Usability study of digital libraries: ACM, IEEE-CS, NCSTRL, NDLTD

If digital libraries are to be used effectively, their user interfaces should be tested and enhanced. We observed 48 participants as they worked with the following digital libraries: ACM, IEEE-CS, NCSTRL, and NDLTD. We discuss how the features of these digital libraries influence the subjects’ efforts to perform search and retrieval tasks. Data analysis indicates that the IEEE-CS digital library was rated the best overall and NDLTD had the best search time. We present user recommendations and propose a taxonomy of features that we believe are essential for the design of future digital libraries. Noteworthy is the observation that users’ judgements on the importance of different features varied widely between the beginning and end of their test sessions. Received: 15 December 1997 / Revised: June 1999     

Osteopathy in Complex Lymphatic Anomalies

Complex Lymphatic Anomalies (CLA) are lymphatic malformations with idiopathic bone and soft tissue involvement. The extent of the abnormal lymphatic presentation and boney invasion varies between subtypes of CLA. The etiology of these diseases has proven to be extremely elusive due to their rarity and irregular progression. In this review, we compiled literature on each of the four primary CLA subtypes and discuss their clinical presentation, lymphatic invasion, osseous profile, and regulatory pathways associated with abnormal bone loss caused by the lymphatic invasion. We highlight key proliferation and differentiation pathways shared between lymphatics and bone and how these systems may interact with each other to stimulate lymphangiogenesis and cause bone loss.     

The creep of hydrated cement paste

Length and weight changes were measured for six series of mortar specimens subjected to various compressive stress histories during desorption and sorption cycles.It was found that complete drying of specimens subjected to compressive stress induces a deformation in excess of that obtainable by shrinkage alone. Appreciable creep occurs with the macropore water frozen at ?18°C. For originally saturated specimens no significant difference in water content due to creep could be detected. Prior removal of the macropore water revealed that the rate of loss of water on drying is reduced by compressive stress due to closure of micropore spaces. For previously dried specimens expansion against load required 1.25 times the weight of water compared with unloaded specimens for the initial sorption region.     

Freeze-fracture of lipids and model membrane systems

Model membrane systems are used extensively in all aspects of membrane research, and freeze-fracture is the preeminent procedure for directly visualizing local structure in these lipid dispersions. Here we describe in detail the formation of liposomes and how freeze-fracture is routinely employed as a complementary technique to biophysical and biochemical procedures in the characterization of multilamellar vesicles (most commonly known as liposomes) and unilamellar vesicles. Many preparative procedures exist for the formation of multi- and unilamellar vesicles. Examples of each system are given and their properties as well as freeze-fracture morphology are discussed. The detection of lipid-phase transitions is considered, in particular, with emphasis on the application of freeze-fracture to the study of lipid polymorphism. We briefly discuss the fracturing of apolar lipids which do not adopt bilayer structures but which can be stabilized into microemulsions by a phospholipid monolayer. Finally, a critical assessment is made of filipin as a morphological marker for cholesterol domains in the plane of the bilayer.     

Methodologies for hazard analysis and risk assessment in the petroleum refining and storage industry — Part II

The report briefly describes the consecutive steps in the identification, assessment and comparison of hazards and associated risk. These techniques can be helpful in setting the priorities for the decision on measures to reduce risk. When quantifying risk for the comparison of alternative cases, the use of a consistent data base is stressed. It is pointed out that the risk assessment techniques described in the report, although potentially valuable tools for improving overall safety performance, have short-comings particularly in dealing with human factors. A glossary is appended to define terms as they are used in this report and a list of recommended further reading is included. Part I appeared inFire Technology, August 1984. Prepared by the Ad-Hoc Risk Assessment Group of the Oil Companies' International Study Group for Conservation of Clean Air and Water in Europe (CONCAWE) Reference: CONCAWE's Ad-Hoc Risk Assessment Group; “Methodologies for Hazard Analysis and Risk Assessment in the Petroleum Refining and Storage Industry, Part II,” Fire Technology, Vol. 20, No. 4, November 1984, p. 43     

Wavelength and temperature dependences of the absorption and scattering cross sections of soot

We have inferred the wavelength and temperature dependence of the absorption and scattering cross sections of mature soot in an ethylene flame from laser-induced incandescence (LII) and transmittance measurements at 532 and 1064 nm. The LII measurements indicate that the emissivity of soot in a flame deviates from the expected 1/λ dependence. Combining the LII results with transmittance measurements yields single-scattering albedos of 0.058-0.077 at 1064 nm and 0.22-0.29 at 532 nm and values of F(m)/E(m) of 2.2-2.9 at 532 nm and 2.4-3.3 at 1064 nm. These values confirm that scattering must be taken into account when interpreting extinction data at these wavelengths. Our results also indicate increases in the absorption cross section and decreases in the scattering cross section with increasing fluence at low fluences. The increase in absorption cross section is consistent with increases in primary particle size with increasing particle temperature during laser heating. The decrease in scattering cross section could be attributable to an increase in the radius of gyration or a decrease in the fractal dimension of the aggregate with increasing temperature. Alternatively these trends might be the result of changes to the optical properties of the particles with increasing temperature.     

High Speed Digital Directional Comparison Relaying

ABSTRACT

A high speed directional comparison relay based on the evaluation of the locally measured deviations of the voltage and current from their prefault values is described in this paper. Signal processing techniques are used to damp out the exponentially decaying dc component and high frequency transient components so that the operation of the relay depends on the power frequency components of the voltage and current deviation signals. The direction to a fault is determined by detecting the first transgression of the fault trajectories across threshold boundaries in the deviation plane. Studies on a three phase power system model show that the direction to a fault is determined within a first few milliseconds following the inception of a fault.