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In the analysis of vascular wall dynamic information, typical oscillogram of pressure displacement wave of vascular wall (PDWVW) and speed wave information were gained from normal and patient groups, which were based on analysis theory of power spectrum. The analyzed results showed that the parameter G and H of signal A and D not only had statistical significance, but also were proportional to the elasticity of the vessel wall. So the two signals could be considered as the main characteristic parameters in quantitative diagnosis of the vascular walls elasticity diseases. It may have some clinical significance in quantitative diagnosis of early vascular diseases. [ABSTRACT FROM AUTHOR]

Krylov subspace spectral (KSS) methods have been demonstrated to be effective tools for solving time-dependent variable-coefficient PDE. They employ techniques developed by Golub and Meurant for computing elements of functions of matrices to approximate each Fourier coefficient of the solution using a Gaussian quadrature rule that is tailored to that coefficient. In this paper, we apply this same approach to time-independent PDE of the form Lu = f, where L is an elliptic differential operator. Numerical results demonstrate the effectiveness of this approach for Poisson's equation and the Helmholtz equation in two dimensions. [ABSTRACT FROM AUTHOR]

This paper presents a method for analyzing the variations of the RGB spectrum of lesion skin images using the novel segmentation process based on Six Sigma concept. This analysis further contemplates on the incidence and propagation of cancer. It is based on the underlying principles of Dr. W.A. Shewhart's Control Charts, which focuses on the fact that the variability does exist in all repetitive processes. The heterogeneous color variation within the skin is considered as an assignable cause and is due to the secretion of excess melanin. These variations possess greater magnitude as compared to the chance causes due to the color variations found in normal skins. The power of control chart that lies in its ability to separate out this assignable cause, which is one of inherent mnemonics of Malignant Melanoma, is exhibited. The proposed Six Sigma based segmentation identifies the normal skin region from the regions of lesions, besides its fuzzy border. Results show that the method produces a robust segmentation of regions of high color contrast. [ABSTRACT FROM AUTHOR]

In this paper, an objective measurement to evaluate the quality of gray scale compressed images, Image Quality Scale (IQS), has been proposed. It is defined by 5 measurements, which are Mean Square Error, Edge Measurement, Correlation Measurement, Human Visual System Measurement and Spectrum Measurement. The evaluation result is rated into 5- level grading scale, 1 to 5, which is comparable to Mean Opinion Score (MOS). The objective of this paper is to provide defining method, definition, and reliability of IQS. From the experiments, we demonstrate that the reliability (correlation coefficient) of IQS is higher than PSNR, MSE, Edge Measurement, Correlation Measurement, HVS Measurement and Spectrum Measurement. Therefore, the IQS is reliable and can be used to evaluate the quality of compressed images, JPEG and JPEG2000. [ABSTRACT FROM AUTHOR]

In the present work a methodology for quantification of modelling uncertainty using decomposed measured data is proposed. The original measured data are decomposed to deterministic and short-term components before the statistical evaluation of the modelling results is performed against the measurements. Using Fourier analysis, the spectral density was obtained for different types of air quality monitoring stations. Next, short-term fluctuations were subtracted from the original data using an iterative moving average filter and taking into account the contribution of higher frequencies determined from the spectral analysis. The methodology was used to estimate uncertainties of the results obtained with CHIMERE model for Portugal. The modelling outputs for one year are compared with the measurement data from different types of air quality stations after the subtraction of short-term variations. The comparison shows a better agreement after the application of the decomposed time series methodology. [ABSTRACT FROM AUTHOR]

For both, the analysis of haptic interaction and the quantification of haptic perception a profound knowledge of the mechanical impedance of human touch are needed. Several models for a user΄s impedance have been suggested in literature and some guidelines and quantitative values from independent models for different contact situations are available. However for the analysis of haptic interaction and the quantification of perception it is necessary to allow comparison between different grasps. Therefore a reduced set of models which covers many types of touch in an acceptable quality would be ideal. Additionally the influence of the change of touch – the pretension of fingers – on the impedance is seldom referred to and even more seldom quantified. In 2005 the authors defined a method to quantify the impedance of a three finger precision grasp. In continuation of this approach and with the aim to collect a catalogue of impedance measures, this document presents results from set of 192 measurements regarding the impedance of the index finger from eight subjects. The resulting models and their dependencies are given as approximated plots of the impedance in dependency of frequency, direction of touch and size of the contact area. The resulting curves are discussed and put into context of the influence of impedance. [ABSTRACT FROM AUTHOR]

