The heating,ventilating,and air conditioning(HVAC)system consumes nearly 50%of the building’s energy,especially in Taiwan with a hot and humid climate.Due to the challenges in obtaining energy sources and the negativ...The heating,ventilating,and air conditioning(HVAC)system consumes nearly 50%of the building’s energy,especially in Taiwan with a hot and humid climate.Due to the challenges in obtaining energy sources and the negative impacts of excessive energy use on the environment,it is essential to employ an energy-efficient HVAC system.This study conducted the machine tools building in a university.The field measurement was carried out,and the data were used to conduct energymodelling with EnergyPlus(EP)in order to discover some improvements in energy-efficient design.The validation between fieldmeasurement and energymodelling was performed,and the error rate was less than 10%.The following strategies were proposed in this study based on several energy-efficient approaches,including room temperature settings,chilled water supply temperature settings,chiller coefficient of performance(COP),shading,and building location.Energy-efficient approaches have been evaluated and could reduce energy consumption annually.The results reveal that the proposed energy-efficient approaches of room temperature settings(3.8%),chilled water supply temperature settings(2.1%),chiller COP(5.9%),using shading(9.1%),and building location(3.0%),respectively,could reduce energy consumption.The analysis discovered that using a well-performing HVAC system and building shading were effective in lowering the amount of energy used,and the energy modelling method could be an effective and satisfactory tool in determining potential energy savings.展开更多
This paper presents a study of the characteristics of a railway vibration at three key sections containing different track structures in a metro depot.The results show that the vertical and horizontal vibration accele...This paper presents a study of the characteristics of a railway vibration at three key sections containing different track structures in a metro depot.The results show that the vertical and horizontal vibration acceleration levels are proportional to train speed.The Z-weighted vertical acceleration levels obtained showed that the vibration source strengths at the ballast foot of the testing line and the throat area were very close.The vibration attenuation at the repair line was larger than that of the testing line.In the throat area,the peak frequency of vibration obtained at the ballast foot(2.5 m)could be shifted to a lower frequency band by using polyurethane sleepers instead of standard concrete sleepers.Polyurethane sleepers can help to reduce vertical vibration in a frequency band of 0-10 Hz.The vibration levels would satisfy the limits given in the ISO2631-2-2003(2013)for any location more than 5 m away from the source at the testing line and 2.5 m away from the source at the repair line and throat area.展开更多
Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the...Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the same time often introduces additional noise,causing a reduced accuracy.Here,a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa.In this protocol,dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time.The sensitivity of our system is about 3.4 nT=√Hz p and 1.3 mK=√Hz p,respectively.Our detection protocol not only enables multifunctional quantum sensing,but also extends more practical applications.展开更多
We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algori...We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algorithm(TSA)for zero-field resonance(ZFR).To satisfy the measurement of AMs,a resonance light of the ^(87)Rb D1 line with a spectral width of less than 1 MHz is converted to circular polarization by a linear polarizer and a quarter-wave plate.After the light beam has passed through the alkali metal vapor cell,the residual magnetic field can be measured by searching for triaxial ZFR optical peaks.The TSA stably reduces the measurement time to 2.41 s on average and improves the measurement accuracy,significantly outpacing existing methods.The weighted averages of all measurements with corresponding uncertainties are(–15.437±0.022)nT,(6.062±0.021)nT,and(–14.158±0.052)nT on the x-,y-,and z-axes,respectively.These improvements could facilitate more extremely weak magnetic studies in real time,such as magnetoencephalography(MEG)and magnetocardiography(MCG)measurements.展开更多
We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency(EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not ne...We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency(EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D_(3/2), under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt.Express 29 1558(2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional–integral–differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry.展开更多
Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is pollut...Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.展开更多
