Stage IV Emission Standards for Tractor Engines

Cílem mé bakalářské práce je objasnění principu funkce systému vstřikování močoviny a jeho instalace na vozidlo. V první části své práce se zabývám problematikou snižování škodlivin ve výfukových plynech a emisními normami, které limitují škodliviny ve výfukových plynech. Ve druhé části je vytvořen přehled značek traktorů na našem trhu a jejich rozdělení podle použitých systémů ke snižování škodlivin ve výfukových plynech u jejich modelových řad.The aim of this bachelor thesis is to explain the mechanism of injection of carbamide and its installation on a vehicle. The first part of this work deals with the reduction of pollutants in the exhaust gases and with the emissions standards which limit the level of pollutants in the exhaust gases. The second part consists of an overview of tractor brands available at Czech market and their classification based on the type of system they use on their new models to reduce the pollutants in the exhaust gases.

Hygro-mechanical model for concrete pavement with long-term drying analysis

Concrete pavements are subjected to the combination of moisture transport, heat transport and traffic loading. A hygro-mechanical 3D finite element model was created in OOFEM software in order to analyse the stress field and deformed shape from a long-term non-uniform drying. The model uses a staggered approach, solving moisture transfer weakly coupled with MPS viscoelastic model for ageing concrete creep and shrinkage. Moisture transport and mechanical sub-models are calibrated with lab experiments, long-term monitoring on D1 highway and data from 40 year old highway pavement. The slab geometry is 3.5×5.0×0.29 m, resting on elastic Winkler-Pasternak foundation. The validation covers autogenous and drying strain on the slab. The models predict drying-induced tensile stress up to 3.3 MPa, inducing additional loading on the slab, uncaptured by current design methods

THERMO-MECHANICAL MODEL FOR CONCRETE PAVEMENT

This paper describes a numerical thermo-mechanical model for concrete pavement, implemented in OOFEM software. The thermal part is a heat transfer problem with appropriate initial and boundary conditions (sun irradiation, radiation and convection), calibrated from experimental data. Heat release from cement hydration is also included, calibrated for commonly used cements to demonstrate the difference that can be achieved with the binder selection. The mechanical part of the problem is composed of a 3D elastic concrete slab, subsoil Winkler-Pasternak elements and 1D interface elements, allowing separation in tension. The Winkler-Pasternak constants C1 and C2 were firstly determined from TP170 document and refined later from static load tests on the highway. The model validates well temperature field, static load test and provide several useful insight such as feasible time for summer casting, stress/strain fields and slab separation from the base

Centrifugal motor brake for pneumatic compactor

Cílem mé diplomové práce je návrh odstředivé brzdy pro zabránění přetočení spalovacího motoru u pneumatikového válce. V první části své diplomové práce se zabývám stávajícími a obdobnými systémy bránícími přetočení motorů. Ve druhé části práce se zabývám vlastním návrhem odstředivé brzdy. Ten zahrnuje základní funkční, pevnostní, tepelný výpočet, návrh jednotlivých komponent a zhotovení výkresové dokumentace dle zadání.The aim of my thesis is the design of centrifugal brakes to prevent twisting of the combustion engine with pneumatic compactor. In the first part of my thesis I deal with existing and similar systems that prevent over speeding. In the second part I deal with the design of its own centrifugal brake. This includes basic functional, strength, thermal calculation, design of components and fabrication drawings according to the assignment.

Optimality problems in Orlicz spaces

In mathematical modelling, the data and solutions are represented as measurable functions and their quality is oftentimes captured by the membership to a certain function space. One of the core questions for an analysis of a model is the mutual relationship between the data and solution quality. The optimality of the obtained results deserves a special focus. It requires a careful choice of families of function spaces balancing between their expressivity, i.e. the ability to capture fine properties of the model, and their accessibility, i.e. its technical difficulty for practical use. This paper presents a unified and general approach to optimality problems in Orlicz spaces. Orlicz spaces are parametrized by a single convex function and neatly balance the expressivity and accessibility. We prove a general principle that yields an easily verifiable necessary and sufficient condition for the existence or the non-existence of an optimal Orlicz space in various tasks. We demonstrate its use in specific problems, including the continuity of Sobolev embeddings and boundedness of integral operators such as the Hardy--Littlewood maximal operator and the Laplace transform

