Properties and emergence patterns of bipolar active regions

Patterns in the properties of bipolar active regions are determined throughout Cycle 21. Active regions that emerged on the visible hemisphere were identified on NSO/KP full-disk magnetograms during 29 solar rotations selected from 1975 through 1986. The bipolar active regions are included only once in this sampling; their properties are derived at the time of maximum development. In order to study an unbiased sample over the entire range of areas larger than 2.5 square degrees (or 373 Mm²), their counts are corrected for size-dependent effects that reduce the chance of their identifications.The size distribution of bipolar active regions is a well-defined function that decreases with increasing size. Except for the smallest regions, the shape of the size distribution is independent of the phase of a cycle, only the scaling factor varies. The shape of the size distribution function for bipoles emerging within existing sunspot regions is virtually the same as that for bipoles emerging outside existing regions. Over the cycle, at least 44% of the regions larger than 3.5 square degrees emerge within existing sunspot regions. Hence, the rate at which new regions emerge is much higher within the boundaries of existing sunspot regions than it is in the activity belts outside existing regions. For regions emerging outside of existing sunspot regions, this rate increases by a factor of 3.5 from cycle minimum to maximum, while for new bipoles within existing active regions, the emergence rate varies with a significantly lower magnitude.Through the cycle, for regions in all size bins, the emergence frequencies appear to vary in phase. The frequencies increase by a factor of more than 8 from minimum to maximum for regions larger than 3.5 square degrees, but no more than 4.7 for the smaller regions. Short-term variations in the emergence frequency of regions do not necessarily occur simultaneously for regions of all sizes, implying that the size distribution is variable on time scales of less than six rotations.     

The influence of a photospheric spectrum of turbulence on the profiles of weak Fraunhofer lines

We assume that the motion field in the solar photosphere is described by a spectrum of turbulence, defined by suitably chosen parameters. For various values of the spectral parameters we compute average (i.e. averaged over a sufficiently large part of the photosphere) profiles of weak Fraunhofer lines. The resulting profiles which represent the distribution function of line-of-sight velocity components as modified by the transfer of radiation through the atmosphere, are thereupon still broadened by a function representing the influence of the distribution function of the granulation cell sizes. The resulting functions should be compared with the distribution function of line-of-sight velocity components as derived from observations, in order to arrive at an observational derivation of the parameters of the photospheric spectrum of turbulence.     

Microfocus X-ray computed tomography analysis of corroded glass objects

Microfocus X-ray computed tomography (µCT) is a useful tool for non-destructive analysis of corroded archaeological glass objects and for monitoring restoration and conservation processes for these materials. This was demonstrated by µCT analysis of artificially corroded laboratory-produced glasses and corroded archaeological glasses retrieved from soil environments. Corrosion layers with a thickness of 20 µm or more can be detected as areas with lower X-ray attenuation values than the non-corroded glass. Features that are revealed by µCT analyses include the degree and patterns of corrosion and the presence of various internal structures in the corrosion layers. The study of restored corroded glasses demonstrates that mechanical and laser cleaning can be monitored efficiently. The study of consolidation practices, using test objects, requires the use of additives to increase X-ray attenuation values of the organic compounds that are used.     

Average sand particle trajectory examined by the Raindrop Detachment and Wind‐driven Transport (RD‐WDT) process

Recent studies of soil loss by the integrated action of raindrop impact and wind transport have demonstrated the significance of this mechanism. This paper presents data obtained during wind‐tunnel experiments examining the ‘Raindrop Detachment and Wind‐driven Transport’ (RD‐WDT) process to investigate average sand particle trajectory and the spatial extent at which the process operates. In the experimental design, at the same time as the horizontal wind velocities of 6·4, 10, and 12 m s^–1 passed through the tunnel, rainfall was simulated falling on very well sorted dune sand. The aspect and slope of the sand bed was varied to reproduce both windward (Ww) and leeward (Lw) slopes of 4º and 9º with respect to the prevailing wind direction. The average sand particle trajectories by the RD‐WDT process ( ) were estimated by a mass‐distribution function, which was integrated over a 7‐m uniform slope segment. The results showed that depended statistically upon the wind shear velocity (u*), and the effect of the slope gradient (θ) was insignificant on . This was different from that of the windless rain process ( ), ‘Raindrop Detachment and Splash‐driven Transport’ (RD‐ST), the spatial range of which relies strongly on θ. Additionally, was approximately 2·27 ± 2·2 times greater than the average path of a typical saltating sand particle of the rainless wind ( ), ‘Wind Erosion Saltation Transport’ (WE‐ST). Copyright © 2009 John Wiley & Sons, Ltd.     

