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University of Twente Publications (47,896 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

Type = Article

Mostrando recursos 1 - 20 de 21,840

1. Focal salvage iodine-125 brachytherapy for prostate cancer recurrences after primary radiotherapy: a retrospective study regarding toxicity, biochemical outcome and quality of life - Peters, Max; Maenhout, Metha; Voort van Zyp, Jochem R.N. van der; Moerland, Marinus A.; Moman, Maaike R.; Steuten, Lotte M.G.; Deursen, Marijke J.H. van; Vulpen, Marco van
Purpose Whole-gland salvage for recurrent prostate cancer (PCa) shows high failure and toxicity rates. Early and adequate localization of recurrences enables focal salvage, thereby potentially improving functional outcomes, while maintaining cancer control. Materials and methods Retrospective analysis yielded 20 focal salvage I125 brachytherapy patients for locally recurrent PCa after primary radiotherapy. Tumor was defined by multiparametric MRI and correspondence with transrectal biopsies. Dose data were obtained intra-operatively. The tumor was prescribed ⩾144 Gy. Toxicity was scored by the Common Terminology Criteria for Adverse Events version 4 (CTCAE-4). Biochemical failure (BF) was defined using the Phoenix criteria (PSA-nadir + 2.0 ng/ml). Quality of life...

2. Cores of games with restricted cooperation - Faigle, U.
Games with restricted cooperation are cooperativeN-person games with sidepayments, where the collection of feasible coalitions need not comprise all subsets of players and thus is restricted. We study balanced and completely balanced games in this context and derive the corresponding core theorems from a sandwich theorem for set functions within the setting of linear programming. In particular, we discuss general convex games, which Edmonds and Giles (1977) have shown to be of particular importance also in combinatorial optimization.

3. Queueing systems on a circle - Kroese, Dirk P.; Schmidt, Volker
Consider a ring on which customers arrive according to a Poisson process. Arriving customers drop somewhere on the circle and wait there for a server who travels on the ring. Whenever this server encounters a customer, he stops and serves the customer according to an arbitrary service time distribution. After the service is completed, the server removes the client from the circle and resumes his journey. We are interested in the number and the locations of customers that are waiting for service. These locations are modeled as random counting measures on the circle. Two different types of servers are considered: The...

4. The irreducible Core of a minimum cost spanning tree game - Aarts, Harry; Driessen, Theo
It is a known result that for a minimum cost spanning tree (mcst) game a Core allocation can be deduced directly from a mcst in the underlying network. To determine this Core allocation one only needs to determine a mcst in the network and it is not necessary to calculate the coalition values of the corresponding mcst game. In this paper we will deduce other Core allocations directly from the network, without determining the corresponding mcst game itself: we use an idea of Bird (cf. [4]) to present two procedures that determine a part of the Core (called the Irreducible...

5. A cooperative game of information trading: The core, the nucleolus and the kernel - Driessen, T.; Muto, S.; Nakayama, M.
A certain trade of the information about a technological innovation between the initial owner of the information andn identical producers is studied by means of a cooperative game theoretic approach. The information trading situation is modelled as a cooperative (n+1)-person game with side payments. The symmetrical strong ɛ-cores (including the core), the nucleolus and the kernel of the cooperative game model are determined. Interpretations of these game theoretic solutions and their implications for the information trading problem are given.

6. Optimization and optimality test for the Max-Cut Problem - Hohmann, Chr.; Kern, W.
We show that the following two problems are polynomially equivalent: 1. Given a (weighted) graphG, and a cutC ofG, decide whetherC is maximal or not. 2. Given a (weighted) graphG, and a cutC ofG, decide whetherC is maximal or not, and in case it is not, find a better solutionC′. As a consequence, an optimality testing oracle may be used to design a polynomial time algorithm for approximately solving the (weighted) Max-Cut Problem. This in turn implies that recognizing optimal cuts in an unweighted graph is NP-hard.

