This paper presents a method for measuring stress fields within the framework of coupled data models,aimed at determining stress fields in isotropic material structures exhibiting localized deterioration behavior with...This paper presents a method for measuring stress fields within the framework of coupled data models,aimed at determining stress fields in isotropic material structures exhibiting localized deterioration behavior without relying on constitutive equations in the deteriorated region.This approach contributes to advancing the field of intrinsic equation-free mechanics.The methodology combines measured strain fields with data-model coupling driven algorithms.The gradient and Canny operators are utilized to process the strain field data,enabling the determination of the deterioration region's location.Meanwhile,an adaptive model building method is proposed for constructing coupling driven models.To address the issue of unknown datasets during computation,a dataset updating strategy based on a differential evolutionary algorithm is introduced.The resulting optimal dataset is then used to generate stress field results.Validation against finite element method calculations demonstrates the accuracy of the proposed method in obtaining full-field stresses in specimens with local degradation behavior.展开更多
Field measurements on thermal comfort were carried out in a building with double-skin faade from January 14th to 16th,2009.Data are obtained by measurements of physical parameters and a questionnaire survey is conduct...Field measurements on thermal comfort were carried out in a building with double-skin faade from January 14th to 16th,2009.Data are obtained by measurements of physical parameters and a questionnaire survey is conducted at the same time in 27 offices of the building.The subjective survey involves questions on demographic information of the occupants,health status,environmental comfort conditions and acceptance.A total of 150 occupants are investigated and 131 questionnaires are completed.The statistical data presents the distributions of predicted mean vote,mean thermal sensation vote,mean thermal comfort vote,thermal acceptability,etc.The results show that low relative humidity is the main reason causing thermal discomfort.The greatest discomfort is dry mouth and eye dryness which are caused by low relative humidity.The females are verified to be more sensitive than the males.Meanwhile,a double-skin faade represents a good noise insulation effect while the glare problem is still unresolved.展开更多
The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Prov...The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand trans-port rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm), but increase at the high height layer (4-60cm). Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to ex-ponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.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
Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positio...Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positions and at different times and three steel bored stress sensors were installed in the return airway to measure rock stress at depth. On the basis of this arrange- ment, the rule of change of the distribution of the side abutment pressure with the advance of the working face and movement of overlying strata was studied. The rule of change and the stability of rock stress at depth were measured. Secondly, the affected area and stability time of the side abutment pressure were also studied. The results show that: 1) During working, the face advanced distance was from 157 m to 99 m, the process was not effected by mining induced pressure. When the distance was 82 m, the posi- tion of peak stress was 5 m away from the coal wall. When the distance was 37 m, the position of peak stress away from the coal wall was about 15 m to 20 m and finally reached a steady state; 2) the time and the range of the peak of side rock pressure obtained from stress sensors were consistent with the results from the dynamic roof monitors; 3) the position of the peak pressure was 25 m away from the coal wall.展开更多
In order to investigate the wind characteristics of coastal areas of China, a long-term field measurement of natural wind was carried out. Based on the field measurement results, this paper presents the natural wind c...In order to investigate the wind characteristics of coastal areas of China, a long-term field measurement of natural wind was carried out. Based on the field measurement results, this paper presents the natural wind characteristics of typhoons and strong monsoons at the site of Xi-hou-men Bridge, including mean wind speed, mean wind direction, mean wind elevation angle, turbulent intensity, gust factor, turbulence integral length scales, power spectrum of wind speed and spatial correlation of gusty wind, the profiles of mean wind speed and turbulent intensity, etc. The correlation among wind characteristics is analyzed in detail, and the similarities and differences of wind characteristics between typhoons and monsoons are analyzed. These results can pro- vide detailed wind characteristics of coastal areas of China.展开更多
