Showing papers by "University of Rhode Island published in 1983"

Product design for manufacture and assembly

Abstract: Design is the first step in manufacturing, and it is where most of the important decisions are made that affect the final cost of a product. Since 1980, analysis techniques have been made available which can guide designers towards products which are easy to manufacture and assemble. The availability of these techniques has created a revolution in manufacturing industry, especially in the USA, leading to reduced product cost, better quality, shorter time to market, lower inventory, few suppliers, and many other improvements. The paper first stresses the importance of taking careful account of manufacturing and assembly problems in the early stages of product design. Then, using a case study, the philosophy of the Design for Manufacture and Assembly (DFMA) methodology and its application are explained. The historical development of dessgn-for-assembly and design-for- techniques in Japan, Europe and the USA is presented. A review of published case histories emphasizes the enormous advantages to be gained by adopting this relatively new approach as the major tool in concurrent and simultaneous engineering. Finally, a discussion of the various roadblocks affecting DFMA implementation is followed by a discussion of current developments, which include product design for disassembly, service and recycling.

Estimating the Angles of Arrival of Multiple Plane Waves

Abstract: The problem of estimating the angles of arrival of M plane waves incident simultaneously on a line array with L + 1 (L?M) sensors utilizing the special eigenstructure of the covariance matrix C of the signal plus noise at the output of the array is addressed. A polynomial D(z) with special properties is constructed from the eigenvectors of C, the zeros of which give estimates of the angle of arrival. Although the procedure turns out to be essentially the same as that developed by Reddi, the development presented here provides insight into the estimation problem.

Rare earth elements in seawater near hydrothermal vents

Abstract: Rare earth element (REE) patterns in the deep Pacific are strongly depleted in the lighter elements and have a large negative cerium anomaly. These REE patterns and associated concentration–depth profiles are maintained by regeneration in deep waters modified by preferential scavenging of the lighter elements. Scavenging by iron- and manganese-rich hydrothermal plumes might explain why vast areas of sediments far removed from spreading centres contain a metalliferous component.

Food limitation of production by adult Acartia tonsa in Narragansett Bay, Rhode Island1

Abstract: Egg production, dry weight, cephalothorax length, and condition factor were measured for adult Acartia tonsa females collected twice weekly from Narragansett Bay, R.I., during summer 1979 and incubated in ambient bay water and in ambient bay water enriched with laboratorycultured algae. Egg production, dry weight, and condition factor of copepods in the ambient bay water fluctuated considerably (ranges 1.6-51.6 eggsafemale-‘*d-l, 7.37-16.60 fig dry wt, and 1.09-2.37 condition factor) and closely followed the seasonal trends in Chl a and particulate carbon and nitrogen. Cephalothorax length remained fairly constant during the study. The overall mean egg production rate, dry weight, and cephalothorax length of the copepods after incubation for 48 h in the algae-enriched water were significantly greater than for copepods incubated in ambient bay water (mean values 45.9 vs. 25.3 eggsafemale-‘*d-l, 13.2 vs. 11.8 kg dry wt, and 901.7 vs. 891.8 pm long). Since body size and egg production in adult A. tonsa responded rapidly to a change in food availability, the copepods must have been continuously food limited in Narragansett Bay during summer.

Overlapping spreading centres: new accretion geometry on the East Pacific Rise

Abstract: In a detailed Seabeam investigation of the East Pacific Rise (EPR) from 8°N to 18°N, a new kind of volcano-tectonic geometry associated with fast-spreading centres has been discovered (Figs 1, 2). At several locations along the rise axis the neovolcanic zone is discontinuous, and is laterally offset a short distance (1–15 km). In contrast to a classic ridge–transform–ridge plate boundary, however, the offset ridge terminations overlap each other by a distance approximately equal to or greater than the offset. They curve sharply towards each other and often merge into one another along strike. Separating the overlapping spreading centres (OSCs) is a closed contour depression up to several hundred metres deep which is sub-parallel to the trend of the OSCs. The region between the OSCs is a complex zone of both shear and rotational deformation with no obvious transform parallel structures. Based on wax model studies of spreading centres, we suggest here that transform faults fail to develop at fast spreading centres where the lateral offsets are small (<15 km), because the lithosphere is too thin and weak to maintain a classic, rigid plate spreading centre–transform fault pattern. The OSC geometry is unstable and evolves rapidly. One of the two OSCs prevails while the other is abandoned. A significant area of sea floor created at fast spreading rates may bear the imprint of this newly observed process.

