No description available.

Characterization and modeling of devices at high drive levels often requires specialized equipment and measurement techniques. Many large-signal devices will never have traditional nonlinear models because model development is expensive and time-consuming. Due to the complexity of the device or the size of the application market, nonlinear modeling efforts may not be cost effective. Scattering parameters, widely used for small-signal passive and active device characterization, have received only cursory consideration for large-signal nonlinear device characterization due to technical and theoretical issues. We review the theory of S-parameters, active device characterization, and previous efforts to use S-parameters with large-signal nonlinear devices. A robust, calibrated vector-measurement system is used to obtain device scattering parameters as a function of drive level. The unique measurement system architecture allows meaningful scattering parameter measurements of large-signal nonlinear devices, overcoming limitations reported by previous researchers. A three-port S-parameter device model, with a nonlinear reflection coefficient terminating the third port, can be extracted from scattering parameters measured as a function of drive level. This three-port model provides excellent agreement with device measurements across a wide range of drive conditions. The model is used to simulate load-pull data for various drive levels which are compared to measured data. / Master of Science

This research deals with the modeling and control of a plasticating twin screw extruder (TSE) that will be used to obtain consistent product quality. The TSE is a widely used process technology for compounding raw polymers. Compounding creates a polymer with improved properties that satisfy the demand of modern plastic applications. Modeling and control of a TSE is challenging because of its high nonlinearity, inherent time delay, and multiple interactive dynamic behavior. A complete methodology is proposed in this thesis to design an advanced control scheme for a TSE. This methodology was used to develop a model predictive control scheme for a laboratory scale plasticating TSE and to implement the control scheme in real-time. The TSE has a processing length of 925 mm and a length to screw diameter ratio (L/D) of 37. High density polyethylenes with different melt indices were used as processing materials. Manipulated variables and disturbance variables were selected based on knowledge of the process. Controlled variables were selected using a selection method that includes a steady state correlation between process output variables and product quality variables, and dynamic considerations. Two process output variables, melt temperature (Tm) at the die and melt pressure (Pm) at the die, were selected as controlled variables. A new modeling approach was proposed to develop grey box models based on excitation in the extruder screw speed (N), one of the manipulated variables. The extruder was excited using a predesigned random binary sequence (RBS) type excitation in N and nonlinear models relating Tm and Pm to N were developed using this approach. System identification techniques were used to obtain model parameters. The obtained models have an autoregressive moving average with exogenous (ARMAX) input structure and the models explain the physics of the extrusion process successfully. The TSE was also excited using a predesigned RBS in the feed rate (F) as a manipulated variable. Models relating Tm and Pm to F were developed using a classical system identification technique; both models have ARMAX structures. The model between Pm and F was found to give excellent prediction for data obtained from a stair type excitation, indicating that the obtained models provide a good representation of the dynamics of the twin screw extruder. Analysis of the TSE open loop process indicated two manipulated variables, N and F, and two controlled variables, Tm and Pm. Thus, a model predictive controller (MPC) was designed using the developed models for this 2X2 system and implemented in real-time. The performance of the MPC was studied by checking its set-point tracking ability. The robustness of the MPC was also examined by imposing external disturbances. Finally, a multimodel operating regime was used to model Tm and N. The operating regime was divided based on the screw speed, N. Local models were developed using system identification techniques. The global model was developed by combining local models using fuzzy logic methodology. Simulated results showed excellent response of Tm for a wide operating range. A similar approach was used to design a global nonlinear proportional-integral controller (n-PI) and a nonlinear MPC (n-MPC). Both the controllers showed good set-points tracking ability over the operating range. The multiple model-based MPC showed smooth transitions from one operating regime to another operating regime. / Process Control

This study utilized, for the first time, the d18Osw as a tracer to investigate the seasonal variations of circulation in the Taiwan Strait (TS), which is the predominant sea passage with an average depth of 60 m connecting the East China Sea (ECS) and the South China Sea (SCS). The result shows that the circulation system in TS is mainly influenced by the inter-mixing among the China Coastal Water (CCW), the SCS water (SCSW), and the Kuroshio Water (KW). In spring, the KW dominates in TS, whereas the CCW is still observed in northwest TS. During the summer, SCSW replaces the KW and becomes the major water type in the TS, yet the KW is found to be restricted in the southwest part and the bottom of the TS. Due to the larger discharge from rivers (mainly the Yangtz River), the CCW has a more extensive distribution in the TS in summer than other seasons. In fall and winter, the CCW occupies the northern part of TS due to the stronger northeastern monsoon which limits the intrusion of the KW through the Luzon Strait to the northern TS. The two distinct water types inevitably form a front in the central TS. The hydrographic variations at Penghu Channel (PHC) were also explored in this study. The d18Osw indicates that the perennial intrusion of the KW into the PHC is varying throughout different seasons. This intrusion is found strongest in fall and winter. In summer, the upper layer of PHC is occupied chiefly by SCSW, while the KW remains at the bottom layer in PHC. By including an additional inflow of 0.5Sv from TS to ECS, this study further reconstructed a box model of the ECS, which was previously furnished by Lin(1999). The new estimates suggest that ~0.38*104 km3/year of the Kuroshio surface water (0-50m) and ~1.54*104 km3/year of the upwelled Kuroshio subsurface water (50-150m) are transported to the ECS, while ~3.83*104 km3/year of the ECS water are exported to the western Pacific Ocean.