This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the frame...This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition （JARE53）. Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase （AGB 5003） was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites： Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN （A） site, observed using an FG-5 absolute gravimeter （serial number 210; FG-5 #210）, was 982 524 322.7＋0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter （serial number 017; A-10 #017） at the newly located site AGS01 in Langhovde.展开更多
In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included...In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included settlements of the earth fill, tensile forces in the ties and earth pressures on the facing panels during the construction and at completion. Based on the measurements, the following statements can be made: (1) the tensile forces in the ties increased with the height of backfill above the tie and there is a tensile force crest in most ties; (2) at completion, the measured earth pressures along the wall face were between the values of the active earth pressures and the pressures at rest; (3) larger settlements occurred near the face of the wall where a zone of drainage sand and gravel was not compacted properly and smaller settlements occurred in the well-compacted backfill. The results of field pullout tests indicated that the magnitudes of pullout resistances as well as tensile forces induced in the ties were strongly influenced by the relative displacements between the ties and the backfill, and pullout resistances increased with the height of backfill above the ties and the length of ties.展开更多
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
The maximum entangled number state （NOON state） can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid ...The maximum entangled number state （NOON state） can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid spin NOON state is investigated. Based on the tunable effective coupling coefficient, we propose a generation scheme of the three-spin NOON state, i.e, the Creenberger-Horne-Zeilinger （CHZ） state, and discussed the mea- surement resolution reduction due to decoherence. It is unnecessary to entangle spins as many as possible when decoherence exists. In practice, defect spins in diamond and alp donors with long coherence time can be applied with current techniques in the nano-scaled high resolution magnetic measurement.展开更多
The high-level biosafety laboratory is not only the basic support for infectious disease prevention and control,but also interrelated with key areas such as environmental security and social security,which has attract...The high-level biosafety laboratory is not only the basic support for infectious disease prevention and control,but also interrelated with key areas such as environmental security and social security,which has attracted increasing attention.A good indoor environment is the premise to ensure the smooth progress of the experiment and biological risk prevention and control.In order to better understand the indoor environment of high-level biosafety laboratories,19 high-level biosafety laboratories in China(with a total of 65 main rooms)were carefully selected as the test objects from December 2020 to December 2022.According to the test methods specified in the Chinese standard GB 50346,the air change,cleanliness,static pressure difference,temperature,relative humidity,and illumination were tested and analyzed.The results showed that all the measured parameters met the requirements of the Chinese standard GB 50346,and the bio-safety performance was completely satisfactory.However,individual parameters showed some overlarge values:the proportion of main rooms with cleanliness levels of 7 and 8 exceeding 50%of the lower limit for air changes was 54.5%and 69.8%,respectively;the proportion of main rooms in BSL-3-b1 laboratories with atmospheric pressure differentials exceeding 50%of the standard lower limit was 94.7%;and the atmospheric pressure differential in the main rooms of BSL-3-b2 laboratories reached a maximum of nearly-160 Pa.On the premise of ensuring the cleanliness and pressure gradient of the main room,it may be possible to reduce the air change.This study,for the first time,reveals the environmental parameters of various types and levels of biosafety laboratories,which can provide reference for the design and operation of such facilities.展开更多
A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferro...A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferroelectric BaTiO_(3)ceramics.The values obtained are dependent on the ratio of sample thickness(S)and top contact radius(r).With increasing S/r from 0.17 to 1.96 the P-E responses become increasingly distorted and broader.Measurements show Wrec increases by a factor of~1.4 but Wloss increases by a factor of~7 with h decreasing from~29%to 8%.Finite element modelling was used to simulate the experimental set-up of the sample/electrode arrangements using the Jiles-Atherton model to replicate the ferroelectric behaviour of BaTiO_(3).These models demonstrate the experimentally applied electricfield using a simple geometric correction for sample thickness is an underestimation of the actualfield experienced by the material under the top contact at high S/r values.We stress the importance of reporting the contact sizes and thicknesses of samples when using PeE measurements to assess Wrec,W_(loss)andηin non-linear dielectric materials.This will allow a fairer comparison of performances between various types of materials being considered for high-energy-density ceramic capacitors.展开更多
