Smoothing GPS carrier phase double differences using inertial measurements for high performance applications

This paper will describe an enhancement to the GPS double difference carrier phase measurements on a single airborne platform by smoothing them with inertial measurements while preserving the dynamic bandwidth. This enhancement will reduce the impact of carrier phase multipath and carrier phase noise on baseline determination between multiple antennas on an aircraft when in flight. This type of measurement system has numerous applications where platform pointing and relative body motion must be determined at the mm-level for applications such as sensor stabilization, Synthetic Aperture Radar, long range RADAR (i.e. angle-of-arrival measurements). Lower noise levels (mm-level and below) enable more performance to the stabilized system such as increased aperture for longer range, operation at higher frequencies, and more image resolution. The focus of this paper will be on a technique to provide this enhanced performance for these various applications using the available navigation systems. Additionally, this type of smoothing can effectively remove the additional noise induced by carrier phase measurement differencing. The noise level of a double or triple difference can be reduced below that of the raw measurement. A complimentary synthesized double difference quantity with ultra-low-noise characteristics will be used to smooth the GPS carrier phase double difference measurements without losing dynamic bandwidth since it follows the airborne dynamics. Flight test data will be presented to demonstrate the performance improvement in the midst of aircraft dynamics. Results will show that the noise reduction follows the theoretical prediction.     

Numerical modeling of stress-permeability coupling in rough fractures

A numerical model is described for coupled flow and mechanical deformation in fractured rock. The mechanical response of rock joints to changes in hydraulic pressure is strongly influenced by the geometric characteristics of the joint surfaces. The concept of this work is to combine straightforward finite element solutions with complex and realistic fracture surface geometry in order to reproduce the non-linear stress-deformation-permeability coupling that is commonly observed in fractures. Building on the numerous studies that have expanded the understanding of the key parameters needed to describe natural rough-walled fractures, new methods have been developed to generate a finite element mesh representing discrete fractures with realistic rough surface geometries embedded in a rock matrix. The finite element code GeoSys/Rockflow was then used to simulate the coupled effects of hydraulic stress, mechanical stress, and surface geometry on the evolving permeability of a single discrete fracture. The modeling concept was experimentally verified against examples from the literature. Modeling results were also compared to a simple interpenetration model.     

Temporal and Spatial Variability of Freshwater Plumes in a Semienclosed Estuarine–Bay System

While the physical forcing mechanisms that govern the outflows of major rivers throughout the world are well documented in the literature, comparably less research has been done to examine the mechanisms that govern the contributions of small rivers and streams to coastal ocean systems. These rivers and streams provide a direct means for the transport of anthropogenic and terrigenous materials from watersheds to coastal oceans. This study describes the temporal and spatial variability of freshwater plumes from Kaneohe Stream, Hawaii, USA, after storm events in the Kaneohe Bay watershed. Freshwater plumes were examined using a combination of fixed moorings, synoptic shipboard surveys, and lagrangian surface drifters. Data sets were collected over the course of 19 months from August 2005 to March 2007 with particular attention paid to storms during the boreal winters. Stream discharge and duration were found to exert a primary control on plume persistence in the southern Kaneohe Bay system. Time series data show a strong coherence between wind forcing and surface currents, which, in combination with data derived from shipboard and aerial surveys, indicate that the spatial variability of freshwater plumes is primarily determined by atmospheric forcing.     

A climate trend analysis of Ethiopia: examining subseasonal climate impacts on crops and pasture conditions

Ethiopia experiences significant climate-induced drought and stress on crop and livestock productivity, contributing to widespread food insecurity. Here, we present subseasonal crop water stress analyses that indicate degrading, growing conditions along Ethiopia’s eastern highlands, including productive and populated highland regions. These seasonally shifting areas of increasing water stress stretch from the north to south across eastern Ethiopia, intersecting regions of acute food insecurity and/or high population. Crop model simulations indicate that between 1982 and 2014, parts of eastern Amhara and eastern Oromia experienced increasing water deficits during the critical sowing, flowering, and ripening periods of crop growth. These trends occurred while population in these regions increased by 143% between 2000 and 2015. These areas of enhanced crop water stress in south-central Ethiopia coincide with regions of high population growth and ongoing crop extensification. Conversely, large regions of relatively unpopulated western Ethiopia are becoming wetter. These areas may therefore be good targets for agricultural development.     

Process and response in contemporary Urban development: Melbourne in the 1980s

In the current climate of economic restructuring, technological change and demographic transition, cities such as Melbourne are experiencing new and different pressures. That these pressures are exerted upon an already developed urban structure, and within a particular planning and administrative structure, means that outcomes vary from city to city. However, Melbourne, in common with a number of cities, is facing substantial changes in many aspects including the nature and location of economic enterprise, the structure and composition of the population, and the relative competitive strength of the region. The result is that Melbourne has experienced problems both in its ability to hold and continue to attract activities which provide a basis for further growth and development, and in the exacerbation of internal variations in the level of opportunity and quality of life available to different groups in the population.

