Mathematical models and routing algorithms for CAD technological preparation of cutting processes

Resource-conscious technologies for cutting sheet material include the ICP and ECP technologies that allow for aligning fragments of the contours of cutouts. In this work, we show the mathematical model for the problem of cutting out parts with these technologies and algorithms for finding cutting tool routes that satisfy technological constraints. We give a solution for the problem of representing a cutting plan as a plane graph G = (V,F,E), which is a homeomorphic image of the cutting plan. This has let us formalize technological constraints on the trajectory of cutting the parts according to the cutting plan and propose a series of algorithms for constructing a route in the graph G = (V,F,E), which is an image of an admissible trajectory. Using known coordinates of the preimages of vertices of graph G = (V,F,E) and the locations of fragments of the cutting plan that are preimages of edges of graph G = (V,F,E), the resulting route in the graph G = (V,E) can be interpreted as the cutting tool’s trajectory.The proposed algorithms for finding routes in a connected graph G have polynomial computational complexity. To find the optimal route in an unconnected graph G, we need to solve, for every dividing face f of graph G, a travelling salesman problem on the set of faces incident to f.     

Working with connective flow: how smartphone use is evolving in practice

Smartphones, those handheld devices that connect us via telephone and the Internet to virtually everyone and everything in the world, are becoming an integral part of everyday life. While there are significant individual and collective benefits from being more connected, there are also concerns associated with ‘always on’ work practices. This paper reports on a two-phase case study of smartphone users in a global financial services firm comparing the use of smartphones and their impact on work over time. We found that mobile communication technology practices have evolved within a relatively short (5-year) period of time as users seek to manage connectivity across work and non-work spaces. Disconnecting from work is no longer possible, nor desirable, for many users, who exercise choice (agency), switching between work and non-work interactions to regulate the connective flow across multiple connective media.     

Symmetric Masks for In-fill Pixel Interpolation on Discrete <Emphasis Type="Italic">p</Emphasis>:<Emphasis Type="Italic">q</Emphasis> Lattices

A 2D p:q lattice contains image intensity entries at pixels located at regular, staggered intervals that are spaced p rows and q columns apart. Zero values appear at all other intermediate grid locations. We consider here the construction, for any given p:q, of convolution masks to smoothly and uniformly interpolate values across all of the intermediate grid positions. The conventional pixel-filling approach is to allocate intensities proportional to the fractional area that each grid pixel occupies inside the boundaries formed by the p:q lines. However, these area-based masks have asymmetric boundaries, flat interior values and may be odd or even in size. Where edges, lines or points are in-filled, area-based p:q masks imprint intensity patterns that recall p:q because the shape of those masks is asymmetric and depends on p:q. We aim to remove these “memory” artefacts by building symmetric p:q masks. We show here that smoother, symmetric versions of such convolution masks exist. The coefficients of the masks constructed here have simple integer values whose distribution is derived purely from symmetry considerations. We have application for these symmetric interpolation masks as part of a precise image rotation algorithm which disguises the rotation angle, as well as to smooth back-projected values when performing discrete tomographic image reconstruction.     

The art,poetics, and grammar of technological innovation as practice,process, and performance

Usually technological innovation and artistic work are seen as very distinctive practices, and innovation of technologies is understood in terms of design and human intention. Moreover, thinking about technological innovation is usually categorized as “technical” and disconnected from thinking about culture and the social. Drawing on work by Dewey, Heidegger, Latour, and Wittgenstein and responding to academic discourses about craft and design, ethics and responsible innovation, transdisciplinarity, and participation, this essay questions these assumptions and examines what kind of knowledge and practices are involved in art and technological innovation. It argues that technological innovation is indeed “technical”, but, if conceptualized as techne, can be understood as art and performance. It is argued that in practice, innovative techne is not only connected to episteme as theoretical knowledge but also has the mode of poiesis: it is not just the outcome of human design and intention but rather involves a performative process in which there is a “dialogue” between form and matter and between creator and environment in which humans and non-humans participate. Moreover, this art is embedded in broader cultural patterns and grammars—ultimately a ‘form of life’—that shape and make possible the innovation. In that sense, there is no gap between science and society—a gap that is often assumed in STS and in, for instance, discourse on responsible innovation. It is concluded that technology and art were only relatively recently and unfortunately divorced, conceptually, but that in practices and performances they were always linked. If we understand technological innovation as a poetic, participative, and performative process, then bringing together technological innovation and artistic practices should not be seen as a marginal or luxury project but instead as one that is central, necessary, and vital for cultural-technological change. This conceptualization supports not only a different approach to innovation but has also social-transformative potential and has implications for ethics of technology and responsible innovation.     

