bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delay management in delay‐tolerant networks
Authors: Zheng Qunwei , Hong Xiaoyan , Wang Pu , Tang Lei , Liu Jun 
Published: August 2008

AbstractIn delay‐tolerant networks (DTN), nodes explore various opportunities to connect and communicate with each other. A series of encounters of different nodes will create such opportunities and spread a message among many nodes and eventually deliver to the designated destination. We study one common DTN scenario where the message exchanges happen when nodes meet others at certain locations. In this situation, the success of message delivery and the quality of the delivery depend highly on the likeliness of nodes' encounters and time elapsed between encounters. We study two important qualities of service requirements: the probability of two nodes meeting each other (encounter probability) and the time it takes for two nodes to meet (encounter delay). The key considerations are how nodes pick their next locations (mobility patterns) and the features of the dwell time. In this paper, we will study several mobility patterns, including random movement, and activity agenda based movement. We also study an additional message delivery constraint, i.e., a message will be dropped if not delivered within a limited number of locations visited. We develop mathematical formulas using Markov chain as a main tool. Our work is presented as an illustration through case studies. The methodology applies to mobility models alike and is extendable to real trace analysis. We present numerical results when closed form formulas cannot be acquired. Our results help the management of message delivery for DTN, e.g., in selecting a proper time‐to‐live threshold for a message. Copyright © 2008 John Wiley & Sons, Ltd.
Development and application of reduced‐order modeling procedures for subsurface flow simulation
Authors: Cardoso M. A. , Durlofsky L. J. , Sarma P. 
Published: August 2008

AbstractThe optimization of subsurface flow processes is important for many applications, including oil field operations and the geological storage of carbon dioxide. These optimizations are very demanding computationally due to the large number of flow simulations that must be performed and the typically large dimension of the simulation models. In this work, reduced‐order modeling (ROM) techniques are applied to reduce the simulation time of complex large‐scale subsurface flow models. The procedures all entail proper orthogonal decomposition (POD), in which a high‐fidelity training simulation is run, solution snapshots are stored, and an eigen‐decomposition (SVD) is performed on the resulting data matrix. Additional recently developed ROM techniques are also implemented, including a snapshot clustering procedure and a missing point estimation technique to eliminate rows from the POD basis matrix. The implementation of the ROM procedures into a general‐purpose research simulator is described. Extensive flow simulations involving water injection into a geologically complex 3D oil reservoir model containing 60 000 grid blocks are presented. The various ROM techniques are assessed in terms of their ability to reproduce high‐fidelity simulation results for different well schedules and also in terms of the computational speedups they provide. The numerical solutions demonstrate that the ROM procedures can accurately reproduce the reference simulations and can provide speedups of up to an order of magnitude when compared with a high‐fidelity model simulated using an optimized solver. Copyright © 2008 John Wiley & Sons, Ltd.
Classical and enriched finite element formulations for Bloch‐periodic boundary conditions
Authors: Sukumar N. , Pask J. E. 
Published: August 2008

AbstractIn this paper, classical and enriched finite element (FE) formulations to impose Bloch‐periodic boundary conditions are proposed. Bloch‐periodic boundary conditions arise in the description of wave‐like phenomena in periodic media. We consider the quantum‐mechanical problem in a crystalline solid and derive the weak formulation and matrix equations for the Schrödinger and Poisson equations in a parallelepiped unit cell under Bloch‐periodic and periodic boundary conditions, respectively. For such second‐order problems, these conditions consist of value‐ and derivative‐periodic parts. The value‐periodic part is enforced as an essential boundary condition by construction of a value‐periodic basis, whereas the derivative‐periodic part is enforced as a natural boundary condition in the weak formulation. We show that the resulting matrix equations can be obtained by suitably specifying the connectivity of element matrices in the assembly of the global matrices or by modifying the Neumann matrices via row and column operations. The implementation and accuracy of the new formulation is demonstrated via numerical examples for the three‐dimensional Poisson and Schrödinger equations using classical and enriched (partition‐of‐unity) higher‐order FEs. Copyright © 2008 John Wiley & Sons, Ltd.
On the numerical solution of hyperbolic PDEs with variable space operator
Authors: Ashyralyev Allaberen , Koksal Mehmet Emir 
Published: August 2008

