Die vorliegende Arbeit befasst sich mit der Methode der modalen Superposition als Ordnungsreduktionsverfahren in der Mikrosystemtechnik. Typische Anwendungsgebiete sind Inertialsensoren und dabei im Besonderen Drehratensensoren, für die die Simulation von zeitabhängigen Phänomenen von entscheidender Bedeutung ist. Im Rahmen der Weiterentwicklung der Ordnungsreduktion nach der Methode der modalen Superposition ist es gelungen für typische lineare Kräfte eine auf analytischen Gleichungen basierende Beschreibung im reduzierten Raum zu finden. Für die Beschreibung von nichtlinearen Kräften ist im Rahmen dieser Arbeit ein Verfahren entwickelt worden, das es erlaubt, bestehende Modelle im Finite-Elemente-Raum in der modalen Beschreibung zu nutzen. In dieser Arbeit werden die theoretischen Grundlagen zur Berücksichtigung von Einflüssen der Aufbau- und Verbindungstechnik in ordnungsreduzierten Modellen dargestellt. Neben der Einkopplung äußerer Kräfte und der Veränderung der mechanischen Randbedingungen wird auch der Einfluss der Aufbau- und Verbindungstechnik auf die elektrostatischen Eigenschaften untersucht. Die Parametrisierung des Verfahrens der modalen Superposition über Fit- und Interpolationsverfahren erlaubt es, parametrisierte ordnungsreduzierte Modelle für die zeitabhängige Systemsimulation zu generieren. Damit wird die Durchführung von Designoptimierung und die Berücksichtigung von Fertigungs- und Prozessschwankungen in ordnungsreduzierten Modellen auf Systemebene möglich.

This work presents a fracture mechanics analysis of the cathodic delamination problem for the polyurethane/titanium and polyurea/steel interfaces. The nonlinear behavior of both polymers was investigated. The recent Marlow model was used to define the strain energy function of the polymers. Viscoelastic effects of the polyurea were also studied. The Marlow model was associated with a nine-term Prony series. This model was seen to represent experimental data relatively well for a wide range of strain rates both in tension and compression. The driving force for delamination, the strain energy release rate G, is presented for both interfaces. Cathodic delamination data for several temperatures are presented as crack growth rate as a function of crack driving force. The approach recognizes that both temperature and stress can be used as accelerated life testing parameters. / text

Bien que les méthodes de calcul peuvent donner de bons résultats, ils ne sont généralement pas en accord avec exactement les données d'essais en vol en raison des incertitudes dans les modelé de calcul de structure et aérodynamiques. Une méthode efficace est nécessaire pour la mise à jour des modelé aeroelastiques en utilisant les données d'essais en vol, les données d'essais de vibration au sol ( GVT ) et les données de soufflerie. Tout d'abord tous les développements ont été valides sur une section de l'aile 2D et sur un modèle 3D simple et après l'approche POD a été applique= a une configuration industrielle (modèle de soufflerie aile-fuselage et modèle d' avions complète). / Although computational methods can provide good results, they usually do not agree exactly with the flight test data due to uncertainties in structural and aerodynamic computational models. An effective method is required for updating computational aeroelastic models using the flight test data along with Ground Vibration Test (GVT) data and wind tunnel data. Firstly all developments have been validated on a 2D wing section and on a simple 3D model and after the POD approach has been applied to an industrial configuration (wing-fuselage wind tunnel model and complete aircraft model).

