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1.
熊小芸 《地震地磁观测与研究》1986,(1)
本文介绍一种结构简单,价格便宜,用CMOS—LSI器件组成的编码数字钟,该钟具有BCD串、并码输出和日历转换功能,性能可靠,可供地震地磁台站作计时器和实现各种时序控制。目前由于LSI和VLSI器件的发展,为设计各种计时电路、数字钟电路提供了方便条件。例如小型计算器上的数字钟,各种民用数字手表机芯电路等等。但上述数字钟、表在液 相似文献
2.
陈金林 《地震地磁观测与研究》1986,(4)
在单板机定时检测、时序控制及过程控制系统中,各种控制操作往往是按严格的时间表进行的。因此要求有一实时时钟为其提供时间服务。时钟可分为硬件钟和软件钟两种。一般说来,硬件钟精度比较高,但在一些对时间精度要求不甚高的场合,软件钟除了能满足任务要求外,还具有充分利用单板机资源而不需另增添设备,且使用灵活、对时方便等优点。本文仅就以“TP-801B”单板机为核心部件的“核旋仪自动遥测装置”中采用的实时时钟及其校时装置做一介绍。该钟的主要功能是自动记录年、月、日、时、分。当程序询问时,时钟将回 相似文献
3.
夏恩山 《地震地磁观测与研究》1989,(2)
目前常规台站地震观测用钟的状况是:一方面新产品不断涌现、待销;另一方面却是台站用钟告急,急待更新换代。一些省局台站管理部门,花了不少钱,选购了一些新产品,试图解决这一问题。但由于产品性能、质量上的问题,台站用钟就成为一个日益突出、难以解决的老大难问题了。但对地震观测来说,时钟又恰恰是唯一直接涉及观测内在质量的至关重 相似文献
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《地球物理学进展》2020,(2)
由于电磁波无法在水中传播,导致海底地震仪(OBS)与全球定位系统(GPS)无法进行实时对钟,因此会产生一定的时钟漂移.而受船时、海况等影响,被动源OBS在回收后往往电量亏损,致使设备回收时并没有完成对钟,无法直接利用对钟前后的时钟漂移量进行线性校正.本文选取中国科学院海洋研究所2016—2017年间在雅浦俯冲带进行的长周期被动源OBS实验所获得的数据,利用背景噪声互相关方法对OBS进行了时间校正.结果发现,各OBS在经过一年左右时间的布放后,时钟漂移量在1～3 s之间,且基本呈线性趋势,将该结果平均分配到每天从而完成线性校正.另外,探讨了时钟的非线性漂移、误差源、参考台站的选取等因素对时钟准确度的影响,为OBS的数据处理进行了有益的探索. 相似文献
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为达到海洋可控源电磁探测和远参考测量的目的,研究控制海底电磁激发脉冲发射的时间同步技术,包括发射前与GPS的对钟技术和发射中的同步技术,保证仪器工作的时间和公共的时间基准GPS信号保持精确一致,为后期的数据处理解释提供统一的时间坐标.对钟技术是指,在海洋调查船上完成仪器内部RTC芯片分频所得的秒脉冲信号RTC_PPS与GPS秒脉冲信号PPS时钟沿的同步;同步技术是指,海底工作过程中,仪器在预定的时钟沿将可控源信号精确发射出去.本论文采用CPLD芯片、RTC芯片、GPS模块和AVR单片机来完成对钟和同步模块的设计. 相似文献
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针对地磁观测台网中部分记录仪的时钟不准确及产出数据的对应时间与实际时间不一致的问题,提出了地磁数据时钟精度检验的扰动区间极值比对法,利用2015年3月国家地磁观测台网的全部数据对该方法的正确性和可靠性进行检验,并给出校正值。结果表明,该方法对于钟差超过1min的数据检出率达到100%,且对检出的异常数据给出误差小于2min的校正时间,准确率达到94.44%,不受地方时的影响。该方法为国家地磁观测台网对大量仪器时钟精度的监控、数据时钟检验和仪器校时提醒自动化以及磁扰日数据时间校正提供了有效的技术途径。 相似文献
8.