The Hierarchy of Hereditary Sorting Operators

We consider the following general model of a sorting procedure: we fix a hereditary permutation class $\mathcal{C}$, which corresponds to the operations that the procedure is allowed to perform in a single step. The input of sorting is a permutation $\pi$ of the set $[n]=\{1,2,\dotsc,n\}$, i.e., a sequence where each element of $[n]$ appears once. In every step, the sorting procedure picks a permutation $\sigma$ of length $n$ from $\mathcal{C}$, and rearranges the current permutation of numbers by composing it with $\sigma$. The goal is to transform the input $\pi$ into the sorted sequence $1,2,\dotsc,n$ in as few steps as possible. This model of sorting captures not only classical sorting algorithms, like insertion sort or bubble sort, but also sorting by series of devices, like stacks or parallel queues, as well as sorting by block operations commonly considered, e.g., in the context of genome rearrangement. Our goal is to describe the possible asymptotic behavior of the worst-case number of steps needed when sorting with a hereditary permutation class. As the main result, we show that any hereditary permutation class $\mathcal{C}$ falls into one of five distinct categories. Disregarding the classes that cannot sort all permutations, the number of steps needed to sort any permutation of $[n]$ with $\mathcal{C}$ is either $\Theta(n^2)$, a function between $O(n)$ and $\Omega(\sqrt{n})$, a function betwee $O(\log^2 n)$ and $\Omega(\log n), or$1$, and for each of these cases we provide a structural characterization of the corresponding hereditary classes

Steel elements with timber fire protection - experiment and numerical analysis

Steel structural elements are sensitive to elevated temperatures, while timber elements have good thermal insulation properties. Timber material can fulfill the role of fire protection of steel members. The effect of the protection is demonstrated on an experiment with three beams with different levels of the protection, placed into a horizontal furnace. The experimental task was also numerically analysed with standard computational approach given by the Eurocode [1, 2], which leads to an interesting comparison, as the calculation is supposed to provide higher temperatures and larger deformations compared to the experimental data

Utjecaj izvedbe lista kružne pile na sile pri poprečnom piljenju drva

This paper evaluates the impact of the number of saw blade teeth on kinematic and dynamic parameters during cross-cutting of soft and hard woods with mitre saw BOSCH GCM 12 GLD Professional. The forces measured using a three-dimensional XYZ dynamometer Kistler 9257B and subsequent calculation based on a mathematical model were applied in the Ernst-Merchant diagram and the forces acting in the cutting of spruce and oak planks were analysed and compared. The wood cutting was performed by four geometrically and structurally similar blades with a 300 mm diameter and with different count of WZ-shaped teeth (z = 26, 36, 48, 60). The optimum saw blade for the given cutting conditions was subsequently assessed by statistical analysis. Unlike many studies researching the cutting resistances in transversal and longitudinal wood cutting, this experiment and force analysis was performed in dependence on the constant feed force.U ovom se radu ispituje utjecaj broja zubi lista pile na kinematičke i dinamičke parametre tijekom poprečnog rezanja mekih i tvrdih vrsta drva poprečnom klatnom pilom BOSCH GCM 12 GLD Professional. Vrijednosti sila izmjerene spomoću trodimenzionalnog XYZ dinamometra Kistler 9257B te vrijednosti naknadnih izračuna primjenom matematičkog modela uvrštene su u Ernst-Merchantov dijagram te je napravljena analiza i usporedba sila pri piljenju smrekovih i hrastovih piljenica. Uzorci drva piljeni su s četiri geometrijski i strukturno slična lista pile promjera 300 mm s različitim brojem zubi tipa WZ (z = 26, 36, 48, 60). Statističkom analizom određen je optimalan list pile za zadane uvjete piljenja. Za razliku od mnogih istraživanja u kojima su proučavani otpori pri poprečnome i uzdužnom piljenju drva, ovo istraživanje i analiza sila provedeni su pri konstantnoj posmičnoj sili