From Work to Life and Back Again: Examining the Digitally-Mediated Work/Life Practices of a Group of Knowledge Workers

This paper presents the results of a qualitative study exploring the technologically-mediated practices of work/life balancing, blurring and boundary-setting of a cohort of professionals in knowledge-intensive roles in Sheffield, a regional city in Northern England. It contributes to a growing body of CSCW research on the complex interweaving of work and non-work tasks, demands and on the boundaries that can be supported or hindered by digital technologies. In the paper, we detail how a cohort of 26 professionals in knowledge-intensive roles devise diverse strategies for handling work and non-work in light of a set of interconnected forces, and we argue that boundary dissolving and work-life blurring, and not just boundary setting and “balancing”, are essential resources within such strategies. We also show how boundary sculpting pertains not only to work pervading personal spheres of life, but also the opposite, and that establishing, softening and dissolving boundaries are practiced to handle situations when the personal seeps into professional life.     

Moving the centre to design social media in rural Africa

Efforts to design voice-based, social media platforms for low-literacy communities in developing countries have not widened access to information in the ways intended. This article links this to who describes the relations that constitute personhood and how these relations are expressed in designing and deploying systems. I make these links oriented by critique in human–computer interaction that design continues a history of colonialism and embeds meanings in media that disrupt existing communication practices. I explore how we translated ‘logics’ about sociality through logics located outside of the rural South African community that we targeted for design and deployment. The system aimed to enable inhabitants to record, store and share voice files using a portable, communally owned display. I describe how we engaged with inhabitants, to understand needs, and represented and abstracted from encounters to articulate requirements, which we translated into statements about technology. Use of the system was not as predicted. My analysis suggests that certain writing cultures, embedded in translations, reify knowledge, disembody voices and neglect the rhythms of life. This biases social media towards individualist logics and limits affordances for forms, genres and other elements of communication that contribute to sociality. Thus, I propose oral practices offer oppositional power in designing digital bubbles to support human togetherness and that we can enrich design by moving the centre—a phrase taken from Ng?g? wa Thiong’o (Moving the centre: the struggle for cultural freedoms, James Currey, London, 1993) who insists that liberation from colonialism requires plural sites of creativity. To realize this potential, we need radically different approaches that enable symmetrical translation.     

Improving validity and reliability in longitudinal case study timelines

Management Information Systems researchers rely on longitudinal case studies to investigate a variety of phenomena such as systems development, system implementation, and information systems-related organizational change. However, insufficient attention has been spent on understanding the unique validity and reliability issues related to the timeline that is either explicitly or implicitly required in a longitudinal case study. In this paper, we address three forms of longitudinal timeline validity: time unit validity (which deals with the question of how to segment the timeline – weeks, months, years, etc.), time boundaries validity (which deals with the question of how long the timeline should be), and time period validity (which deals with the issue of which periods should be in the timeline). We also examine timeline reliability, which deals with the question of whether another judge would have assigned the same events to the same sequence, categories, and periods. Techniques to address these forms of longitudinal timeline validity include: matching the unit of time to the pace of change to address time unit validity, use of member checks and formal case study protocol to address time boundaries validity, analysis of archival data to address both time unit and time boundary validity, and the use of triangulation to address timeline reliability. The techniques should be used to design, conduct, and report longitudinal case studies that contain valid and reliable conclusions.     

