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The paper aims to construct a spatiotemporal situational awareness framework to sense the evolutionary situation of public opinion in social media, thus assisting relevant departments in formulating public opinion control measures for specific time and space contexts.

The spatiotemporal situational awareness framework comprises situational element extraction, situational understanding and situational projection. In situational element extraction, the data on the COVID-19 vaccine, including spatiotemporal tags and text contents, is extracted. In situational understanding, the bidirectional encoder representation from transformers – latent dirichlet allocation (BERT-LDA) and bidirectional encoder representation from transformers – bidirectional long short-term memory (BERT-BiLSTM) are used to discover the topics and emotional labels hidden in opinion texts. In situational projection, the situational evolution characteristics and patterns of online public opinion are uncovered from the perspective of time and space through multiple visualisation techniques.

From the temporal perspective, the evolution of online public opinion is closely related to the developmental dynamics of offline events. In comparison, public views and attitudes are more complex and diversified during the outbreak and diffusion periods. From the spatial perspective, the netizens in hotspot areas with higher discussion volume are more rational and prefer to track the whole process of event development, while the ones in coldspot areas with less discussion volume pay more attention to the expression of personal emotions. From the perspective of intertwined spatiotemporal, there are differences in the focus of attention and emotional state of netizens in different regions and time stages, caused by the specific situations they are in.

The situational awareness framework can shed light on the dynamic evolution of online public opinion from a multidimensional perspective, including temporal, spatial and spatiotemporal perspectives. It enables decision-makers to grasp the psychology and behavioural patterns of the public in different regions and time stages and provide targeted public opinion guidance measures and offline event governance strategies.

The purpose of this paper is to build a warranty cost model for consumer electronics with short lifecycle and frequently upgraded process in generations. Meanwhile, a new warranty service method of replacing the failed old generation (OG) products by new generation (NG) products is proposed to cease the service capability for the OG products from manufacturers’ viewpoint.

A model is built to find an optimal time to switch to the new warranty service method to minimize the warranty cost of the OG products. The inventory cost of spare parts of OG products for warranty, repair cost and manufacturing cost of NG products are taken into account. Meanwhile, a mixed strategy is studied by providing options to customers for replacing their failed OG products with NG products by paying a discounted price of the OG products. Moreover, numerical experiments are conducted to test the effects of different parameters on the optimal solutions.

Solutions to the proposed model are discussed with analytic method and it is proved that the optimal solution exists in the considered situations. The mixed strategy considering the willingness of customers can result in the reduction of the warranty cost.

This paper analyzes the situation that more than one generations of products are in the marketplace simultaneously. Furthermore, this work makes a useful contribution for manufacturers to decrease their warranty cost by changing the service method, and provides the optimal warranty strategy for manufacturers considering the willingness of customers.

The color painting of ancient buildings has high historical and artistic value but is prone to aging due to long-term outdoor exposure. The purpose of this study is to develop a new type of sealing coating to mitigate the impact of ultraviolet (UV) light on color painting.

The new coating was subjected to a 500-h UV-aging test. Compared with the existing acrylic resin Primal AC33, the UV aging behavior of the new coating, such as color difference and gloss, was studied with aging time. The Fourier infrared spectra of the coatings were analyzed after the UV-aging test.

Compared with AC33, the antiaging performance of SF8 was substantially improved. SF8 has a lower color difference value and better light retention and hydrophobicity. The Fourier transform infrared spectroscopy results showed that the C-F bond and Si-O bonds in the resin of the optimized sealing coating protected the main chain C-C structure from degradation during the aging process; thus, the resin maintained good stability. The hindered amine light stabilizer TN292 added to the coating inhibited the antiaging process by trapping active free radicals.

To address the problem of UV aging of oil-decorated colored paintings, a new type of sealing coating with excellent antiaging properties was developed, laying the foundation for its demonstration application on the surface of ancient buildings.

Based on the textual-analyzed data covering 2148 IPO firms in China’s stock market during the 2007–2018 period, the authors’ purpose is to examine the influence of anti-takeover provision (ATP) adoption on initial public offerings (IPO) underpricing and identify the reducing effect of the former.

The authors examine the sample consisting of Chinese A-share listed IPO firms between 2007 and 2018 from China Stock Market Accounting Research and Chinese Research Data Services, with ATP data collected from the IPO firm chapters. Specifically, the authors use text analysis to identify whether there are ATPs in the IPO firm chapters, as well as the number of ATPs. H1: IPO underpricing is less severe for firms adopting ATPs. H2: The effect of ATP adoption on IPO underpricing is more salient for firms in worse information environments.

