Improvement in QEPAS system utilizing a second harmonic based wavelength calibration technique

NASA Astrophysics Data System (ADS)

Zhang, Qinduan; Chang, Jun; Wang, Fupeng; Wang, Zongliang; Xie, Yulei; Gong, Weihua

2018-05-01

A simple laser wavelength calibration technique, based on second harmonic signal, is demonstrated in this paper to improve the performance of quartz enhanced photoacoustic spectroscopy (QEPAS) gas sensing system, e.g. improving the signal to noise ratio (SNR), detection limit and long-term stability. Constant current, corresponding to the gas absorption line, combining f/2 frequency sinusoidal signal are used to drive the laser (constant driving mode), a software based real-time wavelength calibration technique is developed to eliminate the wavelength drift due to ambient fluctuations. Compared to conventional wavelength modulation spectroscopy (WMS), this method allows lower filtering bandwidth and averaging algorithm applied to QEPAS system, improving SNR and detection limit. In addition, the real-time wavelength calibration technique guarantees the laser output is modulated steadily at gas absorption line. Water vapor is chosen as an objective gas to evaluate its performance compared to constant driving mode and conventional WMS system. The water vapor sensor was designed insensitive to the incoherent external acoustic noise by the numerical averaging technique. As a result, the SNR increases 12.87 times in wavelength calibration technique based system compared to conventional WMS system. The new system achieved a better linear response (R2 = 0 . 9995) in concentration range from 300 to 2000 ppmv, and achieved a minimum detection limit (MDL) of 630 ppbv.

Harmonic motion detection in a vibrating scattering medium.

PubMed

Urban, Matthew W; Chen, Shigao; Greenleaf, James

2008-09-01

Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating scattering medium incorporating 3-D beam shapes for radiation force excitation and motion tracking. A parameterized analysis using this model provides a platform to optimize motion detection for vibrometry applications in tissue. An experimental method that produces a multifrequency radiation force is also presented. Experimental harmonic motion detection of simultaneous multifrequency vibration is demonstrated using a single transducer. This method can accurately detect motion with displacement amplitude as low as 100 to 200 nm in bovine muscle. Vibration phase can be measured within 10 degrees or less. The experimental results validate the conclusions observed from the model and show multifrequency vibration induction and measurements can be performed simultaneously.

Harmonic mode-locking using the double interval technique in quantum dot lasers.

PubMed

Li, Yan; Chiragh, Furqan L; Xin, Yong-Chun; Lin, Chang-Yi; Kim, Junghoon; Christodoulou, Christos G; Lester, Luke F

2010-07-05

Passive harmonic mode-locking in a quantum dot laser is realized using the double interval technique, which uses two separate absorbers to stimulate a specific higher-order repetition rate compared to the fundamental. Operating alone these absorbers would otherwise reinforce lower harmonic frequencies, but by operating together they produce the harmonic corresponding to their least common multiple. Mode-locking at a nominal 60 GHz repetition rate, which is the 10(th) harmonic of the fundamental frequency of the device, is achieved unambiguously despite the constraint of a uniformly-segmented, multi-section device layout. The diversity of repetition rates available with this method is also discussed.

Detectability of Halyomorpha Halys (Hemiptera: Pentatomidae) by portable harmonic radar in agricultural landscapes

USDA-ARS?s Scientific Manuscript database

Harmonic radar has provided a new approach to individually track movement of small insects under field conditions. In a series of studies, we developed methods to improve durability of harmonic radar tags attached to insects and established the efficacy of a portable harmonic radar system at detect...

Harmonic Motion Detection in a Vibrating Scattering Medium

PubMed Central

Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.

2008-01-01

Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional accuracy. This paper presents a model that simulates harmonic motion detection in a vibrating scattering medium incorporating 3-D beam shapes for radiation force excitation and motion tracking. A parameterized analysis using this model provides a platform to optimize motion detection for vibrometry applications in tissue. An experimental method that produces a multifrequency radiation force is also presented. Experimental harmonic motion detection of simultaneous multifrequency vibration is demonstrated using a single transducer. This method can accurately detect motion with displacement amplitude as low as 100 to 200 nm in bovine muscle. Vibration phase can be measured within 10° or less. The experimental results validate the conclusions observed from the model and show multifrequency vibration induction and measurements can be performed simultaneously. PMID:18986892

Harmonic versus LigaSure hemostasis technique in thyroid surgery: A meta-analysis

PubMed Central

Upadhyaya, Arun; Hu, Tianpeng; Meng, Zhaowei; Li, Xue; He, Xianghui; Tian, Weijun; Jia, Qiang; Tan, Jian

2016-01-01

Harmonic scalpel and LigaSure vessel sealing systems have been suggested as options for saving surgical time and reducing postoperative complications. The aim of the present meta-analysis was to compare surgical time, postoperative complications and other parameters between them in for the open thyroidectomy procedure. Studies were retrieved from MEDLINE, Cochrane Library, EMBASE and ISI Web of Science until December 2015. All the randomized controlled trials (RCTs) comparing Harmonic scalpel and LigaSure during open thyroidectomy were selected. Following data extraction, statistical analyses were performed. Among the 24 studies that were evaluated for eligibility, 7 RCTs with 981 patients were included. The Harmonic scalpel significantly reduced surgical time compared with LigaSure techniques (8.79 min; 95% confidence interval, −15.91 to −1.67; P=0.02). However, no significant difference was observed for the intraoperative blood loss, postoperative blood loss, duration of hospital stay, thyroid weight and serum calcium level postoperatively in either group. The present meta-analysis indicated superiority of Harmonic Scalpel only in terms of surgical time compared with LigaSure hemostasis techniques in open thyroid surgery. PMID:27446546

Conditional Anomaly Detection with Soft Harmonic Functions.

PubMed

Valko, Michal; Kveton, Branislav; Valizadegan, Hamed; Cooper, Gregory F; Hauskrecht, Milos

2011-01-01

In this paper, we consider the problem of conditional anomaly detection that aims to identify data instances with an unusual response or a class label. We develop a new non-parametric approach for conditional anomaly detection based on the soft harmonic solution, with which we estimate the confidence of the label to detect anomalous mislabeling. We further regularize the solution to avoid the detection of isolated examples and examples on the boundary of the distribution support. We demonstrate the efficacy of the proposed method on several synthetic and UCI ML datasets in detecting unusual labels when compared to several baseline approaches. We also evaluate the performance of our method on a real-world electronic health record dataset where we seek to identify unusual patient-management decisions.

Harmonic vibro-acoustography.

PubMed

Chen, Shigao; Kinnick, Randall R; Greenleaf, James F; Fatemi, Mostafa

2007-07-01

Vibro-acoustography is an imaging method that uses the radiation force of two interfering ultrasound beams of slightly different frequency to probe an object. An image is made using the acoustic emission resulted from the object vibration at the difference frequency. In this paper, the feasibility of imaging objects at twice the difference frequency (harmonic acoustic emission) is studied. Several possible origins of harmonic acoustic emission are explored. As an example, it is shown that microbubbles close to resonance can produce significant harmonic acoustic emission due to its high nonlinearity. Experiments demonstrate that, compared to the fundamental acoustic emission, harmonic acoustic emission greatly improves the contrast between microbubbles and other objects in vibro-acoustography (an improvement of 17-23 dB in these experiments). Applications of this technique include imaging the nonlinearity of the object and selective detection of microbubbles for perfusion imaging. The impact of microbubble destruction during the imaging process also is discussed.

Conditional Anomaly Detection with Soft Harmonic Functions

PubMed Central

Valko, Michal; Kveton, Branislav; Valizadegan, Hamed; Cooper, Gregory F.; Hauskrecht, Milos

2012-01-01

In this paper, we consider the problem of conditional anomaly detection that aims to identify data instances with an unusual response or a class label. We develop a new non-parametric approach for conditional anomaly detection based on the soft harmonic solution, with which we estimate the confidence of the label to detect anomalous mislabeling. We further regularize the solution to avoid the detection of isolated examples and examples on the boundary of the distribution support. We demonstrate the efficacy of the proposed method on several synthetic and UCI ML datasets in detecting unusual labels when compared to several baseline approaches. We also evaluate the performance of our method on a real-world electronic health record dataset where we seek to identify unusual patient-management decisions. PMID:25309142

Compressive Sensing of Roller Bearing Faults via Harmonic Detection from Under-Sampled Vibration Signals

PubMed Central

Tang, Gang; Hou, Wei; Wang, Huaqing; Luo, Ganggang; Ma, Jianwei

2015-01-01

The Shannon sampling principle requires substantial amounts of data to ensure the accuracy of on-line monitoring of roller bearing fault signals. Challenges are often encountered as a result of the cumbersome data monitoring, thus a novel method focused on compressed vibration signals for detecting roller bearing faults is developed in this study. Considering that harmonics often represent the fault characteristic frequencies in vibration signals, a compressive sensing frame of characteristic harmonics is proposed to detect bearing faults. A compressed vibration signal is first acquired from a sensing matrix with information preserved through a well-designed sampling strategy. A reconstruction process of the under-sampled vibration signal is then pursued as attempts are conducted to detect the characteristic harmonics from sparse measurements through a compressive matching pursuit strategy. In the proposed method bearing fault features depend on the existence of characteristic harmonics, as typically detected directly from compressed data far before reconstruction completion. The process of sampling and detection may then be performed simultaneously without complete recovery of the under-sampled signals. The effectiveness of the proposed method is validated by simulations and experiments. PMID:26473858

A coherent detection technique via optically biased field for broadband terahertz radiation.

PubMed

Du, Hai-Wei; Dong, Jia-Meng; Liu, Yi; Shi, Chang-Cheng; Wu, Jing-Wei; Peng, Xiao-Yu

2017-09-01

We demonstrate theoretically and experimentally a coherent terahertz detection technique based on an optically biased field functioning as a local oscillator and a second harmonic induced by the terahertz electric field in the air sensor working in free space. After optimizing the polarization angle and the energy of the probe pulse, and filling the system with dry nitrogen, the terahertz radiation generated from a two-color-femtosecond-laser-pulses induced plasma filament is measured by this technique with a bandwidth of 0.1-10 THz and a signal-to-noise ratio of 48 dB. Our technique provides an alternative simple method for coherent broadband terahertz detection.

A Kalman Filter Based Technique for Stator Turn-Fault Detection of the Induction Motors

NASA Astrophysics Data System (ADS)

Ghanbari, Teymoor; Samet, Haidar

2017-11-01

Monitoring of the Induction Motors (IMs) through stator current for different faults diagnosis has considerable economic and technical advantages in comparison with the other techniques in this content. Among different faults of an IM, stator and bearing faults are more probable types, which can be detected by analyzing signatures of the stator currents. One of the most reliable indicators for fault detection of IMs is lower sidebands of power frequency in the stator currents. This paper deals with a novel simple technique for detecting stator turn-fault of the IMs. Frequencies of the lower sidebands are determined using the motor specifications and their amplitudes are estimated by a Kalman Filter (KF). Instantaneous Total Harmonic Distortion (ITHD) of these harmonics is calculated. Since variation of the ITHD for the three-phase currents is considerable in case of stator turn-fault, the fault can be detected using this criterion, confidently. Different simulation results verify high performance of the proposed method. The performance of the method is also confirmed using some experiments.

Analysis of biochemical phase shift oscillators by a harmonic balancing technique.

PubMed

Rapp, P

1976-11-25

The use of harmonic balancing techniques for theoretically investigating a large class of biochemical phase shift oscillators is outlined and the accuracy of this approximate technique for large dimension nonlinear chemical systems is considered. It is concluded that for the equations under study these techniques can be successfully employed to both find periodic solutions and to indicate those cases which can not oscillate. The technique is a general one and it is possible to state a step by step procedure for its application. It has a substantial advantage in producing results which are immediately valid for arbitrary dimension. As the accuracy of the method increases with dimension, it complements classical small dimension methods. The results obtained by harmonic balancing analysis are compared with those obtained by studying the local stability properties of the singular points of the differential equation. A general theorem is derived which identifies those special cases where the results of first order harmonic balancing are identical to those of local stability analysis, and a necessary condition for this equivalence is derived. As a concrete example, the n-dimensional Goodwin oscillator is considered where p, the Hill coefficient of the feedback metabolite, is equal to three and four. It is shown that for p = 3 or 4 and n less than or equal to 4 the approximation indicates that it is impossible to construct a set of physically permissible reaction constants such that the system possesses a periodic solution. However for n greater than or equal to 5 it is always possible to find a large domain in the reaction constant space giving stable oscillations. A means of constructing such a parameter set is given. The results obtained here are compared with previously derived results for p = 1 and p = 2.

Harmonic component detection: Optimized Spectral Kurtosis for operational modal analysis

NASA Astrophysics Data System (ADS)

Dion, J.-L.; Tawfiq, I.; Chevallier, G.

2012-01-01

This work is a contribution in the field of Operational Modal Analysis to identify the modal parameters of mechanical structures using only measured responses. The study deals with structural responses coupled with harmonic components amplitude and frequency modulated in a short range, a common combination for mechanical systems with engines and other rotating machines in operation. These harmonic components generate misleading data interpreted erroneously by the classical methods used in OMA. The present work attempts to differentiate maxima in spectra stemming from harmonic components and structural modes. The detection method proposed is based on the so-called Optimized Spectral Kurtosis and compared with others definitions of Spectral Kurtosis described in the literature. After a parametric study of the method, a critical study is performed on numerical simulations and then on an experimental structure in operation in order to assess the method's performance.

Improved Shear Wave Motion Detection Using Pulse-Inversion Harmonic Imaging with a Phased Array Transducer

PubMed Central

Song, Pengfei; Zhao, Heng; Urban, Matthew W.; Manduca, Armando; Pislaru, Sorin V.; Kinnick, Randall R.; Pislaru, Cristina; Greenleaf, James F.; Chen, Shigao

2013-01-01

Ultrasound tissue harmonic imaging is widely used to improve ultrasound B-mode imaging quality thanks to its effectiveness in suppressing imaging artifacts associated with ultrasound reverberation, phase aberration, and clutter noise. In ultrasound shear wave elastography (SWE), because the shear wave motion signal is extracted from the ultrasound signal, these noise sources can significantly deteriorate the shear wave motion tracking process and consequently result in noisy and biased shear wave motion detection. This situation is exacerbated in in vivo SWE applications such as heart, liver, and kidney. This paper, therefore, investigated the possibility of implementing harmonic imaging, specifically pulse-inversion harmonic imaging, in shear wave tracking, with the hypothesis that harmonic imaging can improve shear wave motion detection based on the same principles that apply to general harmonic B-mode imaging. We first designed an experiment with a gelatin phantom covered by an excised piece of pork belly and show that harmonic imaging can significantly improve shear wave motion detection by producing less underestimated shear wave motion and more consistent shear wave speed measurements than fundamental imaging. Then, a transthoracic heart experiment on a freshly sacrificed pig showed that harmonic imaging could robustly track the shear wave motion and give consistent shear wave speed measurements while fundamental imaging could not. Finally, an in vivo transthoracic study of seven healthy volunteers showed that the proposed harmonic imaging tracking sequence could provide consistent estimates of the left ventricular myocardium stiffness in end-diastole with a general success rate of 80% and a success rate of 93.3% when excluding the subject with Body Mass Index (BMI) higher than 25. These promising results indicate that pulse-inversion harmonic imaging can significantly improve shear wave motion tracking and thus potentially facilitate more robust assessment

Imaging of targeted lipid microbubbles to detect cancer cells using third harmonic generation microscopy

PubMed Central

Harpel, Kaitlin; Baker, Robert Dawson; Amirsolaimani, Babak; Mehravar, Soroush; Vagner, Josef; Matsunaga, Terry O.; Banerjee, Bhaskar; Kieu, Khanh

2016-01-01

The use of receptor-targeted lipid microbubbles imaged by ultrasound is an innovative method of detecting and localizing disease. However, since ultrasound requires a medium between the transducer and the object being imaged, it is impractical to apply to an exposed surface in a surgical setting where sterile fields need be maintained and ultrasound gel may cause the bubbles to collapse. Multiphoton microscopy (MPM) is an emerging tool for accurate, label-free imaging of tissues and cells with high resolution and contrast. We have recently determined a novel application of MPM to be used for detecting targeted microbubble adherence to the upregulated plectin-receptor on pancreatic tumor cells. Specifically, the third-harmonic generation response can be used to detect bound microbubbles to various cell types presenting MPM as an alternative and useful imaging method. This is an interesting technique that can potentially be translated as a diagnostic tool for the early detection of cancer and inflammatory disorders. PMID:27446711

Adaptive Harmonic Detection Control of Grid Interfaced Solar Photovoltaic Energy System with Power Quality Improvement

NASA Astrophysics Data System (ADS)

Singh, B.; Goel, S.

2015-03-01

This paper presents a grid interfaced solar photovoltaic (SPV) energy system with a novel adaptive harmonic detection control for power quality improvement at ac mains under balanced as well as unbalanced and distorted supply conditions. The SPV energy system is capable of compensation of linear and nonlinear loads with the objectives of load balancing, harmonics elimination, power factor correction and terminal voltage regulation. The proposed control increases the utilization of PV infrastructure and brings down its effective cost due to its other benefits. The adaptive harmonic detection control algorithm is used to detect the fundamental active power component of load currents which are subsequently used for reference source currents estimation. An instantaneous symmetrical component theory is used to obtain instantaneous positive sequence point of common coupling (PCC) voltages which are used to derive inphase and quadrature phase voltage templates. The proposed grid interfaced PV energy system is modelled and simulated in MATLAB Simulink and its performance is verified under various operating conditions.

Modified ADALINE algorithm for harmonic estimation and selective harmonic elimination in inverters

NASA Astrophysics Data System (ADS)

Vasumathi, B.; Moorthi, S.

2011-11-01

In digital signal processing, algorithms are very well developed for the estimation of harmonic components. In power electronic applications, an objective like fast response of a system is of primary importance. An effective method for the estimation of instantaneous harmonic components, along with conventional harmonic elimination technique, is presented in this article. The primary function is to eliminate undesirable higher harmonic components from the selected signal (current or voltage) and it requires only the knowledge of the frequency of the component to be eliminated. A signal processing technique using modified ADALINE algorithm has been proposed for harmonic estimation. The proposed method stays effective as it converges to a minimum error and brings out a finer estimation. A conventional control based on pulse width modulation for selective harmonic elimination is used to eliminate harmonic components after its estimation. This method can be applied to a wide range of equipment. The validity of the proposed method to estimate and eliminate voltage harmonics is proved with a dc/ac inverter as a simulation example. Then, the results are compared with existing ADALINE algorithm for illustrating its effectiveness.

Fluid Properties Measurements Using Wavelength Modulation Spectroscopy with First Harmonic Detection

NASA Technical Reports Server (NTRS)

Silver, Joel A. (Inventor); Chen, Shin-Juh (Inventor)

2014-01-01

An apparatus and method for monitoring gas velocity, temperature, and pressure in combustion systems and flow devices, in particular at inlets and isolators of scramjet engines. The invention employs wavelength modulation spectroscopy with first harmonic detection and without the need to scan the full absorption spectra.

High resolution subsurface imaging using resonance-enhanced detection in 2nd-harmonic KPFM.

PubMed

Cadena, Maria Jose; Reifenberger, Ronald G; Raman, Arvind

2018-06-28

Second harmonic Kelvin probe force microscopy is a robust mechanism for subsurface imaging at the nanoscale. Here we exploit resonance-enhanced detection as a way to boost the subsurface contrast with higher force sensitivity using lower bias voltages, in comparison to the traditional off-resonance case. In this mode, the second harmonic signal of the electrostatic force is acquired at one of the eigenmode frequencies of the microcantilever. As a result, high-resolution subsurface images are obtained in a variety of nanocomposites. To further understand the subsurface imaging detection upon electrostatic forces, we use a finite element model that approximates the geometry of the probe and sample. This allows the investigation of the contrast mechanism, the depth sensitivity and lateral resolution depending on tip-sample properties. © 2018 IOP Publishing Ltd.

Spherical Harmonic Inductive Detection Coils and their use In Dynamic Pre-emphasis for Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Edler, Karl T.

The issue of eddy currents induced by the rapid switching of magnetic field gradients is a long-standing problem in magnetic resonance imaging. A new method for dealing with this problem is presented whereby spatial harmonic components of the magnetic field are continuously sensed, through their temporal rates of change, and corrected. In this way, the effects of the eddy currents on multiple spatial harmonic components of the magnetic field can be detected and corrections applied during the rise time of the gradients. Sensing the temporal changes in each spatial harmonic is made possible with specially designed detection coils. However to make the design of these coils possible, general relationships between the spatial harmonics of the field, scalar potential, and vector potential are found within the quasi-static approximation. These relationships allow the vector potential to be found from the field -- an inverse curl operation -- and may be of use beyond the specific problem of detection coil design. Using the detection coils as sensors, methods are developed for designing a negative feedback system to control the eddy current effects and optimizing that system with respect to image noise and distortion. The design methods are successfully tested in a series of proof-of-principle experiments which lead to a discussion of how to incorporate similar designs into an operational MRI. Keywords: magnetic resonance imaging, eddy currents, dynamic shimming, negative feedback, quasi-static fields, vector potential, inverse curl

Imaging with Second-Harmonic Generation Nanoparticles

NASA Astrophysics Data System (ADS)

Hsieh, Chia-Lung

Second-harmonic generation nanoparticles show promise as imaging probes due to their coherent and stable signal with a broad flexibility in the choice of excitation wavelength. In this thesis, we developed and demonstrated barium titanate nanoparticles as second-harmonic radiation imaging probes. We studied the absolute second-harmonic generation efficiency of the nanoparticles on single-particle level. The polarization dependent second-harmonic signal of single nanoparticles was studied in detail. From the measured polar response, we were able to find the orientation of the nanoparticle. We developed a biochemical interface for using the second-harmonic nanoprobes as biomarkers, including in vitro cellular imaging and in vivo live animal imaging. The nanoparticles were surface functionalized with primary amine groups for stable colloidal dispersion. We achieved specific labeling of the second-harmonic nanoprobes via immunostaining where the antibodies were covalently conjugated onto the nanoparticles. We observed no toxicity of the functionalized nanoparticles to biological cells. The coherent second-harmonic signal radiated from the nanoparticles offers opportunities for new imaging techniques. Using interferometric detection, namely harmonic holography, both amplitude and phase of the second-harmonic field can be captured. Through digital beam propagation, three-dimensional field distribution, reflecting three-dimensional distribution of the nanoparticles, can be reconstructed. We achieved a scan-free three-dimensional imaging of nanoparticles in biological cells with sub-micron spatial resolution by using the harmonic holographic microscope. We further exploited the coherent second-harmonic signal for imaging through scattering media by performing optical phase conjugation of the second-harmonic signal. We demonstrated an all-digital optical phase conjugation of the second-harmonic signal originated from a nanoparticle by combining harmonic holography and

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Higher spatial harmonics of photorefractive gratings written by phase-locked detection

NASA Astrophysics Data System (ADS)

Dugin, A. V.; Zel'dovich, Boris Ya; Il'inykh, P. N.; Liberman, V. S.; Nesterkin, O. P.

1992-11-01

The higher spatial harmonics of the photorefractive response have been studied theoretically and experimentally for gratings written by phase-locked detection in an alternating external field. The conditions for writing higher spatial harmonics are derived analytically. The amplitude of the second spatial harmonic has been found experimentally as a function of the spatial frequency in two Bi12TiO20 crystals.

Harmonic analysis and FPGA implementation of SHE controlled three phase CHB 11-level inverter in MV drives using deterministic and stochastic optimization techniques.

PubMed

Vesapogu, Joshi Manohar; Peddakotla, Sujatha; Kuppa, Seetha Rama Anjaneyulu

2013-01-01

With the advancements in semiconductor technology, high power medium voltage (MV) Drives are extensively used in numerous industrial applications. Challenging technical requirements of MV Drives is to control multilevel inverter (MLI) with less Total harmonic distortion (%THD) which satisfies IEEE standard 519-1992 harmonic guidelines and less switching losses. Among all modulation control strategies for MLI, Selective harmonic elimination (SHE) technique is one of the traditionally preferred modulation control technique at fundamental switching frequency with better harmonic profile. On the other hand, the equations which are formed by SHE technique are highly non-linear in nature, may exist multiple, single or even no solution at particular modulation index (MI). However, in some MV Drive applications, it is required to operate over a range of MI. Providing analytical solutions for SHE equations during the whole range of MI from 0 to 1, has been a challenging task for researchers. In this paper, an attempt is made to solve SHE equations by using deterministic and stochastic optimization methods and comparative harmonic analysis has been carried out. An effective algorithm which minimizes %THD with less computational effort among all optimization algorithms has been presented. To validate the effectiveness of proposed MPSO technique, an experiment is carried out on a low power proto type of three phase CHB 11- level Inverter using FPGA based Xilinx's Spartan -3A DSP Controller. The experimental results proved that MPSO technique has successfully solved SHE equations over all range of MI from 0 to 1, the %THD obtained over major range of MI also satisfies IEEE 519-1992 harmonic guidelines too.

Localized Harmonic Motion Imaging for Focused Ultrasound Surgery Targeting

PubMed Central

Curiel, Laura; Hynynen, Kullervo

2011-01-01

Recently, an in vivo real-time ultrasound-based monitoring technique that uses localized harmonic motion (LHM) to detect changes in tissues during focused ultrasound surgery (FUS) has been proposed to control the exposure. This technique can potentially be used as well for targeting imaging. In the present study we evaluated the potential of using LHM to detect changes in stiffness and the feasibility of using it for imaging purposes in phantoms and in vivo tumor detection. A single-element FUS transducer (80 mm focal length, 100 mm diameter, 1.485 MHz) was used for inducing a localized harmonic motion and a separate ultrasound diagnostic transducer excited by a pulser/receiver (5 kHz PRF, 5 MHz) was used to track motion. The motion was estimated using cross-correlation techniques on the acquired RF signal. Silicon phantom studies were performed in order to determine the size of inclusion that was possible to detect using this technique. Inclusions were discerned from the surroundings as a reduction on LHM amplitude and it was possible to depict inclusions as small as 4 mm. The amplitude of the induced LHM was always lower at the inclusions as compared with the one obtained at the surroundings. Ten New Zealand rabbits had VX2 tumors implanted on their thighs and LHM was induced and measured at the tumor region. Tumors (as small as 10 mm in length and 4 mm in width) were discerned from the surroundings as a reduction on LHM amplitude. PMID:21683514

Signal injection as a fault detection technique.

PubMed

Cusidó, Jordi; Romeral, Luis; Ortega, Juan Antonio; Garcia, Antoni; Riba, Jordi

2011-01-01

Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral analysis of stator current, is the most widely used method for identifying faults in induction motors. Motor faults such as broken rotor bars, bearing damage and eccentricity of the rotor axis can be detected. However, the method presents some problems at low speed and low torque, mainly due to the proximity between the frequencies to be detected and the small amplitude of the resulting harmonics. This paper proposes the injection of an additional voltage into the machine being tested at a frequency different from the fundamental one, and then studying the resulting harmonics around the new frequencies appearing due to the composition between injected and main frequencies.

Signal Injection as a Fault Detection Technique

PubMed Central

Cusidó, Jordi; Romeral, Luis; Ortega, Juan Antonio; Garcia, Antoni; Riba, Jordi

2011-01-01

Double frequency tests are used for evaluating stator windings and analyzing the temperature. Likewise, signal injection on induction machines is used on sensorless motor control fields to find out the rotor position. Motor Current Signature Analysis (MCSA), which focuses on the spectral analysis of stator current, is the most widely used method for identifying faults in induction motors. Motor faults such as broken rotor bars, bearing damage and eccentricity of the rotor axis can be detected. However, the method presents some problems at low speed and low torque, mainly due to the proximity between the frequencies to be detected and the small amplitude of the resulting harmonics. This paper proposes the injection of an additional voltage into the machine being tested at a frequency different from the fundamental one, and then studying the resulting harmonics around the new frequencies appearing due to the composition between injected and main frequencies. PMID:22163801

Improvement of Shear Wave Motion Detection Using Harmonic Imaging in Healthy Human Liver.

PubMed

Amador, Carolina; Song, Pengfei; Meixner, Duane D; Chen, Shigao; Urban, Matthew W

2016-05-01

Quantification of liver elasticity is a major application of shear wave elasticity imaging (SWEI) to non-invasive assessment of liver fibrosis stages. SWEI measurements can be highly affected by ultrasound image quality. Ultrasound harmonic imaging has exhibited a significant improvement in ultrasound image quality as well as for SWEI measurements. This was previously illustrated in cardiac SWEI. The purpose of this study was to evaluate liver shear wave particle displacement detection and shear wave velocity (SWV) measurements with fundamental and filter-based harmonic ultrasound imaging. In a cohort of 17 patients with no history of liver disease, a 2.9-fold increase in maximum shear wave displacement, a 0.11 m/s decrease in the overall interquartile range and median SWV and a 17.6% increase in the success rate of SWV measurements were obtained when filter-based harmonic imaging was used instead of fundamental imaging. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Degree of dispersion monitoring by ultrasonic transmission technique and excitation of the transducer's harmonics

NASA Astrophysics Data System (ADS)

Schober, G.; Heidemeyer, P.; Kretschmer, K.; Bastian, M.; Hochrein, T.

2014-05-01

The degree of dispersion of filled polymer compounds is an important quality parameter for various applications. For instance, there is an influence on the chroma in pigment colored plastics or on the mechanical properties of filled or reinforced compounds. Most of the commonly used offline methods are work-intensive and time-consuming. Moreover, they do not allow an all-over process monitoring. In contrast, the ultrasonic technique represents a suitable robust and process-capable inline method. Here, we present inline ultrasonic measurements on polymer melts with a fundamental frequency of 1 MHz during compounding. In order to extend the frequency range we additionally excite the fundamental and the odd harmonics vibrations at 3 and 5 MHz. The measurements were carried out on a compound consisting of polypropylene and calcium carbonate. For the simulation of agglomerates calcium carbonate with a larger particle size was added with various rates. The total filler content was kept constant. The frequency selective analysis shows a linear correlation between the normalized extinction and the rate of agglomerates simulated by the coarser filler. Further experiments with different types of glass beads with a well-defined particle size verify these results. A clear correlation between the normalized extinction and the glass bead size as well as a higher damping with increasing frequency corresponds to the theoretical assumption. In summary the dispersion quality can be monitored inline by the ultrasonic technique. The excitation of the ultrasonic transducer's harmonics generates more information about the material as the usage of the pure harmonic vibration.

Harmonic stochastic resonance-enhanced signal detecting in NW small-world neural network

NASA Astrophysics Data System (ADS)

Wang, Dao-Guang; Liang, Xiao-Ming; Wang, Jing; Yang, Cheng-Fang; Liu, Kai; Lü, Hua-Ping

2010-11-01

The harmonic stochastic resonance-enhanced signal detecting in Newman-Watts small-world neural network is studied using the Hodgkin-Huxley dynamical equation with noise. If the connection probability p, coupling strength gsyn and noise intensity D matches well, higher order resonance will be found and an optimal signal-to-noise ratio will be obtained. Then, the reasons are given to explain the mechanism of this appearance.

Generalized Wideband Harmonic Imaging of Nonlinearly Loaded Scatterers: Theory, Analysis, and Application for Forward-Looking Radar Target Detection

DTIC Science & Technology

2014-09-01

signal) operations; it is general enough so that it can accommodate high - power (large-signal) sensing as well—which may be needed to detect targets... Generalized Wideband Harmonic Imaging of Nonlinearly Loaded Scatterers: Theory, Analysis, and Application for Forward-Looking Radar Target...Research Laboratory Adelphi, MD 20783-1138 ARL-TR-7121 September 2014 Generalized Wideband Harmonic Imaging of Nonlinearly Loaded

Extracting harmonic signal from a chaotic background with local linear model

NASA Astrophysics Data System (ADS)

Li, Chenlong; Su, Liyun

2017-02-01

In this paper, the problems of blind detection and estimation of harmonic signal in strong chaotic background are analyzed, and new methods by using local linear (LL) model are put forward. The LL model has been exhaustively researched and successfully applied for fitting and forecasting chaotic signal in many chaotic fields. We enlarge the modeling capacity substantially. Firstly, we can predict the short-term chaotic signal and obtain the fitting error based on the LL model. Then we detect the frequencies from the fitting error by periodogram, a property on the fitting error is proposed which has not been addressed before, and this property ensures that the detected frequencies are similar to that of harmonic signal. Secondly, we establish a two-layer LL model to estimate the determinate harmonic signal in strong chaotic background. To estimate this simply and effectively, we develop an efficient backfitting algorithm to select and optimize the parameters that are hard to be exhaustively searched for. In the method, based on sensitivity to initial value of chaos motion, the minimum fitting error criterion is used as the objective function to get the estimation of the parameters of the two-layer LL model. Simulation shows that the two-layer LL model and its estimation technique have appreciable flexibility to model the determinate harmonic signal in different chaotic backgrounds (Lorenz, Henon and Mackey-Glass (M-G) equations). Specifically, the harmonic signal can be extracted well with low SNR and the developed background algorithm satisfies the condition of convergence in repeated 3-5 times.

Sensorless speed detection of squirrel-cage induction machines using stator neutral point voltage harmonics

NASA Astrophysics Data System (ADS)

Petrovic, Goran; Kilic, Tomislav; Terzic, Bozo

2009-04-01

In this paper a sensorless speed detection method of induction squirrel-cage machines is presented. This method is based on frequency determination of the stator neutral point voltage primary slot harmonic, which is dependent on rotor speed. In order to prove method in steady state and dynamic conditions the simulation and experimental study was carried out. For theoretical investigation the mathematical model of squirrel cage induction machines, which takes into consideration actual geometry and windings layout, is used. Speed-related harmonics that arise from rotor slotting are analyzed using digital signal processing and DFT algorithm with Hanning window. The performance of the method is demonstrated over a wide range of load conditions.

Determination of rotor harmonic blade loads from acoustic measurements

NASA Technical Reports Server (NTRS)

Kasper, P. K.

1975-01-01

The magnitude of discrete frequency sound radiated by a rotating blade is strongly influenced by the presence of a nonuniform distribution of aerodynamic forces over the rotor disk. An analytical development and experimental results are provided for a technique by which harmonic blade loads are derived from acoustic measurements. The technique relates, on a one-to-one basis, the discrete frequency sound harmonic amplitudes measured at a point on the axis of rotation to the blade-load harmonic amplitudes. This technique was applied to acoustic data from two helicopter types and from a series of test results using the NASA-Langley Research Center rotor test facility. The inferred blade-load harmonics for the cases considered tended to follow an inverse power law relationship with harmonic blade-load number. Empirical curve fits to the data showed the harmonic fall-off rate to be in the range of 6 to 9 db per octave of harmonic order. These empirical relationships were subsequently used as input data in a compatible far field rotational noise prediction model. A comparison between predicted and measured off-axis sound harmonic levels is provided for the experimental cases considered.

Harmonic Phase Response of Nonlinear Radar Targets

DTIC Science & Technology

2015-10-01

while allowing its harmonics to pass through. The weak harmonic responses are then amplified to allow for easier detection and measurement . 4...where the phase of the 2nd and 3rd harmonic of the received electromagnetic wave from nonlinear targets was measured and plotted against the frequency

High-frequency harmonic imaging of the eye.

PubMed

Silverman, Ronald H; Coleman, D Jackson; Ketterling, Jeffrey A; Lizzi, Frederic L

2005-01-01

PURPOSE: Harmonic imaging has become a well-established technique for ultrasonic imaging at fundamental frequencies of 10 MHz or less. Ophthalmology has benefited from the use of fundamentals of 20 MHz to 50 MHz. Our aim was to explore the ability to generate harmonics for this frequency range, and to generate harmonic images of the eye. METHODS: The presence of harmonics was determined in both water and bovine vitreous propagation media by pulse/echo and hydrophone at a series of increasing excitation pulse intensities and frequencies. Hydrophone measurements were made at the focal point and in the near- and far-fields of 20 MHz and 40 MHz transducers. Harmonic images of the anterior segment of the rabbit eye were obtained by a combination of analog filtering and digital post-processing. RESULTS: Harmonics were generated nearly identically in both water and vitreous. Hydrophone measurements showed the maximum second harmonic to be -5 dB relative to the 35 MHz fundamental at the focus, while in pulse/echo the maximum harmonic amplitude was -15dB relative to the fundamental. Harmonics were absent in the near-field, but present in the far-field. Harmonic images of the eye showed improved resolution. CONCLUSION: Harmonics can be readily generated at very high frequencies, and at power levels compliant with FDA guidelines for ophthalmology. This technique may yield further improvements to the already impressive resolutions obtainable in this frequency range. Improved imaging of the macular region, in particular, may provide significant improvements in diagnosis of retinal disease.

High-frequency harmonic imaging of the eye

NASA Astrophysics Data System (ADS)

Silverman, Ronald H.; Coleman, D. Jackson; Ketterling, Jeffrey A.; Lizzi, Frederic L.

2005-04-01

Purpose: Harmonic imaging has become a well-established technique for ultrasonic imaging at fundamental frequencies of 10 MHz or less. Ophthalmology has benefited from the use of fundamentals of 20 MHz to 50 MHz. Our aim was to explore the ability to generate harmonics for this frequency range, and to generate harmonic images of the eye. Methods: The presence of harmonics was determined in both water and bovine vitreous propagation media by pulse/echo and hydrophone at a series of increasing excitation pulse intensities and frequencies. Hydrophone measurements were made at the focal point and in the near- and far-fields of 20 MHz and 40 MHz transducers. Harmonic images of the anterior segment of the rabbit eye were obtained by a combination of analog filtering and digital post-processing. Results: Harmonics were generated nearly identically in both water and vitreous. Hydrophone measurements showed the maximum second harmonic to be -5 dB relative to the 35 MHz fundamental at the focus, while in pulse/echo the maximum harmonic amplitude was -15dB relative to the fundamental. Harmonics were absent in the near-field, but present in the far-field. Harmonic images of the eye showed improved resolution. Conclusion: Harmonics can be readily generated at very high frequencies, and at power levels compliant with FDA guidelines for ophthalmology. This technique may yield further improvements to the already impressive resolutions obtainable in this frequency range. Improved imaging of the macular region, in particular, may provide significant improvements in diagnosis of retinal disease.

Analysis of Vibrational Harmonic Response for Printing Double-Sheet Detecting System via ANSYS

NASA Astrophysics Data System (ADS)

Guo, Qiang; Cai, Ji-Fei; Wang, Yan; Zhang, Yang

In order to explore the influence of the harmonic response of system vibration upon the stability of the double-sheet detector system, the mathematical model of vibrational system is established via the mechanical dynamic theory. Vibrational system of double-sheet detector is studied by theoretical modeling, and the dynamic simulation to obtain the amplitude/phase frequency response curve of the system based on ANSYS is completed to make a comparison with the theoretical results. It is shown that the theoretical value is basically consistent with that calculated through ANSYS. Conclusion vibrational characteristics of double-sheet detection system is obtained quickly and accurately, and propound solving measures by some crucial factors, such as the harmonic load, mass and stiffness, which will affect the vibration of the system, contribute to the finite element method is applied to the complex multiple-degree-of-freedom system.

Proof of Concept for an Ultrasensitive Technique to Detect and Localize Sources of Elastic Nonlinearity Using Phononic Crystals.

PubMed

Miniaci, M; Gliozzi, A S; Morvan, B; Krushynska, A; Bosia, F; Scalerandi, M; Pugno, N M

2017-05-26

The appearance of nonlinear effects in elastic wave propagation is one of the most reliable and sensitive indicators of the onset of material damage. However, these effects are usually very small and can be detected only using cumbersome digital signal processing techniques. Here, we propose and experimentally validate an alternative approach, using the filtering and focusing properties of phononic crystals to naturally select and reflect the higher harmonics generated by nonlinear effects, enabling the realization of time-reversal procedures for nonlinear elastic source detection. The proposed device demonstrates its potential as an efficient, compact, portable, passive apparatus for nonlinear elastic wave sensing and damage detection.

Detecting Subtle Plasma Membrane Perturbation in Living Cells Using Second Harmonic Generation Imaging

PubMed Central

Moen, Erick K.; Ibey, Bennett L.; Beier, Hope T.

2014-01-01

The requirement of center asymmetry for the creation of second harmonic generation (SHG) signals makes it an attractive technique for visualizing changes in interfacial layers such as the plasma membrane of biological cells. In this article, we explore the use of lipophilic SHG probes to detect minute perturbations in the plasma membrane. Three candidate probes, Di-4-ANEPPDHQ (Di-4), FM4-64, and all-trans-retinol, were evaluated for SHG effectiveness in Jurkat cells. Di-4 proved superior with both strong SHG signal and limited bleaching artifacts. To test whether rapid changes in membrane symmetry could be detected using SHG, we exposed cells to nanosecond-pulsed electric fields, which are believed to cause formation of nanopores in the plasma membrane. Upon nanosecond-pulsed electric fields exposure, we observed an instantaneous drop of ∼50% in SHG signal from the anodic pole of the cell. When compared to the simultaneously acquired fluorescence signals, it appears that the signal change was not due to the probe diffusing out of the membrane or changes in membrane potential or fluidity. We hypothesize that this loss in SHG signal is due to disruption in the interfacial nature of the membrane. The results show that SHG imaging has great potential as a tool for measuring rapid and subtle plasma membrane disturbance in living cells. PMID:24853757

Detecting subtle plasma membrane perturbation in living cells using second harmonic generation imaging.

PubMed

Moen, Erick K; Ibey, Bennett L; Beier, Hope T

2014-05-20

The requirement of center asymmetry for the creation of second harmonic generation (SHG) signals makes it an attractive technique for visualizing changes in interfacial layers such as the plasma membrane of biological cells. In this article, we explore the use of lipophilic SHG probes to detect minute perturbations in the plasma membrane. Three candidate probes, Di-4-ANEPPDHQ (Di-4), FM4-64, and all-trans-retinol, were evaluated for SHG effectiveness in Jurkat cells. Di-4 proved superior with both strong SHG signal and limited bleaching artifacts. To test whether rapid changes in membrane symmetry could be detected using SHG, we exposed cells to nanosecond-pulsed electric fields, which are believed to cause formation of nanopores in the plasma membrane. Upon nanosecond-pulsed electric fields exposure, we observed an instantaneous drop of ~50% in SHG signal from the anodic pole of the cell. When compared to the simultaneously acquired fluorescence signals, it appears that the signal change was not due to the probe diffusing out of the membrane or changes in membrane potential or fluidity. We hypothesize that this loss in SHG signal is due to disruption in the interfacial nature of the membrane. The results show that SHG imaging has great potential as a tool for measuring rapid and subtle plasma membrane disturbance in living cells. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Quantitative second-harmonic generation imaging to detect osteogenesis imperfecta in human skin samples

NASA Astrophysics Data System (ADS)

Adur, J.; Ferreira, A. E.; D'Souza-Li, L.; Pelegati, V. B.; de Thomaz, A. A.; Almeida, D. B.; Baratti, M. O.; Carvalho, H. F.; Cesar, C. L.

2012-03-01

Osteogenesis Imperfecta (OI) is a genetic disorder that leads to bone fractures due to mutations in the Col1A1 or Col1A2 genes that affect the primary structure of the collagen I chain with the ultimate outcome in collagen I fibrils that are either reduced in quantity or abnormally organized in the whole body. A quick test screening of the patients would largely reduce the sample number to be studied by the time consuming molecular genetics techniques. For this reason an assessment of the human skin collagen structure by Second Harmonic Generation (SHG) can be used as a screening technique to speed up the correlation of genetics/phenotype/OI types understanding. In the present work we have used quantitative second harmonic generation (SHG) imaging microscopy to investigate the collagen matrix organization of the OI human skin samples comparing with normal control patients. By comparing fibril collagen distribution and spatial organization, we calculated the anisotropy and texture patterns of this structural protein. The analysis of the anisotropy was performed by means of the two-dimensional Discrete Fourier Transform and image pattern analysis with Gray-Level Co-occurrence Matrix (GLCM). From these results, we show that statistically different results are obtained for the normal and disease states of OI.

Characterization of Harmonic Signal Acquisition with Parallel Dipole and Multipole Detectors

NASA Astrophysics Data System (ADS)

Park, Sung-Gun; Anderson, Gordon A.; Bruce, James E.

2018-04-01

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is a powerful instrument for the study of complex biological samples due to its high resolution and mass measurement accuracy. However, the relatively long signal acquisition periods needed to achieve high resolution can serve to limit applications of FTICR-MS. The use of multiple pairs of detector electrodes enables detection of harmonic frequencies present at integer multiples of the fundamental cyclotron frequency, and the obtained resolving power for a given acquisition period increases linearly with the order of harmonic signal. However, harmonic signal detection also increases spectral complexity and presents challenges for interpretation. In the present work, ICR cells with independent dipole and harmonic detection electrodes and preamplifiers are demonstrated. A benefit of this approach is the ability to independently acquire fundamental and multiple harmonic signals in parallel using the same ions under identical conditions, enabling direct comparison of achieved performance as parameters are varied. Spectra from harmonic signals showed generally higher resolving power than spectra acquired with fundamental signals and equal signal duration. In addition, the maximum observed signal to noise (S/N) ratio from harmonic signals exceeded that of fundamental signals by 50 to 100%. Finally, parallel detection of fundamental and harmonic signals enables deconvolution of overlapping harmonic signals since observed fundamental frequencies can be used to unambiguously calculate all possible harmonic frequencies. Thus, the present application of parallel fundamental and harmonic signal acquisition offers a general approach to improve utilization of harmonic signals to yield high-resolution spectra with decreased acquisition time. [Figure not available: see fulltext.

High-harmonic spectroscopy of aligned molecules

NASA Astrophysics Data System (ADS)

Yun, Hyeok; Yun, Sang Jae; Lee, Gae Hwang; Nam, Chang Hee

2017-01-01

High harmonics emitted from aligned molecules driven by intense femtosecond laser pulses provide the opportunity to explore the structural information of molecules. The field-free molecular alignment technique is an expedient tool for investigating the structural characteristics of linear molecules. The underlying physics of field-free alignment, showing the characteristic revival structure specific to molecular species, is clearly explained from the quantum-phase analysis of molecular rotational states. The anisotropic nature of molecules is shown from the harmonic polarization measurement performed with spatial interferometry. The multi-orbital characteristics of molecules are investigated using high-harmonic spectroscopy, applied to molecules of N2 and CO2. In the latter case the two-dimensional high-harmonic spectroscopy, implemented using a two-color laser field, is applied to distinguish harmonics from different orbitals. Molecular high-harmonic spectroscopy will open a new route to investigate ultrafast dynamics of molecules.

Dual-frequency transducer with a wideband PVDF receiver for contrast-enhanced, adjustable harmonic imaging

NASA Astrophysics Data System (ADS)

Kim, Jinwook; Lindsey, Brooks D.; Li, Sibo; Dayton, Paul A.; Jiang, Xiaoning

2017-04-01

Acoustic angiography is a contrast-enhanced, superharmonic microvascular imaging method. It has shown the capability of high-resolution and high-contrast-to-tissue-ratio (CTR) imaging for vascular structure near tumor. Dual-frequency ultrasound transducers and arrays are usually used for this new imaging technique. Stacked-type dual-frequency transducers have been developed for this vascular imaging method by exciting injected microbubble contrast agent (MCA) in the vessels with low-frequency (1-5 MHz), moderate power ultrasound burst waves and receiving the superharmonic responses from MCA by a high-frequency receiver (>10 MHz). The main challenge of the conventional dual-frequency transducers is a limited penetration depth (<25 mm) due to the insufficient receiving sensitivity for highfrequency harmonic signal detection. A receiver with a high receiving sensitivity spanning a wide superharmonic frequency range (3rd to 6th) enables selectable bubble harmonic detection considering the required penetration depth. Here, we develop a new dual-frequency transducer composed of a 2 MHz 1-3 composite transmitter and a polyvinylidene fluoride (PVDF) receiver with a receiving frequency range of 4-12 MHz for adjustable harmonic imaging. The developed transducer was tested for harmonic responses from a microbubble-injected vessel-mimicking tube positioned 45 mm away. Despite the long imaging distance (45 mm), the prototype transducer detected clear harmonic response with the contrast-to-noise ratio of 6-20 dB and the -6 dB axial resolution of 200-350 μm for imaging a 200 um-diameter cellulose tube filled with microbubbles.

Third order harmonic imaging for biological tissues using three phase-coded pulses.

PubMed

Ma, Qingyu; Gong, Xiufen; Zhang, Dong

2006-12-22

Compared to the fundamental and the second harmonic imaging, the third harmonic imaging shows significant improvements in image quality due to the better resolution, but it is degraded by the lower sound pressure and signal-to-noise ratio (SNR). In this study, a phase-coded pulse technique is proposed to selectively enhance the sound pressure of the third harmonic by 9.5 dB whereas the fundamental and the second harmonic components are efficiently suppressed and SNR is also increased by 4.7 dB. Based on the solution of the KZK nonlinear equation, the axial and lateral beam profiles of harmonics radiated from a planar piston transducer were theoretically simulated and experimentally examined. Finally, the third harmonic images using this technique were performed for several biological tissues and compared with the images obtained by the fundamental and the second harmonic imaging. Results demonstrate that the phase-coded pulse technique yields a dramatically cleaner and sharper contrast image.

Adaptive Piezoelectric Circuitry Sensor Network with High-Frequency Harmonics Interrogation for Structural Damage Detection

DTIC Science & Technology

2014-09-17

AFRL-OSR-VA-TR-2014-0255 ADAPTIVE PIEZOELECTRIC CIRCUITRY SENSOR NETWORK KON -WELL WANG MICHIGAN UNIV ANN ARBOR Final Report 09/17/2014 DISTRIBUTION A...Harmonics Interrogation for Structural Damage Detection FA9550-11-1-0072 Kon -Well Wang and Jiong Tang The Regents of the University of Michigan, 3003...mechanism. These efforts have yielded a complete methodology of adaptive high-frequency piezoelectric self-sensing interrogation. None None None SAR Kon

Harmonic Optimization in Voltage Source Inverter for PV Application using Heuristic Algorithms

NASA Astrophysics Data System (ADS)

Kandil, Shaimaa A.; Ali, A. A.; El Samahy, Adel; Wasfi, Sherif M.; Malik, O. P.

2016-12-01

Selective Harmonic Elimination (SHE) technique is the fundamental switching frequency scheme that is used to eliminate specific order harmonics. Its application to minimize low order harmonics in a three level inverter is proposed in this paper. The modulation strategy used here is SHEPWM and the nonlinear equations, that characterize the low order harmonics, are solved using Harmony Search Algorithm (HSA) to obtain the optimal switching angles that minimize the required harmonics and maintain the fundamental at the desired value. Total Harmonic Distortion (THD) of the output voltage is minimized maintaining selected harmonics within allowable limits. A comparison has been drawn between HSA, Genetic Algorithm (GA) and Newton Raphson (NR) technique using MATLAB software to determine the effectiveness of getting optimized switching angles.