Using neural networks to integrate structural analysis package and optimization package

To solve structural optimization problems, it is necessary to integrate a structural analysis package and an optimization package. Since most structural analysis packages suffer from closeness of system, it is very difficult to integrate it with an optimization package. To overcome the difficulty, we propose a possible alternative, DAMDO, which integrate Design, Analysis, Modeling, Definition, and Optimization phases into an integration environment as follows. (1) Design first generate many possible structural design alternatives. Each design alternative consists of many design variables X. (2) Analysis employ the structural analysis software to analyze all structural design alternatives to obtain their internal forces and displacements. They are the response variables Y. (3) Modeling employ artificial neural networks to build model Y = f(X) to obtain the relationship functions between the design variables X and the response variables Y. (4) Definition employ the design variables X and the response variables Y to define the objective function and constraint functions. (5) Optimization employ the optimization software to solve the optimization problem consisting of the objective function and the constraint functions to produce the optimum design variables X*. Optimization of truss structures was used to validate the DAMDO approach. The empirical results show that the truss optimization problems can be solved by the DAMDO approach, which employ neural networks to integrate the structural analysis package and optimization package without requiring direct integration of the two packages. This approach is promising in many engineering optimization domains which need to couple an analysis package and an optimization one to obtain the optimum solutions.     

Information systems development: a perspective on the challenge of evolutionary complexity

This conceptual paper proposes that the methodical approach to information system development leads us to design systems that are unable to deal with the challenge of evolutionary complexity. This is examined through the use of a systemic framework that describes evolutionary complexity in terms of interaction between the concepts of distinction/connection and variation/selection. In applying these concepts to the social world we are led to conclude (a) that social regularities are emergent and not a priori given and (b) that these emergent regularities are constantly shifting and evolving. This has strong implications for the methodical approach to development, which we argue assumes social structures, mechanisms and processes as ‘invariant regularities’ that only have to be revealed to be understood. This difference leads methodical development to produce static systems that have to work in a dynamic world. The paper concludes by outlining a proposition in response to the challenge of evolutionary complexity, one where design is considered as an inherently ongoing process.     

Irrevocable-choice algorithms for sampling from a stream

The problem of sampling from data streams has attracted significant interest in the last decade. Whichever sampling criteria is considered (uniform sample, maximally diverse sample, etc.), the challenges stem from the relatively small amount of memory available in the face of unbounded streams. In this work we consider an interesting extension of this problem, the framework of which is stimulated by recent improvements in sensing technologies and robotics. In some situations it is not only possible to digitally sense some aspects of the world, but to physically capture a tangible aspect of that world. Currently deployed examples include devices that can capture water/air samples, and devices that capture individual insects or fish. Such devices create an interesting twist on the stream sampling problem, because in most cases, the decision to take a physical sample is irrevocable. In this work we show how to generalize diversification sampling strategies to the irrevocable-choice setting, demonstrating our ideas on several real world domains.     

Managing variants of a personalized product

A product variant table is a table that lists legal combinations of product features. Variant tables can be used to constrain the variability offered for a personalized product. The concept of such a table is easy to understand. Hence, variant tables are natural to use when ensuring the completeness and correctness of a quote/order for a customizable product. They are also used to filter out inadmissible choices for features in an interactive specification (configuration) process. Variant tables can be maintained as relational (database) tables, using spreadsheets, or in proprietary ways offered by the product modeling environment. Variant tables can become quite large. A way of compressing them is then sought that supports a space-efficient representation and a time-efficient evaluation. The motivation of this work is to develop a simple approach to compress/compile a variant table into an easy to read, but possibly hard to write form that can be deployed in a business setting at acceptable cost and risk in a similar manner as a database. The main result is a simple compression and evaluation scheme for an individual variant table called a Variant Decomposition Diagram (VDD). A VDD supports efficient consistency checks, the filtering of inadmissible features, and iteration over the table. A simple static heuristic for decomposition order is proposed that suggests itself from a “column oriented viewpoint”. This heuristic is not always optimal, but it has the advantage of allowing fast compilation of a variant table into a VDD. Compression results for a publicly available model of a Renault Megane are given. With the proposed heuristic the VDD is a specialization of a Zero-suppressed (binary) Decision Diagram (ZDD) (Knuth 2011) and also maps to a Multi-valued Decision Diagram (MDD) (Andersen et al. 2007; Berndt et al. 2012).     