Für die elastische Mehrkörpersimulation bzw. die FEM-MKS-Kopplung sind reduzierte FE-Modelle von großer Bedeutung. Die Erstellung reduzierter Modelle mit hoher Abbildungsgüte im Rahmen einer Modellordnungsreduktion erfordert einerseits ein geeignetes Reduktions-verfahren und andererseits zuverlässige Korrelationsmethoden. Beides wird durch die Soft-ware MORPACK bereitgestellt. Die Korrelation reduzierter FE-Modelle basiert in MORPACK derzeit ausschließlich auf modalen Eigenschaften. Ausgehend von der Annahme, dass sich die Abbildungsgüte eines reduzierten FE-Modells erst im Rahmen einer Zeitbereichssimula-tion vollständig beurteilen lässt, ist eine dahingehende Erweiterung von MORPACK geplant. Für einfache Topologien muss die Möglichkeit bestehen, das dynamische Verhalten, redu-zierter Modelle, direkt in MORPACK zu simulieren. Mit Hilfe der resultierenden Zeitsignale werden die reduzierten Modelle bewertet. Für die Umsetzung dieser Idee muss in MORPACK zunächst ein eigenständiges EMKS-Programm implementiert werden. Die Implementierung des EMKS-Programms in MORPACK (bzw. MATLAB) stellt den Schwerpunkt dieser Arbeit dar. Es werden zunächst die Anforderungen an das EMKS-Programm formuliert. Nach der Behandlung aller erforderlichen theoretischen Grundlagen werden die Systemgleichungen hergeleitet. Anschließend wird ein Formalismus bereitgestellt, der den Aufbau der Systemgleichungen, auf Basis der Nutzereingaben ermöglicht. Nach der Implementierung des Formalismus wird das EMKS-Programm verifiziert und erprobt. / Reduced FE-Models are very important for elastic multibody simulation and FEM-MKS-coupling. The generation of reduced FE-models with high approximation quality in a model order reduction requires on the one hand a suitable reduction method and on the other hand reliable correlation methods. Both are provided by the MORPACK software. In MORPACK the correlation of reduced FE models based currently only on modal properties. An extension of the MORPACK software is planned on the assumption, that the approximation quality of a reduced FE-model can be completely assessed only in a time domain simulation. For simple topologies, it must be possible to simulate the dynamic behavior of reduced models directly into MORPACK. With the correlation of resulting time signals, the reduced models are as-sessed. To realize this idea, an independent EMKS program must be implemented in MORPACK. The implementation of the EMKS program in MORPACK (respectively MATLAB) represents the focus of this thesis. The first part is to formulate the necessary requirements for the EMKS program. After handling of all the necessary theoretical foundations, the system equa-tions are derived. Subsequently, formalism is provided that allows a construction of the sys-tem equations based on the user input. After the implementation of the formalism, the EMKS program will verify and tested.

Rice and maize are global staple food and play an important role in world’s food security strategy. Vietnam is one of rice leading export countries but annually it has to import a considerate amount of maize for cattle food processing. Red River Delta in the north of Vietnam is the second rice bucket of the country, which is responsible formore than 20% of total rice production. The priority crops in the areas are rice and maize and rice-maize system is the leading cropping system in the area. Currently, it is reported that the rice-maize cropping system is not sustainable and its profit is reducing in most of production areas in the Red River Delta. Improving rice cropping system aims is not only to increase rice and maize yields and production but also to improve the land use efficiency, decline the cost of the production and to increase system sustainability. To increase sustainability there must be a linkage of various factors. This review emphasizes on increasing rice-maize crop sustainability by applying appropriate agriculture practices such as reducing chemical fertilization and intensive tillage. / Gạo và ngô là nguồn lương thực chính cho toàn cầu và đóng một vai trò quan trọng trong chiến lược an ninh lương thực của thế giới. Việt Nam là một trong những nước dẫn đầu về xuất khẩu gạo nhưng hàng năm vẫn phải nhập một số lượng lớn ngô để chế biến thức ăn gia súc. Đồng bằng sông Hồng là một trong hai vựa lúa lớn của Việt Nam sản xuất khoảng 20% sản lượng lúa gạo của cả nước. Ở đồng bằng sông Hồng, lúa và ngô là hai cây trồng chính là hệ canh tác lúa-ngô là cơ cấu cây trồng hàng đầu trong vùng. Tuy nhiên, trong những năm gần đây, rất nhiều đánh giá cho thấy hệ thống canh tác lúa-ngô là hệ thống canh tác không bền vững và các lợi nhuận của mang lại từ cơ cấu canh tác ở hầu hết các khu vực sản xuất ở vùng đồng bằng sông Hồng của Việt Nam đã và đang giảm dần. Do đó, việc cải thiện cơ cấu canh tác lúa-ngô không chỉ nhằm mục đích tăng năng suất lúa và ngô mà còn nâng cao hiệu quả sử dụng đất, giảm chi phí sản xuất và tăng cường hệ thống canh tác bền vững. Tuy nhiên, để tăng tính bền vững của hệ thống canh tác thì phải liên kết nhiều yếu tố khác nhau. Bài viết này dựa vào các kết quả nghiên cứu của các tác giả khác nhau để đưa ra những giải pháp tích cực làm tăng tính bền vững của hệ thống canh tác lúa-ngô bằng cách áp dụng các phương pháp canh tác hợp lý như giảm sử dụng phân hóa học và các biện pháp canh tác thâm canh như áp dụng phương pháp làm đất tối thiểu.

