GPS气象学中垂直干分量延时的精确确定(英文)

确定大气中可降水分的含量是 GPS气象学的目的之一。可降水分含量对应于 GPS信号中湿分量延时。现有高精度 GPS软件包只能提供天顶方向的对流层延时 ,但是 ,对流层延时由干分量和湿分量延时组成。因此 ,精确确定干分量延时 ,是分离湿分量延时的关键 ,也是GPS气象学中必不可少的工作。 现有 3种经验模型计算垂直干分量延时 ,即萨氏 (Saastamoinen)模型 ,霍氏 (Hopfield)模型和布兰克 (Black)模型。它们的具体形式分别为 :dz S=0 .2 2 77PF(φ,H )F(φ,H )≡ 1 -0 .0 0 2 6cos(2φ) -0 .0 0 0 2 8H (1 )dz H=1 .5 5 2 (h-H ) PTh≡ 40 .0 82 + 0 .1 4898(T-2 73 .1 6) (2 )dz B=0 .2 3 43 (T-4 .1 2 ) PT (3 )式中 ,垂直干分量延时的单位是 cm;P为气压 ,T为绝对温度 ,H为测站海拔高 ,φ是测站纬度 ;下标 S,H和 B分别代表萨氏 ,霍氏和布兰克模型。现有文献简单认为以上 3种模型没有误差[1,12 ] ,或几毫米的误差[2 ,4～ 6 ,10 ] ,没有详细讨论这些模型的精度。 3种模型中 ,垂直干分量延时是气压和温度观测值的函数 ,式 (1 )～式 (3 )分别对气压和温度微分后 ,并保证其系数达到最大值 ,可以得到垂直干分量延时与气压及温度的微分关系。由此得到 :如果?

局部地区对流层大气垂直干延迟的模型改正

干延迟的精确确定对GPS气象中解算可降水分含量有很重要的作用。根据武汉和探空站Kingspark的探空资料,计算了这两地的实际干延迟量。在这些资料的基础上,用回归分析的方法对这两地的干延迟算式进行了建模和分析,发现该算式的精度优于其他模型。

GPS测量中天顶干延迟的计算方法的研究

大气可降水份的估计是地基GPS气象学的一个主要研究方向。本文介绍了大气折射对GPS测量的影响,简介了两种常用的天顶干延迟分量模型——Saastamoinen模型和Hopfield模型和各种模型的特点。通过对北京、乌鲁木齐、拉萨3个IGS站的气象数据对这两个的天顶延迟干分量模型进行了分析总结。

利用地基GPS技术反演武汉地区大气可降水分

利用武汉地区的探空资料和GPS实测数据,对对流层干分量延迟、对流层加权平均温度进行了检验分析。结果表明,对于武汉地区而言,常用的大气干分量延迟模型(SAAS,Hopfield and Black)存在着1-2 cm的系统误差,这在利用GPS资料估算大气可降水分(PWV)时会引入2-3 mm的误差;对流层加权平均温度与常用的Bevis公式也存在着一定的差异,但这种差异对PWV 结果影响很小。为此,提出了校正对流层干分量延迟的方法,并利用实测数据对该方法进行了检验.实践证明,这种校正方法基本上可以消除常用干分量模型的系统误差。

用GPS监测城市地面沉降的可行性研究

研究了用GPS观测取代常规水准测量方法监测城市地面沉降变化的可行性。在宁波市进行了两期GPS测量和水准测量 ,观测中并采取一定的措施以获得高精度的高程分量。顾及到对流层延迟的影响 ,采用Saas tamoinen模型改正对流层延迟的干分量部分 ,用分段线性方法来估计对流层的湿分量变化。用Bernese软件对数据进行处理 ,获得了毫米级的高程精度。实际算例证明 ,用GPS测量代替水准测量来监测城市地面沉降变化是可行的。

