Five-Phase Line Commutated Rectifiers

Multiphase systems including multiphase generators or motors, especially five-phase, offer improved performance compared to three-phase counterpart. Five-phase generators could generate power in applications such as, but not limited to, wind power generation, electric vehicles, aerospace, and oil and gas. The five-phase generator output requires converter system such as AC-DC converters. This chapter introduces the basic construction and performance analysis for uncontrolled/controlled five-phase line commutated rectifier guided by numerical examples. This rectifier is suitable for wind energy applications to be the intermediate stage between five-phase generator and DC load or inverter stage. The filtration for AC side and effects of source inductances are detailed in other references. Here, this chapter gives the reader a quick idea about the analysis and performance of multiphase line commutated rectifiers and specifically five phase

Značajke istosmjernog pseudo-električnog (virtualno-katodnog) izboja u heliju

The plasma properties of a DC pseudo-discharge have been studied in helium as working gas. The discharge takes place between a disc cathode and a mesh anode, similar to a pulsed virtual-cathode oscillator. It has been found that breakdown characteristics essentially deviate from the expected regular Paschen curves. The current-voltage characteristics of the DC discharge show that it occurs in the region of abnormal glow. The breakdown voltage increases with the decrease of working gas pressure. When the electron beam density increases, the plasma covers the whole surface of the discharge cell outside the electrodes. The plasma has a negative potential with respect to the mesh and the location of the virtual cathode has been measured at around 1 cm from the mesh anode. The axial and radial distributions of electron temperature and ion density have been measured using a double electric probe. The electron temperature has been found to vary between 0.4 and 1 eV and the ion density from 2.8 ×1010 to 4.5 ×1010 cm-3, outside the electrodes. The plasma electron temperature was nearly constant along the axial and radial directions. The plasma density has been found to decrease with axial distance due to electron beam energy loss, and also decreased in the radial position due to diffusion to the discharge walls.Proučavali smo svojstva plazme u istosmjernom pseudo-izboju u heliju. Izboj je bio između kružne katode i mrežaste anode, slično pulsiranom oscilatoru s virtualnom katodom. Našli smo da značajke proboja znatno odstupaju od očekivanih prema običnim Paschenovim krivuljama. Krivulje struja – napon istosmjernog izboja ukazuju da se on dešava u području tinjavog izboja. Napon proboja se povećava smanjenjem tlaka helija. Nakon pojačanja gustoće elektronske struje uspostavi se plazma na cijeloj površini izbojne posude, izvan elektroda. U plazmi je negativan potencijal u odnosu na mrežastu anodu, i položaj virtualne katode se nalazi oko 1 cm iza te anode. Osnu i radijalnu raspodjelu temperature elektrona i ionsku gustoću mjerili smo pomoću dvostruke električne sonde. Našli smo elektronske temperature između 0.4 i 1 eV i ionsku gustoću od 2.8 × 1010 do 4.5 × 1010 cm−3 izvan elektroda. Temperatura elektrona u plazmi bila je gotovo stalna u osnom i radijalnom smjeru. Gustoća plazme se smanjivala u osnom smjeru zbog smanjenja energije elektronskog snopa, i također smanjivala u radijalnom smjeru zbog difuzije prema zidovima izbojne posude

A Review of Common Problems in Design and Installation of Water Spray Cooling and Low Expansion Foam System to Protect Storage Tanks Containing Hydrocarbons Against Fires

Tank fires are rare but carry significant potential risk to life and property. For this reason fire protection of tanks is critical. Fixed Low expansion foam and water spray cooling systems are one of the most effective and economical ways to reduce damages to a tank from fire. Such systems are currently installed in many companies but are not effective enough and require involvement of firefighters which in turn threaten their lives. This paper studies in a systematic way the problems of foam and cooling systems currently installed in a few domestic companies which operate storage tanks with focus on floating and fixed roof atmospheric tanks containing hydrocarbons and offers possible solutions for more efficient installation, design and operation of such systems

Cultural Alignment in Large Language Models: An Explanatory Analysis Based on Hofstede's Cultural Dimensions

