Norcross, GA, United States
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Javaheri B.,Royal Veterinary College | Stern A.R.,Engineering Systems Incorporated
Journal of Bone and Mineral Research | Year: 2014

The Wnt/β-catenin signaling pathway is essential for bone cell viability and function and for skeletal integrity. To determine if β-catenin in osteocytes plays a role in the bone anabolic response to mechanical loading, 18- to 24-week-old osteocyte β-catenin haploinsufficient mice (Dmp1-Cre × β-catenin fl/ +; HET cKO) were compared with their β-catenin fl/fl (control) littermates. Trabecular bone volume (BV/TV) was significantly less (58.3%) in HET cKO females versus controls, whereas male HET cKO and control mice were not significantly different. Trabecular number was significantly less in HET cKO mice compared with controls for both genders, and trabecular separation was greater in female HET cKO mice. Osteoclast surface was significantly greater in female HET cKO mice. Cortical bone parameters in males and females showed subtle or no differences between HET cKO and controls. The right ulnas were loaded in vivo at 100 cycles, 2 Hz, 2500 μÏμ, 3 days per week for 3 weeks, and the left ulnas served as nonloaded controls. Calcein and alizarin complexone dihydrate were injected 10 days and 3 days before euthanization, respectively. Micro-computed tomography (μCT) analysis detected an 8.7% and 7.1% increase in cortical thickness in the loaded right ulnas of male and female control mice, respectively, compared with their nonloaded left ulnas. No significant increase in new cortical bone formation was observed in the HET cKO mice. Histomorphometric analysis of control mice showed a significant increase in endocortical and periosteal mineral apposition rate (MAR), bone-formation rate/bone surface (BFR/BS), BFR/BV, and BFR/TV in response to loading, but no significant increases were detected in the loaded HET cKO mice. These data show that deleting a single copy of β-catenin in osteocytes abolishes the anabolic response to loading, that trabecular bone in females is more severely affected and suggest that a critical threshold of β-catenin is required for bone formation in response to mechanical loading. © 2014 American Society for Bone and Mineral Research.

Duvall D.E.,Engineering Systems Inc.
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2013

Polyolcfin pipe is known to be susceptible to oxidative degradation when used in potable water applications. Flowing water inside of such pipe will extract antioxidants from the inside surface of the pipe, causing diffusion-driven migration of more antioxidant from the pipe mid-wall to that surface. Disinfectants in potable water (e.g. hypochlorites, chlorine dioxide, chloramines, etc.) react with antioxidants in the pipe material, decreasing the amount of effective antioxidant until none remains and the polymer is unprotected against oxidation. Also, the response of polyolefin materials to oxidative degradation and the effect of such degradation on pipe performance varies with the different polyolefin polymers. This study presents the results of testing of the resistance of random copolymer polypropylene pipe to chlorinated water and the failure mechanisms observed in the tests.

Hayes M.D.,Engineering Systems Inc.
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2012

A new test method for evaluating the resistance of plastic pipe to chemical attack and environmental stress cracking (ESC) has been developed. The fixture is a simple extension of the tensile creep rupture test method to ring samples excised from pipes. The design allows for immersion in a variety of aging substances at any temperature and stress level. Simple mechanics equations for curved beams can be used to select the proper load for matching the maximum tensile stress in the ring geometry to the hoop stress in pressurized pipe, and finite element analysis (FEA) was performed to validate the application of the calculations. The results of the analysis, as well as preliminary aging experiments, demonstrate that the geometry causes preferential cracking in the middle of the specimen, away from cut edges. This test method has the advantage of simulating the real application and the development of crazing and cracking and eventual failure more realistically than a displacement-controlled test. Limitations of the geometry are also discussed.

Bernhardt R.P.,Engineering Systems Inc.
Structures Congress 2014 - Proceedings of the 2014 Structures Congress | Year: 2014

How does a structural engineer juggle all of the tasks required to complete multiple projects on-time, with quality and still have a quality life at home? Development of personal mission statements, personal values, and goals helps to set the foundation for setting priorities. Once priorities are understood, decisions can be made on how to discern between the urgent and the important tasks. Writing down every task as it comes to mind and routinely assigning priorities is necessary to keep from becoming overwhelmed. When there are concurrent multiple projects, Post-it® notes will not be adequate to keep track of everything. The entire process - from recording the task, to scheduling the task, to delegating a task, to completion of a task - will be described. One online task management software tool will be demonstrated as it relates to engineering projects. The structural engineer will take away some ideas for organizing life and increasing efficiency on the job, still attending to the tasks required for the important relationships in life. © 2014 American Society of Civil Engineers.