7. On linear consistency of anonymous values for TU-games - Yanovskaya, Elena; Driessen, Theo
In the framework of values for TU-games, it is shown that a particular type of consistency, called linear consistency, together with some kind of standardness for two-person games, imply efficiency, anonymity, linearity, as well as uniqueness of the value. Among others, this uniform treatment generalizes Sobolev's axiomatization of the Shapley value.

8. Using shaped beam patterns for tracking - Bruintjes, T.M.; Kokkeler, A.B.J.; Karagiannis, G.; Smit, G.J.M.
This communication presents a new direction-of-arrival based tracking method, using shaped beam patterns. The advantage of this method is that the direction of a signal can be estimated based on a single output (analog) beamformer, without having to scan over multiple angles. Simulations indicate that, although arrays consisting of 8 to 16 antennas are preferable, the minimum array size is 4. A single array can cover a scan angle of roughly 120° and the direction of arrival can be estimated with an RMS error of 2°.

9. Clustering clinical departments for wards to achieve a prespecified blocking probability - Essen, J. Theresia van; Houdenhoven, Mark van; Hurink, Johann L.
When the number of available beds in a hospital is limited, it can be beneficial to cluster several clinical departments such that the probability of not being able to admit a patient is acceptably small. However, not all clinical departments can be clustered for cross-infection reasons. In addition, patients from one clinical department should not be spread out over the entire hospital as this complicates the process of doing rounds and may result in alternate level of care. In this paper, we consider a situation where wards with a fixed number of beds are given. The question is how to...

10. A bankruptcy problem and an information trading problem: applications to k-convex games - Driessen, Theo
The paper is devoted to two real problems that generate a cooperative game model with a so-calledk-convex characteristic function when certain conditions are fulfilled. Both a bankruptcy problem and an information trading problem are modelled as a cooperative game by constructing the corresponding bankruptcy game as well as the information market game. Firstly, it is established that the bankruptcy game is ak-convexn-person game where 1 ≤k ≤n − 2 if and only if the estate is sufficient to meet the claims of creditors in any (n − k)-person coalition. Secondly, it is shown that thek-convexity property for the information market...

11. Internal and external spatial attention examined with lateralized EEG power spectra - Lubbe, Rob H.J. van der; Bundt, Carsten; Abrahamse, Elger L.
Several authors argued that retrieval of an item from visual short term memory (internal spatial attention) and focusing attention on an externally presented item (external spatial attention) are similar. Part of the neuroimaging support for this view may be due to the employed experimental procedures. Furthermore, as internal spatial attention may have a more induced than evoked nature some effects may not have been visible in event related analyses of the electroencephalogram (EEG), which limits the possibility to demonstrate differences. In the current study, a colored frame cued which stimulus, one out of four presented in separate quadrants, required a...

12. A randomized controlled trial of an Internet-based cognitive–behavioural intervention for non-specific chronic pain: An effectiveness and cost-effectiveness study - Boer, M.J. de; Versteegen, G.J.; Vermeulen, K.M.; Sanderman, R.; Struys, M.M.R.F.
Background Cognitive–behavioural treatment can nowadays be delivered through the Internet. This form of treatment can have various advantages with regard to availability and accessibility. Previous studies showed that Internet-based treatment for chronic pain is effective compared to waiting-list control groups. Methods We conducted a randomized controlled trial comparing an Internet-based cognitive–behavioural intervention with e-mail therapist contact to a face-to-face cognitive–behavioural group intervention. Of the 72 participants who were randomly assigned to an Internet or a group course, 50 participants completed the intervention. Participants were assessed at baseline (T0), immediately after the 7-week course (T1) and at the booster session 2 months later (T2)....

13. Quality assurance in the European policy arena - Enders, Jürgen; Westerheijden, Don F.
Our paper investigates the emergence, development and contested nature of quality assurance (QA) in the European policy arena as part and parcel of the Bologna Process. We conceptualise our paper on the background of the study of multi-level and multi-actor dynamics between national, inter-governmental and supranational policies; we discuss the changing ideational framing of QA in the European policy arena, and attempts at European norm-setting and standardisation. QA in the Bologna Process moved from a non-binding inter-governmental agreement towards monitored coordination and became embedded in the competitive turn in European higher education policy stressing an instrumental view of the university....

