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1
Chow, Mable Man Chee. "Low-complexity code shift keying over the wireless channel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ38623.pdf.
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Zettas, Spiridon. "Adaptive averaging channel estimation for DVB-T2 systems." Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16581.
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In modern communication systems, the rate of transmitted data is growing rapidly. This leads to the need for more sophisticated methods and techniques of implementation in every block of the transmitter-receiver chain. The weakest link in radio communications is the transmission channel. The signal, which is passed through it, suffers from many degrading factors like noise, attenuation, diffraction, scattering etc. In the receiver side, the modulated signal has to be restored to its initial state in order to extract the useful information. Assuming that the channel acts like a filter with finite impulse, one has to know its coefficients in order to apply the inverse function, which will restore the signal back to its initial state. The techniques which deal with this problem are called channel estimation. Noise is one of the causes that degrade the quality of the received signal. If it could be discarded, then the process of channel estimation would be easier. Transmitting special symbols, called pilots with known amplitude, phase and position to the receiver and assuming that the noise has zero mean, an averaging process could reduce the noise impact to the pilot amplitudes and thus simplify the channel estimation process. In this thesis, a novel channel estimation method based on noise rejection is introduced. The estimator takes into account the time variations of the channel and adapts its buffer size in order to achieve the best performance. Many configurations of the estimator were tested and at the beginning of the research fixed size estimators were tested. The fixed estimator has a very good performance for channels which could be considered as stationary in the time domain, like Additive White Gaussian Noise (AWGN) channels or slowly time-varying channels. AWGN channel is a channel model where the only distorting factor is the noise, where noise is every unwanted signal interfering with the useful signal. The properties of the noise are that it is additive, which means that the noise is superimposed on the transmitted signal, it is white so the power density is constant for all frequencies, and it has a Gaussian distribution in the time domain with zero mean and variance σ2=N. A slowly time varying channel refers to channel with coherence time larger than the transmitted symbol duration. The performance of a fixed size averaging estimator in case of fast time-varying channels is subject to the buffering time. When the buffering time is smaller or equal to a portion of the coherence time the averaging process offers better performance than the conventional estimation, but when the buffering time exceeds this portion of the coherence time the performance of the averaging process degrades fast. So, an extension has been made to the averaging estimator that estimates the Doppler shift and thus the coherence time, where the channel could be assumed as stationary. The improved estimator called Adaptive Averaging Channel Estimator (AACE) is capable to adjust its buffer size and thus to average only successive Orthogonal Frequency Division Multiplexing (OFDM) symbols that have the same channel distortions. The OFDM is a transmission method where instead of transmitting the data stream using only on carrier, the stream is divided into parallel sub-streams where the subcarriers conveying the sub-streams are orthogonal to each other. The use of the OFDM increases the symbol duration making it more robust against Inter-Symbol Interference (ISI), which the interference among successive transmitted symbols, and also divides the channel bandwidth into small sub-bandwidths preventing frequency selectivity because of the multipath nature of the radio channel. Simulations using the Rayleigh channel model were performed and the results clearly demonstrate the benefits of the AACE in the channel estimation process. The performance of the combination of AACE with Least Square estimation (AACE-LS) is superior to the conventional Least Square estimation especially for low Doppler shifts and it is close to the Linear Minimum Mean Square Error (LMMSE) estimation performance. Consequently, if the receiver has low computational resources and/or the channel statistics are unknown, then the AACE-LS estimator is a valid choice for modern radio receivers. Moreover, the proposed adaptive averaging process could be used in any OFDM system based on pilot aided channel estimation. In order to verify the superiority of the AACE algorithm, quantitative results are provided in terms of BER vs SNR. It is demonstrated that AACE-LS is 7dB more sensitive than the LS estimator.
3
Haghdad, Mehdi, and Kamilo Feher. "ADVANCE PRACTICAL CHANNEL SIMULATORS FOR LEO SATELLITE CHANNELS WITH SELECTIVE FADING AND DOPPLER SHIFTS." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607588.
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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>Dynamic hardware and software schemes for trajectory based simulation of LEO satellite channel are presented and evaluated. The simulation models are based on the practical LEO satellite channels and change dynamically with the trajectory using the latitude and longitude of the LEO satellite as input. The hardware simulator is consisted of a trajectory based selective fade generator, a trajectory based Doppler shifter, trajectory based time shadowing simulator and a standard channel for addition of noise, ACI and CCI. A FQPSK modulated signal is passed through a trajectory based dynamic fade generator and the spectrum is distorted. Then the resulting signal is exposed to a trajectory based dynamic Doppler Shifter, simulating the passage of the satellite overhead. Then the proper AWGN, ACI or CCI is added to the signal. At the final stage the signal is passed through a trajectory based time Shadowing simulator. The software simulator is a dynamic real time simulator written in MatLab and its structure is similar to the hardware simulator.
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Fofanah, Ibrahim, and Wannaw Assegu. "Delay Spread Characterization of the Aeronautical Channel." International Foundation for Telemetering, 2012. http://hdl.handle.net/10150/581653.
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ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California<br>Radio transmission channel influences greatly the quality of transmitted voice and data signal in terms of data rate and robustness. This degradation is as a result of many factors, notable amongst them are having multiple replica of the transmitted signal at the receiver (multipath), changes of frequency as a result of the movement of the aircraft (Doppler shift) and noise. This paper characterizes the scattered components of the aeronautical channel in terms of delay spread. Geometric representation is used to derive expressions for the maximum delay spread using the 2-ray model and the three dimensional model of the scattered path. Furthermore, the delay and Doppler frequencies are described as a function of the horizontal distance to the specular reflection point between a ground station and a test article. The simulated results are compared to measured data of related articles and the value of the maximum delay spread is compared with the proposed intersymbol guard band for Orthogonal Frequency Division Multiplexing (OFDM) in the Integrated Network Enhanced Telemetry (iNET) program to see if this proposition can be adapted to the aeronautical channel.
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Davidson, H. D. "A reliable data channel for underwater communications using phase shift keying." Thesis, University of Newcastle Upon Tyne, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233423.
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Alsharekh, Mohammed Fahad. "Transform domian/cyclic code shift keying system on an urban multipath channel." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1177003745.
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Long, Christopher C. "Data Processing for NASA's TDRSS DAMA Channel." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/611474.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California<br>Presently, NASA's Space Network (SN) does not have the ability to receive random messages from satellites using the system. Scheduling of the service must be done by the owner of the spacecraft through Goddard Space Flight Center (GSFC). The goal of NASA is to improve the current system so that random messages, that are generated on board the satellite, can be received by the SN. The messages will be requests for service that the satellites control system deems necessary. These messages will then be sent to the owner of the spacecraft where appropriate action and scheduling can take place. This new service is known as the Demand Assignment Multiple Access system (DAMA).
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Shaw, Christopher. "Adjacent Channel Interference for Turbo-Coded APSK." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606238.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, California<br>A study of the effects of interference caused by adjacent channels on the performance of turbo-coded 16- and 32-APSK. Included in our discussion is the spectral regrowth in the nonlinear power amplifier when driven by a non-constant envelope modulation. Ultimately, we present a set of channel spacing guidelines when using turbo-coded APSK for aeronautical telemetry.
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Ekanthalingam, Ravikanth. "Amplitude Estimation of Minimum Shift Keying in the presence of Co-channel interference." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1107802525.
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Mwangi, Patricia A. W., Amr Haj-Omar, and Kishan Montaque. "SIMULATION OF THE AERONAUTICAL RADIO CHANNEL FOR TELEMETRY APPLICATIONS." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604033.
