The effect of grain size, strain rate, and temperature on the mechanical behavior of commercial purity aluminum

Commercial purity aluminum AA1050 was subjected to equal channel angular extrusion (ECAE) that resulted in an ultrafine-grained (UFG) microstructure with an as-received grain size of 0.35 μm. This UFG material was then annealed to obtain microstructures with grain sizes ranging from 0.47 to 20 μm. Specimens were compressed at quasi-static, intermediate, and dynamic strain rates at temperatures of 77 and 298 K. The mechanical properties were found to vary significantly with grain size, strain rate, and temperature. Yield stress was found to increase with decreasing grain size, decreasing temperature, and increasing strain rate. The work hardening rate was seen to increase with increasing grain size, decreasing temperature, and increasing strain rate. The influence of strain rate and temperature is most significant in the smallest grain size specimens. The rate of work hardening is also influenced by strain rate, temperature, and grain size with negative rates of work hardening observed at 298 K and quasi-static strain rates in the smallest grain sizes and increasing rates of work hardening with increasing loading rate and grain size. Work hardening behavior is correlated with the substructural evolution of these specimens.     

MULTIMEDIA NETWORKING A Leading-Edge Communication Technology

The realization of digital multimedia's full business potential requires networking. This article discusses the value-added benefits to the corporation of networked multimedia as well as the choice of architectures and technologies needed to deliver multimedia networking solutions.     

Elastic-Plastic Contact Damage in a Lead Lanthanum Zirconate Titanate

Spherical indenters were used to produce elastic-plastic contact damage in a lead lanthanum zirconate titanate (PLZT) under conditions of quasi-static and impact loading. The extent of radial cracking produced under both loading conditions showed good correlation with the response predicted by an earlier fracture mechanics analysis for quasi-static conditions. Calculated radial crack lengths corresponding to conditions of impact loading exhibited excellent agreement with experimentally measured values. The dynamic hardness of the PLZT was determined to be ∼ 1.5 times the quasi-static hardness. Differences in the radial crack lengths produced under the two loading conditions were attributed primarily to this difference in hardness response.     

Multifamily Housing Characteristics and Tenant Satisfaction

This paper examines the long-term impact of structural features and physical amenities on the residential satisfaction of renters in multifamily housing. A cumulative logit analysis of 7,206 rented multifamily units in the 2005 American Housing Survey indicates that features creating separated space (additional room, bathroom, garage/carport, or balcony/patio) were associated with significantly higher satisfaction, even when holding total unit area constant. Conversely, violation of space separation by noise intrusion through walls, floors, or ceilings created dramatically negative effects. Other amenities such as a fireplace, disposal, or dishwasher had no statistically significant impact. Tracking a cohort of 5,170 rented multifamily units from 1997 to 2005 revealed somewhat similar effects on the satisfaction trajectory of residents during this period. More bathrooms, bedrooms, and other rooms, as well as the presence of a balcony/patio were associated with satisfaction improvements. Analyzing cohort units undergoing modifications during the tracking period revealed that the addition of a bathroom or central air conditioning had the clearest impact on satisfaction, followed by the addition of a balcony/patio, other room, dishwasher, or garage/carport.     

Subcontinuations

Continuations have proven to be useful for implementing a variety of control structures, including exception handling facilities and breadth-first searching algorithms. However, traditional continuations are not useful in the presence of concurrency, because the notion of the rest of the computation represented by a continuation does not in general make sense. Traditional continuations can also be difficult to use in nonconcurrent settings, since their global nature is sometimes problematic. This article presents a new type of continuation, called asubcontinuation. Just as a traditional continuation represents the rest of a computation ¿from a given point in the computation, a subcontinuation represents the rest of asubcomputation ¿from a given point in the subcomputation. Subcontinuations may be used to control tree-structured concurrency by allowing nonlocal exits to arbitrary points in a process tree and allowing the capture of a subtree of a computation as a composable continuation for later use. In the absence of concurrency the localized control achievable with subcontinuations makes them more useful than traditional continuations.     

Inertia and Change in the Early Years: Employment Relations in Young, High Technology Firms

This paper considers processes of organizational imprintingin a sample of 100 young, high technology companies. It examinesthe effects of a pair of initial conditions: the founders' modelsof the employment relation and their business strategies. Ouranalyses indicate that these two features were well alignedwhen the firms were founded. However, the alignment has deterioratedover time, due to changes in the distribution of employmentmodels. In particular, the ‘star’ model and ‘commitment’model are less stable than the ‘engineering’ modeland the ‘factory’ model. Despite their instability,these two blueprints for the employment relation have strongeffects in shaping the early evolution of these firms. In particular,firms that embark with these models have significantly higherrates of replacing the founder chief executive with a non-founderas well as higher rates of completing an initial public stockoffering. Some implications of these findings for future studiesof imprinting and inertia in organizations are discussed.     

Accelerated aging of extruded dielectric power cables. I. Controland monitoring methodology

An improved accelerated cable life test is described. Through the use of programmable logic controllers (PLCs), very precise and consistent control of the accelerated aging process has been achieved. A computer has been utilized to make continuous real-time acquisition and storage of key operating parameters possible. This precise control and monitoring methodology has permitted the study of the synergistic effects of voltage and temperature on the accelerated aging of full-sized cables in the laboratory     

Electronic Sensing of Aromatic Volatiles for Quality Sorting of Blueberries

An electronic sniffer using semi-conductor gas sensors that nondestructively measured aromatic volatile gas emissions from fruit was developed to assess blueberry quality. The sniffer detected soft and damaged fruit in packaged containers at a 5% level of damage and distinguished four of five fruit ripeness classes: (1) mature-green and green-pink; (2) blue-pink; (3) blue; and (4) ripe fruit. Sniffer response increased as fruit ripened, as did total concentration of aromatic volatiles. Sniffer response correlated with berry firmness, pH, titratable acidity, and color, and detected differences among 10 cultivars, as did impact response analysis. The electronic sniffer is rapid, nondestructive and may be used to sort and quality check for presence of unripe or damaged fruit in closed packs of fresh berries.