Search results

The purpose of this paper is to propose a hybrid driving system that couples a motor and flywheel energy storage (FES) for a megawatt-scale superconducting direct current (DC) induction heater. Previous studies have proven that a superconducting DC induction heater has great advantages in relation to its energy efficiency and heating quality. In this heater, a motor rotates an aluminium billet in a DC magnetic field and the induced eddy current causes it to be heated. When the aluminium billet begins to rotate, a high peak load torque appears at a low rotation speed. Therefore, driving the billet economically has been a great challenge when designing the driving system, which is the focus of this paper.

A hybrid driving system based on FES is designed to provide extra torque when the peak load torque occurs at a low rotation speed, which allows the successful start-up of the aluminium billet and the operation of the motor at its rated capacity. The mechanical structure of this hybrid driving system is introduced. A simulation model was constructed using Matlab/Simulink and the dynamic start-up process is analysed. The influence of the flywheel’s inertia and required minimum engagement speed are investigated.

The results of this paper show that the hybrid driving system that couples FES and a motor can successfully be used to start the aluminium billet rotating. The flywheel’s inertia and engagement speed are the most important parameters. The inertia of the flywheel decreases with an increase in its engagement speed.

The cost of the driving system is significantly reduced, which is very important in relation to the commercial potential of this apparatus.

A novel start-up strategy for driving the aluminium billet of a superconducting DC induction heater at low speed is proposed based on FES.

The purpose of this paper is to analyze the influence of different types of winding configurations on the distribution of leakage field and branch currents for a 330-kVA high-temperature superconducting (HTS) transformer winding.

A three-dimensional electromagnetic model coupled with a circuit model validated by an experiment is developed to calculate the leakage field and current uniformity under four different types of secondary winding configurations. The four types of gaps between secondary windings are uniform gap, arithmetic progression (AP) gap, six sections with three different gaps and eight sections with four different gaps. A coefficient named as uneven degree is used to define the current nonuniformity.

The simulation results show that the currents and leakage field of double pancakes (DPs) on both sides are larger than those of the other DPs, and the currents of several middle DPs are smaller than the average rated current with an ISOB gap and larger than the average rated current with an IBOS gap. For any one of the four types of winding configurations, the type with the ISOB gap can prohibit the current nonuniformity more effectively, whereas the IBOS gap can decrease the leakage field more. The AP with the ISOB gap is a wise choice for decreasing the uneven degree and leakage field.

There is an optimal winding configuration for decreasing the leakage field and uneven degree of branch currents. The results and numerical model are very useful for the design of a HTS transformer.

The leakage field distribution and branch currents nonuniformity for 25 parallel DPs are investigated and optimized.

Summarises the environmental cadmium loading, human body cadmium (Cd) burden and the biological indicators of the early‐stage health effects induced by exposure to cadmium on the population of Daye county in China. Claims that urinary calcium and urinary low molecular weight protein are good biological indicators for the detection of the early‐stage renal dysfunction and recommend that the prevention and treatment of cadmium pollution be incorporated into primary health care. Cost‐benefit analysis of reduction of Cd emissions from the non‐ferrous smelter in Daye county indicates that the benefit‐cost ratio taking into account both direct health costs and indirect costs is far in excess of unity.

The purpose of this paper is to analyse and improve the temperature uniformity of aluminium billets heated by superconducting DC induction heaters.

A 3D electromagnetic model coupled with a heat transfer model is developed to calculate the heating process of the billets which are rotated in uniform transverse DC magnetic field. A laboratory-scale DC induction heater prototype has been built to validate the model. The results from simulation and measurement have a good agreement. The model is used to investigate the factors affecting the temperature uniformity of aluminium billets.

The results from simulation show that lower rotation speeds always mean better temperature uniformity along the radial direction, due to the increase in power penetration. However, the situation is very different for the temperature distribution along the axial direction. When the rotation speed is low, the temperature at the ends is lower than other parts. The situation reverses as the rotation speeds increase. This phenomenon is referred to as the “ending effect” in this paper.

Because of the ending effect, a lower rotation speed does not always result in better overall temperature uniformity, especially for billets of smaller sizes.

There is an optimal rotation speed that yields the best overall temperature uniformity. Lower rotation speeds are not always preferred. The results and numerical model developed are very useful in the design of a superconducting DC induction heater.

The temperature uniformity of aluminium billets heated by DC induction heaters is investigated and optimized.

The purpose of the paper is to provide a comparison of first‐ and second‐order two dimensional finite element models for evaluating the electromagnetic properties and calculating AC loss in high‐temperature superconductor (HTS) coated conductors.

