Boundary-mode operation of the boost converter for thermoelectric generator maximum power tracking

This article has been made available through the Brunel Open Access Publishing Fund.Performance-favourable and noteworthy characteristics of the Boost converter are reported, when the latter operates in Maximum Power Tracking (MPT) mode, while fed from a fixed internal resistance power source specifically a Thermo Electric Generator (TEG). It is found that if the converter is controlled with Pulse Frequency Modulation (PFM), for a specific value of inductance, the inductor current inherently remains on the boundary of continuity for the whole control range, that is under all conditions, resulting in reduced switching losses. Furthermore, MPT is possible without the sampling of any current but only with the sampling of the converter input and output voltages. The above theoretical findings have been verified by an experimental prototype

Improved BPSO for optimal PMU placement

Optimal phasor measurement unit (PMU) placement involves the process of minimizing the number of PMU needed while ensuring entire power system network completely observable. This paper presents the improved binary particle swarm (IBPSO) method that converges faster and also manage to maximize the measurement redundancy compared to the existing BPSO method. This method is applied to IEEE-30 bus system for the case of considering zero-injection bus and its effectiveness is verified by the simulation results done by using MATLAB software

Analytical Estimation of the Electrostatic Field in Cylinder-Plane and Cylinder-Cylinder Electrode Configurations

This work presents analytical formulas for the estimation of the electrostatic field in cylinder-plane and cylinder-cylinder electrode configurations. Assuming a predefined potential difference between the electrodes and given their geometrical characteristics, these could be useful for the solution of numerous problems involving such electrode sets. Moreover, the voltage distribution around the electrodes is defined by providing equations either for the equipotentials at a given voltage ratio, or the exact estimation of the potential at any point in the surrounding space. Simplified expressions for critical engineering parameters such as the peak electric field and the field enhancement factor are also given

‘‘Appearance of Corruption’’: Linking Public Opinion and Campaign Finance Reform

At present, campaign finance regulations may only be justified if their primary purpose is to prevent quid pro quo corruption or the appearance of corruption. References to the ‘‘appearance of corruption’’ are ubiquitous in campaign finance decisions, yet courts have provided very little guidance about what the phrase means. In this article, we report findings from a broadly representative national survey in which we (1) directly ask respondents to identify behaviors that appear politically corrupt, and (2) indirectly measure perceptions of corruption using a novel paired-choice conjoint experiment asking respondents to choose which of two randomly generated candidates are more likely to do something corrupt while in office. Our findings both support and challenge current campaign finance jurisprudence. Our direct item shows that bribery is considered to be the most politically corrupt behavior, while wealthy self-funded candidates are not perceived as corrupting the political system. These findings support the reliance of courts on bribery as the primary justification for campaign finance rules, and the courts’ dismissal of regulations targeting wealthy candidates. However, most of our respondents perceived many common behaviors besides bribery to be ‘‘very corrupt,’’ challenging courts’ reliance on bribery as the sole justification for campaign finance rules. Our conjoint experiment, designed to force trade-offs between various behaviors, similarly reveals little differentiation across candidate campaign finance profiles, suggesting voters may not distinguish common behaviors in terms of their corrupting role. A normatively positive result in our conjoint analysis is that partisans do not appear to define corruptibility on the basis of in-/out-party signals

CAC-TCP cross-layer interaction in a HAPS-satellite integrated scenario

The integration of a satellite system with a HAPS segment appears very suitable to provide communication services, including Internet access, for a large set of applications. In fact, the-satellite capability to provide wide coverage and broadband access can be enhanced by the use of cost-effective, mobile/portable and low-power consuming user terminals, when HAPS acts as an intermediate repeater. Moreover, also TCP-based applications, which suffer from long latency introduced by the satellite link and in general by errors, can get benefits in terms of end-to-end performance. In this frame, this paper deals with the introduction, on board the HAPS, of an efficient CAC scheme in order to guarantee an optimal utilization of the precious radio resources. In particular, we propose an innovative TCP driven CAC algorithm, which shall take into account not only the QoS requirements, but also TCP statistics obtained through a proxy installed on the HAPS. Results show that the overall system performance in terms of both average throughput and blocking probability is significantly improved

Alcian Blue Histological investigation of generated hyaline cartilage tissue from adipose mesenchymal stem cells, on Polycaprolactone scaffolds.

