现代变形监测技术的发展现状与展望   总被引：10，自引：7，他引：3  

卫建东 《测绘科学》2007,32(6):10-13

本文对现代变形监测技术从空间、地面、地下三个方面的最新发展入手,综述了各技术目前的应用现状,客观分析了测量机器人、GPS、三维激光扫描、光纤传感器、D-InSAR等技术在变形监测领域应用的特点、优势与不足。提出了随着现代通讯网络技术和G IS技术的发展,变形监测将逐步实现数据获取的自动化,监测设备多层次的集优化,变形数据分析与预警的信息化。  相似文献   

磁电传感器在数字摄影测量工作站中的应用   总被引：1，自引：0，他引：1  

王细检 《测绘科学》2007,32(2):147-148

目前国内各大测绘单位的航测内业成图软件大多数选用了全数字摄影测量工作站。磁电传感器应用于该工作站的脚踏开关系统,与以往的机械式脚踏开关系统相比,大大提高了数据采集的响应频率,成功地解决了数据采集过程中的重复采集,连点采集,漏采数据的问题。直接减轻了作业员,检验员,硬件维修人员工作量,从而大大提高了作业的效率。磁电传感器是一种非接触式传感器,它具有无触点、无开关瞬态抖动、响应频率高、低功耗、高可靠性和长寿命等特点。本文通过分析霍尔传感器件的原理,结合数字摄影测量工作站硬件设备的相关电路,给出了把霍尔传感器应用到数字摄影测量工作站脚踏开关系统中的具体方法。  相似文献   

Variability in the speciation of iron in the northern North Sea     

Martha Gledhill  Constant M. G. van den Berg  Rob F. Nolting  Klaas R. Timmermans 《Marine Chemistry》1998,59(3-4)

Variations in the speciation of iron in the northern North Sea were investigated in an area covering at least two different water masses and an algal bloom, using a combination of techniques. Catalytic cathodic stripping voltammetry was used to measure the concentrations of reactive iron (Fe_R) and total iron (Fe_T) in unfiltered samples, while dissolved iron (Fe_D) was measured by GFAAS after extraction of filtered sea water. Fe_R was defined by the amount of iron that complexed with 20 μM 1-nitroso-2-napthol (NN) at pH 6.9. Fe_T was determined after UV-digestion at pH 2.4. Concentrations of natural organic iron complexing ligands and values for conditional stability constants, were determined in unfiltered samples by titration. Mean concentrations of 1.3 nM for Fe_R, 10.0 nM for Fe_T and 1.7 nM for Fe_D were obtained for the area sampled. Fe_R concentrations increased towards the south of the area investigated, as a result of the increased influence of continental run off. Fe_R concentrations were found to be enhanced below the nutricline (below 40 m) as a result of the remineralisation of organic material. Enhanced levels of Fe_T were observed in some surface samples and in samples collected below 30 m at stations in the south of the area studied, thought to be a result of high concentrations of biogenic particulate material and the resuspended sediments respectively. Fe_D concentrations varied between values similar to those of Fe_T in samples from the north of the area to values similar to those of Fe_R in the south. The bloom was thought to have influenced the distribution of both Fe_R and Fe_T, but less evidence was observed for any influence on Fe_R and Fe_D. The concentration of organic complexing ligands, which could possibly include a contribution from adsorption sites on particulate material, increased slightly in the bloom area and in North Sea waters. Iron was found to be fully (99.9%) complexed by the organic complexing ligands at a pH of 6.9 and largely complexed (82–96%) at pH 8. The ligands were almost saturated with iron suggesting that the ligand concentration could limit the concentration of iron occurring as dissolved species.  相似文献   

Production of methyl bromide and methyl chloride in laboratory cultures of marine phytoplankton II     

M. G. Scarratt  R. M. Moore 《Marine Chemistry》1998,59(3-4)

Methyl halides (monohalomethanes), especially methyl bromide, are known to contribute significantly to ozone destruction in the stratosphere. Budgets of natural and anthropogenic methyl bromide suggest that marine organisms may be the source of a significant proportion of the total global production. Since phytoplankton are abundant in surface waters, they are obvious candidates. Cultures of nine phytoplankton species were grown in CO₂-enriched, nitrate-limited medium in sealed glass vessels. Species tested include Chaetoceros calcitrans, Isochrysis sp., Porphyridium sp., Synechococcus sp., Phaeodactylum tricornutum, Tetraselmis sp., Prorocentrum sp., Emiliania huxleyi and Phaeocystis sp. Methyl bromide (CH₃Br) and methyl chloride (CH₃Cl) concentrations were determined by bubbling the cultures with high-purity air, cryotrapping the effluent and analyzing it on a gas chromatograph with an electron capture detector. The Phaeocystis sp. samples were monitored with GCMS. Cell population, bacterial population, Chl a, pH, and nitrate concentration were monitored for periods of at least two weeks. CH₃Cl was produced by all cultures. CH₃Br was absent in Tetraselmis sp. and Isochrysis sp. cultures, but present in all the others. Methyl iodide (CH₃I) was present in most cultures but could not be quantified due to analytical limitations. CH₃I and CH₃Br production was fastest in stationary phase and continued long after cell division had ceased. Axeic cultures of Phaeocystis sp. achieved almost identical production rates of CH₃Cl and CH₃Br as xenic cultures of the same species. Species from tropical waters had faster CH₃Cl and CH₃Br production rates than temperate species. Scaling the observed production rates using global standing stock estimates for Chl a and particulate nitrogen indicate that phytoplankton can account for only a fraction of the CH₃Cl and CH₃Br believed to be produced in the ocean. Calculations based on the estimated global biomass of Phaeocystis sp. and E. huxleyi blooms show that their contribution is insignificantly small.  相似文献   

