Vortex dynamics and states of artificially layered superconducting films with correlated defects

Linear resistances and $IV$-characteristics have been measured over a wide range in the parameter space of the mixed phase of multilayered a-TaGe/Ge films. Three films with varying interlayer coupling and correlated defects oriented at an angle $\approx 25$ from the film normal were investigated. Experimental data were analyzed within vortex glass models and a second order phase transition from a resistive vortex liquid to a pinned glass phase. Various vortex phases including changes from three to two dimensional behavior depending on anisotropy have been identified. Careful analysis of $IV$-characteristics in the glass phases revealed a distinctive $T$ and $H$-dependence of the glass exponent $\mu$. The vortex dynamics in the Bose-glass phase does not follow the predicted behavior for excitations of vortex kinks or loops.Comment: 16 pages, 10 figures, 3 table

The Discrete Voronoi game in ℝ\u3csup\u3e2\u3c/sup\u3e

In this paper we study the last round of the discrete Voronoi game in ℝ2, a problem which is also of independent interest in competitive facility location. The game consists of two players P1 and P2, and a finite set U of users in the plane. The players have already placed two disjoint sets of facilities F and S, respectively, in the plane. The game begins with P1 placing a new facility followed by P2 placing another facility, and the objective of both the players is to maximize their own total payoffs. In this paper we propose polynomial time algorithms for determining the optimal strategies of both the players for arbitrarily located existing facilities F and S. We show that in the L1 and the L∞ metrics, the optimal strategy of P2, given any placement of P1, can be found in O(n log n) time, and the optimal strategy of P1 can be found in O(n5 log n) time. In the L2 metric, the optimal strategies of P2 and P1 can be obtained in O(n2) and O(n2) and O(n8) times, respectively

Indoor Positioning Using Acoustic Pseudo-Noise Based Time Difference of Arrival

The Global Positioning System (GPS) provides good precision on a global scale, but is not suitable for indoor applications. Indoor positioning systems (IPS) aim to provide high precision position information in an indoor environment. IPS has huge market opportunity with a growing number of commercial and consumer applications especially as Internet of Things (IoT) develops. This paper studies an IPS approach using audible sound and pseudo-noise (PN) based time difference of arrival (TDoA). The system’s infrastructure consists of synchronized speakers. The object to be located, or receiver, extracts TDoA information and uses multilateration to calculate its position. The proposed IPS utilizes sound waves since they travel much slower compared to electromagnetic waves, allowing for easier measurements. Additionally, the audible spectrum has a large availability of low directivity speakers and microphones allowing for a large coverage area compared to highly directive ultrasonic transceivers. This paper experimentally evaluates the feasibility of the proposed IPS

Computing a flattest, undercut-free parting line for a convex polyhedron, with application to mold design

AbstractA parting line for a polyhedron is a closed curve on its surface, which identifies the two halves of the polyhedron for which mold-boxes must be made. A parting line is undercut-free if the two halves that it generates do not contain facets that obstruct the de-molding of the polyhedron. Computing an undercut-free parting line that is as “flat” as possible is an important problem in mold design. In this paper, algorithms are presented to compute such a parting line for a convex polyhedron, based on different flatness criteria

Maximizing Voronoi Regions of a Set of Points Enclosed in a Circle with Applications to Facility Location

In this paper we introduce an optimization problem which involves maximization of the area of Voronoi regions of a set of points placed inside a circle. Such optimization goals arise in facility location problems consisting of both mobile and stationary facilities. Let ψ be a circular path through which mobile service stations are plying, and S be a set of n stationary facilities (points) inside ψ. A demand point p is served from a mobile facility plying along ψ if the distance of p from the boundary of ψ is less than that from any member in S. On the other hand, the demand point p is served from a stationary facility p i  ∈ S if the distance of p from p i is less than or equal to the distance of p from all other members in S and also from the boundary of ψ. The objective is to place the stationary facilities in S, inside ψ, such that the total area served by them is maximized. We consider a restricted version of this problem where the members in S are placed equidistantly from the center o of ψ. It is shown that the maximum area is obtained when the members in S lie on the vertices of a regular n-gon, with its circumcenter at o. The distance of the members in S from o and the optimum area increases with n, and at the limit approaches the radius and the area of the circle ψ, respectively. We also consider another variation of this problem where a set of n points is placed inside ψ, and the task is to locate a new point q inside ψ such that the area of the Voronoi region of q is maximized. We give an exact solution of this problem when n = 1 and a (1 − ε)-approximation algorithm for the general case

Designing the Urban Microclimate:

