共查询到20条相似文献，搜索用时 31 毫秒
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基于射频识别技术的仓储管理系统具有人工干预少、自动化程度高的优点,可极大地提高农产品立体仓库的自动化程度和工作效率.进行了基于51单片机的射频识别读写器的软硬件设计开发,初步完成了仓储数据库管理软件的部分功能模块,并进行了射频识别系统读写距离测试,结果表明系统读写距离基本满足设计要求. 相似文献
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RFID无线射频技术在图书馆的应用分析 总被引：2，自引：0，他引：2
陈海钦 《农业图书情报学刊》2011,23(11):163-166
阐述了RFID无线射频技术的工作原理,以及RFID无线射频技术在图书馆的应用及意义,RFID无线射频识别技术使图书的借还、自助借阅、防盗、盘点、检索、整理书架、自动分拣均通过电子标签完成。真正实现了自助借阅的快捷方便,防盗系统的可靠准确和盘点、找书、整理书架的快速。对无线射频识别技术与条形码技术进行了比较,分析了几种不同频段的RFID技术在图书馆应用中的优缺点,介绍了超高频RFID无线射频技术在少年儿童图书馆的实际应用。 相似文献
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由一种具体无线射频Model-PTR2000构成的单片机之间的无线射频通信系统,给出了必要的主要硬件电路组成,讨论了通讯软件设计和实现方法。由此可构成无线射频通信技术的基础,为实现各种不同具体要求单片机之间的通讯,提供了一种新的方法。 相似文献
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The Very Long Baseline Array is a high-resolution synthesis radio telescope consisting of ten antennas, each 25 meters in diameter, located throughout the United States from Puerto Rico to Hawaii. Each antenna will be equipped with low-noise receivers spaced throughout the frequency range from 330 megahertz to 43 gigahertz, a hydrogen-maser frequency standard for time and frequency reference, and broadband digital tape recorders. Tapes recorded at each antenna will be simultaneously replayed and correlated in a specially built digital correlator, and the correlator output will, by Fourier transformation, be used to construct images of celestial radio sources with an angular resolution better than one thousandth of an arc second. 相似文献
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设计和研制了一套用于研究电磁波非热效应的实验系统。该系统综合了工程上的TEM小室、开阔场地测量屏蔽室和微波暗室的优点，能产生一个具有极端的宽带特征、分布均匀、易于测量的电磁场区域，对周围的人或设备无害或无干扰。 相似文献
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LJ Lanzerotti K Rinnert G Dehmel FO Gliem EP Krider MA Uman J Bach 《Science (New York, N.Y.)》1996,272(5263):858-860
During the Galileo probe's descent through Jupiter's atmosphere, under the ionosphere, the lightning and radio emission detector measured radio frequency signals at levels significantly above the probe's electromagnetic noise. The signal strengths at 3 and 15 kilohertz were relatively large at the beginning of the descent, decreased with depth to a pressure level of about 5 bars, and then increased slowly until the end of the mission. The 15-kilohertz signals show arrival direction anisotropies. Measurements of radio frequency wave forms show that the probe passed through an atmospheric region that did not support lightning within at least 100 kilometers and more likely a few thousand kilometers of the descent trajectory. The apparent opacity of the jovian atmosphere increases sharply at pressures greater than about 4 bars. 相似文献
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Goldberg RA Curtis SA Barcus JR Siefring CL Kelley MC 《Science (New York, N.Y.)》1983,219(4590):1324-1327
Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung x-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the x-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes. 相似文献
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介绍了蓝牙射频技术及芯片NRF401,论述了以NRF401为核心器件的粮库温度监测系统的硬件电路及软件的设计,实现了安全、可靠、方便的粮库温度监测方法. 相似文献
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Cohen MH Gundermann EJ Hardebeck HE Harris DE Salpeter EE Sharp LE 《Science (New York, N.Y.)》1966,153(3737):745-746
The frequency spectrum of fluctuations caused by interplanetary scintillations may give a sensitive estimate of the diameter of a radio source. Observations of 3C 138, 3C 245, 3C 267, and 3C 273 give diameters of 0.1, 相似文献
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WM Folkner RA Preston JS Border J Navarro WE Wilson M Oestreich 《Science (New York, N.Y.)》1997,275(5300):644-646
Although the Galileo probe was designed to communicate only to the orbiter, the probe radio signal was detected at two Earth-based radio observatories where the signal was a billion times weaker. The measured signal frequency was used to derive a vertical profile of the jovian zonal wind speed. Due to the mission geometry, the Earth-based wind estimates are less sensitive to descent trajectory errors than estimates based on probe-orbiter Doppler measurements. The two estimates of wind profiles agree qualitatively; both show high wind speeds at all depths sampled. 相似文献
