Exploiting technological synergies for future launch vehicles

Two launch vehicle concepts based on technologies available today or in a short term future in Western Europe are presented. The design of both launchers has the goal of exploiting synergies with current European programs to limit development and operational costs. Technologies of particular interest here are the high performance solid rocket motors with carbon-epoxy filament wound monolithic motor cases and the future high performance cryogenic expander cycle engine Vinci. The first concept dubbed ANGELA (A New GEneration LAuncher) is a study financed with funds of the German Ministry of Economics and managed by the DLR Space Administration. The project, which started in the summer of 2012 aims at designing a low cost versatile launcher able to place payloads between 2 and 5 tons into GTO. Three architectures have been considered during the first phase of the study. This phase was concluded in March 2013 with the preliminary stagings, which will be the starting point of more detailed analyses. The first architecture is made out of an H110 (stage with 110 tons of LOx/LH2) equipped with two Vulcain 2 engines with shortened nozzles and an H29 propelled by a Vinci engine. In addition the variation of the number of P36 solid rocket boosters allow to reach the entire range of payload performance. The second architecture differs from the first one only by the use of a new staged-combustion engine instead of two Vulcain 2 engines. The new engine, which should deliver 1800 kN in vacuum, allows a reduction of the size of the stages to H90-H24, enhanced with P34 boosters. The third and last architecture is a so called Multi PPH. The first stage is a bundle of 2 or 3 P120 solid rocket motors. The second stage is made out of one single P120, strictly similar to those used for the first stage. Finally the upper stage is an H23 equipped with a Vinci engine, the same as the two other architectures. The second launcher concept described in this paper is the small TSTO launch vehicle. It consists of a large solid rocket motor first stage P175 and a cryogenic upper stage propelled by the Vinci engine, H26. The preliminary design performed at DLR-SART considers two target performances. The light version of the small TSTO shall perform Galileo satellite replacement single launch missions to MTO corresponding to a payload performance of about 1400 kg in GTO. A heavy version of the launch vehicle shall be able to launch payloads up to 3000 kg in GTO. The performance increase for the heavy version is made possible by the addition of two pairs of P23 boosters, the second pair being ignited with a delay

Simple and efficient four-cycle counting on sparse graphs

We consider the problem of counting 4-cycles ($C_4$) in a general undirected graph $G$ of $n$ vertices and $m$ edges (in bipartite graphs, 4-cycles are also often referred to as $\textit{butterflies}$). There have been a number of previous algorithms for this problem; some of these are based on fast matrix multiplication, which is attractive theoretically but not practical, and some of these are based on randomized hash tables. We develop a new simpler algorithm for counting $C_4$ requiring $O(m\bar\delta(G))$ time and $O(n)$ space, where $\bar \delta(G) \leq O(\sqrt{m})$ is the $\textit{average degeneracy}$ parameter introduced by Burkhardt, Faber & Harris (2020). It has several practical improvements over previous algorithms; for example, it is fully deterministic, does not require any sorting of the adjacency list of the input graph, and avoids any expensive arithmetic in its inner loops. To the best of our knowledge, all previous efficient algorithms for $C_4$ counting have required $\Omega(m)$ space. The algorithm can also be adapted to count 4-cycles incident to each vertex and edge

A Linear Time Algorithm for Finding Minimum Spanning Tree Replacement Edges

Given an undirected, weighted graph, the minimum spanning tree (MST) is a tree that connects all of the vertices of the graph with minimum sum of edge weights. In real world applications, network designers often seek to quickly find a replacement edge for each edge in the MST. For example, when a traffic accident closes a road in a transportation network, or a line goes down in a communication network, the replacement edge may reconnect the MST at lowest cost. In the paper, we consider the case of finding the lowest cost replacement edge for each edge of the MST. A previous algorithm by Tarjan takes $O(m \alpha(m, n))$ time, where $\alpha(m, n)$ is the inverse Ackermann's function. Given the MST and sorted non-tree edges, our algorithm is the first that runs in $O(m+n)$ time and $O(m+n)$ space to find all replacement edges. Moreover, it is easy to implement and our experimental study demonstrates fast performance on several types of graphs. Additionally, since the most vital edge is the tree edge whose removal causes the highest cost, our algorithm finds it in linear time

Bounds and algorithms for graph trusses

The $k$-truss, introduced by Cohen (2005), is a graph where every edge is incident to at least $k$ triangles. This is a relaxation of the clique. It has proved to be a useful tool in identifying cohesive subnetworks in a variety of real-world graphs. Despite its simplicity and its utility, the combinatorial and algorithmic aspects of trusses have not been thoroughly explored. We provide nearly-tight bounds on the edge counts of $k$-trusses. We also give two improved algorithms for finding trusses in large-scale graphs. First, we present a simplified and faster algorithm, based on approach discussed in Wang & Cheng (2012). Second, we present a theoretical algorithm based on fast matrix multiplication; this converts a triangle-generation algorithm of Bjorklund et al. (2014) into a dynamic data structure

Furniture Mover

The movement of furniture is an often overlooked pain point for physically-challenged individuals, especially when rearranging furniture in a room. These individuals may try to minimize the risk of tip-over or strain-related injuries by seeking assistance from others. Still, some individuals are limited in finding volunteers forthcoming and capable of helping. This can lead to a dilemma of either being able to find individuals willing to assist in the process or risking one’s own personal safety when moving furniture. The proposed design project implements the use of multiple, independent platforms with mecanum wheels placed underneath each corner of a piece of furniture by a user. These devices will work together to move furniture based on commands from a wireless device, allowing for the adjustment of furniture with more flexible positioning and will negate the requirement of human force, preventing physical strain on one\u27s body