Application of higher harmonic blade feathering for helicopter vibration reduction

NASA Technical Reports Server (NTRS)

Powers, R. W.

1978-01-01

Higher harmonic blade feathering for helicopter vibration reduction is considered. Recent wind tunnel tests confirmed the effectiveness of higher harmonic control in reducing articulated rotor vibratory hub loads. Several predictive analyses developed in support of the NASA program were shown to be capable of calculating single harmonic control inputs required to minimize a single 4P hub response. In addition, a multiple-input, multiple-output harmonic control predictive analysis was developed. All techniques developed thus far obtain a solution by extracting empirical transfer functions from sampled data. Algorithm data sampling and processing requirements are minimal to encourage adaptive control system application of such techniques in a flight environment.

ODF Maxima Extraction in Spherical Harmonic Representation via Analytical Search Space Reduction

PubMed Central

Aganj, Iman; Lenglet, Christophe; Sapiro, Guillermo

2015-01-01

By revealing complex fiber structure through the orientation distribution function (ODF), q-ball imaging has recently become a popular reconstruction technique in diffusion-weighted MRI. In this paper, we propose an analytical dimension reduction approach to ODF maxima extraction. We show that by expressing the ODF, or any antipodally symmetric spherical function, in the common fourth order real and symmetric spherical harmonic basis, the maxima of the two-dimensional ODF lie on an analytically derived one-dimensional space, from which we can detect the ODF maxima. This method reduces the computational complexity of the maxima detection, without compromising the accuracy. We demonstrate the performance of our technique on both artificial and human brain data. PMID:20879302

Probing biomolecular interaction forces using an anharmonic acoustic technique for selective detection of bacterial spores.

PubMed

Ghosh, Sourav K; Ostanin, Victor P; Johnson, Christian L; Lowe, Christopher R; Seshia, Ashwin A

2011-11-15

Receptor-based detection of pathogens often suffers from non-specific interactions, and as most detection techniques cannot distinguish between affinities of interactions, false positive responses remain a plaguing reality. Here, we report an anharmonic acoustic based method of detection that addresses the inherent weakness of current ligand dependant assays. Spores of Bacillus subtilis (Bacillus anthracis simulant) were immobilized on a thickness-shear mode AT-cut quartz crystal functionalized with anti-spore antibody and the sensor was driven by a pure sinusoidal oscillation at increasing amplitude. Biomolecular interaction forces between the coupled spores and the accelerating surface caused a nonlinear modulation of the acoustic response of the crystal. In particular, the deviation in the third harmonic of the transduced electrical response versus oscillation amplitude of the sensor (signal) was found to be significant. Signals from the specifically-bound spores were clearly distinguishable in shape from those of the physisorbed streptavidin-coated polystyrene microbeads. The analytical model presented here enables estimation of the biomolecular interaction forces from the measured response. Thus, probing biomolecular interaction forces using the described technique can quantitatively detect pathogens and distinguish specific from non-specific interactions, with potential applicability to rapid point-of-care detection. This also serves as a potential tool for rapid force-spectroscopy, affinity-based biomolecular screening and mapping of molecular interaction networks. Copyright © 2011 Elsevier B.V. All rights reserved.

A novel technique of harmonic tissue dissection reduces seroma formation after modified radical mastectomy compared to conventional electrocautery: a single-blind randomized controlled trial.

PubMed

Faisal, Mohammed; Fathy, Hamada; Shaban, Hamdy; Abuelela, Sameh T; Marie, Ahmed; Khaled, Islam

2018-01-01

Seroma is the most frequent postoperative complication following breast cancer surgery. Our aim was to evaluate the effect of the harmonic focus scalpel versus electrocautery in reducing seroma formation post-mastectomy and axillary clearance. A prospective randomized controlled trial study was conducted at the Department of Surgery of Suez Canal University Hospital from April 26th 2014 to 30th June 2016. Seventy-two women, in whom a mastectomy and axillary clearance for breast cancer were performed, were randomly allocated to either harmonic dissection ( n  = 36) or electrocautery ( n  = 36). The mean operative time was significantly longer for harmonic dissection compared with electrocautery (2.63 ± 0.41 vs. 1.75 ± 0.26 h; p  < 0.0001). In addition, a significantly smaller amount of intraoperative blood loss (69.4 ± 25.1 vs. 255.5 ± 41.6 ml; p  = 0.002) and total drainage volume (1277.8 ± 172.5 ml vs. 3300 ± 167.5 ml; p  = 0.002) were found in the harmonic group. Moreover, there was a significant reduction in the time of drain removal (10.9 ± 1.12 vs. 15.9 ± 1.44; p  = 0.001) and the incidence of seroma formation after drain removal [8.3% vs 33.3%; p  = 0.003] in the harmonic group compared with those in the electrocautery group. Harmonic dissection technique leads to significant decreases in intraoperative blood loss, total drainage volume and postoperative seroma in terms of shorter drain duration with a minimal increase in the operative time and better quality of life. Here, we recommend the use of the harmonic dissection technique in mastectomy and axillary clearance.

Overview of hybridization and detection techniques.

PubMed

Hilario, Elena

2007-01-01

A misconception regarding the sensitivity of nonradioactive methods for screening genomic DNA libraries often hinders the establishment of these environmentally friendly techniques in molecular biology laboratories. Nonradioactive probes, properly prepared and quantified, can detect DNA target molecules to the femtomole range. However, appropriate hybridization techniques and detection methods should also be adopted for an efficient use of nonradioactive techniques. Detailed descriptions of genomic library handling before and during the nonradioactive hybridization and detection are often omitted from publications. This chapter aims to fill this void by providing a collection of technical tips on hybridization and detection techniques.

Second harmonic detection in the electrochemical strain microscopy of Ag-ion conducting glass

DOE PAGES

Yang, Sangmo; Okatan, Mahmut Baris; Paranthaman, Mariappan Parans; ...

2014-11-14

The first and second harmonic electromechanical responses and their cross-correlation in Ag-ion conducting glass were investigated using band-excitation electrochemical strain microscopy (ESM). Consecutive ESM images with increasing magnitudes of the applied AC voltage allowed observation of not only reversible surface displacement but also irreversible silver nanoparticle formation above a certain threshold voltage. The second harmonic ESM response was anticorrelated with the first harmonic response in many local regions. Furthermore, the nucleation sites of silver nanoparticles were closely related to the anti-correlated regions, specifically, with low second harmonic and high first harmonic ESM responses. The possible origins of the second harmonicmore » ESM response are discussed.« less

Separation of High Order Harmonics with Fluoride Windows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allison, Tom; van Tilborg, Jeroen; Wright, Travis

2010-08-02

The lower orders produced in high order harmonic generation can be effciently temporally separated into monochromatic pulses by propagation in a Fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF2, CaF2, and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We demonstrate the use of this simple and inexpensive technique in a femtosecond pump/probe experiment using the fifth harmonic.

Remote detection of electronic devices

DOEpatents

Judd, Stephen L [Los Alamos, NM; Fortgang, Clifford M [Los Alamos, NM; Guenther, David C [Los Alamos, NM

2012-09-25

An apparatus and method for detecting solid-state electronic devices are described. Non-linear junction detection techniques are combined with spread-spectrum encoding and cross correlation to increase the range and sensitivity of the non-linear junction detection and to permit the determination of the distances of the detected electronics. Nonlinear elements are detected by transmitting a signal at a chosen frequency and detecting higher harmonic signals that are returned from responding devices.

Influence of crack opening and incident wave angle on second harmonic generation of Lamb waves

NASA Astrophysics Data System (ADS)

Yang, Yi; Ng, Ching-Tai; Kotousov, Andrei

2018-05-01

Techniques utilising second harmonic generation (SHG) have proven their great potential in detecting contact-type damage. However, the gap between the practical applications and laboratory studies is still quite large. The current work is aimed to bridge this gap by investigating the effects of the applied load and incident wave angle on the detectability of fatigue cracks at various lengths. Both effects are critical for practical implementations of these techniques. The present experimental study supported by three-dimensional (3D) finite element (FE) modelling has demonstrated that the applied load, which changes the crack opening and, subsequently, the contact nonlinearity, significantly affects the amplitude of the second harmonic generated by the fundamental symmetric mode (S0) of Lamb wave. This amplitude is also dependent on the length of the fatigue crack as well as the incident wave angle. The experimental and FE results correlate well, so the modelling approach can be implemented for practical design of damage monitoring systems as well as for the evaluation of the severity of the fatigue cracks.

Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms.

PubMed

Wei, Wei; Chang, Jun; Wang, Qiang; Qin, Zengguang

2017-01-15

A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%.

Modulation Index Adjustment for Recovery of Pure Wavelength Modulation Spectroscopy Second Harmonic Signal Waveforms

PubMed Central

Wei, Wei; Chang, Jun; Wang, Qiang; Qin, Zengguang

2017-01-01

A new technique of modulation index adjustment for pure wavelength modulation spectroscopy second harmonic signal waveforms recovery is presented. As the modulation index is a key parameter in determining the exact form of the signals generated by the technique of wavelength modulation spectroscopy, the method of modulation index adjustment is applied to recover the second harmonic signal with wavelength modulation spectroscopy. By comparing the measured profile with the theoretical profile by calculation, the relationship between the modulation index and average quantities of the scanning wavelength can be obtained. Furthermore, when the relationship is applied in the experimental setup by point-by-point modulation index modification for gas detection, the results show good agreement with the theoretical profile and signal waveform distortion (such as the amplitude modulation effect caused by diode laser) can be suppressed. Besides, the method of modulation index adjustment can be used in many other aspects which involve profile improvement. In practical applications, when the amplitude modulation effect can be neglected and the stability of the detection system is limited by the sampling rate of analog-to-digital, modulation index adjustment can be used to improve detection into softer inflection points and solve the insufficient sampling problem. As a result, measurement stability is improved by 40%. PMID:28098842

[Practical skills of harmonic scalpel in laparoscopic gastrointestinal surgery].

PubMed

Li, Guo-xin

2013-10-01

Harmonic scalpel, one of the most commonly used energy tools, have been recognized as an important revolutionary development in surgical device. Due to its convenience in cutting, coagulating, and dissecting harmonic scalpel has been increasingly used to performed surgery by more and more surgeons. In gastrointestinal surgeries, however, many manipulationssuch as dissecting soft connective tissues off the stomach or colon, isolating and cutting particular vessels, would require proper techniques in handling harmonic scalpels. Thus, based on our experiences of using harmonic scalpel in laparoscopic gastrointestinal surgeries, we summarized a "nine-word tactics", which may be helpful for beginners to use harmonic scalpels in a proper and efficient manner.

Islanding detection technique using wavelet energy in grid-connected PV system

NASA Astrophysics Data System (ADS)

Kim, Il Song

2016-08-01

This paper proposes a new islanding detection method using wavelet energy in a grid-connected photovoltaic system. The method detects spectral changes in the higher-frequency components of the point of common coupling voltage and obtains wavelet coefficients by multilevel wavelet analysis. The autocorrelation of the wavelet coefficients can clearly identify islanding detection, even in the variations of the grid voltage harmonics during normal operating conditions. The advantage of the proposed method is that it can detect islanding condition the conventional under voltage/over voltage/under frequency/over frequency methods fail to detect. The theoretical method to obtain wavelet energies is evolved and verified by the experimental result.

Thermally and electrically controllable multiple high harmonics generation by harmonically driven quasi-two-dimensional electron gas

NASA Astrophysics Data System (ADS)

Maglevanny, I. I.; Smolar, V. A.; Karyakina, T. I.

2018-06-01

In this paper, we consider the activation processes in nonlinear meta-stable system based on a lateral (quasi-two-dimensional) superlattice and study the dynamics of such a system externally driven by a harmonic force. The internal control parameters are the longitudinal applied electric field and the sample temperature. The spontaneous transverse electric field is considered as an order parameter. The forced violations of order parameter are considered as a response of a system to periodic driving. We investigate the cooperative effects of self-organization and high harmonic forcing from the viewpoint of catastrophe theory and show the possibility of generation of third and higher odd harmonics in output signal that lead to distortion of its wave front. A higher harmonics detection strategy is further proposed and explained in detail by exploring the influences of system parameters on the response output of the system that are discussed through numerical simulations.

On-the-Fly Control of High-Harmonic Generation Using a Structured Pump Beam

NASA Astrophysics Data System (ADS)

Hareli, Liran; Lobachinsky, Lilya; Shoulga, Georgiy; Eliezer, Yaniv; Michaeli, Linor; Bahabad, Alon

2018-05-01

We demonstrate experimentally a relatively simple yet powerful all-optical enhancement and control technique for high harmonic generation. This is achieved by using as a pump beam two different spatial optical modes interfering together to realize tunable periodic quasi-phase matching of the interaction. With this technique, we demonstrate on-the-fly quasi-phase matching of harmonic orders 29-41 at ambient gas pressure levels of 50 and 100 Torr, where an up to 100-fold enhancement of the emission is observed. The technique is scalable to different harmonic orders and ambient pressure conditions.

On-the-Fly Control of High-Harmonic Generation Using a Structured Pump Beam.

PubMed

Hareli, Liran; Lobachinsky, Lilya; Shoulga, Georgiy; Eliezer, Yaniv; Michaeli, Linor; Bahabad, Alon

2018-05-04

We demonstrate experimentally a relatively simple yet powerful all-optical enhancement and control technique for high harmonic generation. This is achieved by using as a pump beam two different spatial optical modes interfering together to realize tunable periodic quasi-phase matching of the interaction. With this technique, we demonstrate on-the-fly quasi-phase matching of harmonic orders 29-41 at ambient gas pressure levels of 50 and 100 Torr, where an up to 100-fold enhancement of the emission is observed. The technique is scalable to different harmonic orders and ambient pressure conditions.

Nanotwin Detection and Domain Polarity Determination via Optical Second Harmonic Generation Polarimetry.

PubMed

Ren, Ming-Liang; Agarwal, Rahul; Nukala, Pavan; Liu, Wenjing; Agarwal, Ritesh

2016-07-13

We demonstrate that optical second harmonic generation (SHG) can be utilized to determine the exact nature of nanotwins in noncentrosymmetric crystals, which is challenging to resolve via conventional transmission electron or scanned probe microscopies. Using single-crystalline nanotwinned CdTe nanobelts and nanowires as a model system, we show that SHG polarimetry can distinguish between upright (Cd-Te bonds) and inverted (Cd-Cd or Te-Te bonds) twin boundaries in the system. Inverted twin boundaries are generally not reported in nanowires due to the lack of techniques and complexity associated with the study of the nature of such defects. Precise characterization of the nature of defects in nanocrystals is required for deeper understanding of their growth and physical properties to enable their application in future devices.

Analysing Harmonic Motions with an iPhone's Magnetometer

ERIC Educational Resources Information Center

Yavuz, Ahmet; Temiz, Burak Kagan

2016-01-01

In this paper, we propose an experiment for analysing harmonic motion using an iPhone's (or iPad's) magnetometer. This experiment consists of the detection of magnetic field variations obtained from an iPhone's magnetometer sensor. A graph of harmonic motion is directly displayed on the iPhone's screen using the "Sensor Kinetics"…

Optical Kerr effect in graphene: Theoretical analysis of the optical heterodyne detection technique

NASA Astrophysics Data System (ADS)

Savostianova, N. A.; Mikhailov, S. A.

2018-04-01

Graphene is an atomically thin two-dimensional material demonstrating strong optical nonlinearities, including harmonics generation, four-wave mixing, Kerr, and other nonlinear effects. In this paper we theoretically analyze the optical heterodyne detection (OHD) technique of measuring the optical Kerr effect (OKE) in two-dimensional crystals and show how to relate the quantities measured in such experiments with components of the third-order conductivity tensor σαβ γ δ (3 )(ω1,ω2,ω3) of the two-dimensional crystal. Using results of a recently developed quantum theory of the third-order nonlinear electrodynamic response of graphene, we analyze the frequency, charge carrier density, temperature, and other dependencies of the OHD-OKE response of this material. We compare our results with a recent OHD-OKE experiment in graphene and find good agreement between the theory and experiment.

Neck dissection with harmonic scalpel and electrocautery? A randomised study.

PubMed

Verma, Roshan K; Mathiazhagan, Arulalan; Panda, Naresh K

2017-10-01

Is the use of harmonic scalpel for neck dissection useful? Literature search did not show a single, prospective, randomised control trial. We intended to study the role of harmonic scalpel in neck dissection and compare it with conventional electrocautery technique for oral cavity carcinoma. 40 patients undergoing selective neck dissection for primary oral cavity malignancy were enrolled in this study. The harmonic scalpel (HS) group consisted of 20 patients, and the electrocautery technique (ET) group comprised of 20 patients. The following variables were examined: intraoperative blood loss, operative time, number of ligatures used, postoperative drain, and postoperative hospital stay. Intraoperative blood loss was found to be significantly reduced in harmonic scalpel group as compared to electrocautery group. However, we found no difference in other parameters like operative time, postop drain, postoperative hospital stay and number of ligatures used between both groups. Harmonic scalpel for neck dissection is associated with significantly lesser intraoperative blood loss as compared to electrocautery. There is no effect on operative time and postoperative hospital stay in both groups. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Polarization-Modulated Second Harmonic Generation Microscopy in Collagen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoller, P C

Collagen is a key structural protein in the body; several pathological conditions lead to changes in collagen. Among imaging modalities that can be used in vivo, second harmonic generation (SHG) microscopy has a key advantage: it provides {approx}1 {micro}m resolution information about collagen structure as a function of depth. A new technique--polarization-modulated SHG--is presented: it permits simultaneous measurement of collagen orientation, of a lower bound on the magnitude of the second order nonlinear susceptibility tensor, and of the ratio of the two independent elements in this tensor. It is applied to characterizing SHG in collagen and to determining effects ofmore » biologically relevant changes in collagen structure. The magnitude of the second harmonic signal in two dimensional images varies with position even in structurally homogeneous tissue; this phenomenon is due to interference between second harmonic light generated by neighboring fibrils, which are randomly oriented parallel or anti-parallel to each other. Studies in which focal spot size was varied indicated that regions where fibrils are co-oriented are less than {approx}1.5 {micro}m in diameter. A quartz reference was used to determine the spot size as well as a lower limit (d{sub xxx} > 0.3 pm/V) for the magnitude of the second order nonlinear susceptibility. The ratio of the two independent tensor elements ranged between d{sub XYY}/d{sub XXX} = 0.60 and 0.75. SHG magnitude alone was not useful for identifying structural anomalies in collagenous tissue. Instead, changes in the polarization dependence of SHG were used to analyze biologically relevant perturbations in collagen structure. Changes in polarization dependence were observed in dehydrated samples, but not in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable SHG signal. Collagen orientation was measured in

Unlocking higher harmonics in atomic force microscopy with gentle interactions.

PubMed

Santos, Sergio; Barcons, Victor; Font, Josep; Verdaguer, Albert

2014-01-01

In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.

Measurement of optical-beat frequency in a photoconductive terahertz-wave generator using microwave higher harmonics.

PubMed

Murasawa, Kengo; Sato, Koki; Hidaka, Takehiko

2011-05-01

A new method for measuring optical-beat frequencies in the terahertz (THz) region using microwave higher harmonics is presented. A microwave signal was applied to the antenna gap of a photoconductive (PC) device emitting a continuous electromagnetic wave at about 1 THz by the photomixing technique. The microwave higher harmonics with THz frequencies are generated in the PC device owing to the nonlinearity of the biased photoconductance, which is briefly described in this article. Thirteen nearly periodic peaks in the photocurrent were observed when the microwave was swept from 16 to 20 GHz at a power of -48 dBm. The nearly periodic peaks are generated by the homodyne detection of the optical beat with the microwave higher harmonics when the frequency of the harmonics coincides with the optical-beat frequency. Each peak frequency and its peak width were determined by fitting a Gaussian function, and the order of microwave harmonics was determined using a coarse (i.e., lower resolution) measurement of the optical-beat frequency. By applying the Kalman algorithm to the peak frequencies of the higher harmonics and their standard deviations, the optical-beat frequency near 1 THz was estimated to be 1029.81 GHz with the standard deviation of 0.82 GHz. The proposed method is applicable to a conventional THz-wave generator with a photomixer.

Simulation study of amplitude-modulated (AM) harmonic motion imaging (HMI) for stiffness contrast quantification with experimental validation.

PubMed

Maleke, Caroline; Luo, Jianwen; Gamarnik, Viktor; Lu, Xin L; Konofagou, Elisa E

2010-07-01

The objective of this study is to show that Harmonic Motion Imaging (HMI) can be used as a reliable tumor-mapping technique based on the tumor's distinct stiffness at the early onset of disease. HMI is a radiation-force-based imaging method that generates a localized vibration deep inside the tissue to estimate the relative tissue stiffness based on the resulting displacement amplitude. In this paper, a finite-element model (FEM) study is presented, followed by an experimental validation in tissue-mimicking polyacrylamide gels and excised human breast tumors ex vivo. This study compares the resulting tissue motion in simulations and experiments at four different gel stiffnesses and three distinct spherical inclusion diameters. The elastic moduli of the gels were separately measured using mechanical testing. Identical transducer parameters were used in both the FEM and experimental studies, i.e., a 4.5-MHz single-element focused ultrasound (FUS) and a 7.5-MHz diagnostic (pulse-echo) transducer. In the simulation, an acoustic pressure field was used as the input stimulus to generate a localized vibration inside the target. Radiofrequency (rf) signals were then simulated using a 2D convolution model. A one-dimensional cross-correlation technique was performed on the simulated and experimental rf signals to estimate the axial displacement resulting from the harmonic radiation force. In order to measure the reliability of the displacement profiles in estimating the tissue stiffness distribution, the contrast-transfer efficiency (CTE) was calculated. For tumor mapping ex vivo, a harmonic radiation force was applied using a 2D raster-scan technique. The 2D HMI images of the breast tumor ex vivo could detect a malignant tumor (20 x 10 mm2) surrounded by glandular and fat tissues. The FEM and experimental results from both gels and breast tumors ex vivo demonstrated that HMI was capable of detecting and mapping the tumor or stiff inclusion with various diameters or

Progress in Arc Safety System Based on Harmonics Detection for ICRH Antennae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger-By, G.; Beaumont, B.; Lombard, G.

2007-09-28

The arc detection systems based on harmonics detection have been tested n USA (TFTR, DIII, Alcator C-mod) and Germany (Asdex). These systems have some advantages in comparison with traditonal securities which use a threshold on the Vr/Vf (Reflected to Forward voltage ratio) calculation and are ITER relevant. On Tore Supra (TS) 3 systems have been built using this principle with some improvements and new features to increase the protection of the 3 ICRH generators and antennae. On JET 2 arc safety systems based on the TS principle wil also be used to mprove the JET ITER-like antenna safety. In ordermore » to have the maximum security level on the TS ICRH system, the 3 antennae are used with these systems during all plasma shots n redundancy with the other systems. This TS RF principle and ts electronic interactions with the VME control of the generator are described. The results on the TS ICRH transmitter feeding the 3 antennae are summarized and some typical signals are given.« less

Automatic computation and solution of generalized harmonic balance equations

NASA Astrophysics Data System (ADS)

Peyton Jones, J. C.; Yaser, K. S. A.; Stevenson, J.

2018-02-01

Generalized methods are presented for generating and solving the harmonic balance equations for a broad class of nonlinear differential or difference equations and for a general set of harmonics chosen by the user. In particular, a new algorithm for automatically generating the Jacobian of the balance equations enables efficient solution of these equations using continuation methods. Efficient numeric validation techniques are also presented, and the combined algorithm is applied to the analysis of dc, fundamental, second and third harmonic response of a nonlinear automotive damper.

Analysing harmonic motions with an iPhone’s magnetometer

NASA Astrophysics Data System (ADS)

Yavuz, Ahmet; Kağan Temiz, Burak

2016-05-01

In this paper, we propose an experiment for analysing harmonic motion using an iPhone’s (or iPad’s) magnetometer. This experiment consists of the detection of magnetic field variations obtained from an iPhone’s magnetometer sensor. A graph of harmonic motion is directly displayed on the iPhone’s screen using the Sensor Kinetics application. Data from this application was analysed with Eureqa software to establish the equation of the harmonic motion. Analyses show that the use of an iPhone’s magnetometer to analyse harmonic motion is a practical and effective method for small oscillations and frequencies less than 15-20 Hz.

A masking level difference due to harmonicity.

PubMed

Treurniet, W C; Boucher, D R

2001-01-01

The role of harmonicity in masking was studied by comparing the effect of harmonic and inharmonic maskers on the masked thresholds of noise probes using a three-alternative, forced-choice method. Harmonic maskers were created by selecting sets of partials from a harmonic series with an 88-Hz fundamental and 45 consecutive partials. Inharmonic maskers differed in that the partial frequencies were perturbed to nearby values that were not integer multiples of the fundamental frequency. Average simultaneous-masked thresholds were as much as 10 dB lower with the harmonic masker than with the inharmonic masker, and this difference was unaffected by masker level. It was reduced or eliminated when the harmonic partials were separated by more than 176 Hz, suggesting that the effect is related to the extent to which the harmonics are resolved by auditory filters. The threshold difference was not observed in a forward-masking experiment. Finally, an across-channel mechanism was implicated when the threshold difference was found between a harmonic masker flanked by harmonic bands and a harmonic masker flanked by inharmonic bands. A model developed to explain the observed difference recognizes that an auditory filter output envelope is modulated when the filter passes two or more sinusoids, and that the modulation rate depends on the differences among the input frequencies. For a harmonic masker, the frequency differences of adjacent partials are identical, and all auditory filters have the same dominant modulation rate. For an inharmonic masker, however, the frequency differences are not constant and the envelope modulation rate varies across filters. The model proposes that a lower variability facilitates detection of a probe-induced change in the variability, thus accounting for the masked threshold difference. The model was supported by significantly improved predictions of observed thresholds when the predictor variables included envelope modulation rate variance measured

Remote Leak Detection: Indirect Thermal Technique

NASA Technical Reports Server (NTRS)

Clements, Sandra

2002-01-01

Remote sensing technologies are being considered for efficient, low cost gas leak detection. Eleven specific techniques have been identified for further study and evaluation of several of these is underway. The Indirect Thermal Technique is one of the techniques that is being explored. For this technique, an infrared camera is used to detect the temperature change of a pipe or fitting at the site of a gas leak. This temperature change is caused by the change in temperature of the gas expanding from the leak site. During the 10-week NFFP program, the theory behind the technique was further developed, experiments were performed to determine the conditions for which the technique might be viable, and a proof-of-concept system was developed and tested in the laboratory.

Study of thermal decomposition mechanisms and low-level detection of explosives using pulsed photoacoustic technique

NASA Astrophysics Data System (ADS)

Yehya, F.; Chaudhary, A. K.; Srinivas, D.; Muralidharan, K.

2015-11-01

We report a novel time-resolved photoacoustic-based technique for studying the thermal decomposition mechanisms of some secondary explosives such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), picric acid, 4,6-dinitro-5-(4-nitro-1 H-imidazol-1-yl)-1 H-benzo[ d] [1-3] triazole, and 5-chloro-1-(4-nitrophenyl)-1 H-tetrazole. A comparison of the thermal decomposition mechanisms of these secondary explosives was made by detecting NO2 molecules released under controlled pyrolysis between 25 and 350 °C. The results show excellent agreement with the thermogravimetric and differential thermal analysis (TGA-DTA) results. A specially designed PA cell made of stainless steel was filled with explosive vapor and pumped using second harmonic, i.e., λ = 532 nm, pulses of duration 7 ns at a 10 Hz repetition rate, obtained using a Q-switched Nd:YAG laser. The use of a combination of PA and TGA-DTA techniques enables the study of NO2 generation, and this method can be used to scale the performance of these explosives as rocket fuels. The minimum detection limits of the four explosives were 38 ppmv to 69 ppbv, depending on their respective vapor pressures.

Ultrafast Plasmonic Control of Second Harmonic Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

Ultrafast Plasmonic Control of Second Harmonic Generation

DOE PAGES

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.; ...

2016-06-01

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

Harmonic Scalpel versus electrocautery and surgical clips in head and neck free-flap harvesting.

PubMed

Dean, Nichole R; Rosenthal, Eben L; Morgan, Bruce A; Magnuson, J Scott; Carroll, William R

2014-06-01

We sought to determine the safety and utility of Harmonic Scalpel-assisted free-flap harvesting as an alternative to a combined electrocautery and surgical clip technique. The medical records of 103 patients undergoing radial forearm free-flap reconstruction (105 free flaps) for head and neck surgical defects between 2006 and 2008 were reviewed. The use of bipolar electrocautery and surgical clips for division of small perforating vessels (n = 53) was compared to ultrasonic energy (Harmonic Scalpel; Ethicon Endo-Surgery, Inc., Cincinnati, Ohio) (n = 52) free-tissue harvesting techniques. Flap-harvesting time was reduced with the use of the Harmonic Scalpel when compared with electrocautery and surgical clip harvest (31.4 vs. 36.9 minutes, respectively; p = 0.06). Two patients who underwent flap harvest with electrocautery and surgical clips developed postoperative donor site hematomas, whereas no donor site complications were noted in the Harmonic Scalpel group. Recipient site complication rates for infection, fistula, and hematoma were similar for both harvesting techniques (p = 0.77). Two flap failures occurred in the clip-assisted radial forearm free-flap harvest group, and none in the Harmonic Scalpel group. Median length of hospitalization was significantly reduced for patients who underwent free-flap harvest with the Harmonic Scalpel when compared with the other technique (7 vs. 8 days; p = 0.01). The Harmonic Scalpel is safe, and its use is feasible for radial forearm free-flap harvest.

The perception of concurrent sound objects through the use of harmonic enhancement: a study of auditory attention.

PubMed

Koulaguina, Elena; Drisdelle, Brandi Lee; Alain, Claude; Grimault, Stephan; Eck, Douglas; Vachon, François; Jolicoeur, Pierre

2015-04-01

When the frequency of one harmonic, in a sound composed of many harmonics, is briefly mistuned and then returned to the 'in-tune' frequency and phase, observers report hearing this harmonic as a separate tone long after the brief period of mistuning - a phenomenon called harmonic enhancement. Here, we examined the consequence of harmonic enhancement on listeners' ability to detect a brief amplitude notch embedded in one of the harmonics after the period of mistuning. When present, the notch was either on the enhanced harmonic or on a different harmonic. Detection was better on the enhanced harmonic than on a non-enhanced harmonic. This finding suggests that attention was drawn to the enhanced harmonic (which constituted a new sound object) thereby easing the processing of sound features (i.e., a notch) within that object. This is the first evidence of a functional consequence of the after-effect of transient mistuning on auditory perception. Moreover, the findings provide support for an attention-based explanation of the enhancement phenomenon.

[Comparison between rapid detection method of enzyme substrate technique and multiple-tube fermentation technique in water coliform bacteria detection].

PubMed

Sun, Zong-ke; Wu, Rong; Ding, Pei; Xue, Jin-Rong

2006-07-01

To compare between rapid detection method of enzyme substrate technique and multiple-tube fermentation technique in water coliform bacteria detection. Using inoculated and real water samples to compare the equivalence and false positive rate between two methods. Results demonstrate that enzyme substrate technique shows equivalence with multiple-tube fermentation technique (P = 0.059), false positive rate between the two methods has no statistical difference. It is suggested that enzyme substrate technique can be used as a standard method for water microbiological safety evaluation.

An evaluation of HEMT potential for millimeter-wave signal sources using interpolation and harmonic balance techniques

NASA Technical Reports Server (NTRS)

Kwon, Youngwoo; Pavlidis, Dimitris; Tutt, Marcel N.

1991-01-01

A large-signal analysis method based on an harmonic balance technique and a 2-D cubic spline interpolation function has been developed and applied to the prediction of InP-based HEMT oscillator performance for frequencies extending up to the submillimeter-wave range. The large-signal analysis method uses a limited number of DC and small-signal S-parameter data and allows the accurate characterization of HEMT large-signal behavior. The method has been validated experimentally using load-pull measurement. Oscillation frequency, power performance, and load requirements are discussed, with an operation capability of 300 GHz predicted using state-of-the-art devices (fmax is approximately equal to 450 GHz).

Experimental demonstration of efficient and robust second harmonic generation using the adiabatic temperature gradient method

NASA Astrophysics Data System (ADS)

Dimova, E.; Steflekova, V.; Karatodorov, S.; Kyoseva, E.

2018-03-01

We propose a way of achieving efficient and robust second-harmonic generation. The technique proposed is similar to the adiabatic population transfer in a two-state quantum system with crossing energies. If the phase mismatching changes slowly, e.g., due to a temperature gradient along the crystal, and makes the phase match for second-harmonic generation to occur, then the energy would be converted adiabatically to the second harmonic. As an adiabatic technique, the second-harmonic generation scheme presented is stable to variations in the crystal parameters, as well as in the input light, crystal length, input intensity, wavelength and angle of incidence.

Edge detection techniques for iris recognition system

NASA Astrophysics Data System (ADS)

Tania, U. T.; Motakabber, S. M. A.; Ibrahimy, M. I.

2013-12-01

Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate.

Harmonic statistics

NASA Astrophysics Data System (ADS)

Eliazar, Iddo

2017-05-01

The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their 'public relations' for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford's law, and 1/f noise.

A lightweight network anomaly detection technique

DOE PAGES

Kim, Jinoh; Yoo, Wucherl; Sim, Alex; ...

2017-03-13

While the network anomaly detection is essential in network operations and management, it becomes further challenging to perform the first line of detection against the exponentially increasing volume of network traffic. In this paper, we develop a technique for the first line of online anomaly detection with two important considerations: (i) availability of traffic attributes during the monitoring time, and (ii) computational scalability for streaming data. The presented learning technique is lightweight and highly scalable with the beauty of approximation based on the grid partitioning of the given dimensional space. With the public traffic traces of KDD Cup 1999 andmore » NSL-KDD, we show that our technique yields 98.5% and 83% of detection accuracy, respectively, only with a couple of readily available traffic attributes that can be obtained without the help of post-processing. Finally, the results are at least comparable with the classical learning methods including decision tree and random forest, with approximately two orders of magnitude faster learning performance.« less

A lightweight network anomaly detection technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jinoh; Yoo, Wucherl; Sim, Alex

While the network anomaly detection is essential in network operations and management, it becomes further challenging to perform the first line of detection against the exponentially increasing volume of network traffic. In this paper, we develop a technique for the first line of online anomaly detection with two important considerations: (i) availability of traffic attributes during the monitoring time, and (ii) computational scalability for streaming data. The presented learning technique is lightweight and highly scalable with the beauty of approximation based on the grid partitioning of the given dimensional space. With the public traffic traces of KDD Cup 1999 andmore » NSL-KDD, we show that our technique yields 98.5% and 83% of detection accuracy, respectively, only with a couple of readily available traffic attributes that can be obtained without the help of post-processing. Finally, the results are at least comparable with the classical learning methods including decision tree and random forest, with approximately two orders of magnitude faster learning performance.« less

Current trends in explosive detection techniques.

PubMed

Caygill, J Sarah; Davis, Frank; Higson, Seamus P J

2012-01-15

The detection of explosives and explosive-related compounds has become a heightened priority in recent years for homeland security and counter-terrorism applications. There has been a huge increase in research within this area-through both the development of new, innovative detection approaches and the improvement of existing techniques. Developments for miniaturisation, portability, field-ruggedisation and improvements in stand-off distances, selectivity and sensitivity have been necessary to develop and improve techniques. This review provides a consolidation of information relating to recent advances in explosive detection techniques without being limited to one specific research area or explosive type. The focus of this review will be towards advances in the last 5 years, with the reader being referred to earlier reviews where appropriate. Copyright © 2011. Published by Elsevier B.V.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics.

PubMed

Boedo, J A; Rudakov, D L

2017-03-01

We present a method to calculate the ion saturation current, I sat , for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat . It is noted that the I sat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e . We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boedo, J. A.; Rudakov, D. L.

Here we present a method to calculate the ion saturation current, I sat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuouslymore » biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.« less

Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

DOE PAGES

Boedo, J. A.; Rudakov, D. L.

2017-03-20

Here we present a method to calculate the ion saturation current, I sat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of I sat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating T e. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuouslymore » biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.« less

Generation of intense high-order vortex harmonics.

PubMed

Zhang, Xiaomei; Shen, Baifei; Shi, Yin; Wang, Xiaofeng; Zhang, Lingang; Wang, Wenpeng; Xu, Jiancai; Yi, Longqiong; Xu, Zhizhan

2015-05-01

This Letter presents for the first time a scheme to generate intense high-order optical vortices that carry orbital angular momentum in the extreme ultraviolet region based on relativistic harmonics from the surface of a solid target. In the three-dimensional particle-in-cell simulation, the high-order harmonics of the high-order vortex mode is generated in both reflected and transmitted light beams when a linearly polarized Laguerre-Gaussian laser pulse impinges on a solid foil. The azimuthal mode of the harmonics scales with its order. The intensity of the high-order vortex harmonics is close to the relativistic region, with the pulse duration down to attosecond scale. The obtained intense vortex beam possesses the combined properties of fine transversal structure due to the high-order mode and the fine longitudinal structure due to the short wavelength of the high-order harmonics. In addition to the application in high-resolution detection in both spatial and temporal scales, it also presents new opportunities in the intense vortex required fields, such as the inner shell ionization process and high energy twisted photons generation by Thomson scattering of such an intense vortex beam off relativistic electrons.

Discrimination of radiation quality through second harmonic out-of-phase cw-ESR detection.

PubMed

Marrale, Maurizio; Longo, Anna; Brai, Maria; Barbon, Antonio; Brustolon, Marina

2014-02-01

The ability to discriminate the quality of ionizing radiation is important because the biological effects produced in tissue strongly depends on both absorbed dose and linear energy transfer (LET) of ionizing particles. Here we present an experimental electron spin resonance (ESR) analysis aimed at discriminating the effective LETs of various radiation beams (e.g., 19.3 MeV protons, (60)Co photons and thermal neutrons). The measurement of the intensities of the continuous wave spectrometer signal channel first harmonic in-phase and the second harmonic out-of-phase components are used to distinguish the radiation quality. A computational analysis, was carried out to evaluate the dependence of the first harmonic in-phase and second harmonic out-of-phase components on microwave power, modulation amplitude and relaxation times, and highlights that these components could be used to point out differences in the relaxation times. On the basis of this numerical analysis the experimental results are discussed. The methodology described in this study has the potential to provide information on radiation quality.

Measurement of Oxygen A Band Line Parameters by Using Modulation Spectroscopy with Higher Harmonic Detection

NASA Technical Reports Server (NTRS)

Dharamsi, Amin

1999-01-01

Wavelength modulation spectroscopy is used to demonstrate that extremely weak absorption lines can be measured even when these lines suffer from interference from the wings of adjacent stronger lines. It is shown that the use of detection at several harmonics allows such interference to be examined clearly and conveniently. The results of experimental measurements on a weak magnetic dipole driven, spin-forbidden line in the oxygen A band, which experiences interference from the wings of a pair of adjacent lines towards the blue and red regions of line center, are presented. A comparison of the experimental results to theory is given.

High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Alexander Roy; Krushelnick, Karl

2016-09-08

We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactionsmore » at 10 21 Wcm -2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.« less

Simulation of 100-300 GHz solid-state harmonic sources

NASA Technical Reports Server (NTRS)

Zybura, Michael F.; Jones, J. Robert; Jones, Stephen H.; Tait, Gregory B.

1995-01-01

Accurate and efficient simulations of the large-signal time-dependent characteristics of second-harmonic Transferred Electron Oscillators (TEO's) and Heterostructure Barrier Varactor (HBV) frequency triplers have been obtained. This is accomplished by using a novel and efficient harmonic-balance circuit analysis technique which facilitates the integration of physics-based hydrodynamic device simulators. The integrated hydrodynamic device/harmonic-balance circuit simulators allow TEO and HBV circuits to be co-designed from both a device and a circuit point of view. Comparisons have been made with published experimental data for both TEO's and HBV's. For TEO's, excellent correlation has been obtained at 140 GHz and 188 GHz in second-harmonic operation. Excellent correlation has also been obtained for HBV frequency triplers operating near 200 GHz. For HBV's, both a lumped quasi-static equivalent circuit model and the hydrodynamic device simulator have been linked to the harmonic-balance circuit simulator. This comparison illustrates the importance of representing active devices with physics-based numerical device models rather than analytical device models.

Relation of squeezed states between damped harmonic and simple harmonic oscillators

NASA Technical Reports Server (NTRS)

Um, Chung-In; Yeon, Kyu-Hwang; George, Thomas F.; Pandey, Lakshmi N.

1993-01-01

The minimum uncertainty and other relations are evaluated in the framework of the coherent states of the damped harmonic oscillator. It is shown that the coherent states of the damped harmonic oscillator are the squeezed coherent states of the simple harmonic oscillator. The unitary operator is also constructed, and this connects coherent states with damped harmonic and simple harmonic oscillators.

Biosensing Using Magnetic Particle Detection Techniques

PubMed Central

Chen, Yi-Ting; Kolhatkar, Arati G.; Zenasni, Oussama; Xu, Shoujun

2017-01-01

Magnetic particles are widely used as signal labels in a variety of biological sensing applications, such as molecular detection and related strategies that rely on ligand-receptor binding. In this review, we explore the fundamental concepts involved in designing magnetic particles for biosensing applications and the techniques used to detect them. First, we briefly describe the magnetic properties that are important for bio-sensing applications and highlight the associated key parameters (such as the starting materials, size, functionalization methods, and bio-conjugation strategies). Subsequently, we focus on magnetic sensing applications that utilize several types of magnetic detection techniques: spintronic sensors, nuclear magnetic resonance (NMR) sensors, superconducting quantum interference devices (SQUIDs), sensors based on the atomic magnetometer (AM), and others. From the studies reported, we note that the size of the MPs is one of the most important factors in choosing a sensing technique. PMID:28994727

Detection the nonlinear ultrasonic signals based on modified Duffing equations

NASA Astrophysics Data System (ADS)

Zhang, Yuhua; Mao, Hanling; Mao, Hanying; Huang, Zhenfeng

The nonlinear ultrasonic signals, like second harmonic generation (SHG) signals, could reflect the nonlinearity of material induced by fatigue damage in nonlinear ultrasonic technique which are weak nonlinear signals and usually submerged by strong background noise. In this paper the modified Duffing equations are applied to detect the SHG signals relating to the fatigue damage of material. Due to the Duffing equation could only detect the signal with specific frequency and initial phase, firstly the frequency transformation is carried on the Duffing equation which could detect the signal with any frequency. Then the influence of initial phases of to-be-detected signal and reference signal on the detection result is studied in detail, four modified Duffing equations are proposed to detect actual engineering signals with any initial phase. The relationship between the response amplitude and the total driving force is applied to estimate the amplitude of weak periodic signal. The detection results show the modified Duffing equations could effectively detect the second harmonic in SHG signals. When the SHG signals include strong background noise, the noise doesn't change the motion state of Duffing equation and the second harmonic signal could be detected until the SNR of noisy SHG signals are -26.3, yet the frequency spectrum method could only identify when the SNR is greater than 0.5. When estimation the amplitude of second harmonic signal, the estimation error of Duffing equation is obviously less than the frequency spectrum analysis method under the same noise level, which illustrates the Duffing equation has the noise immune capacity. The presence of the second harmonic signal in nonlinear ultrasonic experiments could provide an insight about the early fatigue damage of engineering components.

Second Harmonic Generation Guided Raman Spectroscopy for Sensitive Detection of Polymorph Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhury, Azhad U.; Ye, Dong Hye; Song, Zhengtian

Second harmonic generation (SHG) was integrated with Raman spectroscopy for the analysis of pharmaceutical materials. Particulate formulations of clopidogrel bisulfate were prepared in two crystal forms (Form I and Form II). Image analysis approaches enable automated identification of particles by bright field imaging, followed by classification by SHG. Quantitative SHG microscopy enabled discrimination of crystal form on a per particle basis with 99.95% confidence in a total measurement time of ~10 ms per particle. Complementary measurements by Raman and synchrotron XRD are in excellent agreement with the classifications made by SHG, with measurement times of ~1 min and several secondsmore » per particle, respectively. Coupling these capabilities with at-line monitoring may enable real-time feedback for reaction monitoring during pharmaceutical production to favor the more bioavailable but metastable Form I with limits of detection in the ppm regime.« less

Ambient air contamination: Characterization and detection techniques

NASA Technical Reports Server (NTRS)

Nulton, C. P.; Silvus, H. S.

1985-01-01

Techniques to characterize and detect sources of ambient air contamination are described. Chemical techniques to identify indoor contaminants are outlined, they include gas chromatography, or colorimetric detection. Organics generated from indoor materials at ambient conditions and upon combustion are characterized. Piezoelectric quartz crystals are used as precision frequency determining elements in electronic oscillators.

A harmonic pulse testing method for leakage detection in deep subsurface storage formations

NASA Astrophysics Data System (ADS)

Sun, Alexander Y.; Lu, Jiemin; Hovorka, Susan

2015-06-01

Detection of leakage in deep geologic storage formations (e.g., carbon sequestration sites) is a challenging problem. This study investigates an easy-to-implement frequency domain leakage detection technology based on harmonic pulse testing (HPT). Unlike conventional constant-rate pressure interference tests, HPT stimulates a reservoir using periodic injection rates. The fundamental principle underlying HPT-based leakage detection is that leakage modifies a storage system's frequency response function, thus providing clues of system malfunction. During operations, routine HPTs can be conducted at multiple pulsing frequencies to obtain experimental frequency response functions, using which the possible time-lapse changes are examined. In this work, a set of analytical frequency response solutions is derived for predicting system responses with and without leaks for single-phase flow systems. Sensitivity studies show that HPT can effectively reveal the presence of leaks. A search procedure is then prescribed for locating the actual leaks using amplitude and phase information obtained from HPT, and the resulting optimization problem is solved using the genetic algorithm. For multiphase flows, the applicability of HPT-based leakage detection procedure is exemplified numerically using a carbon sequestration problem. Results show that the detection procedure is applicable if the average reservoir conditions in the testing zone stay relatively constant during the tests, which is a working assumption under many other interpretation methods for pressure interference tests. HPT is a cost-effective tool that only requires periodic modification of the nominal injection rate. Thus it can be incorporated into existing monitoring plans with little additional investment.

[Gas pipeline leak detection based on tunable diode laser absorption spectroscopy].

PubMed

Zhang, Qi-Xing; Wang, Jin-Jun; Liu, Bing-Hai; Cai, Ting-Li; Qiao, Li-Feng; Zhang, Yong-Ming

2009-08-01

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.

Harmonic generation with multiple wiggler schemes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonifacio, R.; De Salvo, L.; Pierini, P.

1995-02-01

In this paper the authors give a simple theoretical description of the basic physics of the single pass high gain free electron laser (FEL), describing in some detail the FEL bunching properties and the harmonic generation technique with a multiple-wiggler scheme or a high gain optical klystron configuration.

Pulse compression of harmonic chirp signals using the fractional fourier transform.

PubMed

Arif, M; Cowell, D M J; Freear, S

2010-06-01

In ultrasound harmonic imaging with chirp-coded excitation, a harmonic matched filter (HMF) is typically used on the received signal to perform pulse compression of the second harmonic component (SHC) to recover signal axial resolution. Designing the HMF for the compression of the SHC is a problematic issue because it requires optimal window selection. In the compressed second harmonic signal, the sidelobe level may increase and the mainlobe width (MLW) widen under a mismatched condition, resulting in loss of axial resolution. We propose the use of the fractional Fourier transform (FrFT) as an alternative tool to perform compression of the chirp-coded SHC generated as a result of the nonlinear propagation of an ultrasound signal. Two methods are used to experimentally assess the performance benefits of the FrFT technique over the HMF techniques. The first method uses chirp excitation with central frequency of 2.25 MHz and bandwidth of 1 MHz. The second method uses chirp excitation with pulse inversion to increase the bandwidth to 2 MHz. In this study, experiments were performed in a water tank with a single-element transducer mounted coaxially with a hydrophone in a pitch-catch configuration. Results are presented that indicate that the FrFT can perform pulse compression of the second harmonic chirp component, with a 14% reduction in the MLW of the compressed signal when compared with the HMF. Also, the FrFT provides at least 23% reduction in the MLW of the compressed signal when compared with the harmonic mismatched filter (HMMF). The FrFT maintains comparable peak and integrated sidelobe levels when compared with the HMF and HMMF techniques. Copyright 2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Harmonic analysis of the precipitation in Greece

NASA Astrophysics Data System (ADS)

Nastos, P. T.; Zerefos, C. S.

2009-04-01

Greece is a country with a big variety of climates due to its geographical position, to the many mountain ranges and also to the multifarious and long coastline. The mountainous volumes are of such orientation that influences the distribution of the precipitation, having as a result, Western Greece to present great differentiations from Central and Eastern Greece. The application of harmonic analysis to the annual variability of precipitation is the goal of this study, so that the components, which compose the annual variability, be elicited. For this purpose, the mean monthly precipitation data from 30 meteorological stations of National Meteorological Service were used for the time period 1950-2000. The initial target is to reduce the number of variables and to detect structure in the relationships between variables. The most commonly used technique for this purpose is the application of Factor Analysis to a table having as columns the meteorological stations-variables and rows the monthly mean precipitation, so that 2 main factors were calculated, which explain the 98% of total variability of precipitation in Greece. Factor 1, representing the so-called uniform field and interpreting the most of the total variance, refers in fact to the Mediterranean depressions, affecting mainly the West of Greece and also the East Aegean and the Asia Minor coasts. In the process, the Fourier Analysis was applied to the factor scores extracted from the Factor Analysis, so that 2 harmonic components are resulted, which explain above the 98% of the total variability of each main factor, and are due to different synoptic and thermodynamic processes associated with Greece's precipitation construction. Finally, the calculation of the time of occurrence of the maximum precipitation, for each harmonic component of each one of the two main factors, gives the spatial distribution of appearance of the maximum precipitation in the Hellenic region.

Static harmonization of dynamically harmonized Fourier transform ion cyclotron resonance cell.

PubMed

Zhdanova, Ekaterina; Kostyukevich, Yury; Nikolaev, Eugene

2017-08-01

Static harmonization in the Fourier transform ion cyclotron resonance cell improves the resolving power of the cell and prevents dephasing of the ion cloud in the case of any trajectory of the charged particle, not necessarily axisymmetric cyclotron (as opposed to dynamic harmonization). We reveal that the Fourier transform ion cyclotron resonance cell with dynamic harmonization (paracell) is proved to be statically harmonized. The volume of the statically harmonized potential distribution increases with an increase in the number of trap segments.

