To enhance the coherence and reliability of the double-ended tuning fork (DETF) resonator, a measurement system of resonator vibration is presented to check its dynamic characteristics. Laser Doppler techniques are ...To enhance the coherence and reliability of the double-ended tuning fork (DETF) resonator, a measurement system of resonator vibration is presented to check its dynamic characteristics. Laser Doppler techniques are utilized and the relation between DETF vibration velocity and output current of photodetector is obtained. Resonator vibration equation is also analyzed and its driving power only depends on the direct current bias voltage and the amplitude of alternative voltage. Furthermore, a special resonator driving control circuit based on measurement is designed. The amplitude and frequency of circuit is controlled by a computer so that highly stable and strong driving signal can be output. Experiments on driving and measuring double-ended tuning fork have been done, The frequency of driving signal is 8 kHz and the peak-to-peak value of driving voltage is 140 V. Experimental results indicate resonator can be drived stably by driving control circuit and dynamic characteristics of DETF may be measured in real time.展开更多
Three wheelers(3 Ws)are widely used in low and middle-income countries,particularly in Asia Pacific region as a comparatively cheap method to passenger transportation and goods delivery.The frequent use of 3 Ws in day...Three wheelers(3 Ws)are widely used in low and middle-income countries,particularly in Asia Pacific region as a comparatively cheap method to passenger transportation and goods delivery.The frequent use of 3 Ws in day-to-day activities have caused a large number of accidents causing injuries to their passengers.Less research has been carried out to identify the reasons behind 3 W accidents.The survey carried out prior to this research has identified that the stability control and speed control are the two key factors which the 3 W accidents attributed to.3 W fork is the main mechanical element that controls the balance and the stability of the vehicle.A damaged 3 W fork(a physical damage or a slight deformation)unbalances the 3 W and had been identified as one of the reasons for large number of accidents.Therefore,correctly reforming the damaged fork is of paramount importance,when concerning the safety of the 3 Ws.Traditionally,both heat-treating and cold-working techniques are used in the mending processes.Not only this manual-labor repairing process weakens the strength of the fork,but also the profile produced is inaccurate.This paper discusses a hydraulic operated fork mending machine with an image processing technique to reform the damaged forks in 3 Ws.An image comparator-based imaging technique is used for this machine vision-based visually guided fork repairing process.Three cameras have been used to capture the images from three perpendicular directions.A contour sketch of the original fork(before the deformation occurs)has been compared against the faulty fork,to assist the worker to carry out the repairing process.The preliminary experimentations have shown that the proposed technique can improve the repositioning of the camber angle by repairing the damaged fork.展开更多
This study was performed to evaluate pore systems of reservoir lithofacies within the Devonian Three Forks Formation in the Williston Basin through micro-scale pore characterization.These lithofacies are from the Uppe...This study was performed to evaluate pore systems of reservoir lithofacies within the Devonian Three Forks Formation in the Williston Basin through micro-scale pore characterization.These lithofacies are from the Upper Three Forks section,which is a prominent drilling target within the BakkenThree Forks Petroleum System.Samples from the Formation were examined by(1)physical core description,(2)petrographic thin section microscopy,(3)x-ray diffractometry(XRD)minerals analysis,(4)scanning electron microscopy(SEM),and(5)porosity measurements from helium porosimetry,nuclear magnetic resonance(NMR),gas adsorption and mercury intrusion porosimetry(MIP).These were done to provide better understanding of the local variations in pore structures and how such structures impact reservoir quality within the Three Forks Formation.Seven reservoir lithofacies were identified and described,including laminated lithofacies,massive dolostone,mottled dolostone,massive mudstone,mottled mudstone,mudstone conglomerates,and brecciated mudstone.Samples show a diverse variation in mineralogical composition,pore types,porosity,and pore-size distribution.Six types of pores were identified:interparticle,intercrystalline,intracrystalline,vuggy,microfractures,and mudstone microporosity.Dolostone-rich lithofacies have abundant dolomite and less siliciclastic minerals such as quartz,feldspar,and clays.They also have relatively low porosity and generally larger pore size.A general positive trend exists between porosity with clay minerals and feldspar,in contrast to a negative trend with dolomite,and no clear relationship with quartz content.Results from the gas adsorption analysis,NMR and MIP pore-size distribution confirm an abundance of macropores(>50 nm in diameters)in dolostone dominated lithofacies while other lithofacies generally have abundant mesopores(2–50 nm).展开更多
