Design and performance of the University of Michigan 6.6-inch hypersonic wind tunnel

The tunnel described has several design features intended to maintain laminar flow in the boundary layer of its nozzle. Measurements show that transition to turbulence in the nozzle wall boundary layer begins at the throat and is sensitive to surface roughness, heat transfer rate, and longitudinal radius of curvature. The observed dependence of transition on heat transfer rate is the reverse of that predicted by stability theory for infinitesimal disturbances. Tests include boundary layer surveys of a contoured nozzle and a conical nozzle with four interchangeable throats

Artemis Curation: Preparing for Sample Return from the Lunar South Pole

Space Policy Directive-1 mandates that the United States will lead the return of humans to the Moon for long-term exploration and utilization, followed by human missions to Mars and other destinations. In addition, the Vice President stated that It is the stated policy of this administration and the United States of America to return American astronauts to the Moon within the next five years, that is, by 2024. These efforts, under the umbrella of the recently formed Artemis Program, include such historic goals as the flight of the first woman to the Moon and the exploration of the lunar south-polar region. Among the top priorities of the Artemis Program is the return of a suite of geologic samples, providing new and significant opportunities for progressing lunar science and human exploration. In particular, successful sample return is necessary for understanding the history of volatiles in the Solar System and the evolution of the Earth-Moon system, fully constraining the hazards of the lunar polar environment for astronauts, and providing the necessary data for constraining the abundance and distribution of resources for in-situ resource utilization (ISRU). Here we summarize the ef-forts of the Astromaterials Acquisition and Curation Office (hereafter referred to as the Curation Office) to ensure the success of Artemis sample return (per NASA Policy Directive (NPD) 7100.10E)

Particle trajectories in linearized irrotational shallow water flows

We investigate the particle trajectories in an irrotational shallow water flow over a flat bed as periodic waves propagate on the water's free surface. Within the linear water wave theory, we show that there are no closed orbits for the water particles beneath the irrotational shallow water waves. Depending on the strength of underlying uniform current, we obtain that some particle trajectories are undulating path to the right or to the left, some are looping curves with a drift to the right and others are parabolic curves or curves which have only one loop

A rigorous implementation of the Jeans--Landau--Teller approximation

Rigorous bounds on the rate of energy exchanges between vibrational and translational degrees of freedom are established in simple classical models of diatomic molecules. The results are in agreement with an elementary approximation introduced by Landau and Teller. The method is perturbative theory ``beyond all orders'', with diagrammatic techniques (tree expansions) to organize and manipulate terms, and look for compensations, like in recent studies on KAM theorem homoclinic splitting.Comment: 23 pages, postscrip

Uniqueness and Nondegeneracy of Ground States for (−Δ)sQ+Q−Qα+1=0(-\Delta)^s Q + Q - Q^{\alpha+1} = 0 in R\mathbb{R}

We prove uniqueness of ground state solutions $Q = Q(|x|) \geq 0$ for the nonlinear equation $(-\Delta)^s Q + Q - Q^{\alpha+1}= 0$ in $\mathbb{R}$, where $0 < s < 1$ and $0 < \alpha < \frac{4s}{1-2s}$ for $s < 1/2$ and $0 < \alpha < \infty$ for $s \geq 1/2$. Here $(-\Delta)^s$ denotes the fractional Laplacian in one dimension. In particular, we generalize (by completely different techniques) the specific uniqueness result obtained by Amick and Toland for $s=1/2$ and $\alpha=1$ in [Acta Math., \textbf{167} (1991), 107--126]. As a technical key result in this paper, we show that the associated linearized operator $L_+ = (-\Delta)^s + 1 - (\alpha+1) Q^\alpha$ is nondegenerate; i.\,e., its kernel satisfies $\mathrm{ker}\, L_+ = \mathrm{span}\, \{Q'\}$. This result about $L_+$ proves a spectral assumption, which plays a central role for the stability of solitary waves and blowup analysis for nonlinear dispersive PDEs with fractional Laplacians, such as the generalized Benjamin-Ono (BO) and Benjamin-Bona-Mahony (BBM) water wave equations.Comment: 45 page

