when behavioral performance is the priority of management.
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information will be more highlighted (Gosselin, 2006). The ABC is a revolution in costing systems, and can be used as a powerful tool for solving various management problems (Rahnamay Roodposhti, 2009). However, benefiting from these advantage may not be possible regardless of behavioral considerations (Bahram, et. al, 2008). The most important effective behavioral structures in ABC is the culture of managers, the method of evaluating managers and staff and how to create control mechanisms that should be considered in designing these systems (Namazi,1998). Considering the practical applications of ABC in industrial or even services units, and across different countries as well as the movement of TSE listed industries towards the establishment of the management accounting and ABC system, prior to any action, the assessment of the information needs is necessary; otherwise, a system that is perfectly designed will not be able to help executives of TSE listed companies to optimally capture the resources when they need. As far as the researchers are concerned, a study has not independently reviewed the information needs of managers to the ABC due to the lack of familiarity and knowledge of the ABC systems, its advantages and abilities, lack of training and skills in this field and so on (Bahram Far, et. al, 2008).
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women could not be confirmed. On the contrary, this study shows that women seeking an abortion have received more information about birth control than the women in the control group, but they still do not seem to have better knowledge about contraceptives, including number of methods known, expected efficiency of different contraceptives, and whether oral contraceptives affect the fertility after termination of use. Similarly, there was no difference in contraceptive knowledge between women who had received information from their doctor or other health care provider about contraceptives and women who had not received information. These findings together indicate that the information about birth control given by doctors or other health care providers is insufficient and that contraceptive counseling needs to be improved. This is in line with findings from high resource countries, such as Sweden, where the rate of repeated abortion exceeds 40% and the contraceptive counseling in relation to the abortion visits most often is clearly insufficient. 16 Thus, it seems as if
Abstract: The introduction of function extremum promotes the development of calculus, which is the prerequisite and important condition for the development and development of many mathematical ideas. Except for extreme problems in social life or science and technology, the issue of cost in economic issues, the shortest distance in mathematics problem can be solved by the function extreme value thought. However, because the extreme value problem is not well described, learners cannot easily observe and learn. This paper takes the uniform speed and uniform acceleration and descent in the descent model as an example. In the uniform acceleration, the dichotomy is introduced to solve the function extremum problem. Through MATLAB simulation, the position of the steepest descent point is found intuitively and relevant conclusions are obtained. It is hoped that the research process of the problem can be helpful to the study of refractive problems, and it is hoped that the visually intuitive simulation results can enable learners to understand the descent model more objectively.
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Abstract — To make glowworm swarm optimization (GSO) algorithm solve multi-extremum global optimization more effectively, taking into consideration the disadvantages and some unique advantages of GSO, the paper proposes a hybrid algorithm of Broyden–Fletcher–Goldfarb– Shanno (BFGS) algorithm and GSO, i.e., BFGS-GSO by adding BFGS local optimization operator in it, which can solve the problems effectively such as unsatisfying solving precision, and slow convergence speed in the later period. Through the simulation of eight standard test functions, the effectiveness of the algorithm is tested and improved. It proves that the improved BFGS-GSO abounds in better multi-extremum global optimization in comparison with the basic GSO.
gradient algorithms of search extremum of nonlinear functions with application of some operators of smoothing: an algorithm with the approximating spherical hyper- paraboloid and an algorithm with the approximating elliptical hyper-paraboloid. Are adduced: the statement of the problem, the algorithm of construction of operator of smoothing, the general scheme of search. The verification of the operation of the algorithms is illustrated in test examples. Are researched the problems of convergence of algorithms using operators of smoothing.
This numerical (CFD) study investigates the transient natural convection of water near its density extremum within a vertical cylindrical geometry. A non-Boussinesq approach is employed and the results are compared to previous studies. Distilled water having initial temperature of 8 º C is used as the medium, while the entire cavity is insulated. This experimental chamber is enclosed within another glass cylinder, and coolant fluid at a fixed temperature of 0 º C is pumped continuously through the annular region between the cylinders. Results of cooling curve measurements and the flow patterns present good agreement. From the resulting numerical outputs, it is evident that the density inversion of water has a significant influence on the natural convection in the cavity.
