A digital signal converter for radio astronomical systems

A digital signal converter operating in a video frequency band (up to 32 MHz) and intended for radio astronomical equipment is based on an LTC2288 analog-to-digital converter and an XC4VSX25 field programmed gate array. A two-band base band converter improving parameters of the radio interferometric terminal, a two-channel spectrometer minimizing times of observation of radio-frequency sources in spectral lines, and a radiometer for recording signals in a continuum operating under the action of radio interference have been designed using the converter. The advantages of this equipment are confirmed by results of tests at the Svetloe radio astronomical observatory.     

A Data Acquisition System for Very-Long-Baseline Interferometers

A data-acquisition system designed for very-long-baseline interferometers is connected to the outputs of cryoelectronic radio astronomy receivers, selects signals in specified frequency bands, and converts them into digital data flows for their recording or transmission through telecommunication channels. The system has two inputs and may contain from two to eight base-band converters with an intermediate frequency tuning range of 100–1000 MHz with a 10-kHz step. These converters transform input signals into video frequencies (up to 16 MHz) and separate signals of the upper and lower side bands with an image rejection of >23 dB. The distortions and loss in the phase coherence of the received noise signals are minimized thanks to the equalizing of the amplitude and phase responses of the amplifiers and selectors, and the good spectral characteristics of the local oscillators of the base-band converters. The data-acquisition system is controlled by a PC or the Mark IV Field System program (now used internationally in the pursuit of radio interferometry), which is installed in the radio telescope's central computer using an RS-232 interface. The prototype of such a system is used as standard equipment for conducting observations on the Svetloye–Zelenchukskaya radio interferometer. The first lot of such systems for the development of a network of radio interferometers has been produced.     

A soft and hardware complex for recording and processing of acoustic emission signals and for location and identification of their sources

A soft and hardware complex designed for recording and processing acoustic emission (AE) signals in real time is described. The hardware part of the complex includes a computer with PCI connectors, four-channel parallel-reading analog-to-digital converters (ADCs), preamplifiers, and receiving converters. The software part of the complex is used to record and save in all recording channels the full shape of signals with a preset sampling frequency of up to 20 MHz, locate, identify, and classify AE sources in real time. It differs from analogs in the capability of saving the full shape of AE signals for further analysis and processing, in use of commercially produced ADCs, and in real-time data processing and classifying of AE sources.     

一种轻小型四极杆质谱仪射频电源的研制

四极杆结构是四极杆质谱仪的核心结构，由射频电源分别施加两组高压高频信号进行驱动，利用电场的变化和输入离子的质荷比差异对离子进行筛选。针对四极杆质谱仪小型化的研制需求，以信号调制模块、放大模块、反馈电路和直流模块为基本构型，设计了一种应用于轻小型四极杆质谱仪的射频驱动电源。经实际测试，该电源可以在谐振频率1.33 MHz、扫描频率10 Hz的输入条件下，输出峰 峰值电压最高可达3.33 kV的调幅射频高压信号并驱动四极杆结构，扫描切换时间不高于1 ms。射频电源输出信号稳定、波动小、交直比的波动为0.1%。该射频电源相较于常规的四极杆射频电源具有更高的扫描范围，体积小巧，功耗仅30 W，接口简单，有较高的实用价值。     

A Data Stream Converter for a Radio Telescope with a Wideband-Signal Digital Recording System

A data-stream converter makes it possible to connect a radio telescope with wideband (512 MHz) signal-recording channels to active very-long-baseline interferometers using multichannel recording systems for narrowband (16 or 8 MHz) signals. A digital converter based on a field programmed gate array (FPGA) selects and formats up to 16 narrowband signals.     

