Long-term gravity changes in Chinese mainland from GRACE and ground-based gravity measurements

A long-term （9 years） gravity change in Chinese mainland is obtained on the basis of observation of the ground-based national gravity network. The result shows several features that may be related to sore, large-scale groundwater pumping in North China, glacier-water flow and storage in Tianshan region, and pre seismic gravity changes of the 2008 MsS. 0 Wenchuan earthquake, which are spatially similar to co-seismi, changes but reversed in sign. These features are also shown in the result of the satellite-based GRACE obser vation, after a height effect is corrected with GPS data.

Simultaneous Measurements of Coal Ash Composition by Laser-induced Breakdown Spectroscopy in Different Optical Collection

针对燃煤组分分布不均匀的特性，研究不同收光模式对激光诱导击穿光谱技术同步测量灰成分的影响。选用具有不同灰成分含量梯度的燃煤样品作为检测对象，对比分析同向收光和侧向收光下灰成分组成元素谱线信号探测的强度和稳定性及SiO2、Al2O3、Fe2O3、CaO、MgO和TiO2含量定量分析的精确度。研究结果表明，相同实验条件下同向收光模式的光谱信号稳定性和定量分析精确度更好，检验样品中各灰成分的预测值和参考值之间的拟合度均在0．986以上。而侧向收光模式下探测到的光谱信号强度更强，光谱探测下限可以达到190nm。

Simultaneous density and velocity measurements in a supersonic turbulent boundary layer

A novel technique for simultaneous measurements of instantaneous whole-field density and velocity fields of supersonic flows has been developed.The density measurement is performed based on the nano-tracer planar laser scattering（NPLS） technique,while the velocity measurement is carried out using particle image velocimetry（PIV）.The present experimental technique has been applied to a flat-plate turbulent boundary layer at Mach 3,and the measurement accuracy of the density and velocity are discussed.Based on this new technique,the Reynolds stress distributions were also obtained,demonstrating that this is an effective means for measuring Reynolds stresses under compressible conditions.

A Differential Optical Absorption Spectroscopy Method for X_(CO_2) Retrieval from Ground-Based Fourier Transform Spectrometers Measurements of the Direct Solar Beam

A differential optical absorption spectroscopy （DOAS）-like algorithm is developed to retrieve the column-averaged dry- air mole fraction of carbon dioxide from ground-based hyper-spectral measurements of the direct solar beam. Different to the spectral fitting method, which minimizes the difference between the observed and simulated spectra, the ratios of multiple channel-pairs--one weak and one strong absorption channel--are used to retrieve Xc02 from measurements of the shortwave infrared （SWIR） band. Based on sensitivity tests, a super channel-pair is carefully selected to reduce the effects of solar lines, water vapor, air temperature, pressure, instrument noise, and frequency shift on retrieval errors. The new algorithm reduces computational cost and the retrievals are le^s sensitive to temperature and H20 uncertainty than the spectral fitting method. Multi-day Total Carbon Column Observing Network （TCCON） measurements under clear-sky conditions at two sites （Tsukuba and Bremen） are used to derive Xc02 for the algorithm evaluation and validation. The DOAS-like results agree very well with those of the TCCON algorithm after correction of an airmass-dependent bias.

A Fiber Optic Sensor for the Simultaneous Measurement of Dual-parameter Based on Hydrogel-immobilized Enzyme Complex

A novel fiber optic sensor based on hydrogel-immobilized enzyme complex was developed for the simultaneous measurement of dual-parameter,the leap from a single parameter detecting fiber optic sensor to a fiber optic sensor that can continuously detect two kinds of parameters was achieved.By controlling the temperature from high to low,the function of fiber sulfide sensor and fiber DCP sensor can be realized,so as to realize the continuous detection of dual-parameter.The different variables affecting the sensor performance were evaluated and optimized.Under the optimal conditions,the response curves,linear detection ranges,detection limits and response times of the dual-parameter sensor for testing sulfide and DCP were obtained,respectively.The sensor displays high selectivity,good repeatability and stability,which have good potentials in analyzing sulfide and DCP concentration of practical water samples.