The similarity law of centrifuge test was developed for the seepage field and stress field of a foundation pit with confined water by analyzing control equations,and a similarity index and a similarity coefficient of ...The similarity law of centrifuge test was developed for the seepage field and stress field of a foundation pit with confined water by analyzing control equations,and a similarity index and a similarity coefficient of centrifuge test were obtained.Based on the deep foundation pit of the Huangxing Road Station of the Shanghai metro line M8,the deformation stability of the pit was tested.Finally,a comparative study was conducted on the test results of the pit deformation and the field measurement results.Comparison results show that the pit deformation regularity of the test is basically identical with that of the field measurement,and the difference in pit deformation between the test and the field measurement is within 50%.The centrifuge model test can effectively simulate the displacement response of the ground and retaining structure during dewatering and excavation for the pit with confined water,which provides a reliable basis for the design and construction of the pit with confined water.展开更多
Almost all conventional open-loop particle image velocimetry(PIV) methods employ fixed-interval-time optical imaging technology and the time-consuming cross-correlation-based PIV measurement algorithm to calculate the...Almost all conventional open-loop particle image velocimetry(PIV) methods employ fixed-interval-time optical imaging technology and the time-consuming cross-correlation-based PIV measurement algorithm to calculate the velocity field.In this study,a novel real-time adaptive particle image velocity(RTA-PIV) method is proposed to accurately measure the instantaneous velocity field of an unsteady flow field.In the proposed closed-loop RTA-PIV method,a new correlation-filter-based PIV measurement algorithm is introduced to calculate the velocity field in real time.Then,a Kalman predictor model is established to predict the velocity of the next time instant and a suitable interval time can be determined.To adaptively adjust the interval time for capturing two particle images,a new high-speed frame-straddling vision system is developed for the proposed RTA-PIV method.To fully analyze the performance of the RTA-PIV method,we conducted a series of numerical experiments on ground-truth image pairs and on real-world image sequences.展开更多
Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam ener...Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam energy of 6 GeV and an ultra-low emittance of better than 0.06 nm×rad(http://english.ihep.cas.cn/heps/index.html).Superconducting 3W1 wiggler magnet is one of the insertion devices in High Energy Photon Source Test Facility project(HEPS-TF).And it is also the key component to obtain higher brightness in high photon energy range.Purpose In the development process of superconducting wiggler,in order to ensure the magnetic field quality of each processing,it is necessary to monitor the magnetic field performance of before and after the full length bare magnet installed with cryostat.Therefore,different magnetic field measuring devices are being developed for different develop stages.Methods The magnetic field performance of the full length bare magnet should be tested in vertical at low temperature.After the magnetic structure is installed in the horizontal cryostat,the horizontal test is carried out.In view of these two processes,the vertical magnetic field measurement system and the horizontal magnetic field measurement system have been developed,respectively.Results The magnetic performances of the full length bare magnet and assembled with the horizontal cryostat were measured by the vertical and horizontal magnetic field measurement system.The first and second field integrals are corrected to better than the Physical requirements according to the magnetic field measurement results.Detailed magnetic field performances are described in this paper.Conclusion After more than a year operation of 3W1-SCW on the BII line station,the characteristic energy and photon flux of synchrotron radiation have been greatly improved,and the performance is excellent.It indicates that the measurement results of the magnetic field measurement system are reliable and credible.展开更多
Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds.Based on laser scanning,the...Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds.Based on laser scanning,the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle-track interaction to calibrate and verify a simulation model.The relation between the magnitude of the impact load and various operational parameters,such as vehicle speed,lateral position of wheel-rail contact,track stiffness and position of impact within a sleeper bay,is investigated.The calibrated model is later employed in simulations featuring other forms of tread damage;their effects on impact load and subsequent fatigue impact on bearings,wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed.The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear,and for general assessment of the severity of different types of railway wheel tread damage.展开更多
Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of the...Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution.In this work,a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified.The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner.This solution is well verified by our experiments and can offer a reference for selection of modulation frequencies.The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.展开更多
NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-ch...NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-channel diode laser based cavity ring-down spectroscopy(CRDS)instrument was developed to monitor the concentrations of NO3 and N2O5 in the atmosphere.The effective absorption length ratio and the total loss coefficient of the instrument were calibrated using laboratory standard samples.The effective absorption cross section of NO3 at 662 nm was derived.A detection sensitivity of 1.1 pptv NO3 in air was obtained at a time resolution of 1 s.N2O5 was converted to NO3 and detected online in the second CRDS channel.The instrument was used to monitor the concentrations of NO3 and N2O5 in the atmosphere of winter in Hefei in real time.By comparing the concentration changes of pollutants such as nitrogen oxides,ozone,PM2:5 in a rapid air cleaning process,the factors affecting the concentrations of NO3 and N2O5 in the atmosphere were discussed.展开更多
This paper presents a comparative analysis of ground vibration in three directions generated by a heavy-duty railway with various track sections.The vibration characteristics in the plane area were investigated by usi...This paper presents a comparative analysis of ground vibration in three directions generated by a heavy-duty railway with various track sections.The vibration characteristics in the plane area were investigated by using matrix test measurements.Acceleration peak attenuation was faster within 25 m from the embankment,and the high-frequency vibration attenuates faster with increased distance.For the cutting section with multi-stage soil slope,decay rate of acceleration was relatively larger.The acceleration level of the plane region ranged to 82.2-89.1 dB by the single C80 train.Yet the acceleration level caused by the C80 trains running parallel after meeting showed a distinct increment.The increment of the cutting section was much larger compared with the embankment section,with the increment ranging from 1.2-2.5 dB.In terms of the cutting section,Y direction acceleration was dominant closer to the track.Within 10-30 m of the track,the Y direction acceleration(perpendicular to the rail)decreased rapidly and became comparable to the X direction(parallel to the rail)and Z direction.Additionally,the cutting case generated a higher level of vibration in all three directions compared to the embankment,but as the distance from track increased,the deviation between acceleration gradually decreased.展开更多
Mobile phones and other electronic devices are emitting radiations that will provide harmful effects to the human health. In order to measure the radiation, an innovative low cost measurement system is proposed in thi...Mobile phones and other electronic devices are emitting radiations that will provide harmful effects to the human health. In order to measure the radiation, an innovative low cost measurement system is proposed in this paper. The ideology is to simplify the circuit’s value by converting a voltage detecting circuit to a field detecting circuit by finding an optimum resistance on trial and error basis. The requirement for a trial and error technique is to not allow too high or too low resistance which can be either short or open, resulting provides more damage to the circuit.展开更多
Urban parks are an important part of urban ecosystems and play an important role in biodiversity conservation.However,it is still unclear how park characteristics aff ect plant diversity which could hinder the conserv...Urban parks are an important part of urban ecosystems and play an important role in biodiversity conservation.However,it is still unclear how park characteristics aff ect plant diversity which could hinder the conservation of urban biodiversity due to the ineff ective design of urban parks.The diversity of woody plants in 33 parks of Changchun,China,was measured with plot measurements and linked with urban park characteristics(e.g.,size and age of the park)to uncover the relationship between them.The results show that urban woody plant species were abundant,with 98 species belonging to 51 genera and 26 families in the snow climate city of Changchun.The variation in woody plant diversity was largely explained by internal patch characteristics(e.g.,size,age,shape),and external factors surrounding the park(e.g.,land use type and socioeconomic level)accounted for only 16.0%in our study.For internal patch characteristics,older urban parks with larger areas demonstrated a richer