Passive Cavity Deflation after Water Entry Facilitated by a Vented Tube

When an object enters water, a crater, or air cavity, can form around the object and remain attached as the object travels underwater. Cavities can be beneficial and reduce drag force but there may be times when the cavity needs to be removed. This research proposes a method to remove air cavities by letting air leave the cavity, deflating the cavity similar to how a balloon is deflated. To provide air a path to leave the cavity, a tube with vent holes is attached to the object. The vent holes are located near the object, where the air cavity forms, and allow the air to move from the cavity out through the tube. Cavities for objects with and without the vented tube are compared using images from a high-speed cameras. Different vented tube lengths, vented tube diameters, vent hole areas, and impact velocities are compared. If the vented tube is long enough that it is outside of the cavity then the air will leave and the cavity deflates. As the vented tube length and vented tube diameter increase, the amount of air that leaves the cavity increases. Similarly as vent hole area increases, the amount of air that leaves the cavity increases until the holes get too large and the cavity fills with water before all the air can leave, trapping the remaining air in the cavity. How impact velocity effects the amount of air that leaves the cavity depends on the vented tube length. The critical vented tube length required for deflation to occur depends on the sphere radius, impact velocity, and vented tube diameter. The noise the cavity makes and the acceleration of the object as it travels underwater are compared for deflating cavities and non-deflating cavities and the results show that cavity deflation reduces both noise and acceleration

INTERIM REPORT IMPROVED METHODS FOR INCORPORATING RISK IN DECISION MAKING

This paper reports observations and preliminary investigations in the first phase of a research program covering methodologies for making safety-related decisions. The objective has been to gain insight into NRC perceptions of the value of formal decision methods, their possible applications, and how risk is, or may be, incorporated in decision making. The perception of formal decision making techniques, held by various decision makers, and what may be done to improve them, were explored through interviews with NRC staff. An initial survey of decision making methods, an assessment of the applicability of formal methods vis-a-vis the available information, and a review of methods of incorporating risk and uncertainty have also been conducted

Adolf Hitler's Decision to Invade the Soviet Union

This study makes use not only of German documents captured during the Second World War but of personal accounts of major figures of the Third Reich and their testimony at the Nuremberg Trials. Organized into five chapters, this study surveys Nazi- Soviet relations from 1939 to 1941, from the German viewpoint, with emphasis on Adolf Hitler's assessment of Russian policies and Germany's wartime situation, both of which factors shaped his decision to invade the USSR. The conclusion is that Hitler saw his attack on the Soviet Union as a preventive war, carried out to destroy a growing threat to the Reich. He interpreted Russian activities during the period 1939-1941 as designed to strengthen the USSR strategically against Germany in preparation for intervention in the ongoing conflict with Britain

Design, Manufacturing, and Integration of Fins for 2017-2018 OSU ESRA 30k Rocket

The Oregon State University (OSU) Experimental Sounding Rocket Association (ESRA) 30k Rocket Team is a student run rocket team that competes in the Intercollegiate Rocket Engineering Competition at Spaceport America. The goal of the competition is to launch a student designed, manufactured, and tested experimental sounding rocket to 30,000 ft carrying a 10 lb. scientific payload. One component of the rocket is the fins which provide stability for the rocket. The 2017-2018 OSU ESRA 30k rocket fins are composite fins with a clipped delta planform and a double diamond cross-section. The purpose of this thesis to present the design, manufacturing, integration, and testing processes for the 2017-2018 OSU ESRA 30k rocket fins. The goal is that this thesis will be a reference and a guide for future OSU rocket teams. Background research on fins and optimal fin design is presented and the manufacturing and integration processes are described in detail. Test results are also presented. Additionally, the many lesson learned throughout the process of designing, manufacturing, integrating, and testing the fins are presented to help future teams build better fins and avoid common mistakes. Key Words: ESRA, Rocket, Fins, Design, Manufacturing, Integration, Composite

Thermonuclear burn-up in deuterated methane CD4CD_4

The thermonuclear burn-up of highly compressed deuterated methane CD$_4$ is considered in the spherical geometry. The minimal required values of the burn-up parameter $x = \rho_0 \cdot r_f$ are determined for various temperatures $T$ and densities $\rho_0$. It is shown that thermonuclear burn-up in $CD_4$ becomes possible in practice if its initial density $\rho_0$ exceeds $\approx 5 \cdot 10^3$ $g \cdot cm^{-3}$. Burn-up in CD$_2$T$_2$ methane requires significantly ($\approx$ 100 times) lower compressions. The developed approach can be used in order to compute the critical burn-up parameters in an arbitrary deuterium containing fuel

Model selection in High-Dimensions: A Quadratic-risk based approach

In this article we propose a general class of risk measures which can be used for data based evaluation of parametric models. The loss function is defined as generalized quadratic distance between the true density and the proposed model. These distances are characterized by a simple quadratic form structure that is adaptable through the choice of a nonnegative definite kernel and a bandwidth parameter. Using asymptotic results for the quadratic distances we build a quick-to-compute approximation for the risk function. Its derivation is analogous to the Akaike Information Criterion (AIC), but unlike AIC, the quadratic risk is a global comparison tool. The method does not require resampling, a great advantage when point estimators are expensive to compute. The method is illustrated using the problem of selecting the number of components in a mixture model, where it is shown that, by using an appropriate kernel, the method is computationally straightforward in arbitrarily high data dimensions. In this same context it is shown that the method has some clear advantages over AIC and BIC.Comment: Updated with reviewer suggestion

Mixtures of Regression Models for Time-Course Gene Expression Data: Evaluation of Initialization and Random Effects

Finite mixture models are routinely applied to time course microarray data. Due to the complexity and size of this type of data the choice of good starting values plays an important role. So far initialization strategies have only been investigated for data from a mixture of multivariate normal distributions. In this work several initialization procedures are evaluated for mixtures of regression models with and without random effects in an extensive simulation study on different artificial datasets. Finally these procedures are also applied to a real dataset from E. coli