Fractional derivatives and recurrent neural networks in rheological modelling – part I: theory

The aim of this paper was to develop a general approach based on fractional time derivatives and recurrent neural networks to model the rheological behaviour of asphalt materials. The paper focuses on elastic and viscoelastic material characteristics. It consists of two parts. In this first part, the theoretical aspects of modelling are discussed. A brief introduction into the theory of rheological elements based on fractional time derivatives is provided. The fractional differential equation of a general rheological element (base element) is developed from which a huge variety of other rheological elements can be derived, e.g. fractional Newton, Kelvin and standard solid elements. A new approach is presented for solving the fractional differential equations. Artificial neural networks are developed to compute the stress–strain–time behaviour of fractional rheological elements in a numerical efficient way. The approach is tested and verified. The second part of this work will appear later. It will be focused on applications of the new theoretical work to pavement engineering problems.     

On the cost of uniform protocols whose memory consumption is adaptive to interval contention

Recently, we introduced a novel term, memory-adaptive, whose goal it is to capture what it means for a distributed protocol to most efficiently make use of its shared memory. We proved three results that relate to the memory-adaptive model in the uniform setting. We considered a store/release protocol where processes are required to store a value in shared MWMR memory so that it cannot be overwritten until it has been released by the process. We showed that there do not exist uniformly wait-free store/release protocols using only the basic operations read and write that are memory-adaptive to point contention. We further showed that there exists a uniformly wait-free store/release protocol using only the basic operations read, write, and read-modify-write that is memory-adaptive to interval contention and time-adaptive to total contention. This left a significant gap — it remained open as to whether there exists a uniform, memory adaptive to interval contention store/release protocol that only uses read/write (no read-modify-write) registers. In this paper, we close this gap by showing that no such protocol can exist. We furthermore illustrate the validity and practicality of the concept of memory adaptiveness by providing a uniform, memory-adaptive to interval contention store/release protocol for Network Attached Disks.     

Growth of underwater communication technology in the U.S. Navy

Research and development in underwater communications is expanding in the U.S. Navy. Although there is no single Navy program office whose primary aim is to develop underwater telemetry systems, the Office of Naval Research has made a significant investment in both theoretical and applied work over the past twenty years and currently funds multiple programs in acoustic communication. Increased throughput, better power efficiency, low probability of detection, and compact implementations are all important research topics.     

The effect of a sodium octacosanoate‐based nucleating agent on the crystallization of thermoplastic polyurethanes

Sodium octacosanoate (NaC_28‐32) is commonly used as a nucleating agent in polyester and polyamide formulations. In this work, the effect of adding this agent to three chemically identical thermoplastic polyurethanes (TPUs), but with distinct molecular weights, was addressed, focusing on the study of the crystallization phenomenon. The modified Avrami and Avrami‐Ozawa kinetic models were applied to the isothermal and non‐isothermal crystallization processes, respectively, and both indicated faster crystallization when the nucleating agent was used, with an increase in temperature and rate of crystallization of the TPU. Such effect was partly attributed to the formation of a larger number of crystallization nuclei in comparison to the neat TPU. Besides, the nucleating effect was more pronounced for the TPU with the lowest molecular weight (30,000 Dalton). The Avrami and Avrami‐Ozawa models indicated that the TPU crystallization process occurs with the development of two‐dimensional lamellar aggregates, axialites, and that the incorporation of thenucleating agent does not alter this geometry. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Differential interference contrast x-ray microscopy with twin zone plates

X-ray imaging in differential interference contrast (DIC) with submicrometer optical resolution was performed by using a twin zone plate (TZP) setup generating focal spots closely spaced within the TZP spatial resolution of 160 nm. Optical path differences introduced by the sample are recorded by a CCD camera in a standard full-field imaging and by an aperture photodiode in a standard scanning transmission x-ray microscope. Applying this x-ray DIC technique, we demonstrate for both the full-field imaging and scanning x-ray microscope methods a drastic increase in image contrast (approximately 20x) for a low-absorbing specimen, similar to the Nomarski DIC method for visible-light microscopy.     

The road to RoboCup 2050

The ultimate goal of the RoboCup initiative is stated as follows: by mid-21st century, a team of fully autonomous humanoid robot soccer players shall win the soccer game, comply with the official rule of the FIFA, against the winner of the most recent World Cup. The authors consider this goal from the perspective of how close we are to it and what has to be done to reach it     

Stoßstrom und Stoßdrehmoment von Drehstrommaschinen beim simultanen dreipoligen,zweipoligen und nichtsimultanen dreipoligen Kurzschluß

Zusammenfassung Beim dreipoligen und zweipoligen Kurzschluß von Drehstrommaschinen treten große Strom- und Drehmomentstöße auf. Sie werden unter Vernachlässigung der Abklingvorgänge und bei Annahme subtransienter Symmetrie der Maschine (x _d ^/ =x _q ^/ ) berechnet. Beim zweipoligen Kurzschluß im Spannungsnulldurchgang ergeben sich um 13% kleinere Stromstöße als beim simultanen dreipoligen Kurzschluß (gleichzeitiges Kurzschließen der drei Pole). Die Drehmomentstöße sind dagegen beim zweipoligen Kurzschluß um 30% größer. In der Praxis ist auch ein nichtsimultaner dreipoliger Kurzschluß (nacheinander folgendes Kurzschließen der drei Pole) möglich. Hierbei treten beim Kurzschließen im Spannungsnulldurchgang sowohl um 18% größere Stromstöße als auch um 41% höhere Drehmomentstöße auf als beim simultanen dreipoligen Kurzschluß.     

Anagrelide in control of myeloproliferative thrombocythemia: long-term experiences in 6 patients

Symptomatic or asymptomatic chronic elevation of platelet count can be observed in all forms of myeloproliferative disorders (MPD). Benefits and limitations of the traditional platelet-reducing agents, such as radioactive phosphorus, alkylating agents, hydroxyurea and interferon alpha, are well known and have been largely described. Anagrelide (Agrelin) is an additional newer drug with a selective platelet-lowering effect. We describe our own long-term experience in 6 patients with MPD who were treated with anagrelide as part of a compassionate-use protocol between April 1991 and August 1997. The median duration of therapy was 54 months (range 17 to 75 months), with an overall response rate of 100% (complete and partial response for at least 4 weeks). The initial median platelet count of 1211 x 10(9)/l (range 847 to 2050 x 10(9)/l) was reduced rapidly and lastingly to 570 x 10(9)/l (range 216 to 667 x 10(9)/l) at the time of the last control. Under treatment with anagrelide 4 of the 6 patients showed a reduction of disease-associated symptoms or complications. Adverse reactions were generally mild and transitory, and no interruption or cessation of therapy was required. Development of drug resistance or late adverse events were not observed. Treatment with anagrelide is effective, safe and in our opinion easy to administer. It also appears to be suitable for long-term administration.