Amplitude Modulation

This paper deals with the characterization of blood ultrasonic Doppler signals via the computation of the "mean fractal dimension". We show and we discuss the existing links between the "mean fractal dimension" and the well-known mean frequency and the bandwidth usually used to characterize the blood Doppler signals. To finish, we calculate and we discuss all these parameters in the

A family of silicon micro-sensors for Atomic Force Microscope (AFM) is presented that allows to operate with integrated transducers from medium to high frequencies together with moderate stiffness constants. The sensors are based on Micro-Electro-Mechanical-Systems technology. The vertical design specifically enables a long tip to oscillate perpendicularly to the surface to be imaged. The tip is part of a resonator including quasi-flexural composite beams, and symmetrical transducers that can be used as piezoresistive detector and/or electro-thermal actuator. Two vertical probes (Vprobes) were operated up to 4.3 MHz with stiffness constants 150 N/m to 500 N/m and the capability to oscillate from 10 pm to 90 nm. AFM images of several samples both in amplitude modulation (tapping-mode) and in frequency modulation were obtained.

We present a simulation study on the chirping characteristics of a directly modulated 40 Gbps laser diode and evaluate its performance for use in high-speed optical fiber links. The effects of the linewidth enhancement factor (α) and gain suppression on the laser chirp and the maximum fiber transmission length are investigated. The chirp characteristics include the frequency peak-to-peak chirp of the time-varying frequency and shift of the emission wavelength. The performance of 40 Gbps optical fiber link is evaluated in terms of the eye diagram and quality factor of the received signal, which helps in predicting the maximum fiber length that achieves error-free transmission. The results show that when α increases from 1 to 10, the overshoots of the relaxation oscillations become strong, resulting in a sharp increase in laser peak-to-peak chirp from 21.8 to 205 GHz. The increase of gain suppression factor form ε = 0.5 × 10-17 cm 3 to ε = 5 × 10-17 cm 3 dampens out the overshoots and slightly reduces the peak-to-peak chirp from 19.5 to 193.3 GHz. Although the gain suppression works to reduce the laser chirp, it causes a significant wavelength shift relative to the emission wavelength of the non-modulated laser, which degrades the efficiency of the laser diode. On the other hand, the gain suppression is shown to increase the degree of eye-opening and the corresponding Q-factor of the fiber link on a reverse action of the linewidth enhancement factor. As fiber length increases, the influences of α and ε on chirp characteristics become more significant. The maximum fiber length (L max) is shown to decrease with the increase in α and/or ε; when α increases from 1 to 10, L max decreases from 5.89 to 0.78 km at ε = 5 × 10-17 cm 3 , and decreases from 2.52 to 0.3 km at ε = 0.5 × 10-17 cm 3 .

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a lowcomplexity, small form-factor and lossless modulator based on a semiconductor optical amplifier and electro-absorption modulator. Flexible amplitude/phase format transmission up to 8-QAM is validated.

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb ∕ s per-user bandwidth is investigated for a long reach of 100 km, and its compatibility with a potentially high split is verified.

The speech signal has been shown to contain a fine structure that consists of the fast changing spectral content (e.g., formant transitions, voicing, spectral energy distributions), together with amplitude modulations of the envelope with different timescales. These different modulation frequencies have been associated with linguistic units of different sizes, and neuronal oscillations seem to track this linguistic structure. As the amplitude envelope mostly captures suprasegmental information, the different modulation frequencies are natural candidates to convey prosodic information. In this paper we put these assumptions to the test by comparing effects of sentence length and language, focusing on languages with distinct prosodic profiles: Brazilian Portuguese (syllable-timed), European Portuguese (mixed rhythm, with syllable-timed and stress-timed properties), and German (stress-timed). There are further differences regarding the roles of the syllable, the foot, the prosodic word and the intonation phrase. We analyzed wideband amplitude envelopes using general additive mixed models and show that German differs from Brazilian Portuguese and European Portuguese in the delta (1-2Hz) and theta bands (6-8Hz). European and Brazilian Portuguese also differ, but only in the delta band (1-2Hz). The language differences in amplitude modulation are discussed in terms of speech rhythm and differences in prosodic structure across languages.