Time-domain spectroscopic studies provide a unique perspective on the materials properties and the microscopic processes underlying them in carbon nanotubes. Ultrafast spectroscopy is used to study the dynamics and kinetics of scattering and relaxation processes from the femtosecond (1fs ≡ 10−15 s) to the picosecond timescale. This provides crucial information on carrier and exciton dynamics that underpin a variety of potential applications of carbon nanotubes, from their use as current-carrying quantum wires, through light-emitting or detecting nanodevices, to their use in light-harvesting technologies and photovoltaics. Background information on the ultrafast spectroscopic techniques of greatest applicability to nanotubes is also provided. [ABSTRACT FROM AUTHOR]

This chapter reviews three new experimental techniques for the study and characterization of carbon nanotubes and the exploration of novel phenomena. First, imaging and spectroscopy on the nanoscale is presented using near-field optical microscopy. Secondly, phonon spectroscopy with atomic resolution is demonstrated based on inelastic electron tunneling. Finally, coherent phonon generation by ultrashort laser pulses is reviewed. [ABSTRACT FROM AUTHOR]

We review recent progress in the theoretical and experimental studies of single-wall carbon nanotubes in high magnetic fields. Low-temperature magneto-transport experiments demonstrate the influence of quantum interference, disorder, and band-structure effects. Magneto-optical spectroscopy has been used to show the effects of the Aharonov-Bohm phase on the band structure and on the excitonic properties of carbon nanotubes. [ABSTRACT FROM AUTHOR]

Based on the prominent characteristic that the delay-multiply signals of the direct sequence spread spectral (DSSS) signals are periodical signals, the paper proposes an efficient method for the detection of DSSS signals: the detection, symbol period and chip width estimation of DSSS signals based on delay-multiply, correlation and spectrum analysis. The computer simulations show that the method can not only fit the need of the low signal to noise ratio which is quite common in the detection of DSSS signals, but also can give the estimations of the symbol period and chip width in a simple way. Especially, the proposed method can give an exact estimation of the symbol period by increasing the processed sampling data when the sampling rate is fixed, which is very important for the detection of DSSS signals. [ABSTRACT FROM AUTHOR]

In order to investigate the effects of swirl intensity on the characteristics of thermoacoustic instability, an experimental setup has been built including an adjustable swirl combustor. The swirl combustor includes a fuel nozzle, a straight primary air orifice and three tangential swirl secondary air pipes. The ratio of fuel nozzle diameter to that of burning chamber is 0.25. The distribution of temperature inside the combustion chamber and the fluctuating pressure were measured under different swirl intensities (0.000–0.403). The flow fields of the combustor were modeled with a large eddy simulation method. Experimental results showed that the pressure amplitude increases with the swirling intensity, and the maximum sound pressure level can be larger than 133 dB. The first order resonant frequency lies between 112 Hz and 338 Hz, showing that large span exists. The second order resonant frequency lies between 796 Hz and 822 Hz, and the third one lies between 1313 Hz and 1331 Hz, both of which maintain nearly unchanged. In the range of swirl intensity studied, the flame front moves downstream first and then moves back, and the maximum temperature reaches 1555 K. [ABSTRACT FROM AUTHOR]

Neutrino energy spectra have been calculated based on the recently measured energy spectra of Galactic very high energy γ-ray sources. Based on these neutrino spectra the expected event rates in the ANTARES neutrino telescope and KM3NeT, a future neutrino telescope in the Mediterranean Sea with an instrumented volume of one km3, have been calculated. For the brightest γ-ray sources we find event rates of the order of one neutrino per year. Although the neutrino event rates are comparable to the background from atmospheric neutrinos the detection of individual sources seems possible. [ABSTRACT FROM AUTHOR]

