CT Associates Inc.

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CT Associates Inc.

CT, United States
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Malla R.B.,University of Connecticut | Vila L.J.,CT Associates Inc.
Proceedings of the International Astronautical Congress, IAC | Year: 2016

Planetary drilling is a vital task in the challenge for space exploration and human colonization. Special percussive planetary drilling devices such as the Ultrasonic/Sonic Driller/Corer (USDC) and Auto-Gopher have been developed by Honeybee Robotics Spacecraft Mechanisms Corporation and NASA Jet Propulsion Laboratory to overcome the limitations of current drilling devices for planetary exploration. The percussive mechanism of the USDC and Auto-Gopher consists of an ultrasonic horn, a free mass, and the drill rod. During drilling operation the ultrasonic horn is vibrated via a piezoelectric actuator. The free mass, located between the ultrasonic horn and the drill rod, is struck by the ultrasonic horn and driven towards the drill rod. The free mass oscillates between the top of the drill rod and the bottom of the ultrasonic horn, thus creating repeated impacts. In this study, the analysis of the local interaction between the free mass-ultrasonic horn and free mass-drill rod and the dynamic response of the overall system is presented. The contact interaction is analyzed using Hertz theory of contact, including the effects of structural vibration and structural damping. An in-house finite element code is utilized, in which a numerical integration scheme with equilibrium iterations is implemented to obtain the displacement of each component of the ultrasonic drill and the contact force developed during each impact. In addition, several support conditions (e.g. fixed, elastic, viscous) of the rod are considered. The effects of the support condition of the drill rod on the contact force and the dynamic response of the ultrasonic drill are presented. It was found that the frequency of oscillation of the free mass is smaller than that of the ultrasonic horn. This is consistent with the purpose of including the free mass to convert the high frequency oscillation of the ultrasonic horn into lower frequency impacts on the drill rod. The support condition of the drill rod affects the overall dynamic response of the ultrasonic percussive mechanism, however, the contact force is affected by the support condition of the drill rod only if the duration of contact between the free mass and the drill rod is larger than the time it takes the wave to travel through the rod and return to the impacted end of the rod. The oscillation frequency of the free mass was observed to be highest for the drill rod with fixed support compared with other support conditions considered in this study.

Malla R.B.,University of Connecticut | Vila L.J.,University of Connecticut | Vila L.J.,CT Associates Inc.
Engineering Structures | Year: 2017

Longitudinal impact of a mass (or hammer) on a drill rod has been used over the years on a number of terrestrial applications such as pile driving, rock drilling, and soil testing as well as in drilling devices designed to explore the subsurface of Lunar, Martian, and other planetary bodies. Previous studies have investigated the effects of the boundary conditions on the wave propagation on the rod. However, the coupled effect of the dynamic response, damping and the boundary conditions of the rod on the contact/impact force has not been considered. This paper presents the dynamic contact analysis of the longitudinal impact of a mass on a rod with rigid, free, deformable, and slip support conditions including the effect of damping of the rod. Focus is given to capture how and under what conditions the impact force is affected by the support conditions. The contact force was obtained using Hertz force-indentation relation coupled with the structural vibration of the rod. Both the contact force and the rod dynamic response are determined using mode superposition method as well as an in-house finite element code. A very good agreement is found between the results from the two methods. The results are verified with experimental data previously available in literature and using Abaqus FEA. It is found that for the undamped case the force is affected by the support condition only if the duration of contact between the striker and the rod is larger than the time that the displacement wave takes to travel through the rod to the other end and return back to the contact end. On the other hand, when damping of the rod is considered the contact force is observed to be affected by the support condition before the arrival of the reflected wave to the contact end. However, the effect of the support conditions in the damped case is significantly higher when the duration of contact is larger than the time of arrival of the reflected wave from the far end. When the rod penetrates into the supporting medium while the contact is present the contact force decreases at a higher rate compared with the case where penetration is not present during contact. © 2017 Elsevier Ltd

Rhinehart R.R.,Oklahoma State University | Darby M.L.,Principal CMiD Solutions | Wade H.L.,CT Associates Inc.
ISA Transactions | Year: 2011

The editorial section of ISA Transactions deals with the selection of advanced regulatory control (ARC). The editorial deals with a comparison of feedback control strategies, and includes nonlinear and adaptive algorithms along with model predictive control (MPC) in the definition of APC. Adaptive controllers have models or internal learning ability that adapts to the dynamic process data, tracks changes in process dynamics and gain, and uses the models for control action. MPC is the most often considered component of APC and MPC packages include some features, such as SISO or MISO constraint-handling control, linear MIMO Control, and nonlinear MIMO Control. Some of the significant benefits of advanced control include throughput increase, process stability improvement, energy consumption reduction, and increased yield of more valuable products.

Jeon S.,University of Minnesota | Oberreit D.R.,Kanomax FMT | Van Schooneveld G.,CT Associates Inc. | Hogan C.J.,University of Minnesota
Analytical Chemistry | Year: 2016