考虑随机模型精化的精密GPS动态定位新方法

GPS动态定位要求建立函数模型和随机模型。函数模型描述的是观测值和待估参数之间的物理和几何关系，随机模型描述了GPS观测值的统计特征，并通过观测值的方差协方差给定了每个观测值对最后的定位结果的贡献。正确给定函数模型和随机模型对于GPS定位结果的估计和观测值的粗差探测均至关重要。由于有各种误差存在于伪距和载波相位观测值中，一般GPS动态定位模型均采用双差观测值来构建函数模型。有时候，仔细地使用单差观测值，较之双差观测值有更多的优点，给出了选用单差观测值的理由。但是单差观测值给函数模型带来了接收机钟差，如果直接使用单差观测方程，设计矩阵是奇异的。为了解决这个问题，将伪距观测值中接收机钟差项和接收机延迟项合并为一个新的未知参数。至于载波相位观测值，首先选定一个参考卫星，然后在观测方程的右端同时增加一正一负的参考卫星单差整周模糊度，将正项与接收机钟差项和接收机延迟项合并为一个新的未知参数，将负项和原观测方程中的单差整周模糊度项合并为双差整周模糊度，而参考卫星观测方程的模糊度项则为零，这样无须组建双差观测值，软件实现较容易，也可以直接使用LAMBDA法求整周模糊度，最终也解决了观测方程奇异的问题。准确理解观测值的统计特征是建立GPS随机模型的基础，长期以来GPS商业软件均采用简化模型。关于GPS随机模型的研究远没有函数模型那样受到广泛关注，静态GPS定位可以采用方差协方差分量估计等严密的方法，而动态定位无法承担方差协方差分量估计的计算负担。GPS观测值的信噪比(SNR)是GPS接收机观测过程中的副产品，影响SNR值的因素，如大气层、多路径、接收机内部电路等，也正好是GPS观测值的误差源，因此GPS观测值的方差与SNR存在一定的对应关系。利用这个对应关系来精化GPS随机模型。为了验证本文采用的函数模型的正确性和随机模型的有效性，我们对1999年的一次实测数据(包括零基线和短基线)进行了试算。与零基线的真值和GPSurvey 2．35处理的短基线静态结果比较，表明使用的函数模型是正确的。简化随机模型和精化随机模型处理的结果比较说明精化模型提高了基线处理的精度，同时说明了研究GPS随机模型精化的必要性。     

TBT-pollution in the Gulf of Thailand: A re-inspection of imposex incidence after 10 years

Imposex in neogastropods was used to determine the relative TBT distribution in the Gulf of Thailand in 2006. To identify the imposex prevalence, 8757 specimens, belonging to 22 species from five families of neogastropods, were collected at 56 sites in 13 sample areas. These areas were located between the Bight of Bangkok in the north and the Malaysian border in the south. A contamination model was developed to compensate for differences in TBT sensitivity among species and to make comparisons among areas. At every area imposex was found in neogastropods. The highest incidence was in the east side of the Bight of Bangkok off Si Racha and Pattaya and in the southern part around Pattani. The same areas showed the highest frequency of imposex in 1996. While the frequency of imposex appeared to have slightly decreased in these areas, increases were found elsewhere. In Pattani Province this could be related to dumping of highly polluted harbour sediments in the shallow coastal area. The overall frequency of imposex in the Gulf of Thailand significantly increased from 1996 to 2006.     

Heat-capacity measurements and absolute entropy of ɛ-Mg2PO4OH

The low-temperature heat capacity of -Mg₂PO₄OH was measured between 10 and 400 K by adiabatic calorimetry. No phase transition was observed over this temperature range. A relative enthalpy increment of 22,119 J mol^–1 and an absolute entropy value of 127.13±0.25 J mol^–1 K^–1 at 298.15 K are derived from the results. The low-temperature heat-capacity data are compared with the DSC data obtained from 143 K to 775 K and show marginal differences in the common temperature range. The latter data are fitted by the polynomial

The nation-state and the river: Spaces and times on Dutch rivers, 1795-1814

Nothing indeed demonstrates more forcefully the extent to which Dutch water management corresponds to the nature and the needs of the Dutch people and their land, and how it has emerged there from in a natural fashion than the fact that the revolutionaries of 1795, despite being so intoxicated by their unexpected victory and sudden power that they overturned everything … nonetheless refrained from laying hands on institutions whose extreme antiquity would in those days have provided more of an excuse to abolish than to preserve them (J.W. Welcker, De Noorder-Lekdijk Bovendams en de doorsteking van den Zuider-Lekdijk bij Culemborg 1803-1813. Een bijdrage tot de geschiedenis van den Nederlandschen Waterstaat geschetst en met onuitgegeven stukken toegelicht (‘s-Gravenhage: 1880), p. 2).