USMA Digital Commons (United States Military Academy, West Point)
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Lagrangian and Impedance-Spectroscopy Treatments of Electric Force Microscopy
No full textScanning probe microscopy is often extended beyond simple topographic imaging to study electrical forces and sample properties, with the most widely used experiment being frequency-modulated Kelvin probe force microscopy. The equations commonly used to interpret this frequency-modulated experiment, however, rely on two hidden assumptions. The first assumption is that the tip charge oscillates in phase with the cantilever motion to keep the tip voltage constant. The second assumption is that any changes in the tip-sample interaction happen slowly. Starting from an electromechanical model of the cantilever-sample interaction, we use Lagrangian mechanics to derive coupled equations of motion for the cantilever position and charge. We solve these equations analytically using perturbation theory, and, for verification, numerically. This general approach rigorously describes scanned probe experiments even in the case when the usual assumptions of fast tip charging and slowly changing samples properties are violated. We develop a Magnus-expansion approximation to illustrate how abrupt changes in the tip-sample interaction cause abrupt changes in the cantilever amplitude and phase. We show that feedback-free time-resolved electric force microscopy cannot uniquely determine subcycle photocapacitance dynamics. We then use first-order perturbation theory to relate cantilever frequency shift and dissipation to the sample impedance even when the tip charge oscillates out of phase with the cantilever motion. Analogous to the treatment of impedance spectroscopy in electrochemistry, we apply this approximation to determine the cantilever frequency shift and dissipation for an arbitrary sample impedance in both local dielectric spectroscopy and broadband local dielectric spectroscopy experiments. The general approaches that we develop provide a path forward for rigorously modeling the coupled motion of the cantilever position and charge in the wide range of electrical scanned probe microscopy experiments where the hidden assumptions of the conventional equations are violated or inapplicable
Dean\u27s Significant Activities Report 06-21-2019
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/1005/thumbnail.jp
Atmospheric Flow Validation for Contaminant Transport
Get PDFPresentation on atmospheric flow validation for contaminant transport.https://digitalcommons.usmalibrary.org/presentations/1015/thumbnail.jp
Current Military Academy Service Obligation: Good for Civil-Military Relations
Get PDFImagine receiving a free undergraduate education at one of the best colleges in the United States. The military academies provide this. Any economist, however, will tell you that there is no such thing as a free lunch. The American tax payer foots the bill for all those who are admitted to attend one of the military’s academies. In exchange, these citizens will commission as officers and serve an obligation of five years on active duty. The most recent National Defense Authorization Act (NDAA) includes a section directing the Secretary of Defense to assess if this five-year service obligation should be extended. Congress is now questioning if the increase in the cost of educating and training should equate to an increase in time served for graduates. In short, is the nation getting “an adequate return on investment for a service academy graduate?
Student Energy Audits of Buildings Can be Done!
No full textEnergy conservation and sustainability are at the forefront of engineering today. It is imperative that engineering educators lead in this effort by showing the next generation of engineers that they can have a real impact by saving our energy and resources; this is especially effective when students are led on a journey of discovery, resulting in genuine learning (Adler, 1982). Luckily, it is easy to demonstrate energy conservation in real environments for hands on learning, even right on campus!
In the course Green Facilities Management, student groups performed energy audits of two separate buildings on campus, one constructed in 1948 and the other in 2014[KLCUU1] [SVACUU2] . Students first learned about energy sources and then analyzed an actual energy bill; the students then dug into the creation of green buildings, management of renewable energy sources, and life cycle costing. This was supplemented by a key hands-on portion, with building inspection, which included wall and roof material, insulation levels, window and door sizes, leaks, lighting and appliance loads. Occupant interviews were conducted to determine hours of operations and uses, and heating and cooling loads were calculated using real-world sources, like heat given off by people, solar radiation, conduction, and ancillary heat gain. Students then analyzed Energy Management Opportunities (EMOs), Green Energy Opportunities (GEOs) and life cycle costs and stated their prioritized recommendations, including an evaluation of installed and possible future green measures. Finally, during an oral presentation, the buildings, EMOs and GEOs were compared.