地基GPS准实时反演三峡地区大气可降水量的研究

探讨了利用地基GPS气象学原理反演大气可降水量(precipitable water vapor,PWV)及其变化的可行性。从理论上分析了在缺少地面气象资料时用模型估计气象元素对反演PWV的影响,分析了用IGS超快速星历代替IGS最终精密星历准实时计算PWV的可行性。利用三峡地区13个监测点连续48 h以上的跟踪数据联合国内的几个IGS站,使用GAMIT软件进行了数据处理。

基于遥感生态指数模型的杨凌农业高新技术产业示范区生态环境评价

[目的]定量揭示杨凌农业高新技术产业示范区(简称"杨凌区")生态环境质量的空间分布与变化特征,为该区及类似地区生态环境建设的规划和管理提供科学依据。[方法]本文基于Landsat8卫星影像,利用主成分分析的遥感生态模型进行分析。[结果]2013—2018年,杨凌区生态环境质量总体呈上升趋势,遥感生态指数均值由0.45升至0.50,呈上升趋势的面积为50.77km^2,占全区总面积的38%;杨凌区生态环境状况的空间分布具有向西北优而东南城区差两极扩散的趋势;干度分量对生态指数模型整体影响最大。[结论]杨凌区生态环境质量较差的区域主要集中在城区人为活动密集区和大型工业园区,体现出高度聚集的特点。在杨凌区未来规划和发展中,应控制并有效减小裸地和建设用地面积,重视生态景观和城区绿化。

利用地基GPS测定沙尘暴的含沙量

准确掌握地球大气中沙尘的分布,了解沙尘移动趋势对天气现象、气候变化、数值预报有重要的理论研究及实用价值。本文详细地论述了利用地基GPS方法观测大气中沙尘含量的原理。论述了在地基GPS技术中观测站遥测大气中沙尘含量的理论基础,建立了利用GPS观测数据计算大气层沙尘含量的理论模型,导出了相应的计算公式。

Dynamic Accumulation of β-carotene and Dry Matter in Orange-fleshed Sweetpotato [Ipomoea batatas(L.) Lam] and Their Correlation Analysis

Using three orange-fleshed sweetpotato varieties as experimental materials,16 economic traits at 60 d,75 d,90 d,105 d,120 d and 135 d after planting were measured,so as to revealing the dynamic variations of β-carotene and dry matter accumulation in roots and their relationships with economic traits in orangefleshed sweetpotato.The results showed that the dynamic variations of β-carotene accumulation in tubers varied hugely among different varieties.Interesting,the βcarotene content of all three varieties showed a significant decrease after 120 d,while the dry matter content of them performed a similar ＂fluctuation-type＂.Correlation analysis indicated that β-carotene content of three orange-fleshed sweetpotato varieties had no significant correlation with dry matter content and photosynthetic parameters,but the correlation with other economic traits also varied among varieties.

不同定义的湿位涡分析及在台风中的诊断

本文对不同定义的湿位涡做了理论分析,并利用1522号台风"彩虹"的数值模拟结果对各种湿位涡进行了诊断。主要结论有:经典湿位涡、广义湿位涡和改进湿位涡的差异主要是由不同定义的位温造成的,相当位温、广义位温和修改位温的构成均是在位温基础上添加一显含水汽的附加量;经典湿位涡、广义湿位涡和改进湿位涡的构成均能分为干、湿分量两部分,其干分量表达式相同,都与Ertel干位涡的定义一样,水物质相变潜热的影响隐含在位温中;不同定义湿位涡的本质差异表现在不同的湿分量上,湿分量的表达式中显含了水物质的作用。对台风的诊断分析发现,改进湿位涡分布与Ertel干位涡非常相似,呈现中空分布的位涡塔结构,大值区对应眼墙内侧,改进湿位涡湿分量与经典湿位涡的湿分量分布相似,只是湿分量的绝对值更小,这反映了改进湿位涡既能保持干位涡的分布特征,其分布和演变可反映台风的结构和演变,又能合理地体现水汽分布的影响,所以在台风诊断中有更广泛的应用前景。经典湿位涡在低层表现为负值,这与水汽梯度的分布关系很大,但与垂直速度、潜热加热大值区等都没有很好的匹配关系,用其分析台风结构和演变具有一定局限性;广义湿位涡其形式较复杂,仅在近饱和区域才能发挥其诊断优势。