Purpose: Cartilage has a low regenerative capacity and research has recently focused on regenerative medicine and the construction of three-dimensional scaffolds for cartilage production. The aim of the study was to compare three types of polycaprolactone scaffolds (PCLs) and to characterize the produced cells as chondrocytes, using Alcian blue, a widespread histochemical staining. Methods: We manufactured polycaprolactone scaffolds with three different geometry patterns, named PCL1, PCL2 and PCL3. Adipose mesenchymal stem cells ADMSCs were harvested and were cultivated on all scaffolds. After 26 days of culture, scaffolds were histologically examined. Results: Chondrocytes and extracellular material in scaffolds were revealed by alcian blue staining. In all three types of scaffolds extracellular matrix high in proteoglycans was produced. Small cells were usually found in three-dimensional, tight groups. Larger cells were often identified in flat groups with more extracellular material. In PCL2 scaffolds, cells were usually more rounded and often appeared to be inside lacunae. Perichondrium was detected. Conclusion: Chondrogenesis was achieved in all three types of scaffolds. In all cases we identified cells at various stages of maturation. In the PCL2 scaffold, cells appeared more mature, suggesting that this type of scaffold may be a little more favorable for chondrogenesis

Design and investigation of a diesel engine operated on pilot ignited LPG

This thesis explores the idea of igniting LPG in a compression ignition diesel engine using pilot diesel injection as spark ignition medium. The main advancement in using this technology on current diesel engines is the establishment of a better balance between NOx and PM emissions without losing too much of the CO2 benefits of diesel. With the advent of common rail diesel engines, it is now possible to get control of pilot diesel injection and make the LPG and diesel control systems work together. Combined diesel and LPG operation is a new subject for engine research, so the thesis moves on to consider the results from detailed engine simulation studies that explore the potential benefits of the mix. Subsequent simulations of a modern four cylinder dCi engine suggest that with closer control over the pilot diesel injection, diesel like performance can be obtained, hopefully with less emissions than currently expected from diesel only operation. A single cylinder variable compression ratio research engine was developed to explore diesel /LPG dual fuel operation. A second generation common rail injection rig was also developed for the engine and for fuel spray characterisation. Engine experiments proved the concept of using a modest charge of pilot injected diesel for igniting a larger dose of port injected LPG. The experimental work results suggest that combining diesel common rail injection technology with the state of the art LPG injection systems, it is possible to establish a better balance between NOx/ PM emissions without losing too much of the CO2 benefits from the diesel operation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Application of the Gaussian mixture model in pulsar astronomy -- pulsar classification and candidates ranking for {\it Fermi} 2FGL catalog

Machine learning, algorithms to extract empirical knowledge from data, can be used to classify data, which is one of the most common tasks in observational astronomy. In this paper, we focus on Bayesian data classification algorithms using the Gaussian mixture model and show two applications in pulsar astronomy. After reviewing the Gaussian mixture model and the related Expectation-Maximization algorithm, we present a data classification method using the Neyman-Pearson test. To demonstrate the method, we apply the algorithm to two classification problems. Firstly, it is applied to the well known period-period derivative diagram, where we find that the pulsar distribution can be modeled with six Gaussian clusters, with two clusters for millisecond pulsars (recycled pulsars) and the rest for normal pulsars. From this distribution, we derive an empirical definition for millisecond pulsars as $\frac{\dot{P}}{10^{-17}} \leq3.23(\frac{P}{100 \textrm{ms}})^{-2.34}$. The two millisecond pulsar clusters may have different evolutionary origins, since the companion stars to these pulsars in the two clusters show different chemical composition. Four clusters are found for normal pulsars. Possible implications for these clusters are also discussed. Our second example is to calculate the likelihood of unidentified \textit{Fermi} point sources being pulsars and rank them accordingly. In the ranked point source list, the top 5% sources contain 50% known pulsars, the top 50% contain 99% known pulsars, and no known active galaxy (the other major population) appears in the top 6%. Such a ranked list can be used to help the future follow-up observations for finding pulsars in unidentified \textit{Fermi} point sources.Comment: 9 pages, 4 figures, accepted by MNRA

A Mathematical Model for Determining an Electrohydrodynamic Accelerator's Monopolar Flow Limit During Positive Corona Discharge

This paper presents a mathematical model establishing the velocity limit of EHD fluid accelerators with tip to plane and cylinder to plane electrode configurations. The model is based on the calculation of the electric field lines length and trajectory, allowing practical use even if only the spatial characteristics of the geometry, the fluid's ion mobility and the applied voltage are known. Experiments are performed with wire-plane and needle-grid electrode configurations to validate the developed mathematical model, both for the calculation of the average flow limit of the geometry and for the calculation of the flow limit at the end of each electric field line