level of plant diversity and increased nonlinearly with increasing park area.The threshold size signifi cantly aff ecting plant diversity variation was approximately 30 ha.Plant diversity had positive linear relationships with the ages of urban parks,supporting the legacy eff ect.In addition,woody plant diversity nonlinearly decreased with increasing park shape index,which suggested that the plant diversity could also be increased by optimizing the park shape.Regarding the external factors surrounding parks,the spatial distribution of woody plant diversity varied greatly from the urban center to the suburbs.House prices around the park had positive linear relationships with woody plant diversity in parks,supporting the luxury eff ect.However,building and road proportions,and green space proportion had no relationship with plant diversity in parks.This study can provide a robust reference for enriching plant diversity in urban parks,thus improving the development of urban sustainable cities.展开更多
Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures pre...Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.展开更多
Phase unwrapping is one of the key roles in fringe projection three-dimensional(3D)measurement technology.We propose a new method to achieve phase unwrapping in camera array light filed fringe projection 3D measuremen...Phase unwrapping is one of the key roles in fringe projection three-dimensional(3D)measurement technology.We propose a new method to achieve phase unwrapping in camera array light filed fringe projection 3D measurement based on deep learning.A multi-stream convolutional neural network(CNN)is proposed to learn the mapping relationship between camera array light filed wrapped phases and fringe orders of the expected central view,and is used to predict the fringe order to achieve the phase unwrapping.Experiments are performed on the light field fringe projection data generated by the simulated camera array fringe projection measurement system in Blender and by the experimental 3×3 camera array light field fringe projection system.The performance of the proposed network with light field wrapped phases using multiple directions as network input data is studied,and the advantages of phase unwrapping based on deep learning in light filed fringe projection are demonstrated.展开更多
This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to det...This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.展开更多
Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine ...Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine construction and installation has been largely reduced.Foundation stability is the key technology in the process of towing transportation.Field observation data can reflect the real state of the foundation.In this paper,the influence of water depth and towing speed on liquid level,the compartment pressure,and the pitch angles during towing of composite bucket foundation are studied.These data are analyzed based on the field measurements data from a 3.3 MW offshore wind power project in China.The results show that with varied water depths and towing speeds,the compartment pressure changes are small during the bucket foundation towing process.The offshore wind turbine composite bucket foundation is stable while being towed in the ocean.展开更多
基金support by the Ministry of Science and Technology under Grant No.MOST 108-2622-E-169-006-CC3.
文摘The heating,ventilating,and air conditioning(HVAC)system consumes nearly 50%of the building’s energy,especially in Taiwan with a hot and humid climate.Due to the challenges in obtaining energy sources and the negative impacts of excessive energy use on the environment,it is essential to employ an energy-efficient HVAC system.This study conducted the machine tools building in a university.The field measurement was carried out,and the data were used to conduct energymodelling with EnergyPlus(EP)in order to discover some improvements in energy-efficient design.The validation between fieldmeasurement and energymodelling was performed,and the error rate was less than 10%.The following strategies were proposed in this study based on several energy-efficient approaches,including room temperature settings,chilled water supply temperature settings,chiller coefficient of performance(COP),shading,and building location.Energy-efficient approaches have been evaluated and could reduce energy consumption annually.The results reveal that the proposed energy-efficient approaches of room temperature settings(3.8%),chilled water supply temperature settings(2.1%),chiller COP(5.9%),using shading(9.1%),and building location(3.0%),respectively,could reduce energy consumption.The analysis discovered that using a well-performing HVAC system and building shading were effective in lowering the amount of energy used,and the energy modelling method could be an effective and satisfactory tool in determining potential energy savings.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51479035)the Scientific Research Foundation of the Graduate School of Southeast University(Grant No.YBPY1883).