The authors examine the influence of ATP adoption on IPO underpricing and identify the reducing effect of the former. This effect can be explained by the fact that adopting ATPs in IPO firm chapters can reduce information asymmetry to a large extent by helping external investors obtain more private information, which alleviates IPO underpricing. The authors also find that the reducing effect is more significant in the worsened information environment. Furthermore, the authors explore the influence of adopting ATPs on other IPO characteristics and find positive effects on IPO over-subscription, funds raised and trading activity and negative effects on listing fees.

This study mainly contributes to the literature from the following two aspects. First, the study enriches the literature about the influencing factors of IPO underpricing. Second, the study also enriches the literature about the economic consequences of ATP adoption. This study also has important policy implications. With the coming of the era of decentralized ownership in China’s capital market, ATP adoption has become more important and attracted more attention. Also, investors focus more on pricing efficiency. The findings in this paper provide a more comprehensive understanding of the relationship between ATP adoption and IPO underpricing.

This study aims to form a new concept of power-to-gas-based virtual power plant (GVPP) and propose a low-carbon economic scheduling optimization model for GVPP considering carbon emission trading.

In view of the strong uncertainty of wind power and photovoltaic power generation in GVPP, the information gap decision theory (IGDT) is used to measure the uncertainty tolerance threshold under different expected target deviations of the decision-makers. To verify the feasibility and effectiveness of the proposed model, nine-node energy hub was selected as the simulation system.

GVPP can coordinate and optimize the output of electricity-to-gas and gas turbines according to the difference in gas and electricity prices in the electricity market and the natural gas market at different times. The IGDT method can be used to describe the impact of wind and solar uncertainty in GVPP. Carbon emission rights trading can increase the operating space of power to gas (P2G) and reduce the operating cost of GVPP.

This study considers the electrical conversion and spatio-temporal calming characteristics of P2G, integrates it with VPP into GVPP and uses the IGDT method to describe the impact of wind and solar uncertainty and then proposes a GVPP near-zero carbon random scheduling optimization model based on IGDT.

This study designed a novel structure of the GVPP integrating P2G, gas storage device into the VPP and proposed a basic near-zero carbon scheduling optimization model for GVPP under the optimization goal of minimizing operating costs. At last, this study constructed a stochastic scheduling optimization model for GVPP.

The purpose of this paper is to study the influence of temperature on the acceleration and simulation of indoor corrosion tests and the corrosion behavior of Q235 carbon steel.

The indoor corrosion test was carried out by continuous salt spray in a salt spray chamber. Weight loss analysis, X-ray diffraction, cannon 1500 D, scanning electron microscopy and electrochemical techniques are used to analyze the results.

It was found that thickness loss of Q235 carbon steel increases with higher temperature and it can reach 0.095 mm at 50°C. Compared with the Xisha exposure test, the acceleration rate can achieve 230 times. This phenomenon indicates that decreasing the experimental temperature is beneficial to the anti-corrosion of the Q235 carbon steel. It is fascinating to find that acceleration and simulation increase with temperature simultaneously, which shows that β-FeOOH promotes the corrosion rate and α-FeOOH provides high simulation. Meanwhile, electrochemical impedance spectroscopy indicates that the resistance of the rust layer improves with temperature.

Through the study, the authors found that with the increase of temperature, the acceleration and simulation of indoor corrosion test improved, corrosion products and kinetics are the same as those in outdoor exposure test, and which means that the laboratory can achieve the long-term corrosion degree of outdoor exposure in a short time, and the similarity with outdoor exposure is high. This helps to the study of marine atmospheric corrosion, and indoor accelerated corrosion tests can largely eliminate regional differences by adjusting some environmental factors, and lay a foundation for marine atmospheric corrosion.

The effects of temperature on the acceleration and simulation of indoor corrosion tests are discussed. Through laboratory experiments, the long-term service life of Q235 carbon in the Xisha marine atmosphere can be predicted effectively.

With the rapid development of social media, the occurrence and evolution of emergency events are often accompanied by massive users' expressions. The fine-grained analysis on users' expressions can provide accurate and reliable information for event processing. Hence, 2,003,814 expressions on a major malignant emergency event were mined from multiple dimensions in this paper.

This paper conducted finer-grained analysis on users' online expressions in an emergency event. Specifically, the authors firstly selected a major emergency event as the research object and collected the event-related user expressions that lasted nearly two years to describe the dynamic evolution trend of the event. Then, users' expression preferences were identified by detecting anomic expressions, classifying sentiment tendencies and extracting topics in expressions. Finally, the authors measured the explicit and implicit impacts of different expression preferences and obtained relations between the differential expression preferences.

