We present a quantitative measurement of the horizontal component of the microwave magnetic field of a coplanar waveguide using a quantum diamond probe in fiber format.The measurement results are compared in detail wi...We present a quantitative measurement of the horizontal component of the microwave magnetic field of a coplanar waveguide using a quantum diamond probe in fiber format.The measurement results are compared in detail with simulation,showing a good consistence.Further simulation shows fiber diamond probe brings negligible disturbance to the field under measurement compared to bulk diamond.This method will find important applications ranging from electromagnetic compatibility test and failure analysis of high frequency and high complexity integrated circuits.展开更多
The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(R...The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.展开更多
A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the ...A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.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
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
Let X={X(t)∈R^(d),t∈R^(N)}be a centered space-time anisotropic Gaussian field with indices H=(H_(1),…,H_(N))∈(0,1)~N,where the components X_(i)(i=1,…,d)of X are independent,and the canonical metric√(E(X_(i)(t)-X...Let X={X(t)∈R^(d),t∈R^(N)}be a centered space-time anisotropic Gaussian field with indices H=(H_(1),…,H_(N))∈(0,1)~N,where the components X_(i)(i=1,…,d)of X are independent,and the canonical metric√(E(X_(i)(t)-X_(i)(s))^(2))^(1/2)(i=1,…,d)is commensurate with■for s=(s_(1),…,s_(N)),t=(t_(1),…,t_(N))∈R~N,α_(i)∈(0,1],and with the continuous functionγ(·)satisfying certain conditions.First,the upper and lower bounds of the hitting probabilities of X can be derived from the corresponding generalized Hausdorff measure and capacity,which are based on the kernel functions depending explicitly onγ(·).Furthermore,the multiple intersections of the sample paths of two independent centered space-time anisotropic Gaussian fields with different distributions are considered.Our results extend the corresponding results for anisotropic Gaussian fields to a large class of space-time anisotropic Gaussian fields.展开更多
We performed ultrasonic measurements on a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) to explore the ground state properties derived from non-Kramers Γ_(3) doublet of Pr^(3+).PrRu_(2)In_(2)Zn_(18) is a quaternary...We performed ultrasonic measurements on a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) to explore the ground state properties derived from non-Kramers Γ_(3) doublet of Pr^(3+).PrRu_(2)In_(2)Zn_(18) is a quaternary derivative of the ternary compound PrRu_(2)Zn_(20) that exhibits a structural phase transition at T_S=138 K.In PrRu_(2)In_(2)Zn_(18),the Zn atoms at the 16c site in PrRu_(2)Zn_(20) are selectively replaced by In atoms.A monotonic increase was observed in the temperature dependence of elastic constants C_L=(C_(11)+2C_(12)+4C_(44))/3 and C_(T)=(C_(11)-C_(12)+C_(44))/3 in the temperature range around T_(S) to which an elastic softening was observed in(C_(11)-C_(12))/2 for PrRu_(2)Zn_(20).The disappearance of the softening indicates that the structural transition in PrRu_(2)Zn_(20) is suppressed by the substitution of Zn ions by In ones with a larger ionic radius.Alternatively,the C_(T) of PrRu_(2)In_(2)Zn_(18) exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ_(3) ground state.We discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu_(2)In_(2)Zn_(18) grown under different conditions.展开更多
In track and field sports,the 100-meter race is an extremely intense sport that requires effective training of athletes’core strength.From the perspective of adolescents,in order to enhance core strength,it is necess...In track and field sports,the 100-meter race is an extremely intense sport that requires effective training of athletes’core strength.From the perspective of adolescents,in order to enhance core strength,it is necessary to effectively fix the pelvic position in the process of exercise,so that the core stability,balance,and coordination of athletes can be improved.The training process of the 100-meter event is mainly an anaerobic metabolic exercise,it is necessary to ensure that athletes maintain a high level of physical readiness during the exercises and concentrate highly on their core strength,so that they can achieve excellent results.This paper analyzes the core strength training for the 100-meter event in track and field sports,discusses its importance,and puts forward specific training methods,hoping to provide guidelines for relevant researchers.展开更多
It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on A...It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on Antarctica. The calculated values are, on average, less than the experimental, especially on the propagation path between RID and Antarctica. The field strength by the experiment may be used as the basic data for the research of HF propagation over the very long distance. Because of the large deviation it seems to be necessary to study HF propagation over the very long distance in details, especially the propagation model.展开更多
We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium g...We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S(1/2)〉,an excited state |6P(3/2)〉, and Rydberg state |nD(5/2)〉. Two radio frequency(RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency(Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of k Hz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D(5/2)〉→ |69P(3/2)〉 transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D(5/2)〉→ |81P(3/2)〉 transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.展开更多