Linear Parameter-varying Approach for Modeling and Control of Rapid Thermal Processes

In the present paper, a new approach is presented to model and control single wafer rapid thermal processing (RTP) systems. In the past decade, RTP has achieved acceptance as the mainstream technology for semiconductor manufacturing. Thermal processing is one of the most efficient ways to control the phase-structure properties. Moreover, the time duration of RTP systems reduces the so-called thermal budget significantly compared to the traditional methods. RTP implementation is based on the use of light from heating lamps to provide a heat flux. This process is highly nonlinear due to the radiative heat transfer and material properties. By invoking the first principles-based models, we develop in this paper a linear parameter-varying (LPV) model to directly account for the nonlinearities within the system. The model is then discretized into a high-order LPV model; thereafter, principal component analysis (PCA) method is utilized to reduce the number of LPV model’s scheduling variables, followed by the use of proper orthogonal decomposition (POD) for model order reduction. Using the reduced order model, we then design a gain-scheduled controller to satisfy an induced L₂ gain performance for tracking of a temperature profile and show improvement over other controller design methods suggested in the literature.     

An orthogonal analysis method for decoupling the nozzle geometrical parameters of microthrusters

This paper proposes an orthogonal analysis method for decoupling the multiple nozzle geometrical parameters of microthrusters, thus an reconfigured design can be implemented to generate a proper thrust. In this method, the effects of various nozzle geometrical parameters, including throat width W _t , half convergence angle θ _in , half divergence angle θ _out , exit-to-throat section ratio W _e /W _t and throat radius of the curvature R _t /W _t , on the performance of microthrusters are sorted by range analysis. Analysis results show that throat width seriously affects thrust because range value of 67.53 mN is extremely larger than the range value of other geometry parameters. For average specific impulse (ASI), the range value of exit-to-throat section ratio W _e /W _t and half divergence angle θ _out are 4.82 s and 3.72 s, respectively. Half convergence angle with the range value of 0.39 s and throat radius with 0.32 s have less influence on ASI compared with exit-to-throat section ratio and half divergence angle. When increasing the half convergence angle from 10° to 40° and throat radius of the curvature from 3 to 9, average specific impulse initially decreases and then increases. A MEMS solid propellant thruster (MSPT) with the reconfigured geometrical parameters of nozzle is fabricated to verify the feasibility of the proposed method. The thrust of the microthruster can reach 25 mN. Power is estimated to be 0.84 W. This work provides design guideline to reasonably configure geometry parameters of microthruster.     

ReFlO: an interactive tool for pipe-and-filter domain specification and program generation

ReFlO is a framework and interactive tool to record and systematize domain knowledge used by experts to derive complex pipe-and-filter (PnF) applications. Domain knowledge is encoded as transformations that alter PnF graphs by refinement (adding more details), flattening (removing modular boundaries), and optimization (substituting inefficient PnF graphs with more efficient ones). All three kinds of transformations arise in reverse-engineering legacy PnF applications. We present the conceptual foundation and tool capabilities of ReFlO, illustrate how parallel PnF applications are designed and generated, and how domain-specific libraries of transformations are developed.     

On the Advice Complexity of the k-server Problem Under Sparse Metrics

We consider the k-Server problem under the advice model of computation when the underlying metric space is sparse. On one side, we introduce Θ(1)-competitive algorithms for a wide range of sparse graphs. These algorithms require advice of (almost) linear size. We show that for graphs of size N and treewidth α, there is an online algorithm that receives O (n(log α + log log N))^* bits of advice and optimally serves any sequence of length n. We also prove that if a graph admits a system of μ collective tree (q, r)-spanners, then there is a (q + r)-competitive algorithm which requires O (n(log μ + log log N)) bits of advice. Among other results, this gives a 3-competitive algorithm for planar graphs, when provided with O (n log log N) bits of advice. On the other side, we prove that advice of size Ω(n) is required to obtain a 1-competitive algorithm for sequences of length n even for the 2-server problem on a path metric of size N ≥ 3. Through another lower bound argument, we show that at least \(\frac {n}{2}(\log \alpha - 1.22)\) bits of advice is required to obtain an optimal solution for metric spaces of treewidth α, where 4 ≤ α < 2k.     