FZF2—3型海洋资料浮标传感器系统     

赵力 《海洋技术学报》1998,17(2):38-43

本文介绍了ＦＺＦ２－３型海洋资源浮标系统中各种传感器的技术性能指标、工作原理、构造特性及在海洋浮标系统中进行海洋监测工作中的应用情况。  相似文献   

Photogrammetric Capabilities of the Kodak DC40, DCS420 and DCS460 Digital Cameras     

A. Ahmad  & J. H. Chandler 《The Photogrammetric Record》1999,16(94):601-615

The aim of this study is to assess the impact of sensor size and resolution of different digital camera sensors upon the accuracy and precision of three dimensional data derived by photogrammetry. Kodak DC40, DCS420 and DCS460 digital cameras were used to produce digital images of retroreflective targets in a 4 m three dimensional test field. The image locations of the targeted points were automatically measured using an off the shelf image processing software package. Two different sub-pixel measurement approaches were examined: centre of gravity and weighted mean. From the automated sub-pixel measurement of the targeted points, results indicate that the high resolution DCS460 camera produces optimum results using either the weighted mean or centre of gravity approaches. Although this was perhaps expected, the far lower resolution DC40 camera performed better than was originally anticipated, suggesting potential for the cheaper DC40 for many applications.  相似文献   

Robust dual‐sensor data sea‐surface ghost attenuation for quality control purposes          下载免费PDF全文

Philippe Caprioli  Ralf Ferber 《Geophysical Prospecting》2018,66(5):954-963

Three‐dimensional receiver ghost attenuation (deghosting) of dual‐sensor towed‐streamer data is straightforward, in principle. In its simplest form, it requires applying a three‐dimensional frequency–wavenumber filter to the vertical component of the particle motion data to correct for the amplitude reduction on the vertical component of non‐normal incidence plane waves before combining with the pressure data. More elaborate techniques use three‐dimensional filters to both components before summation, for example, for ghost wavelet dephasing and mitigation of noise of different strengths on the individual components in optimum deghosting. The problem with all these techniques is, of course, that it is usually impossible to transform the data into the crossline wavenumber domain because of aliasing. Hence, usually, a two‐dimensional version of deghosting is applied to the data in the frequency–inline wavenumber domain. We investigate going down the “dimensionality ladder” one more step to a one‐dimensional weighted summation of the records of the collocated sensors to create an approximate deghosting procedure. We specifically consider amplitude‐balancing weights computed via a standard automatic gain control before summation, reminiscent of a diversity stack of the dual‐sensor recordings. This technique is independent of the actual streamer depth and insensitive to variations in the sea‐surface reflection coefficient. The automatic gain control weights serve two purposes: (i) to approximately correct for the geometric amplitude loss of the Z data and (ii) to mitigate noise strength variations on the two components. Here, Z denotes the vertical component of the velocity of particle motion scaled by the seismic impedance of the near‐sensor water volume. The weights are time‐varying and can also be made frequency‐band dependent, adapting better to frequency variations of the noise. The investigated process is a very robust, almost fully hands‐off, approximate three‐dimensional deghosting step for dual‐sensor data, requiring no spatial filtering and no explicit estimates of noise power. We argue that this technique performs well in terms of ghost attenuation (albeit, not exact ghost removal) and balancing the signal‐to‐noise ratio in the output data. For instances where full three‐dimensional receiver deghosting is the final product, the proposed technique is appropriate for efficient quality control of the data acquired and in aiding the parameterisation of the subsequent deghosting processing.  相似文献   

Monitoring litter interception of rainfall using leaf wetness sensor under controlled and field conditions   总被引：2，自引：0，他引：2       下载免费PDF全文