AbstractThe first and second order of accuracy in time and second order of accuracy in the space variables difference schemes for the numerical solution of the initial‐boundary value problem for the multidimensional hyperbolic equation with dependent coefficients are considered. Stability estimates for the solution of these difference schemes and for the first and second order difference derivatives are obtained. Numerical methods are proposed for solving the one‐dimensional hyperbolic partial differential equation. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2009
Effects of γ radiation on fiber‐reinforced polymer concrete
Authors: Martínez‐Barrera Gonzalo , Giraldo Luis F. , López Betty L. , Brostow Witold 
Published: August 2008

AbstractComposites were made from 30% unsaturated polyester resin + 70% calcium bentonite and marble as aggregates, as well as 0.3 and 0.4 vol% of nylon fibers. The fiber‐containing polymer concretes (PCs) were subjected to 5, 10, 50, and 100 kGy applied radiation doses. The compressive strength values depend on both the fiber concentration and the irradiation dose applied. Moreover, the polyester‐based PCs containing two mineral aggregates, calcium carbonate and marble, have lower compressive strength values than those reported earlier for PCs containing only either silica sand or CaCO3. However, significant improvement of the compressive strain and the compression modulus of elasticity are achieved when nylon fibers are added. Both these properties go symbatically with the radiation dose. Mechanical characteristics can be related to the morphological features observed by scanning electron microscopy. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Physical and mechanical properties of dental nanocomposites composed of aliphatic epoxy resin and epoxidized aromatic hyperbranched polymers
Authors: Zhang Yujie , Zhang Daohong , Qin Chuangye , Xu Jingwei 
Published: August 2008

AbstractAliphatic epoxy resin (UVR6105) and epoxidized aromatic hyperbranched polymers (HBP) were used as dental resin matrixes, siliane‐treated inorganic nanoparticles as inorganic fillers, ethyl 4‐dimethylaminobenzoate, camphorquinone, and 4‐[(2‐hydroxytetradecyl)oxy] phenyl‐phenyliodoniumhexafluoroantimonate (CD1012) as initiators to formulate new kinds of dental nanocomposites. Their physical and mechanical properties were tested and the inner structure was observed by using scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The 7 series thermal analysis system was used to determine the glass transition temperature of dental resins. Compressive strengths of dental nanocomposites are lower, diametral tensile strengths are comparable with, flexural strengths are higher than those of commercial hybrid composite (Spectrum‐TPH). The addition of HBP decreased the glass transition temperature of aliphatic epoxy resin. SEM photo micrograph shows that the nanoparticles were well dispersed and inlayed in the resin matrixes. TEM photo micrograph shows that the inner structure of dental resins presents club‐shaped. Epoxidized aromatic hyperbranched polymer can strengthen and toughen aliphatic epoxy resin. These nanocomposites are potential for dental application. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Ins eigene Segel blasen. Münchhausen‐Effekt und Schubumkehr
Authors: Vollmer Michael , Möllmann Klaus‐Peter , Arnold Frank 
Published: August 2008

AbstractKann man sich mit seinem Segelboot fortbewegen, indem man ins eigene Segel bläst? Der Impulssatz erlaubt diesen an Münchhausen erinnernden Effekt. Das demonstriert ein vereinfachtes Gedankenexperiment, bei dem der Segler durch den Werfer eines Balls und das Segel durch eine starre Wand ersetzt wird. Allerdings ergibt die naive Theorie, die Luftmoleküle als ballähnliche Korpuskeln auffasst, einen zu hohen Impuls des reflektierten Luftstroms. Eine realistische Beschreibung liefert die moderne Strömungstheorie. Ihre Resultate sind experimentell erfolgreich umsetzbar. Technisch angewendet wird das Prinzip in der Schubumkehr von Flugzeugtriebwerken.
In den eisigen Welten des Saturn. Planetenforschung
Authors: Köhler Ulrich , Stephan Katrin , Wagner Roland 
Published: August 2008