Property-Preserving Data Reconstruction

We initiate a new line of investigation into online property-preserving data reconstruction. Consider a dataset which is assumed to satisfy various (known) structural properties; e.g., it may consist of sorted numbers, or points on a manifold, or vectors in a polyhedral cone, or codewords from an error-correcting code. Because of noise and errors, however, an (unknown) fraction of the data is deemed unsound, i.e., in violation with the expected structural properties. Can one still query into the dataset in an online fashion and be provided data that is always sound? In other words, can one design a filter which, when given a query to any item I in the dataset, returns a sound item J that, although not necessarily in the dataset, differs from I as infrequently as possible. No preprocessing should be allowed and queries should be answered online.We consider the case of a monotone function. Specifically, the dataset encodes a function f:{1,…,n}?? R that is at (unknown) distance ε from monotone, meaning that f can—and must—be modified at ε n places to become monotone.Our main result is a randomized filter that can answer any query in O(log?² nlog? log?n) time while modifying the function f at only O(ε n) places. The amortized time over n function evaluations is O(log?n). The filter works as stated with probability arbitrarily close to 1. We provide an alternative filter with O(log?n) worst case query time and O(ε nlog?n) function modifications. For reconstructing d-dimensional monotone functions of the form f:{1,…,n} ^d ? ? R, we present a filter that takes (2 ^O(d)(log?n)^4d?2log?log?n) time per query and modifies at most O(ε n ^d ) function values (for constant d).     

Remark on balanced incomplete block designs,near-resolvable block designs,and <Emphasis Type="Italic">q</Emphasis>-ary constant-weight codes

We prove that any balanced incomplete block design B(v, k, 1) generates a nearresolvable balanced incomplete block design NRB(v, k ? 1, k ? 2). We establish a one-to-one correspondence between near-resolvable block designs NRB(v, k ?1, k ?2) and the subclass of nonbinary (optimal, equidistant) constant-weight codes meeting the generalized Johnson bound.     

Shadow Prices in Territory Division

We consider a geographic optimization problem in which we are given a region R, a probability density function f(?) defined on R, and a collection of n utility density functions u _i (?) defined on R. Our objective is to divide R into n sub-regions R _i so as to “balance” the overall utilities on the regions, which are given by the integrals \(\iint _{R_{i}}f(x)u_{i}(x)\, dA\). Using a simple complementary slackness argument, we show that (depending on what we mean precisely by “balancing” the utility functions) the boundary curves between optimal sub-regions are level curves of either the difference function u _i (x) ? u _j (x) or the ratio u _i (x)/u _j (x). This allows us to solve the problem of optimally partitioning the region efficiently by reducing it to a low-dimensional convex optimization problem. This result generalizes, and gives very short and constructive proofs of, several existing results in the literature on equitable partitioning for particular forms of f(?) and u _i (?). We next give two economic applications of our results in which we show how to compute a market-clearing price vector in an aggregate demand system or a variation of the classical Fisher exchange market. Finally, we consider a dynamic problem in which the density function f(?) varies over time (simulating population migration or transport of a resource, for example) and derive a set of partial differential equations that describe the evolution of the optimal sub-regions over time. Numerical simulations for both static and dynamic problems confirm that such partitioning problems become tractable when using our methods.     

Reducing the Range of Perception in Multi-agent Patrolling Strategies

Multi-Agent Patrolling Problems consist in moving agents throughout a graph in order to optimize a collective performance metric. Some strategies from the literature tackle this problem by dispatching decentralized autonomous agents that coordinate themselves merely by sensing and writing information in the nodes. In this work, they are called k-range local strategies, were k indicates the range, in number of edges, of the agents’ sensing capabilities. The 1-range strategies (where agents can sense up to its neighbor nodes) are certainly the most common case in the literature. And only few 0-range strategies (where agents can only sense its current node) were found, although this type of strategy has the advantage of requiring simpler hardware, when applied in the design of real robots. In this work, we propose two higher-level procedures to reduce the perception range of 1-range strategies to 0: the Zr Method and the EZr Method. Applying both methods in 1-range strategies found in the literature, we created twenty new 0-range strategies, which were evaluated in a simulation experiment described and analyzed here. We also developed a prototype of a low-cost patrolling robot that is able to run the 0-range strategies proposed in this work.