Bharat Sharma Acharya  Elaine Stebler  Chris B. Zou 《水文研究》2017,31(1):240-249

Leaf litter interception of water is an integral component of the water budget for some vegetated ecosystems. However, loss of rainfall to litter receives considerably less attention than canopy interception due to lack of suitable sensors to measure changes in litter water content. In this study, a commercially available leaf wetness sensor was calibrated to the gravimetric water content of eastern redcedar (Juniperus virginiana ) litter and used to estimate litter interception in a subhumid eastern redcedar woodland in north‐central Oklahoma. Under controlled laboratory conditions, a strong positive correlation between the leaf wetness sensor output voltage (mV) and measured gravimetric litter water content (? _g) was determined: ? _g = (.0009 × mV²) ? (0.14 × mV) ? 11.41 (R ² = .94, p  < .0001). This relationship was validated with field sampling and the output voltage (mV) accounted for 48% of the observed variance in the measured water content. The maximum and minimum interception storage capacity ranged between 1.16 and 12.04 and 1.12 and 9.62 mm, respectively. The maximum and minimum amount of intercepted rain was positively correlated to rainfall amount and intensity. The continuous field measurements demonstrated that eastern redcedar litter intercepted approximately 8% of the gross rainfall that fell between December 16, 2014 and May 31, 2015. Therefore, rainfall loss to litter can constitute a substantial component of the annual water budget. Long‐term in situ measurement of litter interception loss is necessary to gain a better estimate of water availability for streamflow and recharge. This is critical to manage water resources in the south‐central Great Plains, USA where grasslands are rapidly being transformed to woodland or woody dominated savanna.  相似文献   

RESEARCH ON PASSIVE SERVO SEISMIC ROTATIONAL ACCELERATION SENSOR WITH LARGE DAMPING          下载免费PDF全文

QU Ming-zhe  GAO Feng  YANG Xue-shan  YANG Dong-xia 《地震地质》2018,40(5):1170-1178

Many strong motion records show that under the strong seismic vibration of, the torsional disfigurement of building structures is a common and serious damage. At present, there are no special sensors for measuring seismic rotation in the world. Most of the experts obtain rotational components through observing deformation, theoretical analysis and calculation. The theory of elastic wave and source dynamics also prove the conclusion that the surface of the earth will rotate when an earthquake occurs. Based on a large number of investigations and experiments, a rotational acceleration sensor was developed for the observation of the rotational component of strong ground motions. This acceleration sensor is a double-pendulum passive servo large-damped seismic rotational acceleration sensor with the moving coil transducer. When an earthquake occurs, the seismic rotational acceleration acts on the bottom plate at the same time. The magnetic circuit system and the middle shaft fixedly connected to the bottom plate follow the bottom plate synchronous vibration, and the moving part composed of the mass ring, the swing frame and the moving ring produces relative corners to the central axis. The two working coils mounted on the two pendulums produce the same relative motion with respect to the magnetic gaps of the two magnetic circuits. Both working coils at this time generate an induced electromotive force by cutting magnetic lines of force in the respective magnetic gaps. The generated electromotive forces are respectively input to respective passive servo large damper dynamic ring transducer circuits and angular acceleration adjusting circuits, and the signals are simultaneously input to the synthesizing circuit after conditioning. Finally, the composite circuit outputs a voltage signal proportional to the seismic rotational acceleration to form a seismic rotational acceleration sensor. The paper presents the basic principles of the rotational acceleration sensor, including its mechanical structure diagram, circuit schematic diagram and mathematical models. The differential equation of motion and its circuit equation are derived to obtain the expressions of the main technical specifications, such as the damping ratio and sensitivity. The calculation shows that when the damping ratio is much larger than 1, the output voltage of the passive servo large damping dynamic coil transducer circuit is proportional to the ground rotation acceleration, and the frequency characteristic of bandpass is wider when the damping ratio is larger. Based on the calibration test, the dynamic range is greater than or equal to 100dB and the linearity error is less than 0.05%. The amplitude-frequency characteristics, the phase-frequency characteristics and their corresponding curves of the passive servo rotational acceleration sensor are acquired through the calculations. Based on the accurate measurement of the micro-vibration of the precision rotating vibration equipment, the desired result is obtained. The measured data are presented in the paper, which verify the correctness of the calculation result. The passive servo large damping rotational acceleration sensor has simple circuit design, convenient operation and high resolution, and can be widely applied to seismic acceleration measurement of earthquake or structure.  相似文献   

不锈钢纤维网对热压铁基预合金胎体抗冲击韧性的影响          下载免费PDF全文

孙吉伟  吴海霞  沈立娜  杨甘生 《探矿工程》2020,47(2):73-77

针对孕镶金刚石钻头在孔底钻进时受到各种冲击力而导致胎体出现裂纹甚至断裂的问题,提出了应用不锈钢纤维网提高胎体抗冲击韧性的方法。通过控制纤维网的摆放位置、目数和层数3个变量,测试了不同组合变量下的胎体抗冲击韧性。通过试验得到：（1）不锈钢纤维网能有效提高胎体的抗冲击韧性,而且X轴位置效果更好;（2）当纤维网的目数相同时,胎体抗冲击韧性随纤维网层数的增加而减小;（3）在纤维网层数相同的情况下,随着纤维网目数的增加,胎体抗冲击韧性呈现先增大后减小的趋势。当添加30目单层纤维网时,胎体的抗冲击韧性达到最大值。通过观察冲击断口、分析胎体断裂机理,解释了出现这种规律的原因,并提出了进一步优化胎体抗冲击韧性的方法。  相似文献