446 research outputs found
Fuzzy model based predictive control of chemical processes.
No full textThe past few years have witnessed a rapid growth in the use of fuzzy logic
controllers for the control of processes which are complex and ill-defined. These
control systems, inspired by the approximate reasoning capabilities of humans
under conditions of uncertainty and imprecision, consist of linguistic 'if-then' rules
which depend on fuzzy set theory for representation and evaluation using
computers. Even though the fuzzy rules can be built from purely heuristic
knowledge such as a human operator's control strategy, a number of difficulties
face the designer of such systems. For any reasonably complex chemical process,
the number of rules required to ensure adequate control in all operating regions
may be extremely large. Eliciting all of these rules and ensuring their consistency
and completeness can be a daunting task.
An alternative to modelling the operator's response is to model the process
and then to incorporate the process model into some sort of model-based control
scheme. The concept of Model Based Predictive Control (MB PC) has been
heralded as one of the most significant control developments in recent years. It is
now widely used in the chemical and petrochemical industry and it continues to
attract a considerable amount of research. Its popularity can be attributed to its
many remarkable features and its open methodology. The wide range of choice of
model structures, prediction horizon and optimisation criteria allows the control
designer to easily tailor MBPC to his application. Features sought from such
controllers include better performance, ease of tuning, greater robustness, ability
to handle process constraints, dead time compensation and the ability to control
nonminimum phase and open loop unstable processes. The concept of MBPC is
not restricted to single-input single-output (SISO) processes. Feedforward action
can be introduced easily for compensation of measurable disturbances and the use
of state-space model formulation allows the approach to be generalised easily to
multi-input multi-output (MIMO) systems. Although many different MBPC schemes have emerged, linear process models derived from input-output data are
often used either explicitly to predict future process behaviour and/or implicitly to
calculate the control action even though many chemical processes exhibit
nonlinear process behaviour. It is well-recognised that the inherent nonlinearity of
many chemical processes presents a challenging control problem, especially where
quality and/or economic performance are important demands.
In this thesis, MBPC is incorporated into a nonlinear fuzzy modelling
framework. Even though a control algorithm based on a 1-step ahead predictive
control strategy has initially been examined, subsequent studies focus on
determining the optimal controller output using a long-range predictive control
strategy. The fuzzy modelling method proposed by Takagi and Sugeno has been
used throughout the thesis. This modelling method uses fuzzy inference to
combine the outputs of a number of auto-regressive linear sub-models to construct
an overall nonlinear process model. The method provides a more compact model
(hence requiring less computations) than fuzzy modelling methods using relational
arrays. It also provides an improvement in modelling accuracy and effectively
overcomes the problems arising from incomplete models that characterise
relational fuzzy models.
Difficulties in using traditional cost function and optimisation techniques
with fuzzy models have led other researchers to use numerical search techniques
for determining the controller output. The emphasis in this thesis has been on
computationally efficient analytically derived control algorithms. The performance
of the proposed control system is examined using simulations of the liquid level in
a tank, a continuous stirred tank reactor (CSTR) system, a binary distillation
column and a forced circulation evaporator system. The results demonstrate the
ability of the proposed system to outperform more traditional control systems. The
results also show that inspite of the greatly reduced computational requirement of
our proposed controller, it is possible to equal or better the performance of some
of the other fuzzy model based control systems that have been proposed in the
literature.