王凤霞 《地震地磁观测与研究》1981,(2)
在地震观测技术中,给地震记录系统提供准确、高精度的时间信号,对地震工作是非常重要的。时间服务系统的精度决定地震参数测定的误差。因此对时间精度的要求随着地震工作的飞跃发展而提高。地震记录用的计时钟也是不断发展提高的。由原来最早的机械钟——(如:船钟、天文摆钟等)。发展到第一代小型全晶体管化的SY_1型石英钟;以后又改进为SY_2型石英钟。 相似文献
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近年来,为了提高地震记录的时间服务质量,各类石英钟陆续问世,对钟的技术要求也越来越高。中国科学院陕西天文台发播的“BPM 标准时间、标准频率”授时信号,系国家确认的高精度时间基准。我国地震系统就是采用这个标准来测定时钟的“钟差”。测量钟差的仪器是“毫秒计”、“钟差计”等时间间隔测定器(基本原理见《地震》1981年第4期、第5期刊载的“数字对钟技术”一文)。测定器所采用的是一种基本的测定时间差的方法。但是,它不具备有分辨相关秒脉冲的能力,在使用中,仪器可能记录的是非相关 相似文献
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The system consists of three magnetic variometers with electrical output signals for theH, D, andZ components, a proton magnetometer for the total field, a data acquisition system, two cassette recorders, an analogue chart recorder, a calendar clock, and a telex. The analogue and digital input data are sampled at 10 sec intervals, averaged over a minute, and recorded on a magnetic tape cassette. The computed hourly and daily mean values and the daily minimum and maximum values are recorded together with the occurrence times on a second cassette, at the operator's request. Rapid run recording of the 10 sec values of each measured component is initiated automatically during magnetic storms.DIMARS incorporates several test functions as ROM test, A/D converter test, recorder test, telexline test and checking the memory content. The test functions can be activated by the equipment keyboard, or via the telex. The telex can also be operated as an output printer. 相似文献
12.
Jaymie R. Meliker Geoffrey M. Jacquez 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(5):625-634
Our research group recently developed Q-statistics for evaluating space–time clustering in case–control studies with residential histories. This technique relies
on time-dependent nearest-neighbor relationships to examine clustering at any moment in the life-course of the residential
histories of cases relative to that of controls. In addition, in place of the widely used null hypothesis of spatial randomness,
each individual’s probability of being a case is based instead on his/her risk factors and covariates. In this paper, we extend
this approach to illustrate how alternative temporal orientations (e.g., years prior to diagnosis/recruitment, participant’s
age, and calendar year) influence a spatial clustering pattern. These temporal orientations are valuable for shedding light
on the duration of time between clustering and subsequent disease development (known as the empirical induction period), and
for revealing age-specific susceptibility windows and calendar year-specific effects. An ongoing population-based bladder
cancer case–control study is used to demonstrate this approach. Data collection is currently incomplete and therefore no inferences
should be drawn; we analyze these data to demonstrate these novel methods. Maps of space–time clustering of bladder cancer
cases are presented using different temporal orientations while accounting for covariates and known risk factors. This systematic
approach for evaluating space–time clustering has the potential to generate novel hypotheses about environmental risk factors
and provides insights into empirical induction periods, age-specific susceptibility, and calendar year-specific effects. 相似文献
13.
目的:探讨螺旋CT五个辐射剂量测量点位(CTDI100)值之间的差异和相关性统计学关系,以及该机器的辐射稳定性。方法:通过辐射剂量计和辐射剂量模体对螺旋CT五个测量点位进行12次重复测定,对各个点位的测量结果计算其相对偏差,然后用单因素方差分析(One-Way ANOVA)方法分析各点位测量结果之间的显著性。结果:5个点位重复测量的相对标准差分别为0.33%(中心点)、0.73%(3点位)、0.32%(6点位)、1.00%(9点位)和0.32%(12点位);3点位和9点位的平均值接近,单因素方差分析无显著性差异;12点位和6点位的平均值与3点位平均值的相对偏差在0.5%以下。结论:测试螺旋CT辐射稳定性良好,测试机型3点位和9点位在CTDI100上测量等效。在非验收测试和状态测试场合CTDIP可以进行简化。 相似文献
14.