In 2004 and 2005, the shell-type supernova remnants RX J1713.7-3946 and RX J0852.0-4622 were observed and detected with the complete H.E.S.S. array, a system of four Imaging Cherenkov Telescopes located in Namibia and dedicated to the observations of γ-rays above 100 GeV. The energy spectra of these two sources have been measured over a wide energy range and revealed an integral flux above 1 TeV similar to that of the Crab Nebula. Their morphologies were resolved with high accuracy with H.E.S.S. and exhibit a striking correlation with the X-ray images, thereby pioneering a technique of unambiguously identifying spatially extended γ-ray sources. The results of the observations will be presented. Similarities and differences between these two sources will be pointed out as well as possible implications. [ABSTRACT FROM AUTHOR]

Nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova remnants (SNRs) is used to investigate the properties of Kepler's SNR and, in particular, to predict the γ-eay spectrum expected from this SNR. Observations of the nonthermal radio and X-ray emission spectra as well as theoretical constraints for the total supernova (SN) explosion energy Esn are used to constrain the astronomical and particle acceleration parameters of the system. Under the assumption that Kepler's SN is a type Ia SN we determine for any given explosion energy Esn and source distance d the mass density of the ambient interstellar medium (ISM) from a fit to the observed SNR size and expansion speed. This makes it possible to make predictions for the expected γ-eay flux. Exploring the expected distance range we find that for a typical explosion energy Esn=1051 erg the expected energy flux of TeV γ-rays varies from 2×10−11 to 10−13 erg/(cm2 s) when the distance changes from d=3.4 kpc to 7 kpc. In all cases the γ-eay emission is dominated by π0-decay γ-rays due to nuclear CRs. Therefore Kepler's SNR represents a very promising target for instruments like H.E.S.S., CANGAROO and GLAST. A non-detection of γ-rays would mean that the actual source distance is larger than 7 kpc. [ABSTRACT FROM AUTHOR]

LS I +61 303 has been detected by the Cherenkov telescope MAGIC at very high energies, presenting a variable flux along the orbital motion with a maximum clearly separated from the periastron passage. In the light of the new observational constraints, we revisit the discussion of the production of high-energy gamma rays from particle interactions in the inner jet of this system. The hadronic contribution could represent a major fraction of the TeV emission detected from this source. The spectral energy distribution resulting from pp interactions is recalculated. Opacity effects introduced by the photon fields of the primary star and the stellar decretion disk are shown to be essential in shaping the high-energy gamma-ray light curve at energies close to 200 GeV. We also present results of Monte Carlo simulations of the electromagnetic cascades developed very close to the periastron passage. We conclude that a hadronic microquasar model for the gamma-ray emission in LS I +61 303 can reproduce the main features of its observed high-energy γ-ray flux. [ABSTRACT FROM AUTHOR]

We fit the spectra of Cyg X-1 using two component advective flows with Keplerian accretion disks on the equatorial plane surrounded by sub-Keplerian disks when standing shocks are present. The soft photons generated by the bremsstrahlung and synchrotron processes in the sub-Keplerian flow, as well as the multi-colour black body emission from the Keplerian disk are Comptonized by the thermal and non-thermal electrons. By varying Keplerian and sub-Keplerian rates we are able to reproduce the observed soft and hard states as far as X-ray region is concerned and ‘low γ-ray intensity' and ‘high γ-ray intensity' states as far as the soft γ-ray region is concerned. We also find two pivotal points where the spectra intersect as is observed in Cyg X-1. [ABSTRACT FROM AUTHOR]

Observations of the inner radian of the Galactic disk at very high energy (VHE) gamma-rays have revealed at least 16 new sources. Besides shell type super-nova remnants, pulsar wind nebulae (PWN) appear to be a dominant source population in the catalogue of VHE gamma-ray sources. Except for the Crab nebula, the newly discovered PWN are resolved at VHE gamma-rays to be spatially extended (5-20 pc). Currently, at least 3 middle aged (t>10 kyrs) PWN (Vela X, G18.0-0.7, and G313.3+0.6 in the "Kookaburra" region) and 1 young PWN MSH 15-52 (t=1.55 kyrs) have been identified to be VHE emitting PWN (sometimes called "TeV Plerions"). Two more candidate "TeV Plerions" have been identified and have been reported at this conference (Carrigan, These proceedings, in preparation). In this contribution, the gamma-ray emission from Vela X is explained by a nucleonic component in the pulsar wind. The measured broad band spectral energy distribution is compared with the expected X-ray emission from primary and secondary electrons. The observed X-ray emission and TeV emission from the three middle aged PWN are compared with each other. [ABSTRACT FROM AUTHOR]

