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The objective of the research was to determine the effect of different tillage methods on some soil physicochemical properties in Niger Delta University Teaching and Research Farms. The land was divided into plots measuring 5 x 5 m with three replicates per treatment. Five tillage treatments considered were: No Till, hoeing, digging, hoeing + digging once, and hoeing + digging twice. Two samples were collected per plot at 0-15 cm and 15-30 cm depth. A total number of thirty (30) samples were collected from the field. The research was laid out using the Randomized Complete Block Design. Results showed that the tillage methods had no significant effect on the soil's chemical properties but influenced the physical. Mean pH across all plots ranged from 4.42 - 4.49 indicating strongly acidic state, electrical conductivity ranged 65.67-82 dS m-1 indicating no salinity stress, detrimental to crops; organic carbon and organic matter were moderate with a range of 18.52-21.55 g kg-1 and 37.03-43.10 g kg-1 respectively. Total nitrogen was at its moderate range of 7.88-12.17 g kg-1. Exchangeable acidity was low with a range of 1.52-1.71 cmol kg-1. The tillage methods influenced soil bulk density and porosity; the highest bulk density was recorded in the NT zone (1.18 g cm-3) which decreased steadily with an increase in tillage intensity. With the hoe+digging (twice) recording the lowest value of 0.94 g cm-3. Similarly, the highest porosity value was found in the tillage method with the lowest bulk density value (0.94 g cm-3: 64.7%), while the lowest was observed in the tillage method with the highest bulk density value (1.18 g cm-3: 55.7%). pH had positive correlation (P<0.05) with electrical conductivity (r=0.62), organic carbon (r=0.94), organic matter (r=0.90), and negative correlation with exchangeable acidity (r=-0.52). Organic carbon had strong positive correlation with organic matter (r=0.99), effective cation exchange capacity (r=0.69), clay (r=0.50), and total nitrogen (r=0.61). Silt (r=0.74) and clay (r=0.70) showed positive relationship with bulk density, while bulk density (r= -0.99) showed strong negative correlation with porosity. It is therefore recommended that crude tillage methods be used for sustainable and conservative agriculture. [ABSTRACT FROM AUTHOR]

Although phasor measurement units (PMUs) have become increasingly widespread throughout power networks, the buses monitored by PMUs still constitute a very small percentage of the total number of system buses. Our research explores methods to derive useful information from PMU data in spite of this limited coverage. In particular, we have developed an algorithm which uses known system topology information, together with PMU phasor angle measurements, to detect system line outages. In addition to determining the outaged line, the algorithm also provides an estimate of the pre-outage flow on the outaged line. To demonstrate the effectiveness of our approach, the algorithm is demonstrated using simulated and real PMU data from two systems--a 37-bus study case and the TVA control area. Index Terms--Event detection, line outages, phasor measurement units.

A key need facing the electric power industry is the ongoing requirement to develop its future workforce. While university education is a crucial step in this process, studies have shown that many promising students are unaware of possible careers in the power industry. Many also lose interest in math and science during their high school and even middle school years. This paper presents lesson plans and associated applets designed to help address these needs, developed as a collaboration between electric power researchers and education specialists. Thus far, two units have been developed to engage pre-university students in the power area. The first unit, Power and Energy in the Home, serves as an introduction to the concepts of power and energy and provides many sample loads to illustrate the impacts of running different appliances. Special attention is paid to environmental issues by the inclusion of Energy Star appliances along with incandescent and compact fluorescent lighting. The second unit, titled The Power Grid, aims to inform students about the macroscopic picture of how energy gets from generators to loads. Many different generation technologies are included, along with external system connections to demonstrate how power is imported and exported. Discussion of line overloading, and how networks can be both beneficial and detrimental depending on circumstances, are facilitated by features built into the applet and provided in the lesson plans. The materials have been distributed to students and educators, many of whom have provided valuable feedback. Index Terms--Educational technology, energy conservation, energy resources, load flow analysis, power engineering education, power systems.