The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would lik...The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would like to apologise for any inconvenience caused,and the corrected figures are pending as below.展开更多
On July 27,2022,a high-precision system for measuring the magnetic field based on a coherent population trapping magnetometer(referred to as the CPT system)was launched onboard the Space Advanced Technology demonstrat...On July 27,2022,a high-precision system for measuring the magnetic field based on a coherent population trapping magnetometer(referred to as the CPT system)was launched onboard the Space Advanced Technology demonstration satellite(SATech-01)by a ZK-1A rocket.The payload comprises a scalar coherent population trapping magnetometer(CPTM),triaxial anisotropic magnetoresistance magnetometer(AMRM),and nano star tracker mounted on a non-magnetic telescopic tubular mast.This configuration enables synchronized measurement of scalar and vector geomagnetic fields,as well as the attitude,making the payload with its compact sensors suitable for applications on miniature satellite platforms.On November 7,2022,the novel telescopic tubular mast was deployed in orbit,extending to a length of 5.28 m.The CPTM,an absolute scalar magnetometer with an omnidirectional sensor,is the first China-developed quantum/atomic magnetometer successfully operating in space.In orbit,the CPTM has sensitivity of~10 pT/Hz^(1/2) and can automatically operate under complex magnetic field variations.The difference between the scalar fields obtained using the CPTM and CHAOS model has a mean deviation of -3.73 nT and a standard deviation of 26.11 nT(1σ),without on-orbit calibration or correction.The miniaturized AMRM has a sensitivity of~0.3 nT/Hz^(1/2) and maintains stable and reliable operation in orbit.The low-power and miniaturized nano star tracker has a measurement uncertainty of 14.23″(1σ)in orbit.The mission has realized the on-orbit technical verification of the integrated and synchronized detection of the vector magnetic field and attitude and fully validated the system’s performance,automation level,and reliability.展开更多
A full-scale research study was conducted during the bored tunnelling of the Klang Valley Mass Rapid Transit-Putrajaya Line beneath an existing building structure in Kuala Lumpur,Malaysia.The primary objective was to ...A full-scale research study was conducted during the bored tunnelling of the Klang Valley Mass Rapid Transit-Putrajaya Line beneath an existing building structure in Kuala Lumpur,Malaysia.The primary objective was to investigate the tunnel-soil-pile interaction at various stages of tunnel excavation.This study combined field measurements and three-dimensional(3D)numerical analysis to understand the transient effects of TBM tunnelling on a loaded pile.An experimental pile was instrumented with vibrating wire strain gauges,an inclinometer,and distributed fibre optic sensors using Brillouin optical time domain analysis.The pile was pre-loaded and continuously monitored in real-time throughout the tunnel construction process.The 3D finite element modelling was used to simulate the pile’s transient responses based on actual tunnel boring machine(TBM)driving data.The study revealed that the zone of influence due to tunnelling effects extended from y¼2D to y¼4D,with the peak effect observed at y¼1D to 1.5D,where D represents the tunnel diameter.The analysis of axial load patterns highlighted transient responses,including tensile loads below the tunnel invert,which propagated upward and subsided due to negative skin friction.The maximum downdrag load observed reached 56%e71%of the pile’s working load.Additionally,pile movement patterns indicated outward deflections as the TBM approached and a return toward the tunnel post-passage,aligning with the predicted behaviour in a negative face loss scenario.This validated numerical framework provides a solid foundation for further parametric studies and enhances the understanding of tunnel-soil-pile interactions.展开更多
In order to provide a reliable basis for wind resistant evaluation of a long-span suspension bridge, a structural health monitoring system is installed on a bridge in the East China Sea and the simultaneous wind data ...In order to provide a reliable basis for wind resistant evaluation of a long-span suspension bridge, a structural health monitoring system is installed on a bridge in the East China Sea and the simultaneous wind data at the bridge deck and at the top of the bridge tower are recorded. The average wind speeds and directions, variations of wind speeds with height, turbulent characteristics, spatial correlation and characteristics of wind flow around the bridge deck are analyzed by using statistical methods and spectral analysis. It is found that the average wind speeds along the bridge girder are almost identical; however, the mean wind directions vary greatly at different locations. The dimensionless exponent decreases as the average wind speed increases. The measured turbulence intensities are greater than the recommended values, and the turbulence power spectrum can well fit the standard spectrum. However, the measured spectral values are considerably smaller in low frequency ranges. The mean wind speed of the wake flow decreases and the turbulence intensity increases significantly, and the spectral characteristics of the wake flow change obviously while the feature frequency of vortex shedding has not yet been observed.展开更多