Cochlear implants encode speech information by stimulating the auditory nerve with amplitudemodulated pulse trains. A computer model of the auditory nerve's response to electrical stimulation can be used to evaluate different approaches to improving CI patients' perception. In this paper a computationally efficient stochastic and adaptive auditory nerve model was used to investigate full nerve responses to amplitude-modulated electrical pulse trains. The model was validated for nerve responses to AM pulse trains via comparison with animal data. The influence of different parameters, such as adaptation and stochasticity, on long-term adaptation and modulation-following behavior was investigated. Responses to pulse trains with different pulse amplitudes, amplitude modulation frequencies, and modulation depths were modeled. Rate responses as well as period histograms, Vector Strength and the fundamental frequency were characterized in different time bins. The response alterations, including frequency following behavior, observed over the stimulus duration were similar to those seen in animal experiments. The tested model can be used to predict complete nerve responses to arbitrary input, and thus to different sound coding strategies.

Cochlear implants encode speech information by stimulating the auditory nerve with amplitudemodulated pulse trains. A computer model of the auditory nerve's response to electrical stimulation can be used to evaluate different approaches to improving CI patients' perception. In this paper a computationally efficient stochastic and adaptive auditory nerve model was used to investigate full nerve responses to amplitude-modulated electrical pulse trains. The model was validated for nerve responses to AM pulse trains via comparison with animal data. The influence of different parameters, such as adaptation and stochasticity, on long-term adaptation and modulation-following behavior was investigated. Responses to pulse trains with different pulse amplitudes, amplitude modulation frequencies, and modulation depths were modeled. Rate responses as well as period histograms, Vector Strength and the fundamental frequency were characterized in different time bins. The response alterations, including frequency following behavior, observed over the stimulus duration were similar to those seen in animal experiments. The tested model can be used to predict complete nerve responses to arbitrary input, and thus to different sound coding strategies.

A digital sinusoidal oscillator derived from digital waveguide theory is described which has good properties for VLSI implementation. Its main features are no wavetable and a computational complexity of only one multiply per sample when amplitude and frequency are constant. Three additions are required per sample. A piecewise exponential amplitude envelope is available for the cost of a second multiplication per sample, which need not be as expensive as the tuning multiply. In the presence of frequency modulation (FM), the amplitude coefficient can be varied to exactly cancel amplitude modulation (AM) caused by changing the frequency of oscillation. Contents 1 Introduction 2 The Second-Order Waveguide Filter 3 Conclusions

This paper addresses dereverberation of speech using an unsupervised approach utilizing speech prior and taking only weak assumptions on reverberation. Our approach uses a long time context representation of reverberated speech in spectraltemporal supervectors which are decorrelated by PCA. In the decorrelated domain, supervectors are mapped from the reverberant speech distribution to the clean speech distribution and then to mel-spectral vectors. A mel-domain Wiener filter is applied as post processing. Our results demonstrate performance gains over the provided baseline recognizer, and show that the method can be coupled to CMLLR adaptation with cumulative benefits for clean trained models. Furthermore, we show that using dimensionality reduction coupled with the Wiener filter is better than using full-dimensional PCA in representing small variance components in speech.

This study examined the contribution of temporal and spectral modulation sensitivity to discrimination of stimuli modulated in both the time and frequency domains. The spectrotemporally modulated stimuli contained spectral ripples that shifted systematically across frequency over time at a repetition rate of 5 Hz. As the ripple density increased in the stimulus, modulation depth of the 5 Hz amplitude modulation (AM) reduced. Spectrotemporal modulation discrimination was compared with subjects’ ability to discriminate static spectral ripples and the ability to detect slow AM. The general pattern from both the cochlear implant (CI) and normal hearing groups showed that spectrotemporal modulation thresholds were correlated more strongly with AM detection than with static ripple discrimination. CI subjects’ spectrotemporal modulation thresholds were also highly correlated with speech recognition in noise, when partialing out static ripple discrimination, but the correlation was not sign...

Development of technique for synthesizing multilevel sequences with good correlation properties is very useful for several radar applications where as a set of phase and amplitude coded sequences will be synthesized directly for compression technique. In reality, the signal processing also been significant to transmit or store signals, to enhance desired signal component and to extract useful information carried by signals. Consequently, this paper describes affectively methods to generating the finite length multilevel sequence of any length that have low side lobe energy (SLE) and improved energy ratio (ER) in their autocorrelation function (ACF). Testing for the stability and the analyzing of systems zero pattern using z-transform for the generating sequence indicates a possible position of roots in the radius of circle lies. This is illustrated by application of 13-element Huffman code as a starting sequence, this technique more low complexity and compatible compared inverse fil...

