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Advances in image modeling and data communicationsXiao, Shengkuan. January 2007 (has links)
Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Charles G. Boncelet, Dept. of Computer & Information Sciences. Includes bibliographical references.
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Selected applications of sequential injection analysisMoalusi, Matlhodi Salamina. January 2006 (has links)
Thesis (M.Sc.)(Chemistry)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.
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Autism and our community: Feedback from early intervention providersKallal, Anna Denise 01 May 2016 (has links)
AN ABSTRACT OF THE THESIS OF Anna Kallal, for the Masters of Science degree in Communication Disorders and Sciences presented on March 28, 2016, at Southern Illinois University Carbondale. TITLE: AUTISM AND OUR COMMUNITY: FEEDBACK FROM EARLY INTERVENTION PROVIDERS MAJOR PROFESSOR: Dr. Valerie Boyer Early Intervention (EI) providers often work closely with children who are diagnosed with autism spectrum disorder (ASD) or children who have signs and symptoms of ASD. An understanding of the characteristics in children at early ages can lead to an earlier diagnosis of ASD. The current study investigated specific characteristics that EI providers identify prior to making a referral for an ASD evaluation as well as what treatment strategies EI providers report utilizing when working with children who have ASD. Information was gathered for this study by use of a survey. The survey contained two vignettes of children with varying degrees of ASD characteristics. Speech-Language Pathologists (SLP) who work as EI providers responded to a survey. Results showed that respondents were more willing to make referrals for ASD evaluations when a child displayed more severe characteristics. Respondents listed treatment strategies they were likely to employ with children who display similar characteristics of the children in the vignettes. The researcher identified from survey responses that EI providers are more likely to identify social communication characteristics when describing features critical to referral. This study identifies the characteristics important to making earlier referrals for ASD evaluations, as well as what treatment strategies work best when working with children with ASD.
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Performance analysis of diversity combining for frequency-hop communications under partial-band and multitone interferenceLi, Gang 04 July 2018 (has links)
This dissertation is concerned with performance analysis of diversity combining
schemes in frequency-hop spread spectrum communications under the worst case partial-band noise and multitone jamming.
Performance of a ratio-threshold diversity combining scheme in fast frequency
hop spread spectrum systems with M-ary frequency shift keying modulation
(FFH/MFSK ) under partial-band noise (PBN) and band multitone jamming without
and with the additive white Gaussian noise (AWGN) is analyzed. The analysis
is based on exact bit error probabilities, instead of bounds on the bit error probabilities.
A method to compute the bit error probability for ratio-threshold combining
on jamming channel is developed. Relationship between the system performance
and the system parameters, such as ratio-threshold, diversity order, and thermal
noise level, is illustrated. The performances under band multitone jamming and
under partial-band noise jamming are compared. For binary FSK modulation, the
performance under the two types of jamming is almost the same, but for 8-ary
FSK modulation, tone jamming is more effective against communications. The
structure of the combiner is very simple and easy to implement. Another merit of
this combiner is that its output can be directly fed to a soft-decision FEC decoder.
Maximum-likelihood diversity combining for an FFH/MFSK spread spectrum
system on a PBN interference channel is investigated. The structure of maximum
likelihood diversity reception on a PBN channel with AWGN is derived. It is
shown that signal-to-noise ratio and the noise variance at each hop have to be
known to implement this optimum diversity combining. Several sub-optimum diversity
combining schemes, which require the information on noise variance of each
hop to operate, are also considered. The performance of the maximum-likelihood
combining can be used as a standard in judging the performance of other suboptimum, but more practical diversity combining schemes. The performance of
the optimum combining scheme is evaluated by simulations. It is shown that the
Adaptive Gain Control (AGC) diversity combining actually achieves the optimum
performance when interference is not very weak. But the performance difference
between some of the known diversity combining schemes, which do not require
channel information to operate, and the optimum scheme is not small when the
diversity order is low.
An error-correction scheme is proposed for an M-ary symmetric channel characterized
by a large error probability Pe. Performance of the scheme is analyzed.