Superharmonic imaging with chirp coded excitation: filtering spectrally overlapped harmonics.

PubMed

Harput, Sevan; McLaughlan, James; Cowell, David M J; Freear, Steven

2014-11-01

Superharmonic imaging improves the spatial resolution by using the higher order harmonics generated in tissue. The superharmonic component is formed by combining the third, fourth, and fifth harmonics, which have low energy content and therefore poor SNR. This study uses coded excitation to increase the excitation energy. The SNR improvement is achieved on the receiver side by performing pulse compression with harmonic matched filters. The use of coded signals also introduces new filtering capabilities that are not possible with pulsed excitation. This is especially important when using wideband signals. For narrowband signals, the spectral boundaries of the harmonics are clearly separated and thus easy to filter; however, the available imaging bandwidth is underused. Wideband excitation is preferable for harmonic imaging applications to preserve axial resolution, but it generates spectrally overlapping harmonics that are not possible to filter in time and frequency domains. After pulse compression, this overlap increases the range side lobes, which appear as imaging artifacts and reduce the Bmode image quality. In this study, the isolation of higher order harmonics was achieved in another domain by using the fan chirp transform (FChT). To show the effect of excitation bandwidth in superharmonic imaging, measurements were performed by using linear frequency modulated chirp excitation with varying bandwidths of 10% to 50%. Superharmonic imaging was performed on a wire phantom using a wideband chirp excitation. Results were presented with and without applying the FChT filtering technique by comparing the spatial resolution and side lobe levels. Wideband excitation signals achieved a better resolution as expected, however range side lobes as high as -23 dB were observed for the superharmonic component of chirp excitation with 50% fractional bandwidth. The proposed filtering technique achieved >50 dB range side lobe suppression and improved the image quality without

Historical Techniques of Lie Detection

PubMed Central

Vicianova, Martina

2015-01-01

Since time immemorial, lying has been a part of everyday life. For this reason, it has become a subject of interest in several disciplines, including psychology. The purpose of this article is to provide a general overview of the literature and thinking to date about the evolution of lie detection techniques. The first part explores ancient methods recorded circa 1000 B.C. (e.g., God’s judgment in Europe). The second part describes technical methods based on sciences such as phrenology, polygraph and graphology. This is followed by an outline of more modern-day approaches such as FACS (Facial Action Coding System), functional MRI, and Brain Fingerprinting. Finally, after the familiarization with the historical development of techniques for lie detection, we discuss the scope for new initiatives not only in the area of designing new methods, but also for the research into lie detection itself, such as its motives and regulatory issues related to deception. PMID:27247675

Second harmonic generation: Effects of the multiple reflections of the fundamental and the second harmonic waves on the Maker fringes

NASA Astrophysics Data System (ADS)

Tellier, Gildas; Boisrobert, Christian

2007-11-01

The Maker fringes technique is commonly used for the determination of nonlinear optical coefficients. In this article, we present a new formulation of Maker fringes in parallel-surface samples, using boundary conditions taking into account the anisotropy of the crystal, the refractive-index dispersion, and the reflections of the fundamental and the second harmonic waves inside the material. Complete expressions for the generated second harmonic intensity are given for birefringent crystals for the case of no pump depletion. A comparison between theory and experimental results is made, showing the accuracy of our theoretical expressions.

Cumulative phase delay between second harmonic and fundamental components--a marker for ultrasound contrast agents.

PubMed

Demi, Libertario; Wijkstra, Hessel; Mischi, Massimo

2014-12-01

Several imaging techniques aimed at detecting ultrasound contrast agents (UCAs) echo signals, while suppressing signals coming from the surrounding tissue, have been developed. These techniques are especially relevant for blood flow, perfusion, or contrast dispersion quantification. However, despite several approaches being presented, improving the understanding of the ultrasound/UCAs interaction may support further development of imaging techniques. In this paper, the physical phenomena behind the formation of harmonic components in tissue and UCAs, respectively, are addressed as a possible way to recognize the origin of the echo signals. Simulations based on a modified Rayleigh, Plesset, Noltingk, Neppiras, and Poritsky equation and transmission and backscattering measurements of ultrasound propagating through UCAs performed with a single element transducer and a submergible hydrophone, are presented. Both numerical and in vitro results show the occurrence of a cumulative time delay between the second harmonic and fundamental component which increases with UCA concentration and propagation path length through UCAs, and that was clearly observable at frequencies ( f0 = 2.5 MHz) and pressure regimes (mechanical index = 0.1) of interest for imaging. Most importantly, this delay is not observed in the absence of UCAs. In conclusion, the reported phenomenon represents a marker for UCAs with potential application for imaging.

Simple Harmonic Motion in Harmonic Plane Waves.

ERIC Educational Resources Information Center

Benumof, Reuben

1980-01-01

Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)

Human brain networks function in connectome-specific harmonic waves.

PubMed

Atasoy, Selen; Donnelly, Isaac; Pearson, Joel

2016-01-21

A key characteristic of human brain activity is coherent, spatially distributed oscillations forming behaviour-dependent brain networks. However, a fundamental principle underlying these networks remains unknown. Here we report that functional networks of the human brain are predicted by harmonic patterns, ubiquitous throughout nature, steered by the anatomy of the human cerebral cortex, the human connectome. We introduce a new technique extending the Fourier basis to the human connectome. In this new frequency-specific representation of cortical activity, that we call 'connectome harmonics', oscillatory networks of the human brain at rest match harmonic wave patterns of certain frequencies. We demonstrate a neural mechanism behind the self-organization of connectome harmonics with a continuous neural field model of excitatory-inhibitory interactions on the connectome. Remarkably, the critical relation between the neural field patterns and the delicate excitation-inhibition balance fits the neurophysiological changes observed during the loss and recovery of consciousness.

Two-harmonic complex spectral-domain optical coherence tomography using achromatic sinusoidal phase modulation

NASA Astrophysics Data System (ADS)

Lu, Sheng-Hua; Huang, Siang-Ru; Chou, Che-Chung

2018-03-01

We resolve the complex conjugate ambiguity in spectral-domain optical coherence tomography (SD-OCT) by using achromatic two-harmonic method. Unlike previous researches, the optical phase of the fiber interferometer is modulated by an achromatic phase shifter based on an optical delay line. The achromatic phase modulation leads to a wavelength-independent scaling coefficient for the two harmonics. Dividing the mean absolute value of the first harmonic by that of the second harmonic in a B-scan interferogram directly gives the scaling coefficient. It greatly simplifies the determination of the magnitude ratio between the two harmonics without the need of third harmonic and cumbersome iterative calculations. The inverse fast Fourier transform of the complex-valued interferogram constructed with the scaling coefficient, first and second harmonics yields a full-range OCT image. Experimental results confirm the effectiveness of the proposed achromatic two-harmonic technique for suppressing the mirror artifacts in SD-OCT images.

Dynamic Chirp Control and Pulse Compression for Attosecond High-Order Harmonic Emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng Yinghui; Zeng Zhinan; Zou Pu

2009-07-24

We propose a scheme to compensate dynamically the intrinsic chirp of the attosecond harmonic pulses. By adding a weak second harmonic laser field to the driving laser field, the chirp compensation can be varied from the negative to the positive continuously by simply adjusting the relative time delay between the two-color pulses. Using this technique, the compensation of the negative chirp in harmonic emission is demonstrated experimentally for the first time and the nearly transform-limited attosecond pulse trains are obtained.

Blind separation of overlapping partials in harmonic musical notes using amplitude and phase reconstruction

NASA Astrophysics Data System (ADS)

de León, Jesús Ponce; Beltrán, José Ramón

2012-12-01

In this study, a new method of blind audio source separation (BASS) of monaural musical harmonic notes is presented. The input (mixed notes) signal is processed using a flexible analysis and synthesis algorithm (complex wavelet additive synthesis, CWAS), which is based on the complex continuous wavelet transform. When the harmonics from two or more sources overlap in a certain frequency band (or group of bands), a new technique based on amplitude similarity criteria is used to obtain an approximation to the original partial information. The aim is to show that the CWAS algorithm can be a powerful tool in BASS. Compared with other existing techniques, the main advantages of the proposed algorithm are its accuracy in the instantaneous phase estimation, its synthesis capability and that the only input information needed is the mixed signal itself. A set of synthetically mixed monaural isolated notes have been analyzed using this method, in eight different experiments: the same instrument playing two notes within the same octave and two harmonically related notes (5th and 12th intervals), two different musical instruments playing 5th and 12th intervals, two different instruments playing non-harmonic notes, major and minor chords played by the same musical instrument, three different instruments playing non-harmonically related notes and finally the mixture of a inharmonic instrument (piano) and one harmonic instrument. The results obtained show the strength of the technique.

Measuring the molecular second hyperpolarizability in absorptive solutions by the third harmonic generation ratio technique.

PubMed

Tokarz, Danielle; Cisek, Richard; Prent, Nicole; Fekl, Ulrich; Barzda, Virginijus

2012-11-28

Measurement of the second hyperpolarizability (γ) values of compounds can provide insight into the molecular structural requirements for enhancement of third harmonic generation (THG) signal. A convenient method for measuring the γ of compounds in solutions was developed by implementing the THG ratio method which is based on measuring the THG intensity from two interfaces using a nonlinear optical microscope while accounting for the refractive index of solutions at the fundamental and third harmonic wavelengths. We demonstrated that the difference in refractive index at both wavelengths strongly influenced the calculation of γ values when compounds have absorption near the third harmonic or fundamental wavelength. To this end, a refractometer with the wavelength tuning range from UV to near IR was constructed, and the measured refractive indices were used to extract the γ values. The γ values of carotenoids and chlorophylls found in photosynthetic pigment-protein complexes were explored. Large differences in the refractive index at third harmonic and fundamental wavelengths for chlorophylls result in γ values that are more than two orders of magnitude larger than γ values for carotenoids as well as the sign of chlorophylls'γ values is negative while carotenoids have positive γ values. Copyright © 2012 Elsevier B.V. All rights reserved.

Harmonic regression based multi-temporal cloud filtering algorithm for Landsat 8

NASA Astrophysics Data System (ADS)

Joshi, P.

2015-12-01

Landsat data archive though rich is seen to have missing dates and periods owing to the weather irregularities and inconsistent coverage. The satellite images are further subject to cloud cover effects resulting in erroneous analysis and observations of ground features. In earlier studies the change detection algorithm using statistical control charts on harmonic residuals of multi-temporal Landsat 5 data have been shown to detect few prominent remnant clouds [Brooks, Evan B., et al, 2014]. So, in this work we build on this harmonic regression approach to detect and filter clouds using a multi-temporal series of Landsat 8 images. Firstly, we compute the harmonic coefficients using the fitting models on annual training data. This time series of residuals is further subjected to Shewhart X-bar control charts which signal the deviations of cloud points from the fitted multi-temporal fourier curve. For the process with standard deviation σ we found the second and third order harmonic regression with a x-bar chart control limit [Lσ] ranging between [0.5σ < Lσ < σ] as most efficient in detecting clouds. By implementing second order harmonic regression with successive x-bar chart control limits of L and 0.5 L on the NDVI, NDSI and haze optimized transformation (HOT), and utilizing the seasonal physical properties of these parameters, we have designed a novel multi-temporal algorithm for filtering clouds from Landsat 8 images. The method is applied to Virginia and Alabama in Landsat8 UTM zones 17 and 16 respectively. Our algorithm efficiently filters all types of cloud cover with an overall accuracy greater than 90%. As a result of the multi-temporal operation and the ability to recreate the multi-temporal database of images using only the coefficients of the fourier regression, our algorithm is largely storage and time efficient. The results show a good potential for this multi-temporal approach for cloud detection as a timely and targeted solution for the Landsat 8

Second Harmonic Hectometric Radio Emission at Jupiter

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Gurnett, D. A.; Groene, J. B.

1998-01-01

Galileo has been in orbit around Jupiter since December 1995. The plasma wave instrument on board the spacecraft has occasionally detected a rotationally modulated attenuation band in the hectometric (HOM) emission that most likely is due to scattering of the radiation from density fluctuations along the Io L-shell, as reported earlier. The occurrence of the attenuation band is likely to be dependent on Io activity and the presence of density scattering centers along the Io-L-shell as well as the location of the source region. Some of the attenuation bands show clear indications of second harmonic emission. Without polarization measurements, it is difficult to place constraints on the local generation conditions based on the cyclotron maser instability, but the results imply that second harmonic emission could be present in the decametric (DAM) radiation as well. A survey of the data has revealed about 30 examples of second harmonic HOM.

Second Harmonic Hectometric Radio Emission at Jupiter

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Gurnett, D. A.; Groene, J. B.

1998-01-01

Galileo has been in orbit around Jupiter since December 1995. The plasma wave instrument on board the spacecraft has occasionally detected a rotationally modulated attenuation band in the hectometric (HOM) emission that most likely is due to scattering of the radiation from density fluctuations along the Io L-shell, as reported earlier. The occurrence of the attenuation band is likely to be dependent on Io activity and the presence of density scattering centers along the Io L-shell as well as the location of the source region. Some of the attenuation bands show clear indications of second harmonic emission. Without polarization measurements, it is difficult to place constraints on the local generation conditions based on the cyclotron maser instability, but the results imply that second harmonic emission could be present in the decametric (DAM) radiation as well. A survey of the data has revealed about 30 examples of second harmonic HOM.

Temperature dependence of acoustic harmonics generated by nonlinear ultrasound beam propagation in ex vivo tissue and tissue-mimicking phantoms.

PubMed

Maraghechi, Borna; Kolios, Michael C; Tavakkoli, Jahan

2015-01-01

Hyperthermia is a cancer treatment technique that could be delivered as a stand-alone modality or in conjunction with chemotherapy or radiation therapy. Noninvasive and real-time temperature monitoring of the heated tissue improves the efficacy and safety of the treatment. A temperature-sensitive acoustic parameter is required for ultrasound-based thermometry. In this paper the amplitude and the energy of the acoustic harmonics of the ultrasound backscattered signal are proposed as suitable parameters for noninvasive ultrasound thermometry. A commercial high frequency ultrasound imaging system was used to generate and detect acoustic harmonics in tissue-mimicking gel phantoms and ex vivo bovine muscle tissues. The pressure amplitude and the energy content of the backscattered fundamental frequency (p1 and E1), the second (p2 and E2) and the third (p3 and E3) harmonics were detected in pulse-echo mode. Temperature was increased from 26° to 46 °C uniformly through both samples. The amplitude and the energy content of the harmonics and their ratio were measured and analysed as a function of temperature. The average p1, p2 and p3 increased by 69%, 100% and 283%, respectively as the temperature was elevated from 26° to 46 °C in tissue samples. In the same experiment the average E1, E2 and E3 increased by 163%, 281% and 2257%, respectively. A similar trend was observed in tissue-mimicking gel phantoms. The findings suggest that the harmonics generated due to nonlinear ultrasound beam propagation are highly sensitive to temperature and could potentially be used for noninvasive ultrasound tissue thermometry.

Determination of collagen fibril size via absolute measurements of second-harmonic generation signals

NASA Astrophysics Data System (ADS)

Bancelin, Stéphane; Aimé, Carole; Gusachenko, Ivan; Kowalczuk, Laura; Latour, Gaël; Coradin, Thibaud; Schanne-Klein, Marie-Claire

2014-09-01

The quantification of collagen fibril size is a major issue for the investigation of pathological disorders associated with structural defects of the extracellular matrix. Second-harmonic generation microscopy is a powerful technique to characterize the macromolecular organization of collagen in unstained biological tissues. Nevertheless, due to the complex coherent building of this nonlinear optical signal, it has never been used to measure fibril diameter so far. Here we report absolute measurements of second-harmonic signals from isolated fibrils down to 30 nm diameter, via implementation of correlative second-harmonic-electron microscopy. Moreover, using analytical and numerical calculations, we demonstrate that the high sensitivity of this technique originates from the parallel alignment of collagen triple helices within fibrils and the subsequent constructive interferences of second-harmonic radiations. Finally, we use these absolute measurements as a calibration for ex vivo quantification of fibril diameter in the Descemet’s membrane of a diabetic rat cornea.

Simultaneous Measurements of Harmonic Waves at Fatigue-Cracked Interfaces

NASA Astrophysics Data System (ADS)

Hyunjo, Jeong; Dan, Barnard

2011-08-01

Nonlinear harmonic waves generated at cracked interfaces are investigated theoretically and experimentally. A compact tension specimen is fabricated and the amplitude of the transmitted wave is analyzed as a function of position along the fatigued crack surface. In order to measure as many nonlinear harmonic components as possible, broadband lithium niobate (LiNbO3) transducers are employed together with a calibration technique for making absolute amplitude measurements with fluid-coupled receiving transducers. Cracked interfaces are shown to generate high acoustic nonlinearities, which are manifested as harmonics in the power spectrum of the received signal. The first subharmonic f/2 and the second harmonic 2f waves are found to be dominant nonlinear components for an incident toneburst signal of frequency f. To explain the observed nonlinear behavior, a partially closed crack is modeled by planar half interfaces that can account for crack parameters, such as crack opening displacement and crack surface conditions. The simulation results show reasonable agreement with the experimental results.

Approach for discrimination and quantification of electroactive species: kinetics difference revealed by higher harmonics of Fourier transformed sinusoidal voltammetry.

PubMed

Fang, Yishan; Huang, Xinjian; Wang, Lishi

2015-01-06

Discrimination and quantification of electroactive species are traditionally realized by a potential difference which is mainly determined by thermodynamics. However, the resolution of this approach is limited to tens of millivolts. In this paper, we described an application of Fourier transformed sinusoidal voltammetry (FT-SV) that provides a new approach for discrimination and quantitative evaluation of electroactive species, especially thermodynamic similar ones. Numerical simulation indicates that electron transfer kinetics difference between electroactive species can be revealed by the phase angle of higher order harmonics of FT-SV, and the difference can be amplified order by order. Thus, even a very subtle kinetics difference can be amplified to be distinguishable at a certain order of harmonics. This method was verified with structurally similar ferrocene derivatives which were chosen as the model systems. Although these molecules have very close redox potential (<10 mV), discrimination and selective detection were achieved by as high as the thirteenth harmonics. The results demonstrated the feasibility and reliability of the method. It was also implied that the combination of the traditional thermodynamic method and this kinetics method can form a two-dimension resolved detection method, and it has the potential to extend the resolution of voltammetric techniques to a new level.

4D Hyperspherical Harmonic (HyperSPHARM) Representation of Multiple Disconnected Brain Subcortical Structures

PubMed Central

Hosseinbor, A. Pasha; Chung, Moo K.; Schaefer, Stacey M.; van Reekum, Carien M.; Peschke-Schmitz, Lara; Sutterer, Matt; Alexander, Andrew L.; Davidson, Richard J.

2014-01-01

We present a novel surface parameterization technique using hyperspherical harmonics (HSH) in representing compact, multiple, disconnected brain subcortical structures as a single analytic function. The proposed hyperspherical harmonic representation (HyperSPHARM) has many advantages over the widely used spherical harmonic (SPHARM) parameterization technique. SPHARM requires flattening 3D surfaces to 3D sphere which can be time consuming for large surface meshes, and can’t represent multiple disconnected objects with single parameterization. On the other hand, HyperSPHARM treats 3D object, via simple stereographic projection, as a surface of 4D hypersphere with extremely large radius, hence avoiding the computationally demanding flattening process. HyperSPHARM is shown to achieve a better reconstruction with only 5 basis compared to SPHARM that requires more than 441. PMID:24505716

Harmonics distribution of iron oxide nanoparticles solutions under diamagnetic background

NASA Astrophysics Data System (ADS)

Saari, Mohd Mawardi; Che Lah, Nurul Akmal; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji

2018-04-01

The static and dynamic magnetizations of low concentrated multi-core iron oxide nanoparticles solutions were investigated by a specially developed high-Tc Superconducting Quantum Interference Device (SQUID) magnetometer. The size distribution of iron oxide cores was determined from static magnetization curves concerning different concentrations. The simulated harmonics distribution was compared to the experimental results. Effect of the diamagnetic background from carrier liquid to harmonics distribution was investigated with respect to different intensity and position of peaks in the magnetic moment distribution using a numerical simulation. It was found that the diamagnetic background from carrier liquid of iron oxide nanoparticles affected the harmonics distribution as their concentration decreased and depending on their magnetic moment distribution. The first harmonic component was susceptible to the diamagnetic contribution of carrier liquid when the concentration was lower than 24 μg/ml. The second and third harmonics were affected when the peak position of magnetic moment distribution was smaller than m = 10-19 Am2 and the concentration was 10 ng/ml. A highly sensitive detection up to sub-nanogram of iron oxide nanoparticles in solutions can be achieved by utilizing second and third harmonic components.

Quantitative biomarkers of colonic dysplasia based on intrinsic second-harmonic generation signal

NASA Astrophysics Data System (ADS)

Zhuo, Shuangmu; Zhu, Xiaoqin; Wu, Guizhu; Chen, Jianxin; Xie, Shusen

2011-12-01

Most colorectal cancers arise from dysplastic lesions, such as adenomatous polyps, and these lesions are difficult to be detected by the current endoscopic screening approaches. Here, we present the use of an intrinsic second-harmonic generation (SHG) signal as a novel means to differentiate between normal and dysplastic human colonic tissues. We find that the SHG signal can quantitatively identify collagen change associated with colonic dysplasia that is indiscernible by conventional pathologic techniques. By comparing normal with dysplastic mucosa, there were significant differences in collagen density and collagen fiber direction, providing substantial potential to become quantitative intrinsic biomarkers for in vivo clinical diagnosis of colonic dysplasia.

Low complexity feature extraction for classification of harmonic signals

NASA Astrophysics Data System (ADS)

William, Peter E.

In this dissertation, feature extraction algorithms have been developed for extraction of characteristic features from harmonic signals. The common theme for all developed algorithms is the simplicity in generating a significant set of features directly from the time domain harmonic signal. The features are a time domain representation of the composite, yet sparse, harmonic signature in the spectral domain. The algorithms are adequate for low-power unattended sensors which perform sensing, feature extraction, and classification in a standalone scenario. The first algorithm generates the characteristic features using only the duration between successive zero-crossing intervals. The second algorithm estimates the harmonics' amplitudes of the harmonic structure employing a simplified least squares method without the need to estimate the true harmonic parameters of the source signal. The third algorithm, resulting from a collaborative effort with Daniel White at the DSP Lab, University of Nebraska-Lincoln, presents an analog front end approach that utilizes a multichannel analog projection and integration to extract the sparse spectral features from the analog time domain signal. Classification is performed using a multilayer feedforward neural network. Evaluation of the proposed feature extraction algorithms for classification through the processing of several acoustic and vibration data sets (including military vehicles and rotating electric machines) with comparison to spectral features shows that, for harmonic signals, time domain features are simpler to extract and provide equivalent or improved reliability over the spectral features in both the detection probabilities and false alarm rate.

Evaluation of change detection techniques for monitoring coastal zone environments

NASA Technical Reports Server (NTRS)

Weismiller, R. A. (Principal Investigator); Kristof, S. J.; Scholz, D. K.; Anuta, P. E.; Momin, S. M.

1977-01-01

The author has identified the following significant results. Four change detection techniques were designed and implemented for evaluation: (1) post classification comparison change detection, (2) delta data change detection, (3) spectral/temporal change classification, and (4) layered spectral/temporal change classification. The post classification comparison technique reliably identified areas of change and was used as the standard for qualitatively evaluating the other three techniques. The layered spectral/temporal change classification and the delta data change detection results generally agreed with the post classification comparison technique results; however, many small areas of change were not identified. Major discrepancies existed between the post classification comparison and spectral/temporal change detection results.

Generation of vacuum ultraviolet radiation by intracavity high-harmonic generation toward state detection of single trapped ions

NASA Astrophysics Data System (ADS)

Wakui, Kentaro; Hayasaka, Kazuhiro; Ido, Tetsuya

2014-12-01

Vacuum ultraviolet (VUV) radiation around 159 nm is obtained toward direct excitation of a single trapped ion. An efficient fluoride-based VUV output coupler is employed for intracavity high-harmonic generation of a Ti:S oscillator. Using this coupler, where we measured its reflectance to be about 90 %, an average power reaching 6.4 W is coupled out from a modest fundamental power of 650 mW. When a single comb component out of 1.9 10 teeth is resonant to the atomic transition, 100s of fluorescence photons per second will be detectable under a realistic condition.

Three-dimensional structural imaging of starch granules by second-harmonic generation circular dichroism.

PubMed

Zhuo, G-Y; Lee, H; Hsu, K-J; Huttunen, M J; Kauranen, M; Lin, Y-Y; Chu, S-W

2014-03-01

Chirality is one of the most fundamental and essential structural properties of biological molecules. Many important biological molecules including amino acids and polysaccharides are intrinsically chiral. Conventionally, chiral species can be distinguished by interaction with circularly polarized light, and circular dichroism is one of the best-known approaches for chirality detection. As a linear optical process, circular dichroism suffers from very low signal contrast and lack of spatial resolution in the axial direction. It has been demonstrated that by incorporating nonlinear interaction with circularly polarized excitation, second-harmonic generation circular dichroism can provide much higher signal contrast. However, previous circular dichroism and second-harmonic generation circular dichroism studies are mostly limited to probe chiralities at surfaces and interfaces. It is known that second-harmonic generation, as a second-order nonlinear optical effect, provides excellent optical sectioning capability when combined with a laser-scanning microscope. In this work, we combine the axial resolving power of second-harmonic generation and chiral sensitivity of second-harmonic generation circular dichroism to realize three-dimensional chiral detection in biological tissues. Within the point spread function of a tight focus, second-harmonic generation circular dichroism could arise from the macroscopic supramolecular packing as well as the microscopic intramolecular chirality, so our aim is to clarify the origins of second-harmonic generation circular dichroism response in complicated three-dimensional biological systems. The sample we use is starch granules whose second-harmonic generation-active molecules are amylopectin with both microscopic chirality due to its helical structure and macroscopic chirality due to its crystallized packing. We found that in a starch granule, the second-harmonic generation for right-handed circularly polarized excitation is

Detection technique of targets for missile defense system

NASA Astrophysics Data System (ADS)

Guo, Hua-ling; Deng, Jia-hao; Cai, Ke-rong

2009-11-01

Ballistic missile defense system (BMDS) is a weapon system for intercepting enemy ballistic missiles. It includes ballistic-missile warning system, target discrimination system, anti-ballistic-missile guidance systems, and command-control communication system. Infrared imaging detection and laser imaging detection are widely used in BMDS for surveillance, target detection, target tracking, and target discrimination. Based on a comprehensive review of the application of target-detection techniques in the missile defense system, including infrared focal plane arrays (IRFPA), ground-based radar detection technology, 3-dimensional imaging laser radar with a photon counting avalanche photodiode (APD) arrays and microchip laser, this paper focuses on the infrared and laser imaging detection techniques in missile defense system, as well as the trends for their future development.

The Coupled Harmonic Oscillator: Not Just for Seniors Anymore.

ERIC Educational Resources Information Center

Preyer, Norris W.

1996-01-01

Presents experiments that use Microcomputer Based Laboratory (MBL) techniques to enable freshmen physics students to investigate complex systems, such as nonlinear oscillators or coupled harmonic oscillators, at a level appropriate for an independent project. (JRH)

Harmonic elastic inclusions in the presence of point moment

NASA Astrophysics Data System (ADS)

Wang, Xu; Schiavone, Peter

2017-12-01

We employ conformal mapping techniques to design harmonic elastic inclusions when the surrounding matrix is simultaneously subjected to remote uniform stresses and a point moment located at an arbitrary position in the matrix. Our analysis indicates that the uniform and hydrostatic stress field inside the inclusion as well as the constant hoop stress along the entire inclusion-matrix interface (on the matrix side) are independent of the action of the point moment. In contrast, the non-elliptical shape of the harmonic inclusion depends on both the remote uniform stresses and the point moment.

Assessing the Rayleigh Intensity Remote Leak Detection Technique

NASA Technical Reports Server (NTRS)

Clements, Sandra

2001-01-01

Remote sensing technologies are being considered for efficient, low cost gas leak detection. An exploratory project to identify and evaluate remote sensing technologies for application to gas leak detection is underway. During Phase 1 of the project, completed last year, eleven specific techniques were identified for further study. One of these, the Rayleigh Intensity technique, would make use of changes in the light scattered off of gas molecules to detect and locate a leak. During the 10-week Summer Faculty Fellowship Program, the scatter of light off of gas molecules was investigated. The influence of light scattered off of aerosols suspended in the atmosphere was also examined to determine if this would adversely affect leak detection. Results of this study indicate that in unconditioned air, it will be difficult, though perhaps not impossible, to distinguish between a gas leak and natural variations in the aerosol content of the air. Because information about the particle size distribution in clean room environments is incomplete, the applicability in clean rooms is uncertain though more promising than in unconditioned environments. It is suggested that problems caused by aerosols may be overcome by using the Rayleigh Intensity technique in combination with another remote sensing technique, the Rayleigh Doppler technique.

Spectrally resolved single-shot wavefront sensing of broadband high-harmonic sources

NASA Astrophysics Data System (ADS)

Freisem, L.; Jansen, G. S. M.; Rudolf, D.; Eikema, K. S. E.; Witte, S.

2018-03-01

Wavefront sensors are an important tool to characterize coherent beams of extreme ultraviolet radiation. However, conventional Hartmann-type sensors do not allow for independent wavefront characterization of different spectral components that may be present in a beam, which limits their applicability for intrinsically broadband high-harmonic generation (HHG) sources. Here we introduce a wavefront sensor that measures the wavefronts of all the harmonics in a HHG beam in a single camera exposure. By replacing the mask apertures with transmission gratings at different orientations, we simultaneously detect harmonic wavefronts and spectra, and obtain sensitivity to spatiotemporal structure such as pulse front tilt as well. We demonstrate the capabilities of the sensor through a parallel measurement of the wavefronts of 9 harmonics in a wavelength range between 25 and 49 nm, with up to lambda/32 precision.

Harmonics analysis of the photonic time stretch system.

PubMed

Mei, Yuan; Xu, Boyu; Chi, Hao; Jin, Tao; Zheng, Shilie; Jin, Xiaofeng; Zhang, Xianmin

2016-09-10

Photonic time stretch (PTS) has been intensively investigated in recent decades due to its potential application to ultra-wideband analog-to-digital conversion. A high-speed analog signal can be captured by an electronic analog-to-digital converter (ADC) with the help of the PTS technique, which slows down the speed of signal in the photonic domain. Unfortunately, the process of the time stretch is not linear due to the nonlinear modulation of the electro-optic intensity modulator in the PTS system, which means the undesired harmonics distortion. In this paper, we present an exact analytical model to fully characterize the harmonics generation in the PTS systems for the first time, to the best of our knowledge. We obtain concise and closed-form expressions for all harmonics of the PTS system with either a single-arm Mach-Zehnder modulator (MZM) or a push-pull MZM. The presented model can largely simplify the PTS system design and the system parameters estimation, such as system bandwidth, harmonics power, time-bandwidth product, and dynamic range. The correctness of the mathematic model is verified by the numerical and experimental results.

High-harmonic spectroscopy of oriented OCS molecules: emission of even and odd harmonics.

PubMed

Kraus, P M; Rupenyan, A; Wörner, H J

2012-12-07

We study the emission of even and odd high-harmonic orders from oriented OCS molecules. We use an intense, nonresonant femtosecond laser pulse superimposed with its phase-controlled second harmonic field to impulsively align and orient a dense sample of molecules from which we subsequently generate high-order harmonics. The even harmonics appear around the full revivals of the rotational dynamics. We demonstrate perfect coherent control over their intensity through the subcycle delay of the two-color fields. The odd harmonics are insensitive to the degree of orientation, but modulate with the degree of axis alignment, in agreement with calculated photorecombination dipole moments. We further compare the shape of the even and odd harmonic spectra with our calculations and determine the degree of orientation.

Early detection of dental caries using photoacoustics

NASA Astrophysics Data System (ADS)

Kim, K.; Witte, R.; Koh, I.; Ashkenazi, S.; O'Donnell, M.

2006-02-01

For decades, visual, tactile and radiographic examinations have been the standard for diagnosing caries. Nonetheless, the extent of variation in the diagnosis of dental caries is substantial among dental practitioners using these traditional techniques. Therefore, a more reliable standard for detecting incipient caries would be desirable. Using photoacoustics, near-infrared (NIR) optical contrast between sound and carious dental tissues can be relatively easily and accurately detected at ultrasound resolution. In this paper, a pulsed laser (Nd:YAG, Quanta-Ray) was used to probe extracted human molars at different disease stages determined from periapical radiographs. Both fundamental (1064nm) and first harmonic (532nm) pulses (15ns pulse length, 100mJ at fundamental and 9mJ at first harmonic , 10Hz pulse repetition rate) were used to illuminate the occlusal surface of tooth samples placed in a water tank. The photoacoustic signal was recorded with an unfocused wideband single-element piezoelectric transducer (centered at 12 MHz, bandwidth 15 MHz) positioned at small angle (less than 30 degrees) to the laser beam close to the occlusal surface. At the fundamental wavelength, total photoacoustic energy increases from normal to incipient stage disease by as much as a factor of 10. Differences between photoacoustic energy at the fundamental and first harmonic wavelength further indicate spectral absorption changes of the underlying structure with disease progression. Using a focused laser beam, an extracted molar with suspected incipient caries was scanned along the occulusal surface to help localize the caries inside enamel and dentin. The significantly increasing photoacoustic signal at a specific scan line both at fundamental and first harmonic indicates the local development of the incipient caries. The photoacoustic results compare well with visual inspection after layer by layer dissection. Preliminary results demonstrate the feasibility of detecting incipient

Three-port laparoscopic cholecystectomy by harmonic dissection without cystic duct and artery clipping.

PubMed

Tebala, Giovanni D

2006-05-01

The technique of laparoscopic cholecystectomy (LC) still has areas of refinements. To decrease the number of ports, a cannula may be replaced by a percutaneous suture suspension of the gallbladder. The risk of tissue injury caused by repeat blind extraction and insertion of various instruments in and out of the abdomen may be decreased by the use of the multipurpose harmonic dissector. One hundred consecutive patients with symptomatic cholelithiasis underwent 3-port LC entirely performed by harmonic dissector without cystic duct and artery clipping. In 8 cases, a fourth trocar was necessary. In 2 cases, the cystic duct was clipped after an unsafe ultrasound sealing. In 1 case, continuous bleeding from the liver required the use of diathermy. No common bile duct injury was registered. The 3-port harmonic LC is a feasible, effective, and safe technique.

Anisotropic high-harmonic generation in bulk crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Yong Sing; Reis, David A.; Ghimire, Shambhu

2016-11-21

The microscopic valence electron density determines the optical, electronic, structural and thermal properties of materials. However, current techniques for measuring this electron charge density are limited: for example, scanning tunnelling microscopy is confined to investigations at the surface, and electron diffraction requires very thin samples to avoid multiple scattering. Therefore, an optical method is desirable for measuring the valence charge density of bulk materials. Since the discovery of high-harmonic generation (HHG) in solids, there has been growing interest in using HHG to probe the electronic structure of solids. Here, using single-crystal MgO, we demonstrate that high-harmonic generation in solids ismore » sensitive to interatomic bonding. We find that harmonic efficiency is enhanced (diminished) for semi-classical electron trajectories that connect (avoid) neighbouring atomic sites in the crystal. Finally, these results indicate the possibility of using materials’ own electrons for retrieving the interatomic potential and thus the valence electron density, and perhaps even wavefunctions, in an all-optical setting.« less

A Novel Technique to Detect Code for SAC-OCDMA System

NASA Astrophysics Data System (ADS)

Bharti, Manisha; Kumar, Manoj; Sharma, Ajay K.

2018-04-01

The main task of optical code division multiple access (OCDMA) system is the detection of code used by a user in presence of multiple access interference (MAI). In this paper, new method of detection known as XOR subtraction detection for spectral amplitude coding OCDMA (SAC-OCDMA) based on double weight codes has been proposed and presented. As MAI is the main source of performance deterioration in OCDMA system, therefore, SAC technique is used in this paper to eliminate the effect of MAI up to a large extent. A comparative analysis is then made between the proposed scheme and other conventional detection schemes used like complimentary subtraction detection, AND subtraction detection and NAND subtraction detection. The system performance is characterized by Q-factor, BER and received optical power (ROP) with respect to input laser power and fiber length. The theoretical and simulation investigations reveal that the proposed detection technique provides better quality factor, security and received power in comparison to other conventional techniques. The wide opening of eye in case of proposed technique also proves its robustness.

Optical harmonic generator

DOEpatents

Summers, M.A.; Eimerl, D.; Boyd, R.D.

1982-06-10

A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The extraordinary or e directions of the crystal elements are oriented in the integral assembly to be in quadrature (90/sup 0/). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude o and e components. For a third-harmonic generation, the input fundamental wave has o and e components whose amplitudes are in a ratio of 2:1 (o:e reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10/sup 0/. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axeses (o).

Optical harmonic generator

DOEpatents

Summers, Mark A.; Eimerl, David; Boyd, Robert D.

1985-01-01

A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The "extraordinary" or "e" directions of the crystal elements are oriented in the integral assembly to be in quadrature (90.degree.). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude "o" and "e" components. For a third-harmonic generation, the input fundamental wave has "o" and "e" components whose amplitudes are in a ratio of 2:1 ("o":"e" reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10.degree.. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axes ("o").

Can even-order laser harmonics exhibited by Bohmian trajectories in symmetric potentials be observed?

PubMed

Peatross, J; Johansen, J

2014-01-13

Strong-field laser-atom interactions provide extreme conditions that may be useful for investigating the de Broglie-Bohm quantum interpretation. Bohmian trajectories representing bound electrons in individual atoms exhibit both even and odd harmonic motion when subjected to a strong external laser field. The phases of the even harmonics depend on the random initial positions of the trajectories within the wave function, making the even harmonics incoherent. In contrast, the phases of odd harmonics remain for the most part coherent regardless of initial position. Under the conjecture that a Bohmian point particle plays the role of emitter, this suggests an experiment to determine whether both even and odd harmonics are produced at the atomic level. Estimates suggest that incoherent emission of even harmonics may be detectable out the side of an intense laser focus interacting with a large number of atoms.

A novel power harmonic analysis method based on Nuttall-Kaiser combination window double spectrum interpolated FFT algorithm

NASA Astrophysics Data System (ADS)

Jin, Tao; Chen, Yiyang; Flesch, Rodolfo C. C.

2017-11-01

Harmonics pose a great threat to safe and economical operation of power grids. Therefore, it is critical to detect harmonic parameters accurately to design harmonic compensation equipment. The fast Fourier transform (FFT) is widely used for electrical popular power harmonics analysis. However, the barrier effect produced by the algorithm itself and spectrum leakage caused by asynchronous sampling often affects the harmonic analysis accuracy. This paper examines a new approach for harmonic analysis based on deducing the modifier formulas of frequency, phase angle, and amplitude, utilizing the Nuttall-Kaiser window double spectrum line interpolation method, which overcomes the shortcomings in traditional FFT harmonic calculations. The proposed approach is verified numerically and experimentally to be accurate and reliable.

Digital Detection and Processing of Multiple Quadrature Harmonics for EPR Spectroscopy

PubMed Central

Ahmad, R.; Som, S.; Kesselring, E.; Kuppusamy, P.; Zweier, J.L.; Potter, L.C.

2010-01-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. PMID:20971667

Harmonic multiplication using resonant tunneling

NASA Technical Reports Server (NTRS)

Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Correa, C. A.

1988-01-01

This paper demonstrates the use of resonant-tunneling diodes as varistors for harmonic multiplication. It is shown that efficient odd-harmonic conversion is possible and that even harmonics do not appear because of the antisymmetry of the current-voltage (I-V) curve. It is also shown that, with the proper choice of resonant-tunneling structure and pump amplitude, most of the harmonic output power can be confined to a single odd-harmonic frequency. Fifth-harmonic multiplication was demonstrated with an output at 21.75 GHz and a power conversion efficiency of 0.5 percent, and a fifth-harmonic efficiency of 2.7 percent was achieved in a circuit simulation using an improved I-V curve.

Even-order harmonic cancellation for off-quadrature biased Mach-Zehnder modulator with improved RF metrics using dual wavelength inputs and dual outputs.

PubMed

Devgan, Preetpaul S; Diehl, John F; Urick, Vincent J; Sunderman, Christopher E; Williams, Keith J

2009-05-25

We present a technique using a dual-output Mach-Zehnder modulator (MZM) with two wavelength inputs, one operating at low-bias and the other operating at high-bias, in order to cancel unwanted even-order harmonics in analog optical links. By using a dual-output MZM, this technique allows for two suppressed optical carriers to be transmitted to the receiver. Combined with optical amplification and balanced differential detection, the RF power of the fundamental is increased by 2 dB while the even-order harmonic is reduced by 47 dB, simultaneously. The RF noise figure and third-order spurious-free dynamic range (SFDR(3)) are improved by 5.4 dB and 3.6 dB, respectively. Using a wavelength sensitive, low V(pi) MZM allows the two wavelengths to be within 5.5 nm of each other for a frequency band from 10 MHz to 100 MHz and 10 nm for 1 GHz.

Improved Continuous-Time Higher Harmonic Control Using Hinfinity Methods

NASA Astrophysics Data System (ADS)

Fan, Frank H.

The helicopter is a versatile aircraft that can take-off and land vertically, hover efficiently, and maneuver in confined space. This versatility is enabled by the main rotor, which also causes undesired harmonic vibration during operation. This unwanted vibration has a negative impact on the practicality of the helicopter and also increases its operational cost. Passive control techniques have been applied to helicopter vibration suppression, but these methods are generally heavy and are not robust to changes in operating conditions. Feedback control offers the advantages of robustness and potentially higher performance over passive control techniques, and amongst the various feedback schemes, Shaw's higher harmonic control algorithm has been shown to be an effective method for attenuating harmonic disturbance in helicopters. In this thesis, the higher harmonic disturbance algorithm is further developed to achieve improved performance. One goal in this thesis is to determine the importance of periodicity in the helicopter rotor dynamics for control synthesis. Based on the analysis of wind tunnel data and simulation results, we conclude the helicopter rotor can be modeled reasonably well as linear and time-invariant for control design purposes. Modeling the helicopter rotor as linear time-invariant allows us to apply linear control theory concepts to the higher harmonic control problem. Another goal in this thesis is to find the limits of performance in harmonic disturbance rejection. To achieve this goal, we first define the metrics to measure the performance of the controller in terms of response speed and robustness to changes in the plant dynamics. The performance metrics are incorporated into an Hinfinity control problem. For a given plant, the resulting Hinfinity controller achieves the maximum performance, thus allowing us to identify the performance limitation in harmonic disturbance rejection. However, the Hinfinity controllers are of high order, and may

Characterization of ultrafast devices using novel optical techniques

NASA Astrophysics Data System (ADS)

Ali, Md Ershad

Optical techniques have been extensively used to examine the high frequency performance of a number of devices including High Electron Mobility Transistors (HEMTs), Heterojunction Bipolar Phototransistors (HPTs) and Low Temperature GaAs (LT-GaAs) Photoconductive Switches. To characterize devices, frequency and time domain techniques, namely optical heterodyning and electro-optic sampling, having measurement bandwidths in excess of 200 GHz, were employed. Optical mixing in three-terminal devices has been extended for the first time to submillimeter wave frequencies. Using a new generation of 50-nm gate pseudomorphic InP-based HEMTs, optically mixed signals were detected to 552 GHz with a signal-to-noise ratio of approximately 5 dB. To the best of our knowledge, this is the highest frequency optical mixing obtained in three- terminal devices to date. A novel harmonic three-wave detection scheme was used for the detection of the optically generated signals. The technique involved downconversion of the signal in the device by the second harmonic of a gate-injected millimeter wave local oscillator. Measurements were also conducted up to 212 GHz using direct optical mixing and up to 382 GHz using a fundamental three-wave detection scheme. New interesting features in the bias dependence of the optically mixed signals have been reported. An exciting novel development from this work is the successful integration of near-field optics with optical heterodyning. The technique, called near-field optical heterodyning (NFOH), allows for extremely localized injection of high-frequency stimulus to any arbitrary point of an ultrafast device or circuit. Scanning the point of injection across the sample provides details of the high frequency operation of the device with high spatial resolution. For the implementation of the technique, fiber-optic probes with 100 nm apertures were fabricated. A feedback controlled positioning system was built for accurate placement and scanning of the

The detection of bulk explosives using nuclear-based techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgado, R.E.; Gozani, T.; Seher, C.C.

1988-01-01

In 1986 we presented a rationale for the detection of bulk explosives based on nuclear techniques that addressed the requirements of civil aviation security in the airport environment. Since then, efforts have intensified to implement a system based on thermal neutron activation (TNA), with new work developing in fast neutron and energetic photon reactions. In this paper we will describe these techniques and present new results from laboratory and airport testing. Based on preliminary results, we contended in our earlier paper that nuclear-based techniques did provide sufficiently penetrating probes and distinguishable detectable reaction products to achieve the FAA operational goals;more » new data have supported this contention. The status of nuclear-based techniques for the detection of bulk explosives presently under investigation by the US Federal Aviation Administration (FAA) is reviewed. These include thermal neutron activation (TNA), fast neutron activation (FNA), the associated particle technique, nuclear resonance absorption, and photoneutron activation. The results of comprehensive airport testing of the TNA system performed during 1987-88 are summarized. From a technical point of view, nuclear-based techniques now represent the most comprehensive and feasible approach for meeting the operational criteria of detection, false alarms, and throughput. 9 refs., 5 figs., 2 tabs.« less

The Technology of Suppressing Harmonics with Complex Neural Network is Applied to Microgrid

NASA Astrophysics Data System (ADS)

Zhang, Jing; Li, Zhan-Ying; Wang, Yan-ping; Li, Yang; Zong, Ke-yong

2018-03-01

According to the traits of harmonics in microgrid, a new CANN controller which combines BP and RBF neural network is proposed to control APF to detect and suppress harmonics. This controller has the function of current prediction. By simulation in Matlab / Simulink, this design can shorten the delay time nearly 0.02s (a power supply current cycle) in comparison with the traditional controller based on ip-iq method. The new controller also has higher compensation accuracy and better dynamic tracking traits, it can greatly suppress the harmonics and improve the power quality.

Experiments on Adaptive Techniques for Host-Based Intrusion Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

DRAELOS, TIMOTHY J.; COLLINS, MICHAEL J.; DUGGAN, DAVID P.

2001-09-01

This research explores four experiments of adaptive host-based intrusion detection (ID) techniques in an attempt to develop systems that can detect novel exploits. The technique considered to have the most potential is adaptive critic designs (ACDs) because of their utilization of reinforcement learning, which allows learning exploits that are difficult to pinpoint in sensor data. Preliminary results of ID using an ACD, an Elman recurrent neural network, and a statistical anomaly detection technique demonstrate an ability to learn to distinguish between clean and exploit data. We used the Solaris Basic Security Module (BSM) as a data source and performed considerablemore » preprocessing on the raw data. A detection approach called generalized signature-based ID is recommended as a middle ground between signature-based ID, which has an inability to detect novel exploits, and anomaly detection, which detects too many events including events that are not exploits. The primary results of the ID experiments demonstrate the use of custom data for generalized signature-based intrusion detection and the ability of neural network-based systems to learn in this application environment.« less

Techniques for fire detection

NASA Technical Reports Server (NTRS)

Bukowski, Richard W.

1987-01-01

An overview is given of the basis for an analysis of combustable materials and potential ignition sources in a spacecraft. First, the burning process is discussed in terms of the production of the fire signatures normally associated with detection devices. These include convected and radiated thermal energy, particulates, and gases. Second, the transport processes associated with the movement of these from the fire to the detector, along with the important phenomena which cause the level of these signatures to be reduced, are described. Third, the operating characteristics of the individual types of detectors which influence their response to signals, are presented. Finally, vulnerability analysis using predictive fire modeling techniques is discussed as a means to establish the necessary response of the detection system to provide the level of protection required in the application.

Qualitative and quantitative effects of harmonic echocardiographic imaging on endocardial edge definition and side-lobe artifacts

NASA Technical Reports Server (NTRS)

Rubin, D. N.; Yazbek, N.; Garcia, M. J.; Stewart, W. J.; Thomas, J. D.

2000-01-01

Harmonic imaging is a new ultrasonographic technique that is designed to improve image quality by exploiting the spontaneous generation of higher frequencies as ultrasound propagates through tissue. We studied 51 difficult-to-image patients with blinded side-by-side cineloop evaluation of endocardial border definition by harmonic versus fundamental imaging. In addition, quantitative intensities from cavity versus wall were compared for harmonic versus fundamental imaging. Harmonic imaging improved left ventricular endocardial border delineation over fundamental imaging (superior: harmonic = 71.1%, fundamental = 18.7%; similar: 10.2%; P <.001). Quantitative analysis of 100 wall/cavity combinations demonstrated brighter wall segments and more strikingly darker cavities during harmonic imaging (cavity intensity on a 0 to 255 scale: fundamental = 15.6 +/- 8.6; harmonic = 6.0 +/- 5.3; P <.0001), which led to enhanced contrast between the wall and cavity (1.89 versus 1.19, P <.0001). Harmonic imaging reduces side-lobe artifacts, resulting in a darker cavity and brighter walls, thereby improving image contrast and endocardial delineation.

Signal analysis techniques for incipient failure detection in turbomachinery

NASA Technical Reports Server (NTRS)

Coffin, T.

1985-01-01

Signal analysis techniques for the detection and classification of incipient mechanical failures in turbomachinery were developed, implemented and evaluated. Signal analysis techniques available to describe dynamic measurement characteristics are reviewed. Time domain and spectral methods are described, and statistical classification in terms of moments is discussed. Several of these waveform analysis techniques were implemented on a computer and applied to dynamic signals. A laboratory evaluation of the methods with respect to signal detection capability is described. Plans for further technique evaluation and data base development to characterize turbopump incipient failure modes from Space Shuttle main engine (SSME) hot firing measurements are outlined.

Advanced Gouy phase high harmonics interferometer

NASA Astrophysics Data System (ADS)

Mustary, M. H.; Laban, D. E.; Wood, J. B. O.; Palmer, A. J.; Holdsworth, J.; Litvinyuk, I. V.; Sang, R. T.