14. What's Holding Back Social Entrepreneurship? Removing the Impediments to Theoretical Advancement - Mueller, Susan; D'Intino, Robert S.; Walske, Jennifer; Ehrenhard, Michel L.; Newbert, Scott L.; Robinson, Jeffrey A.; Senjem, Jason C.
This article summarizes four contributions that were presented in a professional development workshop at the 2013 Academy of Management conference. The goal of the workshop was to discuss impediments to the theoretical advancement of social entrepreneurship. This paper's first two contributors discuss assumptions and boundaries of social entrepreneurship, exhibiting contrasting views of whether theory should be aggregated or disaggregated. The other two scholars focus on specific topics that advance social entrepreneurship research, specifically, studying the implicit normative underpinning of social entrepreneurship and social innovation processes. This is part three of a three-part series dealing with the future of social entrepreneurship...

15. Using prior risk-related knowledge to support risk management decisions: lessons learnt from a tunneling project - Chivatá Cárdenas, I.C.; Al-Jibouri, Saad S.H.; Halman, J.I.M.; Linde, W. van de; Kaalberg, F.
The authors of this article have developed six probabilistic causal models for critical risks in tunnel works. The details of the models' development and evaluation were reported in two earlier publications of this journal. Accordingly, as a remaining step, this article is focused on the investigation into the use of these models in a real case study project. The use of the models is challenging given the need to provide information on risks that usually are both project and context dependent. The latter is of particular concern in underground construction projects. Tunnel risks are the consequences of interactions between site-...

16. Satellites & sensors - Bakker, Wim

17. 3-D desktop mapping and volume change estimation of the Northern Ameland Coast, the Netherlands - Bakx, J.P.G.; Zuidam, R.A. van; Mulder, N.J.

18. 3-channel double relaxation oscillation SQUID magnetometer system with simple readout electronics - Lee, Y.H.; Kim, J.M.; Kwon, H.C.; Park, Y.K.; Park, J.C.; Duuren, M.J. van; Adelerhof, D.J.; Flokstra, J.; Rogalla, H.
Recently several approaches have been made to simplify the readout scheme of the standard dc SQUID. A double relaxation oscillation SQUID(DROS) consisting of a hysteretic dc SQUID and a reference junction in series shunted by an inductor and a resistor can provide a very large flux-to-voltage transfer coefficient. Thus, a DROS with direct readout with room temperature dc amplifier can be a good candidate for the next-generation SQUID magnetometer. We report on the development of a 3-channel magnetometer system based on DROS. The DROS is based on Nb/AlO/sub X//Nb Josephson junctions and the main feature of the system is its...

19. Hierarchical Bayesian modeling of the space-time diffusion patterns of cholera epidemic in Kumasi, Ghana - Osei, Frank B.; Duker, Alfred A.; Stein, Alfred
This study analyses the joint effects of the two transmission routes of cholera on the space-time diffusion dynamics. Statistical models are developed and presented to investigate the transmission network routes of cholera diffusion. A hierarchical Bayesian modelling approach is employed for a joint analysis of nonlinear effects of continuous covariates, spatially structured variation, and unstructured heterogeneity. Proximity to primary case locations and population density serve as continuous covariates. Reference to communities is modelled as a spatial effect. The study applied to the Kumasi area in Ghana shows that communities proximal to primary case locations are infected relatively early during the...

20. Towards intelligent manufacturing planning and control systems - Zijm, W.H.M.
In this paper, we review some well-known manufacturing planning and control (MPC) systems and models, and highlight both their advantages and major drawbacks. The analysis indicates that various important planning and control problems, as they arise in industry, are not properly addressed by current MPC systems. A well-known production system typology, illustrated by industrial examples, is briefly discussed to further highlight these planning and control problems. Next, we define a basic framework architecture for planning and control in both make-to-stock and make-to-order systems. The emphasis in this framework is on an integration of technological and logistics planning, and on an...

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