Generating stochastic dispersed and periodic clustered textures using a composite hybrid screen.

In electrophotographic printing, a periodic clustered-dot halftone pattern is preferred for a smooth and stable result. In addition, the screen frequency should be high enough to minimize the visibility of the halftone textures and to ensure good detail rendition. However, at these frequencies, the halftone cell may contain too few pixels to provide a sufficient number of distinct gray levels. This will result in contouring and posterization. The traditional solution is to grow the clusters asynchronously within a repeating block of clusters known as a supercell. The growth of each individual cluster is governed by a microscreen. The order in which the clusters grow within the supercell is determined by a macroscreen. Typically, the macroscreen is a recursive pattern due to Bayer. In highlights and shadows, this ordering results in visible artifacts. Replacing the Bayer screen by a stochastic macroscreen eliminates these artifacts, but results in new artifacts. In this paper, we propose a new composite screen architecture that employs multiple microscreens and multiple macroscreens in the highlights and shadows. These screens are jointly designed by using the direct binary search (DBS) algorithm.     

B-spline explicit active surfaces: an efficient framework for real-time 3-D region-based segmentation

A new formulation of active contours based on explicit functions has been recently suggested. This novel framework allows real-time 3-D segmentation since it reduces the dimensionality of the segmentation problem. In this paper, we propose a B-spline formulation of this approach, which further improves the computational efficiency of the algorithm. We also show that this framework allows evolving the active contour using local region-based terms, thereby overcoming the limitations of the original method while preserving computational speed. The feasibility of real-time 3-D segmentation is demonstrated using simulated and medical data such as liver computer tomography and cardiac ultrasound images.     

Municipalities as a Driver for Wireless Broadband Access

Municipalities can form a driving force behind the deployment of new telecom infrastructure. While a telecom operator focuses on direct (financial) profits, a municipality is mainly interested in the social benefits for its inhabitants. In this paper, we evaluate a wireless municipality network from both a technical and an economic point of view. WiFi and WiMAX are considered as the most suited technologies for this purpose. A detailed techno-economic study has been performed including forecasting of the user adoption, dimensioning of the wireless network and modelling the related costs and revenues. The trade-off between installing a high number of relatively cheap WiFi access points, and a smaller number of more expensive WiMAX base stations for delivering full coverage is investigated in several scenarios.

Approach to stress tests in SIP environment based on marginal analysis

In the field of performance metrics and measurements of SIP (Session Initiation Protocol) Proxy and B2BUA (Back-to-Back User Agent) no standardized methodology has been presented yet. This gap results in a problematic determination of a hardware, the performance of which would be cost-effective and sufficient for the running the SIP Server in a given environment. Today practice relies on the administrator’s skills and experience with the needs of the telephony infrastructure. From this and the increasing usage of SIP based VoIP technologies come the main reasons for creating a methodology that would allow administrators to precisely measure the SIP Server performance and compare it to other software and hardware platform. This work also utilizes SIP Server performance measurements to comparison the results taken when transcoding was in use and when it was not and provides the means for comparison of B2BUAs platform independently.     

Intensity dependent but temperature independent charge carrier generation in organic photodiodes and solar cells

Measurements of the transient photoresponse of organic photodiodes and solar cells show a strong saturation effect in the quantum efficiency at laser fluences above approximately 3.3 μJ/cm². By a comparison of the measured intensity, temperature and field dependence of the transient pulse responses with extended drift–diffusion simulations, the loss of charge carriers can be traced back to a quadratic loss channel in the charge carrier generation process. In contrast to the predictions of the commonly used Onsager–Braun charge carrier generation model, we demonstrate that the dissociation of bound electron–hole-pairs is temperature independent but slightly field dependent.     

Full CMOS continuous time filters for GSM applications

This paper describes full cmoscontinuous time filter design techniques which can meet the specifications commonly set for gsmapplications. First several cmosfilter design techniques are overviewed. The ota-ctechnique is discussed to some more detail. To overcome the main drawback of the lower total harmonic distortion in ota-ctechniques very linear operational transconductance amplifiers (ota)are required. Such an ota,together with the applied linearisation techniques is discussed. To fulfil high accuracy in cut- off frequencies of the filter an active tuning system is necessary. A new on- chip tuning system is presented. The paper concludes with a practical design example for the gsmsystem. Therein the different ota-ctechniques discussed are illustrated.     

A novel propagation modeling for microcellular communications inurban environments

A novel method for microcellular communications to predict propagation characteristics is presented in this paper. It takes into account multiple reflections among walls, ground, vehicles, as well as the transmission/reflection due to groups of trees. Although these are three-dimensional (3-D) problems, we can combine two-dimensional (2-D) ray tracing and simple 3-D geometric considerations to solve them in a very efficient way. We have investigated the propagation loss versus size, number, and locations of vehicles and groups of trees on a safe island. Our results show that the radio wave propagation exhibits severe fast fading, attenuation, and blockage due to reflection, transmission, and shadowing, respectively     

A Channel Borrowing Approach for Cluster-based Hierarchical Wireless Sensor Networks

Mobile Networks and Applications - In Wireless Sensor Networks (WSNs), energy-efficient routing is required to conserve the scarce resources of these networks. Various energy-efficient routing...     

Characterization of charge trapping in SiO2/Al2O3 dielectric stacks by pulsed C–V technique

In this work, charge trapping in SiO₂/Al₂O₃ dielectric stacks is characterized by means of pulsed capacitance–voltage measurements. The proposed technique strongly reduces the measurement time and, as a consequence, the impact of charge trapping on the measurement results. Flat band voltage shift and fast current transient during short stress pulses are systematically monitored and the centroid and the amount of the trapped charge are extracted using a first-order model.