2018-05-01

We describe an extreme ultraviolet (XUV) interferometric technique that can resolve ∼100 zeptoseconds (10‑21 s) delay between high harmonic emissions from two successive sources separated spatially along the laser propagation in a single Gaussian beam focus. Several improvements on our earlier work have been implemented in the advanced interferometer. In this paper, we report on the design, characterization and optimization of the advanced Gouy phase interferometer. Temporal coherence for both atomic argon and molecular hydrogen gases has been observed for several harmonic orders. It has been shown that phase shift of XUV pulses mainly originates from the emission time delay due to the Gouy phase in the laser focus and the observed interference is independent of the generating medium. This interferometer can be a useful tool for measuring the relative phase shift between any two gas species and for studying ultrafast dynamics of their electronic and nuclear motion.

In vitro and in vivo tissue harmonic images obtained with parallel transmit beamforming by means of orthogonal frequency division multiplexing.

PubMed

Demi, Libertario; Ramalli, Alessandro; Giannini, Gabriele; Mischi, Massimo

2015-01-01

In classic pulse-echo ultrasound imaging, the data acquisition rate is limited by the speed of sound. To overcome this, parallel beamforming techniques in transmit (PBT) and in receive (PBR) mode have been proposed. In particular, PBT techniques, based on the transmission of focused beams, are more suitable for harmonic imaging because they are capable of generating stronger harmonics. Recently, orthogonal frequency division multiplexing (OFDM) has been investigated as a means to obtain parallel beamformed tissue harmonic images. To date, only numerical studies and experiments in water have been performed, hence neglecting the effect of frequencydependent absorption. Here we present the first in vitro and in vivo tissue harmonic images obtained with PBT by means of OFDM, and we compare the results with classic B-mode tissue harmonic imaging. The resulting contrast-to-noise ratio, here used as a performance metric, is comparable. A reduction by 2 dB is observed for the case in which three parallel lines are reconstructed. In conclusion, the applicability of this technique to ultrasonography as a means to improve the data acquisition rate is confirmed.

Flood Detection/Monitoring Using Adjustable Histogram Equalization Technique

PubMed Central

Riaz, Muhammad Mohsin; Ghafoor, Abdul

2014-01-01

Flood monitoring technique using adjustable histogram equalization is proposed. The technique overcomes the limitations (overenhancement, artifacts, and unnatural look) of existing technique by adjusting the contrast of images. The proposed technique takes pre- and postimages and applies different processing steps for generating flood map without user interaction. The resultant flood maps can be used for flood monitoring and detection. Simulation results show that the proposed technique provides better output quality compared to the state of the art existing technique. PMID:24558332

NONDESTRUCTIVE TESTING (NDT) TECHNIQUES TO DETECT CONTAINED SUBSURFACE HAZARDOUS WASTE

EPA Science Inventory

The project involves the detection of buried containers with NDT (remote-sensing) techniques. Seventeen techniques were considered and four were ultimately decided upon. They were: electromagnetic induction (EMI); metal detection (MD); magnetometer (MAG); and ground penetrating r...

Combination of binaural and harmonic masking release effects in the detection of a single component in complex tones.

PubMed

Klein-Hennig, Martin; Dietz, Mathias; Hohmann, Volker

2018-03-01

Both harmonic and binaural signal properties are relevant for auditory processing. To investigate how these cues combine in the auditory system, detection thresholds for an 800-Hz tone masked by a diotic (i.e., identical between the ears) harmonic complex tone were measured in six normal-hearing subjects. The target tone was presented either diotically or with an interaural phase difference (IPD) of 180° and in either harmonic or "mistuned" relationship to the diotic masker. Three different maskers were used, a resolved and an unresolved complex tone (fundamental frequency: 160 and 40 Hz) with four components below and above the target frequency and a broadband unresolved complex tone with 12 additional components. The target IPD provided release from masking in most masker conditions, whereas mistuning led to a significant release from masking only in the diotic conditions with the resolved and the narrowband unresolved maskers. A significant effect of mistuning was neither found in the diotic condition with the wideband unresolved masker nor in any of the dichotic conditions. An auditory model with a single analysis frequency band and different binaural processing schemes was employed to predict the data of the unresolved masker conditions. Sensitivity to modulation cues was achieved by including an auditory-motivated modulation filter in the processing pathway. The predictions of the diotic data were in line with the experimental results and literature data in the narrowband condition, but not in the broadband condition, suggesting that across-frequency processing is involved in processing modulation information. The experimental and model results in the dichotic conditions show that the binaural processor cannot exploit modulation information in binaurally unmasked conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Microwave Technique for Detecting and Locating Concealed Weapons

DOT National Transportation Integrated Search

1971-12-01

The subject of this report is the evaluation of a microwave technique for detecting and locating weapons concealed under clothing. The principal features of this technique are: persons subjected to search are not exposed to 'objectional' microwave ra...

Digital detection and processing of multiple quadrature harmonics for EPR spectroscopy.

PubMed

Ahmad, R; Som, S; Kesselring, E; Kuppusamy, P; Zweier, J L; Potter, L C

2010-12-01

A quadrature digital receiver and associated signal estimation procedure are reported for L-band electron paramagnetic resonance (EPR) spectroscopy. The approach provides simultaneous acquisition and joint processing of multiple harmonics in both in-phase and out-of-phase channels. The digital receiver, based on a high-speed dual-channel analog-to-digital converter, allows direct digital down-conversion with heterodyne processing using digital capture of the microwave reference signal. Thus, the receiver avoids noise and nonlinearity associated with analog mixers. Also, the architecture allows for low-Q anti-alias filtering and does not require the sampling frequency to be time-locked to the microwave reference. A noise model applicable for arbitrary contributions of oscillator phase noise is presented, and a corresponding maximum-likelihood estimator of unknown parameters is also reported. The signal processing is applicable for Lorentzian lineshape under nonsaturating conditions. The estimation is carried out using a convergent iterative algorithm capable of jointly processing the in-phase and out-of-phase data in the presence of phase noise and unknown microwave phase. Cramér-Rao bound analysis and simulation results demonstrate a significant reduction in linewidth estimation error using quadrature detection, for both low and high values of phase noise. EPR spectroscopic data are also reported for illustration. Copyright © 2010 Elsevier Inc. All rights reserved.

Detection of main tidal frequencies using least squares harmonic estimation method

NASA Astrophysics Data System (ADS)

Mousavian, R.; Hossainali, M. Mashhadi

2012-11-01

In this paper the efficiency of the method of Least Squares Harmonic Estimation (LS-HE) for detecting the main tidal frequencies is investigated. Using this method, the tidal spectrum of the sea level data is evaluated at two tidal stations: Bandar Abbas in south of Iran and Workington on the eastern coast of the UK. The amplitudes of the tidal constituents at these two tidal stations are not the same. Moreover, in contrary to the Workington station, the Bandar Abbas tidal record is not an equispaced time series. Therefore, the analysis of the hourly tidal observations in Bandar Abbas and Workington can provide a reasonable insight into the efficiency of this method for analyzing the frequency content of tidal time series. Furthermore, applying the method of Fourier transform to the Workington tidal record provides an independent source of information for evaluating the tidal spectrum proposed by the LS-HE method. According to the obtained results, the spectrums of these two tidal records contain the components with the maximum amplitudes among the expected ones in this time span and some new frequencies in the list of known constituents. In addition, in terms of frequencies with maximum amplitude; the power spectrums derived from two aforementioned methods are the same. These results demonstrate the ability of LS-HE for identifying the frequencies with maximum amplitude in both tidal records.

An algebraic cluster model based on the harmonic oscillator basis

NASA Technical Reports Server (NTRS)

Levai, Geza; Cseh, J.

1995-01-01

We discuss the semimicroscopic algebraic cluster model introduced recently, in which the internal structure of the nuclear clusters is described by the harmonic oscillator shell model, while their relative motion is accounted for by the Vibron model. The algebraic formulation of the model makes extensive use of techniques associated with harmonic oscillators and their symmetry group, SU(3). The model is applied to some cluster systems and is found to reproduce important characteristics of nuclei in the sd-shell region. An approximate SU(3) dynamical symmetry is also found to hold for the C-12 + C-12 system.

Analysis of higher order harmonics with holographic reflection gratings

NASA Astrophysics Data System (ADS)

Mas-Abellan, P.; Madrigal, R.; Fimia, A.

2017-05-01

Silver halide emulsions have been considered one of the most energetic sensitive materials for holographic applications. Nonlinear recording effects on holographic reflection gratings recorded on silver halide emulsions have been studied by different authors obtaining excellent experimental results. In this communication specifically we focused our investigation on the effects of refractive index modulation, trying to get high levels of overmodulation that will produce high order harmonics. We studied the influence of the overmodulation and its effects on the transmission spectra for a wide exposure range by use of 9 μm thickness films of ultrafine grain emulsion BB640, exposed to single collimated beams using a red He-Ne laser (wavelength 632.8 nm) with Denisyuk configuration obtaining a spatial frequency of 4990 l/mm recorded on the emulsion. The experimental results show that high overmodulation levels of refractive index produce second order harmonics with high diffraction efficiency (higher than 75%) and a narrow grating bandwidth (12.5 nm). Results also show that overmodulation produce diffraction spectra deformation of the second order harmonic, transforming the spectrum from sinusoidal to approximation of square shape due to very high overmodulation. Increasing the levels of overmodulation of refractive index, we have obtained higher order harmonics, obtaining third order harmonic with diffraction efficiency (up to 23%) and narrowing grating bandwidth (5 nm). This study is the first step to develop a new easy technique to obtain narrow spectral filters based on the use of high index modulation reflection gratings.

Evaluation of Advanced Signal Processing Techniques to Improve Detection and Identification of Embedded Defects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clayton, Dwight A.; Santos-Villalobos, Hector J.; Baba, Justin S.

content SAFT, or an improvement in contrast over conventional SAFT reconstructed images. This report documents our efforts in four fronts: 1) Comparative study between traditional SAFT and FBD SAFT for concrete specimen with and without Alkali-Silica Reaction (ASR) damage, 2) improvement of our Model-Based Iterative Reconstruction (MBIR) for thick reinforced concrete [5], 3) development of a universal framework for sharing, reconstruction, and visualization of ultrasound NDE datasets, and 4) application of machine learning techniques for automated detection of ASR inside concrete. Our comparative study between FBD and traditional SAFT reconstruction images shows a clear difference between images of ASR and non-ASR specimens. In particular, the left first harmonic shows an increased contrast and sensitivity to ASR damage. For MBIR, we show the superiority of model-based techniques over delay and sum techniques such as SAFT. Improvements include elimination of artifacts caused by direct arrival signals, and increased contrast and Signal to Noise Ratio. For the universal framework, we document a format for data storage based on the HDF5 file format, and also propose a modular Graphic User Interface (GUI) for easy customization of data conversion, reconstruction, and visualization routines. Finally, two techniques for ASR automated detection are presented. The first technique is based on an analysis of the frequency content using Hilbert Transform Indicator (HTI) and the second technique employees Artificial Neural Network (ANN) techniques for training and classification of ultrasound data as ASR or non-ASR damaged classes. The ANN technique shows great potential with classification accuracy above 95%. These approaches are extensible to the detection of additional reinforced, thick concrete defects and damage.« less

Layer-Dependent Third-Harmonic Generation in Graphene

NASA Astrophysics Data System (ADS)

Yang, Hao; Guan, Honghua; Dadap, Jerry; Osgood, Richard; Richard Osgood Team

Graphene has become a subject of intense interest and study because of its remarkable 2D electronic properties. Multilayer graphene also offers an array of properties that are also of interest for optical physics and devices. Despite its second-order-nonlinear optical response is intrinsically weak, third-order nonlinear optical effects in graphene are symmetry-allowed thus leading to studies of several third-order process in few-layer graphene. In this work, we report third-harmonic generation in multilayer graphene mounted on fused silica and with thicknesses which approach the bulk continuum. THG signals show cubic power dependence with respect to the intensity of fundamental beam. Third-harmonic generation spectroscopy enables a good fit using linear optical detection, which shows strong contrast for different layer number graphene. The maximum THG efficiency appears at layer number around 30. Two models are used for describing this layer dependent phenomenon and shows absorption plays a key role in THG of multilayer graphene. This work also provides a new imaging technology for graphene detection and identification with better contrast and resolution. U.S. Department of Energy under Contract No. DE-FG 02-04-ER-46157.

Using harmonic oscillators to determine the spot size of Hermite-Gaussian laser beams

NASA Technical Reports Server (NTRS)

Steely, Sidney L.

1993-01-01

The similarity of the functional forms of quantum mechanical harmonic oscillators and the modes of Hermite-Gaussian laser beams is illustrated. This functional similarity provides a direct correlation to investigate the spot size of large-order mode Hermite-Gaussian laser beams. The classical limits of a corresponding two-dimensional harmonic oscillator provide a definition of the spot size of Hermite-Gaussian laser beams. The classical limits of the harmonic oscillator provide integration limits for the photon probability densities of the laser beam modes to determine the fraction of photons detected therein. Mathematica is used to integrate the probability densities for large-order beam modes and to illustrate the functional similarities. The probabilities of detecting photons within the classical limits of Hermite-Gaussian laser beams asymptotically approach unity in the limit of large-order modes, in agreement with the Correspondence Principle. The classical limits for large-order modes include all of the nodes for Hermite Gaussian laser beams; Sturm's theorem provides a direct proof.

Monitoring the effect of low-level laser therapy in healing process of skin with second harmonic generation imaging techniques

NASA Astrophysics Data System (ADS)

Zhang, Xiaoman; Yu, Biying; Weng, Cuncheng; Li, Hui

2014-11-01

The 632nm wavelength low intensity He-Ne laser was used to irradiated on 15 mice which had skin wound. The dynamic changes and wound healing processes were observed with nonlinear spectral imaging technology. We observed that:(1)The wound healing process was accelerated by the low-level laser therapy(LLLT);(2)The new tissues produced second harmonic generation (SHG) signals. Collagen content and microstructure differed dramatically at different time pointed along the wound healing. Our observation shows that the low intensity He-Ne laser irradiation can accelerate the healing process of skin wound in mice, and SHG imaging technique can be used to observe wound healing process, which is useful for quantitative characterization of wound status during wound healing process.

Dirty bosons in a three-dimensional harmonic trap

NASA Astrophysics Data System (ADS)

Khellil, Tama; Pelster, Axel

2017-09-01

We study a three-dimensional Bose-Einstein condensate in an isotropic harmonic trapping potential with an additional delta-correlated disorder potential and investigate the emergence of a Bose-glass phase for increasing disorder strength. At zero temperature a first-order quantum phase transition from the superfluid phase to the Bose-glass phase is detected at a critical disorder strength, which agrees with the findings in the literature. Afterwards, we study the interplay between temperature and disorder fluctuations on the respective components of the particle density. In particular, we find for smaller disorder strengths that a superfluid region, a Bose-glass region, and a thermal region coexist. Furthermore, depending on the respective system parameters, three phase transitions are detected, namely, one from the superfluid to the Bose-glass phase, another one from the Bose-glass to the thermal phase, and finally one from the superfluid to the thermal phase. All these results are obtained by extending a quite recent Hartree-Fock mean-field theory for the dirty boson problem, which is based on the replica method, from the homogeneous case to a harmonic confinement.

Soft X-Ray Second Harmonic Generation as an Interfacial Probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lam, R. K.; Raj, S. L.; Pascal, T. A.

Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (~284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from themore » first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.« less

Soft X-Ray Second Harmonic Generation as an Interfacial Probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lam, R. K.; Raj, S. L.; Pascal, T. A.

Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (~284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from themore » first atomic layer at the open surface. Here, this technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.« less

Soft X-Ray Second Harmonic Generation as an Interfacial Probe

DOE PAGES

Lam, R. K.; Raj, S. L.; Pascal, T. A.; ...

2018-01-08

Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (~284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from themore » first atomic layer at the open surface. Here, this technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.« less

Soft X-Ray Second Harmonic Generation as an Interfacial Probe

NASA Astrophysics Data System (ADS)

Lam, R. K.; Raj, S. L.; Pascal, T. A.; Pemmaraju, C. D.; Foglia, L.; Simoncig, A.; Fabris, N.; Miotti, P.; Hull, C. J.; Rizzuto, A. M.; Smith, J. W.; Mincigrucci, R.; Masciovecchio, C.; Gessini, A.; Allaria, E.; De Ninno, G.; Diviacco, B.; Roussel, E.; Spampinati, S.; Penco, G.; Di Mitri, S.; Trovò, M.; Danailov, M.; Christensen, S. T.; Sokaras, D.; Weng, T.-C.; Coreno, M.; Poletto, L.; Drisdell, W. S.; Prendergast, D.; Giannessi, L.; Principi, E.; Nordlund, D.; Saykally, R. J.; Schwartz, C. P.

2018-01-01

Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (˜284 eV ) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.

Harmonic Motion Imaging for Abdominal Tumor Detection and High-intensity Focused Ultrasound Ablation Monitoring: A Feasibility Study in a Transgenic Mouse Model of Pancreatic Cancer

PubMed Central

Chen, Hong; Hou, Gary Y.; Han, Yang; Payen, Thomas; Palermo, Carmine F.; Olive, Kenneth P.; Konofagou, Elisa E.

2015-01-01

Harmonic motion imaging (HMI) is a radiation force-based elasticity imaging technique that tracks oscillatory tissue displacements induced by sinusoidal ultrasonic radiation force to assess relative tissue stiffness. The objective of this study was to evaluate the feasibility of HMI in pancreatic tumor detection and high-intensity focused ultrasound (HIFU) treatment monitoring. The HMI system consisted of a focused ultrasound transducer, which generated sinusoidal radiation force to induce oscillatory tissue motion at 50 Hz, and a diagnostic ultrasound transducer, which detected the axial tissue displacements based on acquired radiofrequency signals using a 1D cross-correlation algorithm. For pancreatic tumor detection, HMI images were generated for pancreatic tumors in transgenic mice and normal pancreases in wild-type mice. The obtained HMI images showed a high contrast between normal and malignant pancreases with an average peak-to-peak HMI displacement ratio of 3.2. Histological analysis showed that no tissue damage was associated with HMI when it was used for the sole purpose of elasticity imaging. For pancreatic tumor ablation monitoring, the focused ultrasound transducer was operated with a higher acoustic power and longer pulse length than that used in tumor detection to simultaneously induce HIFU thermal ablation and oscillatory tissue displacements, allowing HMI monitoring without interrupting tumor ablation. HMI monitoring of HIFU ablation found significant decreases in the peak-to-peak HMI displacements before and after HIFU ablation with a reduction rate ranging from 15.8% to 57.0%. The formation of thermal lesions after HIFU exposure was confirmed by histological analysis. This study demonstrated the feasibility of HMI in abdominal tumor detection and HIFU ablation monitoring. PMID:26415128

Effect of structural modification on second harmonic generation in collagen

NASA Astrophysics Data System (ADS)

Stoller, Patrick C.; Reiser, Karen M.; Celliers, Peter M.; Rubenchik, Alexander M.

2003-07-01

The effects of structural perturbation on second harmonic generation in collagen were investigated. Type I collagen fascicles obtained from rat tails were structurally modified by increasing nonenzymatic cross-linking, by thermal denaturation, by collagenase digestion, or by dehydration. Changes in polarization dependence were observed in the dehydrated samples. Surprisingly, no changes in polarization dependence were observed in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable second harmonic signal. Prior to loss of signal, no change in polarization dependence was observed in partially heated or digested collagen.

Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology

PubMed Central

Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrik; Cohen, Oren; Plaja, Luis; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret

2016-01-01

Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date. PMID:26989782

Comparison of survey techniques on detection of northern flying squirrels

USGS Publications Warehouse

Diggins, Corinne A.; Gilley, L. Michelle; Kelly, Christine A.; Ford, W. Mark

2016-01-01

The ability to detect a species is central to the success of monitoring for conservation and management purposes, especially if the species is rare or endangered. Traditional methods, such as live capture, can be labor-intensive, invasive, and produce low detection rates. Technological advances and new approaches provide opportunities to more effectively survey for species both in terms of accuracy and efficiency than previous methods. We conducted a pilot comparison study of a traditional technique (live-trapping) and 2 novel noninvasive techniques (camera-trapping and ultrasonic acoustic surveys) on detection rates of the federally endangered Carolina northern flying squirrel (Glaucomys sabrinus coloratus) in occupied habitat within the Roan Mountain Highlands of North Carolina, USA. In 2015, we established 3 5 × 5 live-trapping grids (6.5 ha) with 4 camera traps and 4 acoustic detectors systematically embedded in each grid. All 3 techniques were used simultaneously during 2 4-day survey periods. We compared techniques by assessing probability of detection (POD), latency to detection (LTD; i.e., no. of survey nights until initial detection), and survey effort. Acoustics had the greatest POD (0.37 ± 0.06 SE), followed by camera traps (0.30 ± 0.06) and live traps (0.01 ± 0.005). Acoustics had a lower LTD than camera traps (P = 0.017), where average LTD was 1.5 nights for acoustics and 3.25 nights for camera traps. Total field effort was greatest with live traps (111.9 hr) followed by acoustics (8.4 hr) and camera traps (9.6 hr), although processing and examination for data of noninvasive techniques made overall effort similar among the 3 methods. This pilot study demonstrated that both noninvasive methods were better rapid-assessment detection techniques for flying squirrels than live traps. However, determining seasonal effects between survey techniques and further development of protocols for both noninvasive techniques is

Quantitative evaluation of skeletal muscle defects in second harmonic generation images.

PubMed

Liu, Wenhua; Raben, Nina; Ralston, Evelyn

2013-02-01

Skeletal muscle pathologies cause irregularities in the normally periodic organization of the myofibrils. Objective grading of muscle morphology is necessary to assess muscle health, compare biopsies, and evaluate treatments and the evolution of disease. To facilitate such quantitation, we have developed a fast, sensitive, automatic imaging analysis software. It detects major and minor morphological changes by combining texture features and Fourier transform (FT) techniques. We apply this tool to second harmonic generation (SHG) images of muscle fibers which visualize the repeating myosin bands. Texture features are then calculated by using a Haralick gray-level cooccurrence matrix in MATLAB. Two scores are retrieved from the texture correlation plot by using FT and curve-fitting methods. The sensitivity of the technique was tested on SHG images of human adult and infant muscle biopsies and of mouse muscle samples. The scores are strongly correlated to muscle fiber condition. We named the software MARS (muscle assessment and rating scores). It is executed automatically and is highly sensitive even to subtle defects. We propose MARS as a powerful and unbiased tool to assess muscle health.

Quantitative evaluation of skeletal muscle defects in second harmonic generation images

NASA Astrophysics Data System (ADS)

Liu, Wenhua; Raben, Nina; Ralston, Evelyn

2013-02-01

Skeletal muscle pathologies cause irregularities in the normally periodic organization of the myofibrils. Objective grading of muscle morphology is necessary to assess muscle health, compare biopsies, and evaluate treatments and the evolution of disease. To facilitate such quantitation, we have developed a fast, sensitive, automatic imaging analysis software. It detects major and minor morphological changes by combining texture features and Fourier transform (FT) techniques. We apply this tool to second harmonic generation (SHG) images of muscle fibers which visualize the repeating myosin bands. Texture features are then calculated by using a Haralick gray-level cooccurrence matrix in MATLAB. Two scores are retrieved from the texture correlation plot by using FT and curve-fitting methods. The sensitivity of the technique was tested on SHG images of human adult and infant muscle biopsies and of mouse muscle samples. The scores are strongly correlated to muscle fiber condition. We named the software MARS (muscle assessment and rating scores). It is executed automatically and is highly sensitive even to subtle defects. We propose MARS as a powerful and unbiased tool to assess muscle health.

[Progress of study on the detection technique of microRNA].

PubMed

Zhao, Hai-Feng; Yang, Ren-Chi

2009-12-01

MicroRNAs (miRNAs) are small noncoding RNA molecules that negatively regulate gene expression via degradation or translational repression of their targeted mRNAs. MiRNAs are involved in critical biologic processes, including development, cell differentiation, proliferation and the pathogenesis of disease. This review focuses on recent researches on the detection techniques of miRNA including micorarray technique, Northern blot, real-time quantitative PCR, detection technique of miRNA function and so on.

Detection of Glaucoma Using Image Processing Techniques: A Critique.

PubMed

Kumar, B Naveen; Chauhan, R P; Dahiya, Nidhi

2018-01-01

The primary objective of this article is to present a summary of different types of image processing methods employed for the detection of glaucoma, a serious eye disease. Glaucoma affects the optic nerve in which retinal ganglion cells become dead, and this leads to loss of vision. The principal cause is the increase in intraocular pressure, which occurs in open-angle and angle-closure glaucoma, the two major types affecting the optic nerve. In the early stages of glaucoma, no perceptible symptoms appear. As the disease progresses, vision starts to become hazy, leading to blindness. Therefore, early detection of glaucoma is needed for prevention. Manual analysis of ophthalmic images is fairly time-consuming and accuracy depends on the expertise of the professionals. Automatic analysis of retinal images is an important tool. Automation aids in the detection, diagnosis, and prevention of risks associated with the disease. Fundus images obtained from a fundus camera have been used for the analysis. Requisite pre-processing techniques have been applied to the image and, depending upon the technique, various classifiers have been used to detect glaucoma. The techniques mentioned in the present review have certain advantages and disadvantages. Based on this study, one can determine which technique provides an optimum result.

Research on propane leak detection system and device based on mid infrared laser

NASA Astrophysics Data System (ADS)

Jiang, Meng; Wang, Xuefeng; Wang, Junlong; Wang, Yizhao; Li, Pan; Feng, Qiaoling

2017-10-01

Propane is a key component of liquefied petroleum gas (LPG) and crude oil volatile. This issue summarizes the recent progress of propane detection technology. Meanwhile, base on the development trend, our latest progress is also provided. We demonstrated a mid infrared propane sensor system, which is based on wavelength modulation spectroscopy (WMS) technique with a CW interband cascade laser (ICL) emitting at 3370.4nm. The ICL laser scanned over a sharp feature in the broader spectrum of propane, and harmonic signals are obtained by lock-in amplifier for gas concentration deduction. The surrounding gas is extracted into the fine optical absorption cell through the pump to realize online detection. The absorption cell is designed in mid infrared windows range. An example experimental setup is shown. The second harmonic signals 2f and first harmonic signals1f are obtained. We present the sensor performance test data including dynamic precision and temperature stability. The propane detection sensor system and device is portable can carried on the mobile inspection vehicle platforms or intelligent robot inspection platform to realize the leakage monitoring of whole oil gas tank area.

Workshop on Harmonic Oscillators

NASA Technical Reports Server (NTRS)

Han, D. (Editor); Kim, Y. S. (Editor); Zachary, W. W. (Editor)

1993-01-01

Proceedings of a workshop on Harmonic Oscillators held at the College Park Campus of the University of Maryland on March 25 - 28, 1992 are presented. The harmonic oscillator formalism is playing an important role in many branches of physics. This is the simplest mathematical device which can connect the basic principle of physics with what is observed in the real world. The harmonic oscillator is the bridge between pure and applied physics.

Detecting vocal fatigue in student singers using acoustic measures of mean fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio

NASA Astrophysics Data System (ADS)

Sisakun, Siphan

2000-12-01

The purpose of this study is to explore the ability of four acoustic parameters, mean fundamental frequency, jitter, shimmer, and harmonics-to-noise ratio, to detect vocal fatigue in student singers. The participants are 15 voice students, who perform two distinct tasks, data collection task and vocal fatiguing task. The data collection task includes the sustained vowel /a/, reading a standard passage, and self-rate on a vocal fatigue form. The vocal fatiguing task is the vocal practice of musical scores for a total of 45 minutes. The four acoustic parameters are extracted using the software EZVoicePlus. The data analyses are performed to answer eight research questions. The first four questions relate to correlations of the self-rating scale and each of the four parameters. The next four research questions relate to differences in the parameters over time using one-factor repeated measures analysis of variance (ANOVA). The result yields a proposed acoustic profile of vocal fatigue in student singers. This profile is characterized by increased fundamental frequency; slightly decreased jitter; slightly decreased shimmer; and slightly increased harmonics-to-noise ratio. The proposed profile requires further investigation.

Seismic Techniques for Subsurface Voids Detection

NASA Astrophysics Data System (ADS)

Gritto, Roland; Korneev, Valeri; Elobaid Elnaiem, Ali; Mohamed, Fathelrahman; Sadooni, Fadhil

2016-04-01

A major hazards in Qatar is the presence of karst, which is ubiquitous throughout the country including depressions, sinkholes, and caves. Causes for the development of karst include faulting and fracturing where fluids find pathways through limestone and dissolve the host rock to form caverns. Of particular concern in rapidly growing metropolitan areas that expand in heretofore unexplored regions are the collapse of such caverns. Because Qatar has seen a recent boom in construction, including the planning and development of complete new sub-sections of metropolitan areas, the development areas need to be investigated for the presence of karst to determine their suitability for the planned project. In this paper, we present the results of a study to demonstrate a variety of seismic techniques to detect the presence of a karst analog in form of a vertical water-collection shaft located on the campus of Qatar University, Doha, Qatar. Seismic waves are well suited for karst detection and characterization. Voids represent high-contrast seismic objects that exhibit strong responses due to incident seismic waves. However, the complex geometry of karst, including shape and size, makes their imaging nontrivial. While karst detection can be reduced to the simple problem of detecting an anomaly, karst characterization can be complicated by the 3D nature of the problem of unknown scale, where irregular surfaces can generate diffracted waves of different kind. In our presentation we employ a variety of seismic techniques to demonstrate the detection and characterization of a vertical water collection shaft analyzing the phase, amplitude and spectral information of seismic waves that have been scattered by the object. We used the reduction in seismic wave amplitudes and the delay in phase arrival times in the geometrical shadow of the vertical shaft to independently detect and locate the object in space. Additionally, we use narrow band-pass filtered data combining two

A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation.

PubMed

Hu, Yi

2010-05-01

Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.

Tuvan throat singing and harmonics

NASA Astrophysics Data System (ADS)

Ruiz, Michael J.; Wilken, David

2018-05-01

Tuvan throat singing, also called overtone singing, provides for an exotic demonstration of the physics of harmonics as well as introducing an Asian musical aesthetic. A low fundamental is sung and the singer skillfully alters the resonances of the vocal system to enhance an overtone (harmonic above the fundamental). The result is that the listener hears two pitches simultaneously. Harmonics such as H8, H9, H10, and H12 form part of a pentatonic scale and are commonly selected for melody tones by Tuvan singers. A real-time spectrogram is provided in a video (Ruiz M J 2018 Video: Tuvan Throat Singing and Harmonics http://mjtruiz.com/ped/tuva/) so that Tuvan harmonics can be visualized as they are heard.

Tailored semiconductors for high-harmonic optoelectronics

NASA Astrophysics Data System (ADS)

Sivis, Murat; Taucer, Marco; Vampa, Giulio; Johnston, Kyle; Staudte, André; Naumov, Andrei Yu.; Villeneuve, D. M.; Ropers, Claus; Corkum, P. B.

2017-07-01

The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology. This enables the control of high-harmonic technology within precisely engineered solid targets. We demonstrate customized high-harmonic wave fields with wavelengths down to 225 nanometers (ninth-harmonic order of 2-micrometer laser pulses) and present an integrated Fresnel zone plate target in silicon, which leads to diffraction-limited self-focusing of the generated harmonics down to 1-micrometer spot sizes.

Effects of attention on the neural processing of harmonic syntax in Western music.

PubMed

Loui, Psyche; Grent-'t-Jong, Tineke; Torpey, Dana; Woldorff, Marty

2005-12-01

The effects of selective attention on the neural response to the violation of musical syntax were investigated in the present study. Musical chord progressions were played to nonmusicians while Event-Related Potentials (ERPs) were recorded. The five-chord progressions included 61% harmonically expected cadences (I-I(6)-IV-V-I), 26% harmonically unexpected cadences (I-I(6)-IV-V-N(6)), and 13% with one of the five chords having an intensity fadeout across its duration. During the attended condition, subjects responded by pressing a button upon detecting a fadeout in volume; during the unattended condition, subjects were given reading comprehension materials and instructed to ignore all auditory stimuli. In response to the harmonic deviant, an Early Anterior Negativity (EAN) was observed at 150-300 ms in both attention conditions, but it was much larger in amplitude in the attended condition. A second scalp-negative deflection was also identified at 380-600 ms following the harmonic deviants; this Late Negativity onset earlier during the attended condition. These results suggest strong effects of attention on the neural processing of harmonic syntax.

Projective techniques and the detection of child sexual abuse.

PubMed

Garb, H N; Wood, J M; Nezworski, M T

2000-05-01

Projective techniques (e.g., the Rorschach, Human Figure Drawings) are sometimes used to detect child sexual abuse. West recently conducted a meta-analysis on this topic, but she systematically excluded nonsignificant results. In this article, a reanalysis of her data is presented. The authors conclude that projective techniques should not be used to detect child sexual abuse. Many of the studies purportedly demonstrating validity are flawed, and none of the projective test scores have been well replicated.

Adaptive torque estimation of robot joint with harmonic drive transmission

NASA Astrophysics Data System (ADS)

Shi, Zhiguo; Li, Yuankai; Liu, Guangjun

2017-11-01

Robot joint torque estimation using input and output position measurements is a promising technique, but the result may be affected by the load variation of the joint. In this paper, a torque estimation method with adaptive robustness and optimality adjustment according to load variation is proposed for robot joint with harmonic drive transmission. Based on a harmonic drive model and a redundant adaptive robust Kalman filter (RARKF), the proposed approach can adapt torque estimation filtering optimality and robustness to the load variation by self-tuning the filtering gain and self-switching the filtering mode between optimal and robust. The redundant factor of RARKF is designed as a function of the motor current for tolerating the modeling error and load-dependent filtering mode switching. The proposed joint torque estimation method has been experimentally studied in comparison with a commercial torque sensor and two representative filtering methods. The results have demonstrated the effectiveness of the proposed torque estimation technique.

Anomaly Detection in Power Quality at Data Centers

NASA Technical Reports Server (NTRS)

Grichine, Art; Solano, Wanda M.

2015-01-01

The goal during my internship at the National Center for Critical Information Processing and Storage (NCCIPS) is to implement an anomaly detection method through the StruxureWare SCADA Power Monitoring system. The benefit of the anomaly detection mechanism is to provide the capability to detect and anticipate equipment degradation by monitoring power quality prior to equipment failure. First, a study is conducted that examines the existing techniques of power quality management. Based on these findings, and the capabilities of the existing SCADA resources, recommendations are presented for implementing effective anomaly detection. Since voltage, current, and total harmonic distortion demonstrate Gaussian distributions, effective set-points are computed using this model, while maintaining a low false positive count.

Biophotonic endoscopy: a review of clinical research techniques for optical imaging and sensing of early gastrointestinal cancer

PubMed Central

Coda, Sergio; Siersema, Peter D.; Stamp, Gordon W. H.; Thillainayagam, Andrew V.

2015-01-01

Detection, characterization, and staging constitute the fundamental elements in the endoscopic diagnosis of gastrointestinal diseases, but histology still remains the diagnostic gold standard. New developments in endoscopic techniques may challenge histopathology in the near future. An ideal endoscopic technique should combine a wide-field, “red flag” screening technique with an optical contrast or microscopy method for characterization and staging, all simultaneously available during the procedure. In theory, biophotonic advances have the potential to unite these elements to allow in vivo “optical biopsy.” These techniques may ultimately offer the potential to increase the rates of detection of high risk lesions and the ability to target biopsies and resections, and so reduce the need for biopsy, costs, and uncertainty for patients. However, their utility and sensitivity in clinical practice must be evaluated against those of conventional histopathology. This review describes some of the most recent applications of biophotonics in endoscopic optical imaging and metrology, along with their fundamental principles and the clinical experience that has been acquired in their deployment as tools for the endoscopist. Particular emphasis has been placed on translational label-free optical techniques, such as fluorescence spectroscopy, fluorescence lifetime imaging microscopy (FLIM), two-photon and multi-photon microscopy, second harmonic generation (SHG) and third harmonic generation (THG) imaging, optical coherence tomography (OCT), diffuse reflectance, Raman spectroscopy, and molecular imaging. PMID:26528489

Bioinspired second harmonic generation

NASA Astrophysics Data System (ADS)

Sonay, Ali Y.; Pantazis, Periklis

2017-07-01

Second harmonic generation (SHG) is a microscopic technique applicable to a broad spectrum of biological and medical imaging due to its excellent photostability, high signal-to-noise ratio (SNR) and narrow emission profile. Current SHG microscopy techniques rely on two main contrast modalities. These are endogenous SHG generated by tissue structures, which is clinically relevant but cannot be targeted to another location, or SHG nanoprobes, inorganic nanocrystals that can be directed to proteins and cells of interest, but cannot be applied for clinical imaging due to their chemical composition. Here we analyzed SHG signal generated by large-scale peptide assemblies. Our results show the sequence of peptides play an important role on both the morphology and SHG signal of the peptide assemblies. Changing peptide sequence allows confinement of large number of peptides to smaller voxels, generating intense SHG signal. With miniaturization of these peptides and their proper functionalization strategies, such bioinspired nanoparticles would emerge as valuable tools for clinical imaging.

Sample detection and analysis techniques for electrophoretic separation

NASA Technical Reports Server (NTRS)

Falb, R. D.; Hughes, K. E.; Powell, T. R.

1975-01-01

Methods for detecting and analyzing biological agents suitable for space flight operations were studied primarily by literature searches which were conducted of cell separation techniques. Detection methods discussed include: photometrometric, electric, radiometric, micrometry, ultrasonic, microscopic, and photographic. A bibliography, and a directory of vendors are included along with an index of commercial hardware.

Master training course for detection techniques

NASA Astrophysics Data System (ADS)

Kern, P.

2013-11-01

The LabEx FOCUS proposes a training course to the detection techniques. It will be proposed yearly to the students of master or of engineering school . This theoretical and practical training will be given during a full week at the Observatoire de Haute Provence. The teachers are members from the laboratories of the FOCUS consortium.

Technique for ship/wake detection

DOEpatents

Roskovensky, John K [Albuquerque, NM

2012-05-01

An automated ship detection technique includes accessing data associated with an image of a portion of Earth. The data includes reflectance values. A first portion of pixels within the image are masked with a cloud and land mask based on spectral flatness of the reflectance values associated with the pixels. A given pixel selected from the first portion of pixels is unmasked when a threshold number of localized pixels surrounding the given pixel are not masked by the cloud and land mask. A spatial variability image is generated based on spatial derivatives of the reflectance values of the pixels which remain unmasked by the cloud and land mask. The spatial variability image is thresholded to identify one or more regions within the image as possible ship detection regions.

A Review of Financial Accounting Fraud Detection based on Data Mining Techniques

NASA Astrophysics Data System (ADS)

Sharma, Anuj; Kumar Panigrahi, Prabin

2012-02-01

With an upsurge in financial accounting fraud in the current economic scenario experienced, financial accounting fraud detection (FAFD) has become an emerging topic of great importance for academic, research and industries. The failure of internal auditing system of the organization in identifying the accounting frauds has lead to use of specialized procedures to detect financial accounting fraud, collective known as forensic accounting. Data mining techniques are providing great aid in financial accounting fraud detection, since dealing with the large data volumes and complexities of financial data are big challenges for forensic accounting. This paper presents a comprehensive review of the literature on the application of data mining techniques for the detection of financial accounting fraud and proposes a framework for data mining techniques based accounting fraud detection. The systematic and comprehensive literature review of the data mining techniques applicable to financial accounting fraud detection may provide a foundation to future research in this field. The findings of this review show that data mining techniques like logistic models, neural networks, Bayesian belief network, and decision trees have been applied most extensively to provide primary solutions to the problems inherent in the detection and classification of fraudulent data.

A method for measuring the nonlinear response in dielectric spectroscopy through third harmonics detection.

PubMed

Thibierge, C; L'Hôte, D; Ladieu, F; Tourbot, R

2008-10-01

We present a high sensitivity method allowing the measurement of the nonlinear dielectric susceptibility of an insulating material at finite frequency. It has been developed for the study of dynamic heterogeneities in supercooled liquids using dielectric spectroscopy at frequencies 0.05 Hz < or = f < or = 3x10(4) Hz. It relies on the measurement of the third harmonics component of the current flowing out of a capacitor. We first show that standard laboratory electronics (amplifiers and voltage sources) nonlinearities lead to limits on the third harmonics measurements that preclude reaching the level needed by our physical goal, a ratio of the third harmonics to the fundamental signal about 10(-7). We show that reaching such a sensitivity needs a method able to get rid of the nonlinear contributions both of the measuring device (lock-in amplifier) and of the excitation voltage source. A bridge using two sources fulfills only the first of these two requirements, but allows to measure the nonlinearities of the sources. Our final method is based on a bridge with two plane capacitors characterized by different dielectric layer thicknesses. It gets rid of the source and amplifier nonlinearities because in spite of a strong frequency dependence of the capacitor impedance, it is equilibrated at any frequency. We present the first measurements of the physical nonlinear response using our method. Two extensions of the method are suggested.

Measurement techniques investigated for detection of hydrogen chloride gas in ambient air

NASA Technical Reports Server (NTRS)

Gregory, G. L.

1976-01-01

Nine basic techniques are discussed, ranging from concentration (parts per million) to dosage only (parts per million-seconds) measurement techniques. Data for each technique include lower detection limit, response time, instrument status, and in some cases, specificity. Several techniques discussed can detect ambient hydrogen chloride concentrations below 1 part per million with a response time of seconds.

Elasticity mapping of murine abdominal organs in vivo using harmonic motion imaging (HMI)

NASA Astrophysics Data System (ADS)

Payen, Thomas; Palermo, Carmine F.; Sastra, Stephen A.; Chen, Hong; Han, Yang; Olive, Kenneth P.; Konofagou, Elisa E.

2016-08-01

Recently, ultrasonic imaging of soft tissue mechanics has been increasingly studied to image otherwise undetectable pathologies. However, many underlying mechanisms of tissue stiffening remain unknown, requiring small animal studies and adapted elasticity mapping techniques. Harmonic motion imaging (HMI) assesses tissue viscoelasticity by inducing localized oscillation from a periodic acoustic radiation force. The objective of this study was to evaluate the feasibility of HMI for in vivo elasticity mapping of abdominal organs in small animals. Pathological cases, i.e. chronic pancreatitis and pancreatic cancer, were also studied in vivo to assess the capability of HMI for detection of the change in mechanical properties. A 4.5 MHz focused ultrasound transducer (FUS) generated an amplitude-modulated beam resulting in 50 Hz harmonic tissue oscillations at its focus. Axial tissue displacement was estimated using 1D-cross-correlation of RF signals acquired with a 7.8 MHz diagnostic transducer confocally aligned with the FUS. In vitro results in canine liver and kidney showed the correlation between HMI displacement and Young’s moduli measured by rheometry compression testing. HMI was capable of providing reproducible elasticity maps of the mouse abdominal region in vivo allowing the identification of, from stiffest to softest, the murine kidney, pancreas, liver, and spleen. Finally, pancreata affected by pancreatitis and pancreatic cancer showed HMI displacements 1.7 and 2.2 times lower than in the control case, respectively, indicating higher stiffness. The HMI displacement amplitude was correlated with the extent of fibrosis as well as detecting the very onset of stiffening even before fibrosis could be detected on H&E. This work shows that HMI can produce reliable elasticity maps of mouse abdominal region in vivo, thus providing a potentially critical tool to assess pathologies affecting organ elasticity.

Elasticity mapping of murine abdominal organs in vivo using Harmonic Motion Imaging (HMI)

PubMed Central

Payen, Thomas; Palermo, Carmine F.; Sastra, Steve; Chen, Hong; Han, Yang; Olive, Kenneth P.; Konofagou, Elisa E.

2016-01-01

Recently, ultrasonic imaging of soft tissue mechanics has been increasingly studied to image otherwise undetectable pathologies. However, many underlying mechanisms of tissue stiffening remain unknown, requiring small animal studies and adapted elasticity mapping techniques. Harmonic motion imaging (HMI) assesses tissue viscoelasticity by inducing localized oscillation from a periodic acoustic radiation force. The objective of this study was to evaluate the feasibility of HMI for in vivo elasticity mapping of abdominal organs in small animals. Pathological cases, i.e. chronic pancreatitis and pancreatic cancer, were also studied in vivo to assess the capability of HMI for detection of the change in mechanical properties. A 4.5-MHz focused ultrasound transducer (FUS) generated an amplitude-modulated beam resulting in 50-Hz harmonic tissue oscillations at its focus. Axial tissue displacement was estimated using 1D-cross-correlation of RF signals acquired with a 7.8-MHz diagnostic transducer confocally aligned with the FUS. In vitro results in canine liver and kidney showed the correlation between HMI displacement and Young’s moduli measured by rheometry compression tests. HMI was able to provide reproducible elasticity maps of the mouse abdominal region in vivo allowing the identification of, from stiffest to softest, the murine kidney, pancreas, liver, and spleen. Finally, pancreata affected by pancreatitis and pancreatic cancer showed HMI displacements 1.7 and 2.2 times lower than in the control case, respectively, indicating higher stiffness. HMI displacement was correlated with the extent of fibrosis as well as detecting the very onset of stiffening even before fibrosis could be detected on H&E. This work shows that HMI can produce reliable elasticity maps of mouse abdominal region in vivo providing a crucial tool to understand pathologies affecting organ elasticity. PMID:27401609

Elasticity mapping of murine abdominal organs in vivo using harmonic motion imaging (HMI).

PubMed

Payen, Thomas; Palermo, Carmine F; Sastra, Stephen A; Chen, Hong; Han, Yang; Olive, Kenneth P; Konofagou, Elisa E

2016-08-07

Recently, ultrasonic imaging of soft tissue mechanics has been increasingly studied to image otherwise undetectable pathologies. However, many underlying mechanisms of tissue stiffening remain unknown, requiring small animal studies and adapted elasticity mapping techniques. Harmonic motion imaging (HMI) assesses tissue viscoelasticity by inducing localized oscillation from a periodic acoustic radiation force. The objective of this study was to evaluate the feasibility of HMI for in vivo elasticity mapping of abdominal organs in small animals. Pathological cases, i.e. chronic pancreatitis and pancreatic cancer, were also studied in vivo to assess the capability of HMI for detection of the change in mechanical properties. A 4.5 MHz focused ultrasound transducer (FUS) generated an amplitude-modulated beam resulting in 50 Hz harmonic tissue oscillations at its focus. Axial tissue displacement was estimated using 1D-cross-correlation of RF signals acquired with a 7.8 MHz diagnostic transducer confocally aligned with the FUS. In vitro results in canine liver and kidney showed the correlation between HMI displacement and Young's moduli measured by rheometry compression testing. HMI was capable of providing reproducible elasticity maps of the mouse abdominal region in vivo allowing the identification of, from stiffest to softest, the murine kidney, pancreas, liver, and spleen. Finally, pancreata affected by pancreatitis and pancreatic cancer showed HMI displacements 1.7 and 2.2 times lower than in the control case, respectively, indicating higher stiffness. The HMI displacement amplitude was correlated with the extent of fibrosis as well as detecting the very onset of stiffening even before fibrosis could be detected on H&E. This work shows that HMI can produce reliable elasticity maps of mouse abdominal region in vivo, thus providing a potentially critical tool to assess pathologies affecting organ elasticity.

A Comparative Study of Unsupervised Anomaly Detection Techniques Using Honeypot Data

NASA Astrophysics Data System (ADS)

Song, Jungsuk; Takakura, Hiroki; Okabe, Yasuo; Inoue, Daisuke; Eto, Masashi; Nakao, Koji

Intrusion Detection Systems (IDS) have been received considerable attention among the network security researchers as one of the most promising countermeasures to defend our crucial computer systems or networks against attackers on the Internet. Over the past few years, many machine learning techniques have been applied to IDSs so as to improve their performance and to construct them with low cost and effort. Especially, unsupervised anomaly detection techniques have a significant advantage in their capability to identify unforeseen attacks, i.e., 0-day attacks, and to build intrusion detection models without any labeled (i.e., pre-classified) training data in an automated manner. In this paper, we conduct a set of experiments to evaluate and analyze performance of the major unsupervised anomaly detection techniques using real traffic data which are obtained at our honeypots deployed inside and outside of the campus network of Kyoto University, and using various evaluation criteria, i.e., performance evaluation by similarity measurements and the size of training data, overall performance, detection ability for unknown attacks, and time complexity. Our experimental results give some practical and useful guidelines to IDS researchers and operators, so that they can acquire insight to apply these techniques to the area of intrusion detection, and devise more effective intrusion detection models.

Benchtop Antigen Detection Technique using Nanofiltration and Fluorescent Dyes

NASA Technical Reports Server (NTRS)

Scardelletti, Maximilian C.; Varaljay, Vanessa

2009-01-01

The designed benchtop technique is primed to detect bacteria and viruses from antigenic surface marker proteins in solutions, initially water. This inclusive bio-immunoassay uniquely combines nanofiltration and near infrared (NIR) dyes conjugated to antibodies to isolate and distinguish microbial antigens, using laser excitation and spectrometric analysis. The project goals include detecting microorganisms aboard the International Space Station, space shuttle, Crew Exploration Vehicle (CEV), and human habitats on future Moon and Mars missions, ensuring astronaut safety. The technique is intended to improve and advance water contamination testing both commercially and environmentally as well. Lastly, this streamlined technique poses to greatly simplify and expedite testing of pathogens in complex matrices, such as blood, in hospital and laboratory clinics.

The 'sniffer-patch' technique for detection of neurotransmitter release.

PubMed

Allen, T G

1997-05-01

A wide variety of techniques have been employed for the detection and measurement of neurotransmitter release from biological preparations. Whilst many of these methods offer impressive levels of sensitivity, few are able to combine sensitivity with the necessary temporal and spatial resolution required to study quantal release from single cells. One detection method that is seeing a revival of interest and has the potential to fill this niche is the so-called 'sniffer-patch' technique. In this article, specific examples of the practical aspects of using this technique are discussed along with the procedures involved in calibrating these biosensors to extend their applications to provide quantitative, in addition to simple qualitative, measurements of quantal transmitter release.

Tailored semiconductors for high-harmonic optoelectronics.

