936 resultados para active and reactive power sharing
Resumo:
BACKGROUND: Previous studies on childhood cancer and nuclear power plants (NPPs) produced conflicting results. We used a cohort approach to examine whether residence near NPPs was associated with leukaemia or any childhood cancer in Switzerland. METHODS: We computed person-years at risk for children aged 0-15 years born in Switzerland from 1985 to 2009, based on the Swiss censuses 1990 and 2000 and identified cancer cases from the Swiss Childhood Cancer Registry. We geo-coded place of residence at birth and calculated incidence rate ratios (IRRs) with 95% confidence intervals (CIs) comparing the risk of cancer in children born <5 km, 5-10 km and 10-15 km from the nearest NPP with children born >15 km away, using Poisson regression models. RESULTS: We included 2925 children diagnosed with cancer during 21 117 524 person-years of follow-up; 953 (32.6%) had leukaemia. Eight and 12 children diagnosed with leukaemia at ages 0-4 and 0-15 years, and 18 and 31 children diagnosed with any cancer were born <5 km from a NPP. Compared with children born >15 km away, the IRRs (95% CI) for leukaemia in 0-4 and 0-15 year olds were 1.20 (0.60-2.41) and 1.05 (0.60-1.86), respectively. For any cancer, corresponding IRRs were 0.97 (0.61-1.54) and 0.89 (0.63-1.27). There was no evidence of a dose-response relationship with distance (P > 0.30). Results were similar for residence at diagnosis and at birth, and when adjusted for potential confounders. Results from sensitivity analyses were consistent with main results. CONCLUSIONS: This nationwide cohort study found little evidence of an association between residence near NPPs and the risk of leukaemia or any childhood cancer.
Resumo:
A mathematical model of the voltage drop which arises in on-chip power distribution networks is used to compare the maximum voltage drop in the case of different geometric arrangements of the pads supplying power to the chip. These include the square or Manhattan power pad arrangement, which currently predominates, as well as equilateral triangular and hexagonal arrangements. In agreement with the findings in the literature and with physical and SPICE models, the equilateral triangular power pad arrangement is found to minimize the maximum voltage drop. This headline finding is a consequence of relatively simple formulas for the voltage drop, with explicit error bounds, which are established using complex analysis techniques, and elliptic functions in particular.
Resumo:
Tässä työssä raportoidaan harjoitustyön kehittäminen ja toteuttaminen Aktiivisen- ja robottinäön kurssille. Harjoitustyössä suunnitellaan ja toteutetaan järjestelmä joka liikuttaa kappaleita robottikäsivarrella kolmiuloitteisessa avaruudessa. Kappaleidenpaikkojen määrittämiseen järjestelmä käyttää digitaalisia kuvia. Tässä työssä esiteltävässä harjoitustyötoteutuksessa käytettiin raja-arvoistusta HSV-väriavaruudessa kappaleiden segmentointiin kuvasta niiden värien perusteella. Segmentoinnin tuloksena saatavaa binäärikuvaa suodatettiin mediaanisuotimella kuvan häiriöiden poistamiseksi. Kappaleen paikkabinäärikuvassa määritettiin nimeämällä yhtenäisiä pikseliryhmiä yhtenäisen alueen nimeämismenetelmällä. Kappaleen paikaksi määritettiin suurimman nimetyn pikseliryhmän paikka. Kappaleiden paikat kuvassa yhdistettiin kolmiuloitteisiin koordinaatteihin kalibroidun kameran avulla. Järjestelmä liikutti kappaleita niiden arvioitujen kolmiuloitteisten paikkojen perusteella.
Dial M for Murder: A Case of Passion Killing, Criminal Evidence and Sultanic Power in Medieval India
Resumo:
This paper considers the structures and applications of the criminal judicial system in the Islamic Later Middle Period as it developed in India under the sultans of Delhi (1200-1400 CE). A fundamental issue in crime and punishment is the relationship between sultanic power and religious authority. Particularly at stake in this relationship is the question of who can sanction the highest form of punishment, i.e. the death penalty (siyāsa). Contemporary historians and scholars in the study of religion investigating the relationship between sharīʿa and siyāsa to reveal the extent and limits of sultanic power show a system of governance that allowed for the delegation of authority, particularly in the area of the judiciary, from the sultan down to viziers and judges. Some scholars depict the relationship between the ʿulamāʾ and the sultan as a kind of stand off. The actual dynamics of legal jurisdiction were much more complex. This study proposes a new interpretive framework for understanding the relationship between political power and religious authority through a critical analysis of the criminal judicial system, law, and historical narrative. In particular, I consider a murder case described by Shams al-dīn Sirāj ʿAfīf in one of the most significant histories written in the later Delhi Sultanate, the Tārīkh-i Fīrūzshāhī.
