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Malla R.B.,University of Connecticut | Gopal J.,CT Associates Inc. | Gopal J.,University of Connecticut | Ahn J.,Pusan National University | Ahn J.,University of Connecticut
Journal of Engineering Mechanics | Year: 2013

One of the most critical components in the oxygen-generation and water-processing assemblies for human habitation in space is the deionizing (DI) bed-a packed bed of ion-exchange resin beads-that purifies water. The DI bed shrinks during the course of its operation, and therefore, for the bed to work satisfactorily, it must be kept properly compressed. To understand the force-transferring mechanism along the bed, sets of experimental programs were developed and conducted on the individual particles and bed samples of a DI granular material, Amberlite IRN-78. The presence of water reduced the load-bearing capacity of the individual particles, because most of the wet (water submerged) particles tested failed under relatively small crushing force, whereas the dry particles withstood a much higher load. The particle crushing force was found to be closely represented by normal and Weibull distributions. The DI material bed has a relatively small internal friction angle (shear strength). The lateral pressure coefficient was found to be relatively high. The material exhibited time-dependent behavior, creep, and stress relaxation, possibly through particle deformation and rearrangement. The friction force between the DI medium and the wall of the housing cylinder was significant, and increased rapidly in a nonlinear fashion with increasing sample length. The effect of friction was more significant for more densely packed beds. The loading and unloading tests showed that the compacted material bed exhibited an anelastic type of hysteresis behavior. The uncompacted bed was seen to have nonlinear load-deformation behavior, with a rapid increase in displacement with load, whereas the compacted bed showed linear or near-linear, load-displacement behavior. © 2013 American Society of Civil Engineers. ASCE. Source


Swanson B.J.,CT Associates Inc. | Swanson B.J.,University of Connecticut | Malla R.B.,University of Connecticut | Shaw M.T.,University of Connecticut
Journal of Bridge Engineering | Year: 2013

Bridge expansion joint sealants are used to deter water and corrosive materials from leaking through the joint and damaging the bridge structure. However, problems with leakage from failing joint sealants have been observed. In response to this situation, a silicone foam sealant designed for small-movement bridge expansion joints was developed. The foam sealant proved to be easy to use and economical. In previously reported studies, various laboratory tests were conducted to evaluate the foam sealant's tensile strength, compressive strength, reaction to various temperatures, stress relaxation, creep behavior, and bonding capabilities to various substrate materials, such as steel, asphalt, concrete, and polymer concrete. In the current study, further laboratory tests were conducted on the sealant. These tests included ponding and freeze-thaw resistance. The subject study included the development and use of an application procedure to install the silicone foam sealant into bridge expansion joints. After being applied to expansion joints on four bridges in the Northeast (Connecticut, New Hampshire, Rhode Island, and New York), continuous monitoring of the temperature, precipitation, and physical condition of the sealant was conducted for over 1 year. Based on these tests, it can be concluded that the silicone foam sealant is as easy to install and as durable as conventional solid sealants. © 2013 American Society of Civil Engineers. Source


Leakeas C.L.,Air Force Institute of Technology | Bartell R.J.,Air Force Institute of Technology | Krizo M.J.,Air Force Institute of Technology | Fiorino S.T.,Air Force Institute of Technology | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Laser weapon systems comprise of tiled subapertures are rapidly emerging in the directed energy community. The Air Force Institute of Technology Center for Directed Energy (AFIT/CDE), under sponsorship of the HEL Joint Technology Office has developed performance models of such laser weapon system configurations consisting of tiled arrays of both slab and fiber subapertures. These performance models are based on results of detailed waveoptics analyses conducted using WaveTrain. Previous performance model versions developed in this effort represent system characteristics such as subaperture shape, aperture fill factor, subaperture intensity profile, subaperture placement in the primary aperture, subaperture mutual coherence (piston), subaperture differential jitter (tilt), and beam quality wave-front error associated with each subaperture. The current work is a prerequisite for the development of robust performance models for turbulence and thermal blooming effects for tiled systems. Emphasis is placed on low altitude tactical scenarios. The enhanced performance model developed will be added to AFIT/CDE's HELEEOS parametric one-on-one engagement level model via the Scaling for High Energy Laser and Relay Engagement (SHaRE) toolbox. © 2010 Copyright SPIE - The International Society for Optical Engineering.. Source


Viswanathan C.T.,CT Associates Inc.
Bioanalysis | Year: 2012

The concept of microsampling and particularly the dried blood spot methodology has been widely known to the scientific community for considerable time. Yet, there is no formal standard approach available to date for the pharmaceutical community to benefit from, in its regulatory interactions. This article discusses the various aspects of these issues and provides a framework within which a standard set of procedures can be adopted. © 2012 Future Science Ltd. Source


Albrecht M.,Augustine Biomedical and Design | Gauthier R.L.,Anesthesia Specialty Services | Belani K.,University of Minnesota | Litchy M.,CT Associates Inc. | Leaper D.,University of Cardiff
American Journal of Infection Control | Year: 2011

Background: Forced-air warming (FAW) is widely used to prevent hypothermia during surgical procedures. The airflow from these blowers is often vented near the operative site and should be free of contaminants to minimize the risk of surgical site infection. Popular FAW blowers contain a 0.2-μm rated intake filter to reduce these risks. However, there is little evidence that the efficiency of the intake filter is adequate to prevent airborne contamination emissions or protect the internal air path from microbial contamination buildup. Methods: Five new intake filters were obtained directly from the manufacturer (Bair Hugger 505, model 200708D; Arizant Healthcare, Eden Prairie, MN), and 5 model 200708C filters currently in hospital use were removed from FAW devices. The retention efficiency of these filters was assessed using a monodisperse sodium chloride aerosol. In the same hospitals, internal air path surface swabs and hose outlet particle counts were performed on 52 forced-air warming devices (all with the model 200708C filter) to assess internal microbial buildup and airborne contamination emissions. Results: Intake filter retention efficiency at 0.2 μm was 93.8% for the 200708C filter and 61.3% at for the 200708D filter. The 200708D filter obtained directly from the manufacturer has a thinner filtration media than the 200708C filter in current hospital use, suggesting that the observed differences in retention efficiency were due to design changes. Fifty-eight percent of the FAW blowers evaluated were internally generating and emitting airborne contaminants, with microorganisms detected on the internal air path surfaces of 92.3% of these blowers. Isolates of Staphylococcus aureus, coagulase-negative Staphylococcus, and methicillin-resistant S aureus were detected in 13.5%, 3.9%, and 1.9% of FAW blowers, respectively. Conclusion: The design of popular FAW devices using the 200708C filter was found to be inadequate for preventing the internal buildup and emission of microbial contaminants into the operating room. Substandard intake filtration allowed airborne contaminants (both viable and nonviable) to penetrate the intake filter and reversibly attach to the internal surfaces within the FAW blowers. The reintroduction of these contaminants into the FAW blower air stream was detected and could contribute to the risk of cross-infection. Given the deficiencies identified with the 200708C intake filter, the introduction of a new filter (model 200708D) with substantially lower retention efficiency is of concern. Copyright © 2011 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved. Source

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