During the period 1996–2005, experiments were carried out at the Joniškėlis Research Station of the Lithuanian Institute of Agriculture on an Endocalcari-Endohypogleyic Cambisol. The experiment was set up in 1956 in the ten - field crop rotation: 1) mixture of vetch and oat, 2) winter wheat, 3) spring barley, 4) fodder beet, 5)spring barley with under sowing, 6) 1-st year perennial grasses (red clover and timothy), 7) 2-nd year perennial grasses, 8) winter wheat, 9) fodder beet, 10) spring barley. Scheme of the soil tillage: 1) Conventional soil tillage with ploughing 22-25 cm, 2) permanent shallow ploughing 12-15 cm, 3) soil tillage with an inconstant ploughing depth: 25 cm in fallow, 20 cm after perennial grasses, 15 cm after spring barley, 10 cm after fodder beet, 20-25 cm after winter wheat, 4) soil ploughing depth according to necessity, 5) deep loosening with chisel cultivator PČ-2,5 25 cm. The aim of this investigation was to evaluate the influence of conventional and permanent shallow soil tillage, its alternation, and no-shell board deep loosening on humous, soil physical properties, the productivity of crop rotation and energy efficiency. During the fifth crop rotation, conventional soil tillage alternated with permanent shallow soil tillage or with deep loosening with an inconstant ploughing depth according to necessity had no significantly influence on soil humous. The most increase (0,19 percentage units) of soil humous was determined in soil tillage with an... [to full text]

En 1940, Paul Erdős énonça une conjecture sur la distribution des classes inversibles modulo un entier. La présente thèse étudie la distribution des k-uplets de classes inversibles propose une preuve de la conjecture d'Erdős étendue au cas des k-uplets. / In 1940 Paul Erdos made a conjecture about the distribution of reduced residues. Here, in this thesis we studied the distribution of k-tuples of reduced residues, and proved extension of Erdos's conjecture for them.

In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.

The impact of different agricultural systems used in agriculture on the leaching of nutrients and nitrates first of all depends on many factors that are not noticed and sometimes even underestimated by farmers trying to reach larger yields and better economic results. This article analysis the issue of changes in water regime and nitrate nitrogen leaching under the change of agricultural systems; such issue has not been investigated in Lithuania before. This research is especially relevant under the conditions of the Middle Lithuanian Lowland, where annual crops (cereals and sugar beet) area mainly cultivated, the ground is aerated in-tensely thus increasing the mineralization of organic substances and a lot of fertilizers are used. The change of conventional tillage for reduced tillage resulted in the decrease of the resources of surface soil water by 4,91-5,85 % and after changing it into no-tillage water resources decreased by 23,4 %. Reduced tillage and late ploughing are appropriate environmental means reducing nitrate nitrogen leaching from soil. / Įvairių žemdirbystės sistemų naudojamų žemės ūkyje poveikis maisto medžiagų ir labiausiai nitratų išsiplovimui priklauso nuo daugelio veiksnių, kurių žemdirbiai siekdami didesnių derlių ir geresnių ekonominių rezultatų nepastebi, o kartais ir reikiamai neįvertina. Šiame darbe, nagrinėjamas šalyje netirtas vandens režimo ir nitratų azoto išplovimo pasikeitimų, keičiantis žemdirbystės sistemoms, klausimas. Šie tyrimai ypač aktualūs Lietuvos Vidurio lygumos sąlygomis, kur daugiausia auginama vienmečių augalų (javų ir cukrinių runkelių), kasmet žemė intensyviai aeruojama, taip didinant organinių medžiagų mineralizaciją, naudojama daug trąšų. Pakeitus tradicinį žemės dirbimą į sumažintą žemės dirbimą paviršinio dirvožemio sluoksnio vandens atsargos sumažėjo 4,91-5,85 %, o pakeitus į neariminį žemės dirbimą vandens atsargos sumažėjo 23,4 %. Sumažintas žemės dirbimas bei vėlyvas arimas yra tinkamos aplinkosauginės priemonės, mažinančios nitratų azoto išplovimą iš dirvožemio.

In this thesis, the properties of the Bose-Einstein condensation (BEC) in low dimensions are reviewed. Three dimensional weakly interacting Bose systems are examined by the variational method. The effects of both the attractive and the repulsive interatomic forces are studied. Thomas-Fermi approximation is applied to find the ground state energy and the chemical potential. The occurrence of the BEC in low dimensional systems, is studied for ideal gases confined by both harmonic and power-law potentials. The properties of BEC in highly anisotropic trap are investigated and the conditions for reduced dimensionality are derived.