Using semantic clustering to support situation awareness on Twitter: The case of World Views

In recent years, situation awareness has been recognised as a critical part of effective decision making, in particular for crisis management. One way to extract value and allow for better situation awareness is to develop a system capable of analysing a dataset of multiple posts, and clustering consistent posts into different views or stories (or, world views). However, this can be challenging as it requires an understanding of the data, including determining what is consistent data, and what data corroborates other data. Attempting to address these problems, this article proposes Subject-Verb-Object Semantic Suffix Tree Clustering (SVOSSTC) and a system to support it, with a special focus on Twitter content. The novelty and value of SVOSSTC is its emphasis on utilising the Subject-Verb-Object (SVO) typology in order to construct semantically consistent world views, in which individuals---particularly those involved in crisis response---might achieve an enhanced picture of a situation from social media data. To evaluate our system and its ability to provide enhanced situation awareness, we tested it against existing approaches, including human data analysis, using a variety of real-world scenarios. The results indicated a noteworthy degree of evidence (e.g., in cluster granularity and meaningfulness) to affirm the suitability and rigour of our approach. Moreover, these results highlight this article's proposals as innovative and practical system contributions to the research field

The overall model of ecological assessment of vehicles

W pracy zbudowano model do oceny samochodu pod względem powodowanych zagrożeń środowiska naturalnego z uwzględnieniem wszystkich etapów funkcjonowania: produkcji, użytkowania i recyklingu. Celem jest poszukiwanie samochodu, którym przejechanie jednego kilometra powoduje najmniejsze skutki dla środowiska. Przedstawiono porównanie różnych pojazdów pod względem ich wpływu na środowisko.In this thesis, was built a model to assess vehicle in terms of caused risks of natural environment, including all stages of the functioning: production, use and recycling. The objective is to search the car, where the passing of one kilometer causes the smallest impacts on the environment. It was presented a comparison of different vehicles in terms of their impact on the environment

Modelowanie dynamiki maszyn z zastosowaniem metody elementów skończonych

Metoda elementów skończonych posiada wiele zalet, dzięki którym jest powszechnie stosowana w problemach dynamiki maszyn. Przede wszystkim umożliwia obliczanie dużych układów. W wielu przypadkach dużych obiektów, takich jak: nadwozia samochodów, kadłuby lotnicze i okrętowe jest jedyną metodą umożliwiającą tego rodzaju analizy. Ważną zaletą MES jest fakt, że warunki brzegowe są opisane równaniami algebraicznymi, a nie różniczkowymi, co znacznie upraszcza opis. Ważna jest także możliwość wprowadzenia w jednym systemie różnych obciążeń, np. mechanicznych i cieplnych oraz uwzględnienie różnych właściwości materiałów: lepkosprężystych, plastycznych, analiza struktur kompozytowych. Początkiem analizy dynamiki jest rozwiązanie zagadnienia własnego - wyznaczenie częstości i pstaci drgań. Drugim podstawowym zadaniem jest numeryczne rozwiązywanie równań ruchu

Rozpraszanie energii w tłumiku elastomerowo-ciernym w warunkach ujemnych temperatur

The impact of sub-zero temperatures on energy dissipation levels is very essential in Polish climatic conditions. Experimental research results (made on shimmy self-oscillation damper used in a landing gear of a small plane) show that energy dissipation level of an elastomeric friction damper (in opposition to hydraulic) is decreasing with dropping temperature. This situation is a result of significant differences in thermal expansion of materials, especially the specific elastomer feature – large thermal expansion (elastomer have thermal expansion about 50 times larger than steel). Simulation of damper work, using Finite Element Method, confirmed those dependencies. An estimation of the friction coefficient has been made between the elastomer and aluminium surface. It has been ascertained that those values are relatively small, from 0.13 initial moment declining to 0.085 then rising to 0.256.Problem wpływu ujemnych temperatur na zmienność poziomu rozpraszania energii w polskich warunkach klimatycznych ma ważne znaczenie. Przedstawione w pracy wyniki badań doświadczalnych (wykonane na przykładzie tłumika drgań samowzbudnych typu shimmy w podwoziu małego samolotu) pokazują, że tłumiki elastomerowo-cierne (w przeciwieństwie do hydraulicznych) charakteryzują się obniżaniem poziomu rozpraszania energii z spadkiem temperatury. Przyczyny takiej sytuacji wynikają ze znacznych różnic rozszerzalności cieplnej materiałów, w szczególności specyficznych cech elastomerów, istotna jest duża (około pięćdziesięciokrotnie większa od stali) rozszerzalność cieplna elastomerów. Symulacja działania tłumika wykonana Metodą Elementów Skończonych potwierdziła te zależności. Wykonano również oszacowanie wartości współczynnika tarcia pomiędzy elastomerem a ścianą wykonaną z aluminium - stwierdzono, że są to względnie małe wartości od 0,13 w chwili początkowej spadające do wartości 0,085 i następnie rosnące z prędkością do 0,256