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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California<br>The aeronautical channel is an air to ground channel characterized by multipath, high doppler shifts, Rayleigh fading and noise. Use of a channel sounder ensures proper estimation of the parameters associated with the impulse response of the channel. These estimates help us to characterize the radio channels associated with aeronautical telemetry. In order to have a satisfactory channel characterization, the amplitudes, phase shifts and delays associated with each multipath component in the channel model must be determined.
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Rodenbaugh, John Irvin. "Optimum detection of differentially-encoded M-ary phase-shift keying in a dispersive aeronautical channel." Ohio : Ohio University, 2002. http://www.ohiolink.edu/etd/view.cgi?ohiou1174934375.
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Al-Sharari, Hamed. "An implementation of acquisition using transform domain/cycle code shift keying system on a multipath channel." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1177004799.
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Potter, Chris. "Single Bounce Air to Ground Communication Channel Capacity for MIMO Applications." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604770.
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ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, California<br>This paper addresses the air-to-ground communication problem, where multiple transmit antennas
are used on the aircraft to combat multi-path interference. The channel is assumed to have a
line-of-sight component and a single ground reflection. Multiple input multiple output (MIMO)
techniques can be used in this situation, to increase the reliability and data rate. In this paper
we discuss how the MIMO channel capacity changes, with the aircraft antenna configuration,
altitude, velocity, range, and a number of other parameters. For comparison, the MIMO results
are compared to systems which have single antennas at the transmitter, at the receiver, or at both
ends.
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Ahmed, Sadia. "Channel Analysis and Estimation and Compensation of Doppler Shift in Underwater Acoustic Communication and Mitigation of IFI, ISI in Ultra-wideband Radio." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5408.
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Water occupies three fourth of earth's surface. The remaining one fourth is land. Although human habitats reside on land, there is no denying of the vital connection between land and water. The future sustainability of human species on this planet depends on wise utilization of all available resources, including that provided by the vast water world. Therefore, it is imperative to explore, understand, and define this massive, varying, and in many areas, unexplored water domain.
The water domain exploration and data collection can be conducted using manned or unmanned vehicles, as allowed by the water environment. This dissertation addresses three of the key difficulties that occur during underwater acoustic communication among manned and/or unmanned vehicles and proposes feasible solutions to resolve those difficulties. The focus and the contributions of this research involve the following perspectives:
1) Representation of Underwater Acoustic Communication (UAC) Channels: Providing a comprehensive classification and representation of the underwater acoustic communication channel based on the channel environment.
2) Estimation and Compensation of Doppler Shift: Providing compensation algorithm to mitigate varying Doppler shift effect over subcarriers in UAC Orthogonal Frequency Division Multiplexing (OFDM) systems.
3) Mitigation of Inter-symbol Interference (ISI): Providing feasible solution to long delay spread causing ISI in Ultra-wideband channels.
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Feher, Kamilo, Robert Jefferis, and Eugene Law. "Spectral Efficiency and Adjacent Channel Interference Performance Definitions and Requirements for Telemetry Applications." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607340.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>Organizations such as the National Telecommunications and Information Administration
(NTIA), Federal Communications Commission (FCC), International Telecommunications
Union (ITU) and various commercial entities use a wide range of spectral efficiency
criteria in different broadcast and wireless system applications. These criteria and related
specifications have significant differences. This paper briefly reviews some common
adjacent channel interference (ACI) definitions as well as issues surrounding the
definition of spectral efficiency. The impact of these parameters on system bit error rate
(BER) performance and closely "packed" adjacent signals is described. ACI criteria and
spectral efficiency definitions considered appropriate for existing telemetry applications
and deployment of new generations of spectrally efficient systems are illustrated. Specific
ACI and spectral efficiency performance requirements adopted by the Department of
Defense (DoD) and Advanced Range Telemetry (ARTM) project are highlighted.
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Conka, Tahir. "Performance analysis of noncoherent differential phase shift keying using Post-Detection Selection Combining over a Rayleigh fading channel." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA346398.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, June 1998.<br>Thesis advisor(s): Tri T. Ha, Ralph D. Hippenstiel. "June 1998." Includes bibliographical references (p. 77). Also available online.
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Kızıldağ, Eren C. "Improved magnetic resonance chemical shift imaging at 3 Tesla using a 32-channel integrated RF-shim coil array." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108976.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 87-93).<br>In vivo chemical shift imaging is an imaging modality which uses the so-called chemical-shift phenomenon to quantitate brain metabolites spatially, therefore renders the study of brain metabolism and neurodegenerative diseases possible and eases diagnosis of tumors. However, the method is highly vulnerable to local main magnetic field (Bo) inhomogeneities arising from magnetic susceptibility differences which is predominantly present in air-tissue interfaces. Such magnetic field inhomogeneities result in number of imaging artifacts including chemical shift displacement of metabolites, spectral line broadening as well as complicated water and lipid suppression; which reduce spectral quality. The main goal of this work is to compensate Bo imperfections and therefore mitigate aforementioned artifacts to earn enhanced spectral quality with the aid of a recently introduced, novel, 32-channel integrated RF-shim coil hardware. Experimental results indeed demonstrate sharper spectral lines with narrower line widths and improved water suppression performance in the regions with poor BO conditions with the application of the shim coil hardware.<br>by Eren C. Kizildag.<br>S.M.
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Basharati, Sarhad. "MIMO and Relay Systems Based on Multi-Amplitude Minimum Shift Keying." Thesis, University of Canterbury. Electrical and Computer Engineering, 2013. http://hdl.handle.net/10092/8491.
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This thesis describes the use of a multi-amplitude minimum shift keying (MAMSK) signal in various types of wireless communication system. A MAMSK signal is a bandwidth efficient modulation scheme obtained by superimposing ℳ minimum shift keying (MSK) signals with unequal amplitudes. The overall phase of a MAMSK signal is controlled by the phase of the largest component MSK signal which allows the use of a low-complexity differential detector. A closed form expression for the average bit error rate (BER) for coherent detection of an MAMSK in AWGN is derived and is shown to achieve the same BER as that of square constellation quadrature amplitude modulation (QAM) with the same average transmit power.
We describe the design and implementation of a STBC-based MIMO radio system in conjunction with MAMSK modulation. The proposed system provides high capacity data transmission by carrying information not only in the phases but also in the amplitude. Despite using a simple MAMSK differential receiver the system achieves performance within 1 dB of coherent detection. The existing MSK modems in conjunction with STBC could easily be modified to construct the proposed system.
The MAMSK modulation scheme is extended to a multiuser relaying network where two nodes cooperate in a half-duplex environment to achieve diversity gain. The cooperative scheme is based on superposition modulation using a decode-and-forward (DF) strategy. In the proposed scheme, each node simultaneously transmits its own and the relayed signals by superimposing one on the other. A MAMSK signal is an excellent choice for this type of cooperative communication due its being obtained by a superposition technique. The proposed system exploits the overall phase of a MAMSK signal which allows differential detection and as a result it provides the lowest decoding complexity and memory requirements among the existing superposition based cooperation schemes. The performance of the system is evaluated by simulation, where it is shown that the MAMSK cooperative system outperforms a conventional DF scheme in terms of both power and bandwidth efficiency.