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The planetary radio astronomy experiment on board the Voyager spacecraft has detected bursts of nonthermal radio noise from Saturn occurring near 200 kilohertz, with a peak flux density comparable to higher frequency Jovian emissions. The radiation is right-hand polarized and is most likely emitted in the extraordinary magnetoionic mode from Saturn's northern hemisphere. Modulation that is consistent with a planetary rotation period of 10 hours 39.9 minutes is apparent in the data. 相似文献
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Markowitz W 《Science (New York, N.Y.)》1968,162(3860):1387-1388
A differential Loran C experiment, which is independent of variations in clock rates, shows that the frequency of a radio transmission is not affected by the mass of the earth. 相似文献
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The stable rotation and sharp radio pulses of PSR 1937+21 make this pulsar a clock whose long-term frequency stability approaches and may exceed that of the best atomic clocks. Improvements in measurement techniques now permit pulse arrival times to be determined in 1 hour at the Arecibo radio telescope with uncertainties of about 300 nanoseconds relative to atomic time. Measurements taken approximately every 2 weeks since November 1982 yield estimates of fractional frequency stability that continue to improve with increasing averaging time. The pulsar's frequency stability is at least as good as 6 x 10(-14) for averaging times longer than 4 months, and over the longest intervals the measurements appear to be limited by the stability of the reference atomic docks. The data yield a firm upper limit of 7 x 10(-36) gram per cubic centimeter for the energy density of a cosmic background of gravitational radiation at frequencies of about 0.23 cycle per year. This limit corresponds to approximately 4 x 10(-7) of the density required to close the universe. 相似文献
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安全是智能农业建设的重要目标,基于标签认证的无线射频识别安全机制研究为智能农业的安全建设提供了新的思路和手段。通过聚焦无线射频识别技术在智能农业应用中存在的安全问题,并在此基础上改进了多标签认证研究。希望以此助推智能农业与安全技术的深度、高效融合,让无线射频识别安全机制为智能农业建设保驾护航。 相似文献
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Levy GS Linfield RP Ulvestad JS Edwards CD Jordan JF DI Nardo SJ Christensen CS Preston RA Skjerve LJ Stavert LR Burke BF Whitney AR Cappallo RJ Rogers AE Blaney KB Maher MJ Ottenhoff CH Jauncey DL Peters WL Nishimura T Hayashi T Takano T Yamada T Hirabayashi H Morimoto M Inoue M Shiomi T Kawaguchi N Kunimori H 《Science (New York, N.Y.)》1986,234(4773):187-189
An orbiting spacecraft and ground observatories have been used to obtain interferometric observations of cosmic radio sources. The Tracking and Data Relay Satellite System (TDRSS) was used as the orbiting observatory in conjunction with two 64- meter radio telescopes at ground observatories, one in Australia and one in Japan. The quasars 1730-130 (NRAO 530), 1510-089, and 1741-038 were observed at a frequency of 2.3 gigahertz, and a maximum projected baseline of 1.4 earth diameters was achieved. All quasar observations for which valid data were acquired resulted in detected fringes. Many of the techniques proposed for a dedicated very long baseline interferometry observatory in space were used successfully in this experiment. 相似文献
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基于 RFID 的茶叶物流追溯系统 总被引：1，自引：0，他引：1
利用Coogle公司开发的GoogleMaps,构建了一套基于射频识别技术（RFID）的茶叶物流追溯系统,确保茶叶在生产、加工、销售过程中实物流与信息流的“无缝”对接．消费者可通过浏览器直观地获得所购茶叶的相关信息． 相似文献
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为了减小射频功率放大器的记忆效应,进一步提高功率放大器的线性度,采用漏极静态偏置电阻优化的方法消除电记忆效应,并利用PN结温度升高使导通电压下降的特性进行温度补偿以抵消电热记忆效应.高级电子设计系统（Advanced Design System,ADS）仿真结果表明,放大器三阶互调的高低频谱分量的差值从6.88 dB降低到0.214 dB,显著地消除了电记忆效应,同时也在一定程度上改善了电热记忆效应. 相似文献