含氮固体物质的核四极共振远程探测仪

本文介绍一台结构简单，造价低廉的１４Ｎ核四极共振远程探测仪。它利用脉冲傅立叶变换技术，将获得的核自由感应衰减信号或回波信号进行相干累加以提高信噪比。整个系统分硬件和软件两部分。前者由射频脉冲放大器（有效值功率输出约３００Ｗ）、探头、接收机和ＩＢＭ—ＰＣ机构成。后者由ＰＣ机上的脉冲序列程序和数字信号处理程序组成。利用这台谱仪，能够在几十秒时间内得到距离探头线圈１０厘米以内的典型含氮化合物的核四极共振谱     

A 32-Channel High-Speed Simultaneously Sampling Data Acquisition System

The system is intended for recording data in the multichannel diagnostic sections of experimental plasma facilities. It contains eight four-channel modules that record the shapes of single pulse signals, a controller module of the system bus of the crate, a fiber-optic communication line, and an interface card for connection to the ISA bus of a personal computer. The recording modules are based on 12-bit analog-to-digital converters (ADCs) with a sampling frequency of up to 50 MHz, ensuring a conversion accuracy equal to the least significant bit in a band of the input signal of up to 20 MHz. The ADC samples are fixed in 32-Kword/channel buffer storage units with a page organization. The current values of the amplitude of the input signals in all of the recording channels are measured simultaneously with a time jitter of no more than 0.2 ns. The software selects an amplitude conversion scale and a zero offset voltage value for each recording channel, as well as the current value of the sampling frequency for all the channels.     

Estimating Gastric Rhythm Differences Using a Wavelet Method from the Electrogastrograms of Normal and Diabetic Subjects

Abstract

Electrogastrogram (EGG) is the cutaneous recording of gastric electrical activity. Some patients with nausea, vomiting, early satiety, and patients with long term insulin‐dependent diabetes exhibit gastric electrical rhythm disturbances. We are interested in investigating the EGG to determine if abnormalities of the EGG occur in association with those gastric complaints. The aim of this document is to investigate long term diabetics with a history of such gastric dysrhythmia complaints in an effort to further characterize the frequency of abnormalities of the EGG in real clinical diabetic gastroparesis patients. For feature extraction purposes, we have performed Wavelet‐Packet analysis of EGG signals and have obtained power spectral density of wavelet‐packet details and approximation coefficients in diabetic patients suffering from gastric dysrhythmia (tachygastria, bradygastria) and healthy volunteers. Wavelet‐Packet analysis provides details of changes in frequency components at any time point, and enhanced interpretation of cutaneous EGG recordings. In conclusion, this paper has shown that the Wavelet‐Packet analysis method is very useful in the analysis of cutaneous EGG recordings, especially in detecting dysrhythmic events.     

A Complex for Carrying Out Radar Observations of Near-Earth Objects

The Institute of Applied Astronomy of the Russian Academy of Sciences and the Goldstone Deep Space Communications Complex regularly conduct intercontinental radar observations of near-Earth objects using a 70-m DSS-14 antenna as a transmitter and the 32-m RT-32 radio telescopes of the Quasar VLBI network as receivers. To carry out the observations, the existing complex for reception, conversion, and recording of signals from the RT-32 radio telescopes has been adapted and special software for scheduling observations and processing echo signals has been developed. Since 2015, echoes from the 2011 UW158, 2003 TL4, 2003 YT1, 2003 BD44, and 2014 JO25 asteroids have been recorded. The power spectra of the echoes from these asteroids have been obtained and analyzed.     

A data acquisition system of the S/X-wave range of the radio interferometer for the universal time on-line monitoring

A system is intended for equipping radio telescopes with antennas of small (12–13 m) diameters, used in the very long baseline interferometers (VLBIs), including universal time on-line monitoring interferometers. The system operates in S- and X-wavelength ranges and process up to 8 signals with spectrum widths of up to 512 MHz, converts them into digital sequences with a 1024-MHz clock frequency, and forms data streams in the VLBI Data Interchange Format (VDIF) with a 2048-Mbit/s rate per channel. Data from each channel of the system via the 10G Ethernet interface are transmitted to the data buffering unit for their sending to the correlation processing center.     

A radiointerferometric terminal of the Badary observatory

A radiointerferometric terminal recording signals on hard magnetic disks in the VSI-H format with a rate of up to 1024 Mbit/s is put into operation for the first time in Russia at the Badary observatory. This ensures the possibility of very-long-base radiointerferometry (VLBI) in quasi-real time. A P1000 signal conversion system containing 14 two-band video converters and a 16-channel 2-bit signal digitizing unit with a record-synchronizing device is designed for this terminal at the Institute of Applied Astronomy, Russian Academy of Sciences, and ZAO Radio-Electronic Processing Equipment. The signals are recorded by a Mark 5B recording equipment. The central computer of the radio telescope controls the terminal. Under the international and domestic programs, routine VLBI observations are conducted by the designed terminal in the Badary observatory.     