PubMed

Sivis, Murat; Taucer, Marco; Vampa, Giulio; Johnston, Kyle; Staudte, André; Naumov, Andrei Yu; Villeneuve, D M; Ropers, Claus; Corkum, P B

2017-07-21

The advent of high-harmonic generation in gases 30 years ago set the foundation for attosecond science and facilitated ultrafast spectroscopy in atoms, molecules, and solids. We explore high-harmonic generation in the solid state by means of nanostructured and ion-implanted semiconductors. We use wavelength-selective microscopic imaging to map enhanced harmonic emission and show that the generation medium and the driving field can be locally tailored in solids by modifying the chemical composition and morphology. This enables the control of high-harmonic technology within precisely engineered solid targets. We demonstrate customized high-harmonic wave fields with wavelengths down to 225 nanometers (ninth-harmonic order of 2-micrometer laser pulses) and present an integrated Fresnel zone plate target in silicon, which leads to diffraction-limited self-focusing of the generated harmonics down to 1-micrometer spot sizes. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Investigation of Second- and Third-Harmonic Generation in Few-Layer Gallium Selenide by Multiphoton Microscopy

PubMed Central

Karvonen, Lasse; Säynätjoki, Antti; Mehravar, Soroush; Rodriguez, Raul D.; Hartmann, Susanne; Zahn, Dietrich R. T.; Honkanen, Seppo; Norwood, Robert A.; Peyghambarian, N.; Kieu, Khanh; Lipsanen, Harri; Riikonen, Juha

2015-01-01

Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390 nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes. PMID:25989113

Spin current and second harmonic generation in non-collinear magnetic systems: the hydrodynamic model

NASA Astrophysics Data System (ADS)

Karashtin, E. A.; Fraerman, A. A.

2018-04-01

We report a theoretical study of the second harmonic generation in a noncollinearly magnetized conductive medium with equilibrium spin current. The hydrodynamic model is used to unravel the mechanism of a novel effect of the double frequency signal generation that is attributed to the spin current. According to our calculations, this second harmonic response appears due to the ‘non-adiabatic’ spin polarization of the conduction electrons induced by the oscillations in the non-uniform magnetization forced by the electric field of the electromagnetic wave. Together with the linear velocity response this leads to the generation of the double frequency spin current. This spin current is converted to the electric current via the inverse spin Hall effect, and the double-frequency electric current emits the second harmonic radiation. Possible experiment for detection of the new second harmonic effect is proposed.

Contrast-enhanced harmonic ultrasound imaging in ablation therapy for primary hepatocellular carcinoma.

PubMed

Minami, Yasunori; Kudo, Masatoshi

2009-12-31

The success rate of percutaneous radiofrequency (RF) ablation for hepatocellular carcinoma (HCC) depends on correct targeting via an imaging technique. However, RF electrode insertion is not completely accurate for residual HCC nodules because B-mode ultrasound (US), color Doppler, and power Doppler US findings cannot adequately differentiate between treated and viable residual tumor tissue. Electrode insertion is also difficult when we must identify the true HCC nodule among many large regenerated nodules in cirrhotic liver. Two breakthroughs in the field of US technology, harmonic imaging and the development of second-generation contrast agents, have recently been described and have demonstrated the potential to dramatically broaden the scope of US diagnosis of hepatic lesions. Contrast-enhanced harmonic US imaging with an intravenous contrast agent can evaluate small hypervascular HCC even when B-mode US cannot adequately characterize tumor. Therefore, contrast-enhanced harmonic US can facilitate RF ablation electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of contrast-enhanced harmonic US in ablation therapy for liver cancer is an efficient approach.

Enhanced dynamical stability with harmonic slip stacking

DOE PAGES

Eldred, Jeffrey; Zwaska, Robert

2016-10-26

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Enhanced dynamical stability with harmonic slip stacking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldred, Jeffrey; Zwaska, Robert

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Ultrasonic Imaging Techniques for Breast Cancer Detection

NASA Astrophysics Data System (ADS)

Goulding, N. R.; Marquez, J. D.; Prewett, E. M.; Claytor, T. N.; Nadler, B. R.

2008-02-01

Improving the resolution and specificity of current ultrasonic imaging technology is needed to enhance its relevance to breast cancer detection. A novel ultrasonic imaging reconstruction method is described that exploits classical straight-ray migration. This novel method improves signal processing for better image resolution and uses novel staging hardware options using a pulse-echo approach. A breast phantom with various inclusions is imaged using the classical migration method and is compared to standard computed tomography (CT) scans. These innovative ultrasonic methods incorporate ultrasound data acquisition, beam profile characterization, and image reconstruction. For an ultrasonic frequency of 2.25 MHz, imaged inclusions of approximately 1 cm are resolved and identified. Better resolution is expected with minor modifications. Improved image quality and resolution enables earlier detection and more accurate diagnoses of tumors thus reducing the number of biopsies performed, increasing treatment options, and lowering remission percentages. Using these new techniques the inclusions in the phantom are resolved and compared to the results of standard methods. Refinement of this application using other imaging techniques such as time-reversal mirrors (TRM), synthetic aperture focusing technique (SAFT), decomposition of the time reversal operator (DORT), and factorization methods is also discussed.

Tumor margin detection using optical biopsy techniques

NASA Astrophysics Data System (ADS)

Zhou, Yan; Liu, Cheng-hui; Li, Jiyou; Li, Zhongwu; Zhou, Lixin; Chen, Ke; Pu, Yang; He, Yong; Zhu, Ke; Li, Qingbo; Alfano, Robert R.

2014-03-01

The aim of this study is to use the Resonance Raman (RR) and fluorescence spectroscopic technique for tumor margin detection with high accuracy based on native molecular fingerprints of breast and gastrointestinal (GI) tissues. This tumor margins detection method utilizes advantages of RR spectroscopic technique in situ and in real-time to diagnose tumor changes providing powerful tools for clinical guiding intraoperative margin assessments and postoperative treatments. The tumor margin detection procedures by RR spectroscopy were taken by scanning lesion from center or around tumor region in ex-vivo to find the changes in cancerous tissues with the rim of normal tissues using the native molecular fingerprints. The specimens used to analyze tumor margins include breast and GI carcinoma and normal tissues. The sharp margin of the tumor was found by the changes of RR spectral peaks within 2 mm distance. The result was verified using fluorescence spectra with 300 nm, 320 nm and 340 nm excitation, in a typical specimen of gastric cancerous tissue within a positive margin in comparison with normal gastric tissues. This study demonstrates the potential of RR and fluorescence spectroscopy as new approaches with labeling free to determine the intraoperative margin assessment.

Neuroimaging techniques for memory detection: scientific, ethical, and legal issues.

PubMed

Meegan, Daniel V

2008-01-01

There is considerable interest in the use of neuroimaging techniques for forensic purposes. Memory detection techniques, including the well-publicized Brain Fingerprinting technique (Brain Fingerprinting Laboratories, Inc., Seattle WA), exploit the fact that the brain responds differently to sensory stimuli to which it has been exposed before. When a stimulus is specifically associated with a crime, the resulting brain activity should differentiate between someone who was present at the crime and someone who was not. This article reviews the scientific literature on three such techniques: priming, old/new, and P300 effects. The forensic potential of these techniques is evaluated based on four criteria: specificity, automaticity, encoding flexibility, and longevity. This article concludes that none of the techniques are devoid of forensic potential, although much research is yet to be done. Ethical issues, including rights to privacy and against self-incrimination, are discussed. A discussion of legal issues concludes that current memory detection techniques do not yet meet United States standards of legal admissibility.

QED effects induced harmonics generation in extreme intense laser foil interaction

NASA Astrophysics Data System (ADS)

Yu, J. Y.; Yuan, T.; Liu, W. Y.; Chen, M.; Luo, W.; Weng, S. M.; Sheng, Z. M.

2018-04-01

A new mechanism of harmonics generation (HG) induced by quantum electrodynamics (QED) effects in extreme intense laser foil interaction is found and investigated by particle-in-cell (PIC) simulations. When two laser pulses with identical intensities of 1.6× {10}24 {{W}} {{{cm}}}-2 are counter-incident on a thin foil target, harmonics emission is observed in their reflected electromagnetic waves. Such harmonics radiation is excited due to transversely oscillating electric currents coming from the vibration of QED effect generated {e}-{e}+ pairs. The effects of laser intensity and polarization were studied. By distinguishing the cascade depth of generated photons and pairs, the influence of QED cascades on HG was analyzed. Although the current HG is not an efficient way for radiation source applications, it may provide a unique way to detect the QED processes in the near future ultra-relativistic laser solid interactions.

Harmonization of urine albumin/creatinine ratio (ACR) results: a study based on an external quality assessment program in Polish laboratories.

PubMed

Ćwiklińska, Agnieszka; Dąbrowska, Hanna; Kowalski, Robert; Kuchta, Agnieszka; Kortas-Stempak, Barbara; Fijałkowska, Aleksandra; Bednarczuk, Gabriela; Jankowski, Maciej

2018-05-11

The ratio of albumin to creatinine (ACR) is an important parameter used for detection of albuminuria in patients with early kidney damage. The aim of the study was to evaluate the harmonization of ACR results among Polish participants in an international external quality assessment (EQA) program, and to evaluate the impact of albumin and creatinine analytical performance on the harmonization of ACR results. We analyzed 182 results of albumin, 202 of creatinine, and 180 of ACR obtained from Polish laboratories in an EQA program organized by Labquality. The dispersion of the results in surveys and percentage differences between the results and target values were calculated. Moreover, differences between method groups were assessed. The inter-laboratory coefficient of variation (CV) for ACR was 36%. Only 74% of results of Polish laboratories were within the target limits; for 11% of the results, an incorrect albuminuria category would have been reported. The inter-laboratory CV for albumin was 20%, 2.6-fold higher than for creatinine. Significant differences between method groups for albumin determination have been observed, even when the same measurement technique was used. The greatest difference between two groups was 23%, 2.5-fold greater in comparison to creatinine. There is an insufficient harmonization of ACR values among Polish laboratories, caused mainly by urine albumin analytical performance. Given the important role of ACR in the classification, monitoring and treatment of kidney damage, the harmonization of albumin measurements is crucial and urgently needed.

Fundamentals of electrochemical detection techniques for CE and MCE.

PubMed

Kubán, Pavel; Hauser, Peter C

2009-10-01

The electroanalytical techniques of amperometry, conductometry and potentiometry match well with the instrumental simplicity of CE. Indeed, all three detection approaches have been reported for electrophoretic separations. However, the characteristics of the three methods are quite distinct and these are not related to the optical methods more commonly employed. A detailed discussion of the underlying principles of each is given. The issue of possible effects of the separation voltage on the electrochemical detection techniques is considered in depth, and approaches to the elimination of such interferences are also discussed for each case.

MMS Observations of Harmonic Electromagnetic Cyclotron Waves

NASA Astrophysics Data System (ADS)

Usanova, M.; Ahmadi, N.; Ergun, R.; Trattner, K. J.; Fuselier, S. A.; Torbert, R. B.; Mauk, B.; Le Contel, O.; Giles, B. L.; Russell, C. T.; Burch, J.; Strangeway, R. J.

2017-12-01

Harmonically related electromagnetic ion cyclotron waves with the fundamental frequency near the O+ cyclotron frequency were observed by the four MMS spacecraft on May 20, 2016. The wave activity was detected by the spacecraft on their inbound passage through the Earth's morning magnetosphere during generally quiet geomagnetic conditions but enhanced solar wind dynamic pressure. It was also associated with an enhancement of energetic H+ and O+ ions. The waves are seen in both magnetic and electric fields, formed by over ten higher order harmonics, most pronounced in the electric field. The wave activity lasted for about an hour with some wave packets giving rise to short-lived structures extending from Hz to kHz range. These observations are particularly interesting since they suggest cross-frequency coupling between the lower and higher frequency modes. Further work will focus on examining the nature and role of these waves in the energetic particle dynamics from a theoretical perspective.

Harmonic motion imaging for abdominal tumor detection and high-intensity focused ultrasound ablation monitoring: an in vivo feasibility study in a transgenic mouse model of pancreatic cancer.

PubMed

Chen, Hong; Hou, Gary Y; Han, Yang; Payen, Thomas; Palermo, Carmine F; Olive, Kenneth P; Konofagou, Elisa E

2015-09-01

Harmonic motion imaging (HMI) is a radiationforce- based elasticity imaging technique that tracks oscillatory tissue displacements induced by sinusoidal ultrasonic radiation force to assess the resulting oscillatory displacement denoting the underlying tissue stiffness. The objective of this study was to evaluate the feasibility of HMI in pancreatic tumor detection and high-intensity focused ultrasound (HIFU) treatment monitoring. The HMI system consisted of a focused ultrasound transducer, which generated sinusoidal radiation force to induce oscillatory tissue motion at 50 Hz, and a diagnostic ultrasound transducer, which detected the axial tissue displacements based on acquired radio-frequency signals using a 1-D cross-correlation algorithm. For pancreatic tumor detection, HMI images were generated for pancreatic tumors in transgenic mice and normal pancreases in wild-type mice. The obtained HMI images showed a high contrast between normal and malignant pancreases with an average peak-to-peak HMI displacement ratio of 3.2. Histological analysis showed that no tissue damage was associated with HMI when it was used for the sole purpose of elasticity imaging. For pancreatic tumor ablation monitoring, the focused ultrasound transducer was operated at a higher acoustic power and longer pulse length than that used in tumor detection to simultaneously induce HIFU thermal ablation and oscillatory tissue displacements, allowing HMI monitoring without interrupting tumor ablation. HMI monitoring of HIFU ablation found significant decreases in the peak-to-peak HMI displacements before and after HIFU ablation with a reduction rate ranging from 15.8% to 57.0%. The formation of thermal lesions after HIFU exposure was confirmed by histological analysis. This study demonstrated the feasibility of HMI in abdominal tumor detection and HIFU ablation monitoring.

Harmonization of multi-site diffusion tensor imaging data.

PubMed

Fortin, Jean-Philippe; Parker, Drew; Tunç, Birkan; Watanabe, Takanori; Elliott, Mark A; Ruparel, Kosha; Roalf, David R; Satterthwaite, Theodore D; Gur, Ruben C; Gur, Raquel E; Schultz, Robert T; Verma, Ragini; Shinohara, Russell T

2017-11-01

Diffusion tensor imaging (DTI) is a well-established magnetic resonance imaging (MRI) technique used for studying microstructural changes in the white matter. As with many other imaging modalities, DTI images suffer from technical between-scanner variation that hinders comparisons of images across imaging sites, scanners and over time. Using fractional anisotropy (FA) and mean diffusivity (MD) maps of 205 healthy participants acquired on two different scanners, we show that the DTI measurements are highly site-specific, highlighting the need of correcting for site effects before performing downstream statistical analyses. We first show evidence that combining DTI data from multiple sites, without harmonization, may be counter-productive and negatively impacts the inference. Then, we propose and compare several harmonization approaches for DTI data, and show that ComBat, a popular batch-effect correction tool used in genomics, performs best at modeling and removing the unwanted inter-site variability in FA and MD maps. Using age as a biological phenotype of interest, we show that ComBat both preserves biological variability and removes the unwanted variation introduced by site. Finally, we assess the different harmonization methods in the presence of different levels of confounding between site and age, in addition to test robustness to small sample size studies. Copyright © 2017 Elsevier Inc. All rights reserved.

The Local Stellar Velocity Field via Vector Spherical Harmonics

NASA Technical Reports Server (NTRS)

Markarov, V. V.; Murphy, D. W.

2007-01-01

We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism. We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not corrected for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star. The Oort parameters determined by a straightforward least-squares adjustment in vector spherical harmonics are A=14.0 +/- 1.4, B=13.1 +/- 1.2, K=1.1 +/- 1.8, and C=2.9 +/- 1.4 km s(exp -1) kpc(exp -1). The physical meaning and the implications of these parameters are discussed in the framework of a general linear model of the velocity field. We find a few statistically significant higher degree harmonic terms that do not correspond to any parameters in the classical linear model. One of them, a third-degree electric harmonic, is tentatively explained as the response to a negative linear gradient of rotation velocity with distance from the Galactic plane, which we estimate at approximately -20 km s(exp -1) kpc(exp -1). A similar vertical gradient of rotation velocity has been detected for more distant stars representing the thick disk (z greater than 1 kpc

Approximating high angular resolution apparent diffusion coefficient profiles using spherical harmonics under BiGaussian assumption

NASA Astrophysics Data System (ADS)

Cao, Ning; Liang, Xuwei; Zhuang, Qi; Zhang, Jun

2009-02-01

Magnetic Resonance Imaging (MRI) techniques have achieved much importance in providing visual and quantitative information of human body. Diffusion MRI is the only non-invasive tool to obtain information of the neural fiber networks of the human brain. The traditional Diffusion Tensor Imaging (DTI) is only capable of characterizing Gaussian diffusion. High Angular Resolution Diffusion Imaging (HARDI) extends its ability to model more complex diffusion processes. Spherical harmonic series truncated to a certain degree is used in recent studies to describe the measured non-Gaussian Apparent Diffusion Coefficient (ADC) profile. In this study, we use the sampling theorem on band-limited spherical harmonics to choose a suitable degree to truncate the spherical harmonic series in the sense of Signal-to-Noise Ratio (SNR), and use Monte Carlo integration to compute the spherical harmonic transform of human brain data obtained from icosahedral schema.

Design-for-Hardware-Trust Techniques, Detection Strategies and Metrics for Hardware Trojans

DTIC Science & Technology

2015-12-14

down  both  rising  and  falling  transitions.  For  Trojan   detection ,   one   fault ,   slow-­‐to-­‐rise  or   slow-­‐to...in Jan. 2016. Through the course of this project we developed novel hardware Trojan detection techniques based on clock sweeping. The technique takes...algorithms to detect minor changes due to Trojan and compared them with those changes made by process variations. This technique was implemented on

Lip boundary detection techniques using color and depth information

NASA Astrophysics Data System (ADS)

Kim, Gwang-Myung; Yoon, Sung H.; Kim, Jung H.; Hur, Gi Taek

2002-01-01

This paper presents our approach to using a stereo camera to obtain 3-D image data to be used to improve existing lip boundary detection techniques. We show that depth information as provided by our approach can be used to significantly improve boundary detection systems. Our system detects the face and mouth area in the image by using color, geometric location, and additional depth information for the face. Initially, color and depth information can be used to localize the face. Then we can determine the lip region from the intensity information and the detected eye locations. The system has successfully been used to extract approximate lip regions using RGB color information of the mouth area. Merely using color information is not robust because the quality of the results may vary depending on light conditions, background, and the human race. To overcome this problem, we used a stereo camera to obtain 3-D facial images. 3-D data constructed from the depth information along with color information can provide more accurate lip boundary detection results as compared to color only based techniques.

Double optical gating of high-order harmonic generation with carrier-envelope phase stabilized lasers.

PubMed

Mashiko, Hiroki; Gilbertson, Steve; Li, Chengquan; Khan, Sabih D; Shakya, Mahendra M; Moon, Eric; Chang, Zenghu

2008-03-14

We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2 pi radians.

Double Optical Gating of High-Order Harmonic Generation with Carrier-Envelope Phase Stabilized Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashiko, Hiroki; Gilbertson, Steve; Li, Chengquan

2008-03-14

We demonstrated a novel optical switch to control the high-order harmonic generation process so that single attosecond pulses can be generated with multiple-cycle pulses. The technique combines two powerful optical gating methods: polarization gating and two-color gating. An extreme ultraviolet supercontinuum supporting 130 as was generated with neon gas using 9 fs laser pulses. We discovered a unique dependence of the harmonic spectra on the carrier-envelope phase of the laser fields, which repeats every 2{pi} radians.

2.32 THz quantum cascade laser frequency-locked to the harmonic of a microwave synthesizer source.

PubMed

Danylov, Andriy A; Light, Alexander R; Waldman, Jerry; Erickson, Neal R; Qian, Xifeng; Goodhue, William D

2012-12-03

Frequency stabilization of a THz quantum cascade laser (QCL) to the harmonic of a microwave source has been accomplished using a Schottky diode waveguide mixer designed for harmonic mixing. The 2.32 THz, 1.0 milliwatt CW QCL is coupled into the signal port of the mixer and a 110 GHz signal, derived from a harmonic of a microwave synthesizer, is coupled into the IF port. The difference frequency between the 21st harmonic of 110 GHz and the QCL is used in a discriminator to adjust the QCL bias current to stabilize the frequency. The short-term frequency jitter is reduced from 550 kHz to 4.5 kHz (FWHM) and the long-term frequency drift is eliminated. This performance is compared to that of several other THz QCL frequency stabilization techniques.

Harmonic uniflow engine

DOEpatents

Bennett, Charles L.

2016-03-22

A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.

The harmonic organization of auditory cortex

PubMed Central

Wang, Xiaoqin

2013-01-01

A fundamental structure of sounds encountered in the natural environment is the harmonicity. Harmonicity is an essential component of music found in all cultures. It is also a unique feature of vocal communication sounds such as human speech and animal vocalizations. Harmonics in sounds are produced by a variety of acoustic generators and reflectors in the natural environment, including vocal apparatuses of humans and animal species as well as music instruments of many types. We live in an acoustic world full of harmonicity. Given the widespread existence of the harmonicity in many aspects of the hearing environment, it is natural to expect that it be reflected in the evolution and development of the auditory systems of both humans and animals, in particular the auditory cortex. Recent neuroimaging and neurophysiology experiments have identified regions of non-primary auditory cortex in humans and non-human primates that have selective responses to harmonic pitches. Accumulating evidence has also shown that neurons in many regions of the auditory cortex exhibit characteristic responses to harmonically related frequencies beyond the range of pitch. Together, these findings suggest that a fundamental organizational principle of auditory cortex is based on the harmonicity. Such an organization likely plays an important role in music processing by the brain. It may also form the basis of the preference for particular classes of music and voice sounds. PMID:24381544

The harmonic organization of auditory cortex.

PubMed

Wang, Xiaoqin

2013-12-17

A fundamental structure of sounds encountered in the natural environment is the harmonicity. Harmonicity is an essential component of music found in all cultures. It is also a unique feature of vocal communication sounds such as human speech and animal vocalizations. Harmonics in sounds are produced by a variety of acoustic generators and reflectors in the natural environment, including vocal apparatuses of humans and animal species as well as music instruments of many types. We live in an acoustic world full of harmonicity. Given the widespread existence of the harmonicity in many aspects of the hearing environment, it is natural to expect that it be reflected in the evolution and development of the auditory systems of both humans and animals, in particular the auditory cortex. Recent neuroimaging and neurophysiology experiments have identified regions of non-primary auditory cortex in humans and non-human primates that have selective responses to harmonic pitches. Accumulating evidence has also shown that neurons in many regions of the auditory cortex exhibit characteristic responses to harmonically related frequencies beyond the range of pitch. Together, these findings suggest that a fundamental organizational principle of auditory cortex is based on the harmonicity. Such an organization likely plays an important role in music processing by the brain. It may also form the basis of the preference for particular classes of music and voice sounds.

Application of neutron interrogation techniques to corrosion detection

NASA Technical Reports Server (NTRS)

Birt, E. A.; Namkung, M.; Vulcan, W.; Welsh, R. E.

1991-01-01

This paper discusses a technique which may be able to detect corrosion by determining the presence of oxygen at the corroded site via a neutron inelastic gamma reaction. Initial experiments have been performed using a Pu-239/Be neutron source and a NaI(T1) gamma-ray detector. From the results it was concluded that a 1 mm thickness of aluminum oxide would not be detected.

Apple Mealiness Detection Using Hyperspectral Scattering Technique

USDA-ARS?s Scientific Manuscript database

Mealiness is a symptom of internal fruit disorder, which is characterized by abnormal softness and lack of free juice in the fruit. This research investigated the potential of hyperspectral scattering technique for detecting mealy apples. Spectral scattering profiles between 600 nm and 1,000 nm were...

In vivo time-harmonic multifrequency elastography of the human liver

NASA Astrophysics Data System (ADS)

Tzschätzsch, Heiko; Ipek-Ugay, Selcan; Guo, Jing; Streitberger, Kaspar-Josche; Gentz, Enno; Fischer, Thomas; Klaua, Robert; Schultz, Michael; Braun, Jürgen; Sack, Ingolf

2014-04-01

Elastography is capable of noninvasively detecting hepatic fibrosis by imposing mechanical stress and measuring the viscoelastic response in the liver. Magnetic resonance elastography (MRE) relies on time-harmonic vibrations, while most dynamic ultrasound elastography methods employ transient stimulation methods. This study attempts to benefit from the advantages of time-harmonic tissue stimulation, i.e. relative insensitivity to obesity and ascites and mechanical approachability of the entire liver, and the advantages of ultrasound, i.e. time efficiency, low costs, and wide availability, by introducing in vivo time-harmonic elastography (THE) of the human liver using ultrasound and a broad range of harmonic stimulation frequencies. THE employs continuous harmonic shear vibrations at 7 frequencies from 30 to 60 Hz in a single examination and determines the elasticity and the viscosity of the liver from the dispersion of the shear wave speed within the applied frequency range. The feasibility of the method is demonstrated in the livers of eight healthy volunteers and a patient with cirrhosis. Multifrequency MRE at the same drive frequencies was used as elastographic reference method. Similar values of shear modulus and shear viscosity according the Kelvin-Voigt model were obtained by MRE and THE, indicating that the new method is suitable for in vivo quantification of the shear viscoelastic properties of the liver, however, in real-time and at a fraction of the costs of MRE. In conclusion, THE may provide a useful tool for fast assessment of the viscoelastic properties of the liver at low costs and without limitations in obesity, ascites or hemochromatosis.

Planetary Gearbox Fault Detection Using Vibration Separation Techniques

NASA Technical Reports Server (NTRS)

Lewicki, David G.; LaBerge, Kelsen E.; Ehinger, Ryan T.; Fetty, Jason

2011-01-01

Studies were performed to demonstrate the capability to detect planetary gear and bearing faults in helicopter main-rotor transmissions. The work supported the Operations Support and Sustainment (OSST) program with the U.S. Army Aviation Applied Technology Directorate (AATD) and Bell Helicopter Textron. Vibration data from the OH-58C planetary system were collected on a healthy transmission as well as with various seeded-fault components. Planetary fault detection algorithms were used with the collected data to evaluate fault detection effectiveness. Planet gear tooth cracks and spalls were detectable using the vibration separation techniques. Sun gear tooth cracks were not discernibly detectable from the vibration separation process. Sun gear tooth spall defects were detectable. Ring gear tooth cracks were only clearly detectable by accelerometers located near the crack location or directly across from the crack. Enveloping provided an effective method for planet bearing inner- and outer-race spalling fault detection.

Selective harmonic elimination strategy in eleven level inverter for PV system with unbalanced DC sources

NASA Astrophysics Data System (ADS)

Ghoudelbourk, Sihem.; Dib, D.; Meghni, B.; Zouli, M.

2017-02-01

The paper deals with the multilevel converters control strategy for photovoltaic system integrated in distribution grids. The objective of the proposed work is to design multilevel inverters for solar energy applications so as to reduce the Total Harmonic Distortion (THD) and to improve the power quality. The multilevel inverter power structure plays a vital role in every aspect of the power system. It is easier to produce a high-power, high-voltage inverter with the multilevel structure. The topologies of multilevel inverter have several advantages such as high output voltage, lower total harmonic distortion (THD) and reduction of voltage ratings of the power semiconductor switching devices. The proposed control strategy ensures an implementation of selective harmonic elimination (SHE) modulation for eleven levels. SHE is a very important and efficient strategy of eliminating selected harmonics by judicious selection of the firing angles of the inverter. Harmonics elimination technique eliminates the need of the expensive low pass filters in the system. Previous research considered that constant and equal DC sources with invariant behavior; however, this research extends earlier work to include variant DC sources, which are typical of lead-acid batteries when used in system PV. This Study also investigates methods to minimize the total harmonic distortion of the synthesized multilevel waveform and to help balance the battery voltage. The harmonic elimination method was used to eliminate selected lower dominant harmonics resulting from the inverter switching action.

Self-starting harmonic frequency comb generation in a quantum cascade laser

NASA Astrophysics Data System (ADS)

Kazakov, Dmitry; Piccardo, Marco; Wang, Yongrui; Chevalier, Paul; Mansuripur, Tobias S.; Xie, Feng; Zah, Chung-en; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2017-12-01

Optical frequency combs1,2 establish a rigid phase-coherent link between microwave and optical domains and are emerging as high-precision tools in an increasing number of applications3. Frequency combs with large intermodal spacing are employed in the field of microwave photonics for radiofrequency arbitrary waveform synthesis4,5 and for the generation of terahertz tones of high spectral purity in future wireless communication networks6,7. Here, we demonstrate self-starting harmonic frequency comb generation with a terahertz repetition rate in a quantum cascade laser. The large intermodal spacing caused by the suppression of tens of adjacent cavity modes originates from a parametric contribution to the gain due to temporal modulations of population inversion in the laser8,9. Using multiheterodyne self-detection, the mode spacing of the harmonic comb is shown to be uniform to within 5 × 10-12 parts of the central frequency. This new harmonic comb state extends the range of applications of quantum cascade laser frequency combs10-13.

Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields.

PubMed

Dorney, Kevin M; Ellis, Jennifer L; Hernández-García, Carlos; Hickstein, Daniel D; Mancuso, Christopher A; Brooks, Nathan; Fan, Tingting; Fan, Guangyu; Zusin, Dmitriy; Gentry, Christian; Grychtol, Patrik; Kapteyn, Henry C; Murnane, Margaret M

2017-08-11

High harmonics driven by two-color counterrotating circularly polarized laser fields are a unique source of bright, circularly polarized, extreme ultraviolet, and soft x-ray beams, where the individual harmonics themselves are completely circularly polarized. Here, we demonstrate the ability to preferentially select either the right or left circularly polarized harmonics simply by adjusting the relative intensity ratio of the bichromatic circularly polarized driving laser field. In the frequency domain, this significantly enhances the harmonic orders that rotate in the same direction as the higher-intensity driving laser. In the time domain, this helicity-dependent enhancement corresponds to control over the polarization of the resulting attosecond waveforms. This helicity control enables the generation of circularly polarized high harmonics with a user-defined polarization of the underlying attosecond bursts. In the future, this technique should allow for the production of bright highly elliptical harmonic supercontinua as well as the generation of isolated elliptically polarized attosecond pulses.

Harmonic motion imaging for focused ultrasound (HMIFU): a fully integrated technique for sonication and monitoring of thermal ablation in tissues.

PubMed

Maleke, C; Konofagou, E E

2008-03-21

FUS (focused ultrasound), or HIFU (high-intensity-focused ultrasound) therapy, a minimally or non-invasive procedure that uses ultrasound to generate thermal necrosis, has been proven successful in several clinical applications. This paper discusses a method for monitoring thermal treatment at different sonication durations (10 s, 20 s and 30 s) using the amplitude-modulated (AM) harmonic motion imaging for focused ultrasound (HMIFU) technique in bovine liver samples in vitro. The feasibility of HMI for characterizing mechanical tissue properties has previously been demonstrated. Here, a confocal transducer, combining a 4.68 MHz therapy (FUS) and a 7.5 MHz diagnostic (pulse-echo) transducer, was used. The therapy transducer was driven by a low-frequency AM continuous signal at 25 Hz, producing a stable harmonic radiation force oscillating at the modulation frequency. A pulser/receiver was used to drive the pulse-echo transducer at a pulse repetition frequency (PRF) of 5.4 kHz. Radio-frequency (RF) signals were acquired using a standard pulse-echo technique. The temperature near the ablation region was simultaneously monitored. Both RF signals and temperature measurements were obtained before, during and after sonication. The resulting axial tissue displacement was estimated using one-dimensional cross correlation. When temperature at the focal zone was above 48 degrees C during heating, the coagulation necrosis occurred and tissue damage was irreversible. The HMI displacement profiles in relation to the temperature and sonication durations were analyzed. At the beginning of heating, the temperature at the focus increased sharply, while the tissue stiffness decreased resulting in higher HMI displacements. This was confirmed by an increase of 0.8 microm degrees C(-1)(r=0.93, p<.005). After sustained heating, the tissue became irreversibly stiffer, followed by an associated decrease in the HMI displacement (-0.79 microm degrees C(-1), r=-0.92, p<0.001). Repeated

Experimental and simulation studies on the behavior of signal harmonics in magnetic particle imaging.

PubMed

Murase, Kenya; Konishi, Takashi; Takeuchi, Yuki; Takata, Hiroshige; Saito, Shigeyoshi

2013-07-01

Our purpose in this study was to investigate the behavior of signal harmonics in magnetic particle imaging (MPI) by experimental and simulation studies. In the experimental studies, we made an apparatus for MPI in which both a drive magnetic field (DMF) and a selection magnetic field (SMF) were generated with a Maxwell coil pair. The MPI signals from magnetic nanoparticles (MNPs) were detected with a solenoid coil. The odd- and even-numbered harmonics were calculated by Fourier transformation with or without background subtraction. The particle size of the MNPs was measured by transmission electron microscopy (TEM), dynamic light-scattering, and X-ray diffraction methods. In the simulation studies, the magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively. The odd- and even-numbered harmonics were calculated by Fourier transformation under various conditions of DMF and SMF and for three different particle sizes. The behavior of the harmonics largely depended on the size of the MNPs. When we used the particle size obtained from the TEM image, the simulation results were most similar to the experimental results. The similarity between the experimental and simulation results for the even-numbered harmonics was better than that for the odd-numbered harmonics. This was considered to be due to the fact that the odd-numbered harmonics were more sensitive to background subtraction than were the even-numbered harmonics. This study will be useful for a better understanding, optimization, and development of MPI and for designing MNPs appropriate for MPI.

Computer model for harmonic ultrasound imaging.

PubMed

Li, Y; Zagzebski, J A

2000-01-01

Harmonic ultrasound imaging has received great attention from ultrasound scanner manufacturers and researchers. In this paper, we present a computer model that can generate realistic harmonic images. In this model, the incident ultrasound is modeled after the "KZK" equation, and the echo signal is modeled using linear propagation theory because the echo signal is much weaker than the incident pulse. Both time domain and frequency domain numerical solutions to the "KZK" equation were studied. Realistic harmonic images of spherical lesion phantoms were generated for scans by a circular transducer. This model can be a very useful tool for studying the harmonic buildup and dissipation processes in a nonlinear medium, and it can be used to investigate a wide variety of topics related to B-mode harmonic imaging.

Computer model for harmonic ultrasound imaging.

PubMed

Li, Y; Zagzebski, J A

2000-01-01

Harmonic ultrasound imaging has received great attention from ultrasound scanner manufacturers and researchers. Here, the authors present a computer model that can generate realistic harmonic images. In this model, the incident ultrasound is modeled after the "KZK" equation, and the echo signal is modeled using linear propagation theory because the echo signal is much weaker than the incident pulse. Both time domain and frequency domain numerical solutions to the "KZK" equation were studied. Realistic harmonic images of spherical lesion phantoms were generated for scans by a circular transducer. This model can be a very useful tool for studying the harmonic buildup and dissipation processes in a nonlinear medium, and it can be used to investigate a wide variety of topics related to B-mode harmonic imaging.

Region Spherical Harmonic Magnetic Modeling from Near-Surface and Satellite-Altitude Anomlaies

NASA Technical Reports Server (NTRS)

Kim, Hyung Rae; von Frese, Ralph R. B.; Taylor, Patrick T.

2013-01-01

The compiled near-surface data and satellite crustal magnetic measured data are modeled with a regionally concentrated spherical harmonic presentation technique over Australia and Antarctica. Global crustal magnetic anomaly studies have used a spherical harmonic analysis to represent the Earth's magnetic crustal field. This global approach, however is best applied where the data are uniformly distributed over the entire Earth. Satellite observations generally meet this requirement, but unequally distributed data cannot be easily adapted in global modeling. Even for the satellite observations, due to the errors spread over the globe, data smoothing is inevitable in the global spherical harmonic presentations. In addition, global high-resolution modeling requires a great number of global spherical harmonic coefficients for the regional presentation of crustal magnetic anomalies, whereas a lesser number of localized spherical coefficients will satisfy. We compared methods in both global and regional approaches and for a case where the errors were propagated outside the region of interest. For observations from the upcoming Swarm constellation, the regional modeling will allow the production a lesser number of spherical coefficients that are relevant to the region of interest

High order harmonics anomaly of jet screech

NASA Astrophysics Data System (ADS)

Chen, Zhe; Wu, Jiu Hui; Ren, A.-Dan; Chen, Xin

2018-05-01

Imperfectly expanded supersonic jets under strong screech could generate both fundamental screech tones and multiple tones at the harmonics of the fundamental frequency. The paper compares the fundamental frequency of jets from both AR = 3 (Aspect Ratio) and AR = 4 rectangular nozzles, and conducts analysis of harmonics on Sound Pressure Level (SPL) spectrums of jet noise. The research suggests that the fundamental frequency of the first two- or three-order harmonics increases when the Nozzle Pressure Ratio (NPR) decreases, whereas the highest order harmonic decreases when the NPR decreases. Besides, the paper also observes the differences between the highest order harmonics and other harmonics that have never been reported before. Further analysis on flow field schlieren of AR = 3 nozzle indicates that the highest order harmonic is the outcome of interaction between second shock-cell and nonlinear instable wave. The revolution of these high order harmonics can provide guidance for the prevention of small-scale structure fatigue damage. Moreover, the distribution test of the noises is also carried out to verify the high order harmonics anomaly, and indicate that the jet noise spreads mainly towards downstream while screech towards upstream. In addition, the broadband shock-associated noise spreads vertical to the jet flow and exhibits the feature of directivity.

Second harmonic generation at fatigue cracks by low-frequency Lamb waves: Experimental and numerical studies

NASA Astrophysics Data System (ADS)

Yang, Yi; Ng, Ching-Tai; Kotousov, Andrei; Sohn, Hoon; Lim, Hyung Jin

2018-01-01

This paper presents experimental and theoretical analyses of the second harmonic generation due to non-linear interaction of Lamb waves with a fatigue crack. Three-dimensional (3D) finite element (FE) simulations and experimental studies are carried out to provide physical insight into the mechanism of second harmonic generation. The results demonstrate that the 3D FE simulations can provide a reasonable prediction on the second harmonic generated due to the contact nonlinearity at the fatigue crack. The effect of the wave modes on the second harmonic generation is also investigated in detail. It is found that the magnitude of the second harmonic induced by the interaction of the fundamental symmetric mode (S0) of Lamb wave with the fatigue crack is much higher than that by the fundamental anti-symmetric mode (A0) of Lamb wave. In addition, a series of parametric studies using 3D FE simulations are conducted to investigate the effect of the fatigue crack length to incident wave wavelength ratio, and the influence of the excitation frequency on the second harmonic generation. The outcomes show that the magnitude and directivity pattern of the generated second harmonic depend on the fatigue crack length to incident wave wavelength ratio as well as the ratio of S0 to A0 incident Lamb wave amplitude. In summary, the findings of this study can further advance the use of second harmonic generation in damage detection.

Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trull, J.; Wang, B.; Parra, A.

2015-06-01

Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

Fresh Slice Self-Seeding and Fresh Slice Harmonic Lasing at LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amann, J.W.

We present results from the successful demonstration of fresh slice self-seeding at the Linac Coherent Light Source (LCLS).* The performance is compared with SASE and regular self-seeding at photon energy of 5.5 keV, resulting in a relative average brightness increase of a factor of 12 and a factor of 2 respectively. Following this proof-of-principle we discuss the forthcoming plans to use the same technique** for fresh slice harmonic lasing in an upcoming experiment. The demonstration of fresh slice harmonic lasing provides an attractive solution for future XFELs aiming to achieve high efficiency, high brightness X-ray pulses at high photon energiesmore » (>12 keV).***« less

Phase-sensitive techniques applied to a micromachined vacuum sensor

NASA Astrophysics Data System (ADS)

Chapman, Glenn H.; Sawadsky, N.; Juneja, P. P.

1996-09-01

Phase sensitive AC measurement techniques are particularly applicable to micromachined sensors detecting temperature changes at a sensor caused by a microheater. The small mass produces rapid thermal response to AC signals which are easily detectable with lock-in amplifiers. Phase sensitive measurements were applied to a CMOS compatible micromachined pressure sensor consisting a polysilicon sense line, 760 microns long, on an oxide microbridge separated by 6 microns on each horizontal side from similar polysilicon heaters, all over a micromachined cavity. Sinusoidal heater signals at 32 Hz induced temperature caused sense line resistance changes at 64 Hz. The lock-in detected this as a first harmonic sense resistor voltage from a DC constant sense current. By observing the first harmonic the lock-in rejects all AC coupling of noise by capacitance or inductance, by measuring only those signals at the 64 Hz frequency and with a fixed phase relationship to the heater driver signals. This sensor produces large signals near atmospheric pressure, declining to 7 (mu) V below 0.1 mTorr. Phase measurements between 760 and 100 Torr where the air's thermal conductivity changes little, combined with amplitude changes at low pressure generate a pressure measurement accurate at 5 percent from 760 Torr to 10 mTorr, sensing of induced temperature changes of 0.001 degree C.

Spherical Harmonic Analysis of Particle Velocity Distribution Function: Comparison of Moments and Anisotropies using Cluster Data

NASA Technical Reports Server (NTRS)

Gurgiolo, Chris; Vinas, Adolfo F.

2009-01-01

This paper presents a spherical harmonic analysis of the plasma velocity distribution function using high-angular, energy, and time resolution Cluster data obtained from the PEACE spectrometer instrument to demonstrate how this analysis models the particle distribution function and its moments and anisotropies. The results show that spherical harmonic analysis produced a robust physical representation model of the velocity distribution function, resolving the main features of the measured distributions. From the spherical harmonic analysis, a minimum set of nine spectral coefficients was obtained from which the moment (up to the heat flux), anisotropy, and asymmetry calculations of the velocity distribution function were obtained. The spherical harmonic method provides a potentially effective "compression" technique that can be easily carried out onboard a spacecraft to determine the moments and anisotropies of the particle velocity distribution function for any species. These calculations were implemented using three different approaches, namely, the standard traditional integration, the spherical harmonic (SPH) spectral coefficients integration, and the singular value decomposition (SVD) on the spherical harmonic methods. A comparison among the various methods shows that both SPH and SVD approaches provide remarkable agreement with the standard moment integration method.

Multimodal technique to eliminate humidity interference for specific detection of ethanol.

PubMed

Jalal, Ahmed Hasnain; Umasankar, Yogeswaran; Gonzalez, Pablo J; Alfonso, Alejandro; Bhansali, Shekhar

2017-01-15

Multimodal electrochemical technique incorporating both open circuit potential (OCP) and amperometric techniques have been conceptualized and implemented to improve the detection of specific analyte in systems where more than one analyte is present. This approach has been demonstrated through the detection of ethanol while eliminating the contribution of water in a micro fuel cell sensor system. The sensor was interfaced with LMP91000 potentiostat, controlled through MSP430F5529LP microcontroller to implement an auto-calibration algorithm tailored to improve the detection of alcohol. The sensor was designed and fabricated as a three electrode system with Nafion as a proton exchange membrane (PEM). The electrochemical signal of the interfering phase (water) was eliminated by implementing the multimodal electrochemical detection technique. The results were validated by comparing sensor and potentiostat performances with a commercial sensor and potentiostat respectively. The results suggest that such a sensing system can detect ethanol at concentrations as low as 5ppm. The structure and properties such as low detection limit, selectivity and miniaturized size enables potential application of this device in wearable transdermal alcohol measurements. Copyright © 2016 Elsevier B.V. All rights reserved.

Second-harmonic phonon spectroscopy of α -quartz

NASA Astrophysics Data System (ADS)

Winta, Christopher J.; Gewinner, Sandy; Schöllkopf, Wieland; Wolf, Martin; Paarmann, Alexander

2018-03-01

We demonstrate midinfrared second-harmonic generation as a highly sensitive phonon spectroscopy technique that we exemplify using α -quartz (SiO2) as a model system. A midinfrared free-electron laser provides direct access to optical phonon resonances ranging from 350 to 1400 cm-1 . While the extremely wide tunability and high peak fields of a free-electron laser promote nonlinear spectroscopic studies—complemented by simultaneous linear reflectivity measurements—azimuthal scans reveal crystallographic symmetry information of the sample. Additionally, temperature-dependent measurements show how damping rates increase, phonon modes shift spectrally and in certain cases disappear completely when approaching Tc=846 K where quartz undergoes a structural phase transition from trigonal α -quartz to hexagonal β -quartz, demonstrating the technique's potential for studies of phase transitions.

Expansion into lattice harmonics in cubic symmetries

NASA Astrophysics Data System (ADS)

Kontrym-Sznajd, G.

2018-05-01

On the example of a few sets of sampling directions in the Brillouin zone, this work shows how important the choice of the cubic harmonics is on the quality of approximation of some quantities by a series of such harmonics. These studies led to the following questions: (1) In the case that for a given l there are several independent harmonics, can one use in the expansion only one harmonic with a given l?; (2) How should harmonics be ordered: according to l or, after writing them in terms of (x4 + y4 + z4)n (x2y2z2)m, according to their degree q = n + m? To enable practical applications of such harmonics, they are constructed in terms of the associated Legendre polynomials up to l = 26. It is shown that electron momentum densities, reconstructed from experimental data for ErGa3 and InGa3, are described much better by harmonics ordered with q.

Explaining the harmonic sequence paradox.

PubMed

Schmidt, Ulrich; Zimper, Alexander

2012-05-01

According to the harmonic sequence paradox, an expected utility decision maker's willingness to pay for a gamble whose expected payoffs evolve according to the harmonic series is finite if and only if his marginal utility of additional income becomes zero for rather low payoff levels. Since the assumption of zero marginal utility is implausible for finite payoff levels, expected utility theory - as well as its standard generalizations such as cumulative prospect theory - are apparently unable to explain a finite willingness to pay. This paper presents first an experimental study of the harmonic sequence paradox. Additionally, it demonstrates that the theoretical argument of the harmonic sequence paradox only applies to time-patient decision makers, whereas the paradox is easily avoided if time-impatience is introduced. ©2011 The British Psychological Society.

Second-harmonic patterned polarization-analyzed reflection confocal microscope

NASA Astrophysics Data System (ADS)

Okoro, Chukwuemeka; Toussaint, Kimani C.

2017-08-01

We introduce the second-harmonic patterned polarization-analyzed reflection confocal (SPPARC) microscope-a multimodal imaging platform that integrates Mueller matrix polarimetry with reflection confocal and second-harmonic generation (SHG) microscopy. SPPARC microscopy provides label-free three-dimensional (3-D), SHG-patterned confocal images that lend themselves to spatially dependent, linear polarimetric analysis for extraction of rich polarization information based on the Mueller calculus. To demonstrate its capabilities, we use SPPARC microscopy to analyze both porcine tendon and ligament samples and find differences in both circular degree-of-polarization and depolarization parameters. Moreover, using the collagen-generated SHG signal as an endogenous counterstain, we show that the technique can be used to provide 3-D polarimetric information of the surrounding extrafibrillar matrix plus cells or EFMC region. The unique characteristics of SPPARC microscopy holds strong potential for it to more accurately and quantitatively describe microstructural changes in collagen-rich samples in three spatial dimensions.

Efficient Second-Harmonic Generation in Nanocrystalline Silicon Nanoparticles.

PubMed

Makarov, Sergey V; Petrov, Mihail I; Zywietz, Urs; Milichko, Valentin; Zuev, Dmitry; Lopanitsyna, Natalia; Kuksin, Alexey; Mukhin, Ivan; Zograf, George; Ubyivovk, Evgeniy; Smirnova, Daria A; Starikov, Sergey; Chichkov, Boris N; Kivshar, Yuri S

2017-05-10

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

Dynamics and control of instrumented harmonic drives

NASA Technical Reports Server (NTRS)

Kazerooni, H.; Ellis, S. R. (Principal Investigator)

1995-01-01

Since torque in harmonic drives is transmitted by a pure couple, harmonic drives do not generate radial forces and therefore can be instrumented with torque sensors without interference from radial forces. The installation of torque sensors on the stationary component of harmonic drives (the Flexipline cup in this research work) produce backdrivability needed for robotic and telerobotic compliant maneuvers. Backdrivability of a harmonic drive, when used as torque increaser, means that the output shaft can be rotated via finite amount of torque. A high ratio harmonic drive is non-backdrivable because its output shaft cannot be turned by applying a torque on it. This article first develops the dynamic behavior of a harmonic drive, in particular the non-backdrivability, in terms of a sensitivity transfer function. The instrumentation of the harmonic drive with torque sensor is then described. This leads to a description of the control architecture which allows modulation of the sensitivity transfer function within the limits established by the closed-loop stability. A set of experiments on an active hand controller, powered by a DC motor coupled to an instrumented harmonic drive, is given to exhibit this method's limitations.

[Development of sample pretreatment techniques-rapid detection coupling methods for food security analysis].

PubMed

Huang, Yichun; Ding, Weiwei; Zhang, Zhuomin; Li, Gongke

2013-07-01

This paper summarizes the recent developments of the rapid detection methods for food security, such as sensors, optical techniques, portable spectral analysis, enzyme-linked immunosorbent assay, portable gas chromatograph, etc. Additionally, the applications of these rapid detection methods coupled with sample pretreatment techniques in real food security analysis are reviewed. The coupling technique has the potential to provide references to establish the selective, precise and quantitative rapid detection methods in food security analysis.

Fluorescence hyperspectral imaging technique for foreign substance detection on fresh-cut lettuce.

PubMed

Mo, Changyeun; Kim, Giyoung; Kim, Moon S; Lim, Jongguk; Cho, Hyunjeong; Barnaby, Jinyoung Yang; Cho, Byoung-Kwan

2017-09-01

Non-destructive methods based on fluorescence hyperspectral imaging (HSI) techniques were developed to detect worms on fresh-cut lettuce. The optimal wavebands for detecting the worms were investigated using the one-way ANOVA and correlation analyses. The worm detection imaging algorithms, RSI-I (492-626)/492 , provided a prediction accuracy of 99.0%. The fluorescence HSI techniques indicated that the spectral images with a pixel size of 1 × 1 mm had the best classification accuracy for worms. The overall results demonstrate that fluorescence HSI techniques have the potential to detect worms on fresh-cut lettuce. In the future, we will focus on developing a multi-spectral imaging system to detect foreign substances such as worms, slugs and earthworms on fresh-cut lettuce. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

NASA Technical Reports Server (NTRS)

Holliday, Ezekiel S. (Inventor)

2014-01-01

Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

Biosensor-based microRNA detection: techniques, design, performance, and challenges.

PubMed

Johnson, Blake N; Mutharasan, Raj

2014-04-07

The current state of biosensor-based techniques for amplification-free microRNA (miRNA) detection is critically reviewed. Comparison with non-sensor and amplification-based molecular techniques (MTs), such as polymerase-based methods, is made in terms of transduction mechanism, associated protocol, and sensitivity. Challenges associated with miRNA hybridization thermodynamics which affect assay selectivity and amplification bias are briefly discussed. Electrochemical, electromechanical, and optical classes of miRNA biosensors are reviewed in terms of transduction mechanism, limit of detection (LOD), time-to-results (TTR), multiplexing potential, and measurement robustness. Current trends suggest that biosensor-based techniques (BTs) for miRNA assay will complement MTs due to the advantages of amplification-free detection, LOD being femtomolar (fM)-attomolar (aM), short TTR, multiplexing capability, and minimal sample preparation requirement. Areas of future importance in miRNA BT development are presented which include focus on achieving high measurement confidence and multiplexing capabilities.