Performance limits of coded multilevel differential PSK (MDPSK) in multipath Rayleigh fading channels are described. The simple "Gaussian metric" is assumed for reasons for practicality even though it is not the maximum likelihood. Channel cutoff rate RO of MDPSK is analyzed based on the metric. Account is taken of additive white Gaussian noise (AWGN), cochannel interference, and multipath channel delay spread. For the analysis of the spectrum efficiency of a cellular mobile radio system employing coded MDPSK, its service area is defined as the area in which, with a bit rate of R information bit/symbol ( R 5 Ro ), reliable communications are possible. Three optimal information bit rates are determined from the channel cutoff rate to minimize the required average signal energy per information bit-to-noise power spectral density ratio ( E,, ), to maximize the tolerable rms delay spread T> and to maximize the spectrum efficiency.

In many animals, the information most important for processing communication sounds, including speech, consists of temporal envelope cues below ϳ20 Hz. Physiological studies, however, have typically emphasized the upper limits of modulation encoding. Responses to sinusoidal AM (SAM) are generally summarized by modulation transfer functions (MTFs), which emphasize tuning to modulation frequency rather than the representation of the instantaneous stimulus amplitude. Unfortunately, MTFs fail to capture important but nonlinear aspects of amplitude coding in the central auditory system. We focus on an alternative data representation, the modulation period histogram (MPH), which depicts the spike train folded on the modulation period of the SAM stimulus. At low modulation frequencies, the fluctuations of stimulus amplitude in decibels are robustly encoded by the cycle-by-cycle response dynamics evident in the MPH. We show that all of the parameters that define a SAM stimulus-carrier frequency, carrier level, modulation frequency, and modulation depth-are reflected in the shape of cortical MPHs. In many neurons that are nonmonotonically tuned for sound amplitude, the representation of modulation frequency is typically sacrificed to preserve the mapping between the instantaneous discharge rate and the instantaneous stimulus amplitude, resulting in two response modes per modulation cycle. This behavior, as well as the relatively poor tuning of cortical MTFs, suggests that auditory cortical neurons are not well suited for operating as a "modulation filterbank." Instead, our results suggest that Ͻ20 Hz, the processing of modulated signals is better described as envelope shape discrimination rather than modulation frequency extraction.

The encoding of sound level is fundamental to auditory signal processing, and the temporal information present in amplitude modulation is crucial to the complex signals used for communication sounds, including human speech. The modulation transfer function, which measures the minimum detectable modulation depth across modulation frequency, has been shown to predict speech intelligibility performance in a range of adverse listening conditions and hearing impairments, and even for users of cochlear implants. We presented sinusoidal amplitude modulation (SAM) tones of varying modulation depths to awake macaque monkeys while measuring the responses of neurons in the auditory core. Using spike train classification methods, we found that thresholds for modulation depth detection and discrimination in the most sensitive units are comparable to psychophysical thresholds when precise temporal discharge patterns rather than average firing rates are considered. Moreover, spike timing information was also superior to average rate information when discriminating static pure tones varying in level but with similar envelopes. The limited utility of average firing rate information in many units also limited the utility of standard measures of sound level tuning, such as the rate level function (RLF), in predicting cortical responses to dynamic signals like SAM. Response modulation typically exceeded that predicted by the slope of the RLF by large factors. The decoupling of the cortical encoding of SAM and static tones indicates that enhancing the representation of acoustic contrast is a cardinal feature of the ascending auditory pathway.

We theoretically study the performance of multiple-input multiple-output (MIMO) free-space optical (FSO) systems using subcarrier quadrature modulation (SC-QAM) signaling. The system average symbolerror rate (ASER) is derived taking into account the atmospheric turbulence effects on the MIMO/FSO channel, which is modeled by log-normal and the gamma-gamma distributions for weak and moderate-to-strong turbulence conditions. We quantitatively discuss the influence of index of refraction structure parameter, link distance, and different MIMO configurations on the system ASER. We also analytically derive and discuss the MIMO/FSO average (ergodic) channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE), under the impact of various channel conditions. Monte Carlo simulations are also performed to validate the mathematical analysis, and a good agreement between numerical and simulation results is confirmed.

We experimentally demonstrate the photonic generation of symmetrical waveforms based on amplitude-only modulation in a fiber-based temporal pulse shaping (TPS) system. A rectangular waveform with a 3-dB width of 18.8 ps and a triangular waveform with a 3-dB width of 6.7 ps are experimentally generated.

