Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies ...Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies only focused on the acoustic property of a free drill string and neglected the coupling between pipes and fluid-filled boreholes.In addition to the drill-string waves,a series of fluid waves are recorded in the DAT channel,which has not been investigated yet.Unpredictable channel characteristics result in lower transmission rates and stability than expected.Therefore,a more realistic channel model is needed considering the fluid-filled borehole.In this paper,we propose a hybrid modeling method to investigate the response characteristics of the DAT channel.By combining the axial wavenumbers and excitation functions of mode waves in radially layered LWD structures,the channel model is approximated to the 1-D propagation,which considers transmission,reflection,and interconversion of the drillstring and fluid waves.The proposed 1-D approximation has been well validated by comparing the 2-D finite-difference modeling.It is revealed that the transmitted and converted fluid waves interfere with the drill-string wave,which characterizes the DAT channel as a particular coherent multi-path channel.When a fluid-filled borehole surrounds the drill string,the channel responses exhibit considerable delay as well as strong frequency selectivity in amplitude and phase.These new findings suggest that the complexity of the channel response has been underestimated in the past,and therefore channel measurements on the ground are unreliable.To address these channel characteristics,we apply a noncoherent demodulation strategy.The transmission rate for synthetic data reaches 15 bps in a 94.5 m long channel,indicating that the acoustic telemetry is promising to break the low-speed limitation of mud-pulse telemetry.展开更多
Modeling of a drill-string acoustic channel has been an important topic in downhole telemetry for a long time.The propagation of drill-string guided waves in the borehole contains excitation,attenuation,and mode conve...Modeling of a drill-string acoustic channel has been an important topic in downhole telemetry for a long time.The propagation of drill-string guided waves in the borehole contains excitation,attenuation,and mode conversion issues that have not been considered by existing modeling methods.In this article,we formulate a hybrid modeling method to investigate the response characteristics of a fundamental-mode drill-string wave in various borehole environments.This hybrid method provides channel functions,including transmitting and receiving deployments,periodicity of the structure,and formation property changes.The essential physics of the drill-string wave propagation is captured with a one-dimensional model.The analytical solutions of the wavefield in multilayered cylindrical structures are introduced into a propagation matrix to express drill-string-wave interactions with the borehole environments.The effectiveness of the proposed method is confirmed through comparison with the finite-difference method.In addition,by designing numerical models,we investigate the conversion effect of the drill-string wave at the tool joint.We demonstrate that the conversion intensity of the drill-string wave is positively correlated not only with the cross-sectional area of the tool joint but also with the wave impedance of the outer formation.Hard formation outside the borehole reduces the energy leakage while intensifying the conversion of drill-string waves to Stoneley waves,and the opposite is true for the drill string in an infinite fluid.The converted Stoneley waves interfere with the drill-string waves,resulting in variations of bandgap distribution,which challenges the reliability of the data transmission.展开更多
In the Ethernet lossless Data Center Networks (DCNs) deployedwith Priority-based Flow Control (PFC), the head-of-line blocking problemis still difficult to prevent due to PFC triggering under burst trafficscenarios ev...In the Ethernet lossless Data Center Networks (DCNs) deployedwith Priority-based Flow Control (PFC), the head-of-line blocking problemis still difficult to prevent due to PFC triggering under burst trafficscenarios even with the existing congestion control solutions. To addressthe head-of-line blocking problem of PFC, we propose a new congestioncontrol mechanism. The key point of Congestion Control Using In-NetworkTelemetry for Lossless Datacenters (ICC) is to use In-Network Telemetry(INT) technology to obtain comprehensive congestion information, which isthen fed back to the sender to adjust the sending rate timely and accurately.It is possible to control congestion in time, converge to the target rate quickly,and maintain a near-zero queue length at the switch when using ICC. Weconducted Network Simulator-3 (NS-3) simulation experiments to test theICC’s performance. When compared to Congestion Control for Large-ScaleRDMA Deployments (DCQCN), TIMELY: RTT-based Congestion Controlfor the Datacenter (TIMELY), and Re-architecting Congestion Managementin Lossless Ethernet (PCN), ICC effectively reduces PFC pause messages andFlow Completion Time (FCT) by 47%, 56%, 34%, and 15.3×, 14.8×, and11.2×, respectively.展开更多
