A maximum power point tracking for a photovoltaic system based on optimum sinusoidal modulated control pulses

Photovoltaic systems have grown rapidly in the last few decades. This growth has enhanced research about this technology, focusing on reducing cost and improving efficiency. Maximum power point tracking (MPPT), which increases the overall efficiency of a PV system, is a main part of a PV system. In this paper, some MPPT methods have been critically reviewed. Fractional open-circuit voltage has been investigated. The approach of a separate PV array to obtain the open circuit voltage (Voc) is adopted. The proposed idea in this paper is based on optimising the control pulses for the DC-DC converter. The generation of control pulses is based on sinusoidal modulated pulse width modulation (SPWM). The output from the DC-DC converter is then fed into a low frequency square wave voltage-fed inverter circuit. The output is a fine sinusoidal waveform, although the inverter operates at a low frequency. The block diagrams and the results are presented

Voltage regulation considerations for the design of hybrid distribution transformers

The future substation depends on finding a way to mitigate the effects of the drawbacks of the conventional legacy by employing the efficiency of the solid state switches [1]. This paper discusses the considerations of designing a distribution transformer that provides additional functions in regulating the voltage and controlling the reactive power that is injected in the distribution network, using a fractional rated converter attached partially with the windings of the transformer. This approach aims mainly to enhance the unit with more flexibility in controlling the voltage at the last mile of the network, in order to decrease the losses and meet the future expectations for low voltage networks modifications, and that by using a power electronic (PE) approach has less losses and more functionality (depending on the reliability of transformer and intelligence of PE). The design of a hybrid distribution transformer is detailed and its functionality in regulating the voltage is discussed as a combination between the features of one of the most reliable network devices, the transformer, and the effect of PE existence with less losses in both switching and conduction losses. Reduced ratings PE are used in this approach, whereby the solid state switches are controlled according to the immediate need for voltage control in low voltage (LV) networks

An investigation of the use of compliments by Saudi Arabian students

This study investigates, from a sociolinguistic comparative perspective, the use of compliments by a group of twenty Saudi English speakers, twenty Saudi Arabic speakers and twenty native English speakers. The aim of the research is to identify evidence of the discourse features that suggest that language transfer is occurring. Finally, the research attempts to determine how religiosity affects the form of compliments for Saudi English speakers. A discourse completion test was used comprising six situations to collect data from the participants. The comparative analysis of the compliments from the three groups identified that transfer was not occurring in respect to the use of unbound formulas as this is not a culturally specific semantic form. Transfer was identified as occurring for bound semantic formulas. Two further findings are worthy of mention. The first is that learning English appears to be increasing the assertiveness of Saudi Arabian women as evidenced by a decline in the use of implicit compliments. The second is that there is a decline in the frequency of religious inclusions in the compliments of Saudi English speakers

Successful factors of leadership to create radical innovation culture in mature manufacturing organizations

Poster presented at Cranfield University’s 2019 Manufacturing Doctoral Community event

Efficiency of Aerosol Therapy through Jet Nebulizer, Breath-Actuated Nebulizer, and Pressurized Metered Dose Inhaler in a Simulated Spontaneous Breathing Adult

