217 research outputs found
Extension of the -BEM library for use in a seakeeping pipeline
The problem of seakeeping consists, among other aspects, of studying how a ship reacts to the environmental conditions during navigation, to establish operational limits and verify the seaworthiness of the vessel. A classic approach is to model the ship as a filter, with a set of Response Amplitude Operators (RAO) transforming the wave elevation time series into the motions in the six degrees of freedom.
Thanks to the convolutional properties of the Fast Fourier Transform, a wave elevation time series can then be converted to the prediction of ship motions in real time. For different ship speeds, wave directions and wave frequencies, the RAOs can be determined from the added masses, damping and hydrostatic coefficients, and wave-induced forces and moments. These entities can be obtained from the solutions of suitable complex-valued potential flow problems, in an offline phase.
This work, developed as part of the Winning a Sea State project in collaboration with Cetena, illustrates the extension of the potential flow solver -BEM to support these formulations, in order to provide an efficient, scalable, open source basis for a pipeline of this type. Results for the added mass and damping coefficients of a semi-submerged sphere in the zero-speed case compare favorably with the theory
Machine Learning and Feature Selection for Videogame Beta Testing
This work presents the integration of Machine Learning techniques in the beta testing phase of Heartbot - Escape, a commercial video game, in order to help the game designer in the identification of the game parameters and player characteristics that have the most influence on metrics such as entertainment and difficulty. The game was analysed to define the actual input features and several classification outputs, data collection was designed and performed and data were then analysedope
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Report on the performance of a large-area, gamma-ray imager for search
We are currently constructing a prototype, large-area, gamma-ray detector for conducting vehicle-mounted, mobile-search operations. The system is unique in that it relies on imaging to discriminate point sources of interest from the natural background variations. In a non-imaging instrument the background fluctuations mimic the signature seen from real sources at a distance and one is limited in sensitivity to detecting only those sources that overwhelm the local background variations --not just the counting statistics associated with a given measurement. The net result is that a larger detector is generally not more sensitive to detecting sources in the world at large. [1, 2] In a previous publication [3] we reported on the detection of a 1-mCi source at more than 80 meters from the detector using a proof-of-principle instrument (see Fig. 1) constructed to demonstrate how imaging removes the size limit on search instruments. In this report we document a systematic effort using the same detector to demonstrate that imaging detectors can reliably detect weak radiation sources at many 10's of meters. Specifically, we collected data on a 1-mCi {sup 137}Cs source 65 m from the path of the search instrument
Meta-analysis on the effect of mild primary hyperparathyroidism and parathyroidectomy upon arterial stiffness
CONTEXT: current data about the cardiovascular manifestations of mild primary hyperparathyroidism (pHPT) are often conflicting. Pulse wave velocity (PWV) is the gold-standard method for assessing aortic stiffness, which predicts cardiovascular morbidity and mortality.OBJECTIVE: Primary outcomes were to investigate if mild pHPT was associated with higher PWV and if parathyroidectomy (PTX) reduced PWV in mild pHPT. Secondary outcome was to investigate blood pressure changes after PTX.DATA SOURCES: PubMed, Google Scholar, SCOPUS, Web of Science, and the Cochrane Library.STUDY SELECTION: Eligible studies included reports of PWV in patients with mild pHPT and controls, or in patients with mild pHPT before and after PTX.DATA EXTRACTION: Two investigators independently identified eligible studies and extracted data. Pooled mean difference (MD) was the summary effect measure. Data were presented in forest plots with outlier and influential case diagnostics.DATA SYNTHESIS: Nine observational studies and one RCT were selected, including 433 patients with mild pHPT, 171 of whom underwent PTX, and 407 controls. PWV was significantly higher in mild pHPT as compared to controls (MD=1.18, 0.67 to 1.68, p<0.0001). Seven studies evaluated the effect of PTX on PWV. PTX significantly reduced PWV (MD= -0.48, -0.88 to -0.07, p=0.022).CONCLUSION: Aortic stiffness is increased in patients with mild pHPT, supporting the notion that also mild pHPT is associated with adverse cardiovascular manifestations. PTX significantly reduced arterial stiffness in mild pHPT, indicating that the benefit of PTX over cardiovascular manifestations should not be dismissed but it deserves further studies
A case report of hyponatremia after surgery for Conn's adenoma
Primary aldosteronism (PA), also known as Conn's syndrome, is a frequent cause of secondary hypertension. If PA is due to a documented unilateral adrenal adenoma, adrenalectomy is the treatment of choice. Endocrine Society guidelines suggest monitoring potassium after adrenalectomy, while there is no mention of sodium disorders after surgery. Here we report the case of a patient with Conn's syndrome who developed hyponatremia after surgery. This was an unexpected event in the course of the treatment, which sheds light on the fact that low levels of aldosterone strongly influence sodium concentration, and advises clinicians to monitor sodium after adrenalectomy
PixFEL: development of an X-ray diffraction imager for future FEL applications
A readout chip for diffraction imaging applications at new generation X-ray FELs (Free Electron
Lasers) has been designed in a 65 nm CMOS technology. It consists of a 32 Ă— 32 matrix, with
square pixels and a pixel pitch of 110 µm. Each cell includes a low-noise charge sensitive amplifier
(CSA) with dynamic signal compression, covering an input dynamic range from 1 to 104 photons
and featuring single photon resolution at small signals at energies from 1 to 10 keV. The CSA
output is processed by a time-variant shaper performing gated integration and correlated double
sampling. Each pixel includes also a small area, low power 10-bit time-interleaved Successive
Approximation Register (SAR) ADC for in-pixel digitization of the amplitude measurement. The
channel can be operated at rates up to 4.5 MHz, to be compliant with the rates foreseen for future
X-ray FEL machines. The ASIC has been designed in order to be bump bonded to a slim/active
edge pixel sensor, in order to build the first demonstrator for the PixFEL (advanced X-ray PIXel
cameras at FELs) imager
Effect of global posture re-education on range of motion, pain and quality of life in adults individuals with chronic lower back pain: a randomized clinical trial
Global Postural Re-Education (RPG®) method, developed by the French physiotherapist Philippe E. Souchard, is based on progressing knowledge of human biomechanics and motor coordination, all applied to postural re-education and neuromusculoskeletal rehabilitation. It requires an active role to the patient can be applied to patients of any age, respecting each person’s capability and is indicated in for people presenting postural ailments and musculoskeletal disorder. In the same way, Mézières Method end point is regain “body harmony”. Raggi® Method and Pancafit ® apply the principles previously theorized and combine them to diaphragmatic breathing. Our asses was to evaluate the effect of muscle chain stretching, as proposed by the global posture reeducation method, in the therapy of patients with chronic lower back pain. Eight patients (6 male and 2 female, aged 52.0 +/- 7.3 years old), performed global posture re-education using Pancafit according Raggi Method, once a week. The treatment program consisted of 1-hour individual sessions per week for eight weeks. Patients were evaluated before and after treatment and tested for Platform Lizard ( Stabilometry and postural assessment), pain intensity (by means of visual analog scale), range of motion (bending test), and health-related quality of life (by the SF-36 questionnaire). Significant pain relief and range of motion improvement were observed after treatment; quality of life also improved. Muscle chain stretching was effective in reducing pain and improving the range of motion and quality of life of patients with chronic lower back pain, suggesting that stretching exercises should be prescribed to chronic back pain patients
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