The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cel...The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cell, high-resolution spatial distribution of the microwave electric field strength is achieved for both a cubic cell and a cylinder cell. The spatial distribution of the microwave field strength in two dimensions is measured with sub-wavelength resolution. The experimental results show that the shape of a vapor cell has a significant influence on the abnormal spatial distribution because of the Fabry-P6rot effect inside a vapor cell. A theoretical simulation is obtained for different vapor cell wall thicknesses and shows that a restricted wall thickness results in a measurement fluctuation smaller than 3% at the center of the vapor cell.展开更多
Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to meas...Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.展开更多
Light field imaging technology can obtain three-dimensional(3D)information of a test surface in a single exposure.Traditional light field reconstruction algorithms not only take a long time to trace back to the origin...Light field imaging technology can obtain three-dimensional(3D)information of a test surface in a single exposure.Traditional light field reconstruction algorithms not only take a long time to trace back to the original image,but also require the exact parameters of the light field system,such as the position and posture of a microlens array(MLA),which will cause errors in the reconstructed image if these parameters cannot be precisely obtained.This paper proposes a reconstruction algorithm for light field imaging based on the point spread function(PSF),which does not require prior knowledge of the system.The accurate PSF derivation process of a light field system is presented,and modeling and simulation were conducted to obtain the relationship between the spatial distribution characteristics and the PSF of the light field system.A morphology-based method is proposed to analyze the overlapping area of the subimages of light field images to identify the accurate spatial location of the MLA used in the system,which is thereafter used to accurately refocus light field imaging.A light field system is built to verify the algorithm’s effectiveness.Experimental results show that the measurement accuracy is increased over 41.0%compared with the traditional method by measuring a step standard.The accuracy of parameters is also improved through a microstructure measurement with a peak-to-valley value of 25.4%and root mean square value of 23.5%improvement.This further validates that the algorithm can effectively improve the refocusing efficiency and the accuracy of the light field imaging results with the superiority of refocusing light field imaging without prior knowledge of the system.The proposed method provides a new solution for fast and accurate 3D measurement based on a light field.展开更多
The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,suc...The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,such as surface deformation,groundwater storage changes,and mass migration before and after earthquakes.Based on repeated terrestrial gravity measurements at 198 gravity stations in the Sichuan-Yunnan region(SYR)from 2015 to 2017,we determine a time series of degree 120 gravity fields using the localized spherical harmonic(Slepian)basis functions.Our results show that adopting the first 6 Slepian basis functions is sufficient for effective localized Slepian modeling in the SYR.The differences between two gravity campaigns at the same time of year show an obvious correlation with tectonic features.The degree 120 timevariable gravity models presented in this paper will benefit the study of the regional mass migration inside the crust of the SYR and supplement the existing geophysical models for the China Seismic Experimental Site.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
Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriche...Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.展开更多
The hot-section parts easily occur the creep-fatigued interaction under the condition of mechanicalthermal coupled load during the period of service, which may lead to the damage of the parts, and therefore, the measu...The hot-section parts easily occur the creep-fatigued interaction under the condition of mechanicalthermal coupled load during the period of service, which may lead to the damage of the parts, and therefore, the measurement and characterization of thermal-deformed fields of the parts are important to understand its damage process. Aiming at relevant demand, the bilateral telecentric-multispectral imaging system was established, the research of synchronous measurement technique of the temperature and deformation fields was developed. On the one hand, the measurement technology for surface temperature of the object was developed using the two-color images captured by the multispectral camera with bilateral telecentric lens and combined with colorimetric method. On the other hand, the 2 D-DIC measurement technique of the multispectral camera was developed by conducting digital image correlation analysis using the blue light images before and after deformation, which can measure the high temperature deformation field of the object(the blue light images were filtered by multispectral camera).Results showed that the bilateral telecentric lens is used to replace the ordinary optical lens for imaging,which can effectively eliminate the distortion of the multispectral imaging system. Since the temperature measurement process of this measurement system is little affected by the emissivity of the object, therefore, it has excellent robustness. The thermal expansion coefficients of the nickel alloys are evaluated at the temperature ranges of 700–1000℃, indicating this system can achieve the synchronous and precise measurement of the temperature and deformation fields of the object.展开更多