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Moon, Todd K., and Chet Lo. "Bandwidth Efficient Signaling Using Multiscale Wavelet Functions and its Performance in a Rician Fast Fading Channel Employing Differential Detection." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608755.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada<br>In this paper, orthogonal wavelets are employed to produce multiscale signaling. It is shown that signaling using these functions is bandwidth efficient compared other signaling schemes, including SFSK and GMSK. For signaling in Rician fast fading channel, it is also shown that scaling functions is superior in term of achieving low level of probability of error. Even for multiscale signaling, the level probability of error achieved by using wavelet is lower than conventional flat-top signaling. The benefits are largest for channels with small B(D)T , in which the degradation due to fading is most severe.
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Boucher, Pierre-Alexandre. "Stress driven changes in the kinetics of bilayer embedded proteins: a membrane spandex and a voltage-gated sodium channel." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20034.
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Bilayer embedded proteins are affected by stress. This general affirmation is, in this thesis, embodied by two types of proteins: membrane spandex and voltage-gated sodium channels. In this work, we essentially explore, using methods from physics, the theoretical consequences of ideas drawn from experimental biology.
Membrane spandex was postulated to exist and we study the theoretical implications and possible benefits for a cell to have such proteins embedded in its bilayer. There are no specific membrane spandex proteins, rather any protein with a transition involving a large enough area change between two non-conducting states could act as spandex. Bacterial cells have osmovalve channels which open at near-lytic tensions to protect themselves against rupture. Spandex expanding at tensions just below the osmovalves’ opening tension could relieve tension enough as to avoid costly accidental osmovalve opening due to transient bilayer tension excursions. Another possible role for spandex is a tension-damper: spandex could be used to maintain bilayer tension at a fixed level. This would be useful as many bilayer embedded channels are known to be modulated by tension.
The Stress/shear experienced in traumatic brain injury cause an immediate (< 2 min) and irreversible TTX-sensitive rise in axonal calcium. In situ, this underlies an untreatable
condition, diffuse axonal injury. TTX sensitivity indicates that leaky voltage-gated sodium (Nav) channels mediate the calcium increase. Wang et al. showed that the mammalian adult CNS Nav isoform, Nav1.6, expressed in Xenopus oocytes becomes “leaky” when subjected to bleb-inducing pipette aspiration. This “leaky” condition is caused by a hyperpolarized-shift (left-shift or towards lower potentials, typically 20 mV) of the kinetically coupled processes of activation and inactivation thus effectively degrading a well-confined window conductance
into a TTX-sensitive Na leak. We propose experimental protocols to determine whether this left-shift is the result of an all-or-none or graded process and whether persistent Na currents are also left-shifted by trauma. We also use modeling to assess whether left-shifted Nav channel kinetics could lead to Na+ (and hence Ca2+ ) loading of axons and to study saltatory propagation after traumatizing a single node of Ranvier.
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Kontodios, Pierros. "Performance analysis of noncoherent Binary Frequency Shift Keying using Equal Gain Combining and Post Detection Selection Combining over a Nakagami fading channel." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA354305.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1998.<br>"September 1998." Thesis advisor(s): Tri T. Ha, Ralph D. Hippenstiel. Includes bibliographical references (p. 97). Also available online.
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Gao, Wei, Shih-Ho Wang, and Kamilo Feher. "TESTS AND EVALUATIONS OF ADAPTIVE FEHER EQUALIZERS FOR A LARGE CLASS OF SYSTEMS, INCLUDING FQPSK." International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/606772.
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International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California<br>Design and performance evaluation of a low-complexity equalizer for recently standardized spectral efficient Feher
patented quadrature phase shift keying (FQPSK) system [1] over multipath fading channel is presented. The
implementation based on a Feher patented equalizer (FE) [1] is of a structure with three branches, which are
individually used to compensate for a moving fade notch with different locations. These branches are switched by
the control signal that is generated based on pseudo-error on-line detection technique. It is demonstrated that for
typical aeronautical telemetry RF frequency selective fading channels, having delay spreads in 20 – 200 ns range,
the adaptive FE reduces the number of statistical outages by more than 60% without the need for training bits and
without increasing the receiver synchronization time.
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Argyriou, Andreas. "Probability of symbol error for coherent and non-coherent detection of M-ary frequency-shift keyed (MFSK) signals affected by co-channel interference and additive white Gaussian noise (AWGN) in a fading channel." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA376826.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, March 2000.<br>Thesis advisor(s): Lebaric, Jovan; Robertson, Clark. Includes bibliographical references (p. 289). Also available online.
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Williams, Steve. "Advanced Hardware-in-the-Loop Testing Assures RF Communication System Success." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/604299.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California<br>RF Communication (COMMS) systems where receivers and transmitters are in motion must be proven rigorously over an array of natural RF link perturbations such as Carrier Doppler shift, Signal Doppler shift, delay, path loss and noise. These perturbations play significant roles in COMMS systems involving satellites, aircraft, UAVs, missiles, targets and ground stations. In these applications, COMMS system devices must also be tested against increasingly sophisticated intentional and unintentional interference, which must result in negligible impact on quality of service. Field testing and use of traditional test and measurement equipment will need to be substantially augmented with physics-compliant channel emulation equipment that broadens the scope, depth and coverage of such tests, while decreasing R&D and test costs and driving in quality. This paper describes dynamic link emulation driven by advanced antenna and motion modeling, detailed propagation models and link budget methods for realistic, nominal and worst-case hardware-in-the-loop test and verification.
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Sng, Sin Hie. "Radio channel modeling for mobile ad hoc wireless networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSng.pdf.
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Thesis (M.S. in Engineering Science (Electrical Engineering))--Naval Postgraduate School, June 2004.<br>Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 71). Also available online.
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Kučera, Jan. "Modelování přenosových kanálů pro příjem digitální televize DVB-T/H." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218612.
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This thesis focuses on analysis, classification, simulation and assessment of the signal fading in the scope of terrestrial digital television reception. This is a phenomenon associated with signal multipath propagation caused by the reflection, dispersion and diffraction of electromagnetic waves in interaction with relief and artificial obstacles. Wave propagation issues in a specific landscape are not the central theme of this project. Signal transmission between the transmitter and receiver is defined by channel profile models. Attention is directed not only to static reception but also to portable and mobile reception. Simulation of this phenomenon takes place in the software environment of MATLAB. In the framework of this project program fundament was created which allows simulate the signal processing across the entire communication chain of television broadcasting, including its transmitting and receiving parts.
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Hrach, Petr. "Simulace RF přenosového kanálu pro DVB-H a DVB-SH." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219129.
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Project is focused on description DVB broadcasting for hand-held’s. It describes standard DVB-H that is founded on DVB-T and uses its transmission infrastructure. Standard DVB-SH is a hybrid system that adds to terrestrial broadcasting satellite connection. Signal can extend by various environments, therefore it are defined models transmission channel with defined parameters. Simulation of the transmission in both channel are realized in user application created in MATLAB. Finally, obtained results are evaluated and discussed.
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Axelsson, John. "Long shifts, short rests and vulnerability to shift work." Doctoral thesis, Stockholm : Department of Psychology, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-453.
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Garcia, Peña Axel Javier. "Optimization of demodulation performance of the GPS and GALILEO navigation messages." Phd thesis, Toulouse, INPT, 2010. http://oatao.univ-toulouse.fr/12022/1/garcia_pena_partie_1_sur_2.pdf.