We propose and experimentally demonstrate a modulation technique for closed-loop interferometric fiber optic gyroscopes that improves its scale factor control and allows for the construction of gyroscopes with optimized angle random walk. The proposed two-level and two-period modulation is composed of two intercalated periods of the square wave modulation, one with amplitude of ϕ  rad and the other with amplitude of 2π-ϕ  rad. As in the two-level modulation, the angular velocity is obtained from the difference of consecutive output levels. Modulation depth error is obtained from the difference of the mean levels of the output from two consecutive periods. The proposed technique eliminates the limitation of square wave modulation: inefficient scale factor control at low angular velocities. Additionally, it requires a slower analog-to-digital converter than four-level modulation.

We analyze the conductance fluctuations observed in the quantum Hall regime for a bulk twodimensional electron system in a Corbino geometry. We find that characteristics like the power spectral density and the temperature dependence agree well with simple expectations for universal conductance fluctuations in metals, while the observed amplitude is reduced. In addition, the dephasing length LΦ ∝ T -1/2 , which governs the temperature dependence of the fluctuations, is surprisingly different from the scaling length Lsc ∝ T -1 governing the width of the quantum Hall plateau transition.

The auditory steady state response (aSSR) is an oscillatory electrical potential recorded from the scalp induced by amplitudemodulated (AM) or click/tone burst stimuli. Its clinical utility has been limited by uncertainty regarding the specific areas of the brain involved in its generation. To identify the generators of the aSSR, 15 O-water PET imaging was used to locate the regions of the brain activated by a steady 1 kHz pure tone, the same tone amplitude modulated (AM) at 40 Hz and the specific regions of the brain responsive to the AM component of the stimulus relative to the continuous tone. The continuous tone produced four clusters of activation. The boundaries of these activated clusters extended to include regions in left primary auditory cortex, right non-primary auditory cortex, left thalamus, and left cingulate. The AM tone produced three clusters of activation. The boundaries of these activated clusters extended to include primary auditory cortex bilaterally, left medial geniculate and right middle frontal gyrus. Two regions were specifically responsive to the AM component of the stimulus. These activated clusters extended to include the right anterior cingulate near frontal cortex and right auditory cortex. We conclude that cortical sites, including areas outside primary auditory cortex, are involved in generating the aSSR. There was an unexpected difference between morning and afternoon session scans that may reflect a pre-versus post-prandial state. These results support the hypothesis that a distributed resonating circuit mediates the generation of the aSSR.

Spatial Modulation (SM) is a promising technique for future wireless communication systems, as it reduces hardware cost and complexity while maintaining good bit error rate (BER) performance in MIMO systems. However, in real-world scenarios, systems often face challenges like antenna correlation and partial knowledge of the channel at the receiver (CSIR). This paper examines the performance of a new communication method called Generalized Quadrature Spatial Modulation (GQSM), combined with Quasi-Orthogonal Space-Time Block Codes (QOSTBC), under realistic fading conditions using Nakagami-m channels. To address the impact of imperfect CSIR, the paper introduces three new QR decomposition-based detection techniques. These methods are specifically designed to reduce errors and enhance reliability in conditions where traditional maximum likelihood (ML) detection performs poorly. A detailed theoretical analysis of all three detection schemes is provided to explain their performance and advantages. Among them, Technique III yields the best results in extensive Monte Carlo simulations, demonstrating improved error performance with significantly lower computational complexity than ML detection. Overall, the proposed detection methods not only overcome the limitations of ML detection but also provide a practical and scalable solution for challenging wireless environments by effectively leveraging the numerical stability of QR decomposition.

In this paper design and characteristics of a simple direct QPSK modulator for terrestrial point-to-point radio link is presented. This modulator enables compact, low cost and high efficiency transmitter. Good sideband suppression, greater then 25 dB is obtained in frequency range 21.0 to 24.0 GHz, without tuning. The insertion loss is less than 8 dB in 3-GHz bandwidth and the carrier suppression is about 22 dB.

An experiment conducted in the Mediterranean Sea in April 1996 demonstrated that a time-reversal mirror (or phase conjugate array) can be implemented to spatially and temporally refocus an incident acoustic field back to its origin. The experiment utilized a vertical source–receiver array (SRA) spanning 77 m of a 125-m water column with 20 sources and receivers and a single source/receiver transponder (SRT) colocated in range with another vertical receive array (VRA) of 46 elements spanning 90 m of a 145-m water column located 6.3 km from the SRA. Phase conjugation was implemented by transmitting a 50-ms pulse from the SRT to the SRA, digitizing the received signal and retransmitting the time reversed signals from all the sources of the SRA. The retransmitted signal then was received at the VRA. An assortment of runs was made to examine the structure of the focal point region and the temporal stability of the process. The phase conjugation process was extremely robust and stable, an...

