Noise and Finite Register Effects in Infrared Fourier Transform Spectroscopy

1976 ◽  
Vol 30 (5) ◽  
pp. 531-539 ◽  
Author(s):  
C. T. Foskett
Keyword(s):  
Fourier Transform ◽  
Data Acquisition ◽  
Fast Fourier Transform ◽  
Fourier Transform Spectroscopy ◽  
Noise Sources ◽  
Additional Noise ◽  
The Impact ◽  
The Relationship

Finite registers used in computations act as additional noise sources in infrared Fourier transform spectroscopy. The relationship between these noise sources and classical noise sources is examined. The impact of finite register lengths on data acquisition, computation of the fast Fourier transform (FFT), and post-FFT spectral manipulations leads to the conclusion that the minimum recommended register length is 27 bits.

An improved de Laval nozzle experiment

2021 ◽  
pp. 030641902110341
Author(s):  
Nicholas Goodman ◽  
Brian J Leege ◽  
Peter E Johnson
Keyword(s):  
Data Acquisition ◽  
Laval Nozzle ◽  
Flow Characteristics ◽  
Data Acquisition System ◽  
Isentropic Flow ◽  
Hands On ◽  
De Laval Nozzle ◽  
Physical Phenomena ◽  
The Impact ◽  
The Relationship

Exposing students to hands-on experiments has been a common approach to illustrating complex physical phenomena that have been otherwise modelled solely mathematically. Compressible, isentropic flow in a duct is an example of such a phenomenon, and it is often demonstrated via a de Laval nozzle experiment. We have improved an existing converging/diverging nozzle experiment so that students can modify the location of the normal shock that develops in the diverging portion to better understand the relationship between the shock and the pressure. We have also improved the data acquisition system for this experiment and explained how visualisation of the standing shock is now possible. The results of the updated system demonstrate that the accuracy of the isentropic flow characteristics has not been lost. Through pre- and post-laboratory quizzes, we show the impact on student learning as well.

scholarly journals A Study on Noise Reduction of Gear Pumps of Wheel Loaders Based on the ICA Model

2019 ◽  
Vol 16 (6) ◽  
pp. 999 ◽  
Author(s):  
Panling Huang ◽  
Liang Xu ◽  
Chuan Luo ◽  
Jianchuan Zhang ◽  
Feng Chi ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Noise Reduction ◽  
Noise Level ◽  
Gear Pump ◽  
Noise Sources ◽  
Environmentally Sustainable ◽  
Gear Pumps ◽  
Mixed Noise ◽  
Wheel Loaders

In order to reduce the noise level of wheel loaders caused by gear pumps and realize environmentally sustainable development, the noise generation mechanism of a gear pump was studied, and the influence of flow pulsation and gear impact on noise was analyzed. In order to reduce the interference of other noise sources on the noise level of the gear pump, a noise test rig was established. The mixed noise signals obtained from the rig test were separated using the ICA model. The ICA model includes the following algorithms: The fast Fourier transform (FFT), independent component analysis (ICA) and inverse fast Fourier transform (IFFT). Some theories about the influence of the teeth number and teeth profile on noise were analyzed by theory and simulation. A noise reduction strategy was proposed by increasing the teeth numbers and modifying the teeth profile of the gear pump. The tests results showed that the noise values of the external and the driver’s ear of the wheel loader were reduced to 1 and 2.2 dB (A), respectively. This proves the effectiveness of the optimization scheme of gear pump noise reduction.

The Application of Fast Fourier Transform and Convolution Techniques to Picosecond Continuum Spectroscopy

1983 ◽  
Vol 37 (3) ◽  
pp. 273-279 ◽  
Author(s):  
K. L. Sala ◽  
R. W. Yip ◽  
R. LeSage
Keyword(s):  
Fourier Transform ◽  
Data Processing ◽  
Data Acquisition ◽  
Fast Fourier Transform ◽  
Experimental Technique ◽  
Transient Absorption ◽  
Computation Time ◽  
Spectroscopic Technique ◽  
Experimental Results ◽  
Data Acquisition And Processing

The use of the fast Fourier transform in the processing of photographic data obtained from picosecond continuum spectroscopy is described. The resulting reduction in the complexity and computation time has permitted all of the data acquisition and processing to be carried out with an eight-bit microcomputer. Specific examples of some key problems in the data processing that are peculiar to this spectroscopic technique and methods of overcoming these problems are discussed. Experimental results that serve to illustrate both the experimental technique itself as well as the versatility and reliability of the data processing algorithm are presented for the transient absorption of a Cr(III) complex in solutions.

scholarly journals The effect of fuel mixture on engine vibrations

2019 ◽  
Vol 177 (2) ◽  
pp. 136-138
Author(s):  
Radosław WRÓBEL ◽  
Łukasz ŁOZA ◽  
Piotr HALLER ◽  
Radosław WŁOSTOWSKI
Keyword(s):  
Fourier Transform ◽  
Comparative Analysis ◽  
Data Acquisition ◽  
Fast Fourier Transform ◽  
Frequency Response ◽  
Fuel Mixture ◽  
Graphical Form