As one of the important vegetation parameters, vegetation fractional coverage （VFC） is more difficult to measure accurately among a good many parameters of plant communities. The temperate typical steppe in the nort...As one of the important vegetation parameters, vegetation fractional coverage （VFC） is more difficult to measure accurately among a good many parameters of plant communities. The temperate typical steppe in the north of China was chosen for investigation in the present study and a digital camera was used to measure herb community coverage in the field, adopting methods of ocular estimation, gridding measurement, visual interpretation, supervised classification, and information extraction of color spatial transformation to calculate the VFC of images captured by the digital camera. In addition VFC calculated by various methods was analyzed and compared VFC, enabling us to propose an effective method for measuring VFC using a digital camera. The results of the present study indicate that： （i） as two common useful and effective methods of measuring VFC with a digital camera, not only does the error of estimated values of visual estimation and supervised classification vary considerably, but the degree of automatization is very low and depends, to a great extent, on the manipulator; （ii） although the method of visual interpretation may assure the precision of the calculated VFC and enable the precision of results obtained using other methods to be determined, as far as large quantities of data are concerned, this method has the disadvantages of wasting time and energy, and the applications of this method are limited; （iii） the precision and stability of VFC calculated using the grid and node method are superior to those of visual estimation and supervised classification and inferior to those of visual interpretation, but, as for visual interpretation and supervised classification, gridding measurements are difficult to apply in practice because they are not time efficient; and （iv） in terms of the precision of calculation of the VFC, an information-extracting model based on an intensity, hue, saturation （IHS） color space-multi-component series segmentation strategy is superior to methods of ocular estimation, gridding measurement, and supervised classification. In terms of practical efficiency, the information-extracting model is superior to visual interpretation, supervised classification, and gridding measurement. It has been proven that estimating the VFC of the north temperate typical steppe using this model is feasible. This is very fundamental research work in grassland ecology.展开更多
An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils...An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10-16.展开更多
The glass facade of high-rise building in coastal areas is vulnerable under typhoon.The research works in the literature on facade's wind-resistance performance,however,have some limitations to apply to this issue...The glass facade of high-rise building in coastal areas is vulnerable under typhoon.The research works in the literature on facade's wind-resistance performance,however,have some limitations to apply to this issue.During typhoon landing,the whole facade will vibrate and deform due to the change of atmosphere,temperature and impacted torrential rain,to result in a quite different strain or stress distribution in the glass facade from those in model test and wind tunnel test.In this paper,the field measurement on glass facade of a coastal high-rise building in Xiamen was performed,the wind pressure on the glass facade was measured and a large number of windinduced stress data were obtained during typhoon landing.The relationship between wind pressure and stress or strain of the glass panel was analyzed and the situation of stress distribution was summarized.展开更多
基金supported by the Fundamental Research Fund for the Central Universities(Grant No.BLX202226)。
文摘This paper presents a method for measuring stress fields within the framework of coupled data models,aimed at determining stress fields in isotropic material structures exhibiting localized deterioration behavior without relying on constitutive equations in the deteriorated region.This approach contributes to advancing the field of intrinsic equation-free mechanics.The methodology combines measured strain fields with data-model coupling driven algorithms.The gradient and Canny operators are utilized to process the strain field data,enabling the determination of the deterioration region's location.Meanwhile,an adaptive model building method is proposed for constructing coupling driven models.To address the issue of unknown datasets during computation,a dataset updating strategy based on a differential evolutionary algorithm is introduced.The resulting optimal dataset is then used to generate stress field results.Validation against finite element method calculations demonstrates the accuracy of the proposed method in obtaining full-field stresses in specimens with local degradation behavior.