Recently, the need to extra frequency bands is increasing significantly due to modern devices and applications. This problem can be addressed by exploiting the idle spectra. Thus, the spectrum exploiting is performed using the technique of spectrum sensing. In this paper, a new cooperative spectrum sensing scheme is proposed based on discrete cosine transform periodogram. This scheme is applied on both DVB models for AWGN channel and various S NR values. The obtained results reveal that the proposed scheme has a good performance for ten secondary users and low SNR.

One of the complex problems nowadays in communication systems is the lack of frequency spectrum. To solve this problem, cognitive radio is considered the best candidate that can opportunistically exploit the spectrum. The periodogram based spectrum sensing technique can be used to detect the spectrum in cognitive radio. It is a useful technique since does not need to prior information about the primary signal. In this paper, a new periodogram is presented using the Discrete Cosine Transform (DCT). Results are analyzed and compared with the current raw periodogram. It is observed that the DCT periodogram outperforms the raw technique in terms of probabilities of false alarm and detection, variance, and complexity. In addition, the lowest power of DCT coefficients can be removed without compromising the sensing performance. The proposed system shows high probability of detection with low probability of false alarm even in the case of low Signal-to-Noise Ratio (SNR).

We investigate the nonlinear effect of a planar superconducting metamaterial made from niobium nitride (NbN) at terahertz frequencies. As the variation of the incident intense terahertz field alters the intrinsic conductivity in the NbN, a consequent giant amplitude modulation is observed due to the strong nonlinearities. The high sensitivity of the chosen metamaterial even allows observing the nonlinear behaviors at various temperatures, but the resonance modulation induced by the nonlinear effect was distinct from that induced by the heating effect. The presented results illustrate a clever implementation of strongly enhanced nonlinearities and thus may bring nonlinear metamaterials into novel applications.

Absfracf -This paper describes a LINC (Linear Amplification using Nonlinear Components) handset transmitter adopting DC bias control. The power amplifier is operated at a saturated output power level and its level is adjusted by DC bias control. Thus the transmitter guarantees high efficiency at all usable output power level. Due to the LINC linearization, it can operate as a linear power amplifier. The new LINC transmitter can be used as a transmitter for software defined radio (SDR), since it can efficiently amplify both the GSM type constant envelope signal and CDMA type non-constant envelope signal, and its control part is very simple and mostly embodied in the digital domain. For verification, a 1.71 GHz LINC prototype transmitter has been implemented and tested. The results, compared with conventional cases, clearly show the suitability of the new LINC transmitter for SDR application.

Noise is one of the major challenges in the development of robust automatic speech recognition (ASR) System. There are several speech enhancement techniques available to reduce the effect of noise from speech signals. In this paper, a statistical analysis is presented on the impact of speech enhancement techniques on the feature vectors of noisy speech signals by estimating Bhattacharya distances (BD) from the feature vectors of approximately noise free training speech signals to the feature vectors of noisy testing speech signals. Here Sub-band Spectral Subtraction (SSS) and Frame Selection (FS) have been used as speech enhancement techniques at signal level and Cepstral Mean Normalization (CMN) has been used as feature normalization technique at feature level. In this research work, combination of Mel-Frequency Cepstral Coefficients (MFCC), Log energies, first time derivatives and second time derivatives of MFCCs and Log energies has been used as speech feature vectors. Speech rec...

In agglutinative languages, selection of lexical unit is not obvious. Morpheme unit is usually adopted to ensure the sufficient coverage, but many morphemes are short, resulting in weak constraints and possible confusions. In this paper, we propose a discriminative approach to select lexical entries which will directly contribute to ASR error reduction. We define an evaluation function for each word by a set of features and their weights, and the measure for optimization by the difference of WERs by the morphemebased model and by the word-based model. Then, the weights of the features are learned by a perceptron algorithm. Finally, word (or sub-word) entries with higher evaluation scores are selected to be added to the lexicon. This method is successfully applied to an Uyghur largevocabulary continuous speech recognition system, resulting in a significant reduction of WER and the lexicon size. Further improvement is achieved by combining with a statistical method based on mutual information criterion.

