2,185 research outputs found
On the Complexity of an Unregulated Traffic Crossing
The steady development of motor vehicle technology will enable cars of the
near future to assume an ever increasing role in the decision making and
control of the vehicle itself. In the foreseeable future, cars will have the
ability to communicate with one another in order to better coordinate their
motion. This motivates a number of interesting algorithmic problems. One of the
most challenging aspects of traffic coordination involves traffic
intersections. In this paper we consider two formulations of a simple and
fundamental geometric optimization problem involving coordinating the motion of
vehicles through an intersection.
We are given a set of vehicles in the plane, each modeled as a unit
length line segment that moves monotonically, either horizontally or
vertically, subject to a maximum speed limit. Each vehicle is described by a
start and goal position and a start time and deadline. The question is whether,
subject to the speed limit, there exists a collision-free motion plan so that
each vehicle travels from its start position to its goal position prior to its
deadline.
We present three results. We begin by showing that this problem is
NP-complete with a reduction from 3-SAT. Second, we consider a constrained
version in which cars traveling horizontally can alter their speeds while cars
traveling vertically cannot. We present a simple algorithm that solves this
problem in time. Finally, we provide a solution to the discrete
version of the problem and prove its asymptotic optimality in terms of the
maximum delay of a vehicle
Morbidity And Quality Of Life Among Head And Neck Cancer Patients Treated With Radical Radiotherapy
Objectives: To determine the relative frequency of acute radiation morbidity and their perceived effect on quality of life among head and neck cancer patients treated with radical radiotherapy.Design: A cross-sectional study.Setting: Kenyatta National Hospital, Nairobi.Subjects: Thirty eight patients comprising 28 males and 10 females with ages ranging between 21 and 69 years were evaluated.Results: Most of the tumours occurred in the nasopharynx (38.6%). The rest of the tumours were equally divided between the oral cavity and larynx (31.6%). All tumours except two were carcinomas. The two exceptions were a glomus tumour and a malignant melanoma. The patients had received doses of radiotherapy ranging between 58.5 Grey and 75.5 Grey. Of the 38 patients, 22 (53%) completed their treatment in the prescribedtime while 16 (47%) had treatment interruption on account of radiation morbidity. The cumulative radiation done at the time of interruption ranged between 20 and 46 Grey. The most frequent symptom was dryness of the mouth while the most troublesome symptom was difficulty in tasting foods. The quality of life (QOL) did not vary by age, gender or tumour site. Patients who had treatment interruption had a better QOLthan those who did not.Conclusion: This study provides information that should aid in communicating with the head and neck cancer patients scheduled for radiotherapy and in the design of preventive and interventional strategies aimed at enhancing patient support and rehabilitation
Engineering Cu2O Nanowire Surfaces for Photoelectrochemical Hydrogen Evolution Reaction
Cu2O is a narrow band gap material serving as an important candidate for photoelectrochemical hydrogen evolution reaction. However, the main challenge that hinders its practical exploitation is its poor photostability, due to its oxidation into CuO by photoexcited holes. Here, we thoroughly minimize the photo-oxidation of Cu2O nanowires by growing a thin layer of the TiO2 protective layer and an amorphous layer of the VOx cocatalyst using magnetron sputtering and atomic layer deposition, respectively. After optimization of the protective and the cocatalyst layers, the photoelectrode exhibits a current density of -2.46 mA/cm2 under simulated sunlight (100 mW/cm2) at 0.3 V versus reversible hydrogen electrode, and its performance is stable for an extended illumination time. The chemical stability and the good performance of the engineered photoelectrode demonstrate the potential of using earth-abundant materials as a light-harvesting device for solar hydrogen production
Creating and controlling visual environments using BonVision.