基金The National Key Technology R&D Program of Chinaduring the 11th Five-Year Plan Period(No.2008BAJ12B05)
文摘Field measurements on thermal comfort were carried out in a building with double-skin faade from January 14th to 16th,2009.Data are obtained by measurements of physical parameters and a questionnaire survey is conducted at the same time in 27 offices of the building.The subjective survey involves questions on demographic information of the occupants,health status,environmental comfort conditions and acceptance.A total of 150 occupants are investigated and 131 questionnaires are completed.The statistical data presents the distributions of predicted mean vote,mean thermal sensation vote,mean thermal comfort vote,thermal acceptability,etc.The results show that low relative humidity is the main reason causing thermal discomfort.The greatest discomfort is dry mouth and eye dryness which are caused by low relative humidity.The females are verified to be more sensitive than the males.Meanwhile,a double-skin faade represents a good noise insulation effect while the glare problem is still unresolved.
基金Under the auspices of National Natural Science Foundation of China (No 40571019)
文摘The structure of wind-sand flow under different total sand transport rates was measured with field vertical anemometer and sand trap on the crest of typical coastal transverse ridge in Changli Gold Coast of Hebei Province, which is one of the most typical coastal aeolian distribution regions in China and famous for the tall and typical coastal transverse ridges. The measurement results show that, on the conditions of approximate wind velocities and same surface materials and environments, some changes happen to the structure of wind-sand flow with the increase of total sand transport rate on the crest of coastal transverse ridge. First, the sand transport rates of layers at different heights in the wind-sand flow increase, with the maximum increase at the height layer of 4-8cm. Second, the ratios of sand trans-port rates of layers at different heights to total sand transport rate decrease at the low height layer (0-4cm), but increase at the high height layer (4-60cm). Third, the distribution of the sand transport rate in the wind-sand flow can be expressed by an exponential function at the height layer of 0-40cm, but it changes from power function model to ex-ponential function model in the whole height layer (0-60cm) and changes into polynomial function model at the height layer of 40-60cm with the increase of total sand transport rate. Those changes have a close relationship with the limit of sand grain size of wind flow transporting and composition of sand grain size in the wind-sand flow.
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Projects 106084 supported by the Scientific and Technological Research of the Ministry of EducationBK2007701 by the Natural Science Foundation ofJiangsu Province 2006CB2022010 by the National Basic Research Program of China and the Qing-lan Project of Jiangsu Province
文摘Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positions and at different times and three steel bored stress sensors were installed in the return airway to measure rock stress at depth. On the basis of this arrange- ment, the rule of change of the distribution of the side abutment pressure with the advance of the working face and movement of overlying strata was studied. The rule of change and the stability of rock stress at depth were measured. Secondly, the affected area and stability time of the side abutment pressure were also studied. The results show that: 1) During working, the face advanced distance was from 157 m to 99 m, the process was not effected by mining induced pressure. When the distance was 82 m, the posi- tion of peak stress was 5 m away from the coal wall. When the distance was 37 m, the position of peak stress away from the coal wall was about 15 m to 20 m and finally reached a steady state; 2) the time and the range of the peak of side rock pressure obtained from stress sensors were consistent with the results from the dynamic roof monitors; 3) the position of the peak pressure was 25 m away from the coal wall.
基金Project supported by the National Natural Science Foundation of China (No. 50808148)the National Key Technology R&D Program (No. 2008BAG07B02), China
文摘In order to investigate the wind characteristics of coastal areas of China, a long-term field measurement of natural wind was carried out. Based on the field measurement results, this paper presents the natural wind characteristics of typhoons and strong monsoons at the site of Xi-hou-men Bridge, including mean wind speed, mean wind direction, mean wind elevation angle, turbulent intensity, gust factor, turbulence integral length scales, power spectrum of wind speed and spatial correlation of gusty wind, the profiles of mean wind speed and turbulent intensity, etc. The correlation among wind characteristics is analyzed in detail, and the similarities and differences of wind characteristics between typhoons and monsoons are analyzed. These results can pro- vide detailed wind characteristics of coastal areas of China.
