Attitude estimation based on fusion of gyroscopes and single antenna GPS for small UAVs under the influence of vibration   总被引：4，自引：2，他引：2  

Ying-Chih Lai  Shau-Shiun Jan 《GPS Solutions》2011,15(1):67-77

An attitude estimation method is presented for small unmanned aerial vehicles (UAVs) powered by a piston engine which is the major source of vibration. Vibration of the engine significantly degrades the accuracy of the inertial measurement unit, especially for low-cost sensors that are based on micro electro-mechanical system. Therefore, a vibration model for a small UAV is proposed in order to examine the influence of vibration on attitude estimation with different sensors. The model is derived based on spectrum analysis with short-time Fourier transform. The vibration is compared with the drift of the gyroscope in order to examine the impact on attitude estimation. An attitude estimation method that fuses the gyroscopes and single antenna global positioning system (GPS) is proposed to mitigate the influence of engine vibration and gyroscope drift. The quaternion-based extended Kalman filter is implemented to fuse the sensors. This filter fuses the angular rates measured by the gyroscopes and the pseudo-attitude derived from the GPS velocity to estimate the attitude of the UAV. Simulations and experiment results indicate that the proposed method performs well both in short-term and long-term accuracy even though the gyroscopes are affected by drift and vibration noise, while the pseudo-attitude contains severe noise.  相似文献   

Major human Hepatitis A virus genotype in Hong Kong marine waters and detection by real-time PCR     

Yang N  Chu DL  Wong MM  Qi H  Wu RS  Kong RY 《Marine pollution bulletin》2011,62(12):2654-2658

Marine waters from seven sites around Hong Kong with varying levels of sewage pollution were analyzed for Hepatitis A virus (HAV) by PCR cloning and DNA sequencing of the highly variable VP1/2A junction of the HAV genome. Phylogenetic analysis of 10 PCR clones from each of the HAV-positive marine sites indicated that human HAV genotype IB is the most widely distributed type in Hong Kong waters. A sensitive and quantitative TaqMan-based PCR method targeting the 5′-noncoding region (5′-NCR) of HAV was used to quantify HAV particles in marine water samples along with the total Escherichiacoli counts being enumerated on TBX medium for comparison. Our results showed that no correlation of any significance between HAV and E. coli counts was observed which underscores the inadequacy in using E. coli as a sanitary standard to predict the levels of HAV in marine waters.  相似文献   

Stochastic 1D site response analysis at a site in central Italy     

M. Rota  C.G. Lai  C.L. Strobbia 《Soil Dynamics and Earthquake Engineering》2011

Site response analysis is strongly influenced by the uncertainty associated to the definition of soil properties and model parameters. Deterministic, or even parametric analyses are unable to systematically assess such uncertainty, since the site characterisation can hardly be sufficiently accurate for a deterministic prediction of site response and alternative approaches are hence needed. A fully stochastic procedure for estimating the site amplification of ground motion is proposed and applied to a case study in central Italy. The methodology allows to take into account the record-to-record variability in an input ground motion and the uncertainty in dynamic soil properties and in the definition of the soil model. In particular, their effect on response spectra at the ground surface is evaluated.  相似文献   

西藏尤卡朗铅银矿床流体包裹体研究   总被引：1，自引：0，他引：1       下载免费PDF全文

王涛  赖健清  冯志兴  宋学军 《地质科学》2011,46(2):549-558

西藏尤卡朗铅银矿床位于班公湖-怒江结合带以南、雅鲁藏布江结合带以北的冈底斯-念青唐古拉山中生代岩浆弧.矿区的含矿地层为上侏罗统拉贡塘组顶部的石英岩层,矿体受到裂隙构造控制.含矿脉体的石英中发现两类流体包裹体,即Ⅰ型水溶液包裹体和Ⅱ型H2O-CO2包裹体,均-温度为160℃～250℃,推测成矿温度为中温.流体盐度范围为1...  相似文献   