In the article, the authors analyze the effect of a fuel mixture (iso-octane, butanol and ethanol) on the generation of engine vibrations. The paper presents the results in the form of frequency response (using the Fast Fourier Transform – FFT) for three mixtures of different proportions. The measurements were made with the use of accelerometers and data acquisition cards, conditioning the received signal. The vibration component, in the form of acceleration, will be subjected to a FFT and presented in graphical form (periodogram). The authors put a special emphasis on a comparative analysis, indicating changes in harmonics, which may be a potential cause of engine degradation.

scholarly journals A study of acoustic characteristics of voluntary expiratory sounds produced before and immediately after swallowing

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Shoma Hattori ◽  
Shinji Nozue ◽  
Yoshiaki Ihara ◽  
Koji Takahashi
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Time Window ◽  
Maximum Amplitude ◽  
Comparison Method ◽  
Window Length ◽  
Acoustic Characteristics ◽  
The Mean ◽  
Time Waveform ◽  
The Relationship

AbstractTo evaluate the expiratory sounds produced during swallowing recorded simultaneously with videofluorographic examination of swallowing (VF) using fast Fourier transform (FFT), and to examine the relationship between dysphagia and its acoustic characteristics. A total of 348 samples of expiratory sounds were collected from 61 patients with dysphagia whose expiratory sounds were recorded during VF. The VF results were evaluated by one dentist and categorized into three groups: safe group (SG), penetration group (PG), and aspiration group (AG). The duration and maximum amplitude of expiratory sounds produced were measured as the domain characteristics on the time waveform of these sounds and compared among the groups. Time window-length appropriate for FFT and acoustic discriminate values (AD values) of SG, PG, and AG were also investigated. The groups were analyzed using analysis of variance and Scheffé's multiple comparison method. The maximum amplitude of SG was significantly smaller than those of PG and AG. The mean duration in SG (2.05 s) was significantly longer than those in PG (0.84 s) and AG (0.96 s). The AD value in SG was significantly lower than those in PG and AG. AD value detects penetration or aspiration, and can be useful in screening for dysphagia.

scholarly journals Reducing the Cost of Implementing Filters in LoRa Devices

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 4037
Author(s):  
Shania Stewart ◽  
Ha H. Nguyen ◽  
Robert Barton ◽  
Jerome Henry
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
System Performance ◽  
Pulse Shaping ◽  
Error Rates ◽  
Lookup Table ◽  
Significant Performance ◽  
High Level ◽  
The Cost ◽  
The Impact

This paper presents two methods to optimize LoRa (Low-Power Long-Range) devices so that implementing multiplier-less pulse shaping filters is more economical. Basic chirp waveforms can be generated more efficiently using the method of chirp segmentation so that only a quarter of the samples needs to be stored in the ROM. Quantization can also be applied to the basic chirp samples in order to reduce the number of unique input values to the filter, which in turn reduces the size of the lookup table for multiplier-less filter implementation. Various tests were performed on a simulated LoRa system in order to evaluate the impact of the quantization error on the system performance. By examining the occupied bandwidth, fast Fourier transform used for symbol demodulation, and bit-error rates, it is shown that even performing a high level of quantization does not cause significant performance degradation. Therefore, the memory requirements of LoRa devices can be significantly reduced by using the methods of chirp segmentation and quantization so as to improve the feasibility of implementing multiplier-less filters in LoRa devices.

Multi-Symplectic Fourier Pseudospectral Method for the Kawahara Equation

2014 ◽  
Vol 16 (1) ◽  
pp. 35-55 ◽  
Author(s):  
Yuezheng Gong ◽  
Jiaxiang Cai ◽  
Yushun Wang
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Pseudospectral Method ◽  
Kawahara Equation ◽  
Fourier Pseudospectral Method ◽  
Numerical Examples ◽  
Fourier Pseudospectral ◽  
Energy And Momentum ◽  
The Relationship ◽  
Pseudospectral Scheme

AbstractIn this paper, we derive a multi-symplectic Fourier pseudospectral scheme for the Kawahara equation with special attention to the relationship between the spectral differentiation matrix and discrete Fourier transform. The relationship is crucial for implementing the scheme efficiently. By using the relationship, we can apply the Fast Fourier transform to solve the Kawahara equation. The effectiveness of the proposed methods will be demonstrated by a number of numerical examples. The numerical results also confirm that the global energy and momentum are well preserved.

An X-ray diffractometer coupled with diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography forin situandin operandocharacterization: an innovative analytical laboratory instrument

2012 ◽  
Vol 46 (1) ◽  
pp. 262-266 ◽  
Author(s):  
Laure Braconnier ◽  
Isabelle Clémençon ◽  
Christèle Legens ◽  
Virginie Moizan ◽  
Fabrice Diehl ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Fourier Transform Spectroscopy ◽  
Material Surface ◽  
X Ray Diffraction ◽  
Reaction Cell ◽  
X Ray ◽  
High Pressure Reaction ◽  
Diffuse Reflectance Infrared ◽  
The Impact

In heterogeneous catalysis, chemical reactions take place at the surface of the material and can be influenced by its structure. To understand better the impact of the material surface and structure on catalytic properties, it is important to characterize them simultaneously. The association of X-ray diffraction and diffuse reflectance infrared Fourier transform spectroscopy, combined in a single dedicated high-temperature and high-pressure reaction cell with an online gas chromatograph, could be the answer to this challenge. For the first time, such an analytical tool has been developed for laboratory applications. The use of this device is illustrated, and it is validated through thein situstudy of the thermal decomposition of calcium oxalate.

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