Resumo:
A mathematical model of the voltage drop which arises in on-chip power distribution networks is used to compare the maximum voltage drop in the case of different geometric arrangements of the pads supplying power to the chip. These include the square or Manhattan power pad arrangement, which currently predominates, as well as equilateral triangular and hexagonal arrangements. In agreement with the findings in the literature and with physical and SPICE models, the equilateral triangular power pad arrangement is found to minimize the maximum voltage drop. This headline finding is a consequence of relatively simple formulas for the voltage drop, with explicit error bounds, which are established using complex analysis techniques, and elliptic functions in particular.
Resumo:
In the last few years, the Ukrainian investment market has constantly shown strong performance and significant growth. This is primarily due to the investment attractiveness of Ukraine. From the perspective of investments in energy sector, Ukraine can be described as a country providing significant number of opportunities to multiply invested funds. But there are numbers of risks which hamper large investments. The work objective was to discover opportunities in small-scale hydropower and wind power sectors of Ukraine and more importantly to prove economic expediency of such investments. Thesis covers major of issues, concerning entering the Ukrainian power market as a foreign investor. It provides basic information about the structure of power market, the state of renewables sector in Ukraine, development of power sector in the regions, functioning of Wholesale Electricity Market, formation of electricity prices, possibilities for implementing joint Implementation mechanism, while the most attention, nevertheless, is concentrated on the opportunities in small-scale hydro and wind power sectors. Theoretical part of the study disclosed that Crimea peninsula has perfect wind conditions and could be a prospective area for wind project development. Investment analysis revealed that project profits will be excellent if green tariff for renewable energy is adopted. By the moment uncertainties about green law adoption bring additional risk to the projects and complicate any investment decision.
On the development of an unstructured grid solver for inert and reactive high speed flow simulations
Resumo:
An unstructured grid Euler solver for reactive compressible flow applications is presented. The method is implemented in a cell centered, finite volume context for unstructured triangular grids. Three different schemes for spatial discretization are implemented and analyzed. Time march is implemented in a time-split fashion with independent integrators for the flow and chemistry equations. The capability implemented is tested for inert flows in a hypersonic inlet and for inert and reactive supersonic flows over a 2-D wedge. The results of the different schemes are compared with each other and with independent calculations using a structured grid code. The strengths and the possible weaknesses of the proposed methods are discussed.
Resumo:
At present, permanent magnet synchronous generators (PMSGs) are of great interest. Since they do not have electrical excitation losses, the highly efficient, lightweight and compact PMSGs equipped with damper windings work perfectly when connected to a network. However, in island operation, the generator (or parallel generators) alone is responsible for the building up of the network and maintaining its voltage and reactive power level. Thus, in island operation, a PMSG faces very tight constraints, which are difficult to meet, because the flux produced by the permanent magnets (PMs) is constant and the voltage of the generator cannot be controlled. Traditional electrically excited synchronous generators (EESGs) can easily meet these constraints, because the field winding current is controllable. The main drawback of the conventional EESG is the relatively high excitation loss. This doctoral thesis presents a study of an alternative solution termed as a hybrid excitation synchronous generator (HESG). HESGs are a special class of electrical machines, where the total rotor current linkage is produced by the simultaneous action of two different excitation sources: the electrical and permanent magnet (PM) excitation. An overview of the existing HESGs is given. Several HESGs are introduced and compared with the conventional EESG from technical and economic points of view. In the study, the armature-reaction-compensated permanent magnet synchronous generator with alternated current linkages (ARC-PMSG with ACL) showed a better performance than the other options. Therefore, this machine type is studied in more detail. An electromagnetic design and a thermal analysis are presented. To verify the operation principle and the electromagnetic design, a down-sized prototype of 69 kVA apparent power was built. The experimental results are demonstrated and compared with the predicted ones. A prerequisite for an ARC-PMSG with ACL is an even number of pole pairs (p = 2, 4, 6, …) in the machine. Naturally, the HESG technology is not limited to even-pole-pair machines. However, the analysis of machines with p = 3, 5, 7, … becomes more complicated, especially if analytical tools are used, and is outside the scope of this thesis. The contribution of this study is to propose a solution where an ARC-PMSG replaces an EESG in electrical power generation while meeting all the requirements set for generators given for instance by ship classification societies, particularly as regards island operation. The maximum power level when applying the technology studied here is mainly limited by the economy of the machine. The larger the machine is, the smaller is the efficiency benefit. However, it seems that machines up to ten megawatts of power could benefit from the technology. However, in low-power applications, for instance in the 500 kW range, the efficiency increase can be significant.
