986 resultados para Three-level AC-DC Converter


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UNLABELLED: The relationship between bone quantitative ultrasound (QUS) and fracture risk was estimated in an individual level data meta-analysis of 9 prospective studies of 46,124 individuals and 3018 incident fractures. Low QUS is associated with an increase in fracture risk, including hip fracture. The association with osteoporotic fracture decreases with time. INTRODUCTION: The aim of this meta-analysis was to investigate the association between parameters of QUS and risk of fracture. METHODS: In an individual-level analysis, we studied participants in nine prospective cohorts from Asia, Europe and North America. Heel broadband ultrasonic attenuation (BUA dB/MHz) and speed of sound (SOS m/s) were measured at baseline. Fractures during follow-up were collected by self-report and in some cohorts confirmed by radiography. An extension of Poisson regression was used to examine the gradient of risk (GR, hazard ratio per 1 SD decrease) between QUS and fracture risk adjusted for age and time since baseline in each cohort. Interactions between QUS and age and time since baseline were explored. RESULTS: Baseline measurements were available in 46,124 men and women, mean age 70 years (range 20-100). Three thousand and eighteen osteoporotic fractures (787 hip fractures) occurred during follow-up of 214,000 person-years. The summary GR for osteoporotic fracture was similar for both BUA (1.45, 95 % confidence intervals (CI) 1.40-1.51) and SOS (1.42, 95 % CI 1.36-1.47). For hip fracture, the respective GRs were 1.69 (95 % CI, 1.56-1.82) and 1.60 (95 % CI, 1.48-1.72). However, the GR was significantly higher for both fracture outcomes at lower baseline BUA and SOS (p < 0.001). The predictive value of QUS was the same for men and women and for all ages (p > 0.20), but the predictive value of both BUA and SOS for osteoporotic fracture decreased with time (p = 0.018 and p = 0.010, respectively). For example, the GR of BUA for osteoporotic fracture, adjusted for age, was 1.51 (95 % CI 1.42-1.61) at 1 year after baseline, but at 5 years, it was 1.36 (95 % CI 1.27-1.46). CONCLUSIONS: Our results confirm that quantitative ultrasound is an independent predictor of fracture for men and women particularly at low QUS values.

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Background: The public health burden of coronary artery disease (CAD) is important. Perfusion cardiac magnetic resonance (CMR) is generally accepted to detect and monitor CAD. Few studies have so far addressed its costs and costeffectiveness. Objectives: To compare in a large CMR registry the costs of a CMR-guided strategy vs two hypothetical invasive strategies for the diagnosis and the treatment of patients with suspected CAD. Methods: In 3'647 patients with suspected CAD included prospectively in the EuroCMR Registry (59 centers; 18 countries) costs were calculated for diagnostic examinations, revascularizations as well as for complication management over a 1-year follow-up. Patients with ischemia-positive CMR underwent an invasive X-ray coronary angiography (CXA) and revascularization at the discretion of the treating physician (=CMR+CXA strategy). Ischemia was found in 20.9% of patients and 17.4% of them were revascularized. In ischemia-negative patients by CMR, cardiac death and non-fatal myocardial infarctions occurred in 0.38%/y. In a hypothetical invasive arm the costs were calculated for an initial CXA followed by FFR testing in vessels with ≥50% diameter stenoses (=CXA+FFR strategy). To model this hypothetical arm, the same proportion of ischemic patients and outcome was assumed as for the CMR+CXA strategy. The coronary stenosis - FFR relationship reported in the literature was used to derive the proportion of patients with ≥50% diameter stenoses (Psten) in the study cohort. The costs of a CXA-only strategy were also calculated. Calculations were performed from a third payer perspective for the German, UK, Swiss, and US healthcare systems.

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The thesis is made of three independent chapters interested in the impact of globalization on workers in industrialized countries. The dissertation is especially focused on identifying the causal impact of international trade on workers' mobility, wages, and employment with both a short- and medium-term perspective. The first paper explores the relation between intra-industry trade (IIT) expansion and associated worker flows, taking the latter as an indicator of labor-market adjustment costs. Being the first study to combine theoretical simulations and a novel identification strategy, we find that both theoretical and empirical analyses are consistent with the "smooth adjustment hypothesis", according to which IIT expansion is less disruptive than inter-industry trade expansion. The study therefore lends support to the use of IIT indices as first-pass proxies for the adjustment effects of trade expansion. The second chapter contrasts the impact of increased import competition coming from China and the European Union (EU) on workers in the United Kingdom over a 15-year period. The most salient findings show that increased imports from China had significantly negative effects on workers' earnings, wages and employment. In contrast, larger imports from the EU are associated with positive worker-level outcomes, which is largely explained by the fact that increased imports from the EU were mostly offset by increased same-industry exports to the EU. Besides, we find that increased imports from China exert additional pressure on workers through spillovers to employment and wages in downstream industries. Finally, the last chapter is focused on the impact of exposure to trade and real exchange rate shocks on wages for Swiss manufacturing workers. A particular attention is made to consistently estimate the causal effect in using a two-step gravity-type identification strategy. The study shows that the impact of trade and exchange rate movements is concentrated among high-skilled workers almost exclusively.