Spectral analysis is a particularly valuable method for seeking dependences expressed as lags between different magnitudes. Its use in this article was first determined by the search for maximum objectivity in the observation of time series. The possibility of applying it to a large number of series was then examined. This twin requirement resulted from a desire to avoid the criticism generally levelled at statistical studies concerning cyclical movements of the economy. Spectral analysis is based on the theory of stochastic processes. It starts with the core hypothesis that a given time series consists of a large number of sinusoidal components with different frequencies (univariate spectral analysis). It makes it possible to divide a particular category of records into a set of oscillations of different frequencies and then to show the links between the components with the same frequency in the various series examined (cross-spectral or bivariate spectral analysis). It has had limited applications in cliometrics to date. It is used here to determine the frequency of GDP series of several OECD countries. A reminder of the method (I) is followed by successive examination of the various series chosen, the treatment of these series and the results of spectral analysis (II). It is then possible as a conclusion to show the prospects of this type of approach and to synthesise a completely new major result for understanding economic dynamics in the nineteenth and twentieth centuries, that is to say the existence of a single intermediate cycle with 15 to 20-year frequency that calls into question or even partially contradicts previous work on economic cycles. [ABSTRACT FROM AUTHOR]

MRS evaluation of stroke is a promising technique in that it images intracellular metabolites and thus may eventually serve as a surrogate for the triage of stroke victims concerning treatment. Despite its newfound speed of performance, constantly improving availability and lack of ionizing radiation, several problems persist and dominate its sparing use. Its manifestation of metabolites is relatively unique but apparently not yet distinctive or clinically relevant for most clinical stroke scenarios. At present, MRS should not be used alone but rather in combination with conventional, diffusion-weighted and perfusion-weighted MR imaging for optimal effect in the management of acute stroke patients. [ABSTRACT FROM AUTHOR]

This chapter is dedicated to scanning probe microscopy, one of the most important techniques in nanotechnology. In general, scanning probe techniques allow the measurement of physical properties down to the nanometer scale. Some techniques, such as the scanning tunneling microscope and the scanning force microscope even go down to the atomic scale. The properties that are accessible are various. Most importantly, one can image the arrangement of atoms on conducting surfaces by scanning tunneling microscopy and on insulating substrates by scanning force microscopy. But also the arrangement of electrons (scanning tunneling spectroscopy), the force interaction between different atoms (scanning force spectroscopy), magnetic domains (magnetic force microscopy), the local capacitance (scanning capacitance microscopy), the local temperature (scanning thermo microscopy), and local light-induced excitations (scanning near-field microscopy) can be measured with high spatial resolution. In addition, some techniques even allow the manipulation of atomic configurations. Probably the most important advantage of the low-temperature operation of scanning probe techniques is that they lead to a significantly better signal-to-noise ratio than measuring at room temperature. This is why many researchers work below 100 K. However, there are also physical reasons to use low-temperature equipment. For example, the manipulation of atoms or scanning tunneling spectroscopy with high energy resolution can only be realized at low temperatures. Moreover, some physical effects such as superconductivity or the Kondo effect are restricted to low temperatures. Here, we describe the design criteria of low-temperature scanning probe equipment and summarize some of the most spectacular results achieved since the invention of the method about 20 years ago. We first focus on the scanning tunneling microscope, giving examples of atomic manipulation and the analysis of electronic properties in different material arrangements. Afterwards, we describeresults obtained by scanning force microscopy, showing atomic-scale imaging on insulators, as well as force spectroscopy analysis. Finally, the magnetic force microscope, which images domain patterns in ferromagnets and vortex patterns in superconductors, is discussed. Although this list is far from complete, we feel that it gives an adequate impression of the fascinating possibilities of low-temperature scanning probe instruments. In this chapter low temperatures are defined as lower than about 100K and are normally achieved by cooling with liquid nitrogen or liquid helium. Applications in which SPMs are operated close to 0 °C are not covered in this chapter. [ABSTRACT FROM AUTHOR]