Proposal and Verification of Simultaneous Measurement Method for Three Thermoelectric Properties with Film-Type Thermocouple Probe

A new simultaneous measurement method for the measurement of the three thermoelectric properties with a film-type thermocouple probe was proposed. Seebeck coefficient was measured using the steady-state condi-tion of the differential method. The electrical resistivity was measured us-ing the four-probe method and the thermal diffusivity is measured using the periodic heating method. The effectiveness of the proposed method was verified using constantan as a reference material. After describing the effectiveness of the method, the measurement of three thermoelectric properties of Bi0.3Sb1.7Te3, which is a thermoelectric material, was per-formed.

Simultaneous Measurement of Fringe Visibility and Path Predictability of Wave-Particle Duality

An experimental scheme to simultaneously obtain the information of fringe visibility and path predictability is designed. In a modified Young＇s double-slit experiment, two density filters rotating at different frequencies are placed before the two pineholes to encode path information. The spatial and temporal distributions of the output provide us with the wave and particle information of the single photons, respectively. The simultaneous measurement of the wave and particle information inevitably disturbs the system and thus causes some loss of the duality information, which is equal to the mixedness of the photonic state behind the density filters.

Space- and ground-based CO_2 measurements： A review

The climate warming is mainly due to the increase in concentrations of anthropogenic greenhouse gases, of which CO_2 is the most important one responsible for radiative forcing of the climate. In order to reduce the great estimation uncertainty of atmospheric CO_2 concentrations, several CO_2-related satellites have been successfully launched and many future greenhouse gas monitoring missions are planned. In this paper, we review the development of CO_2 retrieval algorithms, spatial interpolation methods and ground observations. The main findings include: 1) current CO_2 retrieval algorithms only partially account for atmospheric scattering effects; 2) the accurate estimation of the vertical profile of greenhouse gas concentrations is a long-term challenge for remote sensing techniques; 3) ground-based observations are too sparse to accurately infer CO_2 concentrations on regional scales; and 4) accuracy is the primary challenge of satellite estimation of CO_2 concentrations. These findings, taken as a whole, point to the need to develop a high accuracy method for simulation of carbon sources and sinks on the basis of the fundamental theorem of Earth's surface modelling, which is able to efficiently fuse space- and ground-based measurements on the one hand and work with atmospheric transport models on the other hand.

A dual measurement method of strain and temperature

With the rapid development of China's foreign trade, the coastal and inland waterway transport has been increased rapidly. The potential market for marine engines is more and more obvious. The measurement of the engine temperature and strain becomes very important. The fluorescence fiber sensors are broadly used to measure temperature, concentration, and pH value, etc. The fluorescence sensing systems are based on different principles, namely fluorescence intensity, fluorescence intensity ratio, and fluorescence lifetime. The fluorescence lifetime is an effective parameter for sensing purpose, because it is independent of the intensity of the pumping source and does not need expensive narrow-band filters. An experiment system has been established, in which some samples were produced to measure the fluorescence lifetime and temperature characteristics and the relationship of the strain and temperature versus the fluorescence lifetime was achieved at the same time. The experiment result was fitted and analyzed. The test results show that the fluorescence lifetime decreases with the increasing of temperature. The change of fluorescence lifetime with the strain is inconspicuous comparing to that with the temperature.

The Quantitative Density Measurement of Unsteady Flow around the Projectile

Three-dimensional density measurement of unsteady flow field around a sphere is carried out in the ballistic range at Institute of Fluid Science, Tohoku University. Simultaneous multi-angle measurement system using twelve digital cameras is installed in the test chamber of the ballistic range to achieve the three-dimensional density measurement. The Colored-Grid Background Oriented Schlieren (CGBOS) technique using colored-grid background is utilized for the reconstruction of density. The Mach number of the sphere is set to 1.5. The short pulse LEDs to illuminate the backgrounds are also installed in the chamber to capture the unsteady flow field around a flying sphere. Three-dimensional density distribution around a sphere is successfully reconstructed.