Resumo:
SStrong evidence suggests that the climate is changing and that these changes are largely caused by human activities. A consensus exists among researchers that human activity is causing global warming and that actions to mitigate global warming need to be taken swiftly. The transportation sector, which relies heavily on fossil fuel burning and primarily oil, is one of the big contributors to air pollution problems at local, regional and global levels. It is the fastest growing source of greenhouse gas emissions and is estimated to be responsible for nearly a quarter of global energyrelated carbon dioxide emissions. Car sharing is a mobility solution encouraging its users to decrease private car usage in favour of communal transit and environmental goals. The idea of car sharing originates from the aspiration to decrease personal car ownership and to reduce vehicle distance travelled. This thesis seeks to complement the understanding of Finnish car sharing users and their usage through better categorization. Through better categorization and segmentation of Finnish car sharing users the thesis seeks to provide information for improved marketing insight. Research is done on the demographic and behavioural characteristics of Finnish car sharing users and they are compared with international findings about the characteristics of International car sharing users. The main research problem is Are Finnish car sharing users similar to international ones? A theoretical research framework on the determinants of individual car sharing usage is built based on international research about demographic and behaviouristic characteristics. After this a quantitative survey is performed to the customers of a Finnish car sharing organization. The data analysed in the thesis consist out of 532 answers received from the car sharing organizations customers. The data is analysed with descriptive and other exploratory methods, which create an understanding of Finnish car sharing users. At the end of the analysis the demographic and behavioural characteristics of Finnish car sharing users are compared with international ones. The research findings of the thesis indicate that the demographic and behavioural characteristics of Finnish car sharing usage largely follow those of their international counterparts. Thanks to the thesis results the car sharing organization is able to better target their customers through improved marketing insight.
Resumo:
Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the human central nervous system. Although its etiology is unknown, the accumulation and activation of mononuclear cells in the central nervous system are crucial to its pathogenesis. Chemokines have been proposed to play a major role in the recruitment and activation of leukocytes in inflammatory sites. They are divided into subfamilies on the basis of the location of conserved cysteine residues. We determined the levels of some CC and CXC chemokines in the cerebrospinal fluid (CSF) of 23 relapsing-remitting MS patients under interferon-ß-1a therapy and 16 control subjects using ELISA. MS patients were categorized as having active or stable disease. CXCL10 was significantly increased in the CSF of active MS patients (mean ± SEM, 369.5 ± 69.3 pg/mL) when compared with controls (178.5 ± 29.1 pg/mL, P < 0.05). CSF levels of CCL2 were significantly lower in active MS (144.7 ± 14.4 pg/mL) than in controls (237.1 ± 16.4 pg/mL, P < 0.01). There was no difference in the concentration of CCL2 and CXCL10 between patients with stable MS and controls. CCL5 was not detectable in the CSF of most patients or controls. The qualitative and quantitative differences of chemokines in CSF during relapses of MS suggest that they may be useful as a marker of disease activity and of the mechanisms involved in the pathogenesis of the disease.
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The microenvironment of the tumor plays an important role in facilitating cancer progression and activating dormant cancer cells. Most tumors are infiltrated with inflammatory cells which secrete cytokines such as tumor necrosis factor-a (TNF-a). To evaluate the role of TNF-a in the development of cancer we studied its effects on cell migration with a migration assay. The migrating cell number in TNF-a -treated group is about 2-fold of that of the control group. Accordingly, the expression of E-cadherin was decreased and the expression of vimentin was increased upon TNF-a treatment. These results showed that TNF-a can promote epithelial-mesenchymal transition (EMT) of MCF-7 cells. Further, we found that the expression of Snail, an important transcription factor in EMT, was increased in this process, which is inhibited by the nuclear factor kappa B (NFkB) inhibitor aspirin while not affected by the reactive oxygen species (ROS) scavenger N-acetyl cysteine. Consistently, specific inhibition of NFkB by the mutant IkBa also blocked the TNF-a-induced upregulation of Snail promoter activity. Thus, the activation of NFkB, which causes an increase in the expression of the transcription factor Snail is essential in the TNF-a-induced EMT. ROS caused by TNF-a seemed to play a minor role in the TNF-a-induced EMT of MCF-7 cells, though ROS per se can promote EMT. These findings suggest that different mechanisms might be responsible for TNF-a - and ROS-induced EMT, indicating the need for different strategies for the prevention of tumor metastasis induced by different stimuli.