AbstractCassini liefert seit vier Jahren wertvolle Experimentdaten aus der Welt des Saturn, seiner Ringe, von den Monden und der kosmischen Umgebung des zweitgrößten Planeten des Sonnensystems. Die Mission ermöglichte wichtige Erkenntnisse über die Prozesse, die im äußeren Sonnensystem seit der Bildung der Planeten abgelaufen sind. Diese Ergebnisse sind in vielerlei Hinsicht auch bedeutend für das Verständnis der Planeten im inneren Sonnensystem. Huygens ist erstmals auf dem Saturnmond Titan gelandet und hat Bilder und Messdaten von einem der interessantesten Körper im Sonnensystem geliefert. Seit dem 1. Juli 2008 befindet sich die Mission Cassini in einer ersten Verlängerungsphase. Bis Mitte 2010 wird die Sonde weitere 60 Mal Saturn umrunden.
Künstlicher Kugelblitz. Leuchtende Plasmabälle im Labor
Authors: Fußmann Gerd 
Published: August 2008

AbstractOb Kugelblitze in der Natur existieren, ist bislang unbewiesen. Im Labor lassen sich ähnliche Phänomene produzieren. Besonders interessant sind autonome Objekte, die ohne externe Energiezufuhr leuchten. Derzeit gibt es zwei Methoden, diese im Labor zu erzeugen. Bei einer entstehen Leuchtkugeln aus Silizium‐Aerosol, die bis zu 8 s lang existieren. Sie sind aber klein und schweben nicht, was den meisten Augenzeugenberichten über Kugelblitze widerspricht. Die zweite Methode erzeugt mit Elektroden in einem Wasserbehälter eine Gleitentladung an der Wasseroberfläche. Dabei entsteht ein Plasmoid, das etwa 0,3 s lang exisitert. Diese Kugel ist zunächst bis zu 20 cm groß. Sie steigt auf, verformt sich zu einem Pilz und schließlich zu einem Ring. Ihre Leuchtquelle ist chemische Energie. Solche Experimente können die Existenz von natürlichen Kugelblitzen allerdings noch nicht sicher beweisen.
Funkenüberschlag
Authors: Loos Andreas 
Published: August 2008

AbstractFrisch promoviert und staatsexaminiert darf er Mathematik, Physik, Chemie und Mineralogie bis zur Obertertia unterrichten. Doch das ist Plan B – eigentlich will er sich habilitieren. Schließlich, so glaubt er von sich, werde er “den Ansprüchen, die man an einen Physiker mittleren Ranges zu stellen berechtigt ist, mit der Zeit genügen.”
Frittierphysik für perfekte Pommes
Authors: Vilgis Thomas 
Published: August 2008

AbstractDer Ruf von Pommes Frites ist nicht gerade der beste. Mitunter sind sie von Fett durchtränkt, was nicht nur Ernährungsfachleute in Rage versetzt, sondern auch den Genuss deutlich beeinträchtigt. Das eingedrungene Frittierfett verhindert nämlich die wichtigste mechanische Eigenschaft der Fritten: die krachende Knusprigkeit der Hülle und das kartoffelige Innenleben. Mit physikalischer Frittiertheorie lassen sich derartige Unwägbarkeiten verhindern.
No indications of cognitive side‐effects in a prospective study of breast cancer patients receiving adjuvant chemotherapy
Authors: Mehlsen Mimi , Pedersen Anders Degn , Jensen Anders Bonde , Zachariae Robert 
Published: August 2008

AbstractObjective: A number of cross‐sectional studies have reported reduced cognitive function in cancer patients receiving chemotherapy compared with other cancer patients and healthy controls, suggesting that chemotherapy could be associated with cognitive side‐effects. Recently published prospective studies question this hypothesis, but it is still unclear whether cancer patients should regard cognitive problems as a potential risk when receiving chemotherapy.Methods: In the present study we examine whether cancer patients (n=34) receiving chemotherapy differed in cognitive changes during treatment compared with cardiac patients (n=12) and healthy controls (n=12) tested at 3–4 months interval.Results: Our results showed no differences with respect to changes in cognitive performance over time between cancer patients in chemotherapy, cardiac patients, and healthy controls. In addition, the number of individuals showing reliable decline or improvement on cognitive tests did not differ between groups.Conclusion: Taken together, our results do not support a hypothesis of cognitive side‐effects of standard‐dose chemotherapy in breast cancer patients. Copyright © 2008 John Wiley & Sons, Ltd.
Use of simulation to compare the performance of minimization with stratified blocked randomization
Authors: Toorawa Robert , Adena Michael , Donovan Mark , Jones Steve , Conlon John 
Published: August 2008

