One MWth bench model cavity receiver steam generator

Design of a bench model steam generator having geometric and thermal characteristics of the full-scale steam generator to be used in energy collection-conversion modules of a 100 MW_e solar energy conversion power plant scaled for operation in the Centre National de la Recherche Scientifique (CNRS) solar furnace at Odeillo, France, was a major element of the Solar Power System and Component Research Program.^‡

The planned follow-on program to fabricate the bench model steam generator, to provide required instrumentation-control-adaptation equipment and to perform checkout testing is being performed during 1975.     

Olfactory basis of cannibalism in grasshoppers (Orthoptera: Acrididae): III. Use of attractants on carbaryl wheat bran bait

Two known necrogenic attractants, linoleic acid (18:2) and linolenic acid (18:3), were added to carbaryl bran bait to enhance control of rangeland grasshoppers in southeastern Wyoming. The primary goal was to increase control of species of Gomphocerinae, which normally do not consume bran bait. Each attractant was applied at 1, 5, and 10 grasshopper equivalents (GE) (e.g., a 1-GE treatment had the amount of fatty acid per unit weight of wheat bran that would be found in one grasshopper). Controls included carbaryl bran with no attractant and no treatment. Bran was applied at a rate of 1 kg/ha to 1-ha blocks on June 6, 1992, with four replicates per treatment and control. Plots were sampled for grasshoppers and nontarget organisms one day prior to and one, two, and three days after treatment. The addition of linoleic acid (10 GE) resulted in significantly lower total grasshopper densities than carbaryl bran alone. None of the attractants significantly improved control of all Gomphocerinae due to inconsistent effects among species. Relative to carbaryl bait alone, all doses of both fatty acids significantly improved control ofAmphitornus coloradus (Thomas). However, the attractants did not change the level of control ofCordillacris occipitalis orAulocara elliotti, and linolenic acid (5 GE) and linoleic acid (1 GE) resulted in significantly poorer control ofAgeneotettix deorum (Scudder) than carbaryl bait alone. Nontarget arthropods were largely unaffected by the attractants, except for the spiders, which were significantly reduced in all linolenic acid treatments.     

Olfactory basis of cannibalism in grasshoppers (Orthoptera: Acrididae): II. field assessment of attractants

The responses of rangeland grasshoppers to biologically and historically derived attractants were studied in a shortgrass prairie in southeastern Wyoming in July 1990. Seven long-chain fatty acids (C₁₄–C₂₀: singly and in combination), grasshopper cadavers, molasses, fruit extracts, and chloroform (solvent control) were tested. Each attractant was applied to filter paper and placed in an arena delimited by a 0.10-m² aluminum ring. Grasshoppers were most attracted to linoleic and linolenic acids, with significantly more grasshoppers found in these arenas than in those of the controls or other attractants. These two fatty acids alone and in combination were more attractive at 1 grasshopper equivalent (GE) than at 5 GE. The seed bug,Lygaeus kalmii Stål, and five species of ants were also attracted to these two fatty acids. Molasses had significantly more grasshoppers on the filter paper than did the other attractants, but molasses had significantly fewer grasshoppers in the arena than the fatty acids. Fruit extracts were not effective at attracting grasshoppers. Water extracts of cadavers attracted significantly more grasshoppers to the bait than did chloroform extracts. Because the assayed grasshopper community was dominated by the Gomphocerinae (a subfamily that includes many pest species that do not readily consume wheat bran bait), it may be possible to use fatty acids in conjunction with insecticidal bran baits for increased control of rangeland grasshoppers.     

Low-roundoff-noise limit-cycle-free implementation of recursivetransfer functions on a fixed-point digital signal processor

A method is presented for realizing recursive digital transfer functions on a fixed-point digital signal processor. The method is based on the parallel connection of L∞-norm scaled first- and second-order state-space structures. Magnitude truncation of the state update equations is employed to render the realization free of both overflow oscillations and constant-input limit cycles. The roundoff noise and coefficient sensitivity of the realization are also near minimum, giving a realization with outstanding performance in terms of all finite wordlength effects. An implementation on the DSP56000 family of digital signal processors demonstrates that the realization is efficient enough to achieve high sample rates     

Implementation of microprogrammed control in FPGAs

The microprogrammed approach to implementing control state machines has been widely used since the early 1960s and has the advantages of structured programming and fixed timing characteristics. This paper presents a microprogrammed control unit that has been tailored to implementation in field-programmable gate arrays (FPGAs). The microsequencer has a novel architecture which takes advantage of the enhancements existing in coarse-grained FPGAs to implement efficiently four basic functions: registers, multiplexers, adders, and counters. The sequencer supports both nested subroutines and nested loops, and can operate in both pipelined and nonpipelined modes. The pipelined mode of operation uses delayed branching in which one additional microinstruction always executes following any instruction that changes program flow. It is found that in a typical medium-sized (50 K gates) FPGA, the sequencer can be clocked at over 60 MHz nonpipelined and over 100 MHz pipelined while using less than 5% of the available FPGA logic resources. This leaves the bulk of the FPGA resources available for implementing other digital circuitry that is to be controlled by the microsequencer. While not attractive for a small number of states, the microprogrammed approach has some significant advantages for complex controllers with a large number of states     

Olfactory basis of cannibalism in grasshoppers (Orthoptera: Acididae): I. laboratory assessment of attractants

Two laboratory-reared and five field-collected species of grass-hoppers were assayed for behavioral responses to volatile chemicals emitted from grasshopper cadavers using a two-choice olfactometer with no stimulus as a control. Necrophilic and necrophobic responses to the stimuli were dependent upon species, sex, development, starvation, crowding, and attractant. Laboratory-rearedMelanoplus differentialis (Thomas) and field-collectedHadrotettix trifasciatus (Say) andAulocara elliotti Thomas exhibited significant responses to the cadavers. Females of these three species showed significant movement towards the cadavers, but males were not significantly necrophilic. All tested developmental stages ofH. trifasciatus (fourth-instar nymphs through adults) showed significant attraction to cadavers. FedM. differentialis adults andH. trifasciatus adults and nymphs were significantly attracted to cadavers, but starved individuals were either repelled or exhibited no significant response. Although femaleA. elliotti from an uncrowded population were significantly attracted to cadavers, females from a crowded population were significantly repelled from cadavers. Contraspecific cadavers more frequently elicited a measurable response in adultM. sanguinipes andH. trifasciatus than did conspecific cadavers, and only contraspecific cadavers yielded a significant (necrophilic) response. AlthoughM. differentialis was necrophilic, neither males nor females were significantly attracted to water.     

A method for accelerating the design of optimal linear-phase FIRdigital filters

A simple method is presented for reducing the execution time of the McClellan-Parks-Rabiner (1973) FIR (finite impulse response) digital filter design program on computers with a floating-point processor. It is found that 80% to 90% of the execution time of this program involves only four lines of the program code. By efficiently implementing these four lines of code in assembly language it is possible to significantly reduce the execution time. Examples of this method are given for personal computers based on both 8086-family and 68000-family microprocessors with a corresponding math coprocessor. It is found that for these computers the method reduces execution time by a factor of 1.6 to 1.9