BACKGROUND Inpatient telemetry heart rhythm monitoring overuse has been linked to higher healthcare costs.AIM To evaluate if CHA2DS2-VASc score could be used to indicate if a patient admitted with possible cerebrovasc...BACKGROUND Inpatient telemetry heart rhythm monitoring overuse has been linked to higher healthcare costs.AIM To evaluate if CHA2DS2-VASc score could be used to indicate if a patient admitted with possible cerebrovascular accident(CVA)or transient ischemic attack(TIA)requires inpatient telemetry monitoring.METHODS A total of 257 patients presenting with CVA or TIA and placed on telemetry monitoring were analyzed retrospectively.We investigated the utility of telemetry monitoring to diagnose atrial fibrillation/flutter and the CHA2DS2-VASc scoring tool to stratify the risk of having CVA/TIA in these patients.RESULTS In our study population,63(24.5%)of the patients with CVA/TIA and telemetry monitoring were determined to have no ischemic neurologic event.Of the 194(75.5)patients that had a confirmed CVA/TIA,only 6(2.3%)had an arrhythmia detected during their inpatient telemetry monitoring period.Individuals with a confirmed CVA/TIA had a statistically significant higher CHA2DS2-VASc score compared to individuals without an ischemic event(3.59 vs 2.61,P<0.001).CONCLUSION Given the low percentage of inpatient arrhythmias identified,further research should focus on discretionary use of inpatient telemetry on higher risk patients to diagnose the arrhythmias commonly leading to CVA/TIA.A prospective study assessing event rate of CVA/TIA in patients with higher CHA2DS2-VASc score should be performed to validate the CHA2DS2-VASc score as a possible risk stratifying tool for patients at risk for CVA/TIA.展开更多
随着5G技术和物联网的发展,越来越多的终端设备被黑客利用发起分布式拒绝服务(distributed denial of service,DDoS)攻击。为了解决传统DDoS攻击检测技术检测时效性慢、检出率低、需要手动配置和人工干预的问题,对telemetry技术和深度...随着5G技术和物联网的发展,越来越多的终端设备被黑客利用发起分布式拒绝服务(distributed denial of service,DDoS)攻击。为了解决传统DDoS攻击检测技术检测时效性慢、检出率低、需要手动配置和人工干预的问题,对telemetry技术和深度学习技术进行研究,提出基于telemetry技术的智能化DDoS检测方法,以期为相关人员或工程提供参考。展开更多
A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into correspon...A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into corresponding voltage signal by the thermo-couple first. Then after the V/F stage, the voltage signal is converted into the frequency signal to drive the infrared light-emitting diode to transmit infrared pulses. At the receiver end, a photosensitive audion receives the infrared pulses. After conversion, the voltage recorded by the receiver stands for the magnitude of temperature at the measuring point. Test results of the system indicate that the system is practical and the system can perform multipoint looping temperature measurements for the piston.展开更多
While several studies have documented the large-scale, seasonal movements of horseshoe crabs, little is known about their fine-scale, daily movement patterns. In this study we used a fixed array ultrasonic telemetry s...While several studies have documented the large-scale, seasonal movements of horseshoe crabs, little is known about their fine-scale, daily movement patterns. In this study we used a fixed array ultrasonic telemetry system to track the movements of 12 male and 16 female horseshoe crabs in the Great Bay estuary, New Hampshire. Data were obtained during the mating season, as well as during the remainder of the summer and fall, in the years 2005-2008. During the mating season animals were often, but not always, active during the high tides when they were approaching and leaving the spawning beaches. On average, both males and females approached mating beaches during 33% of the high tides they experienced and they most often made the tran- sition from being inactive to active during the last two hours of an incoming tide. From April-October horseshoe crabs were significantly more active during high tide periods vs low tide periods, with no clear preference for diurnal vs nocturnal activity. After the mating season ended horseshoe crabs continued to move into shallower water at high tide and then return to deeper water at low tide. Observations by SCUBA divers suggest that during these excursions into the mudflats horseshoe crabs were digging pits in the sediment while foraging for food. Thus, the tidal rhythm of activity that has been so well documented during the mating season probably persists into the fall, and primarily involves foraging activities展开更多
American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in a semi-enclosed bay on Cape Cod （Pleasant Bay）, Massachusetts, USA, to determine seasonal movement pattern...American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in a semi-enclosed bay on Cape Cod （Pleasant Bay）, Massachusetts, USA, to determine seasonal movement patterns. Fifty-five actively spawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008 through July 2010. Fil^een crabs with transmitters also had archive depth-temperature tags attached. In addition, over 2000 spawning crabs （males and females） were tagged with US Fish and Wildlife CIdSFWS） button tags over the same period. Ninety-one percent of the crabs with transmitters were detected during this study. In the spring, crabs were primarily located in the northern section of the bay near spawning beaches, whereas in the fall crabs moved towards the deeper portions of the bay, and some may have overwIntered in the bay. There was evidence that a majority （58%-71%） of the females with transmitters spawned in two sequential seasons. One archive tag was recovered resulting in a year-long continuous record of depth and tem- perature data that, when integrated with telemetry data, indicated that the crab overwintered in the bay. The live recapture rate of crabs with USFWS button tags was 11%, with all re-sighted crabs except one observed inside Pleasant Bay. Eighty-three percent of recaptures were found within 2.5kin of the tagging location, and 51% were observed at the same beach where they were tagged. This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this embayment展开更多