The value of Pe can be close to, but smaller than, 1 – 1/M for which the channel
capacity is zero. Such a large Pe may occur, for example, in a jamming environment. The coding scheme considered consists of an outer convolutional code
and an inner repetition code of length m which is used for each convolutional
code symbol. At the receiving end, the m inner code symbols are used to form
a soft-decision metric, which is subsequently passed to a soft-decision decoder for
the convolutional code. Emphasis is placed on using a binary convolutional code
due to the consideration that there exist commercial codecs for such a code. New
methods to generate binary metrics from M-ary (M > 2) inner code symbols
are developed. For the binary symmetric channel, it is shown that the overall
code rate is larger than O.6R0, where R0 is the cutoff rate of the channel. New
union bounds on the bit error probability for systems with a binary convolutional
code on 4-ary and 8-ary orthogonal channels are presented. Owing to the variable
m which has no effect on the decoding procedure, this scheme has a clear operational
advantage over some other schemes. For a BSC and a large m, a method
presented for BER approximation based on the central limit theorem. / Graduate
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Relative population densities and transition probabilities in a neon glow dischargeIrwin, John Charles January 1965 (has links)
An experimental technique has been developed for the investigation of departures from thermodynamic equilibrium in plasmas. The relative populations of the upper and lower levels of a spectral line are measured by the reversal temperature method. The reversal temperatures themselves are determined by varying the relative exposure times of the background source and the plasma to be investigated. The relative population densities of the levels in the 2p⁵3s and 2p⁵3p configurations of Nel have been measured. A Neon glow discharge operated in the current region 1mA to 100mA served as the plasma. The results show that the excited gas is definitely not in thermal equilibrium.
The relative intensities of the emission lines between the 2p⁵3s and 2p⁵3p configurations of NeI were measured photometrically and corrected for self-absorption. These intensities were then used in conjunction with the relative population densities to determine relative transition probabilities for the spectral lines concerned. The results are accurate to approximately 10% to 15% and are compared to the values obtained previously by other workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
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Spectroscopic studies of shock tube plasmasJames, Harry Gordon January 1965 (has links)
Spectroscopic measurements were made on plasmas in electromagnetic shock tubes to test the state of equilibrium in these plasmas. In an Argon-Oxygen mixture the relative intensities of AII and AIII lines and of OII lines indicated that complete equilibrium was not established. In a Helium plasma the observed line intensities showed that the populations of the Hel levels agreed with a Boltzmann equilibrium distribution. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
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Colour centres in alkali metal azidesPringle, John Peter Scott January 1958 (has links)
Previous work by Heal had shown that X-irradiated sodium azide crystals dissolved in water produced small amounts of nitrogen gas, hydroxyl ion and ammonia, thereby indicating that some decomposition had occurred. Heal also observed colours in the material, similar to those of the X-irradiated alkali halides for which a whole series of colour centres responsible have been postulated. It was therefore decided to investigate the colour centres of the alkali azides, partly to extend the colour centre research, and partly to illuminate the X-ray decomposition processes.
Crystalline plates of NaN₃, KN₃, RbN₃ and CsN₃ were irradiated at liquid nitrogen and room temperature, using a Machlett AEG-50 tungsten target X-ray tube, operated at 50 KVP. The absorption spectra of the irradiated samples were measured at liquid nitrogen temperature with a Cary model 14 recording spectrophotometer.
The low temperature spectra consisted of three bands.
The A band, peaking at 612, 568, 578 and 592 mu for NaN₃, KN₃, RbN₃ and CsN₃, respectively, is ascribed to F centres. The anomalous sodium azide band is related to its trigonal crystal structure, differing from the body centred tetragonal of the other azides.
The B band, peaking at 361, 374 and 390 mu for KN₃, RbN₃ and CsN₃ respectively, was strong and triple, there being shoulders about 30 mu on each side of the main peak. For NaN₃ it was weak, single and peaked near 330 mu. Tentatively, it is ascribed to the centre.