AbstractMinimization is an alternative method to stratified permuted block randomization, which may be more effective at balancing treatments when there are many strata. However, its use in the regulatory setting for industry trials remains controversial, primarily due to the difficulty in interpreting conventional asymptotic statistical tests under restricted methods of treatment allocation. We argue that the use of minimization should be critically evaluated when designing the study for which it is proposed. We demonstrate by example how simulation can be used to investigate whether minimization improves treatment balance compared with stratified randomization, and how much randomness can be incorporated into the minimization before any balance advantage is no longer retained. We also illustrate by example how the performance of the traditional model‐based analysis can be assessed, by comparing the nominal test size with the observed test size over a large number of simulations. We recommend that the assignment probability for the minimization be selected using such simulations. Copyright © 2008 John Wiley & Sons, Ltd.
A limiting distribution for the number of cuts needed to isolate the root of a random recursive tree
Authors: Drmota Michael , Iksanov Alex , Moehle Martin , Roesler Uwe 
Published: August 2008

AbstractLet Xn be the number of cuts needed to isolate the root in a random recursive tree with n vertices. We provide a weak convergence result for Xn. The basic observation for its proof is that the probability distributions of $\{X_n: n=2,3,\ldots\}$ are recursively defined by $X_n {{\rm d}\atop{=}} X_{n-D_n} + 1, \; n=2,3,\ldots, \; X_1=0$, where Dn is a discrete random variable with ℙ${\{ D_n = k \} = {1 \over {k(k+1)}} {n \over {n-1}}, \; k=1,2,\ldots, n-1}$, which is independent of $(X_2,\ldots, X_n)$. This distributional recursion was not studied previously in the sense of weak convergence. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Local resilience of graphs
Authors: Sudakov Benny , Vu V.H. 
Published: August 2008

AbstractIn this article, we initiate a systematic study of graph resilience. The (local) resilience of a graph G with respect to a property
$\cal {P}$
measures how much one has to change G (locally) to destroy $\cal {P}$. Estimating the resilience leads to many new and challenging problems. Here we focus on random and pseudorandom graphs and prove several sharp results. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008
An efficient method for accommodating potentially underpowered primary endpoints
Authors: Li Jianjun (David) , Mehrotra Devan V. 
Published: August 2008

AbstractIf a trial is adequately powered for two clinically important endpoints, A and B, each of which can fully characterize a treatment benefit to support a regulatory claim by itself, then both endpoints are usually labeled primary, and the trial is deemed positive if either endpoint is statistically significant after a multiplicity adjustment. However, if only A is adequately powered, then should B be designated a secondary endpoint, or should it be retained in the primary family despite being (potentially) underpowered? The former option can lead to a negative trial if A is not statistically significant, no matter how positive the results are for B, since no familywise type I error rate (FWER) is allocated to B, while the latter can reduce the likelihood of a positive trial if an inefficient multiplicity adjustment is used. We underscore this contemporary problem with real examples and offer a novel and intuitively appealing solution for accommodating clinically important but potentially underpowered endpoint(s) in the primary family. In our proposal, for the above scenario with two endpoints, A is tested at a prespecified level α1=α−ε (e.g. ε=0.01 when α=0.05), and B at an ‘adaptive’ level α2 (⩽α) calculated using a prespecified non‐increasing function of the p‐value for A. Our method controls the FWER at level α and can notably increase the probability of achieving a positive trial compared with a fixed prospective alpha allocation scheme (Control. Clin. Trials 2000; 20:40–49), and with Hochberg's method applied to the family of primary endpoints. Importantly, our proposal enables strong results for potentially underpowered primary endpoint(s) to be interpreted in a conclusive rather than exploratory light. Copyright © 2008 John Wiley & Sons, Ltd.
Standardized test outcomes for students engaged in inquiry‐based science curricula in the context of urban reform
Authors: Geier Robert , Blumenfeld Phyllis C. , Marx Ronald W. , Krajcik Joseph S. , Fishman Barry , Soloway Elliot , Clay‐Chambers Juanita 
Published: August 2008