基金National Natural Science Foundation of China under Grant Nos.52068029,51878277 and 52178423the Major Discipline Academic and Technical Leaders Training Program of Jiangxi Province Youth under Grant No.20194BCJ22008the Key Research and Development Program of Jiangxi Province under Grant No.20192BBE50008。
文摘This paper presents a study of the characteristics of a railway vibration at three key sections containing different track structures in a metro depot.The results show that the vertical and horizontal vibration acceleration levels are proportional to train speed.The Z-weighted vertical acceleration levels obtained showed that the vibration source strengths at the ballast foot of the testing line and the throat area were very close.The vibration attenuation at the repair line was larger than that of the testing line.In the throat area,the peak frequency of vibration obtained at the ballast foot(2.5 m)could be shifted to a lower frequency band by using polyurethane sleepers instead of standard concrete sleepers.Polyurethane sleepers can help to reduce vertical vibration in a frequency band of 0-10 Hz.The vibration levels would satisfy the limits given in the ISO2631-2-2003(2013)for any location more than 5 m away from the source at the testing line and 2.5 m away from the source at the repair line and throat area.
基金supported by the National Natural Science Foundation of China(Nos.12005218 and 52130510).
文摘Nitrogen-vacancy color centers can perform highly sensitive and spatially resolved quantum measurements of physical quantities such as magnetic field,temperature,and pressure.Meanwhile,sensing so many variables at the same time often introduces additional noise,causing a reduced accuracy.Here,a dual-microwave time-division multiplexing protocol is used in conjunction with a lock-in amplifier in order to decouple temperature from the magnetic field and vice versa.In this protocol,dual-frequency driving and frequency modulation are used to measure the magnetic and temperature field simultaneously in real time.The sensitivity of our system is about 3.4 nT=√Hz p and 1.3 mK=√Hz p,respectively.Our detection protocol not only enables multifunctional quantum sensing,but also extends more practical applications.
基金This work was supported by Beijing Natural Science Foundation(Grant No.4191002)Key Research&Development Program of Zhejiang,China(Grant No.2020C01037)+1 种基金the National Key Research&Development Program of China(Grant No.2018YFB2002405)the National Natural Science Foundation of China(Grant No.62073014).
文摘We demonstrate a method for quickly and automatically detecting all three components of a remanent magnetic field around a shielded spin-exchange relaxation-free(SERF)atomic magnetometer(AM)using the trisection algorithm(TSA)for zero-field resonance(ZFR).To satisfy the measurement of AMs,a resonance light of the ^(87)Rb D1 line with a spectral width of less than 1 MHz is converted to circular polarization by a linear polarizer and a quarter-wave plate.After the light beam has passed through the alkali metal vapor cell,the residual magnetic field can be measured by searching for triaxial ZFR optical peaks.The TSA stably reduces the measurement time to 2.41 s on average and improves the measurement accuracy,significantly outpacing existing methods.The weighted averages of all measurements with corresponding uncertainties are(–15.437±0.022)nT,(6.062±0.021)nT,and(–14.158±0.052)nT on the x-,y-,and z-axes,respectively.These improvements could facilitate more extremely weak magnetic studies in real time,such as magnetoencephalography(MEG)and magnetocardiography(MCG)measurements.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12034012, 12074231, 12274272, and 61827824)Science and technology innovation plan of colleges and universities in Shanxi Province (Grant No. 2021L313)+2 种基金Science and Technology Project of State Grid (Grant No. 5700-202127198A-0-0-00)Fundamental Research Program of Shanxi Province (Grant No. 202203021222204)Taiyuan University of Science and Technology Scientific Research Initial Funding (Grant Nos. 20222008 and 20222132)。
文摘We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency(EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D_(3/2), under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt.Express 29 1558(2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional–integral–differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry.
基金This study was jointly funded by the National Key Research and Development Program of China(No.2016YFC0700500)the Opening Fund of Key Laboratory of Plateau Green Building and Ecological Community in Qinghai Province(No.KLKF-2020-005).
文摘Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.