New multiplexed system for synchronous measurement of out-of-plane deformation and two orthogonal slopes

We propose a novel system for synchronous measurement of out-of-plane deformation and two orthogonal slopes using a single camera. The linearly polarized reference beam introduced by an optical fiber interferes with the unpolarized object beam to measure the out-of-plane deformation. A modified Mach–Zehnder interferometer is used to measure the two orthogonal slopes of the out-of-plane deformation. One of the object beams of the Mach–Zehnder interferometer is an unpolarized beam, and the other object beam is split into two orthogonal linearly polarized object beams by a polarizing prism. The two beams are orthogonally polarized. Hence, they will not interfere with each other. The two polarized beams respectively interfere with the unpolarized beam to simultaneously measure the two orthogonal slopes of the out-of-plane deformation. In addition, the imaging lens and apertures are respectively placed in three optical paths to independently control the carrier frequencies and shearing amounts. The effectiveness of this method can be proved by measuring two pressure-loaded circular plates.

Simultaneous refractive index and temperature measurements by using dual interference in an all-fiber Mach–Zehnder interferometer

A Fourier analysis applied to the Mach-Zehnder interferometer （MZI） transmission spectrum for simultaneous refractive index （RI） and temperature measurements is proposed and experimentally demonstrated in this Letter. In the fast Fourier transform （FFT） spectrum of the MZI transmission spectrum, several frequency components are generally observed, which means that the transmission spectrum of the MZI is formed by the superposition of some dual-mode interference （DMI） spectra, and each frequency component represents different core-cladding interferences. We can select some dominant frequency components in the FFT spectrum of the MZI transmission spectrum to take the inverse FFT （IFFT）. Then, the corresponding DMI patterns can be obtained. Due to the shift of the wavelength of these DMI spectra with changes in the environmental parameters, we can use the coefficient matrix of these DMI spectra for multi-parameter sensing. In this Letter, two DMI patterns are separated from the resultant transmission spectrum of the MZI. As the RI and temperature change, the shifts of the two DMI patterns with respect to the RI and temperature will be observed. The sensitivities of the RI and temperature are -137.1806 nm/RIU （RI unit） and 0.0860 nm/℃, and -22.9955 nm/RIU and 0.0610 nm/℃ for the two DMIs. Accordingly, it can be used to simultaneously measure RI and temperature changes. The approach can eliminate the influence of multiple interferences and improve the accuracy of the sensor.

Simultaneous blood flow and oxygenation measurements using an off-the-shelf spectrometer

Blood oxygenation and flow are both important parameters in a living body. In this Letter, we introduce a simple configuration to simultaneously measure blood flow and oxygenation using an off-the-shelf spectrometer. With the integration time of 10 ms, flow phantom measurements, a liquid blood phantom test, and an arm cuff occlusion paradigm were performed to validate the feasibility of the system. We expect this proof-of-concept study would be widely adopted by other researchers for acquiring both blood flow and oxygenation changes due to its straightforward configuration and the possibility of multimodal measurement.

“五育并举”视域下高校体育俱乐部教学改革研究

文章在“五育并举”的教育理念下,对高校体育俱乐部教学改革进行了深入研究,并提出了具体的改革策略,包括德育与体育教学的融合、智育与体育教学的结合、体育技能与身体健康的全面提升、美育在体育教学中的渗透以及劳动教育与体育教学的结合。旨在培养全面发展的新时代大学生,提升体育教育的整体质量和学生的综合素质。

对瞬时测频干扰机理的研究

瞬时测频(instantaneous frequency measurement,IFM)接收机是电子侦察中非常重要的测频资源,其结构简单、灵敏度高、侦察频带宽、分辨率高,可以快速测定被测信号的频率,在现代电子战中得到广泛应用。基于IFM微波鉴相器在某一瞬间只能响应一个信号的特性,结合IFM工作原理,研究了一种新的(超过2个信号)对IFM干扰策略,并分析了干扰机理,通过模拟仿真对IFM的干扰效果进行了评估。仿真结果表明:多信号交叠可以对IFM系统产生明显的干扰效果,可以使得其无法测得正确频率,并错误地输出同时到达信号指示。