In this paper we propose a new algorithm for the de novo peptide sequencing problem. This problem reconstructs a peptide sequence from a given tandem mass spectra data containing n peaks. We first build a directed acyclic graph G = (V, E) in O(n log n) time, where v ∊ V is a spectrum mass ion or a complementary mass to a spectrum ion. The solutions of this problem are then given by the paths in the graph between two designated vertices. Unlike previous approaches, the proposed algorithm does not use dynamic programming, but it builds the graph in a progressive fashion using a priority queue, thus obtaining an improvement over other methods [1,2]. [ABSTRACT FROM AUTHOR]

Chapter 5 is dedicated to the processing of stochastic processes using discrete transforms and model-based approaches. It explains the Karhunen-Loeve transform and the whitening transform, gives an introduction to linear estimation theory and optimal filtering, addresses Wiener filters, linear predictors, the Yule-Walker equation, and discusses methods of estimating autocorrelation sequences and power spectra. [ABSTRACT FROM PUBLISHER]

The article focuses on cellular telephony and the introduction of the first generation of cellular systems. Such systems served mobile telephone calls via analog transmission of voice traffic. Despite the fact that 10 systems are considered technologically primitive today, the fact remains that a significant number of people still use analog cellular phones and analog cellular infrastructure is found throughout North America and other parts of the world. Furthermore, they have found use as a basis for the development of several second generation systems. An example of this is D-AMPS, which is a 20 system evolving from AMPS. AMPS divides the frequency spectrum into several channels, each 30 kHz wide. These channels are either speech or control channels. Speech channels utilize Frequency Modulation, while control channels can use Binary Frequency Shift Keying at a rate of 10 kb/s. Both data messages and frequency tones are used for AMPS control signaling and two operators can be collocated in the same geographical area. There are two versions of NMT. The first operates in the area around 450 MHz and the second operates in the area around 900 MHz. These variants are known as NMT 450 and NMT 900, respectively.

The article focuses on imaging system based on terahertz radiation. Terahertz radiation lies between microwave and infrared frequencies. It has widespread potential applications in medicine, microelectronics, agriculture, forensic science. Coherent terahertz time-domain spectroscopy that has an ultrawide bandwidth provides a new method for characterizing the electronic, vibronic, and compositional properties of solid, liquid, and gas phase materials, as well as flames and flows. In an imaging system that bas a single terahertz antenna, the image is obtained by pixel-scanning the sample in two dimensions done with the help of free-space electro-optic detection.

The article examines the fundamental principles on the formation of high resolution secondary ion mass spectroscopy (SIMS) imaging, a modern surface analysis technique that reveals the presence of ionic residues such as sodium, potassium, fluorine and chlorine in corroded or stained areas. It identifies digital micrographs as one of the most effective vehicles for recording the retrieved information quantitatively. The emergence of SIMS imaging can be accounted to the development of finely focused scanning ion microscopes and microprobes.

The article provides information on the design and background material of electromagnetic wave propagation, more usually called radio propagation. Each types of frequency bands have different propagation characteristics. For instance, the frequency band of atmospheric absorption is below ten gigahertz. The appearance of molecular absorption during electromagnetic propagation is due to atmospheric water vapor, oxygen and trace gases.

The article discusses the techniques and basic considerations that need to be taken into account when analyzing sound. Short-term Fourier transform (STFT) process is far from being unsupervised, and its settings are indeed critical in order to get a good representation of the sound. The main parameters involved in this step are window size, window type, frame size and hop size. The sinusoidal model assumes that each spectrum of the STFT representation can be explained by a series of sinusoids. For a given frequency resolution, using enough points in the spectrum, a sinusoid can be identified by its shape.