Oxygen content of the fixative is important in the interpretation of the ultrastructure of ischaemic myocardium

Isolated rat hearts were subjected to 15, 45, or 60 minutes of global ischaemia and then fixed by perfusion at 37°C with glutaraldehyde containing various amounts of oxygen. This either had been bubbled with 100% oxygen (PO₂ 620 mm Hg) or with 100% nitrogen (PO₂ 40 mm Hg) immediately before use, or it had been routinely prepared and stored exposed to atmospheric oxygen (PO₂ 245 mm Hg). The ultrastructure of myocytes and endothelial cells subjected to 15 minutes of ischaemia was not affected by the treatment of the fixative. However, when the tissue subjected to longer periods of ischaemia was fixed with routinely prepared or oxygen-bubbled glutaraldehyde, ultrastructural changes characteristic of reoxygenation damage were uniformly evident in both the microvasculature and myocytes. These qualitatively distinct changes included mitochondrial swelling, cell swelling, endothelial bleb formation, and narrowing of capillary lumina. These abnormalities were not observed in tissue fixed with nitrogen-bubbled glutaraldehyde. These findings indicate that deliberate steps should be taken to reduce or eliminate dissolved oxygen from the fixatives used to study ischaemic tissues. Otherwise artefactual reoxygenation damage in vitro may occur and make valid ultrastructural interpretation difficult or impossible.     

A telemetric measurement complex for acoustic and hydrophysical investigations

A hardware-software complex that allows synchronous measurements of hydroacoustic noises and signals, the temperature, and the pressure at a specified point and provides transmission of theses characteristics via a radio channel and their recording in a shore-based analytical center is described. The offshore part of the complex includes a GPS receiver for testing the location during drift. The results of an experimental approbation of the complex during acoustic thermometry of a water area in the Vityaz bay of the Posiet gulf in the Sea of Japan are presented.     

Linear discriminant function analysis of acoustic emission signals for cutting tool monitoring

A principal setback to automation of the machining process is the inability to completely monitor the condition of the cutting tool in real time. Whereas several of the techniques developed to date are useful in specific applications, no universally applicable sensor is yet available.Acoustic emission is one of the most promising techniques to be recently developed for on-line cutting tool monitoring. However, signal analysis is still an area that requires further investigation to enhance the potential of acoustic emission. For this purpose, frequency-based pattern recognition concepts using linear discriminant functions have been used in analysing acoustic emission signals generated during machining to distinguish between different signal sources, specifically chip formation, tool fracture, and chip noise. Five features were used for classification in the frequency range of 100 kHz to 1 MHz, with each feature consisting of a 20 kHz bandwidth, and were selected using the class mean scatter criterion. The coefficients of the discriminant functions were obtained by training the system using signals generated by each of the sources of interest. An AISI 1018 steel was machined using a titanium carbide-coated cutting tool. Cutting speeds ranged from 200 to 800 ft/min (1 to 4 m/sec) with feed rats of 0·0005 to 0·0075 in/rev (0·0133 mm/rev to 0·191 mm/rev) and depth of cut 0·17 in (4·32 mm). The results show a successful classification rate of 90% for tool breakage, while those for chip formation and chip noise were 97 and 86% respectively.     

