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Raman Spectra of AlP/GaP Short-period Superlattice ①②
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作者 GANRunjin ZHANGFujia 《Semiconductor Photonics and Technology》 CAS 1998年第4期243-247,共5页
The samples of (AlP) n /(GaP) n short-period superlattice (period number n =4,6) grown by MOVPE and the sample of n-GaP (100) single crystal substrate are measured and analyzed by Raman spectrum.In the thr... The samples of (AlP) n /(GaP) n short-period superlattice (period number n =4,6) grown by MOVPE and the sample of n-GaP (100) single crystal substrate are measured and analyzed by Raman spectrum.In the three kinds of samples,the double-phonon modes of first-order Raman scattering peaks are all existent.Moreover,the second-order Raman scattering peaks are observed to exist. 展开更多
关键词 AlP/GaP Raman Spectrum short-period SUPERLATTICE
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Investigation of the factors affecting the consistency of short-period traffic counts
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作者 Solomon Yadessa Kenno Prasanta K.Sahu +1 位作者 Babak Mehran Satish Sharma 《Journal of Modern Transportation》 2017年第3期150-162,共13页
The main intent of this study is to investigate the accuracy of short-duration traffic counts conducted during winter months. The investigation is based on 11-year sample data collected using permanent traffic counter... The main intent of this study is to investigate the accuracy of short-duration traffic counts conducted during winter months. The investigation is based on 11-year sample data collected using permanent traffic counters at various locations in Alberta, Canada. Four types of road sites: commuter, regional commuter, rural long-distance, and recreational sites are studied. The sample data consti- tute six different durations of counts (12-, 24-, 48-, 72-, 96-h, and 1 week) taken during summer and winter months. The coefficient of variation (CV) is used as the relative measure of deviation for counts of different dura- tions to measure the accuracy of short-period traffic counts. The study results indicate that 48-h count seems to be the most cost-effective counting interval during both summer and winter months. It is also found that the lowest values of CV result for counts taken at commuter sites, and the highest values are observed for recreational sites. Frequent changes in temperature and other weather events cause significant variation in traffic volume, which results in an increase in CV values for counts taken during winter months. The application of an adjustment factor to remove the effect of cold and snow from short-period counts is also included in this study. Introduced adjustment factors can reduce the values of CV for all counts taken during winter months. The findings of this study can lead highway agencies to improve the cost-effectiveness of their short- period traffic counting programs. 展开更多
关键词 short-period traffic counts Average annualdaily traffic - Design hourly volume
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Short-Term Orbit Prediction with J<sub>2</sub>and Mean Orbital Elements
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作者 Shraddha Gupta M. Xavier James Raj R. K. Sharma 《International Journal of Astronomy and Astrophysics》 2011年第3期135-146,共12页
An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in ... An analytical theory for calculating perturbations of the orbital elements of a satellite due to J2 to accuracy up to fourth power in eccentricity is developed. It is observed that there is significant improvement in all the orbital elements with the present theory over second-order theory. The theory is used for computing the mean orbital elements, which are found to be more accurate than provided by Bhatnagar and taqvi’s theory (up to second power in eccentricity). Mean elements have a large number of practical applications. 展开更多
关键词 Perturbation DUE to J2 Mean ORBITAL ELEMENTS short-periodic Terms Osculating ORBITAL ELEMENTS Fourth Power in Eccentricit
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The shallow Longmenshan crustal S-velocity structure of the fault zone using ambient noise tomography of a seismic dense array 被引量:5
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作者 Dandan Li Gaochun Wang +2 位作者 Ruihua Lin Kai Deng Xiaobo Tian 《Earthquake Science》 2019年第5期197-206,共10页
