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Experimental Study of a Turbulent Impinging Jet in an Undergraduate Heat Transfer Laboratory
No full textIn many industrial applications, a single gas jet or array of jets can impinge upon a surface to enhance heating, cooling or drying effects. This forced convection phenomenon is covered in several heat transfer textbooks in undergraduate engineering courses. An experimental apparatus was developed for students to measure the convection heat transfer coefficient of a single and array of round impinging jets of air upon a resistively heated flat plate. The jet or jet array is directed on one side of the thin plate while the temperature distribution is measured using an infrared camera on the back side. An energy balance allows for estimation of the local and average convection coefficients, presented as non-dimensional Nusselt numbers, which are then compared against correlations in the literature. Experiments with various Reynolds numbers and separation distances between the nozzle and plate are in agreement with correlations, for both a single jet and hexagonal array of 7 jets. This apparatus will be implemented into a laboratory exercise for the heat transfer course at the United States Military Academy
3D MRI Measurements of the Effects of Wind Direction on Flow Characteristics and Contaminant Dispersion in a Model Urban Canopy
No full textThree dimensional velocity fields and contaminant dispersion within an evenly spaced orthogonal array of cubic buildings (height = H) with a central tall building (height = 3H) were studied to examine the influence of tall buildings and wind orientation within an urban canopy. Mean velocity and contaminant data were collected using magnetic resonance velocimetry and magnetic resonance concentration methods. Two building orientations, each angled at 0° and 45° with respect to the bulk flow, were examined. The single tall building strongly influenced the distribution of the streamwise and vertical mass fluxes in both wind orientations. In particular, the tall building wake strongly influences how mass and momentum are transported downward into the building canopy. The contaminant dispersion pattern was dependent on the size of separation regions behind buildings and the wind orientation relative to the street canyons. A plume of contaminant trailed behind the tall building and was dispersed by the building wake turbulence. This dispersion was more rapid for the 45° wind orientation likely due to the wider wake in this case. The complex mean flow within the canopy plays a major role in controlling ground level dispersion when the wind is not aligned with the street canyons. The relatively simple geometry of the canopy and the detailed full field velocity and concentration data make this an ideal case for testing simulations
Cardiometabolic thresholds for peak 30-min cadence and steps/day
No full textPURPOSE: To provide empirically-supported thresholds for step-based intensity (i.e., peak 30-min cadence; average of the top 30 steps/min in a day) and steps/day in relation to cardiometabolic health outcomes.
METHODS: Receiver operating characteristic curve analysis was applied to the National Health and Nutrition Examination Survey (NHANES) 2005-2006 accelerometer-derived step data to determine steps/day and peak 30-min cadence as risk screening values (i.e., thresholds) for fasting glucose, body mass index, waist circumference, high blood pressure, triglycerides, and HDL cholesterol. Thresholds for peak 30-min cadence and steps/day were derived that, when exceeded, classify the absence of each cardiometabolic risk factor. Additionally, logistic regression models that included the influence of age and smoking were developed using the sample weights, primary sampling units (PSUs), and stratification variables provided by the NHANES survey. Finally, a decision tree analysis was performed to delineate criteria for at-risk versus healthy populations using cadence bands.
RESULTS: Peak 30-min cadence thresholds across cardiometabolic outcomes ranged from 66-72 steps/min. Steps/day thresholds ranged from 4325-6192 steps/day. Higher thresholds were observed in men compared to women. In men, higher steps/day thresholds were observed in age ranges of 30-39, while in women, higher thresholds were observed in the age-range 50-59 years. Decision trees for classifying being at low risk for metabolic syndrome contained one risk-free leaf at higher cadence bands, specifically for any time accumulated at ≥120 steps/min.
CONCLUSIONS: Minimum thresholds representing absence of cardiometabolic risk range from 4325-6192 steps/day and 66-72 steps/min for peak 30-min cadence. Any time accumulated at ≥120 steps/min was associated with an absence of cardiometabolic risk. Although based on cross-sectional data, these thresholds represent potentially important and clinically interpretable daily physical activity goals
Dean\u27s Significant Activities Report 08-02-2019
Get PDFThe Dean’s Weekly Significant Activities Report lists all activities conducted within the Departments, Centers & Staff. The Report is provided to the Dean and Directorate personnel for situational awareness.https://digitalcommons.usmalibrary.org/sigact/1010/thumbnail.jp
An active and incremental learning framework for the online prediction of link quality in robot networks
No full textThis paper presents a comprehensive framework for the active and incremental learning of link quality (LQ) in robot networks. Mobile robots need foresight into the quality of their wireless links in order to proactively optimize routing, plan mobility routes, avoid disconnects, and make other network optimizations. However, the task of predicting LQ is nontrivial. Many environmental factors that influence the quality of radio wave propagation are dynamic, and thus, robots must continually learn and update their prediction models while they operate online. Prior work in the field uses online learning algorithms for predicting LQ, but this approach is costly in terms of energy and network capacity because of the need for a consistent stream of LQ labels to be transmitted from the receiver to the transmitter. Hence, this paper introduces a framework to reduce these overhead expenses by incorporating active learning to selectively label only a portion of the samples from the data stream. The framework also uses incremental training batches to conserve labeling resources, and updates the batches using change detection and forgetting mechanisms to mitigate concept drift. Experimental results reveal that the framework reduces label queries by up to 21.5% and prediction error by up to 9% after periods of concept drift
Childhood obesity intervention studies: A narrative review and guide for investigators, authors, editors, reviewers, journalists, and readers to guard against exaggerated effectiveness claims.