特提斯喜马拉雅带江孜地区古近纪地层源区分析——对造山带早期地壳加厚的制约   总被引：1，自引：0，他引：1  

蔡福龙  丁林  王厚起  岳雅慧  来庆洲 《地质科学》2013,48(2):435-448

特提斯喜马拉雅北亚带江孜地区上古新统-下始新统甲查拉组记录了喜马拉雅碰撞造山带的早期地壳加厚和沉积历史。本文我们报道了甲查拉组详细的碎屑锆石U-Pb年龄和全岩Sm-Nd同位素数据。甲查拉组由青灰色厚层的岩屑砂岩夹泥岩组成,不整合覆盖在宗卓组之上,碎屑锆石主要的峰值介于350～80 Ma, 900～470 Ma以及1 300～950 Ma,次要的峰值介于2 800～1 500 Ma。全岩⁸⁷Sr/⁸⁶Sr介于0.707 505～0.713 174,¹⁴³Nd/¹⁴⁴Nd介于0.512 206～0.512 355,ε_Nd(0)介于-5.52～-8.43。甲查拉组物源区以再循环的日喀则弧前盆地和上三叠统郎杰学群为主,少量物质来自雅鲁藏布江缝合带。上述研究表明,甲查拉组沉积在周缘前陆盆地的背景下,且特提斯喜马拉雅北亚带在始新世期间经历了明显的地壳加厚。  相似文献   

Removal of 2,4-dichlorophenol and pentachlorophenol from aqueous media by electrochemical process     

Jui-Yuan Huang  Wing-Ping Liao  Siou-Mei Lai 《Environmental Earth Sciences》2013,68(8):2281-2288

Chlorophenols are persistent toxins in the natural environment. In this investigation, 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) in aqueous media were degraded using an electrokinetic process (EK) and an electro-Fenton process (EF) using stainless steel and graphite as the anode and cathode, respectively. Chlorophenols were degraded via direct electrolysis at the surface of the electrode in the EK process. However, in the EF process, the degradation mechanism includes direct electrolysis and oxidation by hydroxyl radicals. The optimal conditions were a current density of 0.75 mA/cm² and an air flow of 0.7 l/min at pH 4. Under the optimal conditions, the 2,4-DCP and PCP removal rates in the EF process were 80.18 and 64.03 %, respectively. The mineralization efficiencies of 2,4-DCP and PCP were 78.23 and 75.77 %, respectively. The results of dechlorination reveal that almost all of the chlorines were released, but some were retained in the intermediates. The dechlorination efficiency revealed that the EF and EK4 processes two chlorines from 2,4-DCP. They released four or five chlorines and four chlorines from PCP, respectively. The kinetic results provide evidence of pseudo-first degradation. The rate constant (k _cp) declined as pH_i was increased from 4 to 10. The k _cp values reveal that the pH is an important factor that affects the degradation efficiency in the electrochemical process.  相似文献   

Analysis of earthquake ground motions using an improved Hilbert–Huang transform     

Dong Yinfeng  Li Yingmin  Xiao Mingkui  Lai Ming 《Soil Dynamics and Earthquake Engineering》2008,28(1):7-19

Some limitations of the Hilbert–Huang transform (HHT) for nonlinear and nonstationary signal processing are remarked. As an enhancement to the HHT, a time varying vector autoregressive moving average (VARMA) model based method is proposed to calculate the instantaneous frequencies of the intrinsic mode functions (IMFs) obtained from the empirical mode decomposition (EMD) of a signal. By representing the IMFs as time varying VARMA model and using the Kalman filter to estimate the time varying model parameters, the instantaneous frequencies are calculated according to the time varying parameters, then the instantaneous frequencies and the envelopes derived from the cubic spline interpolation of the maxima of IMFs are used to yield the Hilbert spectrum. The analysis of the length of day dataset and the ground motion record El Centro (1940, N–S) shows that the proposed method offers advantages in frequency resolution, and produces more physically meaningful and readable Hilbert spectrum than the original HHT method, short-time Fourier transform (STFT) and wavelet transform (WT). The analysis of the seismic response of a building during the 1994 Northridge earthquake shows that the proposed method is a powerful tool for structural damage detection, which is expected as the promising area for future research.  相似文献   