It is also shown in this thesis that the proposed control algorithm can be
easily extended to address the requirements of time-varying processes and
processes requiring compensation for disturbance inputs and dead times. The
application of the control system to multivariable processes and the ability to
incorporate explicit constraints in the optimisation process are also demonstrated
A Randomised Control Trial and Comparative Analysis of Multi-Dimensional Learning Tools in Anatomy
No full textResearch was funded by the Cakmak Lab and the University of Otago, Otago Medical School. Author notes: These authors contributed equally: Ben Kei Daniel and Mustafa Asil. Contributions: Conception and Design of Study: Y.C. and C.W.; Design of materials: Y.C. and C.W.; Randomization of participants: P.K.; Acquisition of data: C.W.; Data analysis and interpretation: Y.C., M.A., B.D. and C.W.; Drafting of manuscript and/or critical revision: C.W., Y.C., M.A., B.D. and P.K.; All authors read and approved the final manuscript.Peer reviewe
Economists, institutions, and trade restrictions : a review article
No full textA review article on the work of"practitioners of contemporary economic analysis of trade restrictions", this report focuses on three questions : a) are there holes in the case of free trade? B) Why are trade restrictions imposed, and c) how do US policy actions and those of other nations interact ? On the first question, though difficult to identify when there is profit to be captured by trade intervention and to design an appropriate trade intervention policy, capturing a strategic sector and economic rents is important to equity holders without necessarily being of much significance to the economy as a whole. Further, on trade restrictions, these are often aimed at non economic objectives, since economic sanctions tend to be used only when other instruments fail. As for the interaction of US policy actions versus other nations, they are a manifestation of protectionist legislation in the US Congress and perhaps indictments against GATT as wrong headed.TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research,Rules of Origin,Trade Policy
(Post) Socialism Country's Political Choice of the Economic Reform: Hungary, PRC and Poland
No full text本文主要想回答一個問題：對於正在脫離社會主義經濟體制的轉型國家而言，究竟會選擇什麼樣的策略來進行經濟改革？為什麼？過去一般以正當性變項來對此進行解釋。筆者除反駁此項論述外，並提出一個假設命題：經政初始階段，執政者與舊政權的政經網絡關係決定經改策略的選擇，如果執政者繼承前政權的政經網絡，將偏向採取漸進改革，而如果執政者的政經網絡與舊政權越不同，則越有可能採取震盪療法。並以匈牙利、中國大陸與波蘭為例來驗證此假說。The article is mainly to answer a question: To those (Post) Socialism Countries, which Transition from Socialism, What kind of strategy they will choose to push economic reform? Why? In the past, most scholars thought communism government didn't dare to take actions of the shock therapy and privatize because communism government wanted to maintain the legitimacy of ideology. While a new authority that has the legitimacy of democracy would take steps of the shock therapy. This paper doesn't agree with this discourse, and adduces a hypothetic: In the beginning of the economic reform, the strategy of economic reform opportunity decides on new authorities and the past governor's relationship. If the new authorities follow former relationship, they will take actions of the gradualism. On the contrary, the more different relationship of the new authorities has, the more chances they will take actions of the shock therapy. Then the author will take Hungary, PRC and Poland for example to prove this hypothetic. In order to answer above questions, this paper will divide the article into six parts: the first part is preface to declare the author's question and viewpoint; the second part is to discuss the shock therapy and gradualism, then review correlative articles to lead the writer's hypothetic; the third part will take Hungary for instance to controvert the legitimacy discourse and review the author's hypothetic; the fourth and the fifth part will take PRC and Poland for instance to review the author's hypothetic; the sixth part is the conclusion
Semi-analytical approaches for the prediction of the noise produced by ducted wind turbines
No full textThe integration of wind turbines into urban environments is a challenging task due to the reduced wind speed and high turbulence levels caused by the surface resistance, as well as limited spacing. If a specific building arrangement is explored, an improve ment in wind speed can be obtained. This would be especially beneficial for tall build ings where a wind turbine can be placed on the roof, side, or through a duct. However, the main problem associated with the integration of wind turbines is the acoustic an noyance. Therefore, the focus of this thesis is twofold. First, a robust, accurate, and low computational cost numerical methodology is proposed to predict the trailing edge noise for a ducted wind turbine. Second, a measurement device is developed to acquire noise emitted by a rotating machine where the duct surface cannot be altered. An inves tigation of the incoming flow on the noise emitted by a building-integrated wind turbine is conducted by different aerodynamic roughness lengths…Wind Energ
Processing Risk In Asset Management: Exploring The Boundaries Of Risk Based Optimization Under Uncertainty For An Energy Infrastructure Asset Manager
No full textIn the liberalized energy market Distribution Network Operators (DNOs) are confronted with income reductions by the regulator. The common response to this challenge is the implementation of asset management, which can be regarded as systematically applying Cost Benefit Analysis (CBA) to the risks in the networks. In short, this is Risk Based Optimization (RBO). However, application of RBO is mostly limited to interventions on individual assets like upgrades, replacements and maintenance. Whether RBO is feasible for higher levels of aggregation like the portfolio of interventions or even the whole system was not clear. The unavoidable subjectivity and uncertainty associated with risk decision making could threaten the acceptance of decision outcomes. The experiments conducted in this research reveal that there are no fundamental barriers to risk based optimization of the whole system. Embracing uncertainty and subjectivity allows for relatively simple tools, as the tools do not need to be more accurate than our knowledge of the future. The condition for this to work is that the rational RBO decisions are embedded in a well-designed sociotechnical process. A systematic implementation of RBO on all levels (individual assets, portfolios of interventions and the whole system) results in a reduction of the total costs of the system (expenditure plus residual risk) of about 20%.Engineering Systems and Services, Section Energy & IndustryTechnology, Policy and Managemen