The role of government has traditionally been relatively minor in guiding the process of urban development in Australia. However, since 1982 the state government in Victoria has made a concerted effort to reorganise and coordinate urban management and planning, integrating these with other strategic initiatives relating to economic development and social justice. While there is evidence that many of the initiatives are proving effective, there are still a number of problem areas. Some of these, such as global economic trends, are beyond the scope of government to control. Others, such as measures to facilitate the development of new economic activities, are within the power of government, but require careful formulation and management. The extent to which such measures are successful depends upon both the correct identification of problems and solutions, and the ability of government to gain a wide degree of acceptance of its goals. It is these that will prove the most difficult to achieve in the long run.     

Political change and local objectives: observations from rural Wales

Summary In this article, we argue that the spatial reorganization of local government structures may pose a significant threat to fragile local cultures. A recognition at the national level that policy structures are culturally specific (and not converging) is not always conceded at the very local level. Drawing on observations from Wales, we show how political change brings the danger of cultural neglect.     

Transportation energy demand: Model development and use

This paper describes work undertaken and sponsored by the Energy Commission to improve transportation energy demand forecasting and policy analysis for California. Two different, but related, modeling systems are presented: the Vehicle Transactions Simulator and the Activity and Mobility Simulator. In addition, the paper discusses some of the important energy issues and analysis that will be addressed in the next few years with the help of these models. This paper was prepared as the result of work at the California Energy Commission. It does not necessarily represent the views of the Energy Commission, its employees, or the State of California.     

The EC 14026 stars — IX. KPD 2109+4401

The results of 37 h of high-speed photometry of KPD 2109+4401 are described. At least five periodicities in the range 182–198 s are consistently present in the observations, with amplitudes in the range 1–6 mmag. Results of simultaneous multicolour high-speed photometry with the Stiening photometer are also presented; these data could in principle be used for mode identification of the periodicities. The results of a preliminary study suggest that the pulsations may all be ℓ = 1 and 2 modes. Properties of the star are compared with those of the other EC 14026 stars.     

A U-series study of lavas from Kamchatka and the Aleutians: constraints on source composition and melting processes

New data are presented for lavas from the Kamchatka Peninsula and the Aleutian arc. Radiogenic isotopes are strikingly homogeneous in the Kamchatka lavas and although incompatible trace element ratios exhibit much greater variability, much of this appears to result from shallow level, crystal fractionation. The data reveal little systematic across-arc change in radiogenic isotopes or trace element ratios. The Nd and Pb isotope data overlap those for Pacific MORB and limit the amount of sediment that could be incorporated in the mantle source region to <1% which is insufficient to account for the observed La/Ta ratios (50–68) in the high-MgO lavas. The lack of a positive correlation between La/Ta and depth to the slab suggests that melt–wall rock interaction was not important in controlling this ratio. Instead it is inferred that La/Ta increased during partial melting and that D_La/D_Ta = 0.11–0.06, possibly due to residual amphibole. Ba, U, Sr and Pb were added to the source by an aqueous fluid from the subducting slab and its inferred isotopic composition indicates that this fluid was derived from the altered oceanic crust. The addition of U resulted in a large range of (²³⁸U/²³²Th) from 0.79–2.48 similar to that observed in the Mariana and Lesser Antilles island arcs. However, (²³⁰Th/²³²Th) = 0.79–2.34, and the majority of samples lie close to the equiline indicating that the time since U/Th fractionation is generally ≥150 thousand years. The large width of the volcanic zone is assumed to reflect protracted fluid release from the subducting slab over the depth interval 170–380 km possibly coupled with extension across the Central Kamchatka Depression. The data from the Aleutians contrast strongly with those from Kamchatka. Radiogenic isotope data indicate that the Aleutian lavas contain a significant recycled sedimentary component, consistent with elevated ¹⁰Be/⁹Be ratios. The Aleutian lavas have (²³⁰Th/²³²Th) = 0.79–2.34 and exhibit a significant range of U/Th disequilibria [(²³⁸U/²³⁰Th) = 0.75–1.01]. However, ¹⁰Be/⁹Be is positively correlated with (²³⁸U/²³⁰Th) suggesting that the ¹⁰Be signal was carried by the aqueous fluid from the slab. The U/Th disequilibria for the Aleutian lavas lie close to a 30 thousand year reference line suggesting that this fluid was released from the slab ∼30 thousand years ago similar to recent estimates from the Lesser Antilles, Marianas, and Tonga-Kermadec island arcs from which it is inferred that fluid addition was the trigger for partial melting. Given that the rate of convergence in Kamchatka is similar to that in the Aleutians, Marianas and Tonga-Kermadec the inferred greater time since␣fluid release in Kamchatka requires further investigation. Received: 24 September 1997 / Accepted: 7 July 1998     

Is Lognormal Kriging Suitable for Local Estimation?

Lognormal kriging was developed early in geostatistics to take account of the often seen skewed distribution of the experimental mining data. Intuitively, taking the distribution of the data into account should lead to a better local estimate than that which would have been obtained when it is ignored. In practice however, the results obtained are sometimes disappointing. This paper tries to explain why this is so from the behavior of the lognormal kriging estimator. The estimator is shown to respect certain unbiasedness properties when considering the whole working field using the regression curve and its confidence interval for both simple or ordinary kriging. When examined locally, however, the estimator presents a behavior that is neither expected nor intuitive. These results lead to the question: is the theoretically correct lognormal kriging estimator suited to the practical problem of local estimation?