The entropy squeezing of a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel is investigated in detail. Our results show that when coupled to the single-mod...The entropy squeezing of a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel is investigated in detail. Our results show that when coupled to the single-mode field, the atom in appropriate initial states can not only generate obvious entropy squeezing but also keep in the optimal squeezing state,while passing through the amplitude damping channel, the atom can generate entropy squeezing under the control of the weak measurement. Besides, it is proved again that as a measurement method for atomic squeezing, the entropy squeezing is precise and effective. Therefore our work is instructive for experiments in preparing three-level system information resource with ultra-low quantum noise.展开更多
Objective To investigate effect of MR field strength on texture features of cerebral T2 fluid attenuated inversion recovery(T2-FLAIR)images.Methods We acquired cerebral 3 D T2-FLAIR images of thirty patients who were ...Objective To investigate effect of MR field strength on texture features of cerebral T2 fluid attenuated inversion recovery(T2-FLAIR)images.Methods We acquired cerebral 3 D T2-FLAIR images of thirty patients who were diagnosed with ischemic white matter lesion(WML)with MR-1.5 T and MR-3.0 T scanners.Histogram texture features which included mean signal intensity(Mean),Skewness and Kurtosis,and gray level co-occurrence matrix(GLCM)texture features which included angular second moment(ASM),Contrast,Correlation,Inverse difference moment(IDM)and Entropy,of regions of interest located in the area of WML and normal white matter(NWM)were measured by ImageJ software.The texture parameters acquired with MR-1.5 T scanning were compared with MR-3.0 T scanning.Results The Mean of both WML and NWM obtained with MR-1.5 T scanning was significantly lower than that acquired with MR-3.0 T(P<0.001),while Skewness and Kurtosis between MR-1.5 T and MR-3.0 T scanning showed no significant difference(P>0.05).ASM,Correlation and IDM of both WML and NWM acquired with MR-1.5 T revealed significantly lower values than those with MR-3.0 T(P<0.001),while Contrast and Entropy acquired with MR-1.5 T showed significantly higher values than those with MR-3.0 T(P<0.001).Conclusion MR field strength showed no significant effect on histogram textures,while had significant effect on GLCM texture features of cerebral T2-FLAIR images,which indicated that it should be cautious to explain the texture results acquired based on the different MR field strength.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant No.2021YFB2012600)。
文摘We present a quantitative measurement of the horizontal component of the microwave magnetic field of a coplanar waveguide using a quantum diamond probe in fiber format.The measurement results are compared in detail with simulation,showing a good consistence.Further simulation shows fiber diamond probe brings negligible disturbance to the field under measurement compared to bulk diamond.This method will find important applications ranging from electromagnetic compatibility test and failure analysis of high frequency and high complexity integrated circuits.
基金supported by the National Key Research and Development Program of China(No.2023YFC2907600)the National Natural Science Foundation of China(Nos.42077267,42277174 and 52074164)+2 种基金the Natural Science Foundation of Shandong Province,China(No.ZR2020JQ23)the Opening Project of State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology(No.KFJJ21-02Z)the Fundamental Research Funds for the Central Universities,China(No.2022JCCXSB03).
文摘The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.
文摘A significant number of fire-induced power disruptions are observed in several countries every year. The faults are normally phase-to-phase short circuiting or conductor-to-ground discharges at mid-span region of the high-voltage transmission system. In any case, the wildfire plumes provide a conductive path. The electrical conductivity is due to intense heat in combustion zone of the fire which creates ion and electrons from flame inherent particulates. Increase in the ion concentration increases the electrical conductivity of the fire plume. The main purpose of this study was to measure dielectric breakdown electric field for vegetation and hydrocarbon flames. The experimental data is needed for validation of simulation schemes which are necessary for evaluation of power grid systems reliability under extreme wildfire weather conditions. In this study, hydrocarbon and vegetation fuels were ignited in a cylindrically shaped steel burner which was fitted with type-K thermocouples to measure flame temperature. The fuels consisted of dried weeping wattle (Peltophorum africanum) litter, butane gas and candle wax. Two pinned copper electrodes supported by retort stands were mounted to the burner and energized to a high voltage. This generated a strong electric field sufficient to initiate dielectric breakdown in the flames. Breakdown electric field strength (Ecrit) obtained from the experiment decreased from 10.5 to 6.9 kV/cm for the flames with temperature range of 1003 to 1410 K, respectively.