文摘The similarity law of centrifuge test was developed for the seepage field and stress field of a foundation pit with confined water by analyzing control equations,and a similarity index and a similarity coefficient of centrifuge test were obtained.Based on the deep foundation pit of the Huangxing Road Station of the Shanghai metro line M8,the deformation stability of the pit was tested.Finally,a comparative study was conducted on the test results of the pit deformation and the field measurement results.Comparison results show that the pit deformation regularity of the test is basically identical with that of the field measurement,and the difference in pit deformation between the test and the field measurement is within 50%.The centrifuge model test can effectively simulate the displacement response of the ground and retaining structure during dewatering and excavation for the pit with confined water,which provides a reliable basis for the design and construction of the pit with confined water.
基金supported by the National Natural Science Foundation of China(Grant No.51875228)the National Key R&D Program of China(Grant No.2020YFA0405700)the National Defense Science and Technology Innovation Special Zone Project(Grant No.193-A14-202-01-23)。
文摘Almost all conventional open-loop particle image velocimetry(PIV) methods employ fixed-interval-time optical imaging technology and the time-consuming cross-correlation-based PIV measurement algorithm to calculate the velocity field.In this study,a novel real-time adaptive particle image velocity(RTA-PIV) method is proposed to accurately measure the instantaneous velocity field of an unsteady flow field.In the proposed closed-loop RTA-PIV method,a new correlation-filter-based PIV measurement algorithm is introduced to calculate the velocity field in real time.Then,a Kalman predictor model is established to predict the velocity of the next time instant and a suitable interval time can be determined.To adaptively adjust the interval time for capturing two particle images,a new high-speed frame-straddling vision system is developed for the proposed RTA-PIV method.To fully analyze the performance of the RTA-PIV method,we conducted a series of numerical experiments on ground-truth image pairs and on real-world image sequences.
文摘Background High Energy Photon Source(HEPS)is the fourth-generation synchrotron radiation source to be established in China.HEPS is a high-performance and high-energy synchrotron radiation light source with a beam energy of 6 GeV and an ultra-low emittance of better than 0.06 nm×rad(http://english.ihep.cas.cn/heps/index.html).Superconducting 3W1 wiggler magnet is one of the insertion devices in High Energy Photon Source Test Facility project(HEPS-TF).And it is also the key component to obtain higher brightness in high photon energy range.Purpose In the development process of superconducting wiggler,in order to ensure the magnetic field quality of each processing,it is necessary to monitor the magnetic field performance of before and after the full length bare magnet installed with cryostat.Therefore,different magnetic field measuring devices are being developed for different develop stages.Methods The magnetic field performance of the full length bare magnet should be tested in vertical at low temperature.After the magnetic structure is installed in the horizontal cryostat,the horizontal test is carried out.In view of these two processes,the vertical magnetic field measurement system and the horizontal magnetic field measurement system have been developed,respectively.Results The magnetic performances of the full length bare magnet and assembled with the horizontal cryostat were measured by the vertical and horizontal magnetic field measurement system.The first and second field integrals are corrected to better than the Physical requirements according to the magnetic field measurement results.Detailed magnetic field performances are described in this paper.Conclusion After more than a year operation of 3W1-SCW on the BII line station,the characteristic energy and photon flux of synchrotron radiation have been greatly improved,and the performance is excellent.It indicates that the measurement results of the magnetic field measurement system are reliable and credible.
基金funded from the European Union's Horizon 2020 research and innovation programme in the project In2Track3 under grant agreement No.101012456.
文摘Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds.Based on laser scanning,the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle-track interaction to calibrate and verify a simulation model.The relation between the magnitude of the impact load and various operational parameters,such as vehicle speed,lateral position of wheel-rail contact,track stiffness and position of impact within a sleeper bay,is investigated.The calibrated model is later employed in simulations featuring other forms of tread damage;their effects on impact load and subsequent fatigue impact on bearings,wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed.The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear,and for general assessment of the severity of different types of railway wheel tread damage.
基金Project supported by the National Natural Science Foundation of China(Grant No.42074216).