Comparison of intra-arterial and automated oscillometric blood pressure measurement methods in postoperative hypertensive patients

A comparison of blood pressures measured by direct radial intra-arterial and indirect brachial automated oscillometric methods (Dinamap 1845), was performed in thirty hypertensive post-carotid endarterectomy patients. Five hundred fifty-eight "triplet" readings of systolic, diastolic, and mean blood pressure were compared. Mean differences of 18.92, -6.32, and -0.26 mm Hg, and correlation coefficients of 0.831, 0.724, and 0.776 were calculated for systolic, diastolic, and mean blood pressures, respectively. Mean differences were then calculated within incremental direct systolic pressure ranges of 20 mm Hg and found to become significantly larger with each increasing increment of pressure. These differences ranged from -0.8 to 12.6 and 20.0 to 53.3 mm Hg in the less than 160 and greater than 160 mm Hg groups, respectively, with direct intra-arterial systolic pressures significantly greater than indirect oscillometric systolic pressures in the latter group. The results demonstrate that in the hypertensive pressure range, a significant difference exists in systolic pressure measured by intra-arterial and automated oscillometric methods.     

Time–frequency analysis of tribological systems—part II: tribology of head–disk interactions

Head–disk interface processes operating in contact and near contact recording generate signals that have a distinct frequency for short time intervals and these processes are known as non-stationary. Time–frequency representation displays time, frequency, and amplitude to characterize such processes. Examples drawn from practical head–disk interface signals are analyzed by adapting the fast Fourier transform algorithm to illustrate the dynamic features jointly in time and frequency. Time–frequency analysis of laser Doppler vibrometer (LDV), friction, and acoustic emission (AE) signals give evidence of non-stationary signals obtained from head–disk dynamics experiments. Novel results depicted by the time–frequency analysis technique not reported elsewhere demonstrate the benefit and usefulness of the proposed techniques.     

利用小波包分解提取思维脑电40Hz阵发性信号

确定大脑思维活动与脑电记录之间的时间对应关系是思维脑电研究的关键,阵发性40Hz脑电信号理论有效地解决脑电信号的选择问题,而准确提取阵发性40Hz脑电信号成为分析思维脑电的前提.论文在研究小波包分解与重构的特征的基础上,讨论了小波包分解树的频带分布规律,确定以Shannon熵为熵标准选择Daubechies5小波对脑电信号的进行9层分解,并通过重构获得了频带约为36.1-43.9Hz的窄带40Hz阵发性脑电信号.小波包分解比传统的滤波器分解更便捷,分解得到的阵发性40Hz脑电信号更精确,可以用来作为思维脑电同步选择的依据.     

Radio-frequency probe for bubble size and velocity measurements

A radio frequency (rf) probe that can provide local void fraction and interface velocity measurements in a gas-liquid two-phase flow was developed. The probe response to bubble passage was investigated with single-bubble controlled experiments. For a fixed geometry, the probe response was dependent on the dielectric constant of the medium surrounding the probe tip (air or water) and on the frequency of the carrier signal supplied to the probe. Bubble lengths (< 1 cm) and average bubble approach velocities (< 160 cm/s) were independently measured by two light sources and detectors placed at a known distance from each other and sensing the passage of each bubble. By choosing a sensitive probe tip length of 2.75-3 mm, the rf probe output provided enough information to determine the bubble length and velocity. The results obtained by the two independent methods show reasonable agreement (+/-10%).     

The Prospects for Using High-Speed Analog-to-Digital Converters to Analyze the Signals of Ionizing-Radiation Detectors

The potential advantages of recording digital signals from ionizing-radiation detectors are considered. State-of-the-art high-speed analog-to-digital converters operating at sampling frequencies of 400 MHz (2.5 ns) and higher with a buffer storage of up to 4 Gbyte and a data-input rate of up to 400 Mbyte/s are capable of recording continuous pulse sequences with a throughput of >10⁷ pulse/s in less than 10 s. In contrast to standard recording methods in which overlapping pulses are truncated, the recording of complete signal flows allows one to detect and resolve overlapping pulses quite well, provided they arrive within 20–40 ns of one another.     

A broadband noise-signal spectrometer of a millimeter wavelength band

The spectrum recording method for the broadband noise signal of millimeter wavelength band is considered. It is based on using resonance frequency meters of the millimeter wavelength band, removing the part of the power from the base waveguide transmission line at the resonance. This frequency meter with a changed design makes it possible, together with a corresponding recording device, to unambiguously define the spectrum width of a broadband noise signal and make a paper copy. An example of spectrum recording on the S4-60 spectrum analyzer screen and a paper copy made by a two-coordinate self-recording instrument is presented.