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Evaluasi dan visualisasi fungsi matematika seringkali menjadi proses yang memakan waktu dan kurang interaktif jika menggunakan metode konvensional. Hal ini dapat menjadi penghalang, terutama bagi pengguna yang tidak memiliki latar belakang teknis yang kuat. Proyek ini bertujuan untuk mengatasi masalah tersebut dengan mengembangkan sebuah "Kalkulator Fungsi" berbasis Graphical User Interface (GUI) menggunakan MATLAB. Metode yang digunakan adalah merancang antarmuka visual yang memungkinkan pengguna untuk memasukkan dua fungsi, f(x) dan g(x), kemudian melakukan berbagai operasi seperti penjumlahan, pengurangan, perkalian, pembagian, dan komposisi fungsi hanya dengan menekan tombol. Setiap tombol operasi dihubungkan dengan script MATLAB untuk melakukan perhitungan secara otomatis dan menampilkan hasilnya dalam bentuk grafik pada axes yang telah disediakan. Hasil akhir dari proyek ini adalah sebuah aplikasi yang fungsional dan ramah pengguna, yang berfungsi sebagai jembatan antara konsep matematika abstrak dengan representasi visual yang mudah dipahami. Kalkulator ini diharapkan dapat menjadi alat komputasi yang efisien sekaligus media pembelajaran yang memberdayakan pengguna untuk menjelajahi dunia fungsi secara lebih dinamis dan intuitif.

Measurements have been made, using acoustic presentation of stimuli, to compare a variety of speech-derived signals (amplitude envelope, voice fundamental frequency, secondformant frequency, zero-crossing frequency, and an "odotl" control derived from the amplitude envelope via a comparator) as to their suitability for tactile presentation to the profoundly deaf as an aid to speech reception. Segmental (phonemic) information was conveyed adequately by all five signals; suprasegmental (stress) information was conveyed very well by voice fundamental frequency, and significantly less well by the other signals. The best choice of speech features for presentation via a practical tactile aid is discussed.

The existence of amplitude-modulation (AM) frequency-specific channels has previously been suggested on the basis of psychoacoustical experiments using an adaptation or masking paradigm. Electrophysiological studies have also shown that cochlear nucleus chop-s neurons are tuned to specilic AM frequencies. We have developed a simple but physiologically plausible model of chop-S neuron properties based on a digital integration of Hodgkin and Hwdey equations. Although it does not include an exhaustive peripheral processing, our model produces similar results to physiological data. We recover a bandpass AM transfer fimction at high input levels and non-linear atering. This model enables us to simulate physiological masking situations in the modulation domain. We examine the strength of the model synchronous response to white noises modulated at two dserent frequencies and added with various intensity ratios. Simulations show that the chop-S model enhances AM separation of a well-tuned AM frequency added to another, relative to the auditory-nerve fibers inputs. Masking patterns computed by varying the masker-modulation fiequencies show the recruitment of the neuron by these stimuli.

New wireless subscribers are signing up at an increasing demand of more capacity for ultra-high data rate transfers at speeds more than 1 Gbps, while the radio spectrum is limited. Millimeter wave communication system offers a unique way to resolve these problems. In this paper, the performance of a full duplex transportation system is reported for 1.5 Km of multi-mode fiber length for a sample 10 Gbit/s pseudo random sequence data, with quadrature amplitude modulation mapping and orthogonal frequency division multiplexing modulation with 60 GHz RF and coherent 1550 nm optical carrier. The analysis and simulation results show that the system's quality of service depends on nonlinearity of electro optical modulator, dispersion and signal attenuation impairment of the multimode fiber cable.

The speech signal has been shown to contain a fine structure that consists of the fast changing spectral content (e.g., formant transitions, voicing, spectral energy distributions), together with amplitude modulations of the envelope with different timescales. These different modulation frequencies have been associated with linguistic units of different sizes, and neuronal oscillations seem to track this linguistic structure. As the amplitude envelope mostly captures suprasegmental information, the different modulation frequencies are natural candidates to convey prosodic information. In this paper we put these assumptions to the test by comparing effects of sentence length and language, focusing on languages with distinct prosodic profiles: Brazilian Portuguese (syllable-timed), European Portuguese (mixed rhythm, with syllable-timed and stress-timed properties), and German (stress-timed). There are further differences regarding the roles of the syllable, the foot, the prosodic word and the intonation phrase. We analyzed wideband amplitude envelopes using general additive mixed models and show that German differs from Brazilian Portuguese and European Portuguese in the delta (1-2Hz) and theta bands (6-8Hz). European and Brazilian Portuguese also differ, but only in the delta band (1-2Hz). The language differences in amplitude modulation are discussed in terms of speech rhythm and differences in prosodic structure across languages.