Relative value of carotenoids as precursors of vitamin A

Abstract: The carotenoid pigments are very conspicuous in nature, owing to their yellow to red hues, and occur without exception in photosynthetic tissue. They are responsible for the colour in some species of yeast, bacteria and fungi as well as many vegetables and fruits. Although animals are incapable of de nmo synthesis, they are able to deposit the carotenoid pigment as absorbed or with some alteration of the basic structure. Thus, the red to yellow colour in the flesh, skin, shell or exoskeleton of salmon, lobster, crab, prawn, carp, flamingo, etc. is directly or indirectly diet-related. The intestinal cleavage of carotenoids to form vitamin A active retinoids represents the main contribution of the carotenoids to nutrition. The colour associated with foods such as vegetables, fruits, butter, egg yolks, salmon, etc. represents an aesthetic contribution made by these pigments. An inspection of other papers in this symposium demonstrates that the retinoids have a wider application to health than has been traditionally thought. Likewise, recent findings support the suggestion for a wider, non-vitamin A -role of the carotenes. The structures of some common carotenoids are shown in Fig. I. p-Carotene, while not the most abundant carotene is, nevertheless, very widespread in nature. Both halves of p-carotene are related to retinol, thus the compound possesses maximal provitamin A activity. y-Carotene, with one ring, a-carotene with a 4',5' double bond in the ring, and P-cryptoxanthin (xanthophyll) and P-carotene-5,b epoxide, with substituted rings, contribute 50% of the activity of p-carotene.

Microbiological and Organic-Chemical Processes in the Surface and Mixed Layers

Abstract: The microorganisms, their organic matter and the gases they consume and release are vital components of the hydrosphere which impinge upon the atmosphere. This chapter considers the microbiological processes, and the organic-chemical transformations that occur, when microorganisms utilize one gas as a raw material while releasing another gas as a by-product during the synthesis and decay of organic matter. The cells and the by-products from the growth and metabolism of each trophic or feeding type of microorganism are in turn used by other trophic types to form an ecosystem, a community of organisms considered as a unit together with its physical environment. The microorganisms, their organic matter and the gases that regulate the metabolism within this ecosystem are transformed and balanced in a daily rhythm of production and consumption, controlled directly or indirectly by the solar cycle. They are also affected by physical processes which transfer gases, organic matter and microorganisms to and from the mixed layer and its boundaries at the sea-air interface and at the thermocline.

Experimental ecology of the temperate scleractinian coral Astrangia danae. II. Effect of temperature, light intensity and symbiosis with zooxanthellae on metabolic rate and calcification

Abstract: The combined effects of temperature, light and symbiont density on the metabolic rate and calcification of the temperate coral Astrangia danae were studied experimentally using colonies containing different concentrations of zooxanthellae. After acclimation to five temperatures between 6.5° and 27°C, and incubation at three light levels and in darkness, respiration and photosynthesis were measured and corrected for rates due to commensals alone. Calcification rates were regressed on zooxanthellae concentration and production in order to define “symbiotic” and “non-symbiotic” averages, and the enhancement of calcification by symbiotic interactions in the polyps. Respiration by the polyparium varied less with temperature between 11.5° and 23°C than that of the commensals, suggesting physiological acclimation by the coral tissue. In-vivo zooxanthellae photosynthesis increased linearly with temperature and was near its maximum at 400 μEin m−2 s−1, but the photosynthesis of the endolithic algae of the corallum varied little between 11.5° and 27°C. Calcification at any given temperature was near its maximum at 40 μEin m−2 s−1 in both symbiotic and non-symbiotic corals. CaCO3 deposition increased linearly with temperature in non-symbiotic colonies and in symbiotic colonies incubated in the dark. In symbiotic colonies, calcification in the light increased above these basic rates as temperature rose above 15°C. Below 15°C, symbiotic interactions failed to stimulate calcification, apparently due both to a lowering of zooxanthellae photosynthesis and to a decrease in the enhancing effect of any given level of primary production.