No description available.

In this thesis a quadrotor is studied and a linear model is derived using grey-box estimation, a discipline in system identification where a model structure based on physical relations is used and the parameters are estimated using input-output measurements. From IMU measurements and measured PWM signals to the four motors, a direct approach using the prediction-error method is applied. To investigate the impact of the unknown controller the two-stage method, a closed-loop approach in system identification,  is applied as well. The direct approach was enough for estimating the model parameters. The resulting model manages to simulate the major dynamics for the vertical acceleration and the angular rates well enough  for future control design.

The uptake of carbon in the ocean may change with global warming, which can have significant feedback effects on the climate. To investigate the change, a two box ocean model has been used to simulate the temperature and carbon content in the atmosphere, in a shallow and deep layer of the ocean, when doubling the amount of carbon dioxide in the atmosphere. The results were compared with a low-resolution Earth system model called cGENIE, which is a more complex model. The two box ocean model showed an increase of temperature in the ocean by 1.2°C. A similar response was simulated in cGENIE where the shallow ocean (0-80 meters depth) increased by 0.22°C. The deep ocean (down to 3600 meters) warmed by 0.48°C. The carbon content followed the same behavior in both models. Carbon dioxide in the atmosphere was absorbed by the ocean after the initial doubling. As the ocean absorbed carbon dioxide the radiative forcing decreased again, reducing the warming effect. The two box model is a conceptual model of the carbon cycle in the ocean that can provide a useful illustration of the key balance of carbon in the climate system, despite the many simplifications.

Today’s power systems are based on a centralised system and distribution networks that are considered as passive terminations of transmission networks. The high penetration of Distributed Generation (DG) at the distribution network level has created many challenges for this structure. New tools and simulation approaches are required to address the subject and to quantify the dynamic characteristics of the system. A distribution network or part of it with DG, Active Distribution Network Cell (ADNC), can no longer be considered as passive. An equivalent dynamic model of ADNC is therefore extremely important, as it enables power system operators to quickly estimate the impact of disturbances on the power system’s dynamic behaviour. A dynamic equivalent model works by reducing both the complexity of the distribution network and the computation time required to run a full dynamic simulation. It offers a simple and low-order representation of the system without compromising distribution network dynamic characteristics and behaviour as seen by the external grid. This research aims to develop a dynamic equivalent model for ADNC. It focuses on the development of an equivalent model by exploiting system identification theory, i.e. the grey-box approach. The first part of the thesis gives a comprehensive overview and background of the dynamic equivalent techniques for power systems. The research was inspired by previous work on system identification theory. It further demonstrates the theoretical concept of system identification, system load modelling and the modelling of major types of DG. An equivalent model is developed, guided by the assumed structure of the system. The problem of equivalent model development is then formulated under a system identification framework, and the parameter estimation methodology is proposed. The validation results of the effectiveness and accuracy of the developed model are presented. This includes the estimation of the parameter model using a clustering algorithm to improve the computational performance and the analysis of transformer impedance effects on the ADNC responses. The evaluation of probability density function, eigenvalue analysis and parameter sensitivity analysis for the model parameters are also presented. Typical model parameters for different network topologies and configurations are identified. Finally, the developed equivalent model is used for a large power system application. The accuracy and robustness of the developed equivalent model are demonstrated under small and large disturbance studies for various types of fault and different fault locations.