Aspartate Aminotransferase (AST/GOT) and Alanine Aminotransferase (ALT/GPT) Detection Techniques

PubMed Central

Huang, Xing-Jiu; Choi, Yang-Kyu; Im, Hyung-Soon; Yarimaga, Oktay; Yoon, Euisik; Kim, Hak-Sung

2006-01-01

The levels of aspartate aminotransferase (AST/GOT) and alanine aminotransferase (ALT/GPT) in serum can help people diagnose body tissues especially the heart and the liver are injured or not. This article provides a comprehensive review of research activities that concentrate on AST/GOT and ALT/GPT detection techniques due to their clinical importance. The detection techniques include colorimetric, spectrophotometric, chemiluminescence, chromatography, fluorescence and UV absorbance, radiochemical, and electrochemical techniques. We devote the most attention on experimental principle. In some methods a few representative devices and important conclusions are presented.

Harmonic engine

DOEpatents

Bennett, Charles L [Livermore, CA

2009-10-20

A high efficiency harmonic engine based on a resonantly reciprocating piston expander that extracts work from heat and pressurizes working fluid in a reciprocating piston compressor. The engine preferably includes harmonic oscillator valves capable of oscillating at a resonant frequency for controlling the flow of working fluid into and out of the expander, and also preferably includes a shunt line connecting an expansion chamber of the expander to a buffer chamber of the expander for minimizing pressure variations in the fluidic circuit of the engine. The engine is especially designed to operate with very high temperature input to the expander and very low temperature input to the compressor, to produce very high thermal conversion efficiency.

Detection of genetically modified organisms in foods by DNA amplification techniques.

PubMed

García-Cañas, Virginia; Cifuentes, Alejandro; González, Ramón

2004-01-01

In this article, the different DNA amplification techniques that are being used for detecting genetically modified organisms (GMOs) in foods are examined. This study intends to provide an updated overview (including works published till June 2002) on the principal applications of such techniques together with their main advantages and drawbacks in GMO detection in foods. Some relevant facts on sampling, DNA isolation, and DNA amplification methods are discussed. Moreover; these analytical protocols are discuissed from a quantitative point of view, including the newest investigations on multiplex detection of GMOs in foods and validation of methods.

The design of a multi-harmonic step-tunable gyrotron

NASA Astrophysics Data System (ADS)

Qi, Xiang-Bo; Du, Chao-Hai; Zhu, Juan-Feng; Pan, Shi; Liu, Pu-Kun

2017-03-01

The theoretical study of a step-tunable gyrotron controlled by successive excitation of multi-harmonic modes is presented in this paper. An axis-encircling electron beam is employed to eliminate the harmonic mode competition. Physics images are depicted to elaborate the multi-harmonic interaction mechanism in determining the operating parameters at which arbitrary harmonic tuning can be realized by magnetic field sweeping to achieve controlled multiband frequencies' radiation. An important principle is revealed that a weak coupling coefficient under a high-harmonic interaction can be compensated by a high Q-factor. To some extent, the complementation between the high Q-factor and weak coupling coefficient makes the high-harmonic mode potential to achieve high efficiency. Based on a previous optimized magnetic cusp gun, the multi-harmonic step-tunable gyrotron is feasible by using harmonic tuning of first-to-fourth harmonic modes. Multimode simulation shows that the multi-harmonic gyrotron can operate on the 34 GHz first-harmonic TE11 mode, 54 GHz second-harmonic TE21 mode, 74 GHz third-harmonic TE31 mode, and 94 GHz fourth-harmonic TE41 mode, corresponding to peak efficiencies of 28.6%, 35.7%, 17.1%, and 11.4%, respectively. The multi-harmonic step-tunable gyrotron provides new possibilities in millimeter-terahertz source development especially for advanced terahertz applications.

Tripartite correlations over two octaves from cascaded harmonic generation

NASA Astrophysics Data System (ADS)

Olsen, M. K.

2018-03-01

We analyse the output quantum tripartite correlations from an intracavity nonlinear optical system which uses cascaded nonlinearities to produce both second and fourth harmonic outputs from an input field at the fundamental frequency. Using fully quantum equations of motion, we investigate two parameter regimes and show that the system produces tripartite inseparability, entanglement and EPR steering, with the detection of these depending on the correlations being considered.

Use of an untuned cavity for absolute power measurements of the harmonics above 100 GHz from an IMPATT oscillator

NASA Astrophysics Data System (ADS)

Llewellyn-Jones, D. T.; Knight, R. J.; Gebbie, H. A.

1980-07-01

A new technique of measuring absolute power exploiting an untuned cavity and Fourier spectroscopy has been used to examine the power spectrum of the harmonics and other overtones produced by a 95 GHz IMPATT oscillator. The conditions which favor the production of a rich harmonic spectrum are not those which maximize the fundamental power. Under some conditions of mismatch at the fundamental frequency it is possible to produce over 200 microW of harmonic power in the 100-200 GHz region comparable with the fundamental power from the oscillator.

Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

NASA Astrophysics Data System (ADS)

Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; Weber, Adam Z.; Ulsh, Michael

2016-11-01

Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H2) reactive mixture of H2/O2 in N2 impinging and reacting on a Pt catalytic surface. In this paper, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min-1) and gas flowrates (32.5 or 50 standard L min-1). Furthermore, a model is developed and validated for the technique, and it is subsequently used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.

The harmonic impact of electric vehicle battery charging

NASA Astrophysics Data System (ADS)

Staats, Preston Trent

The potential widespread introduction of the electric vehicle (EV) presents both opportunities and challenges to the power systems engineers who will be required to supply power to EV batteries. One of the challenges associated with EV battery charging comes from the potentially high harmonic currents associated with the conversion of ac power system voltages to dc EV battery voltages. Harmonic currents lead to increased losses in distribution circuits and reduced life expectancy of such power distribution components as capacitors and transformers. Harmonic current injections also cause harmonic voltages on power distribution networks. These distorted voltages can affect power system loads and specific standards exist regulating acceptable voltage distortion. This dissertation develops and presents the theory required to evaluate the electric vehicle battery charger as a harmonic distorting load and its possible harmonic impact on various aspects of power distribution systems. The work begins by developing a method for evaluating the net harmonic current injection of a large collection of EV battery chargers which accounts for variation in the start-time and initial battery state-of-charge between individual chargers. Next, this method is analyzed to evaluate the effect of input parameter variation on the net harmonic currents predicted by the model. We then turn to an evaluation of the impact of EV charger harmonic currents on power distribution systems, first evaluating the impact of these currents on a substation transformer and then on power distribution system harmonic voltages. The method presented accounts for the uncertainty in EV harmonic current injections by modeling the start-time and initial battery state-of-charge (SOC) of an individual EV battery charger as random variables. Thus, the net harmonic current, and distribution system harmonic voltages are formulated in a stochastic framework. Results indicate that considering variation in start-time and

Drop-off Detection with the Long Cane: Effects of Different Cane Techniques on Performance

PubMed Central

Kim, Dae Shik; Emerson, Robert Wall; Curtis, Amy

2010-01-01

This study compared the drop-off detection performance with the two-point touch and constant contact cane techniques using a repeated-measures design with a convenience sample of 15 cane users with visual impairments. The constant contact technique was superior to the two-point touch technique in the drop-off detection rate and the 50% detection threshold. The findings may help an orientation and mobility instructor select an appropriate technique for a particular client or training situation. PMID:21209791

From Pacemaker to Wearable: Techniques for ECG Detection Systems.

PubMed

Kumar, Ashish; Komaragiri, Rama; Kumar, Manjeet

2018-01-11

With the alarming rise in the deaths due to cardiovascular diseases (CVD), present medical research scenario places notable importance on techniques and methods to detect CVDs. As adduced by world health organization, technological proceeds in the field of cardiac function assessment have become the nucleus and heart of all leading research studies in CVDs in which electrocardiogram (ECG) analysis is the most functional and convenient tool used to test the range of heart-related irregularities. Most of the approaches present in the literature of ECG signal analysis consider noise removal, rhythm-based analysis, and heartbeat detection to improve the performance of a cardiac pacemaker. Advancements achieved in the field of ECG segments detection and beat classification have a limited evaluation and still require clinical approvals. In this paper, approaches on techniques to implement on-chip ECG detector for a cardiac pacemaker system are discussed. Moreover, different challenges regarding the ECG signal morphology analysis deriving from medical literature is extensively reviewed. It is found that robustness to noise, wavelet parameter choice, numerical efficiency, and detection performance are essential performance indicators required by a state-of-the-art ECG detector. Furthermore, many algorithms described in the existing literature are not verified using ECG data from the standard databases. Some ECG detection algorithms show very high detection performance with the total number of detected QRS complexes. However, the high detection performance of the algorithm is verified using only a few datasets. Finally, gaps in current advancements and testing are identified, and the primary challenge remains to be implementing bullseye test for morphology analysis evaluation.

Harmonized Medical Device Regulation: Need, Challenges, and Risks of not Harmonizing the Regulation in Asia

PubMed Central

Kaushik, A; Saini, KS; Anil, B; Rambabu, S

2010-01-01

Medical device sector is one of the most complex and challenging business segments of the healthcare industry with close collaboration between science and engineering. Despite the fact that Asia has 60% of the world population providing large market potential, Asian healthcare expenditure constitutes only 15% of the global healthcare expenditure. The accelerated ageing population and increasing prevalence of chronic disease are the key drivers that contribute toward the increase in the total healthcare expenditure on medical devices in the region. Several policies clearly showed the eagerness of the government to provide better healthcare infrastructure with better medical devices and facilities. The fundamental objective of the regulatory harmonization is to improve the efficiency of national economies and their ability to adopt to change and remain competitive. After the era of liberalization and globalization, the desires of developing economies is to ensure safety and performance of the product brought to their markets and for this harmonized regulation is an important tool for strengthening the same. If we talk about the industry need, then this approach will eliminate redundant requirements that do not contribute to safety and effectiveness. In addition, Asia is diverse in many respects and with it come the various challenges to harmonizing the regulation which includes diversity in culture, politics, economy, historical issues, etc. If, by any reason, the regulation of medical devices is not harmonized and consequently, the harmonized regulation is not adopted, then it leads to serious concerns like delayed or absent access to innovative technology, continued rise in the cost of medical therapies, etc. So this issue is written to attract all stakeholders to move toward the concept of harmonization, keeping in mind their need, challenges, and risks of not harmonizing the regulation as well. PMID:21331201

Harmonic Frequency Lowering

PubMed Central

Kirchberger, Martin

2016-01-01

A novel algorithm for frequency lowering in music was developed and experimentally tested in hearing-impaired listeners. Harmonic frequency lowering (HFL) combines frequency transposition and frequency compression to preserve the harmonic content of music stimuli. Listeners were asked to make judgments regarding detail and sound quality in music stimuli. Stimuli were presented under different signal processing conditions: original, low-pass filtered, HFL, and nonlinear frequency compressed. Results showed that participants reported perceiving the most detail in the HFL condition. In addition, there was no difference in sound quality across conditions. PMID:26834122

A Simple Ultrasonic Experiment Using a Phase Shift Detection Technique.

ERIC Educational Resources Information Center

Yunus, W. Mahmood Mat; Ahmad, Maulana

1996-01-01

Describes a simple ultrasonic experiment that can be used to measure the purity of liquid samples by detecting variations in the velocity of sound. Uses a phase shift detection technique that incorporates the use of logic gates and a piezoelectric transducer. (JRH)

Detecting planets in Kepler lightcurves using methods developed for CoRoT.

NASA Astrophysics Data System (ADS)

Grziwa, S.; Korth, J.; Pätzold, M.

2011-10-01

Launched in March 2009, Kepler is the second space telescope dedicated to the search for extrasolar planets. NASA released 150.000 lightcurves to the public in 2010 and announced that Kepler has found 1.235 candidates. The Rhenish Institute for Environmental Research (RIU-PF) is one of the detection groups from the CoRoT space mission. RIU-PF developed the software package EXOTRANS for the detection of transits in stellar lightcurves. EXOTRANS is designed for the fast automated processing of huge amounts of data and was easily adapted to the analysis of Kepler lightcurves. The use of different techniques and philosophies helps to find more candidates and to rule out others. We present the analysis of the Kepler lightcurves with EXOTRANS. Results of our filter (trend, harmonic) and detection (dcBLS) techniques are compared with the techniques used by Kepler (PDC, TPS). The different approaches to rule out false positives are discussed and additional candidates found by EXOTRANS are presented.

Underwater Turbulence Detection Using Gated Wavefront Sensing Technique

PubMed Central

Bi, Ying; Xu, Xiping; Chow, Eddy Mun Tik

2018-01-01

Laser sensing has been applied in various underwater applications, ranging from underwater detection to laser underwater communications. However, there are several great challenges when profiling underwater turbulence effects. Underwater detection is greatly affected by the turbulence effect, where the acquired image suffers excessive noise, blurring, and deformation. In this paper, we propose a novel underwater turbulence detection method based on a gated wavefront sensing technique. First, we elaborate on the operating principle of gated wavefront sensing and wavefront reconstruction. We then setup an experimental system in order to validate the feasibility of our proposed method. The effect of underwater turbulence on detection is examined at different distances, and under different turbulence levels. The experimental results obtained from our gated wavefront sensing system indicate that underwater turbulence can be detected and analyzed. The proposed gated wavefront sensing system has the advantage of a simple structure and high detection efficiency for underwater environments. PMID:29518889

MODEL HARMONIZATION POTENTIAL AND BENEFITS

EPA Science Inventory

The IPCS Harmonization Project, which is currently ongoing under the auspices of the WHO, in the context of chemical risk assessment or exposure modeling, does not imply global standardization. Instead, harmonization is thought of as an effort to strive for consistency among appr...

Young children's harmonic perception.

PubMed

Costa-Giomi, Eugenia

2003-11-01

Harmony and tonality are two of the most difficult elements for young children to perceive and manipulate and are seldom taught in the schools until the end of early childhood. Children's gradual harmonic and tonal development has been attributed to their cumulative exposure to Western tonal music and their increasing experiential knowledge of its rules and principles. Two questions that are relevant to this problem are: (1) Can focused and systematic teaching accelerate the learning of the harmonic/tonal principles that seem to occur in an implicit way throughout childhood? (2) Are there cognitive constraints that make it difficult for young children to perceive and/or manipulate certain harmonic and tonal principles? A series of studies specifically addressed the first question and suggested some possible answers to the second one. Results showed that harmonic instruction has limited effects on children's perception of harmony and indicated that the drastic improvement in the perception of implied harmony noted approximately at age 9 is due to development rather than instruction. I propose that young children's difficulty in perceiving implied harmony stems from their attention behaviors. Older children have less memory constraints and more strategies to direct their attention to the relevant cues of the stimulus. Younger children focus their attention on the melody, if present in the stimulus, and specifically on its concrete elements such as rhythm, pitch, and contour rather than its abstract elements such as harmony and key. The inference of the abstract harmonic organization of a melody required in the perception of implied harmony is thus an elusive task for the young child.

A Multi-object Exoplanet Detecting Technique

NASA Astrophysics Data System (ADS)

Zhang, K.

2011-05-01

Exoplanet exploration is not only a meaningful astronomical action, but also has a close relation with the extra-terrestrial life. High resolution echelle spectrograph is the key instrument for measuring stellar radial velocity (RV). But with higher precision, better environmental stability and higher cost are required. An improved technique of RV means invented by David J. Erskine in 1997, External Dispersed Interferometry (EDI), can increase the RV measuring precision by combining the moderate resolution spectrograph with a fixed-delay Michelson interferometer. LAMOST with large aperture and large field of view is equipped with 16 multi-object low resolution fiber spectrographs. And these spectrographs are capable to work in medium resolution mode (R=5{K}˜10{K}). LAMOST will be one of the most powerful exoplanet detecting systems over the world by introducing EDI technique. The EDI technique is a new technique for developing astronomical instrumentation in China. The operating theory of EDI was generally verified by a feasibility experiment done in 2009. And then a multi-object exoplanet survey system based on LAMOST spectrograph was proposed. According to this project, three important tasks have been done as follows: Firstly, a simulation of EDI operating theory contains the stellar spectrum model, interferometer transmission model, spectrograph mediation model and RV solution model. In order to meet the practical situation, two detecting modes, temporal and spatial phase-stepping methods, are separately simulated. The interference spectrum is analyzed with Fourier transform algorithm and a higher resolution conventional spectrum is resolved. Secondly, an EDI prototype is composed of a multi-object interferometer prototype and the LAMOST spectrograph. Some ideas are used in the design to reduce the effect of central obscuration, for example, modular structure and external/internal adjusting frames. Another feasibility experiment was done at Xinglong Station in

Harmonic field in knotted space

NASA Astrophysics Data System (ADS)

Duan, Xiuqing; Yao, Zhenwei

2018-04-01

Knotted fields enrich a variety of physical phenomena, ranging from fluid flows, electromagnetic fields, to textures of ordered media. Maxwell's electrostatic equations, whose vacuum solution is mathematically known as a harmonic field, provide an ideal setting to explore the role of domain topology in determining physical fields in confined space. In this work, we show the uniqueness of a harmonic field in knotted tubes, and reduce the construction of a harmonic field to a Neumann boundary value problem. By analyzing the harmonic field in typical knotted tubes, we identify the torsion driven transition from bipolar to vortex patterns. We also analogously extend our discussion to the organization of liquid crystal textures in knotted tubes. These results further our understanding about the general role of topology in shaping a physical field in confined space, and may find applications in the control of physical fields by manipulation of surface topology.

Bounce-harmonic Landau Damping of Plasma Waves

NASA Astrophysics Data System (ADS)

Anderegg, Francois

2015-11-01

We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v harmonics damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

High-harmonic generation in amorphous solids

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, Yong Sing; Yin, Yanchun; Wu, Yi

High-harmonic generation in isolated atoms and molecules has been widely utilized in extreme ultraviolet photonics and attosecond pulse metrology. Recently, high-harmonic generation has been observed in solids, which could lead to important applications such as all-optical methods to image valance charge density and reconstruct electronic band structures, as well as compact extreme ultraviolet light sources. So far these studies are confined to crystalline solids; therefore, decoupling the respective roles of long-range periodicity and high density has been challenging. Here we report the observation of high-harmonic generation from amorphous fused silica. We also decouple the role of long-range periodicity by comparingmore » harmonics generated from fused silica and crystalline quartz, which contain the same atomic constituents but differ in long-range periodicity. These results advance current understanding of the strong-field processes leading to high-harmonic generation in solids with implications for the development of robust and compact extreme ultraviolet light sources.« less

Understanding fifth-harmonic generation in CLBO

NASA Astrophysics Data System (ADS)

Patankar, S.; Yang, S. T.; Moody, J. D.; Bayramian, A. J.; Swadling, G. F.; Barker, D.; Datte, P.; Mennerat, G.; Norton, M.; Carr, C. W.; Begishev, I. A.; Bromage, J.; Ross, J. S.

2018-02-01

We report on results of fifth harmonic generation in Cesium Lithium Borate (CLBO) using a three-crystal cascaded frequency conversion scheme designed to study the energy balance of the final sum frequency generation stage. The experimental setup independently combines the first and fourth harmonic of a Nd:Glass laser in a 5mm thick CLBO crystal. Energy balance between the incoming and output energy is close to unity when the CLBO is out of phase matching and approximately 80% when the crystal is in phase matching. A detailed analysis of the residual fundamental and fourth harmonic energy indicates 5th harmonic light is being generated but only 26% is unaccounted for. We attribute the missing light to linear transmission loss in the CLBO oven. The ratio of the output to input energy is unity when the missing 5th harmonic is incorporated into the calculations. Two-dimensional plane wave mixing simulations show agreement with the results at lower intensities.

High-harmonic generation in amorphous solids

DOE PAGES

You, Yong Sing; Yin, Yanchun; Wu, Yi; ...

2017-09-28

High-harmonic generation in isolated atoms and molecules has been widely utilized in extreme ultraviolet photonics and attosecond pulse metrology. Recently, high-harmonic generation has been observed in solids, which could lead to important applications such as all-optical methods to image valance charge density and reconstruct electronic band structures, as well as compact extreme ultraviolet light sources. So far these studies are confined to crystalline solids; therefore, decoupling the respective roles of long-range periodicity and high density has been challenging. Here we report the observation of high-harmonic generation from amorphous fused silica. We also decouple the role of long-range periodicity by comparingmore » harmonics generated from fused silica and crystalline quartz, which contain the same atomic constituents but differ in long-range periodicity. These results advance current understanding of the strong-field processes leading to high-harmonic generation in solids with implications for the development of robust and compact extreme ultraviolet light sources.« less

Advanced Doppler radar physiological sensing technique for drone detection

NASA Astrophysics Data System (ADS)

Yoon, Ji Hwan; Xu, Hao; Garcia Carrillo, Luis R.

2017-05-01

A 24 GHz medium-range human detecting sensor, using the Doppler Radar Physiological Sensing (DRPS) technique, which can also detect unmanned aerial vehicles (UAVs or drones), is currently under development for potential rescue and anti-drone applications. DRPS systems are specifically designed to remotely monitor small movements of non-metallic human tissues such as cardiopulmonary activity and respiration. Once optimized, the unique capabilities of DRPS could be used to detect UAVs. Initial measurements have shown that DRPS technology is able to detect moving and stationary humans, as well as largely non-metallic multi-rotor drone helicopters. Further data processing will incorporate pattern recognition to detect multiple signatures (motor vibration and hovering patterns) of UAVs.

Effect of skew angle on second harmonic guided wave measurement in composite plates

NASA Astrophysics Data System (ADS)

Cho, Hwanjeong; Choi, Sungho; Lissenden, Cliff J.

2017-02-01

Waves propagating in anisotropic media are subject to skewing effects due to the media having directional wave speed dependence, which is characterized by slowness curves. Likewise, the generation of second harmonics is sensitive to micro-scale damage that is generally not detectable from linear features of ultrasonic waves. Here, the effect of skew angle on second harmonic guided wave measurement in a transversely isotropic lamina and a quasi-isotropic laminate are numerically studied. The strain energy density function for a nonlinear transversely isotropic material is formulated in terms of the Green-Lagrange strain invariants. The guided wave mode pairs for cumulative second harmonic generation in the plate are selected in accordance with the internal resonance criteria - i.e., phase matching and non-zero power flux. Moreover, the skew angle dispersion curves for the mode pairs are obtained from the semi-analytical finite element method using the derivative of the slowness curve. The skew angles of the primary and secondary wave modes are calculated and wave propagation simulations are carried out using COMSOL. Numerical simulations revealed that the effect of skew angle mismatch can be significant for second harmonic generation in anisotropic media. The importance of skew angle matching on cumulative second harmonic generation is emphasized and the accompanying issue of the selection of internally resonant mode pairs for both a unidirectional transversely isotropic lamina and a quasi-isotropic laminate is demonstrated.

Coherence-domain imaging with harmonic holography

NASA Astrophysics Data System (ADS)

Pu, Ye; Psaltis, Demetri

2017-08-01

Observing the fast dynamics of specific molecules or targets in three-dimensional (3D) space and time inside a crowded and complex environment, such as living cells or tissues, remain one of the grand open challenges in modern science. Harmonic holography tackle this challenge by combining the 3D imaging capability of holography with the ultrafast, coherent optical contrast offered by second-harmonic radiating imaging probes (SHRIMPs). Similar to fluorescence, the second-harmonic signal emitted from SHRIMPs provides a color contrast against the uninterested background scattering, which can be efficiently suppressed by an optical filter. We review the latest developments in SHRIMPs and harmonic holography and discuss their further applications in fluidics and biofluidics.

A passive infrared ice detection technique for helicopter applications

NASA Technical Reports Server (NTRS)

Dershowitz, Adam L.; Hansman, R. John, Jr.

1991-01-01

A technique has been developed, and successfully tested, to detect icing remotely on helicopter rotor blades. Using passive infrared (IR) thermometry it is possible to detect the warming caused by latent heat released as supercooled water freezes. During icing, the ice accretion region on the leading edge of the blade is found to be warmer than the uniced trailing edge resulting in a chordwise temperature profile characteristic of icing. Preliminary tests, using an IR Thermal video system, were conducted on a static model in the NASA Icing Research Tunnel (IRT) for a variety of wet (glaze) and dry (rime) ice conditions. A prototype detector system was built consisting of a single point IR pyrometer, and experiments were run on a small scale rotor model. Using this prototype detector, the characteristic chordwise temperature profiles were again observed for a range of icing conditions. Several signal processing methods were investigated, to allow automatic recognition of the icing signature. Additionally, several implementation issues were considered. Based on both the static and subscale rotor tests, where ice was successfully detected, the passive IR technique appears to be promising for rotor ice detection.

Detection of cyclic-fold bifurcation in electrostatic MEMS transducers by motion-induced current

NASA Astrophysics Data System (ADS)

Park, Sangtak; Khater, Mahmoud; Effa, David; Abdel-Rahman, Eihab; Yavuz, Mustafa

2017-08-01

This paper presents a new detection method of cyclic-fold bifurcations in electrostatic MEMS transducers based on a variant of the harmonic detection of resonance method. The electrostatic transducer is driven by an unbiased harmonic signal at half its natural frequency, ω a   =  1/2 ω o . The response of the transducer consists of static displacement and a series of harmonics at 2 ω a , 4 ω a , and so on. Its motion-induced current is shifted by the excitation frequency, ω a , to appear at 3 ω a , 5 ω a , and higher odd harmonics, providing higher sensitivity to the measurement of harmonic motions. With this method, we successfully detected the variation in the location of the cyclic-fold bifurcation of an encapsulated electrostatic MEMS transducer. We also detected a regime of tapping mode motions subsequent to the bifurcation.

Reactive impinging-flow technique for polymer-electrolyte-fuel-cell electrode-defect detection

DOE PAGES

Zenyuk, Iryna V.; Englund, Nicholas; Bender, Guido; ...

2016-09-29

Reactive impinging flow (RIF) is a novel quality-control method for defect detection (i.e., reduction in Pt catalyst loading) in gas-diffusion electrodes (GDEs) on weblines. The technique uses infrared thermography to detect temperature of a nonflammable (<4% H 2) reactive mixture of H 2/O 2 in N 2 impinging and reacting on a Pt catalytic surface. In this article, different GDE size defects (with catalyst-loading reductions of 25, 50, and 100%) are detected at various webline speeds (3.048 and 9.144 m min -1) and gas flowrates (32.5 or 50 standard L min -1). Furthermore, a model is developed and validated formore » the technique, and it is subsequently used to optimize operating conditions and explore the applicability of the technique to a range of defects. The model suggests that increased detection can be achieved by recting more of the impinging H 2, which can be accomplished by placing blocking substrates on the top, bottom, or both of the GDE; placing a substrate on both results in a factor of four increase in the temperature differential, which is needed for smaller defect detection. Lastly, overall, the RIF technique is shown to be a promising route for in-line, high-speed, large-area detection of GDE defects on moving weblines.« less

Early Oscillation Detection Technique for Hybrid DC/DC Converters

NASA Technical Reports Server (NTRS)

Wang, Bright L.

2011-01-01

Oscillation or instability is a situation that must be avoided for reliable hybrid DC/DC converters. A real-time electronics measurement technique was developed to detect catastrophic oscillations at early stages for hybrid DC/DC converters. It is capable of identifying low-level oscillation and determining the degree of the oscillation at a unique frequency for every individual model of the converters without disturbing their normal operations. This technique is specially developed for space-used hybrid DC/DC converters, but it is also suitable for most of commercial and military switching-mode power supplies. This is a weak-electronic-signal detection technique to detect hybrid DC/DC converter oscillation presented as a specific noise signal at power input pins. It is based on principles of feedback control loop oscillation and RF signal modulations, and is realized by using signal power spectral analysis. On the power spectrum, a channel power amplitude at characteristic frequency (CPcf) and a channel power amplitude at switching frequency (CPsw) are chosen as oscillation level indicators. If the converter is stable, the CPcf is a very small pulse and the CPsw is a larger, clear, single pulse. At early stage of oscillation, the CPcf increases to a certain level and the CPsw shows a small pair of sideband pulses around it. If the converter oscillates, the CPcf reaches to a higher level and the CPsw shows more high-level sideband pulses. A comprehensive stability index (CSI) is adopted as a quantitative measure to accurately assign a degree of stability to a specific DC/DC converter. The CSI is a ratio of normal and abnormal power spectral density, and can be calculated using specified and measured CPcf and CPsw data. The novel and unique feature of this technique is the use of power channel amplitudes at characteristic frequency and switching frequency to evaluate stability and identify oscillations at an early stage without interfering with a DC/DC converter s

Attentional Capacity Limits Gap Detection during Concurrent Sound Segregation.

PubMed

Leung, Ada W S; Jolicoeur, Pierre; Alain, Claude

2015-11-01

Detecting a brief silent interval (i.e., a gap) is more difficult when listeners perceive two concurrent sounds rather than one in a sound containing a mistuned harmonic in otherwise in-tune harmonics. This impairment in gap detection may reflect the interaction of low-level encoding or the division of attention between two sound objects, both of which could interfere with signal detection. To distinguish between these two alternatives, we compared ERPs during active and passive listening with complex harmonic tones that could include a gap, a mistuned harmonic, both features, or neither. During active listening, participants indicated whether they heard a gap irrespective of mistuning. During passive listening, participants watched a subtitled muted movie of their choice while the same sounds were presented. Gap detection was impaired when the complex sounds included a mistuned harmonic that popped out as a separate object. The ERP analysis revealed an early gap-related activity that was little affected by mistuning during the active or passive listening condition. However, during active listening, there was a marked decrease in the late positive wave that was thought to index attention and response-related processes. These results suggest that the limitation in detecting the gap is related to attentional processing, possibly divided attention induced by the concurrent sound objects, rather than deficits in preattentional sensory encoding.

Wear Detection of Drill Bit by Image-based Technique

NASA Astrophysics Data System (ADS)

Sukeri, Maziyah; Zulhilmi Paiz Ismadi, Mohd; Rahim Othman, Abdul; Kamaruddin, Shahrul

2018-03-01

Image processing for computer vision function plays an essential aspect in the manufacturing industries for the tool condition monitoring. This study proposes a dependable direct measurement method to measure the tool wear using image-based analysis. Segmentation and thresholding technique were used as the means to filter and convert the colour image to binary datasets. Then, the edge detection method was applied to characterize the edge of the drill bit. By using cross-correlation method, the edges of original and worn drill bits were correlated to each other. Cross-correlation graphs were able to detect the difference of the worn edge despite small difference between the graphs. Future development will focus on quantifying the worn profile as well as enhancing the sensitivity of the technique.

Dual aperture dipole magnet with second harmonic component

DOEpatents

Praeg, Walter F.

1985-01-01

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Dual aperture dipole magnet with second harmonic component

DOEpatents

Praeg, W.F.

1983-08-31

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Clustering Categorical Data Using Community Detection Techniques

PubMed Central

2017-01-01

With the advent of the k-modes algorithm, the toolbox for clustering categorical data has an efficient tool that scales linearly in the number of data items. However, random initialization of cluster centers in k-modes makes it hard to reach a good clustering without resorting to many trials. Recently proposed methods for better initialization are deterministic and reduce the clustering cost considerably. A variety of initialization methods differ in how the heuristics chooses the set of initial centers. In this paper, we address the clustering problem for categorical data from the perspective of community detection. Instead of initializing k modes and running several iterations, our scheme, CD-Clustering, builds an unweighted graph and detects highly cohesive groups of nodes using a fast community detection technique. The top-k detected communities by size will define the k modes. Evaluation on ten real categorical datasets shows that our method outperforms the existing initialization methods for k-modes in terms of accuracy, precision, and recall in most of the cases. PMID:29430249

A new method for QRS detection in ECG signals using QRS-preserving filtering techniques.

PubMed

Sharma, Tanushree; Sharma, Kamalesh K

2018-03-28

Detection of QRS complexes in ECG signals is required for various purposes such as determination of heart rate, feature extraction and classification. The problem of automatic QRS detection in ECG signals is complicated by the presence of noise spectrally overlapping with the QRS frequency range. As a solution to this problem, we propose the use of least-squares-optimisation-based smoothing techniques that suppress the noise peaks in the ECG while preserving the QRS complexes. We also propose a novel nonlinear transformation technique that is applied after the smoothing operations, which equalises the QRS amplitudes without boosting the supressed noise peaks. After these preprocessing operations, the R-peaks can finally be detected with high accuracy. The proposed technique has a low computational load and, therefore, it can be used for real-time QRS detection in a wearable device such as a Holter monitor or for fast offline QRS detection. The offline and real-time versions of the proposed technique have been evaluated on the standard MIT-BIH database. The offline implementation is found to perform better than state-of-the-art techniques based on wavelet transforms, empirical mode decomposition, etc. and the real-time implementation also shows improved performance over existing real-time QRS detection techniques.

Wireless tamper detection sensor and sensing system

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2011-01-01

A wireless tamper detection sensor is defined by a perforated electrical conductor. The conductor is shaped to form a geometric pattern between first and second ends thereof such that the conductor defines an open-circuit that can store and transfer electrical and magnetic energy. The conductor resonates in the presence of a time-varying magnetic field to generate a harmonic response. The harmonic response changes when the conductor experiences a change in its geometric pattern due to severing of the conductor along at least a portion of the perforations. A magnetic field response recorder is used to wirelessly transmit the time-varying magnetic field and wirelessly detecting the conductor's harmonic response.

Modernization of Physical Appearance and Solution Color Tests Using Quantitative Tristimulus Colorimetry: Advantages, Harmonization, and Validation Strategies.

PubMed

Pack, Brian W; Montgomery, Laura L; Hetrick, Evan M

2015-10-01

Color measurements, including physical appearance, are important yet often misunderstood and underappreciated aspects of a control strategy for drug substances and drug products. From a patient safety perspective, color can be an important control point for detecting contamination, impurities, and degradation products, with human visual acuity often more sensitive for colored impurities than instrumental techniques such as HPLC. Physical appearance tests and solution color tests can also serve an important role in ensuring that appropriate steps are taken such that clinical trials do not become unblinded when the active material is compared with another product or a placebo. Despite the importance of color tests, compendial visual tests are not harmonized across the major pharmacopoeias, which results in ambiguous specifications of little value, difficult communication of true sample color, and significant extra work required for global registration. Some pharmacopoeias have not yet recognized or adopted technical advances in the instrumental measurement of color and appearance, whereas others begin to acknowledge the advantage of instrumental colorimetry, yet leave implementation of the technology ambiguous. This commentary will highlight the above-mentioned inconsistencies, provide an avenue toward harmonization and modernization, and outline a scientifically sound approach for implementing quantitative technologies for improved measurement, communication, and control of color and appearance for both solutions and solids. Importantly, this manuscript, for the first time, outlines a color method validation approach that is consistent with the International Conference on Harmonization's guidance on the topic of method validation. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Fault detection techniques for complex cable shield topologies

NASA Astrophysics Data System (ADS)

Coonrod, Kurt H.; Davis, Stuart L.; McLemore, Donald P.

1994-09-01

This document presents the results of a basic principles study which investigated technical approaches for developing fault detection techniques for use on cables with complex shielding topologies. The study was limited to those approaches which could realistically be implemented on a fielded cable, i.e., approaches which would require partial disassembly of a cable were not pursued. The general approach used was to start with present transfer impedance measurement techniques and modify their use to achieve the best possible measurement range. An alternative test approach, similar to a sniffer type test, was also investigated.

Harmonic surface acoustic waves on gallium nitride thin films.

PubMed

Justice, Joshua; Lee, Kyoungnae; Korakakis, D

2012-08-01

SAW devices operating at the fundamental frequency and the 5th, 7th, 9th, and 11th harmonics have been designed, fabricated, and measured. Devices were fabricated on GaN thin films on sapphire substrates, which were grown via metal organic vapor phase epitaxy (MOVPE). Operating frequencies of 230, 962, 1338, 1720, and 2100 MHz were achieved with devices that had a fundamental wavelength, lambda0 = 20 μm. Gigahertz operation is realized with relatively large interdigital transducers that do not require complicated submicrometer fabrication techniques. SAW devices fabricated on the GaN/sapphire bilayer have an anisotropic propagation when the wavelength is longer than the GaN film thickness. It is shown that for GaN thin films, where kh(GaN) > 10 (k = 2pi/lambda and h(GaN) = GaN film thickness), effects of the substrate on the SAW propagation are eliminated. Bulk mode suppression at harmonic operation is also demonstrated.

Perturbing laser field dependent high harmonic phase modulations

NASA Astrophysics Data System (ADS)

Li, Zhengyan; Kong, Fanqi; Brown, Graham; Hammond, TJ; Ko, Dong-Hyuk; Zhang, Chunmei; Corkum, P. B.

2018-06-01

A perturbing laser pulse modulates and controls the phase of the high harmonic radiation driven by an intense fundamental pulse. Thus, a structured wave front can impress a specific spatial phase onto the generated high harmonic wave front. This modulation procedure leads to all-optical spatial light modulators for VUV or XUV radiation created by high harmonic generation. Here, through theoretical analysis and experiment, we study the correlation between the high harmonic phase modulations and the perturbing laser field amplitude and phase, providing guidelines for practical high harmonic spatial light modulators. In addition, we show that the petahertz optical oscilloscope for measuring electric fields of a perturbing beam is most robust using low order harmonics, far from the cut-off.

Speed harmonization

DOT National Transportation Integrated Search

2015-01-01

Speed harmonization is a method to reduce congestion and improve traffic performance. This method is applied at points where lanes merge and form bottlenecks, the greatest cause of congestion nationwide. The strategy involves gradually lowering speed...

High order harmonic generation in rare gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budil, Kimberly Susan

1994-05-01

The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~10 13-10 14 W/cm 2) is focused into a dense (~10 17 particles/cm 3) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as wellmore » as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.« less

Harmonic decomposition of magneto-optical signal from superparamagnetic Fe3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Syed, Maarij; Patterson, Cody; Takemura, Yasushi

Superparamagnetic nanoparticles (SPNPs) are expected to play an increasingly important role in bio-imaging and therapy. These applications rely on understanding SPNPs magnetic properties which have been successfully characterized by AC Faraday rotation (FR). AC FR is used here to build on results presented earlier by measuring solutions of surfactant-coated magnetite nanoparticles. The setup employs a He-Ne laser, polarizing components, a sinusoidal B-field, and a lock-in detection scheme to measure the SPNPs FR. Such a setup provides a novel, economical way of determining important magnetic properties of SPNPs. The main intensity signal (1f) along with higher harmonics are collected and analyzed to calculate quantities such as the Verdet constant and the magnetic moment. We hope further analysis can also reveal details of size distribution and relaxation times of SPNPs. We will present results from samples with various concentrations as well as a particular concentration subjected to a range of B-field frequencies (between 800 Hz and 14 kHz). Findings are compared to results from more traditional techniques like magnetic susceptibility measurements, magnetic force microscopy, etc. We will also address the comparative advantages of this technique and its limitations.

Monitoring the interfacial electric field in pure and doped SrTiO3 surfaces by means of phase-resolved optical second harmonic generation

NASA Astrophysics Data System (ADS)

Rubano, Andrea; Mou, Sen; Paparo, Domenico

2018-05-01

Oxides and new functional materials such as oxide-based hetero-structures are very good candidates to achieve the goal of the next generation electronics. One of the main features that rules the electronic behavior of these compounds is the interfacial electric field which confines the charge carriers to a quasi-two-dimensional space region. The sign of the confined charge clearly depends on the electric field direction, which is however a very elusive quantity, as most techniques can only detect its absolute value. Even more valuable would be to access the sign of the interfacial electric field directly during the sample growth, being thus able to optimize the growth conditions directly looking at the feature of interest. For this aim, solid and reliable sensors are needed for monitoring the thin films while grown. Recently optical second harmonic generation has been proposed by us as a tool for non-invasive, non-destructive, real-time, in-situ imaging of oxide epitaxial film growth. The spatial resolution of this technique has been exploited to obtain real-time images of the sample under investigation. Here we propose to exploit another very important physical property of the second harmonic wave: its phase, which is directly coupled with the electric field direction, as shown by our measurements.

Second Harmonic Correlation Spectroscopy: Theory and Principles for Determining Surface Binding Kinetics.

PubMed

Sly, Krystal L; Conboy, John C

2017-06-01

A novel application of second harmonic correlation spectroscopy (SHCS) for the direct determination of molecular adsorption and desorption kinetics to a surface is discussed in detail. The surface-specific nature of second harmonic generation (SHG) provides an efficient means to determine the kinetic rates of adsorption and desorption of molecular species to an interface without interference from bulk diffusion, which is a significant limitation of fluorescence correlation spectroscopy (FCS). The underlying principles of SHCS for the determination of surface binding kinetics are presented, including the role of optical coherence and optical heterodyne mixing. These properties of SHCS are extremely advantageous and lead to an increase in the signal-to-noise (S/N) of the correlation data, increasing the sensitivity of the technique. The influence of experimental parameters, including the uniformity of the TEM00 laser beam, the overall photon flux, and collection time are also discussed, and are shown to significantly affect the S/N of the correlation data. Second harmonic correlation spectroscopy is a powerful, surface-specific, and label-free alternative to other correlation spectroscopic methods for examining surface binding kinetics.

Utility of Higher Harmonics in Electrospray Ionization Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometry.

PubMed

Dziekonski, Eric T; Johnson, Joshua T; McLuckey, Scott A

2017-04-18

Mass resolution (M/ΔM fwhm) is observed to linearly increase with harmonic order in a Fourier transform electrostatic linear ion trap (ELIT) mass spectrometer. This behavior was predicted by Grosshans and Marshall for frequency-multiple detection in a Fourier transform ion cyclotron resonance mass spectrometer only for situations when the prominent mechanism for signal decay is ion ejection from the trap. As the analyzer pressure in our ELIT chamber is relatively high, such that collisional scattering and collision-induced dissociation are expected to underlie much of the ion loss, we sought to explore the relationship between harmonic order and mass resolution. Mass resolutions of 36 900 (fundamental), 75 850 (2nd harmonic), and 108 200 (3rd harmonic) were obtained for GdO + (avg. m/z 173.919) with a transient length of 300 ms. To demonstrate that the mass resolution was truly increasing with harmonic order, the unresolved isotopes at the fundamental distribution of cytochrome c +8 (m/z ∼ 1549) were nearly baseline, resolved at the third harmonic (mass resolution ≈ 23 000) with a transient length of only 200 ms. This experiment demonstrates that, when the ion density is sufficiently low, ions with frequency differences of less than 4 Hz remain uncoalesced. Higher harmonics can be used to increase the effective mass resolution for a fixed transient length and thereby may enable the resolution of closely spaced masses, determination of a protein ion's charge state, and study of the onset of peak coalescence when the resolution at the fundamental frequency is insufficient.

A Wireless Embedded Sensor based on Magnetic Higher-order Harmonic Fields: Application to Liquid Pressure Monitoring

PubMed Central

Tan, Ee Lim; Pereles, Brandon D.

2010-01-01

A wireless sensor based on the magnetoelastic, magnetically soft ferromagnetic alloy was constructed for remote measurement of pressure in flowing fluids. The pressure sensor was a rectangular strip of ferromagnetic alloy Fe40Ni38Mo4B18 adhered on a solid polycarbonate substrate and protected by a thin polycarbonate film. Upon excitation of a time-varying magnetic field through an excitation coil, the magnetically soft sensor magnetized and produced higher-order harmonic fields, which were detected through a detection coil. Under varying pressures, the sensor's magnetoelastic property caused a change in its magnetization, altering the amplitudes of the higher-order harmonic fields. A theoretical model was developed to describe the effect of pressure on the sensor's higher order harmonic fields. Experimental observations showed the 2nd order harmonic field generated by the pressure sensor was correlated to the surrounding fluid pressure, consistent with the theoretical results. Furthermore, it was demonstrated that the sensor exhibited good repeatability and stability with minimal drift. Sensors with smaller dimensions were shown to have greater sensitivity but lower pressure range as compared to their larger counterparts. Since the sensor signal was also dependent on the location of the sensor with respect to the excitation/detection coil, a calibration algorithm was developed to eliminate signal variations due to the changing sensor location. Because of its wireless and passive nature, this sensor is useful for continuous and long-term monitoring of pressure at inaccessible areas. For example, sensors with these capabilities are suitable to be used in biomedical applications where permanent implantation and long-term monitoring are needed. PMID:20514363

Linking high harmonics from gases and solids.

PubMed

Vampa, G; Hammond, T J; Thiré, N; Schmidt, B E; Légaré, F; McDonald, C R; Brabec, T; Corkum, P B

2015-06-25

When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed.

Harmonic generation in magnetized quantum plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Punit; Singh, Abhisek Kumar; Singh, Shiv

2016-05-06

A study of second harmonic generation by propagation of a linearly polarized electromagnetic wave through homogeneous high density quantum plasma in the presence of transverse magnetic field. The nonlinear current density and dispersion relations for the fundamental and second harmonic frequencies have been obtained using the recently developed quantum hydrodynamic (QHD) model. The effect of quantum Bohm potential, Fermi pressure and the electron spin have been taken into account. The second harmonic is found to be less dispersed than the first.

Derivation of exact master equation with stochastic description: dissipative harmonic oscillator.

PubMed

Li, Haifeng; Shao, Jiushu; Wang, Shikuan

2011-11-01

A systematic procedure for deriving the master equation of a dissipative system is reported in the framework of stochastic description. For the Caldeira-Leggett model of the harmonic-oscillator bath, a detailed and elementary derivation of the bath-induced stochastic field is presented. The dynamics of the system is thereby fully described by a stochastic differential equation, and the desired master equation would be acquired with statistical averaging. It is shown that the existence of a closed-form master equation depends on the specificity of the system as well as the feature of the dissipation characterized by the spectral density function. For a dissipative harmonic oscillator it is observed that the correlation between the stochastic field due to the bath and the system can be decoupled, and the master equation naturally results. Such an equation possesses the Lindblad form in which time-dependent coefficients are determined by a set of integral equations. It is proved that the obtained master equation is equivalent to the well-known Hu-Paz-Zhang equation based on the path-integral technique. The procedure is also used to obtain the master equation of a dissipative harmonic oscillator in time-dependent fields.

Hyperspherical Sparse Approximation Techniques for High-Dimensional Discontinuity Detection

DOE PAGES

Zhang, Guannan; Webster, Clayton G.; Gunzburger, Max; ...

2016-08-04

This work proposes a hyperspherical sparse approximation framework for detecting jump discontinuities in functions in high-dimensional spaces. The need for a novel approach results from the theoretical and computational inefficiencies of well-known approaches, such as adaptive sparse grids, for discontinuity detection. Our approach constructs the hyperspherical coordinate representation of the discontinuity surface of a function. Then sparse approximations of the transformed function are built in the hyperspherical coordinate system, with values at each point estimated by solving a one-dimensional discontinuity detection problem. Due to the smoothness of the hypersurface, the new technique can identify jump discontinuities with significantly reduced computationalmore » cost, compared to existing methods. Several approaches are used to approximate the transformed discontinuity surface in the hyperspherical system, including adaptive sparse grid and radial basis function interpolation, discrete least squares projection, and compressed sensing approximation. Moreover, hierarchical acceleration techniques are also incorporated to further reduce the overall complexity. In conclusion, rigorous complexity analyses of the new methods are provided, as are several numerical examples that illustrate the effectiveness of our approach.« less

Delay-Encoded Harmonic Imaging (DE-HI) in Multiplane-Wave Compounding.

PubMed

Gong, Ping; Song, Pengfei; Chen, Shigao

2017-04-01

The development of ultrafast ultrasound imaging brings great opportunities to improve imaging technologies such as shear wave elastography and ultrafast Doppler imaging. In ultrafast imaging, several tilted plane or diverging wave images are coherently combined to form a compounded image, leading to trade-offs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Multiplane wave (MW) imaging is proposed to solve this trade-off by encoding multiple plane waves with Hadamard matrix during one transmission event (i.e. pulse-echo event), to improve image SNR without sacrificing the resolution or frame rate. However, it suffers from stronger reverberation artifacts in B-mode images compared to standard plane wave compounding due to longer transmitted pulses. If harmonic imaging can be combined with MW imaging, the reverberation artifacts and other clutter noises such as sidelobes and multipath scattering clutters should be suppressed. The challenge, however, is that the Hadamard codes used in MW imaging cannot encode the 2 nd harmonic component by inversing the pulse polarity. In this paper, we propose a delay-encoded harmonic imaging (DE-HI) technique to encode the 2 nd harmonic with a one quarter period delay calculated at the transmit center frequency, rather than reversing the pulse polarity during multiplane wave emissions. Received DE-HI signals can then be decoded in the frequency domain to recover the signals as in single plane wave emissions, but mainly with improved SNR at the 2 nd harmonic component instead of the fundamental component. DE-HI was tested experimentally with a point target, a B-mode imaging phantom, and in-vivo human liver imaging. Improvements in image contrast-to-noise ratio (CNR), spatial resolution, and lesion-signal-to-noise ratio ( l SNR) have been achieved compared to standard plane wave compounding, MW imaging, and standard harmonic imaging (maximal improvement of 116% on CNR and 115% on l SNR as compared

Oxygen detection using the laser diode absorption technique

NASA Technical Reports Server (NTRS)

Disimile, P. J.; Fox, C. W.

1991-01-01

Accurate measurement of the concentration and flow rate of gaseous oxygen is becoming of greater importance. The detection technique presented is based on the principal of light absorption by the Oxygen A-Band. Oxygen molecules have characteristics which attenuate radiation in the 759-770 nm wavelength range. With an ability to measure changes in the relative light transmission to less than 0.01 percent, a sensitive optical gas detection system was configured. This system is smaller in size and light in weight, has low energy requirements and has a rapid response time. In this research program, the application of temperature tuning laser diodes and their ability to be wavelength shifted to a selected absorption spectral peak has allowed concentrations as low as 1300 ppm to be detected.

Updating Landsat-derived land-cover maps using change detection and masking techniques

NASA Technical Reports Server (NTRS)

Likens, W.; Maw, K.