AIM:To determine if there were any interactions between cardiac devices and small bowel capsules secondary to electromagnetic interference (EMI) in patients who have undergone small bowel capsule endoscopy (SBCE).METH...AIM:To determine if there were any interactions between cardiac devices and small bowel capsules secondary to electromagnetic interference (EMI) in patients who have undergone small bowel capsule endoscopy (SBCE).METHODS:Authors conducted a chart review of 20 patients with a cardiac pacemaker (CP) or implantable cardioverter defibrillator (ICD) who underwent continuous electrocardiographic monitoring during their SBCE from 2003-2008.authors searched for unexplained electrocardiogram (ECG) findings,changes in CP andICD set parameters,any abnormality in transmitted capsule data,and adverse clinical events.RESULTS:There were no adverse events or hemodynamically significant arrhythmias reported.CP and ICD set parameters were preserved.The majority of ECG abnormalities were also found in pre-or post-SBCE ECG tracings and the CP behavior during arrhythmias appeared appropriate.Two patients seemed to have episodes of undersensing by the CP.However,similar findings were documented in ECGs taken outside the time frame of the SBCE.One patient was observed to have a low signal encountered from the capsule resulting in lack of localization,but no images were lost.CONCLUSION:Capsule-induced EMI remains a possibility but is unlikely to be clinically important.CPinduced interference of SBCE is also possible,but is infrequent and does not result in loss of images transmitted by the capsule.展开更多
To study horseshoe crab Limulus polyphemus spawning behavior and migration over a large-spatial extent （〉100 km）, we arrayed fixed station radio receivers throughout Delaware Bay and deployed radio transmitters and...To study horseshoe crab Limulus polyphemus spawning behavior and migration over a large-spatial extent （〉100 km）, we arrayed fixed station radio receivers throughout Delaware Bay and deployed radio transmitters and archival tags on adult horseshoe crabs prior to their spawning season. We tagged and released 160 females and 60 males in 2004 and 217 females in 2005. The array covered approximately 140 km of shoreline. Recapture rates were 〉70% with multi-year recaptures. We categorized adult age by carapace wear. Older females tended to spawn earlier in the season and more frequently than young females, but those tendencies were more apparent in 2004 when spawning overall occurred earlier than in 2005 when spawning was delayed possibly due to decreased water temperatures. Timing of initial spawning within a year was correlated with water temperature. After adjusting for day of first spring tide, the day of In＇st spawning was 4 days earlier for every 1 degree （℃） rise in mean daily water temperature in May. Seventy nine % of spawning occurred during nighttime high tides. Fifty five % of spawning occurred within 3 d of a spring tide, which was slightly higher than the 47% expected if spawning was uniformly distributed regardless of tidal cycle. Within the same spawning season, males and females were observed spawning or intertidally resting at more than one beach separated by 〉5 kin. Between years, most （77%） did not return to spawn at the same beach. Probability of stranding was strongly age dependent for males and females with older adults experiencing higher stranding rates. Horseshoe crabs staging in the shallow waters east of the channel spawned exclusively along the eastern （N J） shoreline, but those staging west of the channel spawned throughout the bay. Overall, several insights emerged from the use of radio telemetry, which advances our understanding of horseshoe crab ecology and will be useful in conserving the Delaware Bay horseshoe crab population and habitats展开更多
Physical testing of large-scale ship models at sea is a new experimental method.It is a cheap and reliable way to research the environment adaptability of a ship in complex and extreme wave conditions.It is necessary ...Physical testing of large-scale ship models at sea is a new experimental method.It is a cheap and reliable way to research the environment adaptability of a ship in complex and extreme wave conditions.It is necessary to have a stable experimental system for the test.Since the experimental area is large, a remote control system and a telemetry system are essential, and were designed by the authors.An experiment was conducted on the Songhuajiang River to test the systems.The relationship between the model's speed and its electromotor's revolutions was also measured during the model test.The results showed that the two systems make it possible to carry out large-scale model tests at sea.展开更多