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Internationalization and the following rapid growth have created the need to concentrate the IT systems of many small-to-medium-sized production companies. Enterprise Resource Planning systems are a common solution for such companies. Deployment of these ERP systems consists of many steps, one of which is the implementation of the same shared system at all international subsidiaries. This is also one of the most important steps in the internationalization strategy of the company from the IT point of view. The mechanical process of creating the required connections for the off-shore sites is the easiest and most well-documented step along the way, but the actual value of the system, once operational, is perceived in its operational reliability. The operational reliability of an ERP system is a combination of many factors. These factors vary from hardware- and connectivity-related issues to administrative tasks and communication between decentralized administrative units and sites. To accurately analyze the operational reliability of such system, one must take into consideration the full functionality of the system. This includes not only the mechanical and systematic processes but also the users and their administration. All operational reliability in an international environment relies heavily on hardware and telecommunication adequacy so it is imperative to have resources dimensioned with regard to planned usage. Still with poorly maintained communication/administration schemes no amount of bandwidth or memory will be enough to maintain a productive level of reliability. This thesis work analyzes the implementation of a shared ERP system to an international subsidiary of a Finnish production company. The system is Microsoft Dynamics Ax, currently being introduced to a Slovakian facility, a subsidiary of Peikko Finland Oy. The primary task is to create a feasible base of analysis against which the operational reliability of the system can be evaluated precisely. With a solid analysis the aim is to give recommendations on how future implementations are to be managed.

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Abstract Objective: To determine whether low-level laser therapy can prevent salivary hypofunction after radiotherapy and chemotherapy in head and neck cancer patients. Materials and Methods: We evaluated 23 head and neck cancer patients, of whom 13 received laser therapy and 10 received clinical care only. An InGaAlP laser was used intra-orally (at 660 nm and 40 mW) at a mean dose of 10.0 J/cm2 and extra-orally (at 780 nm and 15 mW) at a mean dose of 3.7 J/cm2, three times per week, on alternate days. Stimulated and unstimulated sialometry tests were performed before the first radiotherapy and chemotherapy sessions (N0) and at 30 days after the end of treatment (N30). Results: At N30, the mean salivary flow rates were significantly higher among the laser therapy patients than among the patients who received clinical care only, in the stimulated and unstimulated sialometry tests (p = 0.0131 and p = 0.0143, respectively). Conclusion: Low-level laser therapy, administered concomitantly with radiotherapy and chemotherapy, appears to mitigate treatment-induced salivary hypofunction in patients with head and neck cancer.

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In this work AC magnetometer was developed and primary test measurements were performed for temperature range from 77 K up to 350 K in frequency range from 1 kHz up to 20 kHz. In the course of the present work dependencies of magnetization on temperature for Lao7Sr03Mni _yFeyO3 with y = 0.15, 0.20, 0.25 were obtained in DC magnetic field using SQUID magnetometer and in AC magnetic field using the developed AC magnetometer. Lai.XSrXMnO3 (LSMO) compounds belong to the class of Mn perovskites, which demonstrate very high degree of spin polarization. These materials are of great importance for nowadays applications in spintronics, where spin polarized electron transport is used. Spin glass like behavior was found as a characteristic feature of these solid solutions with the freezing temperature in the range 65 — 210 K.

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Data transmission between an electric motor and a frequency converter is required in variablespeed electric drives because of sensors installed at the motor. Sensor information can be used for various useful applications to improve the system reliability and its properties. Traditionally, the communication medium is implemented by an additional cabling. However, the costs of the traditional method may be an obstacle to the wider application of data transmission between a motor and a frequency converter. In any case, a power cable is always installed between a motor and a frequency converter for power supply, and hence it may be applied as a communication medium for sensor level data. This thesis considers power line communication (PLC) in inverter-fed motor power cables. The motor cable is studied as a communication channel in the frequency band of 100 kHz−30 MHz. The communication channel and noise characteristics are described. All the individual components included in a variable-speed electric drive are presented in detail. A channel model is developed, and it is verified by measurements. A theoretical channel information capacity analysis is carried out to estimate the opportunities of a communication medium. Suitable communication and forward error correction (FEC) methods are suggested. A general method to implement a broadband and Ethernet-based communication medium between a motor and a frequency converter is proposed. A coupling interface is also developed that allows to install the communication device safely to a three-phase inverter-fed motor power cable. Practical tests are carried out, and the results are analyzed. Possible applications for the proposed method are presented. A speed feedback motor control application is verified in detail by simulations and laboratory tests because of restrictions for the delay in the feedback loop caused by PLC. Other possible applications are discussed at a more general level.