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The demodulation performance achieved by any of the existing GPS signals, L1 C/A, L2C or L5, is satisfactory in open environments where the available C/N0 is quite high. However, in indoor/urban environments, the C/N0 level of the received signal is often very low and suffers fast variations which can further affect the GNSS messages demodulation. Therefore, since the mass-market applications being designed nowadays are aimed at these environments, it is necessary to study and to search alternative demodulation/decoding methods which improve the GNSS messages demodulation performance in these environments. Moreover, new GNSS signals recently developed, such as GPS L1C and GALILEO E1, must also be considered. These signals aim at providing satellite navigation positioning service in any kind of environment, giving special attention to indoor and urban environments. Therefore, the demodulation performances of the new GNSS signals as they are defined in the current public documents is also analysed. Moreover, new GALILEO E1 message structures are proposed and analysed in order to optimize the demodulation performance as well as the quantity of broadcasted information. Therefore, the main goal of this dissertation is to analyse and to improve the demodulation performance of the current open GNSS signals, specifically in indoor and urban environments, and to propose new navigation message structures for GALILEO E1. A detailed structure of this dissertation sections is given next. First, the subject of this thesis is introduced, original contributions are highlighted, and the outline of the report is presented. Second, this dissertation begins by a description of the current structure of the different analysed GNSS signals, paying special attention to the navigation message structure, implemented channel code and their decoding techniques. In the third section, two types of transmission channel models are presented for two different types of environments. On one hand, an AWGN channel is used to model the signal transmission in an open environments. On the other hand, the choice of a specific mobile channel, the Perez-Fontan channel model, is chosen to model the signal transmission in an urban environment. In the fourth section, a tentative to make a binary prediction of the broadcasted satellite ephemeris of the GPS L1 C/A navigation message is presented. The prediction is attempted using the GPS L1 C/A almanacs data, a long term orbital prediction program provided by TAS-F, and some signal processing methods: spectral estimation, the PRONY method, and a neural network. In the fifth section, improvements to the GPS L2C and GPS L5 navigation message demodulation performance are brought by using their channel codes in a non-traditional way. Two methods are inspected. The first method consists in sharing information between the message inner and outer channel codes in order to correct more received words. The second method consists in using the ephemeris data probabilities in order to improve the traditional Viterbi decoding. In the sixth section, the GPS L1C and GALILEO E1 Open Service demodulation performance is analysed in different environments. First, a brief study of the structure of both signals to determine the received C/N0 in an AWGN channel is presented. Second, their demodulation performance is analysed through simulations in different environments, with different receiver speeds and signal carrier phase estimation techniques.
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Ramos, Priscila de Moraes. "Análise semi-quantitativa da prova cruzada por citometria de fluxo no transplante renal : determinação de pontos de corte e impactos clínicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/186144.
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Introdução: Testes de histocompatibilidade são indispensáveis para viabilizar o transplante renal. A prova cruzada por citotoxicidade dependente de complemento (CDC) tem sido a técnica padrão para avaliar risco imunológico pré-transplante, no entanto, a prova cruzada por citometria de fluxo (FCXM) possui benefícios adicionais, como maior sensibilidade e análise semi-quantitativa através do Median Channel Shift (MCS). Objetivo: Definir pontos de corte de MCS baseado em correlação inter-técnicas e desfechos clínicos pós-transplante. Método: Estudo retrospectivo com pacientes candidatos a transplante renal no Hospital de Clínicas de Porto Alegre, entre janeiro/2016-agosto/2017. Foram avaliadas 1705 provas cruzadas e 221 pacientes submetidos ao transplante. Resultados: A FCXM, relacionada ao CDC, apresentou sensibilidade=87%(FCXM-T) e 90%(FCXM-B), e VPN=98% para ambos. FCXM-B apresentou especificidade=43%, relacionada aos casos CDC-/FCXMB+. FCXM-T e -B detectaram 53% e 76% dos casos de DSA≥5001 (Donor Specific Antibody). MCS apresentou desempenho satisfatório em detectar CDC+ (AUC/IC): MCST=0,909(0,886-0,933) e MCSB=0,775(0,724-0,826). Pontos de corte de MCST=245 e MCSB=282 apresentaram melhor predição de CDC+. Não houve diferença na função do enxerto de pacientes transplantados com FCXM+. Apenas 30% das FCXM+ estiveram diretamente relacionadas com DSA pré-tx. No entanto, episódios de rejeição foram mais frequentes no grupo FCXM+vs.FCXM- (95%vs.86%, p=0,04). Conclusão: É possível calibrar o MCS baseado no CDC+, no entanto, significa um risco em termos da não detecção de anticorpos de baixo título. A FCXM+, em curto prazo, não deve ser por si só um fator impeditivo para o transplante. A análise conjunta do MCS e DSA parece ser uma boa ferramenta de seleção dos receptores renais.<br>Introduction: Histocompatibility tests are indispensable for enable the renal transplantation. Crossmatching tests for complement dependent cytotoxicity (CDC) has been a standard technique for assess pre-transplant immunological risk, however, the flow cytometry crossmatching test (FCXM) has additional benefits, such as increased sensitivity and semi-quantitative analysis through the Median Channel Shift (MCS). Objective: Define MCS cutoff values based on inter-technical correlation and post-transplant clinical outcomes. Methods: A retrospective study with renal transplant candidates at the Hospital de Clínicas of Porto Alegre, between January/2016-August/2017. A total of 1705 crossmatching and 221 patients submitted to transplantation were evaluated. Results: The FCXM, related to CDC, resulted in sensitivity=87% (FCXM-T) and 90% (FCXM-B), and NPV=98%, for both. FCXM-B resulted in specificity=43%, related to cases CDC-/FCXMB+. FCXM-T and -B detected 53% and 76% of cases of DSA≥5001 (Donor Specific Antibody). The MCS showed satisfactory performance in detecting CDC + (AUC/IC): MCST=0.909(0.886-0.933) and MCSB=0.775(0.724-0.826). Cutoff values of MCST=245 and MCSB=282 showed better prediction of CDC+. There was no difference in the graft function of patients transplanted with FCXM+. Only 30% of FCXM + were directly related to pre-tx DSA. However, rejection episodes were more frequent in the group FCXM+vs.FCXM- (95%vs.86%, p=0,04). Conclusion: it is possible to calibrate MCS based on CDC +, however, that means a risk in terms as to the non-detection of low-titre antibodies. The FCXM+, in the short term, should not be by itself an impediment to transplantation. Joint analysis of MCS and DSA seems to be a good tool for selection of renal receptors.
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Kresta, Daniel. "Analýza přenosu mobilního digitálního rozhlasového vysílání." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-241058.
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This thesis deals with an analysis of a system called Digital Audio Broadcast and describes its mathematical model created in MATLAB program. In the first part basic blocks of a transmitter and a receiver are analyzed along with their principles. Then different types of transmission channels for static, portable and mobile receivers are described. The second part contains description of the DAB mathematical model itself. Individual blocks are described in the order of the DAB signal path, from the transmitter through the transmission channel to the receiver side. In this part the graphical user interface is also described. In the final part the results of experimental measurements and simulations are presented.
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Baserdem, Ciler. "Symbol Timing Recovery For Cpm Signals Based On Matched Filtering." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12608072/index.pdf.
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In this thesis, symbol timing recovery based on matched filtering in Gaussian Minimum Shift Keying (GMSK) with bandwidth-bit period product (BT) of 0.3 is investigated. GMSK is the standard modulation type for GSM. Although GMSK modulation is non-linear, it is approximated to Offset Quadrature Amplitude Modulation (OQAM), which is a linear modulation, so that Maximum Likelihood Sequence Estimation (MLSE) method is possible in the receiver part. In this study Typical Urban (TU) channel model developed in COST 207 is used. Two methods are developed on the construction of the matched filter. In order to obtain timing recovery for GMSK signals, these methods are investigated. The fractional time delays are acquired by using interpolation and an iterative maximum search process. The performance of the proposed symbol timing recovery (STR) scheme is assessed by using computer simulations. It is observed that the STR tracks the variations of the frequency selective multipath fading channels almost the same as the Mazo criterion.