The Longmenshan fault zone(LMSF),characterized by complex structures and strong seismicity,is located at the junction between the eastern margin of the Tibetan Plateau and the north-western Sichuan basin.Since the Wen... The Longmenshan fault zone(LMSF),characterized by complex structures and strong seismicity,is located at the junction between the eastern margin of the Tibetan Plateau and the north-western Sichuan basin.Since the Wenchuan earthquake on May 12,2008,abundant studies of the formation mechanism of earthquakes along the LMSF were performed.In this study,a short-period dense seismic array deployed across the LMSF was applied by ambient noise tomography.Fifty-two 3-D seismic instruments were used for data acquisition for 26 days.We calculated the empirical Green's functions(EGFs)between different station-pairs and extracted 776 Rayleigh-wave dispersion curves between 2 and 7 s.And then,we used the direct-inversion method to obtain the fine shallow crustal S-wave velocity structure within 6 km depth in the middle section of the Longmenshan fault zone and nearby areas.Our results show that the sedimentary layer(>5 km)exists in the northwest margin of Sichuan Basin with a low S-wave velocity(~1.5-2.5 km/s)which is much thicker than that beneath the Longmenshan fault zone and the Songpan-Garze block.The high-velocity structures with clear boundaries below the middle of Longmenshan fault zone(~2-4 km)and the Songpan-Garze block(~4.5-6 km)probably reveal the NW-SE distribution patterns of both the Pengguan complex and the high-density belt hidden in the northwest of the Pengguan complex.And the obviously high-velocity anomalies observed at the depth of^1-2 km in the southeastern margin of the Songpan-Garze block can be considered as the Laojungou granites.Our results provide a high-resolution shallow velocity structure for detailed studies of the Longmenshan fault zone. 展开更多
关键词 Longmenshan fault zone ambient noise tomography S-wave velocity structure short-period dense seis-mic arrays
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Evaluating and correcting short-term clock drift in data from temporary seismic deployments 被引量:2
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作者 Aqeel Abbas Gaohua Zhu +2 位作者 Jinping Zi Han Chen Hongfeng Yang 《Earthquake Research Advances》 CSCD 2023年第2期24-38,共15页
Temporary seismic network deployments often suffer from incorrect timing records and thus pose a challenge to fully utilize the valuable data.To inspect and fix such time problems,the ambient noise cross-correlation f... Temporary seismic network deployments often suffer from incorrect timing records and thus pose a challenge to fully utilize the valuable data.To inspect and fix such time problems,the ambient noise cross-correlation function(NCCF)has been widely adopted by using daily waveforms.However,it is still challenging to detect the shortterm clock drift and overcome the influence of local noise on NCCF.To address these challenges,we conduct a study on two temporary datasets,including an ocean-bottom-seismometer(OBS)dataset from the southern Mariana subduction zone and a dataset from a temporary dense network from the Weiyuan shale gas field,Sichuan,China.We first inspect the teleseismic and local event waveforms to evaluate the overall clock drift and data quality for both datasets.For the OBS dataset,NCCF using different time segments(3,6,and 12-h)beside daily waveforms data is computed to select the data length with optimal detection capability.Eventually,the 6-h segment is the preferred choice with high detection efficiency and low noise level.For the land dataset,higher drift detection is achieved by NCCF using the daily long waveforms.Meanwhile,we find that NCCF symmetry on the dense array is highly influenced by localized intense noise for large interstation distances(>1 km)but is well preserved for short interstation distances.The results have shown that the use of different segments of daily waveform data in the OBS dataset,and the careful selection of interstation distances in the land dataset substantially improved the NCCF results.All the clock drifts in both datasets are successfully corrected and verified with waveforms and NCCF.The newly developed strategies using short-segment NCCF help to overcome the existing issues to correct the clock drift of seismic data. 展开更多
关键词 OBS and Land dataset short-period clock drift Waveforms inspection Ambient noise cross-correlation
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Precontrol of short-period motion for a Tension Leg Platform
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作者 Hao Wu Yan Lin Yongxi Wu 《Journal of Ocean Engineering and Science》 SCIE 2024年第3期264-277,共14页