Marine risers play a key role in the deep and ultra-deep water oil and gas production. The vortex-induced vibration （VIV） of marine risers constitutes an important problem in deep water oil exploration and productio...Marine risers play a key role in the deep and ultra-deep water oil and gas production. The vortex-induced vibration （VIV） of marine risers constitutes an important problem in deep water oil exploration and production. VIV will result in high rates of structural failure of marine riser due to fatigue damage accumulation and diminishes the riser fatigue life. In-service monitoring or full scale testing is essential to improve our understanding of V1V response and enhance our ability to predict fatigue damage. One ma- rine riser fatigue acoustic telemetry scheme is proposed and an engineering prototype machine has been developed to monitor deep and ultra-deep water risers＇ fatigue and failure that can diminish the riser fatigue life and lead to economic losses and eco-catastrophe. Many breakthroughs and innovation have been achieved in the process of developing an engineering prototype machine. Sea trials were done on the 6th generation deep-water drilling platform HYSY-981 in the South China Sea. The inclination monitoring results show that the marine riser fatigue acoustic telemetry scheme is feasible and reliable and the engineering prototype machine meets the design criterion and can match the requirements of deep and ultra-deep water riser fatigue monitoring. The rich experience and field data gained in the sea trial which provide much technical support for optimization in the engineering prototype machine in the future.展开更多
The paper addresses a literature review of the technologies used in the transmission of measuring and logging data during well drilling. It presents a discussion about efficiency in data density transmission and relia...The paper addresses a literature review of the technologies used in the transmission of measuring and logging data during well drilling. It presents a discussion about efficiency in data density transmission and reliability, especially when it comes to software and automated tools. Initially, this paper analyzes the principle of the telemetry systems, considering the mud pulse telemetry, acoustic telemetry, electromagnetic telemetry and wired drill pipe telemetry. They were detailed highlighting information about functionality, data transmission and its linkage to supporting software. Focus is also given to details of the main advantages and disadvantages of each technology considering the influences of lithology, drilling fluid and formation fluids in the reliability and capacity of data transmission.展开更多
PCM/PPK telemetry system is a multi-nary pulse modulation system.It is commonly used to transmit high-accuracy time information and some express signals.To the issue of security that telemetry data is transmitted in t...PCM/PPK telemetry system is a multi-nary pulse modulation system.It is commonly used to transmit high-accuracy time information and some express signals.To the issue of security that telemetry data is transmitted in the open space,a data encryption scheme in the PCM/PPK telemetry system is proposed.In this scheme,the PCM data of signal source are encrypted by stream cipher in which key streams are generated with clock control LSFR.The scheme can save system resource in the dual-modulation compound telemetry system.A backward key synchronization scheme is also proposed,which has the property of strong real-time and easy to implement.A simplified simulation model of PCM/PPK remote system is established based on the actual framework of telemetry system,and the model is simple and easy to simulate.The error performance of the system is analyzed in theory and tested by computer simulation.Also the security of the system is analyzed.The simulation and analysis results show that the encryption scheme can ensure the security of the telemetry data and does not cause error-diffusion.展开更多
In order to grasp the downhole situation immediately, logging while drilling(LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is cr...In order to grasp the downhole situation immediately, logging while drilling(LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is critical for acoustic telemetry technology that the signal is successfully transmitted to the ground. In this paper, binary phase shift keying(BPSK) is used to modulate carrier waves for the transmission and a new BPSK demodulation scheme based on Duffing chaos is investigated. Firstly, a high-order system is given in order to enhance the signal detection capability and it is realized through building a virtual circuit using an electronic workbench(EWB). Secondly, a new BPSK demodulation scheme is proposed based on the intermittent chaos phenomena of the new Duffing system. Finally, a system variable crossing zero-point equidistance method is proposed to obtain the phase difference between the system and the BPSK signal. Then it is determined that the digital signal transmitted from the bottom of the well is ‘0’ or ‘1’. The simulation results show that the demodulation method is feasible.展开更多
Hydrocarbon exploration has evolved over the years from shallow subsurface to deep subsurface prospecting in both onshore and marine environment.In accordance,technical development has encouraged exploration of unconv...Hydrocarbon exploration has evolved over the years from shallow subsurface to deep subsurface prospecting in both onshore and marine environment.In accordance,technical development has encouraged exploration of unconventional reservoirs and development of deeply buried ones.The deeply buried carbonate reservoir in the Tarim Basin have attracted considerable attention(Lee,1985;Neil,1997;Jin et al.,2009,2015).Such deeply buried reservoirs requires careful and accurate well landing and borehole navigation through multiple regions of HC accumulation and precise well closing process involving accurate selection of positions for screens and so on.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12174421 and 11734017)the Scientific Instrument Developing Project of the Chinese Academy of Sciences,China(Grant Nos.YJKYYQ20200072 and GJJSTD20210008).