The C band, peaking about 740, 790, 820 and 850 mu for NaN₃, KN₃, RbN₃ and CsN₃ is weak and single. It may be due to F1 centres.
The room temperature spectra were strikingly different from each other, except for RbN₃ and CsN₃.
For NaN₃ five bands were observed at 342, 560, 630 , 730 and 860 mu; the latter four were weak and may be an electronic vibrational spectrum. The strong 342 mu band is ascribed to the presence of sodium metal in some non-colloidal form; a correlation between the band and the ionisation potential of the metal is noted.
In KN₃ three bands at 760 (strong), 590 (strong shoulder) and 340 mu (weak) were obtained. The first two are ascribed to small F centre aggregates of the M,R type though no definite assignations are made.
RbN₃ and CsN₃ spectra both consist of a broad peak showing fine structure, the highest peaks occurring at 330 mu and 375 mu respectively. It is considered uncertain that all the absorption is due to the impurity held responsible for the fine structure. / Science, Faculty of / Chemistry, Department of / Graduate
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The relative intensities of the polarized components of the symmetric Raman line of calciteFriedmann, Gerhart Bruno January 1957 (has links)
The theory of the Raman Effect in crystals has been re-examined by O. Theimer (Can. J. Phys. 1956, 34 312) in an attempt to overcome some discrepancies between experimental results and predictions of the theory. New selection rules have been derived by investigating the validity of the assumptions made in the earlier theory.
The new theory, applied to the symmetric Raman line of Calcite, predicts that, for the crystal orientated with its optic axis parallel to the illuminated surface, the "forbidden" component will be truly forbidden for forward or backward scattering, while appearing as previously reported for scattering at 90°.
The present investigation is concerned with measuring the relative intensities of the polarized components of this line for backward scattering, the measurements being made with the crystal orientated with its optic axis either parallel or perpendicular to the illuminated surface.
A method for increasing the scattering volume by joining several crystals along cleavage faces has been developed and a new mercury discharge lamp was designed which gave an appreciable increase of the illumination intensity. The relative intensities of the components of the symmetric Raman line obtained were evaluated by careful consideration of the characteristics of the photographic emulsion used to record them.
The results tend to confirm the predictions of the new theory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
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On the temperature dependence of the paramagnetic resonance line shape function in the case of the Ising modelYu-yang, Lee January 1961 (has links)
The adequacy of the approximation method used by
McMillan and Opechowski (1960) in their theoretical study
of the temperature dependence of the paramagnetic
resonance line shape function is very difficult to
ascertain for the case of a typical paramagnetic crystal.
For this reason the approximation method has been investigated,
in this thesis, for the very simple case of the
one-dimensional Ising model. Exact expressions for the
line shape function of the model are compared with
expressions obtained by the above mentioned approximation
method. The agreement between the two expressions is
found to be very good for all temperatures, and in
particular, for extremely low temperatures. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
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Measurement of spectral line profiles in dense plasmasJames, Harry Gordon January 1968 (has links)
The spectra emitted by a pulsed-arc discharge have been photographed with a medium resolution spectrograph to obtain Stark broadened line images measurable for both width and shift. Plasmas with densities near 10¹⁷cm⁻³ and temperatures of about 2.6 ev were produced by subjecting Argon - Nitrogen mixtures to a square current pulse. Light from the discharge was shuttered by a rotating mirror system so that the plasma was photographed in an interval during the current pulse when the plasma had optimal conditions for measurement. A technique in which the spectral lines from a standard source are photographed on the same plates as the plasma lines has been devised for calibrating the measurement routine and for facilitating shift measurements. Stark parameters were obtained by scanning the plates on a precision comparator.
Nineteen ArII lines and six NII lines were studied. For Argon, the agreement with other experimental results is satisfactory but the theory is inadequate. Similarly, the NII theory does not predict the values measured here. On the other hand, some of the qualitative predictions by the Impact theory about the line shape and about the common widths and shifts of lines in the same multiplet have been confirmed. The experiment on the NII lines also reveals advantages of the present technique over other methods for obtaining Stark parameters. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
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