Bimodal grain size distribution and secondary thickening in air-fall ash layers

Abstract: Investigation of the ashfall deposit from the 1980 Mount St Helens eruption reveals that the deposit is bimodal, the finer population maintaining a uniform grain size distribution away from source, and that the deposit exhibits secondary thickening beyond the 1-cm isopach. Grain size distribution shows that at least 64% of the deposit is finer than 63 µm, far more than is generally supposed for plinian eruptions. An investigation of other ashfall deposits reveals similar grain size bimodality features, which are interpreted as evidence of aggregation of fine particles in the eruption cloud. Our data suggest that aggregation may be a common process during ash fallout from explosive eruptions and that secondary thickening may often occur, providing that other conditions are met.

The causes and consequences of sex-specific mortality in a freshwater copepod1

Abstract: We studied skewed adult copepod sex ratios in two ponds in an attempt to understand the ecological causes and evolutionary consequences of this life-history phenomenon. In ponds containing populations of zooplanktivorous sunfish, female copepods suffered higher mortality rates than males, while in ponds lacking these predators, male and female mortality rates were similar. Field and laboratory experiments showed that females, especially those carrying eggs, were more visible than males and that added visibility accounted for higher predation by fish on these individuals. We calculated the cost of carrying eggs in terms of the decreased population growth rate it produces, and then estimated the magnitude of egg mortality necessary to select for the egg-carrying strategy. Eggs not carried would have to suffer at .least 58% mortality for egg carrying to evolve in the presence of selective fish predation. The response of the copepods to these strong selective pressures lies in a third direction, the production of diapausing eggs.

Alternating linear-chain antiferromagnetism in copper nitrate Cu ( N O 3 ) 2 .2.5 H 2 O

Abstract: Current interest in the behavior of Heisenberg alternating antiferromagnetic quantum chains has been stimulated by the discovery of an unusual class of magnetoelastic spin-Peierls systems. Copper nitrate, Cu${(\mathrm{N}{\mathrm{O}}_{3})}_{2}$.2.5${\mathrm{H}}_{2}$O, does not display a spin-Peierls transition, but its dominant magnetic behavior is that of a strongly alternating antiferromagnetic chain with temperature-independent alternation. A remarkable, simultaneous fit is demonstrated between theoretical studies and a wide variety of zero- (low-) field experimental measurements, including susceptibility, magnetization, and specific heat. The fitting parameters are $\ensuremath{\alpha}(\mathrm{degree}\mathrm{of}\mathrm{alternation})=0.27$, $\frac{{J}_{1}}{k}=2.58$ K, ${g}_{b}=2.31$, and ${g}_{\ensuremath{\perp}}=2.11$. Slight systematic discrepancies are attributed to weak interchain coupling. Theoretical studies also predict a rich variety of behavior in high fields, particularly in the region involving the lower and upper critical fields, ${H}_{{c}_{1}}=28$ kOe and ${H}_{{c}_{2}}=44$ kOe. Experimental specific-heat measurements at $H=28.2 \mathrm{and} 35.7$ kOe show quantitative agreement with theory in this interesting parameter region. The fitting parameters are the same as for zero field and, again, small discrepancies between theory and experiment may be attributed to interchain coupling. The exceptional magnetic characterization of copper nitrate suggests its use for further experimental study in the vicinity of the high-field ordering region.