This doctoral thesis presents research on the integration and transfer of knowledge from the specialized field of urban microclimatology into the generic field of urban design. Both fields are studied in order to identify crosslinks and reveal gaps. The main research question of the research is: How can the design of urban neighbourhoods contribute to microclimates that support physical well-being and what kind of information and form of presentation does the urban designer need in order to make design decisions regarding such urban microclimates? This question consists of two parts, which are addressed separately in the first two parts of the dissertation. Part 1 concerns an assessment of relevant knowledge on urban design by literature review, followed by a field study into the use of expert information in the urban design process. Part 2 discusses the influence of the urban environment on its microclimate and, consequently, the living quality of its inhabitants – both by means of literature review. Combined, Parts 1 and 2 serve as a basis for a framework for a design-decision support tool, which is discussed in Part 3. This tool is proposed as a means to integrate knowledge of the urban microclimate into the urban design process, bridging an observed gap. Urban design is concerned with shaping the physical environment to facilitate urban life in all its aspects. This is a complex task, which requires the integration and translation of different stakeholder interests into a proposition for the realization of physical-spatial constructs in the urban environment. Such a proposition comprises different planning elements in the following categories: spatial-functional organization, city plan, public space design and rules for architecture. During the design process, the urban designer has to deal with incomplete, often contradictory and/or changing constraints and quality demands as well as other uncertainties. He/ she handles this complexity by starting with a small selection of constraints, iteratively working to a design solution by incorporating an increasing number of constraints. The selection of constraints is subjective, depending on the design frame of the individual designer. In order to make design decisions, the urban designer requires diverse information. To establish how urban designers collect information and which formats and information levels they prefer, field research among Dutch urban designers was carried out. This consisted of a series of exploratory interviews and an online questionnaire. The results indicate that dissemination of expert knowledge to urban design should be focused on the orientation and sketch phases of the design process and should provide different layers of detail, using mainly visual information accompanied by explanatory text. The results furthermore show a remarkable discrepancy between the assigned significance of the urban microclimate for urban design and the frequency of inquiry on this topic; almost all interviewees and respondents consider the subject to be important, but a majority of them seldom collect information on it. This signifies a gap in the knowledge transfer process. It is important to bridge this gap, because the urban microclimate has a significant impact on the physical well-being of people. All components of the urban microclimate – solar radiation, daylight, wind, air quality and sound – affect the physical well-being of people, whether separately or in conjunction. Some of these effects are immediate, such as heat stress and noise annoyance; others develop over a longer period of overexposure or underexposure, such as pulmonary and respiratory diseases. Some cause discomfort, for example sleep disturbance; others can be life- threatening, such as heat stroke or skin and lung cancer. It is therefore vital that the urban microclimate is given considerable attention in the urban design process. The urban microclimate is to a large extent influenced by the city’s morphology, materialization and landscaping. This influence is exerted through different physical principles, such as reflection, absorption and evapotranspiration. Basic knowledge on how and to what extent the urban environment affects the urban microclimate and of the underlying physical principles, supported by design guidelines and examples/ reference projects, will enable urban designers to estimate the effects of their design choices on the microclimate themselves better, and help them create conditions for urban microclimates that favour physical well-being. In order to make this information available to the urban designer in a way that corresponds to his/her working process, a framework for a design-decision support tool was set up. Requirements regarding form and function were derived from the field of urban design, while requirements regarding content were derived from the field of urban microclimatology. The tool is proposed to be a web-based knowledge base, consisting of five main menu categories: “climate elements”, “plan elements”, “principles”, “guidelines” and “example projects”. Each category provides access to separate pages for underlying items, containing different layers of information, from general to detailed, that can be accessed through collapse menus or click-through functions. Hyperlinks between related items are provided to support different ways to access information. The main menu further gives access to background information on physical well-being and regulations and standards. Separate item pages can be added to a ‘shopping cart’, enabling customised information selection for a specific design at hand. Providing the necessary content for the tool requires further translation of expert knowledge into design information as well as additional research regarding: the plain and simple formulation of physical phenomena related to the urban environment; the integration of expert knowledge of separate microclimatological elements; the incongruity of parameters in microclimatological studies and urban design plan elements; and the presentation of information consistent with design and (design) communication purposes as opposed to evaluation purposes. To illustrate how expert studies can be rendered into design information, the impact of three selected plan elements - Floor Space Index (FSI), Ground Space Index (GSI) and orientation - on solar irradiation and wind was examined with the aid of numerical simulation tools. The results of the calculations for both climate elements were integrated in order to identify conflicts and matches. The emphasis of the study lay on showing trends and generating generic knowledge. Such knowledge is required to fill the proposed design-decision support tool with content. Answering the main research question, it can be concluded that various aspects relating to the morphology, materialization and landscaping of urban neighbourhoods can be employed to create conditions for a distinctive microclimate; urban microclimates often deviate substantially from the regional climate, and even vary within a few meters. Designing urban microclimates needs to be done with care as they affect the physical well-being of people significantly. In order to be able to do this, the urban designer needs information that ties in with his/her way of working and cognitive process. However, expert knowledge from the field of urban microclimatology does not fulfil this requirement and needs to be translated to information for urban design purposes. Aiming to give direction to this translation and facilitate the dissemination of expert urban microclimate knowledge to the urban design process, this research proposes a framework for a design-decision support tool. Requirements for the framework were derived from both the field of urban design and the field of urban microclimatology. A tool created according to the proposed framework will enable urban designers to practice climate-sensitive urban design, and, thus contribute to the physical well-being of people