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New light on plant ash glass found in Africa: evidence for Indian Ocean Silk Road trade using major, minor, trace element and lead isotope analysis of glass from the 15th—16th century AD from Malindi and Mambrui, Kenya
Get PDFSeventeen glass vessels and twenty glass beads recovered from the excavations at the ancient city of Malindi and the archaeological site of Mambrui in Kenya, east Africa were analysed using electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The results show that all of the glass samples are soda-lime-silica glass. They belong to the high alumina -plant ash glass type, characterised by high alumina and relatively low calcium contents, widely distributed in eastern (10th – 16th centuries AD) and southern Africa (13th - 15th centuries AD), Central Asia (9th – 14th centuries AD) and southeast Asia (12th – 13th centuries AD), made with plant ashes and sands. This is an understudied glass type for which previous research has indicated there were three types. When compared with published research on such glasses using Zr, Ti, Ba, Cr, La, Li, Cs, Na2O, MgO and CaO we have identified at least four different compositional groups of v-Na-Al glass: Types A, B, C and D. By comparing the results with contemporary v-Na-Al glass vessels and beads from Central Asia, Africa, and southeast Asia we show that most of the Malindi and Mambrui glass share similar characteristics to the compositions of Mapungubwe Oblate and some of the Madagascar glass beads from southern Africa. They belong to Type A v-Na-Al glass which is characterised by an elevated level of Ti and Ba and a relatively high ratios of Cr/La, relatively low Zr concentrations and low ratios of Zr/Ti. Differences in Zr, Li, MgO and Na2O concentrations in Type A glass indicates that there are subgroups which might derive from different glass workshop(s) specialising in Type A v-Na-Al glass production. Comparison with the chemical compositions of glass from Ghazni, Afghanistan and Termez, Uzbekistan, and by using lead isotope analysis, we suggest v-Na-Al glass was manufactured in Central Asia and possibly worked into vessels and beads there
Polyimide-coated fibre bragg grating (FBG) sensors for thermal mapping of electric machine windings
Get PDFThis paper presents a design concept and a prototype of a polyimide-coated Fibre Bragg Grating (FBG) thermal sensor system based on a fast scan tunable laser source (up to 1 kHz sensing frequency). This system was deployed to perform a comprehensive 2-D real-time radial and axial thermal profiling of an electromagnetic coil - the short duty cycle electric machine (EM) windings. The thermal measurements were performed using an equivalent prototype consisting of an FBG interrogator, a multi-FBG string temperature sensor, power resistors (thermal objects), and conventional thermocouples used for measurement comparison. The FBG measurements of copper windings were subsequently carried out using a copper coil with FBG sensors system to map the radial and axial temperature distribution of the coil. The experimental results show that Polyimide-coated FBG sensor can be used for multi-point temperature monitoring of electromagnetic coils with a sensing temperature range of 20-200°C, a spatial resolution of 6cm, and a measurement error of ± 2%. The obtained thermal maps can be used for the identification of hot spot locations in electromagnetic coil systems
Using explicit teaching of philosophy to promote understanding of the nature of science: a case study from a Chinese high school
Get PDFAdopting an explicit and reflective approach to the teaching of the history and philosophy of science is useful in promoting high school students’ understanding of the nature of science. Whereas the history of science is usually signposted clearly in the school science curriculum, the philosophy of science is considered to be embedded in and integral to science education. This article argues that philosophical topics also need to be explicitly signposted and discussed in the teaching of the nature of science in high schools. This study investigates an interdisciplinary course on the nature of science in a Chinese senior high school. The course involved explicit teaching of philosophy of science topics with subject knowledge in each lesson. This mixed method design of the research included a modified version of the Views on Science, Technology and Society questionnaire as reported by Aikenhead and Ryan (Science Education, 76(5):477‑491, 1992) and phenomenographical analysis. Although the sample size is small, the results suggest that explicit teaching of philosophy of science topics helps students better understand both the nature of science and the relationship between science, technology and society
Accounting ethics education research
Get PDFThis study conducts a historical review of accounting ethics education literature over a forty-eight-year period from 1970 to 2018. It synthesizes accounting ethics education research published in academic research journals to identify trends and key themes. The study contributes to the body of accounting and education literature by giving meaning and shape to the development corpus of accounting ethics education research. Early research highlighted the need for ethics education in the accounting curriculum, while research in the latter part of the relevant period, moved toward understanding the impact of ethics education on students’ cognitive moral development and decision-making. Key topic themes inherent in the data include teaching methods, the importance of ethics education, ethical decision-making, moral development, the integration of ethics into accounting courses, and curriculum related issues. Alongside the rising number of publications during the relevant period, the findings suggest an increasing sophistication in teaching pedagogies and growing interest of ethics education research in developing countries. Overall, this study underlines the importance of ethics education research to the edification and ethics of future accountants
Local history between fact and fabrication: the history of Ningbo during the Tang Dynasty
Get PDFNingbo in the southeastern Chinese province of Zhejiang emerged as a city during the Tang dynasty (618–907), and was known at that time as Mingzhou. On the question where the administrative, political and economic center of the Ningbo region was located between 738 and 821 the various source materials either remain silent or tell very different stories. In this study I re-visit and discuss the three main theories using textual analysis combined with archaeological evidence. On the basis of textual and recent archaeological evidence this study argues that today’s location of Ningbo at Sanjiangkou was the political, economic and cultural center of Eastern Zhejiang over 400 years earlier than previously thought. This clearly demonstrates the geographical and economic importance of the location at Sanjiangkou and the political stability of the region from the end of the Eastern Jin dynasty (317–420)