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Long-term relative sea-level cycles (0 5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault-controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea-level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea-level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea-level drop was in the order of tens of metres, with a duration of <1 Myr. The second stage of relative sea-level fall occurred within the Late Aptian and is recorded by an incised valley that, when restored to its pre-contractional attitude, was >2 km wide and cut 115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was back-filled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea-level drops identified fall within the glacio-eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long-term sea-level trends that are often only recognizable on larger scales (i.e. seismic) such as for the Arabian Plate.

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Long-term relative sea-level cycles (0 5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault-controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea-level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea-level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea-level drop was in the order of tens of metres, with a duration of <1 Myr. The second stage of relative sea-level fall occurred within the Late Aptian and is recorded by an incised valley that, when restored to its pre-contractional attitude, was >2 km wide and cut 115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was back-filled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea-level drops identified fall within the glacio-eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long-term sea-level trends that are often only recognizable on larger scales (i.e. seismic) such as for the Arabian Plate.

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This thesis deals with distance transforms which are a fundamental issue in image processing and computer vision. In this thesis, two new distance transforms for gray level images are presented. As a new application for distance transforms, they are applied to gray level image compression. The new distance transforms are both new extensions of the well known distance transform algorithm developed by Rosenfeld, Pfaltz and Lay. With some modification their algorithm which calculates a distance transform on binary images with a chosen kernel has been made to calculate a chessboard like distance transform with integer numbers (DTOCS) and a real value distance transform (EDTOCS) on gray level images. Both distance transforms, the DTOCS and EDTOCS, require only two passes over the graylevel image and are extremely simple to implement. Only two image buffers are needed: The original gray level image and the binary image which defines the region(s) of calculation. No other image buffers are needed even if more than one iteration round is performed. For large neighborhoods and complicated images the two pass distance algorithm has to be applied to the image more than once, typically 3 10 times. Different types of kernels can be adopted. It is important to notice that no other existing transform calculates the same kind of distance map as the DTOCS. All the other gray weighted distance function, GRAYMAT etc. algorithms find the minimum path joining two points by the smallest sum of gray levels or weighting the distance values directly by the gray levels in some manner. The DTOCS does not weight them that way. The DTOCS gives a weighted version of the chessboard distance map. The weights are not constant, but gray value differences of the original image. The difference between the DTOCS map and other distance transforms for gray level images is shown. The difference between the DTOCS and EDTOCS is that the EDTOCS calculates these gray level differences in a different way. It propagates local Euclidean distances inside a kernel. Analytical derivations of some results concerning the DTOCS and the EDTOCS are presented. Commonly distance transforms are used for feature extraction in pattern recognition and learning. Their use in image compression is very rare. This thesis introduces a new application area for distance transforms. Three new image compression algorithms based on the DTOCS and one based on the EDTOCS are presented. Control points, i.e. points that are considered fundamental for the reconstruction of the image, are selected from the gray level image using the DTOCS and the EDTOCS. The first group of methods select the maximas of the distance image to new control points and the second group of methods compare the DTOCS distance to binary image chessboard distance. The effect of applying threshold masks of different sizes along the threshold boundaries is studied. The time complexity of the compression algorithms is analyzed both analytically and experimentally. It is shown that the time complexity of the algorithms is independent of the number of control points, i.e. the compression ratio. Also a new morphological image decompression scheme is presented, the 8 kernels' method. Several decompressed images are presented. The best results are obtained using the Delaunay triangulation. The obtained image quality equals that of the DCT images with a 4 x 4

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In this work magnetic properties of ZnGeP2:Mn were investigated in DC magnetic field with SQUID magnetometer in the temperature range from 3 K up to 400 K and in AC magnetic field with AC magnetometer in the temperature range from 77 K up to 350 K in frequency range from 500 Hz up to 18 KHz. Three ZnGeP2:Mn samples were studied with Mn concentration c = 1.5 % mass, 3 % mass and 3.5 % mass.