Studies of the optimal multiplier (or optimal step size) modification to the standard Newton-Raphson (NR) load flow have mainly focused on highly stressed and unsolvable systems. This paper extends these previous studies by comparing performance of the NR load flow with and without optimal multipliers for a variety of unstressed, stressed, and unsolvable systems. Also, the impact of coordinate system choice in representing the voltage phasor at each bus is considered. In total, four solution methods are compared: the NR algorithm with and without optimal multipliers using polar and rectangular coordinates. This comparison is carried out by combining analysis of the optimal multiplier technique with empirical results for two-bus, 118-bus, and 10 274-bus test cases. These results indicate that the polar NR load flow with optimal multipliers is the best method of solution for both solvable and unsolvable cases. Index Terms--Load flow analysis, load flow convergence, optimal multipliers, polar and rectangular coordinates, step-size optimization.

An identification algorithm is proposed for generator outages in external systems given tie-line flow measurements and pre-outage linear sensitivity factors. The problem is challenging due to limited information available to operators in interconnected systems. To overcome the underdetermined nature of the problem (the number of tie-line measurements is smaller than the number of generators), a clustering method based on pivoted QR decomposition is implemented so that the outage location can be identified to the area of origination. Two test systems, the 68-bus New England system and the 500-bus synthetic system, were used for validation. The results demonstrate that with limited knowledge of the external system, the algorithm is able to identify the correct generator cluster in all cases. Another advantage of the proposed algorithm is its high efficiency, which enables detection within sub-milliseconds. In addition, an estimation of the cluster injection change is also provided by the algorithm. [ABSTRACT FROM AUTHOR]

Numme Feete: Meter in Early Modern England Joseph Tate University of Washington jtate@washington.edu Tate, Joseph. 'Numme Feete: Meter in Early Modern England', Early Modern Literary Studies 7.1/Special Issue 8 (May, [...]

Brian Vickers. English Renaissance Literary Criticism. Oxford: Oxford UP, 1999. 672pp. ISBN 0 19 818679 7 Joseph Tate University of Washington jtate@u.washington.edu Tate, Joseph. 'Review of Brian Vickers, English Renaissance [...]

This paper proposes and evaluates a systematic method for controlling an energy storage system for preventing load shedding due to transient declines in frequency. The proposed controller works on local measurements and uses an extended Kalman filter to perform online identification of system parameters. These results are then used to implement a model predictive controller for the safe withdrawal of support and energy recovery, both without incurring transient load shedding. The formulation accounts for single generator outages and includes power system parameters such as inertia, damping, and droop. The proposed method is evaluated using the nonlinear simulations of 6-bus and 24-bus test systems known as Roy Billinton Test System (RBTS) and IEEE Reliability Test System. The results show that the proposed controller is effective in preventing transient load shedding. [ABSTRACT FROM PUBLISHER]

The kinetics of the addition of phenol to diisopropylcarbodiimide, and reaction of the resulting N, N′-diisopropyl- O-phenylisourea with hydroxide, are reported. The isourea is generated by a slow overall termolecular equilibrium process, inhibited by isourea-phenol salt generation. In contrast to an earlier report, reaction of the isourea with hydroxide does not induce a synthetically useful 1,3-O-N (Chapman) rearrangement. Instead, deprotonation results in solvolysis by carbodiimide elimination. [ABSTRACT FROM AUTHOR]

Phasor measurement units (PMUs) are being increasingly deployed to improve monitoring and control of the power grid due to their improved data synchronization and reporting rates in comparison with legacy metering devices. However, one drawback of their higher data rates is the associated increase in bandwidth (for transmission) and storage requirements (for data archives). Fortunately, typical grid behavior can lead to significant compression opportunities for phasor angle measurements. For example, operation of the grid at near-nominal frequency results in small changes in phase angles between frames, and the similarity in frequencies throughout the system results in a high level of correlation between phasor angles of different PMUs. This paper presents several methods for preprocessing of phasor angles that take advantage of these system characteristics, including a new method—frequency compensated difference encoding—that is able to significantly reduce angle data entropy. After the preprocessor stage, the signal is input to an entropy encoder, based on Golomb–Rice codes, that is ideal for high-throughput signal compression. The ability of the proposed methods to compress phase angles is demonstrated using a large corpus of data—over 1 billion phasor angles from 25 data sets—captured during typical and atypical grid conditions. [ABSTRACT FROM PUBLISHER]