Gamma band response to visual stimulation in humans has been observed to have both burst and resonance properties. Amplitude modulation of gamma activity at low frequencies has been seen in rat hippocampus and modeled in a number of forms. Significant amplitude modulation ( p = 0.05) of 33 Hz gamma frequency activity at the frequency of an 8 1/3 Hz photic driving stimulus, which also produced strong alpha entrainment, was observed in 67% of the channels in 42 human subjects. Similar amplitude modulation was found at a range of frequencies from greater than 50 Hz to about 28 Hz. The peak of the gamma amplitude modulation curve trailed the peak of the alpha signal by 25 to 30 ms, corresponding to a phase difference of 150-to 180-. The phase consistency of the gamma signal, measured across comparable times of the alpha signal, was least at the minimum amplitude modulation, and largest at the maximum. Although there was no consistent overall relation between the gamma amplitude and alpha amplitude, peak gamma amplitude values were consistently higher during post-target-stimulus alpha suppression, which occurs about 300 -750 ms subsequent to stimulus presentation, than they were at the time of maximum alpha activity during the immediate post-stimulus period. It is hypothesized that there is an interaction between the alpha and gamma generating systems, in which gamma triggers alpha activity and is subsequently inhibited by it, thus producing the observed amplitude modulation. The transition from dark to light of the photic driving stimulus begins a phase resetting process in the gamma system and a concomitant burst of gamma activity; this produces an activation in the alpha system, similar to that found in the P1 -N1 response in evoked potential experiments, and a subsequent inhibition of gamma production.

The stabilization of lasers on ultra-stable optical cavities by the Pound-Drever-Hall (PDH) technique is a widely used method. The PDH method relies on the phase-modulation of the laser, which is usually performed by an electro-optic modulator (EOM). When approaching the $10^{-16}$ level, this technology requires an active control of the residual amplitude modulation (RAM) generated by the EOM in order to bring the frequency stability of the laser down to the thermal noise limit of the ultra-stable cavity. In this article, we report on the development of an active system of RAM reduction based on a free space EOM, which is used to perform PDH-stabilization of a laser on a cryogenic silicon cavity. A RAM stability of $1.4 \times 10^{-7}$ is obtained by employing a digital servo that stabilizes the EOM DC electric field, the crystal temperature and the laser power. Considering an ultra-stable cavity with a finesse of $2.5\times 10^5$, this RAM level would contribute to the fractional frequency instability at the level of about $5\times 10^{-19}$, well below the state of the art thermal noise limit of a few $ 10^{-17}$.

Three copolymers, PFTpBt, PFbCNTpBt, and PFC6TpBt, which are based on dioctylfluorene, dithienylbenzothiadiazole, and thiophene derivatives with different functional groups, were synthesized via a Suzuki reaction. The copolymers were characterized by NMR, GPC, TGA, UV-vis absorption, and electrochemical cyclic voltammetry. Thermogravimetric analysis showed that the copolymers exhibited good thermal stability. The optical, electrochemical, photovoltaic properties, and hole mobility of the copolymers were investigated and discussed. The polymer solar cell based on PFTpBt had the best performance, with a power conversion efficiency (PCE) of 2.17% under the illumination of AM 1.5, 100 mW/cm 2 .

Audio watermarking is a technique, which can be used to embed information into the digital representation of audio signals. The main challenge is to hide data representing some information without compromising the quality of the watermarked track and at the same time ensure that the embedded watermark is robust against removal attacks. Especially providing perfect audio quality combined with high robustness against a wide variety of attacks is not adequately addressed and evaluated in current watermarking systems. In this paper, we present a new phase modulation audio watermarking technique, which among other features provides evidence for high audio quality. PSK modulation has been proposed as an effective approach to watermarking.

A new construction of spherepackings using codes is given, which covers the construction of Leech and Sloane . The dense packings of Sloane [10] are also obtained here, but without the use of complex numbers. Several new records on the packing desity in high dimensions are given. In the second part of this paper three new alternatives of a construction, which leads to the Leech lattice . 24 i ~n lR , are g ven.

The High-flux Advanced Neutron Application Reactor (HANARO) has the equipment to treat the gaseous radioactive waste generated within itself but it does not have proper ways to treat the waste in either a liquid or solid form. For the last 5 years, every effort has been made to reduce the radioactive wastes in HANARO. Improvements of the equipment and operating procedures regarding the generation of radioactive waste in the field have resulted in an effective reduction of the radioactive waste. In addition, as an outgrowth of the research efforts in connection with the demand in the field, several new methods have been developed to effectively treat the radioactive waste. Efforts to reduce and treat the radioactive waste in HANARO will continue and that will contribute greatly to an improvement of the reliability and safety of HANARO.