BACKGROUND: Aerosol therapy using albuterol is one of the most prescribed asthma treatments. The most frequently used methods of aerosol delivery are pneumatic jet nebulizer (JN), pressurized metered-dose inhaler (pMDI), and breath-actuated nebulizer (BAN). Choosing among these devices is usually not based on thorough comparison of efficiency or cost. We compare the efficiency of these three devices using a spontaneously breathing adult model. METHODS: We connected each aerosol generator—JN, BAN, or pMDI with a valved holding chamber (VHC)—to the face of an adult teaching manikin. Below the bifurcation, an elbow adaptor was connected to a corrugated tube and was angled to be at a lower level than the collecting filter to prevent droplets from dripping directly into the collecting filter. From the collecting filter, another corrugated tube was connected to a prevention filter, which was then connected to an adult breathing simulator. Spontaneous breathing parameters were VT 450 mL, RR 20/min, and I: E ratio 1:2. First, we compared JN, BAN (2.5 mg/3 mL), and pMDI (4 puffs); second, we compared JN and BAN 2.5 mg/0.5 mL plus 0.5 mL normal saline. Data were analyzed using spectrophotometry (276 nm). One-way ANOVA and independent sample t-tests were used (p\u3c0.05). RESULTS: There were no differences in inhaled mass percentage (p=0.172) JN, BAN, and pMDI in the first experiment. Treatment time with BAN was significantly longer (p=0.0001) than with JN or pMDI. In the second experiment, BAN delivered more medication (p=0.004) than jet nebulizer. Treatment time was significantly less with JN (p=0.010). There was no difference in residual volume among JN and BAN in both experiment (p=0.765, p=0.115). CONCLUSIONS: All the devices that were compared using a 3 ml or 4 pMDI puffs delivered comparable amount of medication with no significant difference. However, BAN using 1ml fill volume delivers more drug compared to JN. Additionally, treatment time was longest with BAN. Even with reduction of its filling volume, BAN delivers a higher amount of medication to that of pMDI but was not statistically significant

Formulaic Sequences: An Investigation of an EFL Textbook in Saudi Arabia

Over the last decade, an extensive body of literature has demonstrated the essential role of formulaic language in learning and teaching a second language (L2) (Martinez & Schmitt, 2012). Educators and policy makers in the Ministry of Education in Saudi Arabia have expressed their serious concerns about “the low level of achievement in English among students in schools and universities”(Alrashidi & Phan, 2015, p. 38). As a result, most Saudi universities have incorporated Preparatory Year Programs (PYP) to enable students to master crucial academic skills, and to target the English language instruction needs in many disciplines. The present study, therefore, intended to examine academic English-language formulas incorporated into an English Language Teaching (ELT) textbook specifically used to reinforce academic English for many Saudi university students undertaking their preparatory year. In this study, the corpus-driven approach was applied to identify the most frequently occurring 3-, 4-, and 5-word formulas in the textbook whose pragmatic functions were specified on the basis of Simpson-Vlach and Ellis’ taxonomy (2010). In addition, the corpus-based approach was used to compare the extent to which the Academic Formulas List (AFL) (Simpson-Vlach & Ellis, 2010) appeared in the textbook, and the number of times AFL formulas occurred. The major findings showed that the textbook comprised a total of 342 formulas: 217 formulas; 101 formulas; and 24 formulas for the 3-, 4-, and 5-word formulas, respectively. Furthermore, the textbook incorporated only 143 formulas out of 400 AFL formulas. Finally, the majority of the identified formulas functioned as constructing stance expression (46%), followed by referential expressions (36%), and lastly as discourse organizing expressions (18%). The results contribute to an understanding of the input that is provided in an ELT textbook, and to raise the awareness of the importance of formulas inclusion in ELT textbooks. The findings can therefore help L2 instructors, L2 researchers, and especially ELT publishers to not only incorporate academic formulas into ELT textbooks but also to integrate formulas with high utility for L2 learners. This implies that L2 formulas should not be included randomly, but in a way that is consistent with scholarly criteria

Production of English vowels by native Arabic speakers, The

2018 Spring.Includes bibliographical references.When Arabic learners first delve into the English language, they may find many difficulties in pronunciation due to the fact that there are vast differences between English and Arabic, especially regarding the number of vowels and their acoustic realizations. Very few studies have investigated this area of English language acquisition. The aim of this study is to examine the production of English vowels by Arabic speakers and to examine if there are gender differences in the production of English vowels by Arabic English learners. By using the phonetic software Praat, the values of duration and formant of vowel sounds was measured and obtained. English vowels produced by the subjects were recorded and analyzed using Praat, and were compared to results from a research project looking at English native speakers in Colorado. Since the participants were exposed to English and had lived in Colorado, USA, differences in vowel production were discussed and an analysis was conducted. The result of this study displayed that there are significant differences between Saudi ELLs and Colorado English native speakers in almost all the vowels. In addition, this study revealed the significant role of gender and regional dialect in producing English vowels by Arabic speakers