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81.
82.
总结了近几十年来包括活性炭、沸石、蒙脱石、海泡石、麦饭石、凹凸棒石、氧化铝、氢氧化钠、明矾、纳米材料等矿物材料作为卷烟滤嘴添加剂以去除烟气中有毒有害物质的研究和实验应用及效果。实验结果和市场调查表明,活性炭是减少卷烟危害最快、香烟市场应用增长最快的过滤嘴添加剂。从降低卷烟有害成分的比例和成本等综合因素来看,铝硅酸盐类滤嘴和多材料复合滤嘴亦有很好的应用前景和市场需求,应积极进行研制。 相似文献
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陆相沉积的天文地层研究方法简介——以井下地层为例 总被引:2,自引:5,他引:2
XU Dao-yi ) ZHANG Hai-feng ) HAN Yan-ben ) YIN Zhi-qiang ) LI Bao-li ) YAO Yi-min ) ) Institute of Geology China Earthquake Administration Beijing ) Geological Scientific Research Institute of Shengli Oilfield Company SINOPEC Dongying ) National Astronomical Observatories Chinese Academy of Sciences Beijing 《地层学杂志》2007,(Z2)
通过对我国大陆三十余口井的测井资料研究成果,归纳出对陆相地层进行天文地层研究的方法。介绍了所用的新的天文周期理论值、测井资料的选取及预处理方法,重点说明谱分析的数据点数的选定、不同参数(自然伽玛、自然电位和岩屑)的测井资料谱分析结果的对比,以实例说明如何选定主要优势旋回和AR值,以及FIR数字滤波器的基本性质和数字滤波结果,小波分析的特点和通过小波图进行调频的方法,并介绍了地层单位的延续时间计算和年龄确定方法。 相似文献
85.
86.
为了更好地降低或消除供电系统中的三次谐波,保障供电系统的安全运行,针对三次谐波对供配电系统的影响越来越严重的现状,以国家气象信息中心供配电系统为研究对象,采用理论分析与实际测量相结合的方法,对三次谐波的危害及抑制措施进行了研究。指出了三次谐波产生的原因,分析了三次谐波引起的5种主要危害,并以此为依据,提出了降低或消除三次谐波的6种不同方法。通过对降低或消除三次谐波不同方法进行分析、对比,结合实践的检验,通过在配电系统接近负荷的位置安装D-Yn接法隔离变压器,可以最有效地抑制三次谐波产生的各种危害,明显改善供电系统的供电质量和配电系统及设备的安全运行,是行之有效的三次谐波抑制措施。 相似文献
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LIN Xueyuan XU Jin ZHOU Min 《地球空间信息科学学报》2007,10(3):177-180
When SINS (strap-down inertial navigation system) is combined with GPS, the observability of the course angle is weak. Although the course angle error is improved to some extent through Kalman filtering, the course angle still assumes a divergent trend. This trend is aggravated further when using low-cost and low-accuracy SINS. In order to restrain this trend, a method that uses AHRS to substitute for SINS course angle information is put forward aimed at the hardware component characteristic of the low-cost and low-accuracy SINS including AHRS (attitude and heading reference system) and IMU (inertial measurement unit). Real static and dynamic experiments show that the method can restrain the divergent trend of the navigation system angle effectively, and the positioning accuracy is high. 相似文献
89.
A method to improve the alignment performance for GPS-IMU System 总被引:1,自引:0,他引:1
Zero velocity and zero east component of rotation rate relative to local geographic frame have been traditionally applied
as measurements for fine alignment of a GPS-IMU system. The performance of the fine alignment, however, will be affected by
several types of inertial sensor errors, which could cause part of the Kalman filter states to be unobservable. To overcome
this problem, a new method that utilizes the total outputs of the gyro triad and the accelerometer triad as part of the measurements
has been proposed by the authors. The initial results have confirmed the effectiveness of the method. In this paper, the observability
for both traditional and new alignment methods will be first reviewed. The results from computer simulations will then be
presented to compare the traditional and the new alignment methods for the purpose of evaluating the performance of the proposed
new method. Data acquired from real inertial sensors will also be applied to assess the traditional and new alignment methods
by analyzing their innovation sequences from the Klaman filter.
Based on a paper presented at the 18th International Technical Meeting of the Satellite Division of the Institute of Navigation,
Long Beach, California, September 2005. 相似文献
90.
Multipath error is considered one of the major errors affecting GPS observations. One can benefit from the repetition of satellite
geometry approximately every sidereal day, and apply filtering to help minimize this error. For GPS data at 1 s interval processed
using a double-difference strategy, using the day-to-day coordinate or carrier-phase residual autocorrelation determined with
a 10-h window leads to the steadiest estimates of the error-repeat lag, although a window as short as 2 h can produce an acceptable
value with > 97% of the optimal lag’s correlation. We conclude that although the lag may vary with time, such variation is
marginal and there is little advantage in using a satellite-specific or other time-varying lag in double-difference processing.
We filter the GPS data either by stacking a number of days of processed coordinate residuals using the optimum “sidereal”
lag (23 h 55 m 54 s), and removing these stacked residuals from the day in question (coordinate space), or by a similar method
using double-difference carrier-phase residuals (observational space). Either method results in more consistent and homogeneous
set of coordinates throughout the dataset compared with unfiltered processing. Coordinate stacking reduces geometry-related
repeating errors (mainly multipath) better than carrier-phase residual stacking, although the latter takes less processing
time to achieve final filtered coordinates. Thus, the optimal stacking method will depend on whether coordinate precision
or computational time is the over-riding criterion. 相似文献