Prokaryotic infection associated with a mass mortality of the sea scallop, Placopecten magellanicus

Abstract: . A mass mortality of the deep sea scallop, Placopecten magellanicus, which occurred in the autumn and winter of 1979–80, in Narragansett Bay, Rhode Island was studied. Grossly the animals possessed greyish, flaccid adductor muscles and histologically they showed myodegeneration. Eighty-eight per cent of the 34 animals examined were infected with intracellular prokaryotes on the gills, plicate membranes and other epithelial surfaces of the body. The morphology of this prokaryotic organism is suggestive of rickettsia. Heavy infection was positively correlated with extensive myodegeneration.

Inequality, Opportunity, and Crime Rates in Central Cities

Abstract: * * * In a recent paper, Cohen and Felson argue that changes in our routine activities since World War 11 have contributed to the increase in predatory crime by creating additional opportunities for it. In particular, they found that a measure of the dispersal of activities away from the home-the household activity ratio-has had a significant effect on crime rate trends since 1947. The aim of the present research is twofold: (1) to determine if this relationship occurs across space as well as over time, and (2) to see i f economic inequality may be an intervening variable between the household activity ratio and the crime rate. The sample consists of 93 nonsouthern cities of over 50,000 population in 1960. Data are drawn from the 1970 Census und the U n i f m Crime Reports. Using path analysis, it is determined that the effects of the household activity ratio cm rates of predatory crime are entirely indirect, and are transmitted by income inequality.

Survival of natural sewage populations of enteric bacteria in diffusion and batch chambers in the marine environment.

Abstract: The survival of natural populations of Escherichia coli and enterococci in sewage was measured in large-volume diffusion chambers in an estuary and a salt marsh. The 5-liter chambers, with polycarbonate membrane sidewalls, were found to be suitable for up to week-long experiments. Decay rates, measured monthly from February to August 1978, ranged from 0.042 to 0.088 h −1 (time for 90% of the population to die = 25 to 55 h) for E. coli and 0.019 to 0.083 h −1 (time for 90% of the population to die = 29 to 122 h) for enterococci and were significantly correlated with temperature. In contrast to the diffusion culture experiments, the decay of E. coli in batch culture did not correlate with temperature. Enterococci survived longer than E. coli in the Narragansett Bay (estuary) experiments, but survived less well in the more eutrophic salt marsh. The effect of light on survival was examined with light/dark experiments and sampling at frequent intervals over the diel cycle. Diel changes in survival were not evident in the Narragansett Bay experiments. E. coli , however, exhibited a diel pattern of growth during the day and death at night in the salt marsh. There was no significant difference in decay rates between light and dark diffusion chambers, nor were decay rates correlated with light intensity. In concurrent batch experiments, survival was significantly greater in the dark for both organisms. These results suggest that the effect of light is complex and that conditions in batch culture may modify the survival of enteric bacteria. Observations made in diffusion chambers may more closely follow the in situ survival of enteric microorganisms. Images

The Practical Application of Surface Electrical Resistivity to Detection of Ground-Water Pollution

Abstract: One of the primary problems in field investigations of ground-water pollution is locating the contaminant plume. Drilling of sampling holes on a hit-or-miss basis is both time-consuming and expensive. Under many subsurface conditions, surface electrical resistivity profiling can quickly and cheaply locate the general position of the plume and identify areas most feasible for sampling and monitoring. Many contaminants contain an ionic concentration considerably higher than the background level of native ground water. When such a contaminant is introduced into an aquifer, the electrical resistivity of the saturated soil is reduced. Surface electrical resistivity profiling across a suspected area can identify this reduced resistivity zone as an anomaly. The sensitivity of the method depends on relative uniformity of geology and topography as well as minimal extraneous electrical interferences. It is also essential that the “A” spacing used in the profiling procedure be carefully selected. If the resistivity contrast between contaminated and uncontaminated ground water is high, detection of at least the central part of the plume is likely within expected geologic variation. The method has been successfully used in the location of plumes from contaminants including brine, uranium reprocessing liquid wastes and landfill leachate in glacial deposits of New England.