No full textBeing able to draw accurate conclusions from childhood obesity trials is important to make advances in reversing the obesity epidemic. However, obesity research sometimes is not conducted or reported to appropriate scientific standards. To constructively draw attention to this issue, we present 10 errors that are commonly committed, illustrate each error with examples from the childhood obesity literature, and follow with suggestions on how to avoid these errors. These errors are as follows: using self-reported outcomes and teaching to the test; foregoing control groups and risking regression to the mean creating differences over time; changing the goal posts; ignoring clustering in studies that randomize groups of children; following the forking paths, subsetting, p-hacking, and data dredging; basing conclusions on tests for significant differences from baseline; equating no statistically significant difference with equally effective ; ignoring intervention study results in favor of observational analyses; using one-sided testing for statistical significance; and stating that effects are clinically significant even though they are not statistically significant. We hope that compiling these errors in one article will serve as the beginning of a checklist to support fidelity in conducting, analyzing, and reporting childhood obesity research
A Hybrid Software Defined Network Platform for Undergraduate Research and Education
Get PDFSoftware Defined Networks (SDNs) are leading the evolution toward network programmability and open architectures. While many corporations, nonprofits, and individuals have developed training on SDNs, the industry has a significant gap with the robustness of entrenched traditional network educational models, such as Cisco’s Networking Academy. The Department of Defense (DoD) will likely adopt some form of SDN into its global transport network at various tiers and authority boundaries. It is imperative for 21st century leaders to understand how and why the manner in which DoD provides Information Technology (IT) services to its customers is changing with such rapidity. Therefore, we developed three basic SDN course lessons as a base of knowledge and support and integrated a hybrid physical SDN research platform into existing laboratory infrastructure for faculty research and capstone projects for senior cadets. This was accomplished by leveraging existing SDN-related tutorials and resources and integrating them within a virtualized SDN simulation environment. The three lessons were developed for integration into our core networking course that describes fundamental networking concepts in the context of an SDN - with a centralized control plane, while ensuring lesson learning objectives were achievable by non-technical majors yet sufficiently comprehensive across the fundamental operations of an SDN. The hybrid research platform consists of a number of Virtual Machines (VMs) running Mininet1 - an SDN simulation environment - and hosted on a VMware vSphere cluster with direct connectivity to twelve physical openflow-capable switches. This will allow students in the networking course to plan, design, implement, and test a basic SDN topology in either a virtual, physical, or hybrid environment. In addition, it will provide topological and experimental flexibility to student and faculty researchers and senior capstone project teams alike
A Systems Approach for Analyzing Operational Energy Requirements for the Warfighter
No full textWarfighters are carrying increasing amounts of electronics to provide them a tactical edge. These electronics are now imposing a substantial operational energy burden where missions are often constrained by energy requirements. Current operational energy analyses typically only look at the power draw of individual equipment. However, a systems approach more holistically captures these operational energy requirements. A system is defined to consist of the following three components: the soldier, their equipment, and the mission. This analysis then defines each component and then evaluates the interactions between them. These definitions and interactions are captured through a series of tables that can be built in Microsoft Excel which allows for tradespace analysis. This paper outlines this process and presents two case studies. The first case study evaluates adding energy harvesters to a dismounted rifle squad during a 72-hour movement to contact. The second case study evaluates adding a solar blanket to power electronics in a military vehicle during a 24-hour overwatch mission
Inkjet-Printed Carbon Nanotubes for Fabricating a Spoof Fingerprint on Paper.
Get PDFA spoof fingerprint was fabricated on paper and applied for a spoofing attack to unlock a smartphone on which a capacitive array of sensors had been embedded with a fingerprint recognition algorithm. Using an inkjet printer with an ink made of carbon nanotubes (CNTs), we printed a spoof fingerprint having an electrical and geometric pattern of ridges and furrows comparable to that of the real fingerprint. With this printed spoof fingerprint, we were able to unlock a smartphone successfully; this was due to the good quality of the printed CNT material, which provided electrical conductivities and structural patterns similar to those of the real fingerprint. This result confirms that inkjet-printing CNTs to fabricate a spoof fingerprint on paper is an easy, simple spoofing route from the real fingerprint and suggests a new method for outputting the physical ridges and furrows on a two-dimensional plane
Potential for Army Integration of Autonomous Systems by Warfighting Function
Get PDFThe article explains the maximum extent that the U.S. Army can integrate autonomous systems into its operations given the inherent limitations of the technology. Topics include these limitations determine the appropriateness of using autonomous systems to perform each of the broad range of Army tasks that are captured through the warfighter functions and the six warfighting functions of the U.S. Army include mission command, intelligence and protection