The article focuses on the sinusoidal model for conversion of time-domain signal into its frequency representation. The most common approach is though short-time Fourier transform (STFT), but the sinusoidal model represents a step towards a more flexible representations while compromising both sound fidelity and computing time. It is based on modeling the time-varying spectral characteristics of a sound as sums of time-varying sinusoids. Still sinusoidal model added with residual model is best. The sinusoidal plus residual model can cover a wide "compromise space" and can in fact be seen as the generalization of both the STFT and the sinusoidal models.

The article discusses the notations of terms for the application to digital audio effects. The computation of the time-varying spectrum of an input signal can also be interpreted as a parallel bank of bandpass filters. Each bandpass signal is obtained by filtering the input signal with the corresponding bandpass filter. The interpretation offers analysis of a signal by a filter bank, modification of the short-time spectrum on a sample-by-sample basis and synthesis by a summation of the bandpass signals.

Temporal, spatial and spatio-temporal decorrelations play important roles in signal processing. These techniques are based only on second order statistics (SOS). They are the basis for modern subspace methods of spectrum analysis and array processing and often used in a preprocessing stage in order to improve convergence properties of adaptive systems, to eliminate redundancy or to reduce noise. Spatial decorrelation or prewhitening is often considered as a necessary (but not sufficient) condition for the stronger stochastic independence criteria. After prewhitening, the BSS or ICA tasks usually become somewhat easier and well-posed (less ill-conditioned), because the subsequent separating (unmixing) system is described by an orthogonal matrix for real-valued signals and a unitary matrix for complex-valued signals and weights. Furthermore, spatio-temporal and time-delayed decorrelation can be used to identify the mixing matrix and perform blind source separation of colored sources. In this chapter, we discuss and analyze a number of efficient and robust adaptive and batch algorithms for spatial whitening, orthogonalization, spatio-temporal and time-delayed blind decorrelation. Moreover, we discuss several promising robust algorithms for blind identification and blind source separation of non-stationary and/or colored sources. [ABSTRACT FROM PUBLISHER]

Chapter 7 details a new method, based upon signalling random process theory, for evaluating the power spectral density of a random process after a nonlinear memoryless transformation. The approach is successfully applied to the difficult area of FM spectral analysis. [ABSTRACT FROM PUBLISHER]

After completing this chapter, the reader should be able to: Explain the phenomenon of free induction decay; State the rationale for use of the spin-echo technique in imaging; Define T2*; Explain the pulsing and signal acquisition scheme used in the following pulse sequences: Spin-echo; Carr-Purcell-Meiboom-Gill; Inversion recovery; Gradient-echo; Chart the order of occurrence of RF pulses, gradient magnetic fields, and signal acquisition in spatially encoded spin-echo imaging; Explain how the two-dimensional Fourier transform (2DFT) method is used to construct the MR image; Calculate the time required to obtain an image using the spin-echo technique; List some motion suppression techniques; Give the physical principle that underlies the use of contrast agents in MR; Explain the physiological basis of functional MRI (fMRI); List reasons for tissue contrast, differences in MR signal among voxels, and how these differences are highlighted through the choice of pulse sequence parameters; Explain the chemical basis of MR spectroscopy and give some examples of nuclei that are studied. [ABSTRACT FROM PUBLISHER]

After completing this chapter, the reader should be able to: Write the Doppler equation and use it to calculate the Doppler shift; Describe the effect of Doppler angle upon frequency shift and describe how error in estimation of the angle influences the accuracy of velocity estimation; Determine volumetric flow from average velocity and vessel cross-sectional area; Name the main components of a Doppler ultrasound imager; Calculate range gate size and depth from timing information; Describe the differences between information obtained from pulsed-wave versus continuous-wave Doppler; Describe the main features of a frequency spectrum and describe how it is used in constructing the Doppler spectral trace; Describe how color is assigned in color Doppler; Discuss some reasons for spectral broadening. [ABSTRACT FROM PUBLISHER]