文摘Downhole acoustic telemetry(DAT),using a long drill string with periodical structures as the channel,is a prospective technology for improving the transmission rate of logging while drilling(LWD)data.Previous studies only focused on the acoustic property of a free drill string and neglected the coupling between pipes and fluid-filled boreholes.In addition to the drill-string waves,a series of fluid waves are recorded in the DAT channel,which has not been investigated yet.Unpredictable channel characteristics result in lower transmission rates and stability than expected.Therefore,a more realistic channel model is needed considering the fluid-filled borehole.In this paper,we propose a hybrid modeling method to investigate the response characteristics of the DAT channel.By combining the axial wavenumbers and excitation functions of mode waves in radially layered LWD structures,the channel model is approximated to the 1-D propagation,which considers transmission,reflection,and interconversion of the drillstring and fluid waves.The proposed 1-D approximation has been well validated by comparing the 2-D finite-difference modeling.It is revealed that the transmitted and converted fluid waves interfere with the drill-string wave,which characterizes the DAT channel as a particular coherent multi-path channel.When a fluid-filled borehole surrounds the drill string,the channel responses exhibit considerable delay as well as strong frequency selectivity in amplitude and phase.These new findings suggest that the complexity of the channel response has been underestimated in the past,and therefore channel measurements on the ground are unreliable.To address these channel characteristics,we apply a noncoherent demodulation strategy.The transmission rate for synthetic data reaches 15 bps in a 94.5 m long channel,indicating that the acoustic telemetry is promising to break the low-speed limitation of mud-pulse telemetry.
基金the National Natural Science Foundation of China(Grant Nos.11734017 and 12174421)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant Nos.YJKYYQ20200072 and GJJSTD20210008).
文摘Modeling of a drill-string acoustic channel has been an important topic in downhole telemetry for a long time.The propagation of drill-string guided waves in the borehole contains excitation,attenuation,and mode conversion issues that have not been considered by existing modeling methods.In this article,we formulate a hybrid modeling method to investigate the response characteristics of a fundamental-mode drill-string wave in various borehole environments.This hybrid method provides channel functions,including transmitting and receiving deployments,periodicity of the structure,and formation property changes.The essential physics of the drill-string wave propagation is captured with a one-dimensional model.The analytical solutions of the wavefield in multilayered cylindrical structures are introduced into a propagation matrix to express drill-string-wave interactions with the borehole environments.The effectiveness of the proposed method is confirmed through comparison with the finite-difference method.In addition,by designing numerical models,we investigate the conversion effect of the drill-string wave at the tool joint.We demonstrate that the conversion intensity of the drill-string wave is positively correlated not only with the cross-sectional area of the tool joint but also with the wave impedance of the outer formation.Hard formation outside the borehole reduces the energy leakage while intensifying the conversion of drill-string waves to Stoneley waves,and the opposite is true for the drill string in an infinite fluid.The converted Stoneley waves interfere with the drill-string waves,resulting in variations of bandgap distribution,which challenges the reliability of the data transmission.
基金supported by the National Natural Science Foundation of China (No.62102046,62072249,62072056)JinWang,YongjunRen,and Jinbin Hu receive the grant,and the URLs to the sponsors’websites are https://www.nsfc.gov.cn/.This work is also funded by the National Science Foundation of Hunan Province (No.2022JJ30618,2020JJ2029).
文摘In the Ethernet lossless Data Center Networks (DCNs) deployedwith Priority-based Flow Control (PFC), the head-of-line blocking problemis still difficult to prevent due to PFC triggering under burst trafficscenarios even with the existing congestion control solutions. To addressthe head-of-line blocking problem of PFC, we propose a new congestioncontrol mechanism. The key point of Congestion Control Using In-NetworkTelemetry for Lossless Datacenters (ICC) is to use In-Network Telemetry(INT) technology to obtain comprehensive congestion information, which isthen fed back to the sender to adjust the sending rate timely and accurately.It is possible to control congestion in time, converge to the target rate quickly,and maintain a near-zero queue length at the switch when using ICC. Weconducted Network Simulator-3 (NS-3) simulation experiments to test theICC’s performance. When compared to Congestion Control for Large-ScaleRDMA Deployments (DCQCN), TIMELY: RTT-based Congestion Controlfor the Datacenter (TIMELY), and Re-architecting Congestion Managementin Lossless Ethernet (PCN), ICC effectively reduces PFC pause messages andFlow Completion Time (FCT) by 47%, 56%, 34%, and 15.3×, 14.8×, and11.2×, respectively.