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).
文摘This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition （JARE53）. Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase （AGB 5003） was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites： Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN （A） site, observed using an FG-5 absolute gravimeter （serial number 210; FG-5 #210）, was 982 524 322.7＋0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter （serial number 017; A-10 #017） at the newly located site AGS01 in Langhovde.
文摘In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included settlements of the earth fill, tensile forces in the ties and earth pressures on the facing panels during the construction and at completion. Based on the measurements, the following statements can be made: (1) the tensile forces in the ties increased with the height of backfill above the tie and there is a tensile force crest in most ties; (2) at completion, the measured earth pressures along the wall face were between the values of the active earth pressures and the pressures at rest; (3) larger settlements occurred near the face of the wall where a zone of drainage sand and gravel was not compacted properly and smaller settlements occurred in the well-compacted backfill. The results of field pullout tests indicated that the magnitudes of pullout resistances as well as tensile forces induced in the ties were strongly influenced by the relative displacements between the ties and the backfill, and pullout resistances increased with the height of backfill above the ties and the length of ties.
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Supported by the National Basic Research Program of China(No 2011CB921200)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant (No XDB01030200)+1 种基金the National Natural Science Foundation of China(No11374290)the Fundamental Research Funds for the Central Universities and the Foundation for Authors of National Excellent Doctoral Dissertation of China
文摘The maximum entangled number state （NOON state） can improve the sensitivity of physical quantity measure- ment to the Heisenberg limit 1/N. In this work, the magnetic field measurement based on the individual solid spin NOON state is investigated. Based on the tunable effective coupling coefficient, we propose a generation scheme of the three-spin NOON state, i.e, the Creenberger-Horne-Zeilinger （CHZ） state, and discussed the mea- surement resolution reduction due to decoherence. It is unnecessary to entangle spins as many as possible when decoherence exists. In practice, defect spins in diamond and alp donors with long coherence time can be applied with current techniques in the nano-scaled high resolution magnetic measurement.
基金supported by special fund of“Research and Demon-stration of Green and Low Carbon Design Methods and Key Tech-nologies for Hospitals and Biosafety Laboratories”by CABR(No.20220106330730007)supported by Youth Fund Project of“Research on Key technologies of Low carbon design in Arthropod Biosafety Laboratory”by China Academy of Building Research.
文摘The high-level biosafety laboratory is not only the basic support for infectious disease prevention and control,but also interrelated with key areas such as environmental security and social security,which has attracted increasing attention.A good indoor environment is the premise to ensure the smooth progress of the experiment and biological risk prevention and control.In order to better understand the indoor environment of high-level biosafety laboratories,19 high-level biosafety laboratories in China(with a total of 65 main rooms)were carefully selected as the test objects from December 2020 to December 2022.According to the test methods specified in the Chinese standard GB 50346,the air change,cleanliness,static pressure difference,temperature,relative humidity,and illumination were tested and analyzed.The results showed that all the measured parameters met the requirements of the Chinese standard GB 50346,and the bio-safety performance was completely satisfactory.However,individual parameters showed some overlarge values:the proportion of main rooms with cleanliness levels of 7 and 8 exceeding 50%of the lower limit for air changes was 54.5%and 69.8%,respectively;the proportion of main rooms in BSL-3-b1 laboratories with atmospheric pressure differentials exceeding 50%of the standard lower limit was 94.7%;and the atmospheric pressure differential in the main rooms of BSL-3-b2 laboratories reached a maximum of nearly-160 Pa.On the premise of ensuring the cleanliness and pressure gradient of the main room,it may be possible to reduce the air change.This study,for the first time,reveals the environmental parameters of various types and levels of biosafety laboratories,which can provide reference for the design and operation of such facilities.
基金the EPSRC funding to support this work through a CASE conversion DTP grant EP/T517835/1.