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 Natural Science Foundation of China(12371150,11971432)the Natural Science Foundation of Zhejiang Province(LY21G010003)+2 种基金the Management Project of"Digital+"Discipline Construction of Zhejiang Gongshang University(SZJ2022A012,SZJ2022B017)the Characteristic&Preponderant Discipline of Key Construction Universities in Zhejiang Province(Zhejiang Gongshang University-Statistics)the Scientific Research Projects of Universities in Anhui Province(2022AH050955)。
文摘Let X={X(t)∈R^(d),t∈R^(N)}be a centered space-time anisotropic Gaussian field with indices H=(H_(1),…,H_(N))∈(0,1)~N,where the components X_(i)(i=1,…,d)of X are independent,and the canonical metric√(E(X_(i)(t)-X_(i)(s))^(2))^(1/2)(i=1,…,d)is commensurate with■for s=(s_(1),…,s_(N)),t=(t_(1),…,t_(N))∈R~N,α_(i)∈(0,1],and with the continuous functionγ(·)satisfying certain conditions.First,the upper and lower bounds of the hitting probabilities of X can be derived from the corresponding generalized Hausdorff measure and capacity,which are based on the kernel functions depending explicitly onγ(·).Furthermore,the multiple intersections of the sample paths of two independent centered space-time anisotropic Gaussian fields with different distributions are considered.Our results extend the corresponding results for anisotropic Gaussian fields to a large class of space-time anisotropic Gaussian fields.
基金Project supported by the Soft-Path Science and Engineering Research Center (SPERC),Iwate Universitythe JSPS KAKENHI (Grant Nos. JP18K03530,JP21K04622, and JP21K13869)。
文摘We performed ultrasonic measurements on a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) to explore the ground state properties derived from non-Kramers Γ_(3) doublet of Pr^(3+).PrRu_(2)In_(2)Zn_(18) is a quaternary derivative of the ternary compound PrRu_(2)Zn_(20) that exhibits a structural phase transition at T_S=138 K.In PrRu_(2)In_(2)Zn_(18),the Zn atoms at the 16c site in PrRu_(2)Zn_(20) are selectively replaced by In atoms.A monotonic increase was observed in the temperature dependence of elastic constants C_L=(C_(11)+2C_(12)+4C_(44))/3 and C_(T)=(C_(11)-C_(12)+C_(44))/3 in the temperature range around T_(S) to which an elastic softening was observed in(C_(11)-C_(12))/2 for PrRu_(2)Zn_(20).The disappearance of the softening indicates that the structural transition in PrRu_(2)Zn_(20) is suppressed by the substitution of Zn ions by In ones with a larger ionic radius.Alternatively,the C_(T) of PrRu_(2)In_(2)Zn_(18) exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ_(3) ground state.We discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu_(2)In_(2)Zn_(18) grown under different conditions.
文摘In track and field sports,the 100-meter race is an extremely intense sport that requires effective training of athletes’core strength.From the perspective of adolescents,in order to enhance core strength,it is necessary to effectively fix the pelvic position in the process of exercise,so that the core stability,balance,and coordination of athletes can be improved.The training process of the 100-meter event is mainly an anaerobic metabolic exercise,it is necessary to ensure that athletes maintain a high level of physical readiness during the exercises and concentrate highly on their core strength,so that they can achieve excellent results.This paper analyzes the core strength training for the 100-meter event in track and field sports,discusses its importance,and puts forward specific training methods,hoping to provide guidelines for relevant researchers.