The Tension Leg Platform(TLP)is a hybrid,compliant platform designed to sustain springing and ringing responses that are correlated to short-period motion.Since the period of short-period motion is within the wave ene... The Tension Leg Platform(TLP)is a hybrid,compliant platform designed to sustain springing and ringing responses that are correlated to short-period motion.Since the period of short-period motion is within the wave energy concentration region,TLPs may experience sensitive short-period motion,such as resonance and green water,that usually cause serious damage to TLPs.In this study,a precontrol methodology is presented as a solution to prevent TLP-sensitive short-period motion.By applying the precontrol methodology,the parameters of TLP can be predetermined,allowing TLP motion performance to meet the requirements of short-period motion before sensitive motions actually occur.For example,the damping coefficient should be less than 4.3,the tendons’stiffness should be larger than 0.91×10^(8),and the dimensionless draft should be less than 0.665.The development of a precontrol methodology is based on a solid theoretical foundation.First,a series of simple and high-fidelity numerical models are proposed to simulate the natural period of roll,natural period of heave,and green water height.Second,a constraint regime is generated based on the numerical models and the sensitive motion range of short-period motion.The constraint regime is divided into two parts:the control range(corresponding to sensitive shortperiod motion)and the feasible range(the complementary set of control ranges in the whole parameter constraint domain).Finally,TLP parameters are derived from the calculated feasible range.The precontrol methodology goes beyond the conventional approach of real-time control by changing the control from a remedial action to a preventive action. 展开更多
关键词 Precontrol Constraint regime short-period motion TLP
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Cenozoic magmatic activity and oblique uplifting of the Ailao Mountain: Evidence from a short-period dense seismic array 被引量:2
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作者 Lu ZHANG Zhiming BAI +5 位作者 Tao XU Zhenbo WU Minfu HUANG Guiping YU Junlei CHEN Mengjie ZHENG 《Science China Earth Sciences》 SCIE EI CAS CSCD 2020年第9期1294-1308,共15页
Geological studies show that the southern part of Ailaoshan-Red River shear zone(ALSRRSZ)has experienced complex metallogenic processes and multi-stage non-uniform uplifting,called oblique uplifting since the Cenozoic... Geological studies show that the southern part of Ailaoshan-Red River shear zone(ALSRRSZ)has experienced complex metallogenic processes and multi-stage non-uniform uplifting,called oblique uplifting since the Cenozoic.To detect the deep structure and geodynamic background beneath Daping,Chang’an and other gold and polymetallic deposits in this area,we carried out a high-density short-period seismic array survey in southern Yunnan province.The array used is approximately240 km long with an interval of 500 m between two adjacent stations.Based on the data collected by the array,we used H-κstacking and common conversion point(CCP)methods of receiver functions to reveal the fine crustal structure beneath this array,which was located from Lvchun(western end)to the east and ended in Maguan.The three main conclusions are as follows.(1)The average crustal thickness is approximately 37 km and the Vp/Vsratio is 1.75.However,the thickness and Vp/Vsratio of the Ailao Mountain are rather greater or higher than those of the western Lanping-Simao Basin and eastern South-China block.These results may indicate that the crust is rich in ferromagnesian minerals or has a thermal fluid anomaly after orogenic movement.(2)There are two obvious inclined interfaces beneath the Ailao Mountain in the mid-upper crust,which suggests that strong deformation occurred there during the orogenic period.Some evidences,such as the weak converted-wave Pms phase from the Moho,low P-wave velocities of the upper mantle,high surface heat flow values,and generally developed hot springs,indicate that a strong crust-mantle interaction exists in the southern segments of the Ailaoshan-Red River shear zone.These interactions include a diapir of mantle-sourced magma(stronger in the east than that in the west),lateral collision from the Indian Plate,and the differential uplift caused by the strike-slip movement of the Red River Fault.All of above deep processes led to the Cenozoic oblique uplifting of Ailao Mountain.(3)By combining the location of the deposits on the surface,characteristics of the average crustal Vp/Vsratio,hypocenters of the small earthquakes along the research profile,Moho shape,and horizontal variations of the Pms phase amplitudes,we speculate that the Ailaoshan Fault was the upgoing conduit for metallogenic magma and played a significant role in the Cenozoic development of the multiform metal deposits around the Ailao Mountain area. 展开更多
关键词 Ailaoshan-Red River shear zone Multiform metal deposits Oblique uplifting short-period dense seismic array Receiver function
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Remnants of the amalgamation of the east and west Cathaysia blocks revealed by a short-period dense nodal array 被引量:1
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作者 He Huang Xuzhang Shen +4 位作者 Jian Xu Rui Gao Wentian Wang Qiming Zhou Qiangqiang Huang 《Geoscience Frontiers》 SCIE CAS CSCD 2023年第1期207-214,共8页