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Polák, Ladislav. "Simulace vícecestného šíření vícestavových modulací." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218043.
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The diploma thesis Simulation of Multipath Propagation of Multistate Modulations is focused on the development of an appropriate algorithm in MATLAB environment, which is capable to simulate the impact of the multipath propagation on received signal (error rate) on the basis of given parameters of the transmission channels. Mechanisms and characteristics of the wave propagation in communication environment, types of digital modulations and their most important parameters are described in the first part of this thesis. The second part is focused on the simulation itself. Created GUI (Graphical User Interface) is able to display constellation diagrams of transmitted and received signals, as well as their bit error rate. It is also possible to compare these data with the data of signal, which is passed by a non-fading channel.
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Papantoniou, Kyriaki 1983. "Cancer risk and hormonal changes in night shift workers." Doctoral thesis, Universitat Pompeu Fabra, 2014. http://hdl.handle.net/10803/346932.
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Recent human and animal data indicate that night shift work might increase the risk for cancer. Epidemiologic evidence is limited and has mostly focused on breast cancer while underlying mechanisms are still poorly understood. The main aim of this thesis was to evaluate the association between night shift work and breast and prostate cancer risk in a population based multi-case-control study in Spain and study possible underlying mechanisms including the disruption of the daily production of melatonin and sex hormones. Having ever worked permanent or rotating night shift were associated with an increased but not statistically significant risk for breast cancer compared to day workers; Risk increased with duration of exposure and was higher among evening chronotypes. Risk was higher for tumors with worse prognosis. Night shift workers had significantly lower 6-sulfatoxymelatonin levels and higher androgens and progestagens, while smaller differences were found for estrogens. Lower melatonin and higher sex hormone levels among night shift workers are two possible mechanisms that might explain the increased risk of hormone-related tumors.<br>Evidencia reciente en humanos y animales indica que el trabajo nocturno puede aumentar el riesgo de cáncer. La evidencia epidemiológica está limitada y sobre todo se ha enfocado en el cáncer de mama, mientras los mecanismos que se involucran no se han estudiado lo suficiente. El objetivo principal de esta tesis era de evaluar la asociación entre el trabajo nocturno y el cáncer de mama y próstata en un estudio poblacional de casos y controles en España y estudiar posibles mecanismos como la disrupción de la producción de la melatonina y las hormonas sexuales. Haber trabajado de noche de modo permanente o rotativo estaba asociado con un mayor riesgo de padecer cáncer de mama y próstata, sin embargo las diferencias no eran estadísticamente significativas. El riesgo era mayor para trabajadores de noche con exposiciones más largas y para los que tenían un cronotipo vespertino. Se observo un mayor incremento de riesgo de cáncer para los tumores con peor pronóstico. Los trabajadores de noche tenían los niveles de melatonina más bajos y los andrógenos y progestágenos más altos que los trabajadores de día. La supresión de la melatonina y el incremento de las hormonas sexuales son dos mecanismos que pueden explicar en parte el incremento del riesgo de tumores hormono-dependientes
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Foldal, Vegard Stolsmo. "Personal Dispositions and Shift Work Tolerance. A Longitudinal Study of Shift Workers in Trondheim Municipality." Thesis, Norges teknisk-naturvitenskapelige universitet, Psykologisk institutt, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26637.
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The aim of the present study was to investigate how dispositional resistance to change (RTC) and neuroticism could predict shift work tolerance (SWT) over a period of six months. Electronic questionnaire were completed by 74 shift workers employed in Trondheim municipality in January 2013 (T1) and in June 2013 (T2). The results showed that age, gender, neuroticism, and RTC were related to SWT. Age at T1 predicted better SWT at T2, while male gender predicted worse SWT at T2. RTC at T1 predicted better SWT at T2, while neuroticism at T1 predicted worse SWT at T2. The findings suggest that individual differences, especially neuroticism, can predict SWT over a period of six months.
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Kadir, Mohammad Ismat. "Co-located and distributed multicarrier space-time shift keying for wideband channels." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/363263/.
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Multicarrier (MC) transmissions are proposed for the space time shift keying (STSK) concept. Specifically, OFDM, MC CDMA and OFDMA/SC-FDMA-aided STSK are proposed for transmissions over dispersive wireless channels. Additionally, a successive relaying (SR) aided cooperative MC STSK scheme is conceived for gleaning cooperative space time diversity and for mitigating the half-duplex throughput loss of conventional relaying. Furthermore, a multiple-symbol differential sphere decoding (MSDSD) aided multicarrier STSK arrangement is proposed to dispense with channel estimation (CE). We design a novel modality of realizing STSK amalgamated with OFDM for facilitating high-rate data-transmissions through a number of low-rate parallel subchannels, thus overcoming the dispersion induced by broadband channels. A MC-CDMA aided STSK system is also proposed for mitigating the channel-induced dispersion, while providing additional frequency-domain (FD) diversity and supporting multiuser transmissions. As a further advance, we design OFDMA and SC FDMA-aided STSK systems, which are capable of communicating in dispersive multiuser scenarios, whilst maintaining a low peak-to-average power ratio (PAPR) in the SC-FDMA-aided STSK uplink. Additionally, complexity reduction techniques are proposed for OFDMA/SC-FDMA-aided STSK. We also conceive the concept of SR aided cooperative multicarrier STSK for frequency-selective channels for mitigating the typical 50% throughput loss of conventional half-duplex relaying in the context of MC-CDMA and for reducing the SR-induced interferences. We additionally propose a differentially encoded cooperative MC-CDMA STSK scheme for facilitating communications over hostile dispersive channels without requiring CE. Finally, the noncoherent multicarrier STSK arrangement is further developed by using MSDSD. The conventional differential detection suffers from a typical 3-dB performance loss, which is further aggravated in the presence of high Doppler frequencies. Hence, for the sake of mitigating this performance loss in the face of high Doppler scenarios, while maintaining a modest decoding complexity, both a hard-decision-based as well as an iterative soft-decision multiple-symbol differential sphere decoding aided multicarrier STSK arrangement is developed.
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De, Girolamo Debbie. "The fugitive identity of mediation : negotiations, shift changes and allusionary action." Thesis, London School of Economics and Political Science (University of London), 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.566267.
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Despite much having been written about what mediation is, direct observations of commercial mediations are limited. This doctoral thesis provides an opportunity to observe mediation in action and to provide external commentary about the actions observed. Mediation is approached ethnographically as a social process that is informed by structures, rules and norms that colour the environment within which it operates. As Malinowski observed, one had to live among a society one was studying in order to really learn about the society. Ethnography permits us to see beyond the act. to understand how and why people behave as they do, and to make clear that which is obscure. Through the ethnographic method, a process leading to negotiated order is examined, baring its elements, identifying its influences and studying the movement to order. The result is the reconceptualization of mediation. Mediation is a process inextricably linked to negotiation, providing a contextual layer to bi-lateral negotiation while retaining the processual shape of negotiation. The mediator is invited into the negotiation as third party intervener. He creates the process of mediation, defining the process by his actions, which ultimately merges mediator with process. The mediator becomes part of the negotiation process, at times separate from the parties, aligned with the parties or in opposition to the parties. She takes on their identity in addition to her own. The mediator is mediator; she is party; she is party adviser. She takes on the mantle of these personas during mediation: the mediation becomes her negotiation; the party becomes her client. For the parties, however, the mediator remains the non-aligned third party intervener suggested by the literature. The negotiation remains their negotiation and the mediation remains a process ancillary to their negotiation, views aided in their formulation bv mediators' statements regarding mediator role and mediation process.
