Modeling the transport phenomena within arterial wall: porous media approach

The transport of macromolecules, such as low-density lipoprotein (LDL), and their accumulation in the layers of the arterial wall play a critical role in the creation and development of atherosclerosis. Atherosclerosis is a disease of large arteries e.g., the aorta, coronary, carotid, and other proximal arteries that involves a distinctive accumulation of LDL and other lipid-bearing materials in the arterial wall. Over time, plaque hardens and narrows the arteries. The flow of oxygen-rich blood to organs and other parts of the body is reduced. This can lead to serious problems, including heart attack, stroke, or even death. It has been proven that the accumulation of macromolecules in the arterial wall depends not only on the ease with which materials enter the wall, but also on the hindrance to the passage of materials out of the wall posed by underlying layers. Therefore, attention was drawn to the fact that the wall structure of large arteries is different than other vessels which are disease-resistant. Atherosclerosis tends to be localized in regions of curvature and branching in arteries where fluid shear stress (shear rate) and other fluid mechanical characteristics deviate from their normal spatial and temporal distribution patterns in straight vessels. On the other hand, the smooth muscle cells (SMCs) residing in the media layer of the arterial wall respond to mechanical stimuli, such as shear stress. Shear stress may affect SMC proliferation and migration from the media layer to intima. This occurs in atherosclerosis and intimal hyperplasia. The study of blood flow and other body fluids and of heat transport through the arterial wall is one of the advanced applications of porous media in recent years. The arterial wall may be modeled in both macroscopic (as a continuous porous medium) and microscopic scales (as a heterogeneous porous medium). In the present study, the governing equations of mass, heat and momentum transport have been solved for different species and interstitial fluid within the arterial wall by means of computational fluid dynamics (CFD). Simulation models are based on the finite element (FE) and finite volume (FV) methods. The wall structure has been modeled by assuming the wall layers as porous media with different properties. In order to study the heat transport through human tissues, the simulations have been carried out for a non-homogeneous model of porous media. The tissue is composed of blood vessels, cells, and an interstitium. The interstitium consists of interstitial fluid and extracellular fibers. Numerical simulations are performed in a two-dimensional (2D) model to realize the effect of the shape and configuration of the discrete phase on the convective and conductive features of heat transfer, e.g. the interstitium of biological tissues. On the other hand, the governing equations of momentum and mass transport have been solved in the heterogeneous porous media model of the media layer, which has a major role in the transport and accumulation of solutes across the arterial wall. The transport of Adenosine 5´-triphosphate (ATP) is simulated across the media layer as a benchmark to observe how SMCs affect on the species mass transport. In addition, the transport of interstitial fluid has been simulated while the deformation of the media layer (due to high blood pressure) and its constituents such as SMCs are also involved in the model. In this context, the effect of pressure variation on shear stress is investigated over SMCs induced by the interstitial flow both in 2D and three-dimensional (3D) geometries for the media layer. The influence of hypertension (high pressure) on the transport of lowdensity lipoprotein (LDL) through deformable arterial wall layers is also studied. This is due to the pressure-driven convective flow across the arterial wall. The intima and media layers are assumed as homogeneous porous media. The results of the present study reveal that ATP concentration over the surface of SMCs and within the bulk of the media layer is significantly dependent on the distribution of cells. Moreover, the shear stress magnitude and distribution over the SMC surface are affected by transmural pressure and the deformation of the media layer of the aorta wall. This work reflects the fact that the second or even subsequent layers of SMCs may bear shear stresses of the same order of magnitude as the first layer does if cells are arranged in an arbitrary manner. This study has brought new insights into the simulation of the arterial wall, as the previous simplifications have been ignored. The configurations of SMCs used here with elliptic cross sections of SMCs closely resemble the physiological conditions of cells. Moreover, the deformation of SMCs with high transmural pressure which follows the media layer compaction has been studied for the first time. On the other hand, results demonstrate that LDL concentration through the intima and media layers changes significantly as wall layers compress with transmural pressure. It was also noticed that the fraction of leaky junctions across the endothelial cells and the area fraction of fenestral pores over the internal elastic lamina affect the LDL distribution dramatically through the thoracic aorta wall. The simulation techniques introduced in this work can also trigger new ideas for simulating porous media involved in any biomedical, biomechanical, chemical, and environmental engineering applications.