A highly sensitive light-induced thermoelectric spectroscopy(LITES)sensor based on a multi-pass cell(MPC)with dense spot pattern and a novel quartz tuning fork(QTF)with low resonance frequency is reported in this manu...A highly sensitive light-induced thermoelectric spectroscopy(LITES)sensor based on a multi-pass cell(MPC)with dense spot pattern and a novel quartz tuning fork(QTF)with low resonance frequency is reported in this manuscript.An erbi-um-doped fiber amplifier(EDFA)was employed to amplify the output optical power so that the signal level was further enhanced.The optical path length(OPL)and the ratio of optical path length to volume(RLV)of the MPC is 37.7 m and 13.8 cm^(-2),respectively.A commercial QTF and a self-designed trapezoidal-tip QTF with low frequency of 9461.83 Hz were used as the detectors of the sensor,respectively.The target gas selected to test the performance of the system was acetylene(C2H2).When the optical power was constant at 1000 mW,the minimum detection limit(MDL)of the C2H2-LITES sensor can be achieved 48.3 ppb when using the commercial QTF and 24.6 ppb when using the trapezoid-al-tip QTF.An improvement of the detection performance by a factor of 1.96 was achieved after replacing the commer-cial QTF with the trapezoidal-tip QTF.展开更多
This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in t...This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.展开更多
A new and fundamentally different geology and glacial history paradigm (new paradigm) is used to interpret previously ignored and unexplained drainage system and erosional landform evidence shown on the 1893 United St...A new and fundamentally different geology and glacial history paradigm (new paradigm) is used to interpret previously ignored and unexplained drainage system and erosional landform evidence shown on the 1893 United States Geological Survey Cranberry, North Carolina 1:125,000 scale topographic map (which has a 100-foot or about a 30-meter contour interval). In most regions including the Cranberry map area, geomorphologists have never been able to use the accepted geology and glacial history paradigm (accepted paradigm) to explain most of the topographic map drainage system and erosional landform evidence. Probably for that reason, drainage system and erosional landform evidence shown on the 1893 Cranberry topographic map and its adjacent topographic maps has been ignored for 130 years. This study demonstrates how a new geology and glacial history paradigm (new paradigm) which was developed by using Great Plains and Rocky Mountain topographic map evidence explains the 1893 Cranberry map drainage system and erosional landform evidence (and similar evidence from a small area on the adjacent 1905 Morgantown map). The new paradigm sees the Cranberry map area as being located along the southeastern rim of a continental ice sheet created and occupied deep “hole” with regional erosion occurring and present-day drainage systems developing when the headward erosion of southeast-oriented valleys from the Atlantic Ocean and of northwest-oriented valleys from the developing deep “hole” into the gradually rising deep “hole” rim captured massive and prolonged south- and southwest-oriented meltwater floods. The new paradigm permits explanations for most drainage divides, named and unnamed gaps, barbed tributaries, through valleys extending across drainage divides, isolated erosional remnants, diverging and converging valleys, and unusual river and stream direction changes which the 1893 Cranberry topographic map shows.展开更多
We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this repo...We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this report, we demonstrated a simple but effective method to compensate for this parasitic capacitance by adding a compensator circuit consisting of an inverting amplifier and a capacitor. The capacitor is connected in series with the inverting amplifier and the compensator is connected in parallel with the quartz tuning fork. The resonance curve of the system measured after adding the homemade compensator resembles that of a pure RLC circuit, meaning that the stray capacitance is successfully eliminated. Furthermore, we tried to use our equipment to measure PDMS sample and got clean data. This system can be further combined with confocal microscope and diamond with NV defect to build scanning NV magnetometry.展开更多
实现各类预想故障下潮流转移比快速仿真分析是电网安全稳定运行的重要保证。针对现有实际运行方式中潮流转移分析困难问题,提出大规模电力系统潮流转移比多核并行批处理方法。该方法基于广泛使用的商业大系统分析工具,在参数解析分类、...实现各类预想故障下潮流转移比快速仿真分析是电网安全稳定运行的重要保证。针对现有实际运行方式中潮流转移分析困难问题,提出大规模电力系统潮流转移比多核并行批处理方法。该方法基于广泛使用的商业大系统分析工具,在参数解析分类、故障自动设置及结果解析的基础上,引入深度优先搜索(depth first search,DFS)算法进行孤立节点和孤岛区域检测以保证网络完整性,结合潮流计算合理性的自动判别以实现潮流转移比的批处理分析;同时在多核环境下,构建基于Fork/Join的并行框架,采用"分治模式"递归分解计算任务,从而实现分析方法的多核并行。算例仿真和在云南电网的实际应用验证了所提方法的有效性和快速性。展开更多
基金This project is supported by National Natural Science Foundation of China (No.50275108).