KINETIC AND KINEMATIC ANALYSIS OF THE BACKSTROKE START

Race start technique in competitive swimming has developed considerably in recent years and is thought to be an important factor governing the outcome of a race. The purpose of this study was to measure the reliability of a new analysis system for swimming (PAS-S), as well as to analyse the backstroke start kinetics and kinematics and to compare the normal backstroke start with the backstroke start with a new start device. 16 high level competitive swimmers were examined in this study, which revealed that the measurements with the PAS-S are reliable. The analysis of the backstroke start showed the importance of a high preload force just before the start signal. Furthermore, if available, swimmers should use the new backstroke start device since the 15 m times were significantly faster even without considerable training with the new start device

KINETIC AND KINEMATIC ANALYSIS OF THE LEG POSITIONING IN THE FREESTYLE TRACK START IN SWIMMING

In swimming competitions, the track start is an important part of the race. The aim of this study was to assess and compare the relative positioning of the dominant leg in the preferential freestyle track start. The data was collected using the (Kistler) Performance Analysis System for Swimming (PAS-S) that includes a force measurement and motion analysis system. The results taken from 15 high level competitive swimmers showed that 67.7 % of the subjects naturally position their dominant leg in front. Starting with the dominant leg in front (6.67±0.24) was significantly (p < 0.001) faster than in the rear position (7.25±0.23). However swimmers had faster starts when using their preferential track start. Detailed analysis of the swimming start and the footedness allows coaches and athletes to train the fastest starting technique

Twelve months effect on voiding function of retropubic compared with outside-in and inside-out transobturator midurethral slings

Introduction and hypothesis: The purpose of this study is to compare retropubic tension-free vaginal tape (TVT) with transobturator out-in TOT and in-out TVT-O for female stress urinary incontinence. Uroflow rate was primary; continence rates, quality of life (QoL) and complication pattern were secondary endpoints. Methods: A prospective randomised trial with 2:1:1 randomisation at two Swiss teaching hospitals. Patients were followed up at 12months. Results: Eighty TVT, 40 transobturator tape (TOT) and 40 TVT-O were randomised. At 12months, there was no difference in Qmax among the groups. Continence was comparable (≥89%). QoL was improved significantly in all groups (P < 0.05). Five vaginal tape exposures occurred (one TVT, four TOT, zero TVT-O; P = 0.028). Two percent (1/52) of sexually active patients after TVT, 17% (5/29) after TOT, but 0% (0/25) after TVT-O reported de novo female sexual dysfunction (P = 0.011). We considered this clinically important enough to stop enrolment. Conclusions: There was no difference for Qmax at 12months between TVT, TOT and TVT-O. Female sexual dysfunction and tape exposure may be higher with a transobturator tap

Patient satisfaction after retropubic and transobturator slings: first assessment using the Incontinence Outcome Questionnaire (IOQ)

Introduction and hypothesis: The aim of the Incontinence Outcome Questionnaire (IOQ) is to assess quality of life and patient-reported outcome after midurethral slings. Methods: In this retrospective study, 626 patients with a minimum follow-up period of 1year were sent the IOQ. Four hundred twenty-two of 626 (67.4%) patient responses were evaluated. Results: The mean IOQ QoL extended score was 33.7 ± 17.5 and comparable for tension-free vaginal tape (TVT), outside-in transobturator tape (TOT), and inside-out transobturator vaginal tape (TVT-O). Evaluation of IOQ question about readmission revealed a total of 32 patients (18 TVT, 12 TOT, and 2 TVT-O) who underwent a subsequent operation due to sling-related complications. Freedom from reoperation for recurrent SUI at 1, 2, and 5years was 100%, 99.7 ± 0.3%, and 99.7 ± 0.3% for TVT, 100% for TVT-O, and 94.2 ± 2.5%, 91.9 ± 2.9%, and 89.9 ± 3.5% for TOT, respectively (p < 0.001). Conclusions: Patient satisfaction, assessed using the IOQ, is high after retropubic and transobturator slings. In our collective, relapse incontinence is higher after TO

Competition-Based Success Factors During the Talent Pathway of Elite Male Swimmers

Marginal differences in race results between top swimmers have evoked the interest in competition-based success factors of long-term athlete development. To identify novel factors for the multi-dimensional model of talent development, the aim of the study was to investigate annual variation in competition performance (ACV), number of races per year, and age. Therefore, 45,398 race results of all male participants (n = 353) competing in individual events, i.e., butterfly, backstroke, breaststroke, freestyle, and individual medley, at the 2018 European Long-Course Swimming Championships (2018EC) were analyzed retrospectively for all 10 years prior to the championships with Pearson's correlation coefficient and multiple linear regression analysis. Higher ranked swimmers at the 2018EC showed significant medium correlations with a greater number of races per year and small but significant correlations with higher ACV in 10 and nine consecutive years, respectively, prior to the championships. Additionally, better swimmers were older than their lower ranked peers (r = −0.21, p < 0.001). Regression model explained a significant proportion of 2018EC ranking for 50 m (47%), 100 m (45%), 200 m (31%), and 400 m races (29%) but not for 800 and 1,500 m races with number of races having the largest effect followed by age and ACV. In conclusion, higher performance variation with results off the personal best in some races did not impair success at the season's main event and young competitors at international championships may benefit from success chances that increase with age. The higher number of races swum per year throughout the career of higher ranked swimmers may have provided learning opportunities and specific adaptations. Future studies should quantify these success factors in a multi-dimensional talent development model