Relationship Between Differential Interference Angle and Parameter of Experiment in Molecular Beam

Collisional quantum interference （CQI） was observed in the intramolecular rotational energy transfer in the experiment of the static cell, and the integral interference angles were measured. To observe more precise information, the experiment in the molecular beam should be taken,from which the relationship between the differential interference angle and the scattering angle can be obtained. In this paper, the theoretical model of CQI is described in an atom-diatom system in the condition of the molecular beam, based on the first-Born approximation of time-dependent perturbation theory, taking into accounts the long-range interaction potential. The method of observing and measuring correctly the differential interference angle is presented. The changing tendency of the differential interference angle with the impact parameter and relative velocity is discussed. The changing tendencies of the differential interference angle with the parameter of experiment in the molecular beam, including the impact parameter and the velocity are discussed. This theoretical model is important to understand or perform the experiment in the molecular beam.

Rice Repetitive DNA Sequence RRD3:a Plant Promoter and Its Application to RNA Interference

Previously, a moderately repetitive DNA sequence （RRD3） was cloned from rice （Oryza sativa L.） by DNA renaturation kinetics. Sequence analysis revealed several conserved promoter motifs, including four TATA-boxes and a CAAT-box, and promoter activity was shown in Escherichia coli and mammalian expression systems. Here, we inserted the RRD3 fragment into the plant promoter-capture vector, pCAMBIA1391Z, and examined whether the RRD3 fragment has promoter activity in plants. Transgenic tobacco and rice calli both showed β-glucuronidase （GUS） activity, indicating that RRD3 can act as a promoter in both monocot and dicot plants. Based on the promoter characteristic of RRD3, we designed a plant universal binary vector, pCRiRRD3, which is suitable for performing researches on plant RNA interference. This vector has two multiple cloning sites to facilitate sense and antisense cloning of the target sequence, separated by an intron fragment of 200 bp. The efficiency of the vector for gene silencing was assayed by histochemical and quantitative fluorometric GUS assays in transgenic tobacco. These research results suggested that this plant RNAi vector pCRiRRD3 can effectively perform gene silencing researches on both monocot and dicot plants.

Interferences in Photodetachment of a Negative Molecular Ion

The photodetachment of a negative molecular ion is studied theoretically using a two-center model. The detached electron wave function is obtained as a superposition of two coherent waves originating from each center. The photo-detached electron flux is evaluated on a screen placed at a large distance from the negative molecular ion. The electron flux on the screen displays strong interferences, the peak positions are related to the distance between the two centers in the negative molecular ion. We a/so obtained a simple analytical formula for the total photodetachment cross section. It approaches one and two times of the cross section for the one-center system in the high and lowphoton energy limits respectively.

Effect of coal moisture content on coke’s quality and yields of products during coal carbonization

The coal with low moisture during carbonization could not only increase the yield of coke,but also promote the coke quality and reduce the energy consumption.In this paper,the influence of the moisture in the blend coal(1.8%10.13%)on the product yields and coke quality during coal carbonization were investigated.The results show that the coke yield is increased from 75.90%to 77.16%,and the coke qualities such as coke strength after reaction with CO2(CSR),coke reactivity index(CRI),fragmentation index(M25)and abrasion index(M10))are also improved when the moisture of the blend coal decreases from 10.13%to 1.80%in a bench scale reactor.Due to the secondary reaction,tar become lighter when the moisture is decreased.In order to further prove the above results,the blend coal with 1.8%and 9%10%(common moisture used in coke plant)moisture is carbonized in a coke oven with 6 m height,the results show that CRI are 23.4%and 27.3%,CRS are 67.1%and 62.2%under 1.8%and 9%10%moisture of blend coal.Moreover,the variation of the moisture in blend coal has a limited influence on dust emission at the ascension pipe and the charging car.