文摘BACKGROUND Inpatient telemetry heart rhythm monitoring overuse has been linked to higher healthcare costs.AIM To evaluate if CHA2DS2-VASc score could be used to indicate if a patient admitted with possible cerebrovascular accident(CVA)or transient ischemic attack(TIA)requires inpatient telemetry monitoring.METHODS A total of 257 patients presenting with CVA or TIA and placed on telemetry monitoring were analyzed retrospectively.We investigated the utility of telemetry monitoring to diagnose atrial fibrillation/flutter and the CHA2DS2-VASc scoring tool to stratify the risk of having CVA/TIA in these patients.RESULTS In our study population,63(24.5%)of the patients with CVA/TIA and telemetry monitoring were determined to have no ischemic neurologic event.Of the 194(75.5)patients that had a confirmed CVA/TIA,only 6(2.3%)had an arrhythmia detected during their inpatient telemetry monitoring period.Individuals with a confirmed CVA/TIA had a statistically significant higher CHA2DS2-VASc score compared to individuals without an ischemic event(3.59 vs 2.61,P<0.001).CONCLUSION Given the low percentage of inpatient arrhythmias identified,further research should focus on discretionary use of inpatient telemetry on higher risk patients to diagnose the arrhythmias commonly leading to CVA/TIA.A prospective study assessing event rate of CVA/TIA in patients with higher CHA2DS2-VASc score should be performed to validate the CHA2DS2-VASc score as a possible risk stratifying tool for patients at risk for CVA/TIA.
文摘随着5G技术和物联网的发展,越来越多的终端设备被黑客利用发起分布式拒绝服务(distributed denial of service,DDoS)攻击。为了解决传统DDoS攻击检测技术检测时效性慢、检出率低、需要手动配置和人工干预的问题,对telemetry技术和深度学习技术进行研究,提出基于telemetry技术的智能化DDoS检测方法,以期为相关人员或工程提供参考。
文摘A high precision, high antijamming multipoint infrared telemetry system was developed to measure the piston temperature in internal combustion engine. The temperature at the measuring point is converted into corresponding voltage signal by the thermo-couple first. Then after the V/F stage, the voltage signal is converted into the frequency signal to drive the infrared light-emitting diode to transmit infrared pulses. At the receiver end, a photosensitive audion receives the infrared pulses. After conversion, the voltage recorded by the receiver stands for the magnitude of temperature at the measuring point. Test results of the system indicate that the system is practical and the system can perform multipoint looping temperature measurements for the piston.
基金supported by NSF IOB 0517229 and NSF IOS 0920342 grants to WHW Ⅲ and CCC
文摘While several studies have documented the large-scale, seasonal movements of horseshoe crabs, little is known about their fine-scale, daily movement patterns. In this study we used a fixed array ultrasonic telemetry system to track the movements of 12 male and 16 female horseshoe crabs in the Great Bay estuary, New Hampshire. Data were obtained during the mating season, as well as during the remainder of the summer and fall, in the years 2005-2008. During the mating season animals were often, but not always, active during the high tides when they were approaching and leaving the spawning beaches. On average, both males and females approached mating beaches during 33% of the high tides they experienced and they most often made the tran- sition from being inactive to active during the last two hours of an incoming tide. From April-October horseshoe crabs were significantly more active during high tide periods vs low tide periods, with no clear preference for diurnal vs nocturnal activity. After the mating season ended horseshoe crabs continued to move into shallower water at high tide and then return to deeper water at low tide. Observations by SCUBA divers suggest that during these excursions into the mudflats horseshoe crabs were digging pits in the sediment while foraging for food. Thus, the tidal rhythm of activity that has been so well documented during the mating season probably persists into the fall, and primarily involves foraging activities
基金supported by the National Park Service under Cooperative Agreement Number CA452099007 with the University of Rhode Island
文摘American horseshoe crabs Limulus polyphemus were tracked using acoustic telemetry and traditional tagging in a semi-enclosed bay on Cape Cod （Pleasant Bay）, Massachusetts, USA, to determine seasonal movement patterns. Fifty-five actively spawning females were fitted with transmitters in 2008 and 2009 and were tracked using acoustic telemetry from May 2008 through July 2010. Fil^een crabs with transmitters also had archive depth-temperature tags attached. In addition, over 2000 spawning crabs （males and females） were tagged with US Fish and Wildlife CIdSFWS） button tags over the same period. Ninety-one percent of the crabs with transmitters were detected during this study. In the spring, crabs were primarily located in the northern section of the bay near spawning beaches, whereas in the fall crabs moved towards the deeper portions of the bay, and some may have overwIntered in the bay. There was evidence that a majority （58%-71%） of the females with transmitters spawned in two sequential seasons. One archive tag was recovered resulting in a year-long continuous record of depth and tem- perature data that, when integrated with telemetry data, indicated that the crab overwintered in the bay. The live recapture rate of crabs with USFWS button tags was 11%, with all re-sighted crabs except one observed inside Pleasant Bay. Eighty-three percent of recaptures were found within 2.5kin of the tagging location, and 51% were observed at the same beach where they were tagged. This study provides further evidence that horseshoe crabs in Pleasant Bay may be philopatric to this embayment