Results were assessed through both student feedback and project quality. Students appreciated the realistic project and being able to look at energy efficiency and the economics of sustainability. Projects were assessed by the instructor and 78% of the class had a B+ or higher on the project, exceeding expectations. The oral presentation had similarly positive results
Dean\u27s Significant Activities Report 11-18-2019
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/1015/thumbnail.jp
Dean\u27s Significant Activities Report 11-15-2019
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/1023/thumbnail.jp
Increased Glenoid Retroversion Is Associated With Increased Rotator Cuff Strength in the Shoulder.
No full textBACKGROUND: The rotator cuff muscles are critical secondary stabilizers in the shoulder. Increased glenoid retroversion and rotator cuff strength have been associated with the risk of posterior shoulder instability; however, the effect of increased glenoid retroversion on rotator cuff strength remains unclear.
PURPOSE/HYPOTHESIS: The purpose was to examine the association between glenoid version and rotator cuff strength in the shoulder in a young and healthy population with no history of shoulder instability. The hypothesis was that increased glenoid retroversion would be associated with increases in rotator cuff muscle strength.
STUDY DESIGN: Cross-sectional study; Level of evidence, 3.
METHODS: A prospective cohort study was conducted over a 4-year period within a high-risk population to identify the risk factors for shoulder instability. Analyzed participants included 574 freshmen entering a United States service academy. Baseline data collected upon entry into the study included magnetic resonance imaging measurements of glenoid version. Rotator cuff strength was also assessed at baseline using a handheld dynamometer. Internal and external rotation strength were assessed with the glenohumeral joint positioned in neutral and in 45° of abduction. The current study represents an analysis of the baseline data from this cohort.
RESULTS: The mean age, height, and weight of participants was 18.77 ± 0.97 years, 176.81 ± 8.48 cm, and 73.80 ± 12.45 kg, respectively. The mean glenoid version at baseline was 7.79°± 4.85° of retroversion. Univariate linear regression analyses demonstrated that increased glenoid retroversion was associated with increased internal and external rotation strength of the rotator cuff in neutral and 45° of abduction (
CONCLUSION: The results of this study demonstrate that as glenoid retroversion increases, internal and external rotation strength of the rotator cuff also increase in a young and healthy athletic population. These compensatory changes may contribute to increased glenohumeral dynamic stability in the presence of worse static stability with increasing retroversion
Neglecting regression to the mean continues to lead to unwarranted conclusions: Letter regarding The magnitude of weight loss induced by metformin is independently associated with BMI at baseline in newly diagnosed type 2 diabetes: Post-hoc analysis from data of a phase IV open-labeled trial .
No full textAs the prevalence of type 2 diabetes mellitus and obesity increases worldwide, scientifically rigorous research is needed in this field to determine effective interventions for the prevention and treatment of these chronic diseases. In a recent study published in this journal, Zhou et al. conclude that metformin, a drug used for treatment of type 2 diabetes mellitus, can be used effectively for weight loss, and that this effect is even more pronounced in individuals who weigh more at baseline. Unfortunately, we believe these results to be due to the regression to the mean (RTM) phenomenon, which weakens the causal inference proposed in this study. The conclusions of Zhou et al. that metformin is an effective strategy for weight loss in individuals with type 2 diabetes mellitus are not substantiated due to the lack of a control group and failure to consider other factors that may have confounded these results
Model-based Systems Engineering: Application and Lessons from a Technology Maturation Project
No full textThe Tactical Assault Light Operator Suit (TALOS) project is a Special Operations Command (SOCOM) initiative to enhance operator performance, situational awareness, survivability, and lethality. The project adopted a Model-Based Systems Engineering (MBSE) approach to manage the structural system configuration and support the test and integration plan. This approach relies on a unified model in the Systems Modeling Language (SysML) to capture the logical and physical aspects of the system design. The MBSE approach was used to develop a test and evaluation framework that allows for traceability of test plans back to performance requirements. Additionally, the model supported the integration of hardware and software as well as the design of wire harnesses; the MBSE approach provided benefits over more traditional integration techniques. This paper provides lessons learned including the need to balance requirements analysis with functional characterization and the products that were generated from the model. Overall the adoption of the MBSE approach provided lessons on managing a system’s configuration among a distributed team