Factors of customer project profitability in an engineering industrial enterprise

The purpose of the study is to find factors affecting projects' profitability in project business. The issue is approached from customer profitability and project management point of view. The study has been made for a big Finnish company acting in a global market place. The research method is quantitative. Research hypotheses are based on the literature. The used database is originated from the company's ERP- (enterprise resource planning) and project financial follow-up —system. The findings of the study supported the hypotheses weakly. Obviously profitability fluctuated depending on a customer and a project manager. The reasons could not be justified with the variables used in the research.

DFM/DFMA(A) – analysis and aspects of applying systematic engineering for a microwave testfixture design

In this paper, manufacturability analysis and collection of design aspects is made for a microwave test-fixture. Aspects of applying systematic design for a microwave test-fixture design and manufacturing are also analysed. Special questionnaires for the component and machining are made in order to enable necessary information to ensure DFM(A) – aspects of the component. The aspects of easy manufacturing for machining the microwave test-fixture are collected. Material selection is discussed and manufacturing stages of prototype manufacturing are presented.

Competitive flexibility in systems supplier companies in mechanical engineering industry

Systems suppliers are focal actors in mechanical engineering supply chains, in between general contractors and component suppliers. This research concentrates on the systems suppliers’ competitive flexibility, as a competitive advantage that the systems supplier gains from independence from the competitive forces of the market. The aim is to study the roles that power, dependence relations, social capital, and interorganizational learning have on the competitive flexibility. Research on this particular theme is scarce thus far. The research method applied here is the inductive multiple case study. Interviews from four case companies were used as main source of the qualitative data. The literature review presents previous literature on subcontracting, supply chain flexibility, supply chain relationships, social capital and interorganizational learning. The result of this study are seven propositions and consequently a model on the effects that the dominance of sales of few customers, power of competitors, significance of the manufactured system in the end product, professionalism in procurement and the significance of brand products in the business have on the competitive flexibility. These relationships are moderated by either social capital or interorganizational learning. The main results obtained from this study revolve around social capital and interorganizational learning, which have beneficial effects on systems suppliers’ competitive flexibility, by moderating the effects of other constructs of the model. Further research on this topic should include quantitative research to provide the extent to which the results can be reliably generalized. Also each construct of the model gives possible focus for more thorough research.

An Engineering Solution for using Coarse Meshes in the Simulation of Delamination with Cohesive Zone Models

This paper presents a methodology to determine the parameters used in the simulation of delamination in composite materials using decohesion finite elements. A closed-form expression is developed to define the stiffness of the cohesive layer. A novel procedure that allows the use of coarser meshes of decohesion elements in large-scale computations is proposed. The procedure ensures that the energy dissipated by the fracture process is correctly computed. It is shown that coarse-meshed models defined using the approach proposed here yield the same results as the models with finer meshes normally used in the simulation of fracture processes

Blended learning and student time-use in engineering education

Aiheen laajempi artikkeli on julkaistu konferenssi-CD:llä.

Micro- and nanostructuring of poly(ethylene-2,6-naphthalate) surfaces, for biomedical applications, using polymer replication techniques

Here we investigate the formation of superficial micro- and nanostructures in poly(ethylene-2,6-naphthalate) (PEN), with a view to their use in biomedical device applications, and compare its performance with a polymer commonly used for the fabrication of these devices, poly(methyl methacrylate) (PMMA). The PEN is found to replicate both micro- and nanostructures in its surface, albeit requiring more forceful replication conditions than PMMA, producing a slight increase in surface hydrophilicity. This ability to form micro/nanostructures, allied to biocompatibility and good optical transparency, suggests that PEN could be a useful material for production of, or for incorporation into, transparent devices for biomedical applications. Such devices will be able to be autoclaved, due to the polymer's high temperature stability, and will be useful for applications where forceful experimental conditions are required, due to a superior chemical resistance over PMMA.

Quitosana: biopolímero funcional com potencial industrial biomédico

The importance of chitosan has grown significantly over the last two decades due to its renewable and biodegradable source, and also because of the recent increase in the knowledge of its functionality in the technological and biomedical applications. The present article reviews the biopolymer chitosan and its derivatives as versatile biomaterials for potential drug delivery systems, as well as tissue engineering applications, analgesia and treatment of arthritis.

