2,443 research outputs found
Coagulation systems of invertebrates and vertebrates and their roles in innate immunity: The same side of two coins?
No full textTorsten G. Loof, Otto Schmidt, Heiko Herwald, Ulrich Theopol
Modelling Interregional Trade of Energy Crops in Eastern Germany
No full textRenewable resources gain in importance in our modern society. The line of reasoning is based on their positive effects on agriculture, the environment and the economy. To support renewable energy from biomass the EU promotes the cultivation of energy crops. A spatial equilibrium model is applied based on the concept of maximizing net welfare, to provide information whether energy crop production competes with food production for land area. The Model of Interregional Trade of Energy Crops (ITEC) refers to Eastern Germany and adjacent areas of Poland. First results show that the regions have enough feedstocks to meet the required demand for food and biofuel production. In many cases both food crops and biofuels are either traded on interregional basis or exported to "Rest of Europe" indicating that there is no competition between food and energy crops. Only green maize for biogas production strongly competes in areas where the crop is required as feed for cattle.Energy crops, spatial equilibrium analysis, interregional trade, International Relations/Trade,
In-situ study of emerging metallicity and memory effect on ion-beam bombarded strontium titanate surface:
No full textIn this work we present an investigation of the occurrence of conductivity on the surface of SrTiO3 due to argon ion bombardment. We created a model to describe this process and found that the temperature during the ion milling is a crucial factor for the conductivity. Depending on the temperatures we found surface carrier densities ranging from 1.5*10^18 to 2.6*10^20cm^-3 by just analyzing the conductivity behavior.
Clustering of vacancies goes along with temperature and affects the conductivity significantly. Furthermore we found that ion milling is a gentle way create vacancies because the clustering rate is small compared to annealing samples in high vacuum. The amount of clusters at room temperature was measured to be around 3-4 times higher than at -140C.
We found that samples with a conducting surface change their resistance over time at room temperature due to the ongoing process of oxygen vacancy clustering. This effect may be suppressed by decreasing the temperature.
The bistable switching behavior in oxygen deficient SrTiO3 is shown without any additional doping. The vacancy migration is the major mechanism behind this memory effect. Comparing this behavior with annealed samples in high vacuum shows that the therein present amount of vacancy clusters must be much larger and has a negative effect on the bistable switching behavior.M.S.Includes bibliographical references (p. 83-87)by Heiko Gros
Handle with Care : Implementation of the List Experiment and Crosswise Model in a Large-Scale Survey on Academic Misconduct
No full textAcknowledgments We thank the anonymous reviewers as well as Alexander Ehlert, Isabel Raabe, and Justus Rathmann for their concise comments and constructive feedback on our work. Co-authors in alphabetical order. Study Design: Julia Jerke, David Johann, Heiko Rauhut, Kathrin Thomas, Antonia Velicu. Coding and Analysis: Julia Jerke, David Johann, Kathrin Thomas, Antonia Velicu. First draft: Julia Jerke, Heiko Rauhut, Kathrin Thomas, Antonia Velicu. Revisions: David Johann, Kathrin Thomas, Antonia Velicu. Final approval of the paper: Julia Jerke, David Johann, Heiko Rauhut, Kathrin Thomas, Antonia Velicu. Funding Information: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research is supported by the Swiss National Science Foundation (SNSF), Starting Grant “CONCISE” BSSGIO 155981 of Heiko Rauhut.Peer reviewe
Map-based stochastic simulation data of a transient Ekman boundary layer
No full textOverview
A journal paper in Advances in Science and Research [1] details the numerical modeling approach used to create the data. Here, the model input files, the raw data, processed data, and plot scripts are provided that support the research.
The code used here [2,3] is an extended version of the one-dimensional turbulence (ODT) model [4,5]. The current model implementation utilizes an adaptive grid that further increases numerical efficiency [6.7]. A truncated version of the adaptive ODT code of this work is described in [8] and publicly available free of charge in [9].
The theoretical foundation and numerical as well as experimental evidence for this work is given in [10,11,12,13], and the main motivation in [14].
The bash script makePlot.sh is the top-level driver and contains all additional information about the cases. Some other Details are provided by low-level README files. Python-3.8 is required to run the scripts.
References
[1] M. Klein, and H. Schmidt. Capturing features of turbulent Ekman–Stokes boundary layers
with a stochastic modeling approach. Adv. Sci. Res, 20, 55–64, https://doi.org/10.5194/asr-20-55-2023, 2023.