The effects of dinoflagellate bioluminescence on the swimming behavior of a marine copepod1

Abstract: The horizontal swimming patterns of groups of Acartia hudsonica were tracked and described using a video-computer system. The patterns were compared in the presence of clones of bioluminescent and nonbioluminescent Protogonyaulax tamarensis. Bioluminescent dinoflagellates increased the number of high-speed swimming bursts by the copepods and thus decreased the amount of slow-speed swimming characteristic of their grazing behavior. With bioluminescent dinoflagellates, swimming paths were less circuitous and swimming speeds higher. This behavior may tend to move copepods away from bioluminescent dinoflagellates in nature. Both changes in swimming behavior should result in reduced grazing by the copepods on bioluminescent dinoflagellates.

Neodymium isotopic evidence for Galapagos hotspot—spreading centre system evolution

Abstract: Nd and Sr isotope variations along the Galapagos spreading centre support Morgan's preferential subcrustal flow channel connecting the Galapagos mantle plume with the northeastward migrating ridge axis. Decoupling of La/Sm and Nd isotope variations near 91° W further suggests that basalts are derived from smaller degrees of melting and are deeper beneath this elevated part of the ridge.

On the statistics of the estimated reflection coefficients of an autoregressive process

Abstract: The exact statistics of the estimated reflection coefficients for an autoregressive process are difficult to determine. However, since almost all the common methods for estimating the reflection coefficients are maximum likelihood estimates for large data records, the asymptotic distribution of the estimates is multivariate Gaussian with a covariance matrix given by the Cramer-Rao bound. A recursive means of computing the covariance matrix bound is described. Simulation results show that the asymptotic expressions are accurate for large data records. However, for relatively short data records, the asymptotic expressions are accurate only for spectra with a small dynamic range.

Effects of copper and cadmium on growth, swimming and predator avoidance in Eurytemora affinis (Copepoda)

Abstract: In this study we demonstrate the sensitivity of swimming behavior and predator-escape responses of nauplii of the estuarine copepod Eurytemora affinis to sublethal doses of Cu and Cd. Behavior was generally altered at metal doses below those affecting growth rates or survival of the copepods. Swimming velocities of Cu-dosed nauplii were different from controls at all concentrations of Cu tested (10–50 μg l-1 total Cu) after 24- to 48-h exposure, whereas development rate of nauplii was significantly reduced only after 96 h at 25 μg l-1. The 96 h LC50 for Cu was approximately 30 μg l-1 Cu. Naupliar swimming velocity was also affected by Cd. Swimming speeds were reduced after 24 h at 130 μg l-1, and development was slowed after 48 h at 116 μg Cd l-1. The 96-h LC50 was >120 μg l-1. Little is known of the adaptive role of specific motile behaviors in the success of larval copepods. We investigated the relationship of swimming speed to predator — prey interactions of the nauplii using both real and simulated predators. Nauplii exposed to Cu for 24 h were observed to be generally hyperactive, a condition which could increase their encounter frequency with predators. Reduced numbers of escape responses of nauplii to a simulated predator, another indication of increased vulnerability to predation, were observed only after 48-h exposure to Cu. Nevertheless, feeding rates of non-dosed larval striped bass on dosed nauplii (24 h at 25 μg Cu l-1) were significantly higher than on control nauplii. Feeding rates of larval mysid shrimp, however, were not higher on similarly dosed nauplii; 24 h exposure of nauplii to >30 μg Cu l-1 did result in increased predation by mysids.

Recursive maximum likelihood estimation of autoregressive processes

Abstract: A new method of autoregressive parameter estimation is presented. The technique is a closer approximation to the true maximum likelihood estimator than that obtained using linear prediction techniques. The advantage of the new algorithm is mainly for short data records and/or sharply peaked spectra. Simulation results indicate that the parameter bias as well as the variance is reduced over the Yule-Walker and the forward-backward approaches of linear prediction. Also, spectral estimates exhibit more resolution and less spurious peaks. A stable all-pole filter estimate is guaranteed. The algorithm operates in a recursive model order fashion, which allows one to successively fit higher order models to the data.