Self-Consistent Effects on the Starting Current of Gyrotron Oscillators

Self-consistent effects on the starting current of gyrotron oscillators are examined. Field profiles in the open cavity are shown to be sensitive to the interaction dynamics. This can either significantly raise or lower the oscillation threshold, particularly for the low-Q modes. The transition from resonant-mode oscillations at the low magnetic field to backward-wave oscillations at the high magnetic field is demonstrated.     

Analysis of optical coherence multiplexing networks for satellite communication

Free-space optical communication between satellites networked together can enable a high data rate between the satellites. Coherence multiplexing (CM) is an attractive technique for satellite networking due to its ability to cope with the asynchronous nature of communication traffic and the dynamic changes taking place in the satellite constellation. The use of optical radiation for intersatellite links creates very narrow beam divergence angles. Due to the narrow beam divergence angle, the vibration of the pointing system, the movement of the satellite, and the large distance between them the pointing from one satellite to another is a complicated task. The vibration of the pointing system is caused by two stochastic fundamental mechanisms: 1) tracking noises created by the electrooptic tracker and 2) vibrations created by internal satellite mechanical mechanisms and external environments. We derive mathematical models of signal, noise, the approximate signal-to-noise ratio, and the approximate bit-error rates of optical communication satellite networks as functions of the system's parameters, the number of satellites, and the vibration amplitude for frequency-shift keying coherence multiplexing (FSK-CM). Based on these models, we can calculate the negative impact of both the number of satellites and the optical terminal vibration on the system's performance.     

Effects of soil erosion on water quality and water uses in the upper Phong watershed.

The main objective of this paper is to simulate the effects of soil erosion on river water quality and on agricultural production as a result of the transformation of forestlands in the catchment of the upstream Phong River. Suspended solids carry down attached nutrients and agricultural chemicals causing water pollution in the downstream. There are four different types of land use in this simulation, namely forestlands, flatland and highland sugarcane plantation areas, and paddy fields. The highest mean annual amount of soil erosion is from paddy fields (585,700 tons/year), followed by highland (73,800 tons/year) and flatland (63,950 tons/year) sugarcane plantation areas and forestlands (41,800 tons/year), respectively. However, as most of paddy fields are located in a low land and are wet type cultivations, the soil erosion occurred has less impact on river water quality and its production compared to the soil erosion from the steeper slopes of highland plantation areas. Under the resource-based agriculture, the sugarcane production is mainly increased by expanding the plantation areas leading to a significant loss of topsoil and a considerable reduction of agricultural production. Soil erosion contributes to an increase in the average annual suspended solids concentration by 72 mg/l.     

Hydrogenated amorphous silicon thin-film transistor arrays fabricated by digital lithography

A jet-printed digital-lithographic method, in place of conventional photolithography, was used to fabricate 64 /spl times/ 64 pixel (300 /spl mu/m pitch) matrix addressing thin-film transistor (TFT) arrays. The average hydrogenated amorphous silicon TFT device within an array had a threshold voltage of /spl sim/3.5 V, carrier mobility of 0.7 cm/sup 2//V/spl middot/s, subthreshold slope of 0.76 V/decade, and an on/off ratio of 10/sup 8/.     

Accuracy of teacher judgments in predicting oral reading fluency.

The relationship between teachers' judgments versus actual performance on curriculum-based measures in reading was examined. A total of 30 regular education teachers were asked to predict the oral reading fluency score of students along with a rating scale of reading subskills. Correlations between teacher judgment measures and student performance found that teachers were accurate reporters of student performance levels in reading. However, some questions were raised whether teachers were accurate at predicting the actual level of student oral reading fluency when effect sizes were used to compare teacher judgment and actual student performance. Recommendations for continued research in understanding the parameters of the accuracy of teacher judgment are made. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A kinetic model for the acid-oxygen pressure leaching of Ni–Cu matte

A semi-empirical mathematical model for the acid-oxygen pressure leaching of Ni–Cu matte is presented, based on data from batch leaching experiments. The primary controlling factor in the leaching process is found to be galvanic inhibition of the more highly oxidized copper and nickel sulfide species by less oxidized species, particularly Ni alloy and Ni₃S₂. The leaching rate of many species is greatly reduced by the presence of one or both of these phases, and others will not commence leaching until neither is present. The mathematical model is based on first-order chemical reaction controlled rate expressions, as the reactions occurring are electrochemical in nature. Mass transfer effects are included only empirically. Some possibly diffusion-related phenomena are noted, although the model is not extended to incorporate these effects on a fundamental level. The model is verified and extended by the inclusion of several different factors that were tested experimentally. The effects of variations in O₂ flow rate and partial pressure, initial particle size, reaction pulp density and initial acid concentration were all studied, and included in the model. Variations in O₂ flow rate and partial pressure are found to affect the reaction rates via the dissolved oxygen concentration in the solution phase.     

A scale model for fitting object shapes from fixed location data

In this paper we present a scale model for fitting an ideal shape to an object. The measurements of the object are taken corresponding to a fixed coordinate system at a set of well-defined locations on the surface of the object. We propose an algorithm to estimate the model parameters and hypothesis tests to make statistical inferences about several possible special cases of the general model. The model is tested with an example that analyzes data on the feet of people in Hong Kong.     

Thermodynamics of Chemical Interactions in the CdTe–ZnTe–O2–C System during Melt Growth of Cd1 – x Zn x Te Crystals

Thermodynamic analysis is used to identify the possible chemical reactions of CdTe and ZnTe with the container material and gaseous atmosphere during Bridgman growth. Thermodynamic parameters of carbide and oxycarbide formation in the growth system are evaluated. The calculation results are consistent with the well-known fact that oxygen-containing impurities can be removed from the growth charge by calcination in hydrogen. Moreover, as shown in experiment, the removal of oxygen from the charge ensures a substantial decrease in the carbon content of the crystals.     

Binary sequences with low aperiodic autocorrelation for synchronization purposes

An evolutionary algorithm is used to find three sets of binary sequences of length 49-100 suitable for the synchronization of digital communication systems. Optimization of the sets are done by taking into consideration the type of preamble used in data frames and the phase-lock mechanism of the communication system. The preamble is assumed to be either a pseudonoise (PN) sequence or a sequence of 1s. There may or may not be phase ambiguity in detection. With this categorization, the first set of binary sequences is optimized with respect to aperiodic autocorrelation which corresponds to the random (PN) preamble without phase ambiguity case. The second and third sets are optimized with respect to a modified aperiodic autocorrelation for different figures of merit corresponding to the predetermined preamble (sequence of 1s) with and without phase ambiguity cases.