A Sub-1V, Micropower Bandgap Reference
No full textBandgap references are used in many ICs to produce ‘stable’ and ‘temperature-independent’ voltage. This thesis describes a sub-1V bandgap reference in 40 nm and 0.16 µm CMOS technologies that is functional from -40 oC to 125 oC. Traditionally, BJT based references are commonly used, but produce an output voltage of 1.2 V and are not suitable for supply voltages below 1 V. Previously area-intensive solutions that were based on resistive sub-divisions were used to realize sub-1V references. In this work, a compact and low power ‘bandgap’ reference was implemented in standard CMOS technology using a device known as a Dynamic Threshold MOSFET (DTMOST). 20 chips have been taped out in NXP 0.16 µm CMOS technology (C14) and packaged in Ceramic DIL packages. A 3 ? spread of 1.25 % is observed. The chips work down to a supply of 0.9 V and occupy 0.05 mm2. Also, a prototype has been designed in a 40 nm CMOS process and post-layout simulations have been performed. The chip works down to a supply of 0.8 V and occupies 0.05 mm2. Simulated 3? spread is 3.7 %. The total current consumption for the chips in both technologies is less than 4 µA in the worst case corners.Electronic InstrumentationElectrical Engineering (Microelectronics)Electrical Engineering, Mathematics and Computer Scienc
Responsive Suburbia: Dwelling and working in IJBurg
No full textA housing project comprised of 72 units is located in IJ Burg— a new suburb east from the center of Amsterdam. More specifically, the project sits on a man-made island called Steigereiland North, on a ‘left-over’ green strip of land. Two types of dwellings (A and B) are disseminated around the site forming various permeable blocks of living and working units. These apartments consist of free-standing, row, and semi-detached typologies, depending on their arrangement and orientation. The capacity of these units to grow and change over time is a key feature of this project. The project has an additional activity strip between the waterside and the housing fabric border which will aid to serve as a lively catalyst for the neighbourhood. This ‘mat’ consists of landscaping and supplementary functions such as: tennis courts, a soccer field, playgrounds, picnic zones, pergolas, a climbing wall, a dance studio, and storage facilities. The newly-added layer of economical, community-driven activities reinvigorates IJ Burg. Introducing light production as well as the creative and working classes into the urban fabric will also result in an extrovert and well-functioning community.At Home in the City, AmsterdamArchitecture and DwellingArchitectur
When Do JONSWAP Spectra Lead to Soliton Gases in Deep Water Conditions?
No full textWhen a large number of solitons dominates the dynamics of a system, scientists describe this collective behaviour of solitons as a soliton gas. Soliton gases are currently the subject of intense practical and theoretical investigations. The existence of soliton gases has been confirmed in experiments, but is not clear what kind of sea states might lead to soliton gases. Therefore, in order to determine the wave parameters for sea states that lead to soliton gases, large numbers of surface wave elevations are generated by the well-known JOSNWAP model in this paper. Here, we only discuss soliton gases in deep water governed by the nonlinear Schrödinger (NLS) equation. The nonlinear Fourier transform (NFT) with vanishing boundary conditions is applied to the simulated ocean surface waves. The resulting nonlinear Fourier spectrum is used to calculate the energy of radiation waves and solitons. We investigate which JONSWAP parameters result in sea states that can be characterized as soliton gases, and find that a large Phillip’s parameter α, a large peak enhancement parameter γ and a short peak period TP are important factors for soliton gas conditions. The results allow researchers to estimate how likely soliton gases are in deep waters. Furthermore, we find that the appearance of rogue waves is slightly increased in highly nonlinear sea states with soliton gas-like conditions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Michel VerhaegenTeam Sander Wahl
UWB Antenna Design for Polarimetric Imaging Radar
No full textImaging radar has become a keen research topic in recent years. UWB technology provides many advantages to imaging radar such as fine resolution and high power efficiency. The performance of a UWB imaging radar can be further improved by applying polarimetric diversity. The polarimetric signature of objects can be used to enhance the quality of target recognition. Like any other wireless systems, antennas are key factors of radar systems. The focus of this thesis is to develop a dual polarized antenna for UWB imaging radar. An antenna element was designed for the Ku-band and an impedance bandwidth from 8 GHz to 24 GHz was achieved. An orthogonal coax-to-coplanar transition has been developed during this project and this transition is used to feed the antenna element. The antenna elements are successfully applied in two different array configurations. It is demonstrated that these sub-arrays have over 100% fractional bandwidth, good impedance matching, linear phase (almost constant group delay) and uni-directional pattern. These aspects collectively account for the novelty in design. In future, these sub-arrays will be implemented inside a complete array structure of UWB imaging radar.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
- …