Novel technology on preparation of double-layered pellets for sulfur and arsenic-bearing gold concentrates

Double-layered pellet （DLP） roasting is a novel pretreatment method for sulfur and arsenic-bearing gold concentrates. In this process, preparation of DLPs is a fundamental step which is required to produce DLPs with favorable mechanical strength and thermal stability. Studies were carried out to investigate the affecting factors and conditions on the preparation and properties of DLPs. The results show that moisture content has significant influence on DLPs preparation. With the increase of moisture content in the range of no more than 9.8%, drop resistance and compressive strength of green DLPs are raised and the pelletizing dynamics is improved accordingly. The optimum conditions are determined as moisture content of 9.8%, coating time of 14-16 min, drying temperature 〈80 ℃and drying gas velocity 〈1.2 m/s. When DLPs prepared under these conditions are roasted at 600 ℃ for 1 h, favorable removal and solidifying rates can be obtained, in which the removal rates of arsenic and sulfur are 94.38% and 82.55%, and the solidifying rates of arsenic and sulfur reach 99.62% and 99.79%, respectively. These results promise industrial application of DLP roasting.

Prime Factorization in the Duality Computer

We give algorithms to factorize large integers in the duality computer. We provide three duality algorithms for factorization based on a naive factorization method, the Shor algorithm in quantum computing, and the Fermat＇s method in classical computing. All these algorithms may be polynomial in the input size.

Novel Distributed Fiber Bragg Grating Sensing System Based on M-Z Interferometer

One of the problems in using grating sensors is how to measure a small Bragg wavelength shift accurately. Nowadays demodulation techniques are mainly based on the edge filter, tunable filter, or interferometric scanning methods. Interferometric demodulation is widely accepted as the technology which can provide the high sensitivity. An interrogation system using the interferometric scanning method is presented, in which an unbalanced fiber M-Z interferometer is used as the wavelength scanner for temperature measurement. A novel fiber Bragg grating sensor system based on M-Z interferometric demodulation technique is presented in this paper. The temperature sensitivity measured in the experiment is almost consistent with that obtained from the theoretic calculation.

Throughput Analysis of Dynamic Spectrum Anti-Jamming Multiple-Access in HF Communication Systems

A multiple-access networking scheme based on the new dynamic spectrum anti-jamming system is proposed in this paper. The network consists of a center node and multiple user nodes. The center node detects spectrum holes in the operation band periodically according to the user performance target. Detected spectrum holes are allocated to users who request communication. Throughput of this networking scheme is analyzed over a high-frequency(HF) interference channel. The effect of error correction coding and spectrum hole information transmission error is discussed. Throughput of this scheme and conventional frequency-hopping multiple-access(FHMA) scheme are compared. Results show that user performance increase leads to throughput decrease, which can be offset by error correction coding. If spectrum hole information transmission is in error, the throughput is not affected much as long as the bit error rate is below 10-2. Furthermore, throughput of this scheme is obviously superior to the throughput of FHMA scheme.

Further Study of A-Related Quantum Interference of H-State Diatomic on Collision-Induced Rotational Energy Transfer

In our previous theoretical studies [Meng-Tao Sun, Yong-Qing Lee, and Feng-Cai Ma, Chem. Phys.Left. 371 （2003） 342], we have reported the quantum interference on collision-induced rotational energy transfer on CO （A ^1 Π,v = 3） with inert gases, which originates from the difference between the two A-related collision potential energy surfaces. The interference angle, which measures the degree of coherence, is presented in this paper. Based on the time-dependent first order Born approximation, taking into account the anisotropic Lennard-Jones interaction potentials, the relation of the interference angle with the factors, including experimental temperature, partner, and rotational quantum number, are obtained. The changing tendencies with them are discussed. This theoretical model is important to understanding and performing this kind of experiment.

Xeno-free derivation and culture of human embryonic stem cells： current status, problems and challenges

Human embryonic stem cells （hESC） not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.