Selected problems concerning the analysis of thin-walled structures with the use of finite element method

The aim of the paper was presentation and comparison of numerical methods applied in thin-walled structures analysis, with special attention paid to possibility of usage the Finite Element Method (FEM), especially in nonlinear analysis. There were presented basic differences between classical approach to modelling and analyzing thin-walled structures, and these performed with FEM methods using. The biggest emphasis was placed on the analysis of semimonocoąues, in which the loss in the shell 's stability is possible in the range of operational load activity. According to this, many nonlinear terms like global and local buckling, contact problems, significant deformations and shifts, are present. Worth emphasizing is the fact, that tension field, is something that was described long time ago. First paper s about this phenomenon were published in the last century. Although it is a common effect that takes place in semimonocoques, there are not many publications that analyze and examine this phenomenon. In this paper, an analysis of two-sided, thin-walled spar, which has undergone the flexion by the shearing force in the plane of the panel, was presented. The spar was designed as a classic semimonocoque, in which load transmission function is separated. It was assumed that, for the sake of small thickness, shell elements transmit mainly tangential loads, normal loads, when normal loads are transmitted by framework elements. Riveted joints are used to join elements of framework and shell. There are presented and compared results of analysis for models with various complexities. Firstly, results of analysis of classical model of semimonocoques were presented. It means that framework elements were modelled as rod elements transmitted only normal loads, but shell elements were modelled as disc semimonocoque elements, in this case transmitted only tangential loads. Area of section of rod elements was adequately increased, in order to consideration mating width, coming from partial transmission of normal loads by the shell elements. Results obtained for intermediate models were also presented, as well as for complex shell model, which allows on advanced nonlinear analysis of tension field, which consider contact between framework and shell elements. Applications of formulated models to thin-walled structure, especially aircraft ones and further possibilities of presented method of analysis were discussed

Laminated Windshield Breakage Modelling in the Context of Headform Impact Homologation Tests

The purpose of modelling a laminated windshield using the FEM is to provide a critical look on the way the adult headform impact tests are conducted in the process of motor vehicle certification. The main aim of the study is to modify the design of a laminated windshield in the context of a vehicle collision with vulnerable road users. The initial phase of the work was to develop a model of the adult headform impactor. The validation consisted in conducting a series of FEM analyses of the impactor certification testing according to the Regulation (EC) 631/2009. Next, the impact of the headform model on a windshield was analysed. The FEM model of laminated glass is composed of two outer layers of glass and an inner layer of polyvinyl butyral. FEM analyses of the impaction were performed at five points of the windshield characterised by various dynamic responses of the impactor and various patterns of glass cracking. In modelling the layers of glass, the Abaqus environment “brittle cracking” model was used. The following material models of PVB resin were considered: elastic, elastic-plastic, hyperelastic, and low-density foam. Furthermore, the influence of the mesh type on the process of glass cracking in a laminated windshield was analysed

Numerical investigations on vibrating motion with inertial load of vibratory pile hammer stiffly coupled with excavator

A vibratory pile hammer (VPH) is a mechanical device used to drive steel piles as well as tube piles into soil to provide foundation support for buildings or other structures. In order to increase the stability and the efficiency of the VPH work in the over-resonance frequency, a new VPH construction was developed in the Military University of Technology. The new VPH contains a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. This system is suspended in the static parts by the adaptive variable stiffness pillows based on a smart material, magnetorheological elastomer (MRE), which rheological and mechanical properties can be reversibly and rapidly controlled by an external magnetic field. The work presented in the paper is a part of the modified VPH construction design process. It concerns the development of the numerical model of the VPH and soil interaction that will describe resonance conditions, resonance frequencies with consideration of soil susceptibility, coupling phenomenon and elastomer changeable stiffness. On the base of developed theoretical equations, the frequency of VPH piling will be regulated to assure the over-resonance work