文摘AIM:To determine if there were any interactions between cardiac devices and small bowel capsules secondary to electromagnetic interference (EMI) in patients who have undergone small bowel capsule endoscopy (SBCE).METHODS:Authors conducted a chart review of 20 patients with a cardiac pacemaker (CP) or implantable cardioverter defibrillator (ICD) who underwent continuous electrocardiographic monitoring during their SBCE from 2003-2008.authors searched for unexplained electrocardiogram (ECG) findings,changes in CP andICD set parameters,any abnormality in transmitted capsule data,and adverse clinical events.RESULTS:There were no adverse events or hemodynamically significant arrhythmias reported.CP and ICD set parameters were preserved.The majority of ECG abnormalities were also found in pre-or post-SBCE ECG tracings and the CP behavior during arrhythmias appeared appropriate.Two patients seemed to have episodes of undersensing by the CP.However,similar findings were documented in ECGs taken outside the time frame of the SBCE.One patient was observed to have a low signal encountered from the capsule resulting in lack of localization,but no images were lost.CONCLUSION:Capsule-induced EMI remains a possibility but is unlikely to be clinically important.CPinduced interference of SBCE is also possible,but is infrequent and does not result in loss of images transmitted by the capsule.
基金Support Program, New Jersey Fish Game & Wildlife, and Delaware Department of Natural Resources and Environmental Control
文摘To study horseshoe crab Limulus polyphemus spawning behavior and migration over a large-spatial extent （〉100 km）, we arrayed fixed station radio receivers throughout Delaware Bay and deployed radio transmitters and archival tags on adult horseshoe crabs prior to their spawning season. We tagged and released 160 females and 60 males in 2004 and 217 females in 2005. The array covered approximately 140 km of shoreline. Recapture rates were 〉70% with multi-year recaptures. We categorized adult age by carapace wear. Older females tended to spawn earlier in the season and more frequently than young females, but those tendencies were more apparent in 2004 when spawning overall occurred earlier than in 2005 when spawning was delayed possibly due to decreased water temperatures. Timing of initial spawning within a year was correlated with water temperature. After adjusting for day of first spring tide, the day of In＇st spawning was 4 days earlier for every 1 degree （℃） rise in mean daily water temperature in May. Seventy nine % of spawning occurred during nighttime high tides. Fifty five % of spawning occurred within 3 d of a spring tide, which was slightly higher than the 47% expected if spawning was uniformly distributed regardless of tidal cycle. Within the same spawning season, males and females were observed spawning or intertidally resting at more than one beach separated by 〉5 kin. Between years, most （77%） did not return to spawn at the same beach. Probability of stranding was strongly age dependent for males and females with older adults experiencing higher stranding rates. Horseshoe crabs staging in the shallow waters east of the channel spawned exclusively along the eastern （N J） shoreline, but those staging west of the channel spawned throughout the bay. Overall, several insights emerged from the use of radio telemetry, which advances our understanding of horseshoe crab ecology and will be useful in conserving the Delaware Bay horseshoe crab population and habitats
基金Supported by the National Defense Foundation under Grant No.51414030204CB0109
文摘Physical testing of large-scale ship models at sea is a new experimental method.It is a cheap and reliable way to research the environment adaptability of a ship in complex and extreme wave conditions.It is necessary to have a stable experimental system for the test.Since the experimental area is large, a remote control system and a telemetry system are essential, and were designed by the authors.An experiment was conducted on the Songhuajiang River to test the systems.The relationship between the model's speed and its electromotor's revolutions was also measured during the model test.The results showed that the two systems make it possible to carry out large-scale model tests at sea.