文摘A range of partial top full bottom electrodes are used to explore the use of bi-polar Polarisation-Electricfield(PeE)measurements to quantify recoverable energy(Wrec),energy loss(W_(loss))and the efficiency(h)of ferroelectric BaTiO_(3)ceramics.The values obtained are dependent on the ratio of sample thickness(S)and top contact radius(r).With increasing S/r from 0.17 to 1.96 the P-E responses become increasingly distorted and broader.Measurements show Wrec increases by a factor of~1.4 but Wloss increases by a factor of~7 with h decreasing from~29%to 8%.Finite element modelling was used to simulate the experimental set-up of the sample/electrode arrangements using the Jiles-Atherton model to replicate the ferroelectric behaviour of BaTiO_(3).These models demonstrate the experimentally applied electricfield using a simple geometric correction for sample thickness is an underestimation of the actualfield experienced by the material under the top contact at high S/r values.We stress the importance of reporting the contact sizes and thicknesses of samples when using PeE measurements to assess Wrec,W_(loss)andηin non-linear dielectric materials.This will allow a fairer comparison of performances between various types of materials being considered for high-energy-density ceramic capacitors.
文摘The editorial office regrets that mistakes occurred during the presentation of Figs.1 and 4.Specifically,a typographic error in Figs.1 and 4 was mistakenly taken from a different article.The editorial office would like to apologise for any inconvenience caused,and the corrected figures are pending as below.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Grant No. 2018181)the Specialized Research Fund for State Key Laboratories+1 种基金the National Natural Science Foundation of China (Grant No. 41404146)support for the mission from the Chinese Academy of Sciences。
文摘On July 27,2022,a high-precision system for measuring the magnetic field based on a coherent population trapping magnetometer(referred to as the CPT system)was launched onboard the Space Advanced Technology demonstration satellite(SATech-01)by a ZK-1A rocket.The payload comprises a scalar coherent population trapping magnetometer(CPTM),triaxial anisotropic magnetoresistance magnetometer(AMRM),and nano star tracker mounted on a non-magnetic telescopic tubular mast.This configuration enables synchronized measurement of scalar and vector geomagnetic fields,as well as the attitude,making the payload with its compact sensors suitable for applications on miniature satellite platforms.On November 7,2022,the novel telescopic tubular mast was deployed in orbit,extending to a length of 5.28 m.The CPTM,an absolute scalar magnetometer with an omnidirectional sensor,is the first China-developed quantum/atomic magnetometer successfully operating in space.In orbit,the CPTM has sensitivity of~10 pT/Hz^(1/2) and can automatically operate under complex magnetic field variations.The difference between the scalar fields obtained using the CPTM and CHAOS model has a mean deviation of -3.73 nT and a standard deviation of 26.11 nT(1σ),without on-orbit calibration or correction.The miniaturized AMRM has a sensitivity of~0.3 nT/Hz^(1/2) and maintains stable and reliable operation in orbit.The low-power and miniaturized nano star tracker has a measurement uncertainty of 14.23″(1σ)in orbit.The mission has realized the on-orbit technical verification of the integrated and synchronized detection of the vector magnetic field and attitude and fully validated the system’s performance,automation level,and reliability.
文摘A full-scale research study was conducted during the bored tunnelling of the Klang Valley Mass Rapid Transit-Putrajaya Line beneath an existing building structure in Kuala Lumpur,Malaysia.The primary objective was to investigate the tunnel-soil-pile interaction at various stages of tunnel excavation.This study combined field measurements and three-dimensional(3D)numerical analysis to understand the transient effects of TBM tunnelling on a loaded pile.An experimental pile was instrumented with vibrating wire strain gauges,an inclinometer,and distributed fibre optic sensors using Brillouin optical time domain analysis.The pile was pre-loaded and continuously monitored in real-time throughout the tunnel construction process.The 3D finite element modelling was used to simulate the pile’s transient responses based on actual tunnel boring machine(TBM)driving data.The study revealed that the zone of influence due to tunnelling effects extended from y¼2D to y¼4D,with the peak effect observed at y¼1D to 1.5D,where D represents the tunnel diameter.The analysis of axial load patterns highlighted transient responses,including tensile loads below the tunnel invert,which propagated upward and subsided due to negative skin friction.The maximum downdrag load observed reached 56%e71%of the pile’s working load.Additionally,pile movement patterns indicated outward deflections as the TBM approached and a return toward the tunnel post-passage,aligning with the predicted behaviour in a negative face loss scenario.This validated numerical framework provides a solid foundation for further parametric studies and enhances the understanding of tunnel-soil-pile interactions.