A general theory of SR, not confined to the conventional bistable case @ 6 # , was introduced in @ 7 # . It was predicted @ 8,9 # on this basis that SR could also occur in monostable systems @ 10 # . In this perception of the phenomenon, SR is to be an- ticipated in any system whose fluctuation spectrum in the absence of a periodic signal displays at least one narrow peak that grows quickly enough with increasing noise intensity. In the particular case considered in @ 8,9 # , the SR was associated with zero-dispersion peaks @ 12–15 # in systems whose eigen- frequency as a function of energy possesses an extremum: to distinguish it from conventional bistable SR, it was named zero-dispersion stochastic resonance ~ ZDSR ! .
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Because feedback seeking is proactive in nature, self-initiated, and complicated by the fact that employees need to put themselves in the vulnerable position of having to approach and seek feedback from their supervisors, employees face potential risks (e.g., losing face, appearing unconfident or incompetent, damaging their reputation) that may deter them from seeking feedback. Accordingly, the quality of the perceived social exchange relationship an employee has with his or her supervisor (i.e., leader–member exchange, or LMX hereinafter) (Graen and Uhl-Bien 1995) becomes a critical factor that can mitigate the potential risks associated with feedback seeking and ultimately lead to more (and more productive) feedback seeking. We posit that frontline employees 1 experience tension and conflict due to the many, and often competing, job demands they face when interacting with customers (e.g., the demand for greater
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When network devices communicate with many other devices, the workload required of the CPUs on the devices can be burdensome. For example, in a large flat (switched) network, broadcast packets are burdensome. A broadcast packet interrupts the CPU on each device within the broadcast domain, and demands processing time on every device for which a protocol understanding for that broadcast is installed. This includes routers, workstations, and servers. Another potential problem with nonhierarchical networks, besides broadcast packets, is the CPU workload required for routers to communicate with many other routers and process numerous route advertisements. A hierarchical network design methodology lets you design a modular topology that limits the number of communicating routers. Using a hierarchical model can help you minimize costs. You can purchase the appropriate internetworking devices for each layer of the hierarchy, thus avoiding spending money on unnecessary features for a layer. Also, the modular nature of the hierarchical design model enables accurate capacity planning within each layer of the hierarchy, thus reducing wasted bandwidth. Network management responsibility and network management systems can be distributed to the different layers of a modular network architecture to control management costs.
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Globally, the percentage of the adult population with an active headache disorder is 46%, out of which, 11% have migraine, tension-type headache constitute 42% [1,2]. On the World Health Organization's ranking and the Global Burden of Disease Study 2010 (GBD2010) the Tension-Type Headache (TTH) and migraine were reported to be the most prevalent disorders worldwide [1,3]. Despite the high prevalence of headache, half of the patients may not seek treatment or they try self remedies . Headache care professionals have expressed the concern of high treatment gap and a global campaign was initiated by World Health Organization . Empirically, myths, misconceptions and poor knowledge about headache along with low socioeconomic status are the major barriers to help seeking . Help-seeking is defined as a problem focused, planned behaviour, involving interpersonal interaction with a qualified health-care professional . Experimental or correlational research reveals that people are less likely to seek help for problems that are highly ego-central and non-normative , and when autonomy is threatened . Inadequate emotional control, insufficient social & financial resources, cost of help, lack of awareness of remedial options, concerns about confrontation, and not wanting to share personal problems (self-disclosure) may obstruct the help seeking [9-11].
Abstract. Recent work has suggested that in highly cor- related systems, such as sandpiles, turbulent fluids, ignited trees in forest fires and magnetization in a ferromagnet close to a critical point, the probability distribution of a global quantity (i.e. total energy dissipation, magnetization and so forth) that has been normalized to the first two moments fol- lows a specific non-Gaussian curve. This curve follows a form suggested by extremum statistics, which is specified by a single parameter a (a = 1 corresponds to the Fisher-Tippett Type I (“Gumbel”) distribution).
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Taken into account these features, the control system (functional diagram is shown in Figure-4) on the first cycle of material feeding which is determined by the appropriate signal of the SCADA system, identifies the drift of the static map by providing training search by using extremum memorizing method at a constant counterweight motion speed and reverse zone defined the necessary immunity. The trajectory of the drift (dotted curve) at this motion is the sliding average value of the integrated control actions applied to the actuators. In the process of teaching it is memorizing the current values of vibration (in the memory block M1) and the integrated value of control actions (in the memory M2), which after the end of the grinding cycle (which is defined in the mass comparator CM with equal masses of feed and discharged material, measured by feed sensor FS and discharge sensor DS, respectively) are averaged and stored their median values instead of using the current by using drift identification block IDB.