This chapter look in to the way the Inter- symbol interference (ISI) has a significant challenge in communication systems, which adversely affect the data integrity and transmission efficiency. ISI arises majorly due to scattering nature of communication channels, where symbols overlap and collide with one another, thereby resulting to errors in signal detection. This phenomenon arises to be particularly pronounced in high-speed data transmission systems in which environments with multiples of propagation in involved such as wireless communication. A myriad of equalization techniques, not limited to Zero-forcing (ZF), Minimum Mean Square Error (MMSE), and Least Mean Square (LMS) adaptive equalizers, have been developed and refined over decades to mitigate ISI. Furthermore, this literature reviews delves much in to the principles, design methodologies and the performance of these equalizers based on recent researchers.

Of all the Cuban reptile species, lizards have the greatest richness and diversity. Among them, little is known about the natural history of the species of the genus Diploglossus, so that studies on their ecological niche would provide relevant and novel information about their ecology. Because of that, we proposed to characterize the climatically suitable areas of D. delasagra and D. nigropunctatus and to evaluate the niche overlap between them. We compiled information from 123 georeferenced presence records. Bioclimatic variables of WorldClim were used as predictive variables for the generation of ecological niche models in Maxent program. The final averaged models were binarized to generate presence-absence maps with the ArcGis program. The models obtained were evaluated as useful and excellent according to the difference between the training and testing AUC values, reflecting their high predictive capacity. The contribution of the variables to the resulting models varied between the two species, and in both cases the variables derived from temperature were those with the greatest contribution. The climatically suitable areas completely included the areas of known presence and included other areas. The potential distribution areas of the climate niche for both species showed very different distribution patterns, being higher for D. delasagra (221 123.84 km 2) and smaller for D. nigropunctatus (6 173.82 km 2). The Principal Components Analysis showed a very low niche overlap between the species, being D. delasagra the one with the greatest ecological plasticity and D. nigropunctatus the one with the least, the latter with preference of environments with lower values of seasonality in temperatures and a regime of abundant rainfall all year. The ecological niche breadth was also described using the B1 index in the ENMTools program, and the position and amplitude of the niche along the climatic axes. The Discriminant Analysis showed 95.24% of correct classifications, so there is no overlap between the ecological niches of both species. In conclusion, D. delasagra presents a wide distribution with respect to D. nigropunctatus, restricted to the main mountainous massifs of the east of Cuba, and both niches differ in environmental requirements and amplitude, defined by different variables. Research article Volume 2 Issue 3

Due to normal friction and wear, even in properly lubricated moving machine elements, it is not uncommon to find small amounts of debris in used lubricants. The wear debris analysis technique has been applied for monitoring machine condition for quite sometimes. However, most of the works reported to date have been focussed for oil - lubricated machinery. Actually, very little primary material of the application of used grease analysis technique for plain bearings is to be found in the periodical literature. The identification of the cause of damage or failure in plain bearings is crucial before remedial action can be taken to prevent further. The first step is a visual examination of the wear debris and/ or contaminants suspended in the used grease samples. In addition, this step can then be followed up by visualization of the damaged parts, if applicable. Once failure has been initiated, the origin mechanism may lead to other failure mechanisms and it is essential to identify the ...

Bonang can be played simultaneously on the same two-tone one octave apart, so it appears the phenomenon of superposition. To observe the differences in superposition waveform and spectrum of various timbres of bonang barung, the audacity software was employed. It is used to record and analyse the sound bonang barung, and MATLAB software to process data from the time domain to the frequency domain. The object of research is a set pelog bonang barung Gending Bahana made of iron. The research was conducted by recording of bonang barung sounds using software audacity. Pencon bonang barungs were beaten separately and simultaneously. The recorded sound of bonang barung that is beaten separately then mixed with mix and rendering facilities in audacity. Then the recorded sounds analyzed by spectral plots for producing the fundamental and harmonic frequencies. Besides analyzed with analysis menu on audacity, recordings of sound bonang barung can be analyzed with FFT program in MATLAB software. The results showed that comparison of the results of mix and simultaneous superposition with audacity percentage ranged from 0% to 2%, while the comparison of the results of superposition analysis with MATLAB program on the percentage ranged from 0% to 0,4%. Superposition results obtained from the mix and simultaneous value remained at almost the same range. So that when struck, mix and simultaneous superposition result will sound the same by those who hear it because of the frequency and the amplitude is almost as though there is a phase difference.