Mitolo M.,Engineering Systems Inc. | Pettinger A.,Engineering Systems Inc.
IEEE Transactions on Industry Applications | Year: 2016

Buried pipelines carrying hazardous products are mandated to be protected against corrosion, generally via layer(s) of coating materials integrated with active cathodic protection systems. Impressed-current systems, normally adopted for larger or longer structures, force the pipeline to behave as a cathode, therefore providing protection against corrosion of its exposed parts when the coating fails. Cathodically protected pipelines may, however, be buried in proximity of grounding electrodes, such as ground grids of substations; thus, they may need to be bonded to the grid to prevent, or lower, the risk of metal-to-metal touch voltages, as indicated in applicable technical standards. This bonding connection, required for the safety of the electrical operators, may, however, compromise the effectiveness of the cathodic protection, as well safety. In this paper, the authors explore the issues introduced by the coexistence of grounding systems and cathodic protection systems, and propose possible solutions to insure safety and, at the same time, protect assets and the environment from corrosion. © 1972-2012 IEEE.

Mitolo M.,Engineering Systems Inc. | Bajzek T.J.,Engineering Systems Inc.
IEEE Transactions on Industry Applications | Year: 2016

Touchable parts of electrical products and equipment can be thermally hot. Unintentional contact with hot surfaces during the normal operations of products may cause burns, and severity depends on the thermal resistivity of the material of the exposed part, the contact duration, the contact pressure, and skin conditions (i.e., dry, water wet, etc.). Currents flowing through equipment surfaces due to intentional choice or wiring errors can also elevate their temperatures, compounding the thermal effect; this causes an increased risk of triggering explosive atmospheres and fires in locations where combustible/flammable materials are processed or stored. In this paper, in light of applicable technical standards, the authors discuss and propose applicable burn thresholds, and permissible contact times with hot parts, based on different groups of users who may unintentionally touch the surfaces. The risk assessment of burning can be performed by comparing actual maximum temperatures of parts of electrical equipment against safe temperatures that a person may withstand for a given time without suffering a second degree burn. © 1972-2012 IEEE.

Stone D.H.,Engineering Systems Inc
Journal of Failure Analysis and Prevention | Year: 2016

The relatively recent appearance of formerly rare vertical split rim wheel failures provides a good case study of how a shift in failure mode occurs when a material improvement is made to solve an existing problem. The mode of railroad wheel failures have changed three times over the past 40 years when the dominate failure mode has been identified and corrected. When the principal failure mode has been corrected the service life increases, but a new or previously minor failure mode assumes the role of principle failure cause. Because of the large population of railroad wheels in North American service, failure trends can be easily observed. This paper will discuss the evolution of failure mode with successive material and structural improvements. © 2016 ASM International

Garber M.A.,Engineering Systems Inc.
2011 IRCOBI Conference Proceedings - International Research Council on the Biomechanics of Injury | Year: 2011

Primary research on the biomechanics of impact often informs accident investigation. Such research is the source of nearly all data on human injury tolerance, is the basis for the development of most biomechanical modeling techniques in common use, and provides crucial information on the performance of various occupant protection systems currently installed in vehicles. This paper utilizes a recent aviation accident study to highlight the ways that accident investigation contributes to, complements, and guides biomechanics research. Aside from the basic collection of epidemiological data on injury in vehicular crashes or other accident scenarios, accident investigation can provide detailed information regarding the effectiveness of injury countermeasures in real world situations, evidence of unintended consequences of such countermeasures, effects of population variation on injury causation, and assessment of actual (as opposed to nominal) use of various systems designed for end-users, among other information. In addition, accidents may serve to highlight issues that might otherwise get little attention. While this attention may not directly drive primary research, it certainly provides an important input into vehicular design issues. Ultimately, the importance of accident investigation in biomechanics research may be to help focus the question of why the research is important in the first place.

Hineman M.A.,Engineering Systems Inc. | Schmidt F.E.,Engineering Systems Inc.
Praktische Metallographie/Practical Metallography | Year: 2013

Copper piping systems for HVAC (Heating Ventilation Air Conditioning) are used to transport heating and cooling water in high rise buildings. Commercial and residential plumbing has a design life that must be specified with respect to the water quality parameters associated with the geographic location. Stress corrosion cracking has been identified as one of the failure mechanism normally occurring in the infancy of the life of the systems that is highly associated with contamination. A metallurgical analysis of the characteristics of typical cold worked tubing, used in copper piping, with insulation, contamination and crack morphology are presented. © Carl Hanser Verlag, München.

Brickman D.B.,Engineering Systems Inc.
ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 | Year: 2011

This paper addresses the ability of a human worker to activate safety devices to stop and reverse the mechanical infeed system inside a commercial tree chipper infeed hopper. Studies were performed using a tray equipped commercial tree chipper incorporating a safety control bar and safety cables to stop and reverse the mechanical infeed system. The test results indicate that the human test subject was able to successfully activate the safety control bar and the safety cables from a variety of body positions around and within the tree chipper infeed hopper. Copyright © 2011 by ASME.

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