基金The research is supported by the National Natural Science Foundation of China State Antarctic Committee
文摘It was ascertained that there is a great margin between the theoretical values and experimental medians of the field strength of RWM and RID signals during high solar activity period at Chinese Great Wall Station on Antarctica. The calculated values are, on average, less than the experimental, especially on the propagation path between RID and Antarctica. The field strength by the experiment may be used as the basic data for the research of HF propagation over the very long distance. Because of the large deviation it seems to be necessary to study HF propagation over the very long distance in details, especially the propagation model.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61475090,61675123,61775124,and 11804202)+1 种基金the State Key Program of National Natural Science of China(Grant Nos.11434007 and 61835007)Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT 17R70)。
文摘We present a precise measurement of a weak radio frequency electric field with a frequency of ■3 GHz employing a resonant atomic probe that is constituted with a Rydberg cascade three-level atom, including a cesium ground state |6S(1/2)〉,an excited state |6P(3/2)〉, and Rydberg state |nD(5/2)〉. Two radio frequency(RF) electric fields, noted as local and signal fields, couple the nearby Rydberg transition. The two-photon resonant Rydberg electromagnetically induced transparency(Rydberg-EIT) is employed to directly read out the weak signal field having hundreds of k Hz difference between the local and signal fields that is encoded in the resonant microwave-dressed Rydberg atoms. The minimum detectable signal fields of ESmin= 1.36 ± 0.04 mV/m for 2.18 GHz coupling |68D(5/2)〉→ |69P(3/2)〉 transition and 1.33 ± 0.02 mV/m for 1.32 GHz coupling |80D(5/2)〉→ |81P(3/2)〉 transition are obtained, respectively. The bandwidth dependence is also investigated by varying the signal field frequency and corresponding -3 dB bandwidth of 3 MHz is attained. This method can be employed to perform a rapid and precise measurement of the weak electric field, which is important for the atom-based microwave metrology.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA03044200 and 2016YFF0200104)the National Natural Science Foundation of China(Grant Nos.91536110,61505099,and 61378013)the Fund for Shanxi“331 Project”Key Subjects Construction,China
文摘The geometry effect of a vapor cell on the metrology of a microwave electric field is investigated. Based on the splitting of the electromagnetically induced transparency spectra of cesium Rydberg atoms in a vapor cell, high-resolution spatial distribution of the microwave electric field strength is achieved for both a cubic cell and a cylinder cell. The spatial distribution of the microwave field strength in two dimensions is measured with sub-wavelength resolution. The experimental results show that the shape of a vapor cell has a significant influence on the abnormal spatial distribution because of the Fabry-P6rot effect inside a vapor cell. A theoretical simulation is obtained for different vapor cell wall thicknesses and shows that a restricted wall thickness results in a measurement fluctuation smaller than 3% at the center of the vapor cell.
文摘Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.
基金This work was partially supported by the National Key R&D Program of China(No.2017YFA0701200)the National Nat-ural Science Foundation of China(Grant No.52075100)Shanghai Science and Technology Committee Innovation Grant(19ZR1404600).
文摘Light field imaging technology can obtain three-dimensional(3D)information of a test surface in a single exposure.Traditional light field reconstruction algorithms not only take a long time to trace back to the original image,but also require the exact parameters of the light field system,such as the position and posture of a microlens array(MLA),which will cause errors in the reconstructed image if these parameters cannot be precisely obtained.This paper proposes a reconstruction algorithm for light field imaging based on the point spread function(PSF),which does not require prior knowledge of the system.The accurate PSF derivation process of a light field system is presented,and modeling and simulation were conducted to obtain the relationship between the spatial distribution characteristics and the PSF of the light field system.A morphology-based method is proposed to analyze the overlapping area of the subimages of light field images to identify the accurate spatial location of the MLA used in the system,which is thereafter used to accurately refocus light field imaging.A light field system is built to verify the algorithm’s effectiveness.Experimental results show that the measurement accuracy is increased over 41.0%compared with the traditional method by measuring a step standard.The accuracy of parameters is also improved through a microstructure measurement with a peak-to-valley value of 25.4%and root mean square value of 23.5%improvement.This further validates that the algorithm can effectively improve the refocusing efficiency and the accuracy of the light field imaging results with the superiority of refocusing light field imaging without prior knowledge of the system.The proposed method provides a new solution for fast and accurate 3D measurement based on a light field.