[2] M. Klein, and H. Schmidt. Exploring stratification effects in stable Ekman boundary layers using a stochastic one-dimensional turbulence model, Adv. Sci. Res., 19, 117–136, https://doi.org/10.5194/asr-19-117-2022, 2022.
[3] M. Klein, and H. Schmidt. A stochastic modeling strategy for intermittently unstable Ekman—Stokes boundary layers, Proc. Appl. Math. Mech., 20, e202000127, https://doi.org/10.1002/pamm.202000127, 2020.
[4] A. R. Kerstein. One-dimensional turbulence: Model formulation and application to homogeneous turbulence, shear flows, and buoyant stratified flows, J. Fluid Mech., 392, 277–334, https://doi.org/10.1017/S0022112099005376, 1999.
[5] A. R. Kerstein, and S. Wunsch. _Simulation of a stably stratified atmospheric boundary layer using one-dimensional turbulence, Boundary-Layer Meteorol., 118, 325–356, https://doi.org/10.1007/s10546-005-9004-x, 2006.
[6] D. O. Lignell, A. R. Kerstein, G. Sun, and E. T. Monson. Mesh adaption for efficient multiscale implementation of one-dimensional turbulence, Theor. Comput. Fluid Dyn., 27, 273–295, https://doi.org/10.1007/s00162-012-0267-9, 2013.
[7] D. O. Lignell V. B. Lansinger, J. Medina, M. Klein A. R. Kerstein, H. Schmmidt, M. Fistler, and M. Oevermann. One-dimensional turbulence modeling for cylindrical and spherical flows: model formulation and application, Theor. Comput. Fluid Dyn., 32, 495–520, https://doi.org/10.1007/s00162-018-0465-1, 2018.
[8] V. B. Stephens, and D. O. Lignell. One-dimensional turbulence (ODT): Computationally efficient modeling and simulation of turbulent flows, Software X, 13, 100641, https://doi.org/10.1016/j.softx.2020.100641, 2021.
[9] BYU Ignite. Adaptive ODT source code, https://github.com/BYUignite/ODT.
[10] S. Salon, and V. Armenio. A numerical investigation of the turbulent Stokes–Ekman bottom boundary layer, J. Fluid Mech., 684, 316–352, https://doi.org/10.1017/jfm.2011.303, 2011.
[11] M. Klein, T. Seelig, M. V. Kurgansky, A. Ghasemi V., I. D. Borcia, A. Will, E. Schaller, C. Egbers, and U. Harlander. Inertial wave excitation and focusing in a liquid bounded by a frustum and a cylinder, J. Fluid Mech., 751, 255–297, https://doi.org/10.1017/jfm.2014.304, 2014.
[12] A. Ghasemi, M. Klein, A. Will, and U. Harlander. Mean flow generation by an intermittently unstable boundary layer over a sloping wall, J. Fluid Mech., 853, 111–149, https://doi.org/10.1017/jfm.2018.552, 2018.
[13] M. Vincze, N. Fenyvesi, M. Klein, J. Sommeria, S. Viboud, and Y. Ashkenazy. Evidence for wind-induced Ekman layer resonance based on rotating tank experiments, EPL, 125, 44001, https://doi.org/10.1209/0295-5075/125/44001, 2019.
[14] L. S. Freire. Large-eddy simulation of the atmospheric boundary layer with near-wall resolved turbulence, Boundary-Layer Meteorol., 184, 25–43, https://doi.org/https://doi.org/10.1007/s10546-022-00702-z, 2022
Upper and Lower Bounds for Complete Linkage in General Metric Spaces
No full textIn a hierarchical clustering problem the task is to compute a series of mutually compatible clusterings of a finite metric space (P,dist). Starting with the clustering where every point forms its own cluster, one iteratively merges two clusters until only one cluster remains. Complete linkage is a well-known and popular algorithm to compute such clusterings: in every step it merges the two clusters whose union has the smallest radius (or diameter) among all currently possible merges. We prove that the radius (or diameter) of every k-clustering computed by complete linkage is at most by factor O(k) (or O(k²)) worse than an optimal k-clustering minimizing the radius (or diameter). Furthermore we give a negative answer to the question proposed by Dasgupta and Long [Sanjoy Dasgupta and Philip M. Long, 2005], who show a lower bound of Ω(log(k)) and ask if the approximation guarantee is in fact Θ(log(k)). We present instances where complete linkage performs poorly in the sense that the k-clustering computed by complete linkage is off by a factor of Ω(k) from an optimal solution for radius and diameter. We conclude that in general metric spaces complete linkage does not perform asymptotically better than single linkage, merging the two clusters with smallest inter-cluster distance, for which we prove an approximation guarantee of O(k)
Noisy, Greedy and Not so Greedy k-Means++
No full textThe k-means++ algorithm due to Arthur and Vassilvitskii [David Arthur and Sergei Vassilvitskii, 2007] has become the most popular seeding method for Lloyd’s algorithm. It samples the first center uniformly at random from the data set and the other k-1 centers iteratively according to D²-sampling, i.e., the probability that a data point becomes the next center is proportional to its squared distance to the closest center chosen so far. k-means++ is known to achieve an approximation factor of (log k) in expectation.