We have briefly discussed a wide range of spectroscopic techniques that involve the use of electrons and/or photons. These techniques yield very detailed information about occupied and empty electron energy bands and also core levels of semiconductors. The angle-resolved versions of photoemission and inverse photoemission have produced convincing pictures of the E(k) dependence of bulk electronic states. They also have yielded information on surface states. We presented spectra of excitations of core levels and discussed the information that can be obtained from them. We also introduced the concepts of surface reconstruction, electronic surface states, and surface energy bands, and presented a few phenomena related to them, such as Fermi level pinning. This led to a brief discussion of the technologically important concepts of charge depletion and enrichment layers at semiconductor surfaces. [ABSTRACT FROM AUTHOR]

Chapters 6 and 7 are devoted to the study of the optical properties of semiconductors. In this chapter we have discussed those phenomena involving only one photon frequency. In processes like absorption and reflection an incident electromagnetic wave illuminates the sample and the frequency of the wave is unchanged by its interaction with the sample. In the following chapter we shall discuss phenomena in which the frequency of the incident wave is altered by the sample. The optical properties of the sample studied in this chapter can be completely described by its complex dielectric function. A microscopic theory of this function shows that photons interact mainly with the electrons in semiconductors by exciting interband and intraband transitions. Interband transitions from the valence bands to the conduction bands produce peaks and shoulders in the optical spectra which can be attributed to Van Hove singularities in the valence-conduction band joint density of states. These structures can be greatly enhanced by using the technique of modulation spectroscopy, in which the derivatives of some optical response function with respect to either frequency or an external modulation (such as electric and stress fields) are measured. These optical measurements have provided an extremely sensitive test of existing electronic band structure calculations. Occasionally, disagreements between experimental and theoretical spectral peak positions and lineshapes have been found. These can be explained by the excitonic effect as a result of the Coulomb interaction between excited electrons and holes in the semiconductor. Intraband electronic transitions occur in doped semiconductors and their contribution to the optical properties can be obtained by using the Drude model proposed for free electrons in simple metals. Transitions between the discrete levels of impurities in semiconductors can also contribute to absorption of photons in the infrared. Although these extrinsic absorption processes are much waker than those involving intrinsic electronic transitions, they can give rise to extremely sharp peaks and have been a very useful and highly sensitive probe of the electronic energy levels of impurities. Finally, in polar semiconductors, such as those with the zincblende crystal structure, photons can be absorbed and reflected as a result of interaction with optical phonons. The reflectivity becomes particularly high for photons with frequency between the TO and LO phonon frequencies, giving rise to a phenomenon known for a long time as reststrahlen. The coupling between infrared-active optic phonons and electromagnetic waves can be so strong that they cannot be separated inside the medium. Instead, they should be regarded as coupled waves or quasiparticles known as phonon-polaritons. [ABSTRACT FROM AUTHOR]

The article presents information on the linear prediction and extrapolation. Linear prediction' is a means of estimating a missing sample of a sampled function. As the name implies, the missing sample is calculated as a linear combination of the known samples. The usefulness of linear prediction in spectroscopy comes from its property that it lends itself readily to extrapolation. By applying linear prediction repeatedly, using predicted sample estimates to predict more estimates, one is able to extrpolate a measured signal.

The article presents information on the processing of signal and spectrum. The process of finding estimates for the values of a function at new points between known data by computational methods is called interpolation. A fast and simple interpolation method is obtained by the use of Fourier transforms. A measured spectrum generally contains undesired components, noise, in addition to the actual spectrum. An alternative solution for the elimination of high-frequency noise is low-pass filtering. Low-pass filtering is a special case of band-pass filtering, which filters away all other frequencies of the spectrum than the desired bands containing information.

The article presents information on Fourier self-deconvolution (FSD). In Fourier self-deconvolution, FSD, the spectrum is deconvolved by the line shape of the spectrum itself. The line shape is a line situated in the origin, and it has an area equal to one. In FSD, the signal in t-domain is divided by the Fourier transform of the line shape function. A return to f-domain by inverse Fourier transform gives a spectrum with narrower spectral lines. Since deconvolution is equivalent to division in i-domain, it is clearly a linear operation. Deconvolving a linear combination of spectral lines of various heights simultaneously gives the same result as deconvolving each line separately, providing that they have a common line shape.