Despite the importance of examining the formation of nanoparticle-protein conjugates, there is a dearth of routine techniques for nanoparticle-protein conjugate characterization. The most prominent change to a nanoparticle population upon conjugate formation is a shift in the nanoparticle size distribution function. However, commonly employed dynamic light scattering based approaches for size distribution characterization are ineffective for nonmonodisperse samples, and further they are relatively insensitive to size shifts of only several nanometers, which are common during conjugate formation. Conversely, gas phase ion mobility spectrometry (IMS) techniques can be used to reliably examine polydisperse samples, and are sensitive to ∼1 nm size distribution function shifts; the challenge with IMS is to convert nanoparticle-protein conjugates to aerosol particles without bringing about nonspecific aggregation or conjugate formation. Except in limited circumstances, electrospray based aerosolization has proven difficult to apply for this purpose. Here we show that via liquid nebulization (LN) with online, high-flow-rate dilution (with dilution factors up to 10 000) it is possible to aerosolize nanoparticle-protein conjugates, enabling IMS measurements of their conjugate size distribution functions. We specifically employ the LN-IMS system to examine bovine serum albumin binding to gold nanoparticles. Inferred maximum protein surface coverages (∼0.025 nm-2) from measurements are shown to be in excellent agreement with reported values for gold from quartz crystal microbalance measurements. It is also shown that LN-IMS measurements can be used to detect size distribution function shifts on the order of 1 nm, even in circumstances where the size distribution function itself has a standard deviation of ∼5 nm. In total, the reported measurements suggest that LN-IMS is a potentially simple and robust technique for nanoparticle-protein conjugate characterization. © 2016 American Chemical Society.

Jeon S.,University of Minnesota | Oberreit D.R.,Kanomax FMT | Van Schooneveld G.,CT Associates Inc. | Hogan C.J.,University of Minnesota
Analyst | Year: 2016

We apply liquid nebulization (LN) in series with ion mobility spectrometry (IMS, using a differential mobility analyzer coupled to a condensation particle counter) to measure the size distribution functions (the number concentration per unit log diameter) of gold nanospheres in the 5-30 nm range, 70 nm × 11.7 nm gold nanorods, and albumin proteins originally in aqueous suspensions. In prior studies, IMS measurements have only been carried out for colloidal nanoparticles in this size range using electrosprays for aerosolization, as traditional nebulizers produce supermicrometer droplets which leave residue particles from non-volatile species. Residue particles mask the size distribution of the particles of interest. Uniquely, the LN employed in this study uses both online dilution (with dilution factors of up to 104) with ultra-high purity water and a ball-impactor to remove droplets larger than 500 nm in diameter. This combination enables hydrosol-to-aerosol conversion preserving the size and morphology of particles, and also enables higher non-volatile residue tolerance than electrospray based aerosolization. Through LN-IMS measurements we show that the size distribution functions of narrowly distributed but similarly sized particles can be distinguished from one another, which is not possible with Nanoparticle Tracking Analysis in the sub-30 nm size range. Through comparison to electron microscopy measurements, we find that the size distribution functions inferred via LN-IMS measurements correspond to the particle sizes coated by surfactants, i.e. as they persist in colloidal suspensions. Finally, we show that the gas phase particle concentrations inferred from IMS size distribution functions are functions of only of the liquid phase particle concentration, and are independent of particle size, shape, and chemical composition. Therefore LN-IMS enables characterization of the size, yield, and polydispersity of sub-30 nm particles. © The Royal Society of Chemistry 2016.

Vila L.J.,CT Associates Inc. | Vila L.J.,University of Connecticut | Malla R.B.,University of Connecticut
Journal of Engineering Mechanics | Year: 2016

A series of special percussive drilling devices has been designed by the NASA Jet Propulsion Laboratory and Honeybee Robotics Spacecraft Mechanisms Corporation for exploration of planetary bodies (e.g., Mars). The percussive mechanism of these special drilling devices consists of three main components: ultrasonic horn, free mass, and drill bit/rod. This paper presents the analysis of the interaction between the free mass/striker and the drill rod including the coupled effects of structural vibration; plastic deformation of the rod; repeated impacts; and the support condition of the rod on the contact force, contact duration, and coefficient of restitution. The impact between the free mass and the drill rod is analyzed by means of a modified Hertz force-indentation relation coupled with the structural vibration obtained using the mode superposition method. The material of the striker is considered elastic, while the rod is considered as an elastic perfectly plastic material. A numerical integration scheme, with equilibrium iterations, is implemented to solve the system's equations. It is observed that for both support conditions considered, i.e., fixed and elastic support, the first impact yields the largest plastic deformation, which then decreases as the number of impacts increases. The maximum contact force and the coefficient of restitution are observed to increase with the number of impacts while the duration of contact decreases. Additionally, the effect of the support condition of the rod on the contact force decreases as the number of impacts increases. © 2016 American Society of Civil Engineers.

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.

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.

Viswanathan C.T.,CT Associates Inc.
Bioanalysis | Year: 2011

Incurred sample reanalysis (ISR) is accepted as both a fundamental concept and an integral part in the conduct of pharmacokinetic, bioequivalence and preclinical safety studies. Reproducibility demonstrated by ISR reinforces confidence that the method is valid and the results dependable. In this article, the history of the uptake of ISR is discussed and the current practices described. The industry is given credit for its awareness of the importance of, and implementation of, ISR practices in bioanalytical laboratories. Finally, in the context of the recent publication of guidelines for ISR by the EMA, implications for globalization and harmonization of regulations pertaining to ISR are described. © 2011 Future Science Ltd.

CT Associates Inc. | Date: 2013-09-19

A method and apparatus for measuring dissolved residue concentrations and particulate residue particle concentrations and size distribution in liquids, particularly colloidal suspensions. The method involves separating dissolved and particulate residues in liquids for subsequent analysis of the residue species. The method includes the steps of forming an aerosol from the liquid sample to be analyzed, evaporating the droplets in the aerosol to dryness, detecting and sizing the particles, and determining the liquid volumetric inspection rate. An apparatus for separating dissolved and particulate residues in liquids for determination of the concentrations of the two residue species as well as the size distribution of the particulate species is also disclosed. The apparatus includes a droplet former, a dryer communicatively connected to the droplet former, and a detector communicatively connected to the evaporator for detecting and sizing particles.

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