基金The National Natural Science Foundation of China (No.90815022, 50808160)
文摘In order to provide a reliable basis for wind resistant evaluation of a long-span suspension bridge, a structural health monitoring system is installed on a bridge in the East China Sea and the simultaneous wind data at the bridge deck and at the top of the bridge tower are recorded. The average wind speeds and directions, variations of wind speeds with height, turbulent characteristics, spatial correlation and characteristics of wind flow around the bridge deck are analyzed by using statistical methods and spectral analysis. It is found that the average wind speeds along the bridge girder are almost identical; however, the mean wind directions vary greatly at different locations. The dimensionless exponent decreases as the average wind speed increases. The measured turbulence intensities are greater than the recommended values, and the turbulence power spectrum can well fit the standard spectrum. However, the measured spectral values are considerably smaller in low frequency ranges. The mean wind speed of the wake flow decreases and the turbulence intensity increases significantly, and the spectral characteristics of the wake flow change obviously while the feature frequency of vortex shedding has not yet been observed.
文摘As one of the important vegetation parameters, vegetation fractional coverage （VFC） is more difficult to measure accurately among a good many parameters of plant communities. The temperate typical steppe in the north of China was chosen for investigation in the present study and a digital camera was used to measure herb community coverage in the field, adopting methods of ocular estimation, gridding measurement, visual interpretation, supervised classification, and information extraction of color spatial transformation to calculate the VFC of images captured by the digital camera. In addition VFC calculated by various methods was analyzed and compared VFC, enabling us to propose an effective method for measuring VFC using a digital camera. The results of the present study indicate that： （i） as two common useful and effective methods of measuring VFC with a digital camera, not only does the error of estimated values of visual estimation and supervised classification vary considerably, but the degree of automatization is very low and depends, to a great extent, on the manipulator; （ii） although the method of visual interpretation may assure the precision of the calculated VFC and enable the precision of results obtained using other methods to be determined, as far as large quantities of data are concerned, this method has the disadvantages of wasting time and energy, and the applications of this method are limited; （iii） the precision and stability of VFC calculated using the grid and node method are superior to those of visual estimation and supervised classification and inferior to those of visual interpretation, but, as for visual interpretation and supervised classification, gridding measurements are difficult to apply in practice because they are not time efficient; and （iv） in terms of the precision of calculation of the VFC, an information-extracting model based on an intensity, hue, saturation （IHS） color space-multi-component series segmentation strategy is superior to methods of ocular estimation, gridding measurement, and supervised classification. In terms of practical efficiency, the information-extracting model is superior to visual interpretation, supervised classification, and gridding measurement. It has been proven that estimating the VFC of the north temperate typical steppe using this model is feasible. This is very fundamental research work in grassland ecology.
基金supported by the National Basic Research Program of China(No.2005CB724506)the National Natural Science Foundation of China(Nos. 10604058 and 10974215)the Open Research Fund of State Key Laboratory of Precision Spectroscope.
文摘An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of 87Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10-16.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90815030,50978094,51008237)
文摘The glass facade of high-rise building in coastal areas is vulnerable under typhoon.The research works in the literature on facade's wind-resistance performance,however,have some limitations to apply to this issue.During typhoon landing,the whole facade will vibrate and deform due to the change of atmosphere,temperature and impacted torrential rain,to result in a quite different strain or stress distribution in the glass facade from those in model test and wind tunnel test.In this paper,the field measurement on glass facade of a coastal high-rise building in Xiamen was performed,the wind pressure on the glass facade was measured and a large number of windinduced stress data were obtained during typhoon landing.The relationship between wind pressure and stress or strain of the glass panel was analyzed and the situation of stress distribution was summarized.