The models are based on the two‐dimensional (2D) H formulation, which is based on directly solving the magnetic field components in 2D. Two models – one with a minimum symmetric triangular mesh and one with a single‐layer square mesh – are compared based on different types of mesh elements: first‐order (Lagrange – linear) and second‐order (Lagrange – quadratic) mesh elements, and edge elements.

The number and type of mesh elements are critically important to obtain the minimum level of discretization to achieve accurate results. Artificially increasing the superconductor layer and choosing a minimum symmetric mesh with triangular edge elements can provide a sufficiently accurate estimation of the hysteretic superconductor loss for a transport current.

This paper describes how the selection of mesh type and number of elements affects the computation speed and convergence properties of the finite element model using two different types of meshing. It offers an insight into the different factors modelers must consider when modeling HTS coated conductors and the methods that may be applied when extending the model to complex device geometries, such as wound coils.

Mobile agent, as a new mobile computing technology, has been applied to various parallel and distributed computing problem solutions. Several mobile agent systems have been built to drive the agents following a platform dependant scheme, and some formal approaches have been proposed to describe mobile agents’ behaviors or properties for respective purposes. However, there remains a lack of a standard approach to describing a mobile agent algorithm and its semantics from the viewpoint of a practical program, which makes it difficult to specify an algorithm unambiguously and verify its correctness formally. This paper proposes a practical approach to overcome that difficulty by defining a script language and associated mechanisms to specify and verify mobile agent algorithms. The language, called SMAL, can describe mobile agent’s behaviors clearly due to its explicitly defined semantics. Based on the semantics, a transformation function for converting the specified algorithm to its equivalent specification in Mobile UNITY, a well‐known mobile computation formal approach for correctness verification, is presented. Formal verification of the algorithms can be accomplished based on the UNITY‐logic rules.

The purpose of this paper is to investigate the main factors that may affect Italian consumers’ willingness to eat insects. Italy is a fairly special case among Western countries: in many Italian regions, there is old traditional food with insects.

Data come from a sample of 456 consumers living in four Italian regions. The empirical investigation involves several steps: modification of class distributions to obtain a balanced sample; model estimation using the least absolute shrinkage and selection operator; model evaluation using out-of-sample classification performance measures; and estimation of the “effect” of each explanatory variable via average predictive comparisons. The uncertainty associated with the whole procedure is evaluated using the bootstrap.

The interviewed consumers are generally unwilling to eat insect-based food. However, factors such as previous experience, taste expectations and attitude towards both new food experiences and sustainable food play an important role in shaping individual inclination towards eating insects.

The sample analysed in this study is not representative of the whole national population, as it happens in most papers dealing with entomophagy.

The paper revisits the issue using a relatively large sample and sophisticated statistical methods. The likely average effect of each explanatory variable is estimated and discussed in detail. The results provide interesting insights on how to approach a hypothetical Italian consumer in view of the possible development of a new market for edible insects.

The purpose of this paper is to explore the attitude of Italian consumers towards insect consumption. The use of insects as alternative protein source is claimed to be a solution to the environmental concerns over the production of animal proteins and to food security issues. Studies conducted in other European countries report that consumers are quite resistant to the introduction of insect-based products in their diet, although those who are more concerned about environmental and health show some interest towards insect consumption.

The authors conducted a survey with a 14-item questionnaire on 201 consumers, selected with a systematic sampling within a shopping mall. The factors influencing respondents’ attitude towards insect consumption were studied by means of a logistic regression.

Results show that 31 per cent of respondents were willing to try insects as food, while 5 per cent had already tried. Familiarity with foreign food, higher education and gender (male) positively influenced consumer attitude to entomophagy. Instead, the fear of insects and the idea that the taste might be disgusting were the main barriers to the willingness to try entomophagy, although these issues were mainly raised by consumers who had no direct experience with insects eating.

The paper is a first attempt of exploring the topic of entomophagy in the Italian context. Most of the results were consistent with previous research carried out in other countries. However, some barriers to insect consumption seem to be stronger in Italy than elsewhere.

Since stock return and volatility matters to investors, this study proposes to incorporate the textual sentiment of annual reports in stock price crash risk prediction.

Specific sentences gathered from management discussions and their subsequent analyses are tokenized and transformed into numeric vectors using textual mining techniques, and then the Naïve Bayes method is applied to score the sentiment, which is used as an input variable for crash risk prediction. The results are compared between a collection of predictive models, including linear regression (LR) and machine learning techniques.

The experimental results find that those predictive models that incorporate textual sentiment significantly outperform the baseline models with only accounting and market variables included. These conclusions hold when crash risk is proxied by either the negative skewness of the return distribution or down-to-up volatility (DUVOL).

It should be noted that the authors' study focuses on examining the predictive power of textual sentiment in crash risk prediction, while other dimensions of textual features such as readability and thematic contents are not considered. More analysis is needed to explore the predictive power of textual features from various dimensions, with the most recent sample data included in future studies.