Experimental results showed that users have both short- and long-term attention to emergency events. Their enthusiasm for discussing the event will be quickly dispelled and easily aroused. Meanwhile, most users prefer to make rational and normative expressions of events, and the expression topics are diversified. In addition, compared with anomic negative expressions, anomic expressions in positive sentiments are more common. In conclusion, the integration of multi-dimensional analysis results of users' expression preferences (including discussion heat, preference impacts and preference relations) is an effective means to support emergency event processing.

To the best of the authors' knowledge, it is the first research to conduct in-depth and fine-grained analysis of user expression in emergencies, so as to get in-detail and multi-dimensional characteristics of users' online expressions for supporting event processing.

The purpose of this paper is to examine the most interesting research question of the past decade – What Lures the Bears? Leveraging the public sector management and international business strategy literature, the paper first presents an overview of the transformational dynamics of state-owned enterprises (SOEs) in three major phases – institutionalization, privatization, and corporatization, and internationalization. Then, it analyzes geographic patterns and industry trends of the outward foreign direct investment (FDI) projects announced by SOEs over an eight-year period.

Grounded in the exploratory research such as inductive and deductive logic, the study proposes theoretical constructs, and discusses several findings based on the data accessed from highly cited archival sources, such as the UNCTAD FDI stat/WIRs, the World Development Indicators, Doing Business Report, Global Competitiveness Report, the Index of Economic Freedom, the Academic Ranking of World Universities, and the Fortune Global 500.

Based on an analysis of global market trends (a sample of over 20 countries and five industries), the study highlights that SOEs from Asia and Europe have been greatly expanded into developed markets, thus to secure natural resources, to acquire strategic assets like technology, and to leverage the developed financial markets and better investment environment. Therefore, SOEs’ outward FDI strategy and overseas performance was driven by institutional transitions, resource security, home market development and government legitimacy may contribute to the competitive advantage of their home country.

The study offers several implications for the policymakers of the governments in emerging economies and bureaucratic management of SOEs. It recommends that state ownership pattern and bureaucratic system of SOEs need to be reexamined, revised, and corporatized in the changing dynamics of the multinational business environment, thus to secure resources, acquire technological know-how, and compete in home and global markets.

As a response to academic calls on the globalization, performance and governance mechanisms of SOEs in and out of emerging economies, this paper draws a unique presentation of the transformational dynamics of SOEs – establishment to internationalization.

This paper aims to design a global controller that is operational throughout all flight modes and less dependent on an accurate model.

By adopting the interconnection and damping assignment passivity-based control (IDA-PBC) technology and compensating extra inputs for handling the unknown dynamics and time-varying disturbances, a model-free control (MFC)-based global controller is proposed.

Test results indicate that the designed controllers are more suitable for actual flight as they have smaller position tracking errors and energy consumption in all flight phases than the excellent model-free controller intelligent-PID.

The designed global controller, which works in all flight modes without adjusting its structure and parameters, can realize a stable and accurate tracking control of a tail-sitter and improve the resistance to unknown disturbances and model uncertainties.

The newly-designed controller is considered as an enhanced version of the traditional MFC. It further improves the control effect by using the poorly known dynamics of the system and choosing the IDA-PBC as the control auxiliary input. This method eliminates the unnecessary dynamics to continuously stabilize the vehicle with suitable energy consumption covering its entire flight envelope.

The purpose of this paper is to obtain the environmental factor, which has the greatest effect on the corrosion rate of Q235 carbon steel under thin electrolyte layer, and to analyze the effect of this factor on the corrosion morphology, corrosion products and polarization process of Q235 carbon steel.

An electrochemical device, which can be used under thin electrolyte layer is designed to measure the corrosion current in different environments. Response surface methodology (RSM) is introduced to analyze the effect of environmental factors on corrosion rate. Scanning electron microscope (SEM) and X-ray diffraction (XRD) technique are used to analyze the results. The Tafel slopes of anode and cathode in different humidity and solution are calculated by least square method.

The three environmental factors are ranked according to importance, namely, humidity, temperature and chloride ion deposition rate. In a high humidity environment, the relative content of α-FeOOH in the corrosion product is high and the relative content of β-FeOOH is low. The higher the humidity, the lower the degree of anodic blockage, whereas the degree of cathodic blockage is independent of humidity. The above experiments confirm the effectiveness and efficiency of the device, indicating it can be used for the screening of corrosive environmental factors.

In this paper, an electrochemical device under thin film is designed, which can simulate atmospheric corrosion well. Subsequent SEM and XRD confirmed the reliability of the data measured by this device. The introduction of a scientific RSM can overcome the limitations of orthogonal experiments and more specifically and intuitively analyze the effects of environmental factors on corrosion rates.