Already in the original paper on k-means++, Arthur and Vassilvitskii suggested a variation called greedy k-means++ algorithm in which in each iteration multiple possible centers are sampled according to D²-sampling and only the one that decreases the objective the most is chosen as a center for that iteration. It is stated as an open question whether this also leads to an (log k)-approximation (or even better). We show that this is not the case by presenting a family of instances on which greedy k-means++ yields only an Ω(⋅log k)-approximation in expectation where is the number of possible centers that are sampled in each iteration.
Inspired by the negative results, we study a variation of greedy k-means++ which we call noisy k-means++ algorithm. In this variation only one center is sampled in every iteration but not exactly by D²-sampling. Instead in each iteration an adversary is allowed to change the probabilities arising from D²-sampling individually for each point by a factor between 1-ε₁ and 1+ε₂ for parameters ε₁ ∈ [0,1) and ε₂ ≥ 0. We prove that noisy k-means++ computes an (log² k)-approximation in expectation. We use the analysis of noisy k-means++ to design a moderately greedy k-means++ algorithm
The Definitive Guide to NetBeans Platform
No full textThe Definitive Guide to NetBeans(t) Platform is a thorough and definitive introduction to the NetBeans Platform, covering all its major APIs in detail, with relevant code examples used throughout. The original German book on which this title is based was well received. The NetBeans Platform Community has put together this English translation, which author Heiko Bock updated to cover the latest NetBeans Platform 6.5 APIs. With an introduction by known NetBeans Platform experts Jaroslav Tulach, Tim Boudreau, and Geertjan Wielenga, this is the most up-to-date book on this topic at the moment. Al
An adaptive system for patient-controlled analgesia vol.1
No full textVolume 2 is the actual data. Please contact the author for this information. Heiko Rudolph [[email protected]] http://www.set.rmit.edu.au/~e55643/Deposited with permission of the author. © 1995 Dr. Heiko E. R. Rudolph.Patient-Controlled Analgesia (PCA) has become accepted as an important means of self-regulated relief from post-surgical pain. In commonly used PCA systems, patients use a hand-held push-button to indicate the presence of pain and initiate a predetermined bolus of drug infusion. A disadvantage of this system is that no means is provided to accommodate variations in the intensity of pain or the sensitivity of the patient to the analgesic in use apart from the frequency of button pushing. A fixed rate background infusion is usually an option. A new adaptive PCA system is proposed to provide improved PCA through the use a variable background infusion, the provision for an extended high range of analgesic dosages and a novel handset which allows patients to rate their pain. The total system is under the control of an expert algorithm and is proposed to overcome some of the shortcomings of current systems. (For complete abstract open document
Bicycle Ambulances in rural Uganda - Analysis of factors influencing its usage
No full textThis article reports on a study undertaken to analyze the usage of the bicycle ambulances in Uganda. Since 1997, approximately 400 bicycle ambulances have been distributed to villages in rural Uganda to improve accessibility to health centers. Approximately 20% of the population of Uganda have to travel more than 5 km to a health center, in a country where most transportation is by foot. A bicycle ambulance is a bicycle with an attached trailer used to transport seriously sick patients up to 15 km. The author conducted guided interviews with receivers and the distributors of bicycle ambulances in selected villages. Factors have been defined that influence the usage of bicycle ambulances, including individual village characteristics, the features of the bicycle ambulance, the system of distribution, and the organization of the groups using the bicycle ambulances. The distance to the health center, nor the distance to the main road and quality of the road itself significantly influenced the usage of the bicycle ambulance. The frequency of usage of the bicycle ambulances was limited to a few cases in a month or year. The only significant influence on the frequency of usage was observed based on the different organizational structures of the bicycle ambulance groups. The author considers some of the barriers to use, including long distances to health centers and costs of repairs, but notes that these and other barriers can be overcome through the positive attitude of group members
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