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Turnock, Karen Ann. ""It's a shift in thinking, a shift in practice" : moving to a new assessment framework in early childhood education." Thesis, University of Canterbury. School of Maori, Social and Cultural Studies, 2009. http://hdl.handle.net/10092/3077.
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This qualitative ethnographic study explored the various ways a team of early childhood teachers made sense of, and used, an assessment framework based on learning dispositions and formative assessment for assessing children’s learning. In the late 1980s and early 1990s traditional methods for assessing children were being significantly questioned. The development in 1996 of Te Whāriki, the early childhood curriculum, signalled a re-form of assessment practices in the early years. This reform involved a major shift in thinking and practice for teachers who worked in early childhood education. The teachers in this study were already beginning to change their assessment practices to reflect learning dispositions and formative assessment. This study focused on the theoretical and policy framework that reflected the shift toward teachers being encouraged to adopt these new ways for assessing children’s learning
Multiple sources of data collection included individual interviews, a group interview, an analysis of documents including relevant policies, staff meeting minutes and Learning Stories written by three of the teachers over a six-month period. Findings revealed that the ways in which the teachers in this study made sense of, and used, the dispositional framework depended on how they viewed the purposes of assessment and their role as teachers. The study also explored some of the consequences of teachers adopting the dispositional framework when they were already experienced in other forms of assessment practice. The significance of self-directed professional development was also highlighted. Implications for management include the need to consider that the theoretical concepts associated with shifting from a developmental approach to a dispositional focus requires extensive time, resources and a team that is committed to change.
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Kallel, Fathi. "Algorithmes de réduction du bruit en vue d'une amélioration de l'intelligibilité de la parole : cas de la prothèse cochléaire." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10293.
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La prothèse cochléaire est un appareillage destiné à la réhabilitation des surdités profondes et totales dont un appareillage conventionnel est inefficace. Elle assure la stimulation directe des neurones cochléaires à travers un faisceau d’électrodes. Différents travaux de recherches ont été établis afin d'évaluer l'intelligibilité de la parole chez les sujets bilatéralement implantés en environnements silencieux et bruité. Les résultats ont montré une bonne intelligibilité de la parole en milieu silencieux. Toutefois, les capacités de perception de la parole chez les patients implantés se dégradent en environnement bruité. Nous avons de ce fait proposé trois approches de traitement du signal en vue d'une amélioration de l'intelligibilité de la parole dans le cas de l'implant cochléaire bilatéral: la stimulation bilatérale décalée, l'algorithme de la soustraction spectrale bi-voie et l'algorithme de la soustraction interspectrale. Des améliorations de l'intelligibilité de la parole entre 4% et 10% ont été notées dans le cas de la stimulation bilatérale décalée par rapport à la stimulation bilatérale symétrique. L'approche basée sur l'algorithme de la soustraction spectrale bi-voie présentait des améliorations variables entre 10% et 17%. De meilleures performances ont été obtenues lorsque l'approche basée sur l'algorithme de la soustraction interspectrale est considérée où les améliorations étaient entre 15% et 27%<br>Cochlear prostheses are intended for persons suffering from deep or total deafness where conventional prostheses proved ineffective. In quiet listening conditions, most bilateral cochlear implant (BCI) users can now achieve even more than 80% word recognition scores regardless the used device. However, under more challenging listening conditions, BCI recipients perform poorly, compared to normal-hearing listeners. In this work, we proposed three speech processing approaches for speech intelligibility improvement. The first is based on shifted bilateral cochlear implant stimulation; the second is based on dual-channel spectral subtraction algorithm and finally the cross power spectral subtraction algorithm was considered. Experimental results showed a speech intelligibility improvement between 4% and 10% when the shifted bilateral cochlear implant stimulation is considered. Performance amelioration was observed when the dual-channel spectral subtraction based speech enhancement algorithm was considered and the improvement was between 10% and 17%. The better performance was obtained when noisy speech signals were processed using cross power spectral subtraction algorithm and the improvement was between 15% and 27%
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Cioffi, Marina. "Structure determination of protein-ligand complexes using 1H-NMR chemical shift changes." Thesis, University of Sheffield, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489716.
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Chapter 1 reviews the experimental and computational techniques available for the structure determination of protein-ligand complexes at atomic resolution. Chapter 2 describes a new method for determining three-dimensional solution structures of protein-ligand complexes using experimentally determined complexation-induced changes in ¹H NMR chemical shift (CIS). The method has been tested using the complex formed by the protein Neocarzinostatin and four synthetic chromophore analogues. The experimental CIS values were used in a continuous direct structure refinement process based on genetic algorithms to sample conformational space. The calculated structure agrees well with the NMR solution structure of the complex indicating the potential of this approach for structure determination. Chapter 3 reports an analysis of the effects of protein flexibility on the accuracy of 3D structures determined using the CIS-based approach. The effects of protein conformational mobility have been investigated. The results indicated that loop movement has a significant impact on the quality of the structure generated by the CIS structure determination methodology. Chapter 4 introduces a first attempt to validate the CIS-based approach on a set of complexes containing ligands, with a range of anisotropic functional groups, molecular size and flexibility. For all the cases analyzed, it was possible to identify the protein binding site and in some cases the orientation of the ligand in the binding site was also accurately predicted. Chapter 5 reports binding studies for the complexes of the protein Barnase with ligand 3-GMP, d(GpC) and d(CGAC). The mononucleotide did not show any binding even when changing pH conditions. However, binding was observed for the dinucleotide and tetranucleotide. NMR titration experiments supported by structure determination experiments show that in both cases the ligand binds in the G-recognition binding site, in contrast with previously published X-ray experiments, where d(GpC) tends to occupy secondary subsite as a result of crystal packing.
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Rivas, Ubach Albert. "Stoichiometric and metabolomic shifts of organisms under environmental changes." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129546.
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L’estequiometria ecològica pretén explicar l’estil de vida dels organismes i l’estructura i funció dels ecosistemes en relació a les proporcions de C:N:P dels organismes i ecosistemes. Un dels paradigmes centrals de l’estequiometria ecològica és la “growth rate hypothesis” (GRH) que proposa que els organismes en fase de creixement han d’incrementar l’aportació de P al RNA per suplir l’elevada demanda de síntesi proteica necessària pel creixement. Baixes proporcions ambientals de N:P i en condicions no limitants, afavoreix les espècies amb creixements més ràpids, això podria llavors induir canvis a les comunitats. Recentment, les evidències d’aquestes relacions entre el medi abiòtic i les proporcions de C:N:P als organismes confereix a l’estequiometria ecològica un rol central a la recerca ecològica.
La majora d’elements, especialment el C, N i P, els més estudiats en l’estequiometria ecològica, no actuen per ells mateixos sinó que formen part de compostos moleculars. L’acoblament de la metabolòmica a l’estequiometria ajuda a entendre la resposta dels organismes sota estressos biòtics i abiòtics així com també els processos ontogènics i fisiològics, i permet entendre l’assignació dels diferents nutrients a les diferents funcions fisiològiques. La metabolòmica permet l’anàlisi del metaboloma, el conjunt de metabòlits d’un organisme en un moment específic, i ha demostrat una alta sensibilitat en detectar els mecanismes fenotípics i les molècules clau que intervenen en les respostes dels organismes davant de canvis ambientals. Aquest mètode permet una bona exploració i examinació de la bioquímica de les mostres.
