Effects of varying the threshold of alarm systems and workload on human performance

The purpose of this research was to investigate the effects of varying the threshold of alarm systems and workload on human response to alarm signals and performance on a complex task. A receiver operating characteristic (ROC) curve was selected to reflect the sensitivity of the alarm system. The threshold of the alarm system was manipulated by changing the value of beta along the ROC curve. A total of 84 students participated in experiment 1 and 48 students participated in experiment 2. Participants performed a compensatory-tracking, a resource management and a monitoring task. As expected, results showed that participants responded significantly faster to true alarm signals when they were using the system with the highest threshold under low-workload conditions. Results also indicated that changing the threshold of the alarm system had a significant effect on overall performance and this effect was greater under high-workload conditions. However, contrary to expectations, the highest level of performance was achieved by setting the threshold at a low level. Results from both experiments revealed that the advantage of faster alarm reaction time as a result of increasing the system's threshold was lost because of its increased probability of missed events.     

Electron diffraction analysis and techniques for studying polypeptides and other polymers

A review of electron diffraction studies of polypeptide structures is given together with a discussion of the methods for obtaining diffraction patterns without serious specimen damage by electrons. Electron diffraction studies of poly-β-benzyl-L-aspartate show that diffraction intensities can be used quantitatively to determine polypeptide structures and the advantages of these studies in observing high angle meridional reflections are shown up by the observation of a novel structure in the unheated left handed helical form of the polypeptide. A large catalogue of techniques for preparing orientated films of polypeptides suitable for electron diffraction investigations makes the technique a powerful one for studying these structures. Polypeptides are shown to be useful for studying electron beam damage in protein-like materials.     

The social climate of alcoholism treatment programs

The social climate of four residential alcoholism treatment programs was assessed with the Community-Oriented Programs Environment Scale (COPES). The programs differed in terms of their treatment orientations (aversion-conditioning, milieu therapy) and the sociodemographic characteristics of the patients admitted. Results showed that (1) COPES profiles distinguished between the four alcoholism programs in ways that were consistent with their respective treatment orientations; (2) the type of patient admitted to these programs did not systematically affect their treatment environment; and (3) changes occurring within an alcoholism program resulted in corresponding changes in relevant dimensions of the treatment environment. We also discuss the practical utility of the COPES for assessing alcoholism programs.     

Efficacy of oxibendazole against adult and larval nematodes of cattle

Calves which were artificially infected with Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum but which were also carrying natural infections of Nematodirus and Trichuris were treated with 15.0 mg of oxibendazole (methyl-5-n-propoxy-2-benzimidazole-carbamate)/kg of body weight at 3 days, 7 days, and 42 days after exposure to the infective trichostrongylid and strongylid larvae. Efficacies against adult populations of these genera treated on day 42, except Trichostrongylus, exceeded 98%. The chemical was highly effective against immature nematodes of the genera, except Oesophagostomum (0%). Data were not obtained on Trichostrongylus. The oxibendazole premix was palatable, and toxicosis due to the chemical was not seen in these calves.     

National Ignition Facility system alignment

The National Ignition Facility (NIF) is the world's largest optical instrument, comprising 192 37?cm square beams, each generating up to 9.6?kJ of 351?nm laser light in a 20?ns beam precisely tailored in time and spectrum. The Facility houses a massive (10?m diameter) target chamber within which the beams converge onto an ～1?cm size target for the purpose of creating the conditions needed for deuterium/tritium nuclear fusion in a laboratory setting. A formidable challenge was building NIF to the precise requirements for beam propagation, commissioning the beam lines, and engineering systems to reliably and safely align 192 beams within the confines of a multihour shot cycle. Designing the facility to minimize drift and vibration, placing the optical components in their design locations, commissioning beam alignment, and performing precise system alignment are the key alignment accomplishments over the decade of work described herein. The design and positioning phases placed more than 3000 large (2.5?m×2?m×1?m) line-replaceable optics assemblies to within ±1?mm of design requirement. The commissioning and alignment phases validated clear apertures (no clipping) for all beam lines, and demonstrated automated laser alignment within 10?min and alignment to target chamber center within 44?min. Pointing validation system shots to flat gold-plated x-ray emitting targets showed NIF met its design requirement of ±50?μm rms beam pointing to target chamber. Finally, this paper describes the major alignment challenges faced by the NIF Project from inception to present, and how these challenges were met and solved by the NIF design and commissioning teams.     

GaN single crystals grown on HVPE seeds in alkaline supercritical ammonia

Ammonothermal growth (synthesis in supercritical (sc) ammonia fluid) has the promise of producing large low defect gallium nitride crystals through the application of techniques similar to those used in hydrothermal growth. Retrograde solubility of GaN greater than 5% by weight using group I amides as mineralizers is demonstrated in high nickel content autoclaves at pressures of one to three kilobars and temperatures between 300 to 600°C. The above conditions were optimized to grow single-crystal GaN at rates up to 40 μm per day on one cm² seeds. Gallium nitride Hydride Vapor Phase Epitaxy (HVPE) seeds are placed in the higher temperature zone below the nutrient basket employing the same configurations used in reverse gradient hydrothermal growth of berlinite (AlPO₄). GaN single crystals grown by the ammonothermal technique were characterized by X-ray diffraction, photoluminescence, scanning electron microscopy (SEM), atomic force microscopy (AFM), and chemical etching. The nitrogen-terminated face tends to exhibita flatter surface morphology than the gallium-terminated face, which is made up of a series of hexagonal columns. Major impurities in the crystal include potassium from the mineralizer, metals from the autoclave, and oxygen. The nitrogen-terminated face incorporated a lower level of metallic impurities in comparison with the gallium-terminated face. Finally, several process phenomena such as ammonia decomposition, parasitic nucleation of GaN on the autoclave walls, impurity incorporation, and defect generation in single-crystal GaN layers grown on HVPE seeds are identified and their possible mechanisms are discussed.     

Fire Performance of Selected IT-Equipment

The results from a series of large scale tests are presented to establish the fire performance of a number of common pieces of IT equipment including: computer monitors, printers and CPUs. The monitors have been tested in a fully furnished scenario in the ISO 9705 room arranged in a typical bedroom setting and in a specially constructed 4 m × 5 m room arranged in a typical classroom setting. The other pieces of equipment have been tested directly under the furniture calorimeter. This paper presents HRR for the various tests and discusses the significance of the results in terms of fire safety. A discussion of available statistical and anecdotal information is presented in this context.     

Room temperature discharge characteristics of Li/NH4NO3−LiNO3-amide cells using silver salts as active cathode materials

The discharge characteristics of cells using lithium anodes in conjunction with nitrate-amide melt electrolytes and silver salt cathodes are presented. The use of insoluble or sparingly soluble silver salts as active cathode materials for ambient temperature galvanic cell cathodes can allow higher rate discharges than otherwise possible using melt reduction as the cathode reaction. The cathode materials studied were: Ag₂CrO₄, Ag₂MoO₄, Ag₂WO₄, Ag₂PO₄, Ag₂SO₄, AgIO₃, AgIO₄, AgF, AgCl, AgBr, AgI, Ag₄RbI₅ and Ag₂O. The reduction characteristics of silver ions added to natrate-amide melts are also presented.