AbstractConsiderable effort has been made over the past decade to address the needs of learners in large urban districts through scaleable reform initiatives. We examine the effects of a multifaceted scaling reform that focuses on supporting standards based science teaching in urban middle schools. The effort was one component of a systemic reform effort in the Detroit Public Schools, and was centered on highly specified and developed project‐based inquiry science units supported by aligned professional development and learning technologies. Two cohorts of 7th and 8th graders that participated in the project units are compared with the remainder of the district population, using results from the high‐stakes state standardized test in science. Both the initial and scaled up cohorts show increases in science content understanding and process skills over their peers, and significantly higher pass rates on the statewide test. The relative gains occur up to a year and a half after participation in the curriculum, and show little attenuation with in the second cohort when scaling occurred and the number of teachers involved increased. The effect of participation in units at different grade levels is independent and cumulative, with higher levels of participation associated with similarly higher achievement scores. Examination of results by gender reveals that the curriculum effort succeeds in reducing the gender gap in achievement experienced by urban African‐American boys. These findings demonstrate that standards‐based, inquiry science curriculum can lead to standardized achievement test gains in historically underserved urban students, when the curriculum is highly specified, developed, and aligned with professional development and administrative support. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 922–939, 2008
Comparison Between Open and Laparoscopic Repair of Perforated Peptic Ulcer Disease
Authors: Bhogal Ricky H. , Athwal Ruvinder , Durkin Damien , Deakin Mark , Cheruvu Chandra N. V. 
Published: August 2008

AbstractBackgroundThe place of laparoscopic repair of perforated peptic ulcer followed by peritoneal toilet has been established, although it is not routinely practiced. This prospective study compared laparoscopic and open repair of perforated peptic ulcer disease. We evaluated whether the early results from laparoscopic repair resulted in improved patient outcome compared with conventional open repair.MethodsAll patients who underwent repair of perforated peptic ulcer disease during a 12‐month period in our unit were included in the study. The primary end points that were evaluated were total operative time, nasogastric tube utilisation, intravenous fluid requirement, total time of urinary catheter and abdominal drainage usage, time taken to return to normal diet, intravenous/intramuscular opiate use, time to full mobilization, and total in‐patient hospital stay.ResultsThirty‐three patients underwent surgical repair of perforated peptic ulcer disease (19 laparoscopic repairs and 14 open repairs; mean age, 54.2 (range, 32–82) years). There was no increase in total operative time in patients who had undergone laparoscopic repair (mean: 61 minutes laparoscopic versus 57 minutes open). There was significantly less requirement for intravenous/intramuscular opiate analgesia in patients who had undergone laparoscopic repair (mean time to oral analgesia: 1.2 days laparoscopic versus 3.8 days open). In addition there was a significant decrease in the time that the nasogastric tube (mean: 2.1 days laparoscopic versus 3.1 days open), urinary catheter (mean: 2.3 days laparoscopic versus 3.7 days open) and abdominal drain (mean: 2.2 days laparoscopic versus 3.8 days open) were required during the postoperative period. Patients who had undergone laparoscopic repair required less intravenous fluids (mean: 1.4 days laparoscopic versus 3.1 days open) and returned to normal diet (mean: 2.3 days laparoscopic versus 4.8 days open) and full mobilization significantly earlier than those who had undergone open repair (mean: 2.3 days laparoscopic versus 3.3 days open). In addition, patients who had undergone laparoscopic repair required a shorter in‐patient hospital stay (mean: 3.1 days laparoscopic versus 4.3 days open).ConclusionsLaparoscopic repair is a viable and safe surgical option for patients with perforated peptic ulcer disease and should be considered for all patients, providing that the necessary expertise is available.
Surgical Education at the West African College of Surgeons
Authors: Bode Christopher Olusanjo , Nwawolo Clement Chukwuemeka , Giwa‐Osagie Osato Frank 
Published: August 2008

AbstractThe West African College of Surgeons (WACS) was formed almost 50 years ago to foster friendship and greater interaction amongst the first crop of surgeons of West African origin freshly returning from overseas training. Under the College’s umbrella, seven different surgical Faculties—Anaesthesiology, Dental Surgery, Obstetrics & Gynaecology, Ophthalmology, Otorhinolaryngology, Radiology/Radiotherapy, and Surgery—have been nurtured into viable entities. The WACS is a leading institution for surgical training, accreditation, and collaboration with international bodies in the subregion. With more than 3000 Fellows, the WACS’ surgical training programs and diplomas have remained the standard format for a population of >140 million in the five Anglophone West African countries for decades. The College has assumed increasing roles in attracting donor agencies as well as West Africans in the Diaspora desirous of establishing training links with credible institutions in the subregion. This paper discusses the history of the WACS, its examination process and other functions, as well as its contributions toward and challenges in surgical manpower development in the West African subregion.