En aquesta tesis hem realitzat una revisió de l’estat de l’art de l’estequiometria ecològica i la metabolòmica aplicada al camp de l’ecologia i fisiologia. Després, vam optimitzar un protocol de metabolòmica utilitzant RMN per posteriorment analitzar la metabolòmica i estequiometria en diferents espècies vegetals sota condicions experimentals de canvi climàtic i també de cianobacteris creixent sota condicions limitants de nutrients.
Els nostres experiments han demostrat que les diferents condicions ambientals de les diferents estacions de l’any del clima mediterrani fan canviar el metaboloma de les plantes. Aquests canvis van també estar acompanyats per canvis estequiomètrics demostrant així la relació entre els canvis foliars de les proporcions de C:N:P:K amb els canvis metabolòmics. Per exemple, el bruc d’hivern va presentar concentracions majors de metabòlits relacionats amb el creixement com els sucres o els aminoacids durant la primavera, l’estació de creixement. Aquests increments en les concentracions d’aquests compostos van ser també acompanyats per proporcions foliars de N:P més baixes, tal i com tracta d’explicar la GRH. De totes maneres, la GRH no sembla complir-se del tot en grans arbres que presenten estructures de fusta que actuen de reservori de nutrients com en el cas de l’alzina.
Les plantes Mediterrànies sota condicions de sequera, ja sigui experimental com condicions naturals a l’estiu, presenten alts nivells de compostos fenòlics amb acció antioxidant o osmorreguladors com els sucres o la colina. Aquests canvis, un cop més, van estar acompanyats per concentracions foliars de K més elevades per així evitar pèrdues d’aigua. També, la sequera sembla estimular l’activitat d’herbivorisme mitjançant el canvi metabolòmic de les plantes incrementant les concentracions de sucres i antioxidants. Això podria llavors tenir un impacte indirecte a les xarxes tròfiques.
Els cianobacteris canvien el metabolisme sota condicions limitants de P i ferro (Fe). Les cèl·lules van canviar el metabolisme augmentant les vies anaeròbiques incrementant així les concentracions d’àcid làctic, entre altres canvis metabolòmics. El metabolisme anaeròbic produeix menys energia i redueix el creixement, això pot produir llavors canvis a la composició de les especies dels ecosistemes aquàtics i actuar en el control de la fixació del CO2 atmosfèric.
Aquesta tesi ha ajudat a fer els primers passos de l’aplicació de la metabolòmica i l’estequiometria per a una major comprensió de les respostes dels organismes i els ecosistemes davant dels canvis ambientals. Els resultats el estudis realitzats mereixen i obren noves propostes per estudis futurs en la recerca ecometabolòmica.<br>Ecological stoichiometry aims to explain the organism life style and the ecosystem structure and function in relation to the environment and organism C:N:P ratios. One of the central paradigms of ecological stoichiometry is the growth rate hypothesis (GRH) proposing that growing organisms must increase their allocation of P to RNA to meet the elevated demands for the synthesis of proteins required for growth. Low ratios of environmental N:P under not limiting conditions favor species with very high rates of growth, which may induce shifts in species communities. Recently, the evidences of those relationships between the non-biotic media and organismic C:N:P ratios conferred to ecological stoichiometry a central role in ecological research.
Most elements, especially C, N and P, the most studied elements in ecological stoichiometry, do not actuate as themselves but as molecular compounds. The coupling of metabolomics to stoichiometry studies help to understand the response of organisms under biotic and non-biotic stresses, and the ontogenetic and physiological processes, and to disentangle the allocation of different nutrients to the different physiological functions. Metabolomics aims to analyze the metabolome, the total set of metabolites of an organism in a specific moment and has demonstrated a great sensitivity in detecting the phenotypic mechanisms and key molecules underlying organism responses to environmental changes. This “holistic” method enables unbiased exploration and examination of sample molecular biochemistry.
In this thesis we reviewed the state of the art of ecological stoichiometry and metabolomics applied to the field of ecology and physiology. After that, we optimized a NMR-based method for metabolomic analyses and conducted metabolomics and stoichiometric analyses in different wild plant species living in field plots under different climatic conditions and cyanobacteria growing under different nutrient deprivation.
Our experiments showed that the different environmental conditions of the different seasons of the year in Mediterranean climate make plants to shift their metabolomes. These metabolomic shifts were also accompanied by stoichiometric changes demonstrating the relationship between the shifts of foliar C:N:P:K and the shifts of metabolomes. For example, Erica multiflora shrub presented higher foliar concentrations of metabolites related to growth such as sugars and amino acids in spring, the growing season. These increments in the concentrations of these compounds were accompanied by lower foliar N:P ratios as expected in the frame of the GRH. However the GRH does not seem to be totally fulfilled in big trees that present large wood structures that act as a reservoir of nutrients as in the case of Quercus ilex.
Mediterranean plants under drought conditions (experimental or the natural drought conditions in summer) presented high levels of phenolic compounds with antioxidant function and osmoregulants such as sugars or choline. These shifts were also accompanied by higher levels of foliar K to prevent water losses. Drought seems also to stimulate the folivory activity by shifting the foliar metabolomes of plants by increasing foliar sugars and antioxidant concentrations. It could have thus a further indirect impact on trophic webs.
Cyanobacetria changed their metabolism under P and iron (Fe) deprivation. Cells shifted from aerobic to anaerobic metabolism by increasing the cellular lactic acid concentrations among other metabolomic changes. The anaerobic metabolism produces less energy and reduces cell growth. This growth reduction may produce a further shift in species composition and biodiversity of communities in aquatic ecosystems and of controls of ecosystem production and CO2 sequestration.
This thesis has thus helped to make the first steps in application of metabolomics and stocichiometry to better understand the responses of organisms and ecosystems to environmental changes. The results of the conducted studies warrant and open challenging prospects to further research in ecometabolomics.
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Yoon, Hyejin. "The Animation Industry: Technological Changes, Production Challenge, and Glogal Shifts." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1212779559.
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Ye, Zhengqing. "Changes in the El Niño-Southern Oscillation under climate regime shift and increased greenhouse gases." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31187.
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The observed El Niño/Southern Oscillation (ENSO) has shown eastward displacements of the zonal wind stress anomalies and surface heat flux anomalies in the equatorial Pacific during El Niño episodes in the 1981-1995 regime relative to the 1961-1975 regime. Numerical experiments with a modified Zebiak-Cane intermediate complexity coupled model generally reproduced such displacements when the model climatological fields were replaced by the observed and simulated climatologies for the 1981-1995 regime. The later regime climatology resulted in eastward shifts in the ENSO system during El Niño but not La Niña, through the eastward shift of the atmosphere convergence heating rate in the coupled model. The ENSO period and ENSO predictability were also enhanced in the coupled model under the later regime climatology. A similar behavior was found in the Lorenz (1963) 3-component chaos system, i.e. in both the ENSO and Lorenz systems, stronger nonlinearity appears to lengthen the period thereby enhancing the predictability. Using nonlinear principal component analysis, we demonstrated that the leading ENSO mode had changed on a physical basis since the late 1970s. The ENSO modes resembled the destabilized 'ocean basin mode' and 'the recharge-mode' in the pre- and post-1980s regimes, respectively. The surface zonal current acted as an intensifier of ENSO in the earlier regime and played a role in the transition of the ENSO cycle in the later regime. With data from an ensemble of coupled general circulation models in the IPCC-AR4 project, climate under year 2000 greenhouse gas (GHG) level was compared with climate under pre-industrial conditions. In the tropical Pacific, the warming in the mean sea surface temperatures (SST) was found to have an El Niño-like pattern, in agreement with the observed SST data (1900-1999). The models showed that both the equatorial zonal overturning circulation and the shallow meridional overturning circulation weakened under increased GHG forcing. For ENSO, the asymmetry in the SST anomalies between El Niño and La Niña was found to be enhanced under increased GHG, for both the ensemble model data and the observed data. The enhanced asymmetry was mainly caused by the intensified vertical nonlinear dynamic heating. Furthermore, the enhanced GHG simulations showed that the asymmetry between El Niño and La Niña increased in the zonal wind stress anomalies, the equatorial undercurrent anomalies and the shallow meridional overturning circulation anomalies.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate
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LeMaster, Cheryl Faye. "Leading Change in Complex Systems: A Paradigm Shift." Antioch University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=antioch1500033972019138.