Project owner’s and outside engineering consultant’s role in power plant implementation projects

The purpose of this study was to investigate the nature of co-operation between a project owner and an outside engineering consultant in combined heat and power plant implementation projects. Moreover, as another focal subject of the study was to familiarize the purchasing behavior of the energy producer and how an outside engineering consultant participated into different stages of the purchasing process. The study was carried out as a multiple case study including altogether six Finnish power plant implementation projects that had been taken into commercial use during 1995 – 2015. By adjusting the findings of empirical interview data and comparing those to the theoretical framework concerning, among others, Finnish energy production, engineering consulting businesses, delivery methods of construction project and finally the purchasing process, it can be concluded that especially in the power plant implementation projects in the past have a great influence to decisions made during the project. The role of the main engineering consultant is to act as an assistant, who helps to achieve the project goals successfully rather than an advisor who only knows how the project should be conducted. At least in these five project cases this was the case, meaning that the final decision power always remaining with project owner.

Engineering of Business Critical Web Applications

Research focus of this thesis is to explore options for building systems for business critical web applications. Business criticality here includes requirements for data protection and system availability. The focus is on open source software. Goals are to identify robust technologies and engineering practices to implement such systems. Research methods include experiments made with sample systems built around chosen software packages that represent certain technologies. The main research focused on finding a good method for database data replication, a key functionality for high-availability, database-driven web applications. Research included also finding engineering best practices from books written by administrators of high traffic web applications. Experiment with database replication showed, that block level synchronous replication offered by DRBD replication software offered considerably more robust data protection and high-availability functionality compared to leading open source database product MySQL, and its built-in asynchronous replication. For master-master database setups, block level replication is more recommended way to build high-availability into the system. Based on thesis research, building high-availability web applications is possible using a combination of open source software and engineering best practices for data protection, availability planning and scaling.

Segmentation of Industrial Customers – Case: Finnish Mechanical Engineering Companies

Segmentointi on perinteisesti ollut erityisesti kuluttajamarkkinoinnin työkalu, mutta siirtymä tuotteista palveluihin on lisännyt segmentointitarvetta myös teollisilla markkinoilla. Tämän tutkimuksen tavoite on löytää selkeästi toisistaan erottuvia asiakasryhmiä suomalaisen liikkeenjohdon konsultointiyritys Synocus Groupin tarjoaman case-materiaalin pohjalta. K-means-klusteroinnin avulla löydetään kolme potentiaalista markkinasegmenttiä perustuen siihen, mitkä tarjoamaelementit 105 valikoitua suomalaisen kone- ja metallituoteteollisuuden asiakasta ovat maininneet tärkeimmiksi. Ensimmäinen klusteri on hintatietoiset asiakkaat, jotka laskevat yksikkökohtaisia hintoja. Toinen klusteri koostuu huolto-orientoituneista asiakkaista, jotka laskevat tuntikustannuksia ja maksimoivat konekannan käyttötunteja. Tälle kohderyhmälle kannattaisi ehkä markkinoida teknisiä palveluja ja huoltosopimuksia. Kolmas klusteri on tuottavuussuuntautuneet asiakkaat, jotka ovat kiinnostuneita suorituskyvyn kehittämisestä ja laskevat tonnikohtaisia kustannuksia. He tavoittelevat alempia kokonaiskustannuksia lisääntyneen suorituskyvyn, pidemmän käyttöiän ja alempien huoltokustannusten kautta.

Utilizing online demand generation in an engineering company

Työn tarkoituksena on selvittää miten sähköistä kysynnän herättämistä voidaan hyödyntää Mantsinen Group Ltd Oy:ssä siten, että sillä pystytään tukemaan myyntiä. Lisäksi sähköisen kysynnän herättämisen tehokkuutta tutkitaan, jotta saadaan selville onko se kannattavaa ja kuinka hyvin se sopii yritykselle. Kysynnän herättämisjärjestelmän käyttö on määritelty kirjallisuuteen perustuen ja sen jälkeen järjestelmän käyttö on aloitettu. Sähköisen kysynnän herättämisen tehokkuus mitataan kolmen kuukauden tarkastelujakson todellisella datalla. Sähköisen kysynnän herättämisen sopivuutta arvioidaan perustuen sen kustannustehokkuuteen ja tuloksiin. Työn tulokset osoittavat, että sähköinen kysynnän herättäminen on kannattavaa ja se sopii yritykselle. Sillä voidaan parhaiten tukea myyntiä järjestelmän tuottaessa laadukkaita myyntimahdollisuuksia tasaisena virtana myynnille. Myös aiemmin manuaalisesti tehtyjä työtehtäviä voidaan automatisoida ja näin vähentää myyjien työtaakkaa.