Magma mingling in the Tungho area,Coastal Range of eastern Taiwan     

Yu-Ming Lai  Sheng-Rong Song  Yoshiyuki Iizuka 《Journal of Volcanology and Geothermal Research》2008

Complex rocks, consisting of different lithologic breccias and sediments in the Tungho area of the southern Coastal Range, eastern Taiwan, were formed by magmas and magma–sediment mingling. Based on field occurrences, petrography, and mineral and rock compositions, three components including mafic magma, felsic magma, and sediments can be identified. The black breccias and white breccias were consolidated from mafic and felsic magma, respectively. Isotopic composition shows these two magmas may be from the same source. Compared to the white breccias, the black breccias show clast-supported structures, higher An values in plagioclase, higher contents of MgO, CaO, and Fe₂O₃ and lower SiO₂, greater enrichment in the light rare earth elements (LREE), and depletion in the heavy rare earth elements (HREE). The white breccias show matrix-supported blocks and mingling with tuffaceous sediments to form peperite. Physical and chemical evidence shows that the characteristics of these two components (mafic and felsic magmas) are still apparent in the mingled zone. According to their petrography, mafic and felsic magmas did not have much time for mingling. White intrusive structures and black flow structures show that mingling occurred before they solidified. Finally, the occurrence of mingling between magmas and sediments suggests that the mingling has taken place at the surface and not in the magma chamber.  相似文献   

煤层处置CO2 的二元气- 固耦合数值模拟   总被引：2，自引：0，他引：2  

冯启言  周来  陈中伟  刘继山 《高校地质学报》2009,15(1):63

利用不可开采煤层处置二氧化碳可以有效控制温室气体的排放量并可驱动和增加煤层气资源的开采量。二氧化碳注入煤层处置后引入一个复杂的CH4-CO2二元气体与煤体的气固耦合问题,耦合了二元气体竞争吸附、竞争扩散,气体渗流以及煤体变形过程。基于COMSOL Multiphysics建立了二元气固耦合的有限元数值模型,并应用数值模拟实验对二元气固耦合进行了机理分析。模拟结果表明,CO2注入煤层后不断驱替CH4,CH4组分明显减少;气体吸附引起的煤层膨胀量可以抵消部分有效应力引起的压缩变形,由于CH4-CO2二元气体较单一CH4引起的煤层吸附膨胀量大,二氧化碳注入煤层后可以缓解煤层的压缩变形;不同孔隙压力条件下,吸附膨胀与孔隙压力两者竞争作用引起的煤层净变形不同,而净变形也控制着煤层孔隙压力和渗流率的变化,煤层渗透整体呈现先降后升,模拟进行到4.66×107 s时煤层渗透率发生反弹。  相似文献   

A Preliminary Interpretation of Near-field Observation Data of the Zhangbei Earthquake     

Shi Jinhu  Lai Xiaoling  Duan Yonghong  Li Songlin  Zhang Xiankang  Song Zhanlong  Yang Jian 《中国地震研究》2000,14(2):179-187

In this paper, a preliminary data processing was made for tbe aftershock records or theZhangbei M6.2 earthquake on Jan. 10, 1998. The hypocenters of 205 earthquakes with M_L≥0.5 were located. The result shows that most aftershockS were concentrated in a more than10 km long and 5～8 km wide NE-trending beIt. The source mechanism solutions of largeraftersbocks were also calculated, from which it can be inferred that the faulted zone of themain shock is an NE-trending fault. Furthermore, the spectral analysis of P waves was made.The corner frequency is about 10 Hz.  相似文献