The deployment of large language models (LLMs) raises concerns regarding their cultural misalignment and potential ramifications on individuals from various cultural norms. Existing work investigated political and social biases and public opinions rather than their cultural values. To address this limitation, the proposed Cultural Alignment Test (CAT) quantifies cultural alignment using Hofstede's cultural dimension framework, which offers an explanatory cross-cultural comparison through the latent variable analysis. We apply our approach to assess the cultural values embedded in state-of-the-art LLMs, such as: ChatGPT and Bard, across diverse cultures of countries: United States (US), Saudi Arabia, China, and Slovakia, using different prompting styles and hyperparameter settings. Our results not only quantify cultural alignment of LLMs with certain countries, but also reveal the difference between LLMs in explanatory cultural dimensions. While all LLMs did not provide satisfactory results in understanding cultural values, GPT-4 exhibited the highest CAT score for the cultural values of the US.Comment: 31 page

A Comparative Analysis of E-Scooter and E-Bike Usage Patterns: Findings from the City of Austin, TX

E-scooter-sharing and e-bike-sharing systems are accommodating and easing the increased traffic in dense cities and are expanding considerably. However, these new micro-mobility transportation modes raise numerous operational and safety concerns. This study analyzes e-scooter and dockless e-bike sharing system user behavior. We investigate how average trip speed change depending on the day of the week and the time of the day. We used a dataset from the city of Austin, TX from December 2018 to May 2019. Our results generally show that the trip average speed for e-bikes ranges between 3.01 and 3.44 m/s, which is higher than that for e-scooters (2.19 to 2.78 m/s). Results also show a similar usage pattern for the average speed of e-bikes and e-scooters throughout the days of the week and a different usage pattern for the average speed of e-bikes and e-scooters over the hours of the day. We found that users tend to ride e-bikes and e-scooters with a slower average speed for recreational purposes compared to when they are ridden for commuting purposes. This study is a building block in this field, which serves as a first of its kind, and sheds the light of significant new understanding of this emerging class of shared-road users.Comment: Submitted to the International Journal of Sustainable Transportatio

Assessment of apical leakage of different endodontic sealers -In vitro study

Aim: The aim of this prospective study was to assess in vitro the comparison between apical leakage of Apexit Plus (calcium hydroxide based), Roth 801 (Zinc oxide eugenol based) and Perma Evolution (epoxy resin based) sealers in lateral condensation technique using linear dye leakage penetration method.Material and methods: In this study 70 freshly extracted maxillary central incisors and canines with straight root canals were used. Teeth were decoronated and step back root canal preparation using Gates Glidden drill and stainless steel hand K files was performed with size 45 being the master apical cone. After preparation, the teeth were randomly divided into 5 groups. Three groups with 20 teeth for experimental and two groups with 5 teeth as positive and negative control. Obturation was done with lateral condensation in three groups with Roth 801, Apexit plus and Perma Evolution sealers. The obturated specimens were then stored in 2% Basic fuchsin dye for 72 hours. After splitting the teeth longitudinally, each tooth has been placed on a standardized scaled paper under the microscope and digital images have been captured by this microscope. Then the digital images were processed by Analyzing Digital Image software.Results: The results showed that Roth 801 sealer leaked significantly higher than both Apexit plus and Perma Evolution sealers (p < 0.05) and no statically significant difference has been found between Apexit plus and Perma Evolution sealers (p > 0.05).Conclusion: According to the methodology proposed and based on the results of this study, it may be concluded that Roth 801 showed the most leakage but Perma Evolution and Apexit plus showed similar sealing ability. However, further in vivo studies requirement should be done to find the best root canal filling material

Distributed System Contract Monitoring

The use of behavioural contracts, to specify, regulate and verify systems, is particularly relevant to runtime monitoring of distributed systems. System distribution poses major challenges to contract monitoring, from monitoring-induced information leaks to computation load balancing, communication overheads and fault-tolerance. We present mDPi, a location-aware process calculus, for reasoning about monitoring of distributed systems. We define a family of Labelled Transition Systems for this calculus, which allow formal reasoning about different monitoring strategies at different levels of abstractions. We also illustrate the expressivity of the calculus by showing how contracts in a simple contract language can be synthesised into different mDPi monitors.Comment: In Proceedings FLACOS 2011, arXiv:1109.239