The authors' study provides implications for the information value of textual data in financial analysis and risk management. It suggests that the soft information contained within annual reports may prove informative in crash risk prediction, and the incorporation of textual sentiment provides an incremental improvement in overall predictive performance.

Thailand has served as a major outbound tourist destination for Chinese tourists for decades. Behaviours demonstrated by Chinese tourists in Thailand are believed to have created an image of Chinese outbound tourists among the residents and have impacted on the sustainability of Thai tourism. This study aims to contribute a more comprehensive and nuanced understanding of the image of Chinese outbound tourists from the perspective of Thai residents’.

In-depth interviews were conducted with 15 Thai residents who have frequent contact with Chinese tourists.

The results reveal that Thai residents’ perceptions of Chinese tourists include both positive and negative images. Positive images consist of being filial and friendly (e.g. taking good care of the elderly and having close emotional ties within their touring group) and being wealthy and auspicious (e.g. having a lot of money to spend and tipping generously). Negative images include moral norms (e.g. making loud noises and jumping into a queue), hygiene habits (e.g. littering and spitting) and religious culture (e.g. touching and climbing Buddha statues).

This qualitative research promotes the study of destination residents’ perceptions of tourists’ in the context of outbound tourism and enriches the application of social representation theory from the perspective of residents in the field of tourism marketing. It generates a more nuanced comprehension of Thai residents’ perceptions of Chinese tourists, contributes to the government’s formulation of guidelines for civilised tourism and has benefits to the sustainable development of tourism destinations.

泰国居民对中国游客的形象感知

摘要

几十年来, 泰国一直是中国游客的主要出境旅游目的地。中国游客在泰国表现出的行为在居民中创造了中国出境游客的形象, 并影响了泰国旅游业的可持续性。这项研究旨在从泰国居民的感知出发, 对中国出境游客的形象进行更全面、细致的了解。

对15位经常与中国游客接触的泰国居民进行了深入访谈。

结果表明, 泰国居民对中国游客形象的感知既包括正面形象也包括负面形象。正面的形象包括孝顺和友善（例如, 照顾老人, 并在其旅行团中保持紧密的情感联系）, 富有和吉祥（例如, 有很多钱可花, 并慷慨地付小费）, 而负面的形象则包括道德规范（例如, 大声喧哗, 并插队）, 卫生习惯（例如, 乱扔垃圾和随地吐痰）以及宗教文化（例如, 触摸和爬到佛像上）。

这项定性研究弥补了出境旅游背景下目的地居民对游客形象的感知的差距, 并且从居民的角度出发丰富了社会表象理论在旅游营销领域的应用。它使泰国居民对中国游客的认识更加细致, 有助于政府制定有针对性的文明旅游指导方针, 有利于旅游目的地未来的可持续发展。

Percepción de los residents tailandeses sobre el comportamiento de los turistas chinos

Por décadas, Tailandia ha sido un principal destino tulístico de turismo emisor para los turistas chinos.El comportamiento de los turistas chinos en Tailandia ha impresionado las imagenes de los turistas chinos emisores a los habitantes, y ha afectado la sostenibilidad de la industria turística de Tailandia. Esta investigación tiene como objetivo comenzar con la percepción de los habitantes tailandeses para conocer una comprensión más completa y detallada de las imagenes de los turistas chinos emisores.

Entrevisitar en profundidad a 15 habitantes tailandeses que a menudo contactan con los turistas chinos.

Los resultados muestran, las percepciones de los habitantes tailandeses de las imagenes de los turistas chinos contienen las imagenes positivas y negativas. Los imágenes positivas incluyen fiedad filial y amabilidad (por ejemplo, cuida a los ancianos y mantiene una estrecha conexión emocional con su grupo de viaje), riqueza y buena suerte (Por ejemplo, tiene mucho dinero para gastar y propina generosa.) pero las imagenes negativas incluyen las normas étias (por ejemplo, hace ruido fuerte y corta en línea.) los hábitos de higienes (por ejemplo, tira basura al azar y escupiendo por todas partes.) y cultura religiosa (por ejemplo, toca y trepa los estatuas de Buda.)

Esta investigación cualitativa cierra la brecha en los percepciones de los habitantes de desino de las imagenes de turistas en el contexto del turisimo emisor y comenza con los aspectos de los habitantes enriquece la aplicación de la teoría de la representación social en el campo de marketing turístico. Deja los habitantes tailanteses conocer a los turistas chinos más detallada y ayuda al gobierno a desarrollar pautas específicas de turismo civilizado y es benificioso para el futuro desarrollo sostenible de los destinos turísticos.