基金supported in part by the National Science and Technology Major Project of China (2011ZX 05026-001-06)the National Natural Science Foundation of China (51249005 60972153)
文摘Marine risers play a key role in the deep and ultra-deep water oil and gas production. The vortex-induced vibration （VIV） of marine risers constitutes an important problem in deep water oil exploration and production. VIV will result in high rates of structural failure of marine riser due to fatigue damage accumulation and diminishes the riser fatigue life. In-service monitoring or full scale testing is essential to improve our understanding of V1V response and enhance our ability to predict fatigue damage. One ma- rine riser fatigue acoustic telemetry scheme is proposed and an engineering prototype machine has been developed to monitor deep and ultra-deep water risers＇ fatigue and failure that can diminish the riser fatigue life and lead to economic losses and eco-catastrophe. Many breakthroughs and innovation have been achieved in the process of developing an engineering prototype machine. Sea trials were done on the 6th generation deep-water drilling platform HYSY-981 in the South China Sea. The inclination monitoring results show that the marine riser fatigue acoustic telemetry scheme is feasible and reliable and the engineering prototype machine meets the design criterion and can match the requirements of deep and ultra-deep water riser fatigue monitoring. The rich experience and field data gained in the sea trial which provide much technical support for optimization in the engineering prototype machine in the future.
文摘The paper addresses a literature review of the technologies used in the transmission of measuring and logging data during well drilling. It presents a discussion about efficiency in data density transmission and reliability, especially when it comes to software and automated tools. Initially, this paper analyzes the principle of the telemetry systems, considering the mud pulse telemetry, acoustic telemetry, electromagnetic telemetry and wired drill pipe telemetry. They were detailed highlighting information about functionality, data transmission and its linkage to supporting software. Focus is also given to details of the main advantages and disadvantages of each technology considering the influences of lithology, drilling fluid and formation fluids in the reliability and capacity of data transmission.
文摘PCM/PPK telemetry system is a multi-nary pulse modulation system.It is commonly used to transmit high-accuracy time information and some express signals.To the issue of security that telemetry data is transmitted in the open space,a data encryption scheme in the PCM/PPK telemetry system is proposed.In this scheme,the PCM data of signal source are encrypted by stream cipher in which key streams are generated with clock control LSFR.The scheme can save system resource in the dual-modulation compound telemetry system.A backward key synchronization scheme is also proposed,which has the property of strong real-time and easy to implement.A simplified simulation model of PCM/PPK remote system is established based on the actual framework of telemetry system,and the model is simple and easy to simulate.The error performance of the system is analyzed in theory and tested by computer simulation.Also the security of the system is analyzed.The simulation and analysis results show that the encryption scheme can ensure the security of the telemetry data and does not cause error-diffusion.
基金supported by the National Natural Science Foundation of China(Grant No.51177117)the National Key Science&Technology Special Projects,China(Grant No.2011ZX05021-005)
文摘In order to grasp the downhole situation immediately, logging while drilling(LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is critical for acoustic telemetry technology that the signal is successfully transmitted to the ground. In this paper, binary phase shift keying(BPSK) is used to modulate carrier waves for the transmission and a new BPSK demodulation scheme based on Duffing chaos is investigated. Firstly, a high-order system is given in order to enhance the signal detection capability and it is realized through building a virtual circuit using an electronic workbench(EWB). Secondly, a new BPSK demodulation scheme is proposed based on the intermittent chaos phenomena of the new Duffing system. Finally, a system variable crossing zero-point equidistance method is proposed to obtain the phase difference between the system and the BPSK signal. Then it is determined that the digital signal transmitted from the bottom of the well is ‘0’ or ‘1’. The simulation results show that the demodulation method is feasible.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(NO.XDA140500001)
文摘Hydrocarbon exploration has evolved over the years from shallow subsurface to deep subsurface prospecting in both onshore and marine environment.In accordance,technical development has encouraged exploration of unconventional reservoirs and development of deeply buried ones.The deeply buried carbonate reservoir in the Tarim Basin have attracted considerable attention(Lee,1985;Neil,1997;Jin et al.,2009,2015).Such deeply buried reservoirs requires careful and accurate well landing and borehole navigation through multiple regions of HC accumulation and precise well closing process involving accurate selection of positions for screens and so on.