DZSS-1型深层数字地震仪由三分量检波器CDJ-6B、数据采集单元、磁带机、编码钟和回放装置组成。它采用循环浮点放大-A/D转换技术、低噪音运算放大器、CMOS器件,使仪器噪音小于0.3μV（折合到前级放大器输入端,均值）,动态范围大于96dB,采用调相制、串码、单轨盒式数字磁带记录。仪器频带范围1-30Hz,浮点72dB。有钟差显示（±1ms）、噪音和误操作显示。仪器主要技术指标（道间一致性、漂移、噪音、串音、误码率、主放台阶精度）可用微机进行检测,能满足地震测深和其它低频数字测量之用。 相似文献
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电磁法观测系统中,采样时钟质量直接影响高精度ADC的信噪比,而高精度ADC芯片的信噪比作为电磁法观测系统信号检测非常关键的指标,决定了获取数据的质量.采样时钟的时间抖动是时钟孔径不确定度产生的原因,导致电磁法观测系统中ADC数据转换的信噪比变差,严重影响电磁系统观测质量,为此提出了ADC采样时钟不确定度最大时间抖动的确定方法.该方法通过对ADC采样过程进行时域、频域分析,借助正弦波导数给出采样时钟孔径不确定度引起的采样数据误差数学描述,结合极大值法与ADC信噪比计算方法获取系统信噪比需求范围内的最差时钟孔径不确定度,进而计算出相应采样时钟的最大时间抖动误差.以地球物理仪器中常用的ADC芯片AD7760为例进行了相应的时钟抖动误差计算,确定时钟的孔径不确定度抖动时间.根据信噪比指标确定了时钟孔径不确定度后,采用压控恒温晶振跟踪GPS信号中的秒脉冲的方法,保证时钟抖动误差能够满足AD7760的要求,根据测试表明,在GPS失锁4 h内,时钟输出能够满足技术要求. 相似文献
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The effects of sample scheduling and sample numbers on estimates of the annual fluxes of suspended sediment in fluvial systems 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Since the 1970s, there has been both continuing and growing interest in developing accurate estimates of the annual fluvial transport (fluxes and loads) of suspended sediment and sediment‐associated chemical constituents. This study provides an evaluation of the effects of manual sample numbers (from 4 to 12 year?1) and sample scheduling (random‐based, calendar‐based and hydrology‐based) on the precision, bias and accuracy of annual suspended sediment flux estimates. The evaluation is based on data from selected US Geological Survey daily suspended sediment stations in the USA and covers basins ranging in area from just over 900 km2 to nearly 2 million km2 and annual suspended sediment fluxes ranging from about 4 Kt year?1 to about 200 Mt year?1. The results appear to indicate that there is a scale effect for random‐based and calendar‐based sampling schemes, with larger sample numbers required as basin size decreases. All the sampling schemes evaluated display some level of positive (overestimates) or negative (underestimates) bias. The study further indicates that hydrology‐based sampling schemes are likely to generate the most accurate annual suspended sediment flux estimates with the fewest number of samples, regardless of basin size. This type of scheme seems most appropriate when the determination of suspended sediment concentrations, sediment‐associated chemical concentrations, annual suspended sediment and annual suspended sediment‐associated chemical fluxes only represent a few of the parameters of interest in multidisciplinary, multiparameter monitoring programmes. The results are just as applicable to the calibration of autosamplers/suspended sediment surrogates currently used to measure/estimate suspended sediment concentrations and ultimately, annual suspended sediment fluxes, because manual samples are required to adjust the sample data/measurements generated by these techniques so that they provide depth‐integrated and cross‐sectionally representative data. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
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采用全集成化分频全电子讯号输出的方法，对５型钟进行了改造，达到了预期的效果。改造后的５型钟可提供时分秒同步电脉冲信号，时分号串行输出方式，使笔绘记录与光记录兼容。守时精度可达Ⅱ类台站用钟标准。 相似文献
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Reservoir 14C age offsets are invaluable tracers for past changes in carbon cycle and oceanic circulation. Reconstruction of reservoir age offsets with time is also required for calibration purposes (reconstruction of atmospheric calibration curve, calibration of non-atmospheric radiocarbon ages). Thus, properly propagating the various uncertainties linked to reservoir age offset is important for proper interpretation. However, approaches for reservoir age offset calculation – especially when considering pairs of reservoir-derived 14C and calendar ages – are usually not detailed and inadequate for proper propagation of uncertainties. Here, the various ways to properly calculate reservoir age offsets are described with a focus on a new approach when considering pairs of 14C and calendar ages. This approach maps the calendar age distribution onto the 14C time scale prior to reservoir age offset calculation – the “uncalibration-convolution process”. R codes computing reservoir age offsets based on available data are presented. Finally, a case study focusing on the reconstruction of the speleothem-atmosphere 14C age offsets of speleothem 14C data used in the latest release of the atmospheric calibration curve is discussed. 相似文献
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从江苏省数字地震台网2011年的宽频带记录数据中, 选取了不同背景噪声区域下的两组不同台间距的台站(A, B每组4个台站), 两组台站的平均台间距分别为44.6和30.5 km. 首先, 运用滑动窗互相关技术, 测量出各台站对间背景噪声互相关格林函数随时间的偏移量ΔDSi-Sj, 然后通过奇异值分解来求解由ΔDSi-Sj与系数矩阵构成的超定方程, 从而计算出单个台站的时钟误差ΔSi;并引入协方差矩阵来估计不同置信水平下计算结果的误差范围. 计算结果表明, 除去明显的钟差误差(>3 s)外, 8个台站的时间误差平均均方根为0.4215 s, A与B两组台站在置信水平为95%时的时间误差范围分别为±0.4544 s和±0.4283 s; 而采用HYPOSAT定位方法对2010—2011年江苏地区的地震进行定位, 得到的平均走时残差约为0.386 s. 两者的计算精度基本相当, 表明基于背景噪声互相关格林函数计算出的单台时间误差是可信的. 相似文献