3,584 research outputs found
An Examination of Multi-Tier Designs for Legacy Data Access
This work examines the application of Java and the Common Object Request Broker Architecture (CORBA) to support access to remote databases via the Internet. The research applies these software technologies to assist an Air Force distance learning provider in improving the capabilities of its World Wide Web-based correspondence system. An analysis of the distance learning provider\u27s operation revealed a strong dependency on a non-collocated legacy relational database. This dependency limits the distance learning provider\u27s future web-based capabilities. A recommendation to improve operation by data replication is proposed, and the implementation details are provided for two alternative test systems that support data replication between heterogeneous relational database management systems. The first test system incorporates a two-tier architecture design using Java, and the second system employs a three-tier architecture design using Java and CORBA. Data on replication times for the two-tier and three-tier designs are presented, revealing a greater performance consistency from the three-tier design over the two-tier design for varying client platforms and communications channels. Discussion of a small-scale proof-of-concept system based on the three-tier design is provided, along with a presentation of the potential for the technologies applied in this system to benefit Air Force web-based distance learning
The independent and combined effects of carbohydrate and caffeine ingestion on cycling performance
Purpose: The purpose of this study was to determine the independent and combined effects of carbohydrate and caffeine ingestion on performance and physiological parameters during high-intensity aerobic cycling (~60 minutes). Methods: Ten cyclists (28 ± 3 yr, 73.2 ± 1.9 kg) performed 20 minutes of steady-state cycling (60% Wmax) followed by a simulated 20-km time trial (TT) under the following four treatment conditions: placebo (PLA), carbohydrate (CHO), caffeine (CAF), and a combination of CHO and CAF (CHO-CAF). One hour prior to exercise subjects ingested a placebo/caffeine capsule. Beverages (250 ml) were consumed immediately prior to the 20-min steady-state, immediately prior to the 20-km TT, and at the 20-min mark during the time trial. Subjects completed the treatment trials in a semi-randomized, double-blind, placebo fashion and trials were separated by ≥ 5 days. Results: CHO-CAF improved 20-km TT performance by 3.4% (93 sec) compared to PLA (p ≤ 0.05), whereas no differences were detected among CHO, CAF, and PLA. Similarly, CHO-CAF improved mean power output by 5% during the 20-km TT compared to the PLA trial. RER was elevated under all treatment conditions compared to PLA. Further, blood glucose was elevated in CHO-CAF compared to PLA post steady-state and post TT. Treatment conditions did not differentially impact VE, VO2, pre-exercise MVC, post-exercise MVC, RPE, and blood lactate. Conclusions: CAF and CHO improve 20-km time trial performance when taken together but not when taken independently. This appears to be possibly facilitated by peripheral (MVC) and metabolic modifications (RER + blood glucose). Regardless of the mechanism, these data suggest that cyclists should ingest CHO and CAF together to improve high-intensity time trial performance, while in the fed state
Aerodynamic and acoustic effects of eliminating core swirl from a full scale 1.6 stage pressure ratio fan (QF-5A)
Fan QF-5A was a modification of fan QF-5 which had an additional core stator and adjusted support struts to turn the core exit flow from a 30 deg swirl to the axial direction. This modification was necessary to eliminate the impingement of the swirling core flow on the axial support pylon of the NASA-Lewis Quiet Fan Facility that caused aerodynamic, acoustic and structural problems with the original fan stage at fan speeds greater than 85 percent of design. The redesigned fan QF-5A did obtain the design bypass ratio with an increased core airflow suggesting that the flow problem was resolved. Acoustically, the redesigned stage showed a low frequency broadband noise reduction compared to the results for fan QF-5 at similar operating conditions
Experimental steady-state performance of a multitube, centrally finned, potassium condensing radiator
Steady state performance of multitube, centrally finned, potassium condensing radiato
Facing Uncertainty, Proceeding with Caution, Living with Joy: Women with Multiple Sclerosis and the Motherhood Decision
Multiple sclerosis is a degenerative neurological disorder, affecting approximately 250,000-350,000 persons in the United States. Women are diagnosed twice as frequently as men, with the majority of those diagnoses occurring during their childbearing (typically between the ages of 20 and 40) years. For women with multiple sclerosis, the decision to bear children is complicated by numerous factors. First, conventional cultural images of motherhood rarely acknowledge women with disability of any kind as fit mothers. For a disabled woman to pursue motherhood often means confronting predominant ideals and frequently having to justify her decision. Second, multiple sclerosis has proven to be an enduring mystery to medical researchers. Discovered over 130 years ago, no causative agent has been identified and current treatments can merely slow the progression of the disease. Because the disease is unpredictable and there is no way of knowing the rate of disease progression, women must evaluate their current level of disability at the time they consider pregnancy and try their best to envision what their future may hold. Other complications include difficulty in accessing healthcare providers that are well-trained in the management of pregnancy and multiple sclerosis, and the limited availability of social programs and services to support mothers with multiple sclerosis. Despite these considerable challenges, women with multiple sclerosis employ strategic, adaptive approaches to their disease. Pregnancy and parenting that enable them to effectively fulfill the role of mother
Gas physical conditions and kinematics of the giant outflow Ou4
Ou4 is a recently discovered bipolar outflow with a projected size of more
than one degree in the plane of the sky. It is apparently centred on the young
stellar cluster -whose most massive representative is the triple system HR8119-
inside the HII region Sh 2-129. The driving source, the nature, and the
distance of Ou4 are not known. Deep narrow-band imagery of the whole nebula at
arcsec resolution was obtained to study its morphology. Long-slit spectroscopy
of the tips of the bipolar lobes was secured to determine the gas ionization
mechanism, physical conditions, and line-of-sight velocities. An estimate of
the proper motions at the tip of the south lobe using archival images is
attempted. The existing multi-wavelength data for Sh 2-129 and HR 8119 are also
comprehensively reviewed. The morphology of Ou4, its emission-line spatial
distribution, line flux ratios, and the kinematic modelling adopting a
bow-shock parabolic geometry, illustrate the expansion of a shock-excited fast
collimated outflow. The radial velocities and reddening are consistent with
those of Sh 2-129 and HR 8119. The improved determination of the distance to
HR8119 (composed of two B0 V and one B0.5 V stars) and Sh 2-129 is 712 pc. We
identify in WISE images a 5 arcmin-radius (1 pc at the distance above) bubble
of emission at 22 micron emitted by hot (107 K) dust, located inside the
central part of Ou4 and corresponding to several [O III] features of Ou4. The
apparent position and the properties studied in this work are consistent with
the hypothesis that Ou4 is located inside the Sh 2-129 HII region, suggesting
that it was launched some 90 000 yrs ago by HR8119. The outflow total kinetic
energy is estimated to be ~4e47~ergs. However, the alternate possibility that
Ou4 is a bipolar planetary nebula, or the result of an eruptive event on a
massive AGB or post-AGB star not yet identified, cannot be ruled out.Comment: Accepted for publication in Astronomy and Astrophysics. Also
available at http://hal.archives-ouvertes.fr/hal-0102228
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