Real-time rendering of closed-loop visual environments is important for next-generation understanding of brain function and behaviour, but is often prohibitively difficult for non-experts to implement and is limited to few laboratories worldwide. We developed BonVision as an easy-to-use open-source software for the display of virtual or augmented reality, as well as standard visual stimuli. BonVision has been tested on humans and mice, and is capable of supporting new experimental designs in other animal models of vision. As the architecture is based on the open-source Bonsai graphical programming language, BonVision benefits from native integration with experimental hardware. BonVision therefore enables easy implementation of closed-loop experiments, including real-time interaction with deep neural networks, and communication with behavioural and physiological measurement and manipulation devices
A randomized trial comparing digital and live lecture formats [ISRCTN40455708
BACKGROUND: Medical education is increasingly being conducted in community-based teaching sites at diverse locations, making it difficult to provide a consistent curriculum. We conducted a randomized trial to assess whether students who viewed digital lectures would perform as well on a measure of cognitive knowledge as students who viewed live lectures. Students' perceptions of the digital lecture format and their opinion as whether a digital lecture format could serve as an adequate replacement for live lectures was also assessed. METHODS: Students were randomized to either attend a lecture series at our main campus or view digital versions of the same lectures at community-based teaching sites. Both groups completed the same examination based on the lectures, and the group viewing the digital lectures completed a feedback form on the digital format. RESULTS: There were no differences in performance as measured by means or average rank. Despite technical problems, the students who viewed the digital lectures overwhelmingly felt the digital lectures could replace live lectures. CONCLUSIONS: This study provides preliminary evidence digital lectures can be a viable alternative to live lectures as a means of delivering didactic presentations in a community-based setting
An Optimization Approach to the Ordering Phase of an Attended Home Delivery Service
Attended Home Delivery (AHD) systems are used whenever a supplying company
offers online shopping services that require that customers must be present
when their deliveries arrive. Therefore, the supplying company and the customer
must both agree on a time window, which ideally is rather short, during which
delivery is guaranteed. Typically, a capacitated Vehicle Routing Problem with
Time Windows forms the underlying optimization problem of the AHD system. In
this work, we consider an AHD system that runs the online grocery shopping
service of an international grocery retailer. The ordering phase, during which
customers place their orders through the web service, is the computationally
most challenging part of the AHD system. The delivery schedule must be built
dynamically as new orders are placed. We propose a solution approach that
allows to (non-stochastically) determine which delivery time windows can be
offered to potential customers. We split the computations of the ordering phase
into four key steps. For performing these basic steps we suggest both a
heuristic approach and a hybrid approach employing mixed-integer linear
programs. In an experimental evaluation we demonstrate the efficiency of our
approaches
Finding a voice? Narrating the female self in mathematics
If mathematics is a male domain, where does this leave women who do mathematics? In a world where there is little or no discursive space in which to be female, women who enter in must do identity work in order to achieve what is often an uneasy presence. This paper builds on recent research which suggests that some undergraduate women are however finding new spaces for belonging in the world of mathematics through critical reflection and collective challenge to dominant discourses. Focussing on an analysis of two womenâs narratives of their success in mathematics, it explores their multi-voiced accounts of self through the lens of Bakhtinâs dialogism. It discusses the scope of reflexivity in creating new identity spaces in refigured worlds
Freight distribution performance indicators for service quality planning in large transportation networks
This paper studies the use of performance indicators in routing problems to estimate how transportation cost is affected by the quality of service offered. The quality of service is assumed to be directly dependent on the size of the time windows. Smaller time windows mean better service. Three performance indicators are introduced. These indicators are calculated directly from the data without the need of a solution method. The introduced indicators are based mainly on a "request compatibility", which describes whether two visits can be scheduled consecutively in a route. Other two indicators are introduced, which get their values from a greedy constructive heuristic. After introducing the indicators, the correlation between indicators and transportation cost is examined. It is concluded that the indicators give a good first estimation on the transportation cost incurred when providing a certain quality of service. These indicators can be calculated easily in one of the first planning steps without the need of a sophisticated solution tool. The contribution of the paper is the introduction of a simple set of performance indicators that can be used to estimate the transportation cost of a routing problem with time window
Distance Approximation for Dynamic Waste Collection Planning
Approximating the solution value of transportation problems has become more relevant in recent years, as these approximations can help to decrease the computational eort required for solving those routing problems. In this paper, we apply several regression methods to predict the total distance of the traveling salesman problem (TSP) and vehicle routing problem (VRP). We show that distance can be estimated fairly accurately using simple regression models and only a limited number of features. We use features found in scientific literature and introduce a new class of geographical features. The model is validated on a dynamic waste collection case in the city of Amsterdam, The Netherlands. We introduce a cost function that combines the travel distance and service level, and show that our model can reduce distances up to 17%, while maintaining the same service level, compared to a well-known heuristic approximation. Furthermore, we show the benefits of using approximations for combining oine learning with online or frequent optimization
A preliminary randomized double blind placebo-controlled trial of intravenous immunoglobulin for Japanese encephalitis in Nepal
BACKGROUND: Japanese encephalitis (JE) virus (JEV) is a mosquito-borne flavivirus found across Asia that is closely related to West Nile virus. There is no known antiviral treatment for any flavivirus. Results from in vitro studies and animal models suggest intravenous immunoglobulin (IVIG) containing virus-specific neutralizing antibody may be effective in improving outcome in viral encephalitis. IVIG's anti-inflammatory properties may also be beneficial. METHODOLOGY/PRINCIPAL FINDINGS: We performed a pilot feasibility randomized double-blind placebo-controlled trial of IVIG containing anti-JEV neutralizing antibody (ImmunoRel, 400mg/kg/day for 5 days) in children with suspected JE at two sites in Nepal; we also examined the effect on serum neutralizing antibody titre and cytokine profiles. 22 children were recruited, 13 of whom had confirmed JE; 11 received IVIG and 11 placebo, with no protocol violations. One child (IVIG group) died during treatment and two (placebo) subsequently following hospital discharge. Overall, there was no difference in outcome between treatment groups at discharge or follow up. Passive transfer of anti-JEV antibody was seen in JEV negative children. JEV positive children treated with IVIG had JEV-specific neutralizing antibody titres approximately 16 times higher than those treated with placebo (p=0.2), which was more than could be explained by passive transfer alone. IL-4 and IL-6 were higher in the IVIG group. CONCLUSIONS/SIGNIFICANCE: A trial of IVIG for JE in Nepal is feasible. IVIG may augment the development of neutralizing antibodies in JEV positive patients. IVIG appears an appealing option for JE treatment that warrants further study. TRIAL REGISTRATION: ClinicalTrials.gov NCT01856205
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