The article presents information on Fourier transform spectroscopy (FTS). A. A. Michelson invented in the 1880s a simple interferometer, which basically consists of a beamsplitter and two plane mirrors. Initially, the interferometer was used to study the speed of light and to fix the standard meter with the wavelength of a spectral line. The Michelson interferometer is very simple, but its principles of function can be applied to other interferometers used in Fourier transform spectroscopy, FTS. The incident beam is divided by a beamsplitter B into two parts: the reflected beam travels to a fixed mirror and back, and the transmitted beam travels to a moving mirror and back.

The article presents information on Nuclear magnetic resonance (NMR) spectroscopy. The goal of nuclear magnetic resonance, NMR, is to study molecular structures, molecular motion, and various chemical characteristics. This kind of information can be found in the nuclear magnetic resonance spectrum. The NMR spectrum reveals the Larmor frequencies of the nuclei in a sample. The sum of the precessing magnetic moments of nuclei in a static magnetic field, that is, the macroscopic magnetic moment M, lies along the z-axis (the direction of the magnetic field). In order to be able to measure M to obtain an NMR spectrum, it is necessary to rotate M in such a way that an observable component is achieved along, say, y-axis.

The article presents information on Ion cyclotron resonance (ICR) mass spectrometry. In the absence of an electric field, only the magnetic component of the force is present. Because of the properties of the vector product, the magnetic force is perpendicular to the plane determined by the velocity and the magnetic field. If v would be parallel to B, then the force would be zero. A mass spectrometer is an instrument which separates ions of different mass-to-charge ratios m/q. In a uniform magnetic field, ions of different m/q but constant velocity v have a different radius of orbit R, and they can be separated.

The article presents some basic definitions of Fourier's transforms in Spectroscopy. In the Fourier series, a function h(t) is analyzed into an infinite sum of harmonic components at multiples of the fundamental frequency. If the Fourier series is truncated, and h(t) is approximated by a sum of only a finite number of terms of the Fourier series, then this approximation differs somewhat from h(t). Generally, the approximation becomes better and better as more and more terms are included. The Delta function, also called the impulse function, is a concept which is frequently used to describe quantities which are localized in one point. Even though real physical quantities cannot be truly localized in exactly one point, the concept of delta function is very useful.

This chapter of the book "Advanced Digital Signal Processing and Noise Reduction," begins with an introduction to the basic ideas of deconvolution and channel equalization. The author studies blind equalization based on the channel input power spectrum, equalization through separation of the input signal and channel response models, Bayesian equalization, nonlinear adaptive equalization for digital communication channels, and equalization of maximum-phase channels using higher-order statistics.

The power spectrum reveals the existence, or the absence, of repetitive patterns and correlation structures in a signal process. The power spectrum of a signal gives the distribution of the signal power among various frequencies. The power spectrum is the Fourier transform of the correlation function, and reveals information on the correlation structure of the signal. The strength of the Fourier transform in signal analysis and pattern recognition is its ability to reveal spectral structures that may be used to characterize a signal.

It is easy enough to measure the frequency of a clean sinusoid, assuming that we have seen enough of the signal for its frequency to be determinable. For more complex signals the whole concept of frequency becomes more complex. We previously saw two distinct meanings, the spectrum and the instantaneous frequency. There is yet a third definition. Model based spectral estimation methods assume a particular mathematical expression for the signal and estimate the parameters of this expression. This technique extends the idea of estimating the frequency of a signal assumed to be a perfect sinusoid. The difference here is that the assumed functional form is more complex. One popular model is to assume the signal to be one or more sinusoids in additive noise, while another takes it to be the output of a filter. This approach is truly novel, and the uncertainty theorem does not directly apply to its frequency measurements. [ABSTRACT FROM PUBLISHER]

Signals dwell both in the time and frequency domains; we can equally accurately think of them as values changing in time (time domain), or as blendings of fundamental frequencies (spectral domain). The method for determining these fundamental frequencies from the time variations is called Fourier or spectral analysis. Similar techniques allow returning to the time domain representation from the frequency domain description. [ABSTRACT FROM PUBLISHER]