文摘Most triaxial-vectorial magnetic field measurements with spin-exchange relaxation free(SERF)atomic magnetometer(AM)are based on the quasi-steady-state solution of the Bloch equation.However,the responding speed of these methods is greatly limited because the frequency of the modulation signal should be slow enough to ensure the validity of the quasi-steady-state solution.In this work,a new model to describe the response of the three-axis sensitive SERF AM with high modulation frequency is presented and verified.The response of alkali-atomic spin to high-frequency modulation field is further investigated by solving the Bloch equation in a modulation-frequency-dependence manner.This solution is well verified by our experiments and can offer a reference for selection of modulation frequencies.The result shows a potential to achieve a SERF AM operating in a geomagnetic field without heavy aluminum shielding when the modulation frequencies are selected properly.
基金Hao Wu,Jian Chen,An-wen Liu,and Shui-ming Hu acknowledge the supports from the Ministry of Science and Technology of China(No.2013BAK12B00)the National Natural Science Foundation of China(No.21427804).
文摘NO3 and N2O5 are important participants in nocturnal atmospheric chemical processes,and their concentrations are of great significance in the study of the mechanism of nocturnal atmospheric chemical reactions.A two-channel diode laser based cavity ring-down spectroscopy(CRDS)instrument was developed to monitor the concentrations of NO3 and N2O5 in the atmosphere.The effective absorption length ratio and the total loss coefficient of the instrument were calibrated using laboratory standard samples.The effective absorption cross section of NO3 at 662 nm was derived.A detection sensitivity of 1.1 pptv NO3 in air was obtained at a time resolution of 1 s.N2O5 was converted to NO3 and detected online in the second CRDS channel.The instrument was used to monitor the concentrations of NO3 and N2O5 in the atmosphere of winter in Hefei in real time.By comparing the concentration changes of pollutants such as nitrogen oxides,ozone,PM2:5 in a rapid air cleaning process,the factors affecting the concentrations of NO3 and N2O5 in the atmosphere were discussed.
基金Natural Science Foundation of China under Grant No.51878242Hebei Natural Science Foundation of China under Grant Nos.E2017404013 and E2020404007。
文摘This paper presents a comparative analysis of ground vibration in three directions generated by a heavy-duty railway with various track sections.The vibration characteristics in the plane area were investigated by using matrix test measurements.Acceleration peak attenuation was faster within 25 m from the embankment,and the high-frequency vibration attenuates faster with increased distance.For the cutting section with multi-stage soil slope,decay rate of acceleration was relatively larger.The acceleration level of the plane region ranged to 82.2-89.1 dB by the single C80 train.Yet the acceleration level caused by the C80 trains running parallel after meeting showed a distinct increment.The increment of the cutting section was much larger compared with the embankment section,with the increment ranging from 1.2-2.5 dB.In terms of the cutting section,Y direction acceleration was dominant closer to the track.Within 10-30 m of the track,the Y direction acceleration(perpendicular to the rail)decreased rapidly and became comparable to the X direction(parallel to the rail)and Z direction.Additionally,the cutting case generated a higher level of vibration in all three directions compared to the embankment,but as the distance from track increased,the deviation between acceleration gradually decreased.
文摘Mobile phones and other electronic devices are emitting radiations that will provide harmful effects to the human health. In order to measure the radiation, an innovative low cost measurement system is proposed in this paper. The ideology is to simplify the circuit’s value by converting a voltage detecting circuit to a field detecting circuit by finding an optimum resistance on trial and error basis. The requirement for a trial and error technique is to not allow too high or too low resistance which can be either short or open, resulting provides more damage to the circuit.
基金supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2020237 and 2019234)the National Natural Science Foundation of China(Grant No.42171109 and 32130068).