甲基绿吸收光谱法同时测定糖果中的酒石黄和日落黄

采用甲基绿吸收光谱法同时测定糖果中酒石黄和日落黄含量,并对不同糖果前处理及甲基绿吸收光谱法检测条件进行单因素优化。结果表明,不同糖果前处理条件略有差异。在400~800 nm范围内,Tris-HCl用量1 m L,p H为9.43,甲基绿溶液用量2 m L,反应时间15 min时,甲基绿与酒石黄和日落黄发生显色反应生成离子缔合物,酒石黄-甲基绿在574 nm处测得最大值,标准曲线为y=-0.0035x+0.7009(R^(2)=0.9993),线性范围是0.03~16 mg/L,检出限为0.069 mg/L;日落黄-甲基绿在488 nm处测得最大值,标准曲线为y=0.0378x+0.2104(R^(2)=0.9993),线性范围是0.04~14 mg/L,检出限为0.024 mg/L。对实际样品进行加标回收,酒石黄与日落黄的加标检测均在正常范围内。该方法简便、快速、灵敏度高,可以在不同波长下同时测定硬质糖果中的酒石黄和日落黄的含量。

相邻深基坑开挖相互影响及变形控制研究

以北京城市副中心站综合交通枢纽项目大铁深基坑和02B区深基坑分期开挖为研究对象,采用有限元软件建立了局部精细化模型,对相邻深基坑开挖的变形特性和影响因素进行了研究,并提出了深基坑变形控制措施。研究结果表明,在相邻深基坑近接施工过程中,先开挖的深基坑呈向后开挖深基坑方向移动的趋势,而坑间土地表沉降变形从凹槽形变为双峰形;根据拟合出的变形曲线斜率,可以将相邻深基坑近接施工影响分区划分为:d<2h为强影响区,2h≤d<4h为次影响区,4h≤d<6h为弱影响区,d≥6h为无影响区;为了确保深基坑群施工的整体稳定性,最优开挖顺序是同步开挖,如需分步开挖应优先开挖支护结构刚度较大、支护力度较强的深基坑;该工程可通过及时在逆作区架设上斜撑来实现变形控制的目的。

双燃料喷射器油-气瞬时质量流率同场测量方法

提出一种组合式的测量方法,将其应用于缸内高压直喷柴油/天然气发动机双燃料喷射器瞬态燃料质量流率的研究,实现了两相燃料同场高精度测试.针对传统“动量法”只能获取喷气规律型线无法获取准确质量流率的问题,提出一种平行测试的方法,通过采集测试容腔内的压力变化获取循环喷气量,结合瞬态动量信号得到精确的喷气规律曲线.并对喷射器的计量特征及时间特征进行验证.最后对柴油/天然气双燃料喷射器常用工况进行测试,结果表明:该方法解决了两相燃料难以同场测量的问题,实现了双燃料喷射器油-气瞬时质量流率的精确测量;喷气量测试误差不超过5%,喷油及喷气起始时刻与结束时刻的测试误差不超过0.113 ms,喷油量及喷气量的波动率分别不超过1.4%和2.9%.随着燃料喷射压力增加,喷射器的开启时段减小、关闭时段增加,且内部轴针开启和关闭的速度均大于外部轴针.引燃油的喷射通过影响喷气持续期影响喷气量,先油后气喷射方式下的喷气量在仅喷气方式下的喷气量上、下波动.

基于GZCORS随探随测的地质雷达人防空洞探测技术研究

地质雷达具有无损、抗干扰和浅层分辨率高的优势,是城区人防空洞探测最重要的工具之一。传统的外业流程为:先探后测,再返还室内处理和解释数据。这种分离的作业方式常引起成果解释难度大和返工问题。本文充分发挥GZCORS(广州市连续运行卫星定位综合服务系统)快速测量优势,提出了可随探随测及现场解译的新方法,提高了人防空洞探测效率和准确性,最后用工程实例对该方法的优势进行了验证。