用微波辐射技术检测学生学习疲劳的实验研究

学生长期处于学习状态,容易产生脑力疲劳,它将影响其生长发育和健康,因此研究和预防学习疲劳是儿少卫生工作中的一个重要课题。关于脑力疲劳的客观评定方法,目前国内外常用的方法中,有的夹杂着主观因素,有的与学生的注意力集中的配合状况密切相关,有的还受熟练程度的影响,客观性不太理想。 随着航天技术的发展,微波遥感技术在军事、

微波辅助萃取十大功劳叶中的小檗碱

利用间歇式微波辅助萃取装置 ,对提取阔叶十大功劳叶中的药用有效成分小檗碱进行了研究。选择并确定了萃取液中盐酸小檗碱的分析方法 ( Al2 O3 柱层析 -紫外分光光度法 ) ;选取了甲醇、乙醇、乙醇 -水 ( V/ V=9∶ 1 )为溶剂 ;微波辐射量为 2 ,4,6min;处理比 ( g/ m L)为 1∶ 40 ,1∶ 60 ,1∶80 ;利用正交实验设计考察了不同湿分原料的微波辅助萃取效率 。

天地两重忧

天忧日积月累的“太空垃圾”。如今的太空,已经“星满为患”。各国发射人造卫星,每次都有火箭残骸等碎块变成太空垃圾而飞驰于宇宙空间。即使是一个很小很小的碎片,也会像一颗流弹。

Retrieval algorithm of sea surface wind vectors for WindSat based on a simple forward model

WindSat/Coriolis is the first satellite-borne polarimetric microwave radiometer, which aims to improve the potential of polarimetric microwave radiometry for measuring sea surface wind vectors from space. In this paper, a wind vector retrieval algorithm based on a novel and simple forward model was developed for WindSat. The retrieval algorithm of sea surface wind speed was developed using multiple linear regression based on the simulation dataset of the novel forward model. Sea surface wind directions that minimize the difference between simulated and measured values of the third and fourth Stokes parameters were found using maximum likelihood estimation, by which a group of ambiguous wind directions was obtained. A median filter was then used to remove ambiguity of wind direction. Evaluated with sea surface wind speed and direction data from the U.S. National Data Buoy Center （NDBC）, root mean square errors are 1.2 rn/s and 30~ for retrieved wind speed and wind direction, respectively. The evaluation results suggest that the simple forward model and the retrieval algorithm are practicable for near-real time applications, without reducing accuracy.

Methodology for Determination of Moisture Distribution

The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials using a non-destructive method while using microwave radiation. Available documents are usually focused on the description of diffusion and similar works are based on the difference of partial pressure [I]. Publication will introduce experimental measurements the transport of humidity in porous material in a non-stationary state. As a result may be obtaining of data for formulation of humidity profiles with the help of experimentally built measuring apparatus without influence of human factor. Aim is verification of mentioned method of measurement for description of moisture parameters building materials applicable for practice. Complication in the determination of moisture parameters is various porous textures and the remains effect of condensation and transport influence of liquid moisture by diffusion in porous material. At the present time does not exist for standard use computational theory to description of transport of dampness in building materials. Moisture in porous medium is transported by the help of the capillary forces. The liquid moisture gradient is an indicator of moving of liquid moisture in a porous material through capillaries. This phenomenon is called capillary conductivity of moisture. Purpose presents measurement of material specimen for formulation of capillary conductivity coefficient and its dependence on moisture. The specimen of porous material is subjected to an isothermal moisture intake process. The transient moisture distribution in the specimen during the process is determined, at different stages of the process. Methodology of data scanning with the help of microwave radiation and data processing is processed for numerical computation on the basis known physics laws. The outputs of measurements can be used for evaluation of physical properties of building materials.

The development of an algorithm to enhance and match the resolution of satellite measurements from AMSR-E

Microwave radiometers have many applications because of their penetration ability. However, two major problems remain that obstruct the development of microwave research. One factor that limits their commercial application is the relatively low resolution of microwave radiometers. The other is the non-uniform spatial resolution for each frequency of the radiometer. The resolution mismatch becomes a critical consideration when observations at two or more frequencies must be combined. In this paper, we have used the Backus-Gilbert method to solve these two problems, while AMSR-E is chosen as the research object. First, we derived the Backus-Gilbert method in detail. The simulated data were then used to decide the optimum parameters in the Backus-Gilbert method. To enhance the resolution, the Backus-Gilbert method has been applied to the AMSR-E data, which covered the Mexico Gulf and the Amazon River. After resolution was enhanced, detailed information was obtained and compared with visible high resolution data. To match the resolution, the AMSR-E data from the Oklahoma Little Washed were used to compute the Microwave Vegetation Index (MVI), which was developed by J. C. Shi. Compared to the original MVIs, the information contained in the MVIs that were processed by the Backus-Gilbert method is more reliable.

Assessment and analysis of microwave emissivity and transmissivity of a deciduous forest towards the estimate of vegetation biomass

Forests play an important role in the global carbon cycle and have a potential impact on global climatic change.Monitoring forest biomass is of considerable importance in understanding the hydrological cycle.Because of the problem of dense forest cover,no reliable method with which to retrieve soil moisture in forest areas from the microwave emission signature has been established.All of these issues relate to the microwave emissivity and transmissivity characteristics of a forest.The microwave emission contribution received by a sensor above a forest canopy comes from both the soil surface and the vegetation layer.To analyze the relationship of forest biomass and forest emission and transmissivity,a high-order emission model,the matrix-doubling model,which consists of both soil and vegetation models,was developed and then validated for a young deciduous forest stand in a field experiment.To simulate the emissivity and transmissivity of a deciduous forest in the L and X bands using the matrix-doubling model,the parameters of components of deciduous trees when the leaf area index varies from 1 to10 were generated by an L-system and a forest growth model.The emissivity and transmissivity of a forest and the relationships of these parameters to forest biomass are presented and analyzed in this paper.Emissivity in the L band when the leaf area index is less than 6 and at viewing angles less than 40°,and transmissivity in the L band are the most sensitive parameters in deciduous forest biomass estimation.

Revisit of constraints on holographic dark energy:SNLS3 dataset with the effects of time-varying β and different light-curve fitters

Previous studies have shown that for the Supernova Legacy Survey three-year （SNLS3） data there is strong evidence for the redshifl- evolution of color-luminosity parameter β of type Ia supernovae （SN Ia）. In this paper, we explore the effects of varying β on the cosmological constraints of holographic dark energy （HDE） model. In addition to the SNLS3 data, we also use Planck distance prior data of cosmic microwave background （CMB）, as well as galaxy clustering （GC） data extracted from Sloan Digital Sky Survey （SDSS） data release 7 and Baryon Oscillation Spectroscopic Survey （BOSS）. We find that, for the both cases of using SN data alone and using SN＋CMB＋GC data, involving an additional parameter of β can reduce χ^2 by - 36; this shows that β deviates from a constant at 6σ- confidence levels. Adopting SN＋CMB＋GC data, we find that compared to the constant β case, varying β yields a larger fractional matter density Ωm0 and a smaller reduced Hubble constant h; moreover, varying β significantly increases the value of HDE model parameter c, leading to c ≈ 0.8, consistent with the constraint results obtained before Planck. These results indicate that the evolution of β should be taken into account seriously in the cosmological fits. In addition, we find that relative to the differences between the constant β and varying β（z） cases, the effects of different light-curve fitters on parameter estimation are very small.