文摘Urban parks are an important part of urban ecosystems and play an important role in biodiversity conservation.However,it is still unclear how park characteristics aff ect plant diversity which could hinder the conservation of urban biodiversity due to the ineff ective design of urban parks.The diversity of woody plants in 33 parks of Changchun,China,was measured with plot measurements and linked with urban park characteristics(e.g.,size and age of the park)to uncover the relationship between them.The results show that urban woody plant species were abundant,with 98 species belonging to 51 genera and 26 families in the snow climate city of Changchun.The variation in woody plant diversity was largely explained by internal patch characteristics(e.g.,size,age,shape),and external factors surrounding the park(e.g.,land use type and socioeconomic level)accounted for only 16.0%in our study.For internal patch characteristics,older urban parks with larger areas demonstrated a richer level of plant diversity and increased nonlinearly with increasing park area.The threshold size signifi cantly aff ecting plant diversity variation was approximately 30 ha.Plant diversity had positive linear relationships with the ages of urban parks,supporting the legacy eff ect.In addition,woody plant diversity nonlinearly decreased with increasing park shape index,which suggested that the plant diversity could also be increased by optimizing the park shape.Regarding the external factors surrounding parks,the spatial distribution of woody plant diversity varied greatly from the urban center to the suburbs.House prices around the park had positive linear relationships with woody plant diversity in parks,supporting the luxury eff ect.However,building and road proportions,and green space proportion had no relationship with plant diversity in parks.This study can provide a robust reference for enriching plant diversity in urban parks,thus improving the development of urban sustainable cities.
文摘Main quadrupole magnets are critical for the Circular Electron and Positron Collider(CEPC)and are specifically designed as dual aperture quadrupole(DAQ)magnets.However,the field crosstalk between the two apertures presents challenges.As the CEPC will work at four beam energies of Z,W,Higgs and ttbar mode,the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m.The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range.Accordingly,a compensation method was proposed in this work to solve the field crosstalk effect.By adjusting the gap height at the middle of the two apertures,the field harmonics and magnetic center shift are significantly reduced.After optimization,the short prototype was modified using a new scheme.The field simulations are validated from the magnetic measurement results.Further,the multipole field meets the requirements of the four beam energies.The detailed magnetic field optimization,field harmonics adjustment,and measurement results are presented herein.
基金the National Natural Science Foundation of China(No.61905178)the Science&Technology Development Fund of Tianjin Education Commission for Higher Education(No.2019KJ021)the Natural Science Foundation of Tianjin(No.18JCQNJC71100)。
文摘Phase unwrapping is one of the key roles in fringe projection three-dimensional(3D)measurement technology.We propose a new method to achieve phase unwrapping in camera array light filed fringe projection 3D measurement based on deep learning.A multi-stream convolutional neural network(CNN)is proposed to learn the mapping relationship between camera array light filed wrapped phases and fringe orders of the expected central view,and is used to predict the fringe order to achieve the phase unwrapping.Experiments are performed on the light field fringe projection data generated by the simulated camera array fringe projection measurement system in Blender and by the experimental 3×3 camera array light field fringe projection system.The performance of the proposed network with light field wrapped phases using multiple directions as network input data is studied,and the advantages of phase unwrapping based on deep learning in light filed fringe projection are demonstrated.
基金supported by E.S.E METROSALUD and Instituto Tecnologico Metropolitano—ITM.
文摘This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.
基金financially supported by the National Natural Science Foundation of China (Grant No. 52171274)
文摘Composite bucket foundation and one-step installation technology for offshore wind turbine are the integration of foundation construction,transportation and whole installation at sea.The cost of offshore wind turbine construction and installation has been largely reduced.Foundation stability is the key technology in the process of towing transportation.Field observation data can reflect the real state of the foundation.In this paper,the influence of water depth and towing speed on liquid level,the compartment pressure,and the pitch angles during towing of composite bucket foundation are studied.These data are analyzed based on the field measurements data from a 3.3 MW offshore wind power project in China.The results show that with varied water depths and towing speeds,the compartment pressure changes are small during the bucket foundation towing process.The offshore wind turbine composite bucket foundation is stable while being towed in the ocean.