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Galib, M. M. Asadullah, Takaya Yamazato, Masaaki Katayama та Akira Ogawa. "Performance Evaluation of DS/CDMA Communications Systems Modulated with π/2-shift BPSK over Multipath Rayleigh Fading Channels". IEEE, 1998. http://hdl.handle.net/2237/7788.
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Zhu, Changle. "Performance analysis of subcarrier quadrature phase-shift keying systems with I/Q imbalance over Gamma-Gamma fading channels." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58363.
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The error rate performance is studied for subcarrier intensity modulated (SIM) quadrature phase-shift keying (QPSK) system with in-phase and quadrature (I/Q) imbalance over Gamma-Gamma fading channels. In free-space optical (FSO) communication system, the transmitted signals are typically affected by the atmospheric turbulence over the transmission links. In order to study the system performance analytically, different statistical distributions have been proposed to describe the random variation in signal irradiance due to the scintillation caused by the inhomogeneities in both temperature and pressure along the transmission path. Besides the atmospheric turbulence, other sources can also introduce performance degradation to an FSO system. Using quadrature conversion, the performance of the practical system is affected by the phase and amplitude offsets in the two branches. This phenomenon is referred to as I/Q imbalance. Using direct-conversion transceivers, the I/Q imbalance is unavoidable due to the considerable mismatches between the circuit components. This imbalance can happen at transmitter end, receiver end, or both ends of the transceiver.
First, we study the error rate performance for a SIM QPSK system with transmitter I/Q imbalance over the Gamma-Gamma fading channels. Then, the error rate performance of a SIM QPSK system with receiver I/Q imbalance is investigated. Finally, the error rate performance is analyzed for a SIM QPSK system with I/Q imbalance at both ends of the transceiver over the Gamma-Gamma fading channels. Closed-form symbol error rate (SER) expressions are derived by taking into account of both the I/Q imbalance and the fading. It is discovered that the value of the receiver amplitude imbalance is irrelevant to the SER of a subcarrier QPSK system. Truncation error analyses are carried out to ensure the accuracy of the approximate series solutions and support the asymptotic analyses. We also present the numerical results to show the performance improvement using a calibrated transceiver. We will treat these three cases separately since they have slightly different models.<br>Applied Science, Faculty of<br>Engineering, School of (Okanagan)<br>Graduate
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Milligan, Lindsay. "The role of Gaelic (learners) education in reversing language shift for Gaelic in Scotland." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158424.
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Extensive literature has argued the important role that education plays in the process of language shift. Within this literature, it is widely acknowledged that education in which the target language is also the medium of instruction can make a positive contribution toward Reversing Language Shift. For users of minoritised languages in particular, having access to education in one’s own language has important status and educational consequences: helping to support the prestige of the target language and also reducing the kinds of educational inequalities that are often associated with minoritised languages. In keeping with the prime importance of language-as-medium education to language planning goals, there is a growing body of research which focuses upon Gaelic Medium Education in Scotland. The role that second or additional language education can play in Reversing Language Shift is acknowledged to a much lesser extent. This is especially true within the context of Scotland, where the relevant education provision within state secondary schools, Gaelic (Learners) Education, has only received passing recognition. This thesis aimed to address this gap in knowledge about the way in which education contributes to development goals for Gaelic in Scotland by questioning what, if any, role the Gaelic (Learners) Education programme has to play in the reversal of language shift. The first aim of the dissertation was to identify a theoretical foundation for the role that second or additional language education can play in Reversing Language Shift. Several prominent theoretical approaches were reviewed and a hypothesis posed that Gaelic (Learners) Education was beneficial to both Acquisition and Status development. Subsequent analyses of policies at the macro, meso, and micro levels confirmed the relevance of this hypothesis. However, it was also found that there was a lack of overt policy acknowledgement for Gaelic (Learners) Education in Scotland overall, suggesting that the stream was not regarded as being particularly relevant to Reversing Language Shift. The next aim of the thesis was to clarify the ways in which the stream could be used to help contribute to the reversal of language shift. This focused on identifying areas in which this educational programme could be improved. Using data elicited in semi-structured interviews with education professionals and gathered through surveys of pupils within GLE classes, several blockages for Gaelic (Learners) Education could be identified including aspects of capacity, opportunity and attitudes.
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Ghasemi, Mandana. "COMPARISON OF MULTIVARIATE PROCESS MEAN SHIFT APPROACHES: MEWMA, MCUSUM, CHANGE POINT AND NEURAL NETWORK." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1589.
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Computer integrated manufacturing environments and competition among companies to meet customer requirements raise the need for the use of online methodologies in combination with traditional Statistical Process Control tools. This study focuses on detecting the change point, when a shift in mean occurs, in a normal bivariate process using two different approaches. First, Multivariate Cumulative Sum (MCUSUM) and Multivariate Exponentially Weighted Moving Average (MEWMA) statistical procedures were used in detecting the mean shift in the process. Then the step-change detection and neural network approaches were applied to the outputs of MCUSUM and MEWMA statistical procedures to identify the time of the change. The results show that the step-change and neural network approaches are capable of detecting the time of the change earlier than either the MCUSUM or MEWMA statistical procedure.
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Langmaid, Kimberly Ford. "Seeing Shifts: Ecologists' Lived Experiences of Climate Change in Mountains of the American West." [Yellow Springs, Ohio] : Antioch University, 2009. http://etd.ohiolink.edu/view.cgi?acc_num=antioch1244125357.
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Thesis (Ph. D.)--Antioch University New England, 2009.<br>Title from PDF t.p. (viewed Aug. 7, 2009). "A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Environmental Studies at Antioch University New England (2009)."--The title page. Advisor: Mitchell Thomashow, Ph. D. Includes bibliographical references (p. 184-196).
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Liu, Wenjie. "Estimation and bias correction of the magnitude of an abrupt level shift." Thesis, Linköpings universitet, Statistik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84618.
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Consider a time series model which is stationary apart from a single shift in mean. If the time of a level shift is known, the least squares estimator of the magnitude of this level shift is a minimum variance unbiased estimator. If the time is unknown, however, this estimator is biased. Here, we first carry out extensive simulation studies to determine the relationship between the bias and three parameters of our time series model: the true magnitude of the level shift, the true time point and the autocorrelation of adjacent observations. Thereafter, we use two generalized additive models to generalize the simulation results. Finally, we examine to what extent the bias can be reduced by multiplying the least squares estimator with a shrinkage factor. Our results showed that the bias of the estimated magnitude of the level shift can be reduced when the level shift does not occur close to the beginning or end of the time series. However, it was not possible to simultaneously reduce the bias for all possible time points and magnitudes of the level shift.