Use of Qualitative Methods in Published Health Services and Management Research: A 10-Year Review

Over the past 10 years, the field of health services and management research has seen renewed interest in the use of qualitative research methods. This article examines the volume and characteristics of qualitative research articles published in nine major health services and management journals between 1998 and 2008. Qualitative research articles comprise 9% of research articles published in these journals. Although the publication rate of qualitative research articles has not kept pace with that of quantitative research articles, citation analysis suggests that qualitative research articles contribute comparably to the field’s knowledge base. A wide range of policy and management topics has been examined using qualitative methods. Case study designs, interviews, and documentary sources were the most frequently used methods. Half of qualitative research articles provided little or no detail about key aspects the study’s methods. Implications are discussed and recommendations are offered for promoting the publication of qualitative research

Teaching Mathematics with Technology: TPACK and Effective Teaching Practices

This paper examines how 17 secondary mathematics teacher candidates (TCs) in four university teacher preparation programs implemented technology in their classrooms to teach for conceptual understanding in online, hybrid, and face to face classes during COVID-19. Using the Professional Development: Research, Implementation, and Evaluation (PrimeD) framework, TCs, classroom mentor teachers, field experience supervisors, and university faculty formed a Networked Improvement Community (NIC) to discuss a commonly agreed upon problem of practice and a change idea to implement in the classroom. Through Plan-Do-Study-Act cycles, participants documented their improvement efforts and refinements to the change idea and then reported back to the NIC at the subsequent monthly meeting. The Technology Pedagogical Content Knowledge framework (TPACK) and the TPACK levels rubric were used to examine how teacher candidates implemented technology for Mathematics conceptual understanding. The Mathematics Classroom Observation Protocol for Practices (MCOP2) was used to further examine how effective mathematics teaching practices (e.g., student engagement) were implemented by TCs. MCOP2 results indicated that TCs increased their use of effective mathematics teaching practices. However, growth in TPACK was not significant. A relationship between TPACK and MCOP2 was not evident, indicating a potential need for explicit focus on using technology for mathematics conceptual understanding

On the particle paths and the stagnation points in small-amplitude deep-water waves

In order to obtain quite precise information about the shape of the particle paths below small-amplitude gravity waves travelling on irrotational deep water, analytic solutions of the nonlinear differential equation system describing the particle motion are provided. All these solutions are not closed curves. Some particle trajectories are peakon-like, others can be expressed with the aid of the Jacobi elliptic functions or with the aid of the hyperelliptic functions. Remarks on the stagnation points of the small-amplitude irrotational deep-water waves are also made.Comment: to appear in J. Math. Fluid Mech. arXiv admin note: text overlap with arXiv:1106.382

Relationships Between Gratitude and Mental Health Difficulties During the COVID-19 Pandemic in a Southern Region of the United States

Introduction: The extensive disruptions of the COVID-19 pandemic have led to heightened concerns about mental health sequelae. There has been significant interest in identifying factors associated with psychosocial vulnerability or resilience. Aims: This study examined associations of trait gratitude with mental health difficulties among community residents in a southern state of the US. Methods: In this cross-sectional online investigation, 543 adults were assessed during an earlier phase of the pandemic, characterized by the reopening of facilities but mounting infection rates. Participants were evaluated using a validated measure of trait gratitude and clinically relevant screening assess-ments of depression, anxiety, and trauma symptoms. Results: After adjusting for a range of pandemic-associated burdens and sociodemographic factors, multivariable analyses indicated that gratitude was significantly related to diminished levels of depres-sion, anxiety, and trauma. These effects remained significant after additional adjustment for other psychosocial resources (religiousness and perceived support). Conclusions: Findings provide novel information regarding relationships between gratitude and reduced mental health difficulties among community residents during a stressful period early in the pandemic. Results set the stage for longitudinal research. A disposition to identify and appreciate beneficial experiences might contribute to more favorable adaptation to communal crises, and warrants further investigation