文摘To enhance the coherence and reliability of the double-ended tuning fork (DETF) resonator, a measurement system of resonator vibration is presented to check its dynamic characteristics. Laser Doppler techniques are utilized and the relation between DETF vibration velocity and output current of photodetector is obtained. Resonator vibration equation is also analyzed and its driving power only depends on the direct current bias voltage and the amplitude of alternative voltage. Furthermore, a special resonator driving control circuit based on measurement is designed. The amplitude and frequency of circuit is controlled by a computer so that highly stable and strong driving signal can be output. Experiments on driving and measuring double-ended tuning fork have been done, The frequency of driving signal is 8 kHz and the peak-to-peak value of driving voltage is 140 V. Experimental results indicate resonator can be drived stably by driving control circuit and dynamic characteristics of DETF may be measured in real time.
文摘Three wheelers(3 Ws)are widely used in low and middle-income countries,particularly in Asia Pacific region as a comparatively cheap method to passenger transportation and goods delivery.The frequent use of 3 Ws in day-to-day activities have caused a large number of accidents causing injuries to their passengers.Less research has been carried out to identify the reasons behind 3 W accidents.The survey carried out prior to this research has identified that the stability control and speed control are the two key factors which the 3 W accidents attributed to.3 W fork is the main mechanical element that controls the balance and the stability of the vehicle.A damaged 3 W fork(a physical damage or a slight deformation)unbalances the 3 W and had been identified as one of the reasons for large number of accidents.Therefore,correctly reforming the damaged fork is of paramount importance,when concerning the safety of the 3 Ws.Traditionally,both heat-treating and cold-working techniques are used in the mending processes.Not only this manual-labor repairing process weakens the strength of the fork,but also the profile produced is inaccurate.This paper discusses a hydraulic operated fork mending machine with an image processing technique to reform the damaged forks in 3 Ws.An image comparator-based imaging technique is used for this machine vision-based visually guided fork repairing process.Three cameras have been used to capture the images from three perpendicular directions.A contour sketch of the original fork(before the deformation occurs)has been compared against the faulty fork,to assist the worker to carry out the repairing process.The preliminary experimentations have shown that the proposed technique can improve the repositioning of the camber angle by repairing the damaged fork.
文摘This study was performed to evaluate pore systems of reservoir lithofacies within the Devonian Three Forks Formation in the Williston Basin through micro-scale pore characterization.These lithofacies are from the Upper Three Forks section,which is a prominent drilling target within the BakkenThree Forks Petroleum System.Samples from the Formation were examined by(1)physical core description,(2)petrographic thin section microscopy,(3)x-ray diffractometry(XRD)minerals analysis,(4)scanning electron microscopy(SEM),and(5)porosity measurements from helium porosimetry,nuclear magnetic resonance(NMR),gas adsorption and mercury intrusion porosimetry(MIP).These were done to provide better understanding of the local variations in pore structures and how such structures impact reservoir quality within the Three Forks Formation.Seven reservoir lithofacies were identified and described,including laminated lithofacies,massive dolostone,mottled dolostone,massive mudstone,mottled mudstone,mudstone conglomerates,and brecciated mudstone.Samples show a diverse variation in mineralogical composition,pore types,porosity,and pore-size distribution.Six types of pores were identified:interparticle,intercrystalline,intracrystalline,vuggy,microfractures,and mudstone microporosity.Dolostone-rich lithofacies have abundant dolomite and less siliciclastic minerals such as quartz,feldspar,and clays.They also have relatively low porosity and generally larger pore size.A general positive trend exists between porosity with clay minerals and feldspar,in contrast to a negative trend with dolomite,and no clear relationship with quartz content.Results from the gas adsorption analysis,NMR and MIP pore-size distribution confirm an abundance of macropores(>50 nm in diameters)in dolostone dominated lithofacies while other lithofacies generally have abundant mesopores(2–50 nm).