The Cathaysia block located at the southeast South China block(SCB)is considered formed by the amalgamation of the east and west Cathaysia blocks along the Gaoyao-Huilai and Zhenghe-Dapu deep faults(here referred as G... The Cathaysia block located at the southeast South China block(SCB)is considered formed by the amalgamation of the east and west Cathaysia blocks along the Gaoyao-Huilai and Zhenghe-Dapu deep faults(here referred as GHF and ZDF,respectively).Although the extension of the ZDF to the northeast,which represents the amalgamation of the two sub-blocks has been confirmed,the development of the GHF to the southwest remains to be verified.To better constrain the detailed deep structure beneath the southwest Cathaysia,which hold great significance for revealing the evolution of the SCB,a linear seismic array with 331 nodal geophones was deployed across the Sanshui basin(SSB).Combining with the regional 10 permanent stations(PA),we obtained two profiles with teleseismic P-wave receiver function stacking.The most obvious feature in our results is the ascending Moho towards the coastal area,which is consistent with the passive margin continental and extensional tectonic setting.The stacking profile from the dense nodal array(DNA)shows that the Moho is offset beneath the transition zone of the Nanling orogeny and SSB.We deduce that this offset may be casued by the deep extension of the GHF,which represents the remnants of the amalgamation of the Cathaysia block.From the other evidences,we infer that the widespread and early erupted felsic magmas in the SSB may have resulted from lithospheric materials that were squeezed out to the surface.The relative higher Bouguer gravity and heat flow support the consolidation of magmas and the residual warm state in the shallow crustal scale beneath the SSB.The sporadic basaltic magmas in the middle SSB may have a close relation to deep extension of the GHF,which serves as a channel for upwelling hot materials. 展开更多
关键词 Dense short-period nodal array Teleseismic receiver function Cathaysia block Offset Moho High V_(p)/V_(s)ratio
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Measurement of ice flow velocities from GPS positions logged by short-period seismographs in East Antarctica
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作者 Lei FU Jingxue GUO Xiaofei CHEN 《Science China Earth Sciences》 SCIE EI CSCD 2021年第8期1381-1389,共9页
The ice flow velocity is a basic feature of glaciers and ice sheets. Measuring ice flow velocities is very important for estimating the mass balance of ice sheets in the Arctic and Antarctic. Traditional methods for m... The ice flow velocity is a basic feature of glaciers and ice sheets. Measuring ice flow velocities is very important for estimating the mass balance of ice sheets in the Arctic and Antarctic. Traditional methods for measuring ice flow velocity include the use of stakes, snow pits and on-site geodetic GPS and remote sensing measurement methods. Geodetic GPS measurements have high accuracy, but geodetic GPS monitoring points only sparsely cover the Antarctic ice sheets. Moreover, the resolution and accuracy of ice flow velocities based on remote sensing measurements are low. Although the accuracy of the location data recorded by the navigation-grade GPS receivers embedded in short-period seismographs is not as good as that of geodetic GPS,the ice flow velocity can be accurately measured by these navigation-grade GPS data collected over a sufficiently long period. In this paper, navigation-grade GPS location data obtained by passive seismic observations during the 36 th Chinese National Antarctic Research Expedition were used to accurately track the movement characteristics of the ice sheet in the Larsemann Hills of East Antarctica and the Taishan Station area. The results showed that the ice sheet in the two study areas is basically moving northwestward with an average ice flow velocity of approximately 1 m mon-1. The results in the Taishan Station area are basically consistent with the geodetic GPS results, indicating that it is feasible to use the embedded GPS location data from shortperiod seismographs to track the movement characteristics of ice sheets. The ice flow characteristics in the Larsemann Hills are more complex. The measured ice flow velocities in the Larsemann Hills with a resolution of 200 m help to understand its characteristics. In summary, the ice flow velocities derived from GPS location data are of great significance for studying ice sheet dynamics and glacier mass balance and for evaluating the systematic errors caused by ice sheet movements in seismic imaging. 展开更多
关键词 short-period seismograph Antarctic ice sheet Ice flow velocity GPS
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