<p>Hur resonerar potentiella kunder kring inköp av produkten som ens företag tillhandahåller? En av de främsta frågorna hos en marknadsförare, men också en fråga som är aktuell i vår marknadsekonomi i stort. Konsumentbeteende är därför ett givet fält inom företagsekonomin. Men hur går det till när konsumenten är ett företag? Vilka aspekter är viktiga och varför? Vilka marknadsföringsinsatser bör genomföras utifrån denna adderade förståelse? Det är utgångspunkten för denna uppsats. För att kunna svara på dessa frågor har en ny konsumentbeteendemodell utarbetats, vilket skett utifrån befintliga teorier inom konsumentbeteende och då särskilt den så kallade svarta lådan-modellen. Målet med modellen är att kasta ljus över relevanta aspekter och processer som beaktas och gås igenom i samband med inköp inom ett företag.</p><p>Studien avser inköp av kaffemaskiner avgränsat till potentiella kunder för kaffe- och kaffemaskinleverantören Premium Coffee och dess produkt Nespresso, med betoning på större företag i Stockholmsområdet. Informationsinsamlingen har skett med hjälp av enkäter per mail.</p><p>Utifrån vår empiri och analys av denna har vi gjort antagandet att priset är den absolut mest styrande faktorn för gruppen. Det verkar dock som om man kan tänka sig att betala mer om detta ”mer” är konkret och efterfrågat. Hit verkar inte en godare smak och möjligheter till varumärkesbyggande finnas utan snarare värden som miljövänlighet, kvalité och hållbarhet. Vidare kan vi också anta att inköp nästan alltid sker via anbud.</p><p>Utifrån detta kan man dra slutsatser kring vilka insatser som skulle kunna genomföras. Hit hör att berättiga sitt ändå högre pris, men också utforma ett bättre svar på miljöfrågorna och en uppväxling av positioneringsaktiviteterna.</p> / <p>How do potential customers reason concerning the purchase of a product supplied? This is one of the main issues for a marketer, but also an issue that is current in our market economy at large. Consumer behaviour is a given field of business economy. But how does this work when the consumer is a company? What marketing efforts should be implemented based on these new findings? This is the starting point of this essay. To answer these questions, a new consumer model, has therefore, been developed, which is based on existing theories of consumer behaviour and in particular the so-called black box model. The goal of the model is to shed light on the relevant aspects and processes that are reviewed and considered in connection to the purchase of an enterprise.</p><p>The study relates to the purchase of coffee machines to the limited prospects for the coffee and coffee machine supplier Coffee Premium, with an emphasis on large companies in the Stockholm region. Information has been collected using questionnaires by mail.</p><p>Based on our empirical data, we can assume that price is the absolutely most governing factor for the group. They are however willing to pay for more if this "more" is defined and demanded. It does not seem as a better taste and the ability to strengthen the brand are aspects considered as such but rather aspects as quality and durability. Furthermore, we can also assume that the purchase is almost always done through tenders.</p><p>Based on this we are able to draw a number of conclusions about what actions that could be implemented. These include, for example, to review the pricing, combined with the aim to justify the higher prices, but also design a better response to environmental issues and an up shift of positioning activities.</p>

Hur resonerar potentiella kunder kring inköp av produkten som ens företag tillhandahåller? En av de främsta frågorna hos en marknadsförare, men också en fråga som är aktuell i vår marknadsekonomi i stort. Konsumentbeteende är därför ett givet fält inom företagsekonomin. Men hur går det till när konsumenten är ett företag? Vilka aspekter är viktiga och varför? Vilka marknadsföringsinsatser bör genomföras utifrån denna adderade förståelse? Det är utgångspunkten för denna uppsats. För att kunna svara på dessa frågor har en ny konsumentbeteendemodell utarbetats, vilket skett utifrån befintliga teorier inom konsumentbeteende och då särskilt den så kallade svarta lådan-modellen. Målet med modellen är att kasta ljus över relevanta aspekter och processer som beaktas och gås igenom i samband med inköp inom ett företag. Studien avser inköp av kaffemaskiner avgränsat till potentiella kunder för kaffe- och kaffemaskinleverantören Premium Coffee och dess produkt Nespresso, med betoning på större företag i Stockholmsområdet. Informationsinsamlingen har skett med hjälp av enkäter per mail. Utifrån vår empiri och analys av denna har vi gjort antagandet att priset är den absolut mest styrande faktorn för gruppen. Det verkar dock som om man kan tänka sig att betala mer om detta ”mer” är konkret och efterfrågat. Hit verkar inte en godare smak och möjligheter till varumärkesbyggande finnas utan snarare värden som miljövänlighet, kvalité och hållbarhet. Vidare kan vi också anta att inköp nästan alltid sker via anbud. Utifrån detta kan man dra slutsatser kring vilka insatser som skulle kunna genomföras. Hit hör att berättiga sitt ändå högre pris, men också utforma ett bättre svar på miljöfrågorna och en uppväxling av positioneringsaktiviteterna. / How do potential customers reason concerning the purchase of a product supplied? This is one of the main issues for a marketer, but also an issue that is current in our market economy at large. Consumer behaviour is a given field of business economy. But how does this work when the consumer is a company? What marketing efforts should be implemented based on these new findings? This is the starting point of this essay. To answer these questions, a new consumer model, has therefore, been developed, which is based on existing theories of consumer behaviour and in particular the so-called black box model. The goal of the model is to shed light on the relevant aspects and processes that are reviewed and considered in connection to the purchase of an enterprise. The study relates to the purchase of coffee machines to the limited prospects for the coffee and coffee machine supplier Coffee Premium, with an emphasis on large companies in the Stockholm region. Information has been collected using questionnaires by mail. Based on our empirical data, we can assume that price is the absolutely most governing factor for the group. They are however willing to pay for more if this "more" is defined and demanded. It does not seem as a better taste and the ability to strengthen the brand are aspects considered as such but rather aspects as quality and durability. Furthermore, we can also assume that the purchase is almost always done through tenders. Based on this we are able to draw a number of conclusions about what actions that could be implemented. These include, for example, to review the pricing, combined with the aim to justify the higher prices, but also design a better response to environmental issues and an up shift of positioning activities.