基金National Natural Science Foundation of China(Grant Nos.62335006,62022032,62275065,and 61875047)Key Laboratory of Opto-Electronic Information Acquisition and Manipulation(Anhui University),Ministry of Education(Grant No.OEIAM202202)Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2023011).
文摘A highly sensitive light-induced thermoelectric spectroscopy(LITES)sensor based on a multi-pass cell(MPC)with dense spot pattern and a novel quartz tuning fork(QTF)with low resonance frequency is reported in this manuscript.An erbi-um-doped fiber amplifier(EDFA)was employed to amplify the output optical power so that the signal level was further enhanced.The optical path length(OPL)and the ratio of optical path length to volume(RLV)of the MPC is 37.7 m and 13.8 cm^(-2),respectively.A commercial QTF and a self-designed trapezoidal-tip QTF with low frequency of 9461.83 Hz were used as the detectors of the sensor,respectively.The target gas selected to test the performance of the system was acetylene(C2H2).When the optical power was constant at 1000 mW,the minimum detection limit(MDL)of the C2H2-LITES sensor can be achieved 48.3 ppb when using the commercial QTF and 24.6 ppb when using the trapezoid-al-tip QTF.An improvement of the detection performance by a factor of 1.96 was achieved after replacing the commer-cial QTF with the trapezoidal-tip QTF.
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFB2008800)the Nanchang Institute for Microtechnology of Tianjin University。
文摘This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.
文摘A new and fundamentally different geology and glacial history paradigm (new paradigm) is used to interpret previously ignored and unexplained drainage system and erosional landform evidence shown on the 1893 United States Geological Survey Cranberry, North Carolina 1:125,000 scale topographic map (which has a 100-foot or about a 30-meter contour interval). In most regions including the Cranberry map area, geomorphologists have never been able to use the accepted geology and glacial history paradigm (accepted paradigm) to explain most of the topographic map drainage system and erosional landform evidence. Probably for that reason, drainage system and erosional landform evidence shown on the 1893 Cranberry topographic map and its adjacent topographic maps has been ignored for 130 years. This study demonstrates how a new geology and glacial history paradigm (new paradigm) which was developed by using Great Plains and Rocky Mountain topographic map evidence explains the 1893 Cranberry map drainage system and erosional landform evidence (and similar evidence from a small area on the adjacent 1905 Morgantown map). The new paradigm sees the Cranberry map area as being located along the southeastern rim of a continental ice sheet created and occupied deep “hole” with regional erosion occurring and present-day drainage systems developing when the headward erosion of southeast-oriented valleys from the Atlantic Ocean and of northwest-oriented valleys from the developing deep “hole” into the gradually rising deep “hole” rim captured massive and prolonged south- and southwest-oriented meltwater floods. The new paradigm permits explanations for most drainage divides, named and unnamed gaps, barbed tributaries, through valleys extending across drainage divides, isolated erosional remnants, diverging and converging valleys, and unusual river and stream direction changes which the 1893 Cranberry topographic map shows.
文摘We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this report, we demonstrated a simple but effective method to compensate for this parasitic capacitance by adding a compensator circuit consisting of an inverting amplifier and a capacitor. The capacitor is connected in series with the inverting amplifier and the compensator is connected in parallel with the quartz tuning fork. The resonance curve of the system measured after adding the homemade compensator resembles that of a pure RLC circuit, meaning that the stray capacitance is successfully eliminated. Furthermore, we tried to use our equipment to measure PDMS sample and got clean data. This system can be further combined with confocal microscope and diamond with NV defect to build scanning NV magnetometry.
文摘实现各类预想故障下潮流转移比快速仿真分析是电网安全稳定运行的重要保证。针对现有实际运行方式中潮流转移分析困难问题,提出大规模电力系统潮流转移比多核并行批处理方法。该方法基于广泛使用的商业大系统分析工具,在参数解析分类、故障自动设置及结果解析的基础上,引入深度优先搜索(depth first search,DFS)算法进行孤立节点和孤岛区域检测以保证网络完整性,结合潮流计算合理性的自动判别以实现潮流转移比的批处理分析;同时在多核环境下,构建基于Fork/Join的并行框架,采用"分治模式"递归分解计算任务,从而实现分析方法的多核并行。算例仿真和在云南电网的实际应用验证了所提方法的有效性和快速性。