基金the National Natural Science Foundation of China(Nos.41974095,41774090,and U1939205)the Special Fund of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB20X09,and DQJB21R30)The first author acknowledges support from the China Postdoctoral Science Foundation(No.2018M641424)。
文摘The terrestrial time-variable gravity measurements are characterized by a high signal-to-noise ratio and sensitivity to the sources of mass change in the Earth's crust.These gravity data have many applications,such as surface deformation,groundwater storage changes,and mass migration before and after earthquakes.Based on repeated terrestrial gravity measurements at 198 gravity stations in the Sichuan-Yunnan region(SYR)from 2015 to 2017,we determine a time series of degree 120 gravity fields using the localized spherical harmonic(Slepian)basis functions.Our results show that adopting the first 6 Slepian basis functions is sufficient for effective localized Slepian modeling in the SYR.The differences between two gravity campaigns at the same time of year show an obvious correlation with tectonic features.The degree 120 timevariable gravity models presented in this paper will benefit the study of the regional mass migration inside the crust of the SYR and supplement the existing geophysical models for the China Seismic Experimental Site.
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.
文摘Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.
基金the National Natural Science Foundation of China(Grant Nos.12032013 and 11972209)the National Key Research and Development Program of China(Grant No.2017YFB1103900)the National Science and Technology Major Project(Grant No.2017-VⅠ-0003-0073).
文摘The hot-section parts easily occur the creep-fatigued interaction under the condition of mechanicalthermal coupled load during the period of service, which may lead to the damage of the parts, and therefore, the measurement and characterization of thermal-deformed fields of the parts are important to understand its damage process. Aiming at relevant demand, the bilateral telecentric-multispectral imaging system was established, the research of synchronous measurement technique of the temperature and deformation fields was developed. On the one hand, the measurement technology for surface temperature of the object was developed using the two-color images captured by the multispectral camera with bilateral telecentric lens and combined with colorimetric method. On the other hand, the 2 D-DIC measurement technique of the multispectral camera was developed by conducting digital image correlation analysis using the blue light images before and after deformation, which can measure the high temperature deformation field of the object(the blue light images were filtered by multispectral camera).Results showed that the bilateral telecentric lens is used to replace the ordinary optical lens for imaging,which can effectively eliminate the distortion of the multispectral imaging system. Since the temperature measurement process of this measurement system is little affected by the emissivity of the object, therefore, it has excellent robustness. The thermal expansion coefficients of the nickel alloys are evaluated at the temperature ranges of 700–1000℃, indicating this system can achieve the synchronous and precise measurement of the temperature and deformation fields of the object.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12064012 and 11374096)。
文摘The entropy squeezing of a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel is investigated in detail. Our results show that when coupled to the single-mode field, the atom in appropriate initial states can not only generate obvious entropy squeezing but also keep in the optimal squeezing state,while passing through the amplitude damping channel, the atom can generate entropy squeezing under the control of the weak measurement. Besides, it is proved again that as a measurement method for atomic squeezing, the entropy squeezing is precise and effective. Therefore our work is instructive for experiments in preparing three-level system information resource with ultra-low quantum noise.
文摘Objective To investigate effect of MR field strength on texture features of cerebral T2 fluid attenuated inversion recovery(T2-FLAIR)images.Methods We acquired cerebral 3 D T2-FLAIR images of thirty patients who were diagnosed with ischemic white matter lesion(WML)with MR-1.5 T and MR-3.0 T scanners.Histogram texture features which included mean signal intensity(Mean),Skewness and Kurtosis,and gray level co-occurrence matrix(GLCM)texture features which included angular second moment(ASM),Contrast,Correlation,Inverse difference moment(IDM)and Entropy,of regions of interest located in the area of WML and normal white matter(NWM)were measured by ImageJ software.The texture parameters acquired with MR-1.5 T scanning were compared with MR-3.0 T scanning.Results The Mean of both WML and NWM obtained with MR-1.5 T scanning was significantly lower than that acquired with MR-3.0 T(P<0.001),while Skewness and Kurtosis between MR-1.5 T and MR-3.0 T scanning showed no significant difference(P>0.05).ASM,Correlation and IDM of both WML and NWM acquired with MR-1.5 T revealed significantly lower values than those with MR-3.0 T(P<0.001),while Contrast and Entropy acquired with MR-1.5 T showed significantly higher values than those with MR-3.0 T(P<0.001).Conclusion MR field strength showed no significant effect on histogram textures,while had significant effect on GLCM texture features of cerebral T2-FLAIR images,which indicated that it should be cautious to explain the texture results acquired based on the different MR field strength.
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).