3,664 research outputs found
A Navier-Stokes Solution of Hull-Ring Wing-Thruster Interaction
Navier-Stokes simulations of high Reynolds number flow around an axisymmetric body supported in a water tunnel were made. The numerical method is based on a finite-differencing high resolution second-order accurate implicit upwind scheme. Four different configurations were investigated, these are: (1) barebody; (2) body with an operating propeller; (3) body with a ring wing; and (4) body with a ring wing and an operating propeller. Pressure and velocity components near the stern region were obtained computationally and are shown to compare favorably with the experimental data. The method correctly predicts the existence and extent of stern flow separation for the barebody and the absence of flow separation for the three other configurations with ring wing and/or propeller
Robotic Partial Nephrectomy for a Peripheral Renal Tumor
Partial nephrectomy (PN) is the preferred surgical treatment for T1 renal tumors whenever technically feasible. When properly performed, it allows preservation of nephron mass without compromising oncologic outcomes. This reduces the postoperative risk of renal insufficiency, which translates into better overall survival for the patients. PN can be technically challenging, because it requires the surgeon to complete the tasks of tumor excision, hemostasis and renorrhaphy, all within an ischemic time of preferably below 30 minutes. The surgeon needs to avoid violating the tumor margins while leaving behind the maximal parenchymal volume at the same time. Variations such as zero ischemia, early unclamping, and selective clamping have been developed in an attempt to reduce the negative impact of renal ischemia, but inevitably add to the steep learning curves for any surgeon. Being able to appreciate the fine details of each surgical step in PN is the fundamental basis to the success of this surgery. The use of the robotic assistance allows a good combination of the minimally invasive nature of laparoscopic surgery and the surgical exposure and dexterity of open surgery. It also allows the use of adjuncts such as concurrent ultrasound assessment of the renal mass and intraoperative fluorescence to aid the identification of tumor margins, all with a simple hand switch at the console. Robot-assisted laparoscopic PN is now the most commonly performed type of PN in the United States and is gaining acceptance on the global scale. In this video, we illustrate the steps of robot-assisted laparoscopic PN and highlight the technical key points for success
The Purposes and Accountability of the Corporation in Contemporary Society: Corporate Governance at a Crossroads
Little attention has been paid to how the governance structures of public corporations adapt to structural changes in the social, political, economic and legal environments in which they operate. Bradley et al chronicle the recent changes in the conduct of business enterprise and establish the necessary conditions for a system of corporate governance capable of accommodating these changes
Two generalizations of the PRV conjecture
Let G be a complex connected reductive group. The PRV conjecture, which was
proved independently by S. Kumar and O. Mathieu in 1989, gives explicit
irreducible submodules of the tensor product of two irreducible G-modules. This
paper has three aims. First, we simplify the proof of the PRV conjecture, then
we generalize it to other branching problems. Finally, we find other
irreducible components of the tensor product of two irreducible G-modules that
appear for "the same reason" as the PRV ones
FiSH: Fair Spatial Hotspots
Pervasiveness of tracking devices and enhanced availability of spatially
located data has deepened interest in using them for various policy
interventions, through computational data analysis tasks such as spatial hot
spot detection. In this paper, we consider, for the first time to our best
knowledge, fairness in detecting spatial hot spots. We motivate the need for
ensuring fairness through statistical parity over the collective population
covered across chosen hot spots. We then characterize the task of identifying a
diverse set of solutions in the noteworthiness-fairness trade-off spectrum, to
empower the user to choose a trade-off justified by the policy domain. Being a
novel task formulation, we also develop a suite of evaluation metrics for fair
hot spots, motivated by the need to evaluate pertinent aspects of the task. We
illustrate the computational infeasibility of identifying fair hot spots using
naive and/or direct approaches and devise a method, codenamed {\it FiSH}, for
efficiently identifying high-quality, fair and diverse sets of spatial hot
spots. FiSH traverses the tree-structured search space using heuristics that
guide it towards identifying effective and fair sets of spatial hot spots.
Through an extensive empirical analysis over a real-world dataset from the
domain of human development, we illustrate that FiSH generates high-quality
solutions at fast response times
An analogue of the Wiener Tauberian theorem for the Heisenberg motion group
We show that the Wiener Tauberian property holds for the Heisenberg Motion group Tn⊲<Hn. This is a special case of the same result for a wider class of groups. However, our exposition is almost self contained and the techniques used in the proof are relatively simple
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