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Technical analysis of Low Voltage Direct Current (LVDC) distribution systems shows that in LVDC transmission the customer voltage quality is higher. One of the problems in LVDC distribution networks that converters both ends of the DC line are required. Because of the converters produce not pure DC voltage, but some fluctuations as well, the huge electrolytic capacitors are required to reduce voltage distortions in the DC-side. This thesis master’s thesis is focused on calculating required DC-link capacitance for LVDC transmission and estimation of the influence of different parameters on the voltage quality. The goal is to investigate the methods of the DC-link capacitance estimation and location in the transmission line.

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Understanding how marine predators interact is a scientific challenge. In marine ecosystems, segregation in feeding habits has been largely described as a common mechanism to allow the coexistence of several competing marine predators. However, little is known about the feeding ecology of most species of chondrichthyans, which play a pivotal role in the structure of marine food webs worldwide. In this study, we examined the trophic ecology of 3 relatively abundant chondrichthyans coexisting in the Mediterranean Sea: the blackmouth catshark Galeus melastomus , the velvet belly lanternshark Etmopterus spinax and the rabbit fish Chimaera monstrosa. To examine their trophic ecology and interspecific differences in food habits, we combined the analysis of stomach content and stable isotopes. Our results highlighted a trophic segregation between C. monstrosa and the other 2 species. G. melastomus showed a diet composed mainly of cephalopods, while E. spinax preyed mainly on shrimps and C. monstrosa on crabs. Interspecific differences in the trophic niche were likely due to different feeding capabilities and body size. Each species showed different isotopic niche space and trophic level. Specifically, C. monstrosa showed a higher trophic level than E. spinax and G. melastomus. The high trophic levels of the 3 species highlighted their important role as predators in the marine food web. Our results illustrate the utility of using complementary approaches that provide information about the feeding behaviour at short (stomach content) and long-term scales (stable isotopes), which could allow more efficient monitoring of marine food-web changes in the study area.

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The research around performance measurement and management has focused mainly on the design, implementation and use of performance measurement systems. However, there is little evidence about the actual impacts of performance measurement on the different levels of business and operations of organisations, as well as the underlying factors that lead to a positive impact of performance measurement. The study thus focuses on this research gap, which can be considered both important and challenging to cover. The first objective of the study was to examine the impacts of performance measurement on different aspects of management, leadership and the quality of working life, after which the factors that facilitate and improve performance and performance measurement at the operative level of an organisation were examined. The second objective was to study how these factors operate in practice. The third objective focused on the construction of a framework for successful operative level performance measurement and the utilisation of the factors in the organisations. The research objectives have been studied through six research papers utilising empirical data from three separate studies, including two sets of interview data and one of quantitative data. The study applies mainly the hermeneutical research approach. As a contribution of the study, a framework for successful operative level performance measurement was formed by matching the findings of the current study and performance measurement theory. The study extents the prior research regarding the impacts of performance measurement and the factors that have a positive effect on operative level performance and performance measurement. The results indicate that under suitable circumstances, performance measurement has positive impacts on different aspects of management, leadership, and the quality of working life. The results reveal that for example the perception of the employees and the management of the impacts of performance measurement on leadership style differ considerably. Furthermore, the fragmented literature has been reorganised into six factors that facilitate and improve the performance of the operations and employees, and the use of performance measurement at the operative level of an organisation. Regarding the managerial implications of the study, managers who operate around performance measurement can utilise the framework for example by putting the different phases of the framework into practice.

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This research studied children who had been diagnosed with Multisystem Developmental Disorder (MSDD) (NC, 2002) under the Diagnostic Classifications of Mental Health and Developmental Disorders of Infancy and Early Childhood (DC: 0 - 3). They all showed, to a varying degree, difficulties in relating to others, play, affective interaction and severe delay in developing communication skills. Some studies have observed continuity in the diagnosis of autism during the first years of life. The objective of this study is to analyse the development of infants with MSDD whose diagnosis of autism was not confirmed. We also attempted to verify any possible psychomotor developmental differences based on, or related to, the severity and typology (B and C) of the MSDD. To enable us to do this we carried out a 3-year follow-up during which we assessed the infants (n = 15) and their parents. They are 2 - 4 years old. Results showed that type B children did present a greater impairment of psychomotor development in assessment tests. However, we did not observe any correlation between the degree of severity of the initial symptoms and later diagnoses. Conclusion: although our sample is small, we can conclude that there isn’t a clear evolution in the diagnosis, but we have found significant differences in the symptomatology between the type B and C