Chua's Circuit in Spread Spectrum Communication Systems

Communication system via chaotic modulations is demonstrated. It contains the well-known chaotic circuits as its basic elements - Chua's circuits. The proposed system has some standard properties of spread spectrum communication. The following advantage is found in simulations: a) Transmitted signals have broad spectra. b) Secure communications are possible in the sense that the better parameter matching is required in order to recover the signal. c) The circuit structure of the communication system is most simple and communication systems are easily built at a small outlay. Finally computer simulations are given to examine the validity of this system

Compensation of Wall Effect for Through Wall Tracking of Moving Targets

Through wall tracking of moving targets is of interest for rescue, surveillance and security operations. A useful method applies an ultra-wideband radar approach for this purpose since electromagnetic waves in the lower GHz- range penetrate most common building materials, such as bricks, wood, dry walls, concrete and reinforced concrete. However in consequence of a wall effect, estimated target track can be considerably spatially shifted and distorted. In the paper, two different methods for compensation of this ef- fect are described. Their effectiveness is evaluated at syn- thetic as well as real radar data. Obtained results prove that proposed novel approach reach the best outcomes

BAMUD Features Demonstration by System View

Direct-sequence code-division multiple access (DS-CDMA) is a frequently used wireless technology in DS-CDMA communications. The conventional DS-CDMA detector follows a single-user detection strategy in which each user is detected separately without regard for the other users. The better strategy is multi-user detection (MUD), where information about multiple users is used to improve detection of each individual user. This paper presents an adaptive multi-user detector converging (for any initialization) to the minimum mean square error (MMSE) detector without requiring training sequences. This blind multi-user detector (BAMUD) requires no more knowledge than does the conventional single-user detector. The structure of adaptive blind detector is simulated by the system design tool SystemView. The aim focus is to verify theoretical knowledge of BAMUD structure using hardware-oriented PC-based model in SystemView

Effects of Spreading Sequences on the Performance of MC-CDMA System with Nonlinear Models of HPA

Performance evaluation and comparison of multi-carrier code division multiple access (MC-CDMA) system model for different spreading sequences at the presence of Saleh and Rapp model of high power amplifier (HPA) is investigated. Nonlinear amplification introduces degradation of bit error performance and destroys the orthogonality among subcarriers. In order to avoid performance degradation without requiring extremely large backoffs in the transmitter amplifier, it becomes convenient to use nonlinear multi-user detection techniques at the receiver side. In order to illustrate this fact, microstatistic multi-user receiver (MSF-MUD) and conventional minimum mean square error receiver (MMSE-MUD) are considered and mutually compared. The results of our analyses based on computer simulations will show very clearly, that the application of nonlinear MSF-MUD in combination with Golay codes can provide significantly better results than the other tested spreading codes and receivers. Besides this fact, a failure of Walsh codes especially at the Saleh model of HPA will be outlined by using constellation diagram

Time of Arrival Complementing Method for Cooperative Localization of a Target by Two-Node UWB Sensor Network

Recently, the detection, localization and tracking of moving persons in emergency situations using ultra-wideband (UWB) sensors have attracted the attention of researchers and final users as well. Experiences with single UWB sensors in real applications have shown that their reliability and accuracy in person detection and localization may be considerably reduced. In contrast, the improved performance of a UWB sensor-based localization system can be provided by a UWB sensor network, which benefits from cooperation among spatially distributed sensor nodes. This cooperation extends the coverage of the monitored area and improves detection capability and localization performance, especially in the case of complex environments and multiple targets. In this paper, we will introduce a new approach to cooperative localization of a target, referred to as the time of arrival complementing method (TOACOM). TOACOM, developed for a two-node UWB sensor network, is based on the time of arrival (TOA) complementing and combining algorithms in combination with the conventional direct calculation method (DC). Its properties will be analyzed for through-the-wall single moving person localization. The obtained results will show the superior performance of TOACOM as compared with person localization by a single UWB sensor, or by a two-node sensor network. In the conclusion, we will outline that the presented version of TOACOM can be further modified for a multiple target scenario and an N-node sensor network

Subsynchronous Vibration Problem And Solution In Multistage Centrifugal Compressor.

LecturePg. 65-74The investigation of a subsynchronous vibration problem encountered in a six stage centrifugal compressor is discussed. At a running speed of approximately 9000 rpm, a subsynchronous vibration (at 4200 rpm) of nearly two times the synchronous vibration level was encountered. A systematic program was undertaken to identify the problem and correct it. A detailed analysis of the floating ring annular oil seals, balance piston labyrinth seals and impeller aerodynamic cross coupling was conducted. The oil seals were identified as the primary cause of the subsynchronous vibration due to lock up, and a modified seal design incorporating circumferential grooves was developed. This radically reduced the seal cross coupled stiffness. Further, a modified bearing design was investigated to increase the rotor logarithmic decrement. Changes were implemented in the compressor with the result of no subsynchronous vibrations for the operating conditions of the compressor thus far

Paying for parking : improving stated-preference surveys

This article describes an experiment which introduced random ranges into the variables used for the design of a stated preference survey and its effects on willingness to pay for parking. User behaviour at the time of parking was modelled to determine their willingness to pay in order to get to their final destination more quickly. Calculating willingness to pay is fundamental during the social and economic assessment of projects. It is important to correctly model how car parks and their users interact in order to get values which represent reality as closely as possible. Willingness to pay is calculated using a stated preference survey and by calibrating multinomial logit models, taking variable tastes into account. It is shown that a value with a low variability can be obtained for willingness to pay by correctly establishing the context of the choice and randomly changing the variables around an average value

A Fluorescence Reporter Model Defines “Tip-DCs” as the Cellular Source of Interferon β in Murine Listeriosis

Production of type I interferons, consisting mainly of multiple IFNα subtypes and IFNβ, represents an essential part of the innate immune defense against invading pathogens. While in most situations, namely viral infections, this class of cytokines is indispensable for host survival they mediate a detrimental effect during infection with L. monocytogenes by rendering macrophages insensitive towards IFNγ signalling which leads to a lethal bacterial pathology in mice. Due to a lack of suitable analytic tools the precise identity of the cell population responsible for type I IFN production remains ill-defined and so far these cells have been described to be macrophages. As in general IFNβ is the first type I interferon to be produced, we took advantage of an IFNβ fluorescence reporter-knockin mouse model in which YFP is expressed from a bicistronic mRNA linked by an IRES to the endogenous ifnb mRNA to assess the IFNβ production on a single cell level in situ. Our results showed highest frequencies and absolute numbers of IFNβ+ cells in the spleen 24 h after infection with L. monocytogenes where they were located predominately in the white pulp within the foci of infection. Detailed FACS surface marker analyses, intracellular cytokine stainings and T cell proliferation assays revealed that the IFNβ+ cells were a phenotypically and functionally further specialized subpopulation of TNF and iNOS producing DCs (Tip-DCs) which are known to be essential for the early containment of L. monocytogenes infection. We proved that the IFNβ+ cells exhibited the hallmark characteristics of Tip-DCs as they produced iNOS and TNF and possessed T cell priming abilities. These results point to a yet unappreciated ambiguous role for a multi-effector, IFNβ producing subpopulation of Tip-DCs in controlling the balance between containment of L. monocytogenes infection and effects detrimental to the host driven by IFNβ