Prioritized demand assignment protocols and their evaluation

A class of message-based or station-based priority protocols for demand-assignment-based local area networks (LANs), such as Token Bus, HYPERbus, LCN, etc., is defined. It is shown how existing priority protocols can be represented within this class and how they can be extended for a more efficient realization with regard to both delay and capacity of prioritized channel access in LANs. An analytic approach for analyzing multiple-access systems operating under prioritized demand assignment protocols is introduced. The approach permits the modeling of station-dependent and priority-dependent arrival rates and generally distributed transmission times. The introduced finite-population model is especially appropriate for prioritized systems where the number of users per priority class is typically small and users place different service demands on the system. For modeling systems with large populations of users, an approximate model, which is shown to be significantly more computationally efficient than the exact model without imposing additional modeling restrictions, is introduced     

IPSEP-COLA: an incremental procedure for separation constraint layout of graphs

Existing information-visualization techniques that target small screens are usually limited to exploring a few hundred items. In this article we present a scatterplot tool for personal digital assistants that allows the handling of many thousands of items. The application's scalability is achieved by incorporating two alternative interaction techniques: a geometric-semantic zoom that provides smooth transition between overview and detail, and a fisheye distortion that displays the focus and context regions of the scatterplot in a single view. A user study with 24 participants was conducted to compare the usability and efficiency of both techniques when searching a book database containing 7500 items. The study was run on a pen-driven Wacom board simulating a PDA interface. While the results showed no significant difference in task-completion times, a clear majority of 20 users preferred the fisheye view over the zoom interaction. In addition, other dependent variables such as user satisfaction and subjective rating of orientation and navigation support revealed a preference for the fisheye distortion. These findings partly contradict related research and indicate that, when using a small screen, users place higher value on the ability to preserve navigational context than they do on the ease of use of a simplistic, metaphor-based interaction style     

Free-Surface Viscous Flow Solution Methods for Ship Hydrodynamics

The simulation of viscous free-surface water flow is a subject that has reached a certain maturity and is nowadays used in industrial applications, like the simulation of the flow around ships. While almost all methods used are based on the Navier-Stokes equations, the discretisation methods for the water surface differ widely. Many of these highly different methods are being used with success.     

Matrix Factorization Techniques for Recommender Systems

As the Netflix Prize competition has demonstrated, matrix factorization models are superior to classic nearest-neighbor techniques for producing product recommendations, allowing the incorporation of additional information such as implicit feedback, temporal effects, and confidence levels.     

Recent developments in monolithic integration of InGaAsP/InP optoelectronic devices

Monolithically integrated optoelectronic circuits combine optical devices such as light sources (injection lasers and light emitting diodes) and optical detectors with solid-state semiconductor devices such as field effect transistors, bipolar transistors, and others on a single semiconductor crystal. Here we review some of the integrated circuits that have been realized and discuss the laser structures suited for integration with emphasis on the InGaAsP/InP material system. Some results of high frequency modulation and performance of integrated devices are discussed.     

Planar buried heterostructure InP/GaInAs lasers grown entirely by OMVPE

GaInAs/InP planar buried heterostructure (PBH) lasers with semi-insulating blocking layers were grown in an `all? atmospheric OMVPE system. These layers had current thresholds as low as 35 mA and differential quantum efficiencies of ?16% at a wavelength of 1.64 ?m. The maximum power output was 80 mW pulsed and 8mWCW.     

Efficient V-V energy transfer in a multiphoton excited mixture of SF6and CF4

Spectral and temporal measurements of infrared fluorescence (IRF) in SF6, CF4, and mixtures of SF6and CF4gases excited by a pulsed CO2laser are reported. Using the 944.2 cm^-1[P(20)] laser line for excitation and measuring the IRF spectra between 700 and 1500 cm^-1, a strong red shifted IRF peak of the ν3mode in pure SF6was found. No IRF was observed under these conditions in pure CF4. In a 13:10 mixture of SF6and CF4, two strong IRF peaks of the ν3modes, shifted to the red relative to the room-temperature fundamentals at 948 cm^-1and 1283.2 cm^-1, were observed. The peaks are almost equal in height and since both molecules have almost the same ν3band intensity, the present result suggests that efficient intermolecularV-Venergy transfer occurs from excited SF6to cold CF4molecules. The temporal behavior of the IRF signals under high excitation (langlenrangle approx 6) in pure SF6exhibits two relaxation times, one of bulk cooling withtau_{1} approx 1ms and the other of aV-Tnature withPtau_{2} approx 20 mus . torr. In the mixture, an additional relaxation of the intermolecularV-Venergy transfer process is observed withPtau_{3} approx 10 mus . torr. The red shift dependence of the IRF peaks on the degree of excitation was also measured and used to examine population distributions, specific IRF transitions, and anharmonicity parameters.     

Value creation through design for scalability of reconfigurable manufacturing systems

Rapid and cost-effective scalability of the throughput of manufacturing systems is an invaluable feature for the management of manufacturing enterprises. System design for scalability allows the enterprise to build a manufacturing system to supply the current demand, and upgrade its throughput in the future, in a cost-effective manner, to meet possible higher market demand in a timely manner. To possess this capability, the manufacturing system must be designed at the outset for future expansions in its throughput to enable growths in supply exactly when needed by the market. A mathematical method that maximises the system throughput after reconfiguration is proposed, and an industrial case is presented to validate the method. The paper offers a set of principles for system design for scalability to guide designers of modern manufacturing systems.     

Operation of Manufacturing Systems with Work-in-process Inventory and Production Control

The operation of large manufacturing systems with buffers has two goals: to meet production target and minimize the work-in-process (WIP) inventory. This paper introduces a novel approach, based on optimal control theory, to achieve both goals simultaneously by on-line adjustment of the production rate of each machine. In this method the state variables are the buffer levels, the control variables are the machine production rates, and the output variable is the target production (the demand). The method is evaluated through simulations under various conditions, and compared with other methods in the literature. The results demonstrate that the proposed method can successfully produce low WIP inventory than other methods, while the required production demand is still fulfilled. It is also shown that the method is capable of providing feasible solutions for large manufacturing systems - a goal that is harder to achieve with the current known method.     

The Magnetometric System of the СПРУТ-VI Instrument Package

The magnetometric system of the -VI instrument package installed on board the Mir orbital station in 1999 is described. The system was a fluxgate magnetometer that enabled high-precwasion vector measurements (with a resolution of 0.1 nT for each component) of the magnetic field over a range of ±65000 nT. The operating temperature range of the sensing device was –170 to +80°C and the temperature range of the system electronics was –55 to +60°C. The system was used for studying fluctuations of the Earth's magnetic field and characteristics of various particle formations in near-equatorial and low latitudes as well as calculating the pitch-angle distribution of fluxes of charged particles and determining the exact spatial coordinates of isolated malfunctions in microcircuits.