1982-01-01

The California Integrated Remote Sensing System's San Bernardino County Project was devised to study the utilization of a data base at a number of jurisdictional levels. The present paper discusses the implementation of change-detection and masking techniques in the updating of Landsat-derived land-cover maps. A baseline landcover classification was first created from a 1976 image, then the adjusted 1976 image was compared with a 1979 scene by the techniques of (1) multidate image classification, (2) difference image-distribution tails thresholding, (3) difference image classification, and (4) multi-dimensional chi-square analysis of a difference image. The union of the results of methods 1, 3 and 4 was used to create a mask of possible change areas between 1976 and 1979, which served to limit analysis of the update image and reduce comparison errors in unchanged areas. The techniques of spatial smoothing of change-detection products, and of combining results of difference change-detection algorithms are also shown to improve Landsat change-detection accuracies.

Harmonic Series Meets Fibonacci Sequence

ERIC Educational Resources Information Center

Chen, Hongwei; Kennedy, Chris

2012-01-01

The terms of a conditionally convergent series may be rearranged to converge to any prescribed real value. What if the harmonic series is grouped into Fibonacci length blocks? Or the harmonic series is arranged in alternating Fibonacci length blocks? Or rearranged and alternated into separate blocks of even and odd terms of Fibonacci length?

Tuvan Throat Singing and Harmonics

ERIC Educational Resources Information Center

Ruiz, Michael J.; Wilken, David

2018-01-01

Tuvan throat singing, also called overtone singing, provides for an exotic demonstration of the physics of harmonics as well as introducing an Asian musical aesthetic. A low fundamental is sung and the singer skillfully alters the resonances of the vocal system to enhance an overtone (harmonic above the fundamental). The result is that the…

A sensible technique to detect mollicutes impurities in human cells cultured in GMP condition.

PubMed

Ugolotti, Elisabetta; Vanni, Irene

2014-01-01

In therapeutic trials the use of manipulated cell cultures for clinical applications is often required. Mollicutes microorganism contamination of tissue cultures is a major problem because it can determine various and severe alterations in cellular function. Thus methods able to detect and trace cell cultures with Mollicutes contamination are needed in the monitoring of cells grown under good manufacturing practice conditions, and cell lines in continuous culture must be tested at regular intervals. We here describe a multiplex quantitative polymerase chain reaction assay able to detect contaminant Mollicutes species in a single-tube reaction through analysis of 16S-23S rRNA intergenic spacer regions and Tuf and P1 cytoadhesin genes. The method shows a sensitivity, specificity, and robustness comparable with the culture and the indicator cell culture as required by the European Pharmacopoeia guidelines and was validated following International Conference on Harmonization guidelines and Food and Drug Administration requirements.

Data-Mining Techniques in Detecting Factors Linked to Academic Achievement

ERIC Educational Resources Information Center

Martínez Abad, Fernando; Chaparro Caso López, Alicia A.

2017-01-01

In light of the emergence of statistical analysis techniques based on data mining in education sciences, and the potential they offer to detect non-trivial information in large databases, this paper presents a procedure used to detect factors linked to academic achievement in large-scale assessments. The study is based on a non-experimental,…

Tracking the harmonic response of magnetically-soft sensors for wireless temperature, stress, and corrosive monitoring.

PubMed

Ong, Keat G; Grimes, Craig A

2002-09-30

This paper describes the application of magnetically-soft ribbon-like sensors for measurement of temperature and stress, as well as corrosive monitoring, based upon changes in the amplitudes of the higher-order harmonics generated by the sensors in response to a magnetic interrogation signal. The sensors operate independently of mass loading, and so can be placed or rigidly embedded inside nonmetallic, opaque structures such as concrete or plastic. The passive harmonic-based sensor is remotely monitored through a single coplanar interrogation and detection coil. Effects due to the relative location of the sensor are eliminated by tracking harmonic amplitude ratios, thereby, enabling wide area monitoring. The wireless, passive, mass loading independent nature of the described sensor platform makes it ideally suited for long-term structural monitoring applications, such as measurement of temperature and stress inside concrete structures. A theoretical model is presented to explain the origin and behavior of the higher-order harmonics in response to temperature and stress. c2002 Elsevier Science B.V. All rights reserved.

Tracking the harmonic response of magnetically-soft sensors for wireless temperature, stress, and corrosive monitoring

NASA Technical Reports Server (NTRS)

Ong, Keat G.; Grimes, Craig A.

2002-01-01

This paper describes the application of magnetically-soft ribbon-like sensors for measurement of temperature and stress, as well as corrosive monitoring, based upon changes in the amplitudes of the higher-order harmonics generated by the sensors in response to a magnetic interrogation signal. The sensors operate independently of mass loading, and so can be placed or rigidly embedded inside nonmetallic, opaque structures such as concrete or plastic. The passive harmonic-based sensor is remotely monitored through a single coplanar interrogation and detection coil. Effects due to the relative location of the sensor are eliminated by tracking harmonic amplitude ratios, thereby, enabling wide area monitoring. The wireless, passive, mass loading independent nature of the described sensor platform makes it ideally suited for long-term structural monitoring applications, such as measurement of temperature and stress inside concrete structures. A theoretical model is presented to explain the origin and behavior of the higher-order harmonics in response to temperature and stress. c2002 Elsevier Science B.V. All rights reserved.

Resolution-Enhanced Harmonic and Interharmonic Measurement for Power Quality Analysis in Cyber-Physical Energy System.

PubMed

Liu, Yanchi; Wang, Xue; Liu, Youda; Cui, Sujin

2016-06-27

Power quality analysis issues, especially the measurement of harmonic and interharmonic in cyber-physical energy systems, are addressed in this paper. As new situations are introduced to the power system, the impact of electric vehicles, distributed generation and renewable energy has introduced extra demands to distributed sensors, waveform-level information and power quality data analytics. Harmonics and interharmonics, as the most significant disturbances, require carefully designed detection methods for an accurate measurement of electric loads whose information is crucial to subsequent analyzing and control. This paper gives a detailed description of the power quality analysis framework in networked environment and presents a fast and resolution-enhanced method for harmonic and interharmonic measurement. The proposed method first extracts harmonic and interharmonic components efficiently using the single-channel version of Robust Independent Component Analysis (RobustICA), then estimates the high-resolution frequency from three discrete Fourier transform (DFT) samples with little additional computation, and finally computes the amplitudes and phases with the adaptive linear neuron network. The experiments show that the proposed method is time-efficient and leads to a better accuracy of the simulated and experimental signals in the presence of noise and fundamental frequency deviation, thus providing a deeper insight into the (inter)harmonic sources or even the whole system.

Resolution-Enhanced Harmonic and Interharmonic Measurement for Power Quality Analysis in Cyber-Physical Energy System

PubMed Central

Liu, Yanchi; Wang, Xue; Liu, Youda; Cui, Sujin

2016-01-01

Power quality analysis issues, especially the measurement of harmonic and interharmonic in cyber-physical energy systems, are addressed in this paper. As new situations are introduced to the power system, the impact of electric vehicles, distributed generation and renewable energy has introduced extra demands to distributed sensors, waveform-level information and power quality data analytics. Harmonics and interharmonics, as the most significant disturbances, require carefully designed detection methods for an accurate measurement of electric loads whose information is crucial to subsequent analyzing and control. This paper gives a detailed description of the power quality analysis framework in networked environment and presents a fast and resolution-enhanced method for harmonic and interharmonic measurement. The proposed method first extracts harmonic and interharmonic components efficiently using the single-channel version of Robust Independent Component Analysis (RobustICA), then estimates the high-resolution frequency from three discrete Fourier transform (DFT) samples with little additional computation, and finally computes the amplitudes and phases with the adaptive linear neuron network. The experiments show that the proposed method is time-efficient and leads to a better accuracy of the simulated and experimental signals in the presence of noise and fundamental frequency deviation, thus providing a deeper insight into the (inter)harmonic sources or even the whole system. PMID:27355946

New Evidence That Nonlinear Source-Filter Coupling Affects Harmonic Intensity and fo Stability During Instances of Harmonics Crossing Formants.

PubMed

Maxfield, Lynn; Palaparthi, Anil; Titze, Ingo

2017-03-01

The traditional source-filter theory of voice production describes a linear relationship between the source (glottal flow pulse) and the filter (vocal tract). Such a linear relationship does not allow for nor explain how changes in the filter may impact the stability and regularity of the source. The objective of this experiment was to examine what effect unpredictable changes to vocal tract dimensions could have on fo stability and individual harmonic intensities in situations in which low frequency harmonics cross formants in a fundamental frequency glide. To determine these effects, eight human subjects (five male, three female) were recorded producing fo glides while their vocal tracts were artificially lengthened by a section of vinyl tubing inserted into the mouth. It was hypothesized that if the source and filter operated as a purely linear system, harmonic intensities would increase and decrease at nearly the same rates as they passed through a formant bandwidth, resulting in a relatively symmetric peak on an intensity-time contour. Additionally, fo stability should not be predictably perturbed by formant/harmonic crossings in a linear system. Acoustic analysis of these recordings, however, revealed that harmonic intensity peaks were asymmetric in 76% of cases, and that 85% of fo instabilities aligned with a crossing of one of the first four harmonics with the first three formants. These results provide further evidence that nonlinear dynamics in the source-filter relationship can impact fo stability as well as harmonic intensities as harmonics cross through formant bandwidths. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Label-free imaging of atherosclerotic plaques using third-harmonic generation microscopy

PubMed Central

Small, David M.; Jones, Jason S.; Tendler, Irwin I.; Miller, Paul E.; Ghetti, Andre; Nishimura, Nozomi

2017-01-01

Multiphoton microscopy using laser sources in the mid-infrared range (MIR, 1,300 nm and 1,700 nm) was used to image atherosclerotic plaques from murine and human samples. Third harmonic generation (THG) from atherosclerotic plaques revealed morphological details of cellular and extracellular lipid deposits. Simultaneous nonlinear optical signals from the same laser source, including second harmonic generation and endogenous fluorescence, resulted in label-free images of various layers within the diseased vessel wall. The THG signal adds an endogenous contrast mechanism with a practical degree of specificity for atherosclerotic plaques that complements current nonlinear optical methods for the investigation of cardiovascular disease. Our use of whole-mount tissue and backward scattered epi-detection suggests THG could potentially be used in the future as a clinical tool. PMID:29359098

A new imaging technique for detecting interstellar communications

NASA Astrophysics Data System (ADS)

Vallerga, John; Welsh, Barry; Kotze, Marissa; Siegmund, Oswald

2017-01-01

We report on a unique detection methodology using the Berkeley Visible Image Tube (BVIT) mounted on the 10m Southern African Large Telescope (SALT) to search for laser pulses originating in communications from advanced extraterrestrial (ET) civilizations residing on nearby Earth-like planets located within their habitability zones. The detection technique assumes that ET communicates through high powered pulsed lasers with pulse durations on the order of 5 nanoseconds, the signals thereby being brighter than that of the host star within this very short period of time. Our technique turns down the gain of the optically sensitive photon counting microchannel plate detector such that ~30 photons are required in a 5ns window to generate an imaged event. Picking a priori targets with planets in the habitable zone substantially reduces the false alarm rate. Interplanetary communication by optical masers was first postulated by Schwartz and Townes in 1961. Under the assumption that ET has access to a 10 m class telescope operated as a transmitter then we could detect lasers with a similar power to that of the Livermore Laboratory laser (~1.8Mj per pulse), to a distance of ~ 1000 pc. In this talk we present the results of 2400 seconds of BVIT observations on the SALT of the star Wolf 1061, which is known to harbor an Earth-sized exoplanet located in the habitability zone. At this distance (4.3 pc), BVIT on SALT could detect a 48 joule per pulse laser, now commercially available as tabletop devices.

Detection of fundamental and harmonic type III radio emission and the associated Langmuir waves at the source region

NASA Technical Reports Server (NTRS)

Reiner, M. J.; Stone, R. G.; Fainberg, J.

1992-01-01

Type III radio emission generated in the vicinity of the Ulysses spacecraft has been detected at both the fundamental and harmonic of the local plasma frequency. The observations represent the first clear evidence of locally generated type III radio emission. This local emission shows no evidence of frequency drift, exhibits a relatively short rise time, is less intense than the observed remotely generated radio emission, and is temporally correlated with observed in situ Langmuir waves. The observations were made with the unified radio astronomy and wave (URAP) experiment on the Ulysses spacecraft between 1990 November 4 and 1991 April 30, as it traveled from 1 to 3 AU from the sun. During this time period many thousands of bursts were observed. However, only three examples of local emission and associated Langmuir waves were identified. This supports previous suggestions that type III radio emission is generated in localized regions of the interplanetary medium, rather than uniformly along the extent of the electron exciter beam.

Three-in-one resonance tube for harmonic series sound wave experiments

NASA Astrophysics Data System (ADS)

Jaafar, Rosly; Nazihah Mat Daud, Anis; Ali, Shaharudin; Kadri Ayop, Shahrul

2017-07-01

In this study we constructed a special three-in-one resonance tube for a harmonic series sound waves experiment. It is designed for three different experiments: both-open-end, one-closed-end and both-closed-end tubes. The resonance tube consists of a PVC conduit with a rectangular hole, rubber tube, plastic stopper with an embedded microphone and a plastic stopper. The resonance tube is utilized with visual analyser freeware to detect, display and measure the resonance frequencies for each harmonic series. The speeds of sound in air, v, are determined from the gradient of the 2(L+e) versus n fn-1 , 4(L+e) versus n fn-1 and 2L versus n fn-1 graphs for both-open-end, one-closed-end and both-closed-end tubes, respectively. The compatibility of a resonance tube for a harmonic series experiment is determined by comparing the experimental and standard values of v. The use of a resonance tube produces accurate results for v within a 1.91% error compared to its standard value. It can also be used to determine the values of end correction, e, in both-open-end and one-closed-end tubes. The special resonance tube can also be used for the values of n for a harmonic series experiment in the three types of resonance tubes: both-open-end, one-closed-end and both-closed-end tubes.

Indirect fluorometric detection techniques on thin layer chromatography and effect of ultrasound on gel electrophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yinfa, Ma.

Thin-layer chromatography (TLC) is a broadly applicable separation technique. It offers many advantages over high performance liquid chromatography (HPLC), such as easily adapted for two-dimensional separation, for whole-column'' detection and for handling multiple samples, etc. However, due to its draggy development of detection techniques comparing with HPLC, TLC has not received the attention it deserves. Therefore, exploring new detection techniques is very important to the development of TLC. It is the principal of this dissertation to present a new detection method for TLC -- indirect fluorometric detection method. This detection technique is universal sensitive, nondestructive, and simple. This will bemore » described in detail from Sections 1 through Section 5. Section 1 and 3 describe the indirect fluorometric detection of anions and nonelectrolytes in TLC. In Section 2, a detection method for cations based on fluorescence quenching of ethidium bromide is presented. In Section 4, a simple and interesting TLC experiment is designed, three different fluorescence detection principles are used for the determination of caffeine, saccharin and sodium benzoate in beverages. A laser-based indirect fluorometric detection technique in TLC is developed in Section 5. Section 6 is totally different from Sections 1 through 5. An ultrasonic effect on the separation of DNA fragments in agarose gel electrophoresis is investigated. 262 refs.« less

Drop-Off Detection with the Long Cane: Effects of Different Cane Techniques on Performance

ERIC Educational Resources Information Center

Kim, Dae Shik; Emerson, Robert Wall; Curtis, Amy

2009-01-01

This study compared the drop-off detection performance with the two-point touch and constant contact cane techniques using a repeated-measures design with a convenience sample of 15 cane users with visual impairments. The constant contact technique was superior to the two-point touch technique in the drop-off detection rate and the 50% detection…

First-harmonic nonlinearities can predict unseen third-harmonics in medium-amplitude oscillatory shear (MAOS)

NASA Astrophysics Data System (ADS)

Carey-De La Torre, Olivia; Ewoldt, Randy H.

2018-02-01

We use first-harmonic MAOS nonlinearities from G 1' and G 1″ to test a predictive structure-rheology model for a transient polymer network. Using experiments with PVA-Borax (polyvinyl alcohol cross-linked by sodium tetraborate (borax)) at 11 different compositions, the model is calibrated to first-harmonic MAOS data on a torque-controlled rheometer at a fixed frequency, and used to predict third-harmonic MAOS on a displacement controlled rheometer at a different frequency three times larger. The prediction matches experiments for decomposed MAOS measures [ e 3] and [ v 3] with median disagreement of 13% and 25%, respectively, across all 11 compositions tested. This supports the validity of this model, and demonstrates the value of using all four MAOS signatures to understand and test structure-rheology relations for complex fluids.

Harmonic generation with a dual frequency pulse.

PubMed

Keravnou, Christina P; Averkiou, Michalakis A

2014-05-01

Nonlinear imaging was implemented in commercial ultrasound systems over the last 15 years offering major advantages in many clinical applications. In this work, pulsing schemes coupled with a dual frequency pulse are presented. The pulsing schemes considered were pulse inversion, power modulation, and power modulated pulse inversion. The pulse contains a fundamental frequency f and a specified amount of its second harmonic 2f. The advantages and limitations of this method were evaluated with both acoustic measurements of harmonic generation and theoretical simulations based on the KZK equation. The use of two frequencies in a pulse results in the generation of the sum and difference frequency components in addition to the other harmonic components. While with single frequency pulses, only power modulation and power modulated pulse inversion contained odd harmonic components, with the dual frequency pulse, pulse inversion now also contains odd harmonic components.

Epileptic seizure detection in EEG signal using machine learning techniques.

PubMed

Jaiswal, Abeg Kumar; Banka, Haider

2018-03-01

Epilepsy is a well-known nervous system disorder characterized by seizures. Electroencephalograms (EEGs), which capture brain neural activity, can detect epilepsy. Traditional methods for analyzing an EEG signal for epileptic seizure detection are time-consuming. Recently, several automated seizure detection frameworks using machine learning technique have been proposed to replace these traditional methods. The two basic steps involved in machine learning are feature extraction and classification. Feature extraction reduces the input pattern space by keeping informative features and the classifier assigns the appropriate class label. In this paper, we propose two effective approaches involving subpattern based PCA (SpPCA) and cross-subpattern correlation-based PCA (SubXPCA) with Support Vector Machine (SVM) for automated seizure detection in EEG signals. Feature extraction was performed using SpPCA and SubXPCA. Both techniques explore the subpattern correlation of EEG signals, which helps in decision-making process. SVM is used for classification of seizure and non-seizure EEG signals. The SVM was trained with radial basis kernel. All the experiments have been carried out on the benchmark epilepsy EEG dataset. The entire dataset consists of 500 EEG signals recorded under different scenarios. Seven different experimental cases for classification have been conducted. The classification accuracy was evaluated using tenfold cross validation. The classification results of the proposed approaches have been compared with the results of some of existing techniques proposed in the literature to establish the claim.

[Harmonization of TSH Measurements.

PubMed

Takeoka, Keiko; Hidaka, Yoh; Hishinuma, Akira; Ikeda, Katsuyoshi; Okubo, Shigeo; Tsuchiya, Tatsuyuki; Hashiguchi, Teruto; Furuta, Koh; Hotta, Taeko; Matsushita, Kazuyuki; Matsumoto, Hiroyuki; Murakami, Masami; Maekawa, Masato

2016-05-01

The measured concentration of thyroid stimulating hormone (TSH) differs depending on the reagents used. Harmonization of TSH is crucial because the decision limits are described in current clinical practice guide- lines as absolute values, e.g. 2.5 mIU/L in early pregnancy. In this study, we tried to harmonize the report- ed concentrations of TSH using the all-procedure trimmed mean. TSH was measured in 146 serum samples, with values ranging from 0.01 to 18.8 mIU/L, using 4 immunoassays. The concentration of TSH was highest with E test TOSOH and lowest with LUMIPULSE. The concentrations with each reagent were recalculated with the following formulas: E test TOSOH 0.855x-0.014; ECLusys 0.993x+0.079; ARCHITECT 1.041x- 0.010; and LUMIPULSE 1.096x-0.015. Recalculation eliminated the between-assay discrepancy. These formulas may be used until harmonization of TSH is achieved by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).

Sensitive Technique For Detecting Alignment Of Seed Laser

NASA Technical Reports Server (NTRS)

Barnes, Norman P.

1994-01-01

Frequency response near resonance measured. Improved technique for detection and quantification of alignment of injection-seeding laser with associated power-oscillator laser proposed. Particularly useful in indicating alignment at spectral purity greater than 98 percent because it becomes more sensitive as perfect alignment approached. In addition, implemented relatively easily, without turning on power-oscillator laser.

Maelstrom Research guidelines for rigorous retrospective data harmonization

PubMed Central

Fortier, Isabel; Raina, Parminder; Van den Heuvel, Edwin R; Griffith, Lauren E; Craig, Camille; Saliba, Matilda; Doiron, Dany; Stolk, Ronald P; Knoppers, Bartha M; Ferretti, Vincent; Granda, Peter; Burton, Paul

2017-01-01

Abstract Background: It is widely accepted and acknowledged that data harmonization is crucial: in its absence, the co-analysis of major tranches of high quality extant data is liable to inefficiency or error. However, despite its widespread practice, no formalized/systematic guidelines exist to ensure high quality retrospective data harmonization. Methods: To better understand real-world harmonization practices and facilitate development of formal guidelines, three interrelated initiatives were undertaken between 2006 and 2015. They included a phone survey with 34 major international research initiatives, a series of workshops with experts, and case studies applying the proposed guidelines. Results: A wide range of projects use retrospective harmonization to support their research activities but even when appropriate approaches are used, the terminologies, procedures, technologies and methods adopted vary markedly. The generic guidelines outlined in this article delineate the essentials required and describe an interdependent step-by-step approach to harmonization: 0) define the research question, objectives and protocol; 1) assemble pre-existing knowledge and select studies; 2) define targeted variables and evaluate harmonization potential; 3) process data; 4) estimate quality of the harmonized dataset(s) generated; and 5) disseminate and preserve final harmonization products. Conclusions: This manuscript provides guidelines aiming to encourage rigorous and effective approaches to harmonization which are comprehensively and transparently documented and straightforward to interpret and implement. This can be seen as a key step towards implementing guiding principles analogous to those that are well recognised as being essential in securing the foundational underpinning of systematic reviews and the meta-analysis of clinical trials. PMID:27272186

The Outlier Detection for Ordinal Data Using Scalling Technique of Regression Coefficients

NASA Astrophysics Data System (ADS)

Adnan, Arisman; Sugiarto, Sigit

2017-06-01

The aims of this study is to detect the outliers by using coefficients of Ordinal Logistic Regression (OLR) for the case of k category responses where the score from 1 (the best) to 8 (the worst). We detect them by using the sum of moduli of the ordinal regression coefficients calculated by jackknife technique. This technique is improved by scalling the regression coefficients to their means. R language has been used on a set of ordinal data from reference distribution. Furthermore, we compare this approach by using studentised residual plots of jackknife technique for ANOVA (Analysis of Variance) and OLR. This study shows that the jackknifing technique along with the proper scaling may lead us to reveal outliers in ordinal regression reasonably well.

Exploring machine-learning-based control plane intrusion detection techniques in software defined optical networks

NASA Astrophysics Data System (ADS)

Zhang, Huibin; Wang, Yuqiao; Chen, Haoran; Zhao, Yongli; Zhang, Jie

2017-12-01

In software defined optical networks (SDON), the centralized control plane may encounter numerous intrusion threatens which compromise the security level of provisioned services. In this paper, the issue of control plane security is studied and two machine-learning-based control plane intrusion detection techniques are proposed for SDON with properly selected features such as bandwidth, route length, etc. We validate the feasibility and efficiency of the proposed techniques by simulations. Results show an accuracy of 83% for intrusion detection can be achieved with the proposed machine-learning-based control plane intrusion detection techniques.

Standoff detection: classification of biological aerosols using laser induced fluorescence (LIF) technique

NASA Astrophysics Data System (ADS)

Hausmann, Anita; Duschek, Frank; Fischbach, Thomas; Pargmann, Carsten; Aleksejev, Valeri; Poryvkina, Larisa; Sobolev, Innokenti; Babichenko, Sergey; Handke, Jürgen

2014-05-01

The challenges of detecting hazardous biological materials are manifold: Such material has to be discriminated from other substances in various natural surroundings. The detection sensitivity should be extremely high. As living material may reproduce itself, already one single bacterium may represent a high risk. Of course, identification should be quite fast with a low false alarm rate. Up to now, there is no single technique to solve this problem. Point sensors may collect material and identify it, but the problems of fast identification and especially of appropriate positioning of local collectors are sophisticated. On the other hand, laser based standoff detection may instantaneously provide the information of some accidental spillage of material by detecting the generated thin cloud. LIF technique may classify but hardly identify the substance. A solution can be the use of LIF technique in a first step to collect primary data and - if necessary- followed by utilizing these data for an optimized positioning of point sensors. We perform studies on an open air laser test range at distances between 20 and 135 m applying LIF technique to detect and classify aerosols. In order to employ LIF capability, we use a laser source emitting two wavelengths alternatively, 280 and 355 nm, respectively. Moreover, the time dependence of fluorescence spectra is recorded by a gated intensified CCD camera. Signal processing is performed by dedicated software for spectral pattern recognition. The direct comparison of all results leads to a basic classification of the various compounds.

Evolving optical second-harmonic anisotropy at the cleaved Bi2Se3 surface

NASA Astrophysics Data System (ADS)

An, Yong; Green, Avery; Diebold, Alain

Bismuth selenide (Bi2Se3) is a centrosymmetric topological insulator with conducting surface states. The surface states have been studied by various electrical and optical techniques in air, but ambience effects and surface aging have not been adequately addressed. Optical second-harmonic generation (SHG) is a suitable probe for the Bi2Se3 surface because SHG arises from symmetry breaking at the surface and thus should detect surface states preferentially over bulk states. However, a strong time dependence of SHG is often observed, hampering the detection and investigation of the surface states. Here we find a new phenomenon in which the major and minor intensity lobes of a measured rotational-anisotropy SHG pattern from a cleaved Bi2Se3 (111) surface can significantly change with time and eventually switch their amplitudes. This switching provides a means for tracking the progress of surface oxidation inside a quintuple layer of Bi2Se3. We also perform pump-probe SHG experiments, comparatively on freshly cleaved and oxidized Bi2Se3 surfaces, to study charge dynamics at the oxide/Bi2Se3 interface and to detect spin polarization of photoexcited surface states in the Bi2Se3 topological insulator. This work was supported by the SRC NRI Institute for Nanoelectronics Discovery and Exploration (INDEX).

The Population of Small Comets: Optimum Techniques for Detection

NASA Technical Reports Server (NTRS)

Brandt, John C.

1997-01-01

The goals of this project were: (1) to present evidence to the scientific community for the importance of the small comet population and (2) to develop techniques for optimum detection in order to characterize the population. Our work on techniques has been to develop algorithms for searching images for SCs based on the distinctive properties of comets; (1) motion with respect to background stars; (2) extended source with most light coming from the coma rather than the nucleus; and characteristic spectral signature.

High-harmonic generation by quantum-dot nanorings

NASA Astrophysics Data System (ADS)

Bâldea, Ioan; Gupta, Ashish K.; Cederbaum, Lorenz S.; Moiseyev, Nimrod

2004-06-01

Exact numerical results are obtained within the extended Hubbard Hamiltonian for nanorings consisting of Ag quantum dots (QD’s) with C6v symmetry which interact with a circularly polarized light. The results show that the high-harmonic generation (HHG) spectra obtained from such artificial “molecules” are more pronounced than the HHG spectra obtained from a real molecule such as benzene. Our studies show that the HHG spectra obtained from the QD nanorings consist of two plateaus while only one plateau appears for benzene. The role of electron correlations in the generation of the high-order harmonics is studied, and it is shown that it can increase the intensity of the high-order harmonics. Mainly affected are the harmonics which are located in the second plateau. Selection rules for the produced high harmonics and a new “synergetic” selection rule for the symmetry of the states contributing to the HHG spectrum, a combined effect of spatial and charge conjugation symmetries, are discussed.

Determining Energies and Cross Sections of Individual Ions Using Higher-Order Harmonics in Fourier Transform Charge Detection Mass Spectrometry (FT-CDMS)

NASA Astrophysics Data System (ADS)

Harper, Conner C.; Elliott, Andrew G.; Lin, Haw-Wei; Williams, Evan R.

2018-06-01

A general method for in situ measurements of the energy of individual ions trapped and weighed using charge detection mass spectrometry (CDMS) is described. Highly charged (> 300 e), individual polyethylene glycol (PEG) ions are trapped and oscillate within an electrostatic trap, producing a time domain signal. A segmented Fourier transform (FT) of this signal yields the temporal evolution of the fundamental and harmonic frequencies of ion motion throughout the 500-ms trap time. The ratio of the fundamental frequency and second harmonic (HAR) depends on the ion energy, which is an essential parameter for measuring ion mass in CDMS. This relationship is calibrated using simulated ion signals, and the calibration is compared to the HAR values measured for PEG ion signals where the ion energy was also determined using an independent method that requires that the ions be highly charged (> 300 e). The mean error of 0.6% between the two measurements indicates that the HAR method is an accurate means of ion energy determination that does not depend on ion size or charge. The HAR is determined dynamically over the entire trapping period, making it possible to observe the change in ion energy that takes place as solvent evaporates from the ion and collisions with background gas occur. This method makes it possible to measure mass changes, either from solvent evaporation or from molecular fragmentation (MSn), as well as the cross sections of ions measured using CDMS.

Determining Energies and Cross Sections of Individual Ions Using Higher-Order Harmonics in Fourier Transform Charge Detection Mass Spectrometry (FT-CDMS).

PubMed

Harper, Conner C; Elliott, Andrew G; Lin, Haw-Wei; Williams, Evan R

2018-06-02

A general method for in situ measurements of the energy of individual ions trapped and weighed using charge detection mass spectrometry (CDMS) is described. Highly charged (> 300 e), individual polyethylene glycol (PEG) ions are trapped and oscillate within an electrostatic trap, producing a time domain signal. A segmented Fourier transform (FT) of this signal yields the temporal evolution of the fundamental and harmonic frequencies of ion motion throughout the 500-ms trap time. The ratio of the fundamental frequency and second harmonic (HAR) depends on the ion energy, which is an essential parameter for measuring ion mass in CDMS. This relationship is calibrated using simulated ion signals, and the calibration is compared to the HAR values measured for PEG ion signals where the ion energy was also determined using an independent method that requires that the ions be highly charged (> 300 e). The mean error of 0.6% between the two measurements indicates that the HAR method is an accurate means of ion energy determination that does not depend on ion size or charge. The HAR is determined dynamically over the entire trapping period, making it possible to observe the change in ion energy that takes place as solvent evaporates from the ion and collisions with background gas occur. This method makes it possible to measure mass changes, either from solvent evaporation or from molecular fragmentation (MS n ), as well as the cross sections of ions measured using CDMS. Graphical Abstract.

An optimization-based approach for solving a time-harmonic multiphysical wave problem with higher-order schemes

NASA Astrophysics Data System (ADS)

Mönkölä, Sanna

2013-06-01

This study considers developing numerical solution techniques for the computer simulations of time-harmonic fluid-structure interaction between acoustic and elastic waves. The focus is on the efficiency of an iterative solution method based on a controllability approach and spectral elements. We concentrate on the model, in which the acoustic waves in the fluid domain are modeled by using the velocity potential and the elastic waves in the structure domain are modeled by using displacement. Traditionally, the complex-valued time-harmonic equations are used for solving the time-harmonic problems. Instead of that, we focus on finding periodic solutions without solving the time-harmonic problems directly. The time-dependent equations can be simulated with respect to time until a time-harmonic solution is reached, but the approach suffers from poor convergence. To overcome this challenge, we follow the approach first suggested and developed for the acoustic wave equations by Bristeau, Glowinski, and Périaux. Thus, we accelerate the convergence rate by employing a controllability method. The problem is formulated as a least-squares optimization problem, which is solved with the conjugate gradient (CG) algorithm. Computation of the gradient of the functional is done directly for the discretized problem. A graph-based multigrid method is used for preconditioning the CG algorithm.

Extraction of small boat harmonic signatures from passive sonar.

PubMed

Ogden, George L; Zurk, Lisa M; Jones, Mark E; Peterson, Mary E

2011-06-01

This paper investigates the extraction of acoustic signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the harmonic structure of noise radiated from small boats is developed. The Harmonic Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the harmonic tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. Results are presented that show the HEAT algorithms ability to extract these signatures. © 2011 Acoustical Society of America

Selective detection of cavitation bubbles by triplet pulse sequence in high-intensity focused ultrasound treatment

NASA Astrophysics Data System (ADS)

Iwasaki, Ryosuke; Nagaoka, Ryo; Yoshizawa, Shin; Umemura, Shin-ichiro

2018-07-01

Acoustic cavitation bubbles are known to enhance the heating effect in high-intensity focused ultrasound (HIFU) treatment. The detection of cavitation bubbles with high sensitivity and selectivity is required to predict the therapeutic and side effects of cavitation, and ensure the efficacy and safety of the treatment. A pulse inversion (PI) technique has been widely used for imaging microbubbles through enhancing the second-harmonic component of echo signals. However, it has difficulty in separating the nonlinear response of microbubbles from that due to nonlinear propagation. In this study, a triplet pulse (3P) method was investigated to specifically image cavitation bubbles by extracting the 1.5th fractional harmonic component. The proposed 3P method depicted cavitation bubbles with a contrast ratio significantly higher than those in conventional imaging methods with and without PI. The results suggest that the 3P method is effective for specifically detecting microbubbles in cavitation-enhanced HIFU treatment.

Promoting Spontaneous Second Harmonic Generation through Organogelation.

PubMed

Marco, A Belén; Aparicio, Fátima; Faour, Lara; Iliopoulos, Konstantinos; Morille, Yohann; Allain, Magali; Franco, Santiago; Andreu, Raquel; Sahraoui, Bouchta; Gindre, Denis; Canevet, David; Sallé, Marc

2016-07-27

An organogelator based on the Disperse Red nonlinear optical chromophore was synthesized according to a simple and efficient three-step procedure. The supramolecular gel organization leads to xerogels which display a spontaneous second harmonic generation (SHG) response without any need for preprocessing, and this SHG activity appears to be stable over several months. These findings, based on an intrinsic structural approach, are supported by favorable intermolecular supramolecular interactions, which promote a locally non-centrosymmetric NLO-active organization. This is in sharp contrast with most materials designed for SHG purposes, which generally require the use of expensive or heavy-to-handle external techniques for managing the dipoles' alignment.

General Criterion for Harmonicity

NASA Astrophysics Data System (ADS)

Proesmans, Karel; Vandebroek, Hans; Van den Broeck, Christian

2017-10-01

Inspired by Kubo-Anderson Markov processes, we introduce a new class of transfer matrices whose largest eigenvalue is determined by a simple explicit algebraic equation. Applications include the free energy calculation for various equilibrium systems and a general criterion for perfect harmonicity, i.e., a free energy that is exactly quadratic in the external field. As an illustration, we construct a "perfect spring," namely, a polymer with non-Gaussian, exponentially distributed subunits which, nevertheless, remains harmonic until it is fully stretched. This surprising discovery is confirmed by Monte Carlo and Langevin simulations.

The Application of Speaker Recognition Techniques in the Detection of Tsunamigenic Earthquakes

NASA Astrophysics Data System (ADS)

Gorbatov, A.; O'Connell, J.; Paliwal, K.

2015-12-01

Tsunami warning procedures adopted by national tsunami warning centres largely rely on the classical approach of earthquake location, magnitude determination, and the consequent modelling of tsunami waves. Although this approach is based on known physics theories of earthquake and tsunami generation processes, this may be the main shortcoming due to the need to satisfy minimum seismic data requirement to estimate those physical parameters. At least four seismic stations are necessary to locate the earthquake and a minimum of approximately 10 minutes of seismic waveform observation to reliably estimate the magnitude of a large earthquake similar to the 2004 Indian Ocean Tsunami Earthquake of M9.2. Consequently the total time to tsunami warning could be more than half an hour. In attempt to reduce the time of tsunami alert a new approach is proposed based on the classification of tsunamigenic and non tsunamigenic earthquakes using speaker recognition techniques. A Tsunamigenic Dataset (TGDS) was compiled to promote the development of machine learning techniques for application to seismic trace analysis and, in particular, tsunamigenic event detection, and compare them to existing seismological methods. The TGDS contains 227 off shore events (87 tsunamigenic and 140 non-tsunamigenic earthquakes with M≥6) from Jan 2000 to Dec 2011, inclusive. A Support Vector Machine classifier using a radial-basis function kernel was applied to spectral features derived from 400 sec frames of 3-comp. 1-Hz broadband seismometer data. Ten-fold cross-validation was used during training to choose classifier parameters. Voting was applied to the classifier predictions provided from each station to form an overall prediction for an event. The F1 score (harmonic mean of precision and recall) was chosen to rate each classifier as it provides a compromise between type-I and type-II errors, and due to the imbalance between the representative number of events in the tsunamigenic and non

Failure detection and fault management techniques for flush airdata sensing systems

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A.; Moes, Timothy R.; Leondes, Cornelius T.

1992-01-01

Methods based on chi-squared analysis are presented for detecting system and individual-port failures in the high-angle-of-attack flush airdata sensing system on the NASA F-18 High Alpha Research Vehicle. The HI-FADS hardware is introduced, and the aerodynamic model describes measured pressure in terms of dynamic pressure, angle of attack, angle of sideslip, and static pressure. Chi-squared analysis is described in the presentation of the concept for failure detection and fault management which includes nominal, iteration, and fault-management modes. A matrix of pressure orifices arranged in concentric circles on the nose of the aircraft indicate the parameters which are applied to the regression algorithms. The sensing techniques are applied to the F-18 flight data, and two examples are given of the computed angle-of-attack time histories. The failure-detection and fault-management techniques permit the matrix to be multiply redundant, and the chi-squared analysis is shown to be useful in the detection of failures.

Twenty-four tuba harmonics using a single pipe length

NASA Astrophysics Data System (ADS)

Holmes, Bud; Ruiz, Michael J.

2017-03-01

Harmonics arise naturally from the resonances in strings and pipes. A video demonstration (Ruiz 2016 YouTube: Tuba Harmonics (https://youtu.be/souhEzOP9c4)) is provided where a tubist (coauthor Holmes) produces a phenomenal 24 harmonics using a single tuba pipe length by controlling the buzz of his lips. The frequencies of the harmonics, measured with the free software program Audacity, fall excellently on a linear fit using a spreadsheet. The skillful musical production of so many harmonics with a fixed pipe length is an extraordinary illustration of physics.

Harmonic magneto-electric response in GaFeO3

NASA Astrophysics Data System (ADS)

Naiya, Amit Kumar; Awasthi, A. M.

2018-04-01

GaFeO3 is a well-known multiferroic material. Like optical second harmonic generation, it also generates radio frequency (RF) second harmonic due to its non-centrosymmetric orthorhombic structure. The harmonic RF response also features a magneto-electric character comparable in prominence to that of the fundamental response. We measured complex parts of the fundamental and the second harmonic over 80 K to 300 K. The second harmonic permittivity and its phase angle change sign at the spin glass transition temperature Tg = 200 K and becomes dispersive above ˜280 K.

Automatic Detection of Optic Disc in Retinal Image by Using Keypoint Detection, Texture Analysis, and Visual Dictionary Techniques

PubMed Central

Bayır, Şafak

2016-01-01

With the advances in the computer field, methods and techniques in automatic image processing and analysis provide the opportunity to detect automatically the change and degeneration in retinal images. Localization of the optic disc is extremely important for determining the hard exudate lesions or neovascularization, which is the later phase of diabetic retinopathy, in computer aided eye disease diagnosis systems. Whereas optic disc detection is fairly an easy process in normal retinal images, detecting this region in the retinal image which is diabetic retinopathy disease may be difficult. Sometimes information related to optic disc and hard exudate information may be the same in terms of machine learning. We presented a novel approach for efficient and accurate localization of optic disc in retinal images having noise and other lesions. This approach is comprised of five main steps which are image processing, keypoint extraction, texture analysis, visual dictionary, and classifier techniques. We tested our proposed technique on 3 public datasets and obtained quantitative results. Experimental results show that an average optic disc detection accuracy of 94.38%, 95.00%, and 90.00% is achieved, respectively, on the following public datasets: DIARETDB1, DRIVE, and ROC. PMID:27110272

Detection of cavitation vortex in hydraulic turbines using acoustic techniques

NASA Astrophysics Data System (ADS)

Candel, I.; Bunea, F.; Dunca, G.; Bucur, D. M.; Ioana, C.; Reeb, B.; Ciocan, G. D.

2014-03-01

Cavitation phenomena are known for their destructive capacity in hydraulic machineries and are caused by the pressure decrease followed by an implosion when the cavitation bubbles find an adverse pressure gradient. A helical vortex appears in the turbine diffuser cone at partial flow rate operation and can be cavitating in its core. Cavity volumes and vortex frequencies vary with the under-pressure level. If the vortex frequency comes close to one of the eigen frequencies of the turbine, a resonance phenomenon may occur, the unsteady fluctuations can be amplified and lead to important turbine and hydraulic circuit damage. Conventional cavitation vortex detection techniques are based on passive devices (pressure sensors or accelerometers). Limited sensor bandwidths and low frequency response limit the vortex detection and characterization information provided by the passive techniques. In order to go beyond these techniques and develop a new active one that will remove these drawbacks, previous work in the field has shown that techniques based on acoustic signals using adapted signal content to a particular hydraulic situation, can be more robust and accurate. The cavitation vortex effects in the water flow profile downstream hydraulic turbines runner are responsible for signal content modifications. Basic signal techniques use narrow band signals traveling inside the flow from an emitting transducer to a receiving one (active sensors). Emissions of wide band signals in the flow during the apparition and development of the vortex embeds changes in the received signals. Signal processing methods are used to estimate the cavitation apparition and evolution. Tests done in a reduced scale facility showed that due to the increasing flow rate, the signal -- vortex interaction is seen as modifications on the received signal's high order statistics and bandwidth. Wide band acoustic transducers have a higher dynamic range over mechanical elements; the system's reaction time

Data-adaptive harmonic analysis and prediction of sea level change in North Atlantic region

NASA Astrophysics Data System (ADS)

Kondrashov, D. A.; Chekroun, M.

2017-12-01

This study aims to characterize North Atlantic sea level variability across the temporal and spatial scales. We apply recently developed data-adaptive Harmonic Decomposition (DAH) and Multilayer Stuart-Landau Models (MSLM) stochastic modeling techniques [Chekroun and Kondrashov, 2017] to monthly 1993-2017 dataset of Combined TOPEX/Poseidon, Jason-1 and Jason-2/OSTM altimetry fields over North Atlantic region. The key numerical feature of the DAH relies on the eigendecomposition of a matrix constructed from time-lagged spatial cross-correlations. In particular, eigenmodes form an orthogonal set of oscillating data-adaptive harmonic modes (DAHMs) that come in pairs and in exact phase quadrature for a given temporal frequency. Furthermore, the pairs of data-adaptive harmonic coefficients (DAHCs), obtained by projecting the dataset onto associated DAHMs, can be very efficiently modeled by a universal parametric family of simple nonlinear stochastic models - coupled Stuart-Landau oscillators stacked per frequency, and synchronized across different frequencies by the stochastic forcing. Despite the short record of altimetry dataset, developed DAH-MSLM model provides for skillful prediction of key dynamical and statistical features of sea level variability. References M. D. Chekroun and D. Kondrashov, Data-adaptive harmonic spectra and multilayer Stuart-Landau models. HAL preprint, 2017, https://hal.archives-ouvertes.fr/hal-01537797

Study of thin film production of ceramic ZrO2 on silicon wafer using second harmonic Nd-Yag laser with pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Suliyanti, Maria M.; Hidayah, Affi Nur; Kurniawan, K. H.

2012-06-01

Study about thin film production using technique pulsed laser deposition have been done. The Pulsed Laser Deposition (PLD) method has been used for growing thin film of ZrO2 on silicon wafer substrate (111 single crystal, thickness 400μm and diameter 7.5 cm). The target made from Zirconia oxide powder mixing with PVA and press using pressure 100kgN. The laser beam was focused by a lens (f = 100mm) through a quartz window onto the sample surface and the substrate was placed in parallel line with target. The distance between the target and the substrate is about 1 cm. The early results of this synthesis using 75 mJ Nd-YAG second harmonic laser pulse (532 nm Nd-YAG) and low pressure chamber surrounding gas 5 Torr. The irradiation of laser take around 6000 shoots or 10 minutes using frequencies laser 10 Hz. The micro thickness of film can be produced on silicon wafer using this technique. The results of ZrO2 thin film on substrate about 26.92%.

Loop-mediated isothermal amplification (LAMP): a versatile technique for detection of micro-organisms.

PubMed

Wong, Y-P; Othman, S; Lau, Y-L; Radu, S; Chee, H-Y

2018-03-01

Loop-mediated isothermal amplification (LAMP) amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions by using a DNA polymerase with high displacement strand activity and a set of specifically designed primers to amplify targeted DNA strands. Following its first discovery by Notomi et al. ( Nucleic Acids Res 28: E63), LAMP was further developed over the years which involved the combination of this technique with other molecular approaches, such as reverse transcription and multiplex amplification for the detection of infectious diseases caused by micro-organisms in humans, livestock and plants. In this review, available types of LAMP techniques will be discussed together with their applications in detection of various micro-organisms. Up to date, there are varieties of LAMP detection methods available including colorimetric and fluorescent detection, real-time monitoring using turbidity metre and detection using lateral flow device which will also be highlighted in this review. Apart from that, commercialization of LAMP technique had also been reported such as lyophilized form of LAMP reagents kit and LAMP primer sets for detection of pathogenic micro-organisms. On top of that, advantages and limitations of this molecular detection method are also described together with its future potential as a diagnostic method for infectious disease. © 2017 The Society for Applied Microbiology.

A Time-Frequency Respiration Tracking System using Non-Contact Bed Sensors with Harmonic Artifact Rejection

PubMed Central

Beattie, Zachary T.; Jacobs, Peter G.; Riley, Thomas C.; Hagen, Chad C.

2015-01-01

Sleep apnea is a serious health condition that affects many individuals and has been associated with serious health conditions such as cardiovascular disease. Clinical diagnosis of sleep apnea requires that a patient spend the night in a sleep clinic while being wired up to numerous obtrusive sensors. We are developing a system that utilizes respiration rate and breathing amplitude inferred from non-contact bed sensors (i.e. load cells placed under bed supports) to detect sleep apnea. Multi-harmonic artifacts generated either biologically or as a result of the impulse response of the bed have made it challenging to track respiration rate and amplitude with high resolution in time. In this paper, we present an algorithm that can accurately track respiration on a second-by-second basis while removing noise harmonics. The algorithm is tested using data collected from 5 patients during overnight sleep studies. Respiration rate is compared with polysomnography estimations of respiration rate estimated by a technician following clinical standards. Results indicate that certain subjects exhibit a large harmonic component of their breathing signal that can be removed by our algorithm. When compared with technician transcribed respiration rates using polysomnography signals, we demonstrate improved accuracy of respiration rate tracking using harmonic artifact rejection (mean error: 0.18 breaths/minute) over tracking not using harmonic artifact rejection (mean error: −2.74 breaths/minute). PMID:26738176

Investigation of a Moire Based Crack Detection Technique for Propulsion Health Monitoring

NASA Technical Reports Server (NTRS)

Woike, Mark R.; Abudl-Aziz, Ali; Fralick, Gustave C.; Wrbanek, John D.

2012-01-01

The development of techniques for the health monitoring of the rotating components in gas turbine engines is of major interest to NASA s Aviation Safety Program. As part of this on-going effort several experiments utilizing a novel optical Moir based concept along with external blade tip clearance and shaft displacement instrumentation were conducted on a simulated turbine engine disk as a means of demonstrating a potential optical crack detection technique. A Moir pattern results from the overlap of two repetitive patterns with slightly different periods. With this technique, it is possible to detect very small differences in spacing and hence radial growth in a rotating disk due to a flaw such as a crack. The experiment involved etching a circular reference pattern on a subscale engine disk that had a 50.8 mm (2 in.) long notch machined into it to simulate a crack. The disk was operated at speeds up to 12 000 rpm and the Moir pattern due to the shift with respect to the reference pattern was monitored as a means of detecting the radial growth of the disk due to the defect. In addition, blade displacement data were acquired using external blade tip clearance and shaft displacement sensors as a means of confirming the data obtained from the optical technique. The results of the crack detection experiments and its associated analysis are presented in this paper.

Practical Tools to Foster Harmonic Understanding

ERIC Educational Resources Information Center

Johnson, Erik

2013-01-01

Among the elements required to develop a comprehensive understanding of music is students' ability to perceive, recognize, and label the harmonies they hear. Harmonic dictation is among the strategies that teachers have traditionally chosen to help students develop harmonic awareness. However, the highly idiosyncratic ways that students approach…

Optimal control of a harmonic oscillator: Economic interpretations

NASA Astrophysics Data System (ADS)

Janová, Jitka; Hampel, David

2013-10-01

Optimal control is a popular technique for modelling and solving the dynamic decision problems in economics. A standard interpretation of the criteria function and Lagrange multipliers in the profit maximization problem is well known. On a particular example, we aim to a deeper understanding of the possible economic interpretations of further mathematical and solution features of the optimal control problem: we focus on the solution of the optimal control problem for harmonic oscillator serving as a model for Phillips business cycle. We discuss the economic interpretations of arising mathematical objects with respect to well known reasoning for these in other problems.

Quasi-phase-matching of only even-order high harmonics.

PubMed

Diskin, Tzvi; Cohen, Oren

2014-03-24

High harmonic spectrum of a quasi-monochromatic pump that interacts with isotropic media consists of only odd-order harmonics. Addition of a secondary pump, e.g. a static field or the second harmonic of the primary pump, can results with generation of both odd and even harmonics of the primary pump. We propose a method for quasi-phase matching of only the even-order harmonics of the primary pump. We formulate a theory for this process and demonstrate it numerically. We also show that it leads to attosecond pulse trains with constant carrier envelop phase and high repetition rate.

Analysis of Even Harmonics Generation in an Isolated Electric Power System

NASA Astrophysics Data System (ADS)

Kanao, Norikazu; Hayashi, Yasuhiro; Matsuki, Junya

Harmonics bred from loads are mainly odd order because the current waveform has half-wave symmetry. Since the even harmonics are negligibly small, those are not generally measured in electric power systems. However, even harmonics were measured at a 500/275/154kV substation in Hokuriku Electric Power Company after removal of a transmission line fault. The even harmonics caused malfunctions of protective digital relays because the relays used 4th harmonics at the input filter as automatic supervisory signal. This paper describes the mechanism of generation of the even harmonics by comparing measured waveforms with ATP-EMTP simulation results. As a result of analysis, it is cleared that even harmonics are generated by three causes. The first cause is a magnetizing current of transformers due to flux deviation by DC component of a fault current. The second one is due to harmonic conversion of a synchronous machine which generates even harmonics when direct current component or even harmonic current flow into the machine. The third one is that increase of harmonic impedance due to an isolated power system produces harmonic voltages. The design of the input filter of protective digital relays should consider even harmonics generation in an isolated power system.