Experimental statistical method predicting AC losses on random windings and PWM effect evaluation
Get PDFNowadays, one of the challenges in transport electrification is the reduction of the components’ size and weight in order to improve the power density. This is often achieved by designing electrical machines with higher rotational speeds and excitation frequencies. In addition, the converter needs to control the machine over a wide speed range given by the mission profile. Therefore, copper losses can significantly increase due to the combination of high frequency excitation and the harmonics introduced by the converter .The winding arrangement design plays a key role in the minimization of the copper losses. This paper presents an in depth study on AC losses in random windings for high frequency motor applications. An analytical method is compared against 2-D Finite Element (FE) simulation results. These are then compared to experimental measurements taken on a custom motorette. Importantly, in order to take into account the random positions of each strand within the machine slots, an Experimental Statistic Method (ESM) is proposed. The ESM allows to define the probability distribution which is useful to evaluate the winding copper losses at the design stage. The contribution of the Pulse Width Modulation (PWM) effect is also considered and experimentally evaluated. IEE
The champion of urban water resources management in the Chinese city — the case of Ningbo
Get PDFNingbo is a coastal megacity located at the East Coast of China and developing rapidly with proactive trading and export economic activities. The city owns a ranked top ten international port and it is the major strategic spot of 21st century maritime Silk Road from the “Belt and Road” policy established for promoting further international trades and developments. In future, populations and economy in Ningbo are expected continuously growing in the next few decades. The demand of quality freshwater resources thus is enormously increasing. Ningbo municipal government has established the “Five water management” (五水共治) policy in 2013 that aims to manage (i) sewage discharge; (ii) flooding; (iii) surface water; (iv) water conservation and (v) freshwater supply. Indeed, the municipal government also liaised and initiated the “Sponge City Program” after 2015 that Ningbo was selected as one of the pilot city; these policies and practices are successful up to now. This article adopts the case study of Ningbo to investigate the reasons of municipal government to promote the policy, to understand the public perception of this water management policy in Ningbo through conducted semi-structured interviews. During the 2017 and 2019, we conducted a questionnaire (N = 110) and interviews (N = 10) that follow up for justification of the public perception with the local communities. Our findings indicated that the communities had not been engaged closely with these practices, but generally supporting these two urban water management practices; and agreed that the urban water conditions (urban floods and pollution) had been improved. Also, the article discusses whether these (5 Water and SCP) practices can be extensively applied in other Chinese cities. We will provide recommendations at the end of the article
Investigating electrical drive performance employing model predictive control and active disturbance rejection control algorithms
Get PDFMany issues can degrade the electrical drive performance such as cross-coupling, time delay, external disturbances, and parameter variation. The Synchronous Reference Frame (SRF) PI Current Controller (CC) is the most popular control scheme for the motor drive current control due to its simplicity. However, the PI controller does not have an optimal dynamic response due to the reasonably low transient response of the integral parts. Furthermore, the tuning of the PI controller depends heavily on the machine’s parameters. Recently, alternative control schemes such as Model Predictive Control (MPC) and Active Disturbance Rejection Control (ADRC) are studied due to their dynamic performance and disturbance rejection capability, respectively. This paper presents a comparative study between the conventional PI, ADRC, and MPC control schemes applied for Permanent Magnet Synchronous Motor (PMSM) taking into consideration the operational issues of electrical drives
Production of H2-rich syngas from lignocellulosic biomass using microwave-assisted pyrolysis coupled with activated carbon enabled reforming
Get PDFThis study focuses on the use of a microwave reactor that combines biomass pyrolysis, at mild temperature, with catalytic reforming of the pyrolytic gas, using activated carbon, for generating hydrogen-rich synthesis gas. The traditional pyrolysis of biomass coupled with the reforming of its pyrolytic yields were also conducted using an electrically heated reactor. The bio-oil attained from conventional pyrolysis was higher in comparison to the yield from microwave pyrolysis. The reforming of the pyrolytic gas fraction led to reductions in bio-oil yield to <3.0 wt%, with a simultaneous increase in gaseous yields. An increase in the syngas and H2 selectivity was discovered with the reforming process such that the use of microwave pyrolysis with activated carbon reforming produced 85 vol% synthesis gas fraction containing 55 vol% H2 in comparison to the 74 vol% syngas fraction with 30 vol% H2 obtained without the reforming. Cracking reactions were improved with microwave heating, while deoxidation and dehydrogenation reactions were enhanced by activated carbon, which creates a reduction environment. Consequently, these reactions generated H2-rich syngas formation. The approach implemented in this study revealed higher H2, syngas yield and that the overall LHV of products has huge potential in the transformation of biomass into high-value synthesis gas
A novel approach for the determination of the height of the tropopause from ground-based GNSS observations
Get PDFIn this paper, we present a new method to calculate the height of the second lapse-rate tropopause (LRT2) using GNSS high-precision data. The use of GNSS data for monitoring the atmosphere is possible because as the radio signals propagate through the troposphere, they are delayed according to the refractive index of the path of the signal. We show that by integrating the vertical profile of the refractive index in the troposphere, we are able to determine the altitude of LTR2. Furthermore, as GNSS data is available from many stations around all latitudes of the globe and make up a network with high spatial and temporal resolution, we can monitor the diurnal cycle of the variables related to the refractive index of the path of the signal. A comparison between the heights of the LRT2 obtained with radiosonde data and with this novel method is presented in the paper, and it shows good agreement. The average difference found is ≤1 km for stations between the latitudes of 30°S and 30°N
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