Selection rules for harmonic generation in solids

NASA Astrophysics Data System (ADS)

Moiseyev, Nimrod

2015-05-01

High-order harmonic generation (HHG) in a bulk crystal was first observed in 2011 [S. Ghimire, A. D. DiChiara, E. Sistrunk, P. Agostini, L. F. DiMauro, and D. A. Reis, Nat. Phys. 7, 138 (2011), 10.1038/nphys1847]. Only odd-order harmonics were observed as expected on the basis of the selection rules in solids, which were derived when only the interband currents were taken into consideration. Here we study HHG in solids when the intraband currents are taken into consideration as well. We show that the dynamical selection rules are broken in solids and the possibility of generation of even-order harmonics cannot be excluded on the basis of the dynamical symmetry analysis. However, a simple analysis of the expression we obtained for the amplitude of the emitted high-order harmonics shows, without the need to carry out numerical calculations, that the even-order harmonics are suppressed due to the localization of the field-free one-electron density probability on the atoms in the solids.

Signal Detection Techniques for Diagnostic Monitoring of Space Shuttle Main Engine Turbomachinery

NASA Technical Reports Server (NTRS)

Coffin, Thomas; Jong, Jen-Yi

1986-01-01

An investigation to develop, implement, and evaluate signal analysis techniques for the detection and classification of incipient mechanical failures in turbomachinery is reviewed. A brief description of the Space Shuttle Main Engine (SSME) test/measurement program is presented. Signal analysis techniques available to describe dynamic measurement characteristics are reviewed. Time domain and spectral methods are described, and statistical classification in terms of moments is discussed. Several of these waveform analysis techniques have been implemented on a computer and applied to dynamc signals. A laboratory evaluation of the methods with respect to signal detection capability is described. A unique coherence function (the hyper-coherence) was developed through the course of this investigation, which appears promising as a diagnostic tool. This technique and several other non-linear methods of signal analysis are presented and illustrated by application. Software for application of these techniques has been installed on the signal processing system at the NASA/MSFC Systems Dynamics Laboratory.

Multi-Frequency Signal Detection Based on Frequency Exchange and Re-Scaling Stochastic Resonance and Its Application to Weak Fault Diagnosis.

PubMed

Liu, Jinjun; Leng, Yonggang; Lai, Zhihui; Fan, Shengbo

2018-04-25

Mechanical fault diagnosis usually requires not only identification of the fault characteristic frequency, but also detection of its second and/or higher harmonics. However, it is difficult to detect a multi-frequency fault signal through the existing Stochastic Resonance (SR) methods, because the characteristic frequency of the fault signal as well as its second and higher harmonics frequencies tend to be large parameters. To solve the problem, this paper proposes a multi-frequency signal detection method based on Frequency Exchange and Re-scaling Stochastic Resonance (FERSR). In the method, frequency exchange is implemented using filtering technique and Single SideBand (SSB) modulation. This new method can overcome the limitation of "sampling ratio" which is the ratio of the sampling frequency to the frequency of target signal. It also ensures that the multi-frequency target signals can be processed to meet the small-parameter conditions. Simulation results demonstrate that the method shows good performance for detecting a multi-frequency signal with low sampling ratio. Two practical cases are employed to further validate the effectiveness and applicability of this method.

Multi-Frequency Signal Detection Based on Frequency Exchange and Re-Scaling Stochastic Resonance and Its Application to Weak Fault Diagnosis

PubMed Central

Leng, Yonggang; Fan, Shengbo

2018-01-01

Mechanical fault diagnosis usually requires not only identification of the fault characteristic frequency, but also detection of its second and/or higher harmonics. However, it is difficult to detect a multi-frequency fault signal through the existing Stochastic Resonance (SR) methods, because the characteristic frequency of the fault signal as well as its second and higher harmonics frequencies tend to be large parameters. To solve the problem, this paper proposes a multi-frequency signal detection method based on Frequency Exchange and Re-scaling Stochastic Resonance (FERSR). In the method, frequency exchange is implemented using filtering technique and Single SideBand (SSB) modulation. This new method can overcome the limitation of "sampling ratio" which is the ratio of the sampling frequency to the frequency of target signal. It also ensures that the multi-frequency target signals can be processed to meet the small-parameter conditions. Simulation results demonstrate that the method shows good performance for detecting a multi-frequency signal with low sampling ratio. Two practical cases are employed to further validate the effectiveness and applicability of this method. PMID:29693577

Tunneling ionization and harmonic generation in two-color fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondo, K.; Kobayashi, Y.; Sagisaka, A.

1996-02-01

Tunneling ionization and harmonic generation in two-color fields were studied with a fundamental beam ({omega}) and its harmonics (2{omega},3{omega}), which were generated by a 100-fs Ti:sapphire laser. Ion yields of atoms and molecules were successfully controlled by means of a change in the relative phase between {omega} and 3{omega} pulses. Two-color interference was clearly observed in photoelectron spectra and harmonic spectra. In the {omega}{endash}2{omega} field even-order harmonics were observed in which the intensity was almost equal to that of the odd harmonics because of an asymmetric optical field. These results were compared with the quasi-static model for ionization and withmore » the quantum theory for harmonic generation. {copyright} {ital 1996 Optical Society of America.}« less

Attenuation of harmonic noise in vibroseis data using Simulated Annealing

NASA Astrophysics Data System (ADS)

Sharma, S. P.; Tildy, Peter; Iranpour, Kambiz; Scholtz, Peter

2009-04-01

Processing of high productivity vibroseis seismic data (such as slip-sweep acquisition records) suffers from the well known disadvantage of harmonic distortion. Harmonic distortions are observed after cross-correlation of the recorded seismic signal with the pilot sweep and affect the signals in negative time (before the actual strong reflection event). Weak reflection events of the earlier sweeps falling in the negative time window of the cross-correlation sequence are being masked by harmonic distortions. Though the amplitude of the harmonic distortion is small (up to 10-20 %) compared to the fundamental amplitude of the reflection events, but it is significant enough to mask weak reflected signals. Elimination of harmonic noise due to source signal distortion from the cross-correlated seismic trace is a challenging task since the application of vibratory sources started and it still needs improvement. An approach has been worked out that minimizes the level of harmonic distortion by designing the signal similar to the harmonic distortion. An arbitrary length filter is optimized using the Simulated Annealing global optimization approach to design a harmonic signal. The approach deals with the convolution of a ratio trace (ratio of the harmonics with respect to the fundamental sweep) with the correlated "positive time" recorded signal and an arbitrary filter. Synthetic data study has revealed that this procedure of designing a signal similar to the desired harmonics using convolution of a suitable filter with theoretical ratio of harmonics with fundamental sweep helps in reducing the problem of harmonic distortion. Once we generate a similar signal for a vibroseis source using an optimized filter, then, this filter could be used to generate harmonics, which can be subtracted from the main cross-correlated trace to get the better, undistorted image of the subsurface. Designing the predicted harmonics to reduce the energy in the trace by considering weak reflection

A Real-Time Earthquake Precursor Detection Technique Using TEC from a GPS Network

NASA Astrophysics Data System (ADS)

Alp Akyol, Ali; Arikan, Feza; Arikan, Orhan

2016-07-01

Anomalies have been observed in the ionospheric electron density distribution prior to strong earthquakes. However, most of the reported results are obtained by earthquake analysis. Therefore, their implementation in practice is highly problematic. Recently, a novel earthquake precursor detection technique based on spatio-temporal analysis of Total Electron Content (TEC) data obtained from Turkish National Permanent GPS Network (TNPGN) is developed by IONOLAB group (www.ionolab.org). In the present study, the developed detection technique is implemented in a causal setup over the available data set in test phase that enables the real time implementation. The performance of the developed earthquake prediction technique is evaluated by using 10 fold cross validation over the data obtained in 2011. Among the 23 earthquakes that have magnitudes higher than 5, the developed technique can detect precursors of 14 earthquakes while producing 8 false alarms. This study is supported by TUBITAK 115E915 and Joint TUBITAK 114E092 and AS CR 14/001 projects.

Thermographic techniques and adapted algorithms for automatic detection of foreign bodies in food

NASA Astrophysics Data System (ADS)

Meinlschmidt, Peter; Maergner, Volker

2003-04-01

At the moment foreign substances in food are detected mainly by using mechanical and optical methods as well as ultrasonic technique and than they are removed from the further process. These techniques detect a large portion of the foreign substances due to their different mass (mechanical sieving), their different colour (optical method) and their different surface density (ultrasonic detection). Despite the numerous different methods a considerable portion of the foreign substances remain undetected. In order to recognise materials still undetected, a complementary detection method would be desirable removing the foreign substances not registered by the a.m. methods from the production process. In a project with 13 partner from the food industry, the Fraunhofer - Institut für Holzforschung (WKI) and the Technische Unsiversität are trying to adapt thermography for the detection of foreign bodies in the food industry. After the initial tests turned out to be very promising for the differentiation of food stuffs and foreign substances, more and detailed investigation were carried out to develop suitable algorithms for automatic detection of foreign bodies. In order to achieve -besides the mere visual detection of foreign substances- also an automatic detection under production conditions, numerous experiences in image processing and pattern recognition are exploited. Results for the detection of foreign bodies will be presented at the conference showing the different advantages and disadvantages of using grey - level, statistical and morphological image processing techniques.

Performance assessment of HIFU lesion detection by Harmonic Motion Imaging for Focused Ultrasound (HMIFU): A 3D finite-element-based framework with experimental validation

PubMed Central

Hou, Gary Y.; Luo, Jianwen; Marquet, Fabrice; Maleke, Caroline; Vappou, Jonathan; Konofagou, Elisa E.

2014-01-01

Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a novel high-intensity focused ultrasound (HIFU) therapy monitoring method with feasibilities demonstrated in vitro, ex vivo and in vivo. Its principle is based on Amplitude-modulated (AM) - Harmonic Motion Imaging (HMI), an oscillatory radiation force used for imaging the tissue mechanical response during thermal ablation. In this study, a theoretical framework of HMIFU is presented, comprising a customized nonlinear wave propagation model, a finite-element (FE) analysis module, and an image-formation model. The objective of this study is to develop such a framework in order to 1) assess the fundamental performance of HMIFU in detecting HIFU lesions based on the change in tissue apparent elasticity, i.e., the increasing Young's modulus, and the HIFU lesion size with respect to the HIFU exposure time and 2) validate the simulation findings ex vivo. The same HMI and HMIFU parameters as in the experimental studies were used, i.e., 4.5-MHz HIFU frequency and 25 Hz AM frequency. For a lesion-to-background Young's modulus ratio of 3, 6, and 9, the FE and estimated HMI displacement ratios were equal to 1.83, 3.69, 5.39 and 1.65, 3.19, 4.59, respectively. In experiments, the HMI displacement followed a similar increasing trend of 1.19, 1.28, and 1.78 at 10-s, 20-s, and 30-s HIFU exposure, respectively. In addition, moderate agreement in lesion size growth was also found in both simulations (16.2, 73.1 and 334.7 mm2) and experiments (26.2, 94.2 and 206.2 mm2). Therefore, the feasibility of HMIFU for HIFU lesion detection based on the underlying tissue elasticity changes was verified through the developed theoretical framework, i.e., validation of the fundamental performance of the HMIFU system for lesion detection, localization and quantification, was demonstrated both theoretically and ex vivo. PMID:22036637

Performance assessment of HIFU lesion detection by harmonic motion imaging for focused ultrasound (HMIFU): a 3-D finite-element-based framework with experimental validation.

PubMed

Hou, Gary Y; Luo, Jianwen; Marquet, Fabrice; Maleke, Caroline; Vappou, Jonathan; Konofagou, Elisa E

2011-12-01

Harmonic motion imaging for focused ultrasound (HMIFU) is a novel high-intensity focused ultrasound (HIFU) therapy monitoring method with feasibilities demonstrated in vitro, ex vivo and in vivo. Its principle is based on amplitude-modulated (AM) - harmonic motion imaging (HMI), an oscillatory radiation force used for imaging the tissue mechanical response during thermal ablation. In this study, a theoretical framework of HMIFU is presented, comprising a customized nonlinear wave propagation model, a finite-element (FE) analysis module and an image-formation model. The objective of this study is to develop such a framework to (1) assess the fundamental performance of HMIFU in detecting HIFU lesions based on the change in tissue apparent elasticity, i.e., the increasing Young's modulus, and the HIFU lesion size with respect to the HIFU exposure time and (2) validate the simulation findings ex vivo. The same HMI and HMIFU parameters as in the experimental studies were used, i.e., 4.5-MHz HIFU frequency and 25 Hz AM frequency. For a lesion-to-background Young's modulus ratio of 3, 6 and 9, the FE and estimated HMI displacement ratios were equal to 1.83, 3.69 and 5.39 and 1.65, 3.19 and 4.59, respectively. In experiments, the HMI displacement followed a similar increasing trend of 1.19, 1.28 and 1.78 at 10-s, 20-s and 30-s HIFU exposure, respectively. In addition, moderate agreement in lesion size growth was found in both simulations (16.2, 73.1 and 334.7 mm(2)) and experiments (26.2, 94.2 and 206.2 mm(2)). Therefore, the feasibility of HMIFU for HIFU lesion detection based on the underlying tissue elasticity changes was verified through the developed theoretical framework, i.e., validation of the fundamental performance of the HMIFU system for lesion detection, localization and quantification, was demonstrated both theoretically and ex vivo. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Harmonic oscillator states in aberration optics

NASA Technical Reports Server (NTRS)

Wolf, Kurt Bernardo

1993-01-01

The states of the three-dimensional quantum harmonic oscillator classify optical aberrations of axis-symmetric systems due to the isomorphism between the two mathematical structures. Cartesian quanta and angular momentum classifications have their corresponding aberration classifications. The operation of concatenation of optical elements introduces a new operation between harmonic oscillator states.

Second Harmonic Imaging improves Echocardiograph Quality on board the International Space Station

NASA Technical Reports Server (NTRS)

Garcia, Kathleen; Sargsyan, Ashot; Hamilton, Douglas; Martin, David; Ebert, Douglas; Melton, Shannon; Dulchavsky, Scott

2008-01-01

Ultrasound (US) capabilities have been part of the Human Research Facility (HRF) on board the International Space Station (ISS) since 2001. The US equipment on board the ISS includes a first-generation Tissue Harmonic Imaging (THI) option. Harmonic imaging (HI) is the second harmonic response of the tissue to the ultrasound beam and produces robust tissue detail and signal. Since this is a first-generation THI, there are inherent limitations in tissue penetration. As a breakthrough technology, HI extensively advanced the field of ultrasound. In cardiac applications, it drastically improves endocardial border detection and has become a common imaging modality. U.S. images were captured and stored as JPEG stills from the ISS video downlink. US images with and without harmonic imaging option were randomized and provided to volunteers without medical education or US skills for identification of endocardial border. The results were processed and analyzed using applicable statistical calculations. The measurements in US images using HI improved measurement consistency and reproducibility among observers when compared to fundamental imaging. HI has been embraced by the imaging community at large as it improves the quality and data validity of US studies, especially in difficult-to-image cases. Even with the limitations of the first generation THI, HI improved the quality and measurability of many of the downlinked images from the ISS and should be an option utilized with cardiac imaging on board the ISS in all future space missions.

Solid-state harmonics beyond the atomic limit.

PubMed

Ndabashimiye, Georges; Ghimire, Shambhu; Wu, Mengxi; Browne, Dana A; Schafer, Kenneth J; Gaarde, Mette B; Reis, David A

2016-06-23

Strong-field laser excitation of solids can produce extremely nonlinear electronic and optical behaviour. As recently demonstrated, this includes the generation of high harmonics extending into the vacuum-ultraviolet and extreme-ultraviolet regions of the electromagnetic spectrum. High harmonic generation is shown to occur fundamentally differently in solids and in dilute atomic gases. How the microscopic mechanisms in the solid and the gas differ remains a topic of intense debate. Here we report a direct comparison of high harmonic generation in the solid and gas phases of argon and krypton. Owing to the weak van der Waals interaction, rare (noble)-gas solids are a near-ideal medium in which to study the role of high density and periodicity in the generation process. We find that the high harmonic generation spectra from the rare-gas solids exhibit multiple plateaus extending well beyond the atomic limit of the corresponding gas-phase harmonics measured under similar conditions. The appearance of multiple plateaus indicates strong interband couplings involving multiple single-particle bands. We also compare the dependence of the solid and gas harmonic yield on laser ellipticity and find that they are similar, suggesting the importance of electron-hole recollision in these solids. This implies that gas-phase methods such as polarization gating for attosecond pulse generation and orbital tomography could be realized in solids.

Geometrical Theory of Spherical Harmonics for Geosciences

NASA Astrophysics Data System (ADS)

Svehla, Drazen

2010-05-01

Spherical harmonics play a central role in the modelling of spatial and temporal processes in the system Earth. The gravity field of the Earth and its temporal variations, sea surface topography, geomagnetic field, ionosphere etc., are just a few examples where spherical harmonics are used to represent processes in the system Earth. We introduce a novel method for the computation and rotation of spherical harmonics, Legendre polynomials and associated Legendre functions without making use of recursive relations. This novel geometrical approach allows calculation of spherical harmonics without any numerical instability up to an arbitrary degree and order, e.g. up to degree and order 106 and beyond. The algorithm is based on the trigonometric reduction of Legendre polynomials and the geometric rotation in hyperspace. It is shown that Legendre polynomials can be computed using trigonometric series by pre-computing amplitudes and translation terms for all angular arguments. It is shown that they can be treated as vectors in the Hilbert hyperspace leading to unitary hermitian rotation matrices with geometric properties. Thus, rotation of spherical harmonics about e.g. a polar or an equatorial axis can be represented in the similar way. This novel method allows stable calculation of spherical harmonics up to an arbitrary degree and order, i.e. up to degree and order 106 and beyond.

Determination of nonlinear resistance voltage-current relationships by measuring harmonics

NASA Technical Reports Server (NTRS)

Stafford, J. M.

1971-01-01

Test configuration measures harmonic signal amplitudes generated in nonlinear resistance. Vacuum-type voltmeter measures low frequency sinusoidal input signal amplitude and wave-analyzer measures amplitude of harmonic signals generated in junction. Input signal harmonics amplitude must not exceed that of harmonics generated in nonlinear resistance.

Predicting chaos in memristive oscillator via harmonic balance method.

PubMed

Wang, Xin; Li, Chuandong; Huang, Tingwen; Duan, Shukai

2012-12-01

This paper studies the possible chaotic behaviors in a memristive oscillator with cubic nonlinearities via harmonic balance method which is also called the method of describing function. This method was proposed to detect chaos in classical Chua's circuit. We first transform the considered memristive oscillator system into Lur'e model and present the prediction of the existence of chaotic behaviors. To ensure the prediction result is correct, the distortion index is also measured. Numerical simulations are presented to show the effectiveness of theoretical results.

Background field removal technique using regularization enabled sophisticated harmonic artifact reduction for phase data with varying kernel sizes.

PubMed

Kan, Hirohito; Kasai, Harumasa; Arai, Nobuyuki; Kunitomo, Hiroshi; Hirose, Yasujiro; Shibamoto, Yuta

2016-09-01

An effective background field removal technique is desired for more accurate quantitative susceptibility mapping (QSM) prior to dipole inversion. The aim of this study was to evaluate the accuracy of regularization enabled sophisticated harmonic artifact reduction for phase data with varying spherical kernel sizes (REV-SHARP) method using a three-dimensional head phantom and human brain data. The proposed REV-SHARP method used the spherical mean value operation and Tikhonov regularization in the deconvolution process, with varying 2-14mm kernel sizes. The kernel sizes were gradually reduced, similar to the SHARP with varying spherical kernel (VSHARP) method. We determined the relative errors and relationships between the true local field and estimated local field in REV-SHARP, VSHARP, projection onto dipole fields (PDF), and regularization enabled SHARP (RESHARP). Human experiment was also conducted using REV-SHARP, VSHARP, PDF, and RESHARP. The relative errors in the numerical phantom study were 0.386, 0.448, 0.838, and 0.452 for REV-SHARP, VSHARP, PDF, and RESHARP. REV-SHARP result exhibited the highest correlation between the true local field and estimated local field. The linear regression slopes were 1.005, 1.124, 0.988, and 0.536 for REV-SHARP, VSHARP, PDF, and RESHARP in regions of interest on the three-dimensional head phantom. In human experiments, no obvious errors due to artifacts were present in REV-SHARP. The proposed REV-SHARP is a new method combined with variable spherical kernel size and Tikhonov regularization. This technique might make it possible to be more accurate backgroud field removal and help to achive better accuracy of QSM. Copyright © 2016 Elsevier Inc. All rights reserved.

Temperature, stress, and corrosive sensing apparatus utilizing harmonic response of magnetically soft sensor element (s)

NASA Technical Reports Server (NTRS)

Grimes, Craig A. (Inventor); Ong, Keat Ghee (Inventor)

2003-01-01

A temperature sensing apparatus including a sensor element made of a magnetically soft material operatively arranged within a first and second time-varying interrogation magnetic field, the first time-varying magnetic field being generated at a frequency higher than that for the second magnetic field. A receiver, remote from the sensor element, is engaged to measure intensity of electromagnetic emissions from the sensor element to identify a relative maximum amplitude value for each of a plurality of higher-order harmonic frequency amplitudes so measured. A unit then determines a value for temperature (or other parameter of interst) using the relative maximum harmonic amplitude values identified. In other aspects of the invention, the focus is on an apparatus and technique for determining a value for of stress condition of a solid analyte and for determining a value for corrosion, using the relative maximum harmonic amplitude values identified. A magnetically hard element supporting a biasing field adjacent the magnetically soft sensor element can be included.

Wavelet Transform Based Filter to Remove the Notches from Signal Under Harmonic Polluted Environment

NASA Astrophysics Data System (ADS)

Das, Sukanta; Ranjan, Vikash

2017-12-01

The work proposes to annihilate the notches present in the synchronizing signal required for converter operation appearing due to switching of semiconductor devices connected to the system in the harmonic polluted environment. The disturbances in the signal are suppressed by wavelet based novel filtering technique. In the proposed technique, the notches in the signal are determined and eliminated by the wavelet based multi-rate filter using `Daubechies4' (db4) as mother wavelet. The computational complexity of the adapted technique is very less as compared to any other conventional notch filtering techniques. The proposed technique is developed in MATLAB/Simulink and finally validated with dSPACE-1103 interface. The recovered signal, thus obtained, is almost free of the notches.

Multi-Orbital contributions in High Harmonic Generation

NASA Astrophysics Data System (ADS)

Guehr, Markus

2009-05-01

The high harmonic spectrum generated from atoms or molecules in a strong laser field contains information about the electronic structure of the generation medium. In the high harmonic generation (HHG) process, a free electron wave packet tunnel-ionizes from the molecular orbital in a strong laser field. After being accelerated by the laser electric field, the free electron wave packet coherently recombines to the orbital from which is was initially ionized, thereby emitting the harmonic spectrum. Interferences between the free electron wave packet and the molecular orbital will shape the spectrum in a characteristic way. These interferences have been used to tomographically image the highest occupied molecular orbital (HOMO) of N2 [1]. Molecular electronic states energetically below the HOMO should contribute to laser-driven high harmonic generation (HHG), but this behavior has not been observed previously. We have observed evidence of HHG from multiple orbitals in aligned N2 [2]. The tunneling ionization (and therefore the harmonic generation) is most efficient if the orbital has a large extension in the direction of the harmonic generation polarization. The HOMO with its σg symmetry therefore dominates the harmonic spectrum if the molecular axis is parallel to the harmonic generation polarization, the lower bound πu HOMO-1 dominates in the perpendicular case. The HOMO contributions appear as a regular plateau with a cutoff in the HHG spectrum. In contrast, the HOMO-1 signal is strongly peaked in the cutoff region. We explain this by semi-classical simulations of the recombination process that show constructive interferences between the HOMO-1 and the recombining wave packet in the cutoff region. The ability to monitor several orbitals opens the route to imaging coherent superpositions of electronic orbitals. [1] J. Itatani et al., Nature 432, 867 (2004)[2] B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. Gühr, Science 322, 1232 (2008)

Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method.

PubMed

Sun, Weifang; Yao, Bin; He, Yuchao; Chen, Binqiang; Zeng, Nianyin; He, Wangpeng

2017-08-09

Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages.

Health State Monitoring of Bladed Machinery with Crack Growth Detection in BFG Power Plant Using an Active Frequency Shift Spectral Correction Method

PubMed Central

Sun, Weifang; Yao, Bin; He, Yuchao; Zeng, Nianyin; He, Wangpeng

2017-01-01

Power generation using waste-gas is an effective and green way to reduce the emission of the harmful blast furnace gas (BFG) in pig-iron producing industry. Condition monitoring of mechanical structures in the BFG power plant is of vital importance to guarantee their safety and efficient operations. In this paper, we describe the detection of crack growth of bladed machinery in the BFG power plant via vibration measurement combined with an enhanced spectral correction technique. This technique enables high-precision identification of amplitude, frequency, and phase information (the harmonic information) belonging to deterministic harmonic components within the vibration signals. Rather than deriving all harmonic information using neighboring spectral bins in the fast Fourier transform spectrum, this proposed active frequency shift spectral correction method makes use of some interpolated Fourier spectral bins and has a better noise-resisting capacity. We demonstrate that the identified harmonic information via the proposed method is of suppressed numerical error when the same level of noises is presented in the vibration signal, even in comparison with a Hanning-window-based correction method. With the proposed method, we investigated vibration signals collected from a centrifugal compressor. Spectral information of harmonic tones, related to the fundamental working frequency of the centrifugal compressor, is corrected. The extracted spectral information indicates the ongoing development of an impeller blade crack that occurred in the centrifugal compressor. This method proves to be a promising alternative to identify blade cracks at early stages. PMID:28792453

Remote listening and passive acoustic detection in a 3-D environment

NASA Astrophysics Data System (ADS)

Barnhill, Colin

Teleconferencing environments are a necessity in business, education and personal communication. They allow for the communication of information to remote locations without the need for travel and the necessary time and expense required for that travel. Visual information can be communicated using cameras and monitors. The advantage of visual communication is that an image can capture multiple objects and convey them, using a monitor, to a large group of people regardless of the receiver's location. This is not the case for audio. Currently, most experimental teleconferencing systems' audio is based on stereo recording and reproduction techniques. The problem with this solution is that it is only effective for one or two receivers. To accurately capture a sound environment consisting of multiple sources and to recreate that for a group of people is an unsolved problem. This work will focus on new methods of multiple source 3-D environment sound capture and applications using these captured environments. Using spherical microphone arrays, it is now possible to capture a true 3-D environment A spherical harmonic transform on the array's surface allows us to determine the basis functions (spherical harmonics) for all spherical wave solutions (up to a fixed order). This spherical harmonic decomposition (SHD) allows us to not only look at the time and frequency characteristics of an audio signal but also the spatial characteristics of an audio signal. In this way, a spherical harmonic transform is analogous to a Fourier transform in that a Fourier transform transforms a signal into the frequency domain and a spherical harmonic transform transforms a signal into the spatial domain. The SHD also decouples the input signals from the microphone locations. Using the SHD of a soundfield, new algorithms are available for remote listening, acoustic detection, and signal enhancement The new algorithms presented in this paper show distinct advantages over previous detection and

Multisite EPR oximetry from multiple quadrature harmonics.

PubMed

Ahmad, R; Som, S; Johnson, D H; Zweier, J L; Kuppusamy, P; Potter, L C

2012-01-01

Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported. Copyright © 2011 Elsevier Inc. All rights reserved.

Dispersion tuning in sub-micron tapers for third-harmonic and photon triplet generation.

PubMed

Hammer, Jonas; Cavanna, Andrea; Pennetta, Riccardo; Chekhova, Maria V; Russell, Philip St J; Joly, Nicolas Y

2018-05-15

Precise control of the dispersion landscape is of crucial importance if optical fibers are to be successfully used for the generation of three-photon states of light-the inverse of third-harmonic generation (THG). Here we report gas-tuning of intermodal phase-matched THG in sub-micron-diameter tapered optical fiber. By adjusting the pressure of the surrounding argon gas up to 50 bars, intermodally phase-matched third-harmonic light can be generated for pump wavelengths within a 15 nm range around 1.38 μm. We also measure the infrared fluorescence generated in the fiber when pumped in the visible and estimate that the accidental coincidence rate in this signal is lower than the predicted detection rate of photon triplets.

Laser heterodyne detection techniques. [for atmospheric monitoring applications

NASA Technical Reports Server (NTRS)

Menzies, R. T.

1976-01-01

The principles of heterodyne radiometry are examined, taking into account thermal radiation, the Dicke microwave radiometer, photomixing in the infrared, and signal-to-noise considerations. The passive heterodyne radiometer is considered and a description is presented of heterodyne techniques in active monitoring systems. Attention is given to gas emissivities in the infrared, component requirements, experimental heterodyne detection of gases, a comparison of the passive heterodyne radiometer with the Michelson interferometer-spectrometer, airborne monitoring applications, turbulence effects on passive heterodyne radiometry, sensitivity improvements with heterodyning, atmosphere-induced degradation of bistatic system performance, pollutant detection experiments with a bistatic system, and the airborne laser absorption spectrometer. Future improvements in spectral flexibility are also discussed.

Harmonic lasing in x-ray free electron lasers

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2012-08-01

Harmonic lasing in a free electron laser with a planar undulator (under the condition that the fundamental frequency is suppressed) might be a cheap and efficient way of extension of wavelength ranges of existing and planned x-ray free electron laser (FEL) facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental frequency. In this paper we perform a parametrization of the solution of the eigenvalue equation for lasing at odd harmonics, and present an explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental harmonic. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of x-ray beam at saturation. Considering 3rd harmonic lasing as a practical example, we come to the conclusion that it is much more robust than usually thought, and can be widely used in the existing or planned x-ray FEL (XFEL) facilities. In particular, Linac Coherent Light Source (LCLS) after a minor modification can lase to saturation at the 3rd harmonic up to the photon energy of 25-30 keV providing multigigawatt power level and narrow bandwidth. As for the European XFEL, harmonic lasing would allow one to extend operating range (ultimately up to 100 keV), to reduce FEL bandwidth and to increase brilliance, to enable two-color operation for pump-probe experiments, and to provide more flexible operation at different electron energies. Similar improvements can be realized in other x-ray FEL facilities with gap-tunable undulators like FLASH II, SACLA, LCLS II, etc. Harmonic lasing can be an attractive option for compact x-ray FELs (driven by electron beams with a relatively low energy), allowing the use of the standard undulator technology instead of small-gap in

Parallel transmit beamforming using orthogonal frequency division multiplexing applied to harmonic imaging--a feasibility study.

PubMed

Demi, Libertario; Verweij, Martin D; Van Dongen, Koen W A

2012-11-01

Real-time 2-D or 3-D ultrasound imaging systems are currently used for medical diagnosis. To achieve the required data acquisition rate, these systems rely on parallel beamforming, i.e., a single wide-angled beam is used for transmission and several narrow parallel beams are used for reception. When applied to harmonic imaging, the demand for high-amplitude pressure wave fields, necessary to generate the harmonic components, conflicts with the use of a wide-angled beam in transmission because this results in a large spatial decay of the acoustic pressure. To enhance the amplitude of the harmonics, it is preferable to do the reverse: transmit several narrow parallel beams and use a wide-angled beam in reception. Here, this concept is investigated to determine whether it can be used for harmonic imaging. The method proposed in this paper relies on orthogonal frequency division multiplexing (OFDM), which is used to create distinctive parallel beams in transmission. To test the proposed method, a numerical study has been performed, in which the transmit, receive, and combined beam profiles generated by a linear array have been simulated for the second-harmonic component. Compared with standard parallel beamforming, application of the proposed technique results in a gain of 12 dB for the main beam and in a reduction of the side lobes. Experimental verification in water has also been performed. Measurements obtained with a single-element emitting transducer and a hydrophone receiver confirm the possibility of exciting a practical ultrasound transducer with multiple Gaussian modulated pulses, each having a different center frequency, and the capability to generate distinguishable second-harmonic components.

Detection of cracks beneath rivet heads via pulsed eddy current technique

NASA Astrophysics Data System (ADS)

Giguère, J. S. R.; Lepine, B. A.; Dubois, J. M. S.

2002-05-01

Improving the detectability of fatigue cracks under installed fasteners is one of the many goals of the aging aircraft nondestructive evaluation (NDE) community. The pulsed eddy current offers new capabilities to address this requirement. The aim of the paper is to evaluate the potential of this technique for detecting and quantifying notches under installed fasteners.

Hyperbolic Harmonic Mapping for Surface Registration

PubMed Central

Shi, Rui; Zeng, Wei; Su, Zhengyu; Jiang, Jian; Damasio, Hanna; Lu, Zhonglin; Wang, Yalin; Yau, Shing-Tung; Gu, Xianfeng

2016-01-01

Automatic computation of surface correspondence via harmonic map is an active research field in computer vision, computer graphics and computational geometry. It may help document and understand physical and biological phenomena and also has broad applications in biometrics, medical imaging and motion capture inducstries. Although numerous studies have been devoted to harmonic map research, limited progress has been made to compute a diffeomorphic harmonic map on general topology surfaces with landmark constraints. This work conquers this problem by changing the Riemannian metric on the target surface to a hyperbolic metric so that the harmonic mapping is guaranteed to be a diffeomorphism under landmark constraints. The computational algorithms are based on Ricci flow and nonlinear heat diffusion methods. The approach is general and robust. We employ our algorithm to study the constrained surface registration problem which applies to both computer vision and medical imaging applications. Experimental results demonstrate that, by changing the Riemannian metric, the registrations are always diffeomorphic and achieve relatively high performance when evaluated with some popular surface registration evaluation standards. PMID:27187948

Degradation in finite-harmonic subcarrier demodulation

NASA Technical Reports Server (NTRS)

Feria, Y.; Townes, S.; Pham, T.

1995-01-01

Previous estimates on the degradations due to a subcarrier loop assume a square-wave subcarrier. This article provides a closed-form expression for the degradations due to the subcarrier loop when a finite number of harmonics are used to demodulate the subcarrier, as in the case of the buffered telemetry demodulator. We compared the degradations using a square wave and using finite harmonics in the subcarrier demodulation and found that, for a low loop signal-to-noise ratio, using finite harmonics leads to a lower degradation. The analysis is under the assumption that the phase noise in the subcarrier (SC) loop has a Tikhonov distribution. This assumption is valid for first-order loops.

Resonance ultrasonic vibrations in Cz-Si wafers as a possible diagnostic technique in ion implantation

NASA Astrophysics Data System (ADS)

Zhao, Z. Y.; Ostapenko, S.; Anundson, R.; Tvinnereim, M.; Belyaev, A.; Anthony, M.

2001-07-01

The semiconductor industry does not have effective metrology for well implants. The ability to measure such deep level implants will become increasingly important as we progress along the technology road map. This work explores the possibility of using the acoustic whistle effect on ion implanted silicon wafers. The technique detects the elastic stress and defects in silicon wafers by measuring the sub-harmonic f/2 resonant vibrations on a wafer induced via backside contact to create standing waves, which are measured by a non-contact ultrasonic probe. Preliminary data demonstrates that it is sensitive to implant damage, and there is a direct correlation between this sub-harmonic acoustic mode and some of the implant and anneal conditions. This work presents the results of a feasibility study to assess and quantify the correspondent whistle effect to implant damage, residual damage after annealing and intrinsic defects.

Automated Land Cover Change Detection and Mapping from Hidden Parameter Estimates of Normalized Difference Vegetation Index (NDVI) Time-Series

NASA Astrophysics Data System (ADS)

Chakraborty, S.; Banerjee, A.; Gupta, S. K. S.; Christensen, P. R.; Papandreou-Suppappola, A.

2017-12-01

Multitemporal observations acquired frequently by satellites with short revisit periods such as the Moderate Resolution Imaging Spectroradiometer (MODIS), is an important source for modeling land cover. Due to the inherent seasonality of the land cover, harmonic modeling reveals hidden state parameters characteristic to it, which is used in classifying different land cover types and in detecting changes due to natural or anthropogenic factors. In this work, we use an eight day MODIS composite to create a Normalized Difference Vegetation Index (NDVI) time-series of ten years. Improved hidden parameter estimates of the nonlinear harmonic NDVI model are obtained using the Particle Filter (PF), a sequential Monte Carlo estimator. The nonlinear estimation based on PF is shown to improve parameter estimation for different land cover types compared to existing techniques that use the Extended Kalman Filter (EKF), due to linearization of the harmonic model. As these parameters are representative of a given land cover, its applicability in near real-time detection of land cover change is also studied by formulating a metric that captures parameter deviation due to change. The detection methodology is evaluated by considering change as a rare class problem. This approach is shown to detect change with minimum delay. Additionally, the degree of change within the change perimeter is non-uniform. By clustering the deviation in parameters due to change, this spatial variation in change severity is effectively mapped and validated with high spatial resolution change maps of the given regions.

Focused Ultrasound Steering for Harmonic Motion Imaging.

PubMed

Han, Yang; Payen, Thomas; Wang, Shutao; Konofagou, Elisa

2018-02-01

Harmonic motion imaging (HMI) is a radiation-force-based ultrasound elasticity imaging technique, which is designed for both tissue relative stiffness imaging and reliable high-intensity focused ultrasound treatment monitoring. The objective of this letter is to develop and demonstrate the feasibility of 2-D focused ultrasound (FUS) beam steering for HMI using a 93-element, FUS phased array. HMI with steered FUS beam was acquired in tissue-mimicking phantoms. The HMI displacement was imaged within the steering range of ±1.7 mm laterally and ±2 mm axially. Using the steered FUS beam, HMI can be used to image a larger tissue volume with higher efficiency and without requiring mechanical movement of the transducer.

Study of third order nonlinearity of chalcogenide thin films using third harmonic generation measurements

NASA Astrophysics Data System (ADS)

Rani, Sunita; Mohan, Devendra; Kumar, Manish; Sanjay

2018-05-01

Third order nonlinear susceptibility of (GeSe3.5)100-xBix (x = 0, 10, 14) and ZnxSySe100-x-y (x = 2, y = 28; x = 4, y = 20; x = 6, y = 12; x = 8, y = 4) amorphous chalcogenide thin films prepared using thermal evaporation technique is estimated. The dielectric constant at incident and third harmonic wavelength is calculated using "PARAV" computer program. 1064 nm wavelength of Nd: YAG laser is incident on thin film and third harmonic signal at 355 nm wavelength alongwith fundamental light is obtained in reflection that is separated from 1064 nm using suitable optical filter. Reflected third harmonic signal is measured to trace the influence of Bi and Zn on third order nonlinear susceptibility and is found to increase with increase in Bi and Zn content in (GeSe3.5)100-xBix, and ZnxSySe100-x-y chalcogenide thin films respectively. The excellent optical nonlinear property shows the use of chalcogenide thin films in photonics for wavelength conversion and optical data processing.

Higher Harmonics in Heavy Ion Collisions

NASA Astrophysics Data System (ADS)

Jeon, Sangyong

2013-03-01

As the QGP expands and cools, it carries much information on its creation and evolution imprinted on the patterns of higher harmonic flow. In this proceeding we report on the progress in simulating and understanding the higher harmonics by the McGill group using the 3+1D event-by-event viscous hydrodynamics simulation suite named MUSIC.

Sunspots and Their Simple Harmonic Motion

ERIC Educational Resources Information Center

Ribeiro, C. I.

2013-01-01

In this paper an example of a simple harmonic motion, the apparent motion of sunspots due to the Sun's rotation, is described, which can be used to teach this subject to high-school students. Using real images of the Sun, students can calculate the star's rotation period with the simple harmonic motion mathematical expression.

Promoting clinical and laboratory interaction by harmonization.

PubMed

Plebani, Mario; Panteghini, Mauro

2014-05-15

The lack of interchangeable results in current practice among clinical laboratories has underpinned greater attention to standardization and harmonization projects. Although the focus was mainly on the standardization and harmonization of measurement procedures and their results, the scope of harmonization goes beyond method and analytical results: it includes all other aspects of laboratory testing, including terminology and units, report formats, reference limits and decision thresholds, as well as test profiles and criteria for the interpretation of results. In particular, as evidence collected in last decades demonstrates that pre-pre- and post-post-analytical steps are more vulnerable to errors, harmonization initiatives should be performed to improve procedures and processes at the laboratory-clinical interface. Managing upstream demand, down-stream interpretation of laboratory results, and subsequent appropriate action through close relationships between laboratorians and clinicians remains a crucial issue of the laboratory testing process. Therefore, initiatives to improve test demand management from one hand and to harmonize procedures to improve physicians' acknowledgment of laboratory data and their interpretation from the other hand are needed in order to assure quality and safety in the total testing process. © 2013.

Evidence for Harmonic Content and Frequency Evolution of Oscillations During the Rising Phase of X-ray Bursts From 4U 1636-536

NASA Technical Reports Server (NTRS)

Bgattacharyya, Sudip; Strohmayer, E.

2005-01-01

We report on a study of the evolution of burst oscillation properties during the rising phase of X-ray bursts from 4U 1636-536 observed with the proportional counter array (PCA) on board the Rossi X-Ray Timing Explorer (RXTE) . We present evidence for significant harmonic structure of burst oscillation pulses during the early rising phases of bursts. This is the first such detection in burst rise oscillations, and is very important for constraining neutron star structure parameters and the equation of state models of matter at the core of a neutron star. The detection of harmonic content only during the initial portions of the burst rise is consistent with the theoretical expectation that with time the thermonuclear burning region becomes larger, and hence the fundamental and harmonic amplitudes both diminish. We also find, for the first time from this source, strong evidence of oscillation frequency increase during the burst rise. The timing behavior of harmonic content, amplitude, and frequency of burst rise oscillations may be important in understanding the spreading of thermonuclear flames under the extreme physical conditions on neutron star surfaces.

A leakage-free resonance sparse decomposition technique for bearing fault detection in gearboxes

NASA Astrophysics Data System (ADS)

Osman, Shazali; Wang, Wilson

2018-03-01

Most of rotating machinery deficiencies are related to defects in rolling element bearings. Reliable bearing fault detection still remains a challenging task, especially for bearings in gearboxes as bearing-defect-related features are nonstationary and modulated by gear mesh vibration. A new leakage-free resonance sparse decomposition (LRSD) technique is proposed in this paper for early bearing fault detection of gearboxes. In the proposed LRSD technique, a leakage-free filter is suggested to remove strong gear mesh and shaft running signatures. A kurtosis and cosine distance measure is suggested to select appropriate redundancy r and quality factor Q. The signal residual is processed by signal sparse decomposition for highpass and lowpass resonance analysis to extract representative features for bearing fault detection. The effectiveness of the proposed technique is verified by a succession of experimental tests corresponding to different gearbox and bearing conditions.

Lenore White Harmon: One Woman's Career Development.

ERIC Educational Resources Information Center

Fouad, Nadya A.

1997-01-01

Presents biographical information on Lenore White Harmon, noted professor, counselor, and researcher. In a question-and-answer section, Harmon describes her early career decisions, work history, research efforts, professional contributions, important influences and reflections on her career development. (KW)

Harmonic arbitrary waveform generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, Brock Franklin

2017-11-28

High frequency arbitrary waveforms have applications in radar, communications, medical imaging, therapy, electronic warfare, and charged particle acceleration and control. State of the art arbitrary waveform generators are limited in the frequency they can operate by the speed of the Digital to Analog converters that directly create their arbitrary waveforms. The architecture of the Harmonic Arbitrary Waveform Generator allows the phase and amplitude of the high frequency content of waveforms to be controlled without taxing the Digital to Analog converters that control them. The Harmonic Arbitrary Waveform Generator converts a high frequency input, into a precision, adjustable, high frequency arbitrarymore » waveform.« less

Statistical Techniques For Real-time Anomaly Detection Using Spark Over Multi-source VMware Performance Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solaimani, Mohiuddin; Iftekhar, Mohammed; Khan, Latifur

Anomaly detection refers to the identi cation of an irregular or unusual pat- tern which deviates from what is standard, normal, or expected. Such deviated patterns typically correspond to samples of interest and are assigned different labels in different domains, such as outliers, anomalies, exceptions, or malware. Detecting anomalies in fast, voluminous streams of data is a formidable chal- lenge. This paper presents a novel, generic, real-time distributed anomaly detection framework for heterogeneous streaming data where anomalies appear as a group. We have developed a distributed statistical approach to build a model and later use it to detect anomaly. Asmore » a case study, we investigate group anomaly de- tection for a VMware-based cloud data center, which maintains a large number of virtual machines (VMs). We have built our framework using Apache Spark to get higher throughput and lower data processing time on streaming data. We have developed a window-based statistical anomaly detection technique to detect anomalies that appear sporadically. We then relaxed this constraint with higher accuracy by implementing a cluster-based technique to detect sporadic and continuous anomalies. We conclude that our cluster-based technique out- performs other statistical techniques with higher accuracy and lower processing time.« less

Detection of irradiated spices using photo-stimulated luminescence technique (PSL)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi; Othman, Zainon

2014-09-03

Photo-stimulated luminescence (PSL) technique was applied to detect irradiated black pepper (Piper nigrum), cinnamon (Cinnamomum verum) and turmeric (Curcuma longa) after dark storage for 1 day, 3 and 6 months. Using screening and calibrated PSL, all samples were correctly discriminated between non-irradiated and spices irradiated with doses 1, 5 and 10 kGy. The PSL photon counts (PCs) of irradiated spices increased with increasing dose, with turmeric showing highest sensitivity index to irradiation compared to black pepper and cinnamon. The differences in response are possibly attributed to the varying quantity and quality of silicate minerals present in each spice sample. PSLmore » signals of all irradiated samples reduced after 3 and 6 months storage. The results of this study provide a useful database on the applicability of PSL technique for the detection of Malaysian irradiated spices.« less

Detection of irradiated spices using photo-stimulated luminescence technique (PSL)

NASA Astrophysics Data System (ADS)

Ramli, Ros Anita Ahmad; Yasir, Muhamad Samudi; Othman, Zainon; Abdullah, Wan Saffiey Wan

2014-09-01

Photo-stimulated luminescence (PSL) technique was applied to detect irradiated black pepper (Piper nigrum), cinnamon (Cinnamomum verum) and turmeric (Curcuma longa) after dark storage for 1 day, 3 and 6 months. Using screening and calibrated PSL, all samples were correctly discriminated between non-irradiated and spices irradiated with doses 1, 5 and 10 kGy. The PSL photon counts (PCs) of irradiated spices increased with increasing dose, with turmeric showing highest sensitivity index to irradiation compared to black pepper and cinnamon. The differences in response are possibly attributed to the varying quantity and quality of silicate minerals present in each spice sample. PSL signals of all irradiated samples reduced after 3 and 6 months storage. The results of this study provide a useful database on the applicability of PSL technique for the detection of Malaysian irradiated spices.

Data harmonization of environmental variables: from simple to general solutions

NASA Astrophysics Data System (ADS)

Baume, O.

2009-04-01

been active for all member states for more than a decade (de Cort and de Vries, 1997). This database contains biases because of the different networks processes used in data reporting (Bossew et al., 2007). In a comparison study, monthly averaged Gamma dose measurements from eight European countries were using the methods described above. Baume et al. (2008) showed that both methods yield similar results and can detect and remove bias from the EURDEP database. To broaden the potential of the methods developed within the INTAMAP project, another application example taken from soil science is presented in this paper. The Carbon/Nitrogen (C/N) ratio of forest soils is one of the best predictors for evaluating soil functions such as used in climate change issues. Although soil samples were analyzed according to a common European laboratory method, Carré et al. (2008) concluded that systematic errors are introduced in the measurements due to calibration issues and instability of the sample. The application of the harmonization procedures showed that bias could be adequately removed, although the procedures have difficulty to distinguish real differences from bias.

Polarization-Resolved Study of High Harmonics from Bulk Semiconductors

NASA Astrophysics Data System (ADS)

Kaneshima, Keisuke; Shinohara, Yasushi; Takeuchi, Kengo; Ishii, Nobuhisa; Imasaka, Kotaro; Kaji, Tomohiro; Ashihara, Satoshi; Ishikawa, Kenichi L.; Itatani, Jiro

2018-06-01

The polarization property of high harmonics from gallium selenide is investigated using linearly polarized midinfrared laser pulses. With a high electric field, the perpendicular polarization component of the odd harmonics emerges, which is not present with a low electric field and cannot be explained by the perturbative nonlinear optics. A two-dimensional single-band model is developed to show that the anisotropic curvature of an energy band of solids, which is pronounced in an outer part of the Brillouin zone, induces the generation of the perpendicular odd harmonics. This model is validated by three-dimensional quantum mechanical simulations, which reproduce the orientation dependence of the odd-order harmonics. The quantum mechanical simulations also reveal that the odd- and even-order harmonics are produced predominantly by the intraband current and interband polarization, respectively. These experimental and theoretical demonstrations clearly show a strong link between the band structure of a solid and the polarization property of the odd-order harmonics.

Statistics and Machine Learning based Outlier Detection Techniques for Exoplanets

NASA Astrophysics Data System (ADS)

Goel, Amit; Montgomery, Michele

2015-08-01

Architectures of planetary systems are observable snapshots in time that can indicate formation and dynamic evolution of planets. The observable key parameters that we consider are planetary mass and orbital period. If planet masses are significantly less than their host star masses, then Keplerian Motion is defined as P^2 = a^3 where P is the orbital period in units of years and a is the orbital period in units of Astronomical Units (AU). Keplerian motion works on small scales such as the size of the Solar System but not on large scales such as the size of the Milky Way Galaxy. In this work, for confirmed exoplanets of known stellar mass, planetary mass, orbital period, and stellar age, we analyze Keplerian motion of systems based on stellar age to seek if Keplerian motion has an age dependency and to identify outliers. For detecting outliers, we apply several techniques based on statistical and machine learning methods such as probabilistic, linear, and proximity based models. In probabilistic and statistical models of outliers, the parameters of a closed form probability distributions are learned in order to detect the outliers. Linear models use regression analysis based techniques for detecting outliers. Proximity based models use distance based algorithms such as k-nearest neighbour, clustering algorithms such as k-means, or density based algorithms such as kernel density estimation. In this work, we will use unsupervised learning algorithms with only the proximity based models. In addition, we explore the relative strengths and weaknesses of the various techniques by validating the outliers. The validation criteria for the outliers is if the ratio of planetary mass to stellar mass is less than 0.001. In this work, we present our statistical analysis of the outliers thus detected.