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To improve the problems as the heavy burden of sewage treatment and environmental pollution caused by the traditional sodium hydrosulfite reduction dyeing of indigo, this study aims to carry out the direct electrochemical reduction dyeing for indigo with the eco-friendly Cu(II)/sodium borohydride reduction system under normal temperature and pressure conditions.

The electrochemical behavior of Cu(II)/sodium borohydride reduction system was investigated by cyclic voltammetry. And, the dyeing performance of the Cu(II)/sodium borohydride reduction system was developed by optimizing the concentration of copper sulfate in the anode electrolyte, applied voltage and reduction time via single-factor and orthogonal integrated analysis.

The dyeing performance of the Cu(II)/sodium borohydride reduction system is superior to that of the traditional reduction dyeing with sodium hydrosulfite. In the case of the optimized condition, the soaping fastness and dry/wet rubbing fastness of the dyed fabric in the two reduction dyeing processes were basically comparable, the K/S value of electrocatalytic reduction of indigo by Cu(II)/NaBH4 is 11.81, which is higher than that obtained by traditional sodium hydrosulfite reduction dyeing of indigo.

The innovative electrocatalytic reduction system applied herein uses sodium borohydride as the hydrogen source combined with Cu(II) complex as the catalyst, which can serve as a medium for electron transfer and active the dye molecule to make it easier to be reduced. The electrochemical dyeing strategy presented here provides a new idea to improve the reduction dyeing performance of indigo by sodium borohydride.

The purpose of this paper is to assess the process of prefabricated construction (PC) and analyze the impacts of rework risk to identify the core tasks for which the rework risk has severe impacts.

The methods consist of a literature review, expert interviews, a questionnaire survey and a rework risk function. The expert interviews and questionnaire survey were administered to experts in the entire process of PC from the dimensions of rework frequency, rework cost and rework time. Descriptive and inferential statistics were employed to analyze the data. The rework risk function was based on the loss expectancy method.

There are 13 core tasks that have higher impacts than the average level. The core tasks in the design stage account for 100% of the tasks in the stage, those in the manufacturing stage account for 20% and those in the construction stage account for 23.1%. Compared with the other stages, the design stage is characterized by significantly more frequent rework, higher rework costs and longer rework time. The manufacturing stage is characterized by significantly higher rework costs than the construction stage. The manufacturing stage and construction stage are co-reliant, and both are impacted by the design stage.

The findings provide stakeholders with a clear understanding of the core tasks of the PC process and represent a method for identifying core tasks. Stakeholders can learn from this to focus on the core tasks to reduce rework risk and manage the process with the priority of PC rework management based on the following order: design > manufacturing > construction. The approach is suitable for core task identification in other areas.

This research provides insight into rework risk management and provides a novel analysis method for rework risk and PC management from the perspective of the construction process. The findings are valuable for supporting stakeholders in making effective construction plans to reduce the impacts of rework risk in PC and provide a reference for future research on process optimization.

The authors designed those experiments to test the sensitivity of graphene when it is exposed to NO₂ gas, to find a way to decrease the recovery time of graphene and to find the difference effect between monolayer and bilayer graphene in the experiments.

The authors transferred graphene from film on Cu foil to NO₂ sensor sample and measured the resistances of on monolayer and bilayer graphene when they were exposed to NO₂ gas under different concentration; then, the authors obtained the results.

The results show that monolayer graphene exhibits a linear response when the NO₂ concentration is below 20 ppm. But the monolayer graphene will not be so sensitive to NO₂ gas when the concentration continues to reduce. The desorption time of monolayer graphene is longer when compared with bilayer graphene. It shows faster recovery time and higher response of bilayer graphene under low NO₂ concentration. And the limit detectable NO₂ concentration of bilayer graphene is 50 ppb. Desorption time of bilayer graphene is shortened to below 20 s under UV light.

The authors found a reliable way to decrease the recovery time of graphene when it is exposed NO₂ gas and got the concrete data.

The construction industry is facing challenges not only for workers' mobility in the pandemic situation but also for Lean Construction (LC) practise in responding to the high-quality development during the post-pandemic. As such, this paper presents a construction workforce management framework based on LC to manage both the emergency goal in migrant worker management and the long-term goal in labour productivity improvement in China.

The framework is created based on the integrated culture and technology strategies of LC. A combination of qualitative and quantitative methods is taken to explore factors influencing the mobility of construction workers and to measure labour productivity improvement. The case study approach is adopted to demonstrate the framework application.

For method application, a time-and-motion study and Percent Plan Complete indicator are proposed to offer labour productivity measurements of “resources efficiency” and “flow efficiency”. Moreover, the case study provides an industry level solution for construction workforce management and Lean Construction culture shaping, as well as witnesses the LC culture and technology strategies alignment contributing to LC practise innovation.

Compared with previous studies which emphasised solely LC techniques rather than socio-technical system thinking, the proposed integration framework as well as implementation of “Worker's Home” and “Lean Work Package” management models in the COVID-19 pandemic contribute to new extensions of both the fundamental of knowledge and practise in LC.

Through empirical analysis of Sino-US solar photovoltaic (PV) trade, this paper aims to evaluate the complementarity of Sino-US solar PV trade by adopting trade combination degree (TCD) index, export similarity index (SI) and trade complementarity index (TCI). It also explores the role of trade disputes over Sino-US solar PV trade between China and the USA and important factors affecting the complementarity of the trade.

Based on the comparative advantage theory, this paper selects the TCD, export SI and TCI to evaluate the complementarity of Sino-US solar PV trade comprehensively. Among them, TCD and SI can directly reflect the degree of cooperation and competition of Sino-US solar PV trade. Finally, the authors further analyze the decisive factors affecting the complementarity of Sino-US PV trade by entropy weight method and multiple linear regression analysis on the influencing factors of TCI.

The solar PV trade between China and the USA still has a close relationship, and there is solar PV trade cooperation and competition between the two countries. The factors affecting the complementarity of Sino-US solar PV trade are mainly exchange rate levels rather than trade disputes between China and the USA. The solar PV trade policies of China and the USA will have a great negative impact on the global supply chain of solar PV products. The major solar PV products in China and the USA have a clear division in the global supply chain and still have a strong trade complementarity.

This paper conducts an empirical analysis of the Sino-US solar PV trade rather than a policy discussion. This research has important practical significance for the healthy and sustainable development of solar PV trade for both countries. It can also provide references to the current trade disputes between China and the USA in a broader sense.

At present, the scale of China's floating population has reached 376 million people. Compared with the local inhabitants, the poverty problem of the floating population is more complex, and this problem should also attract the attention of all sectors of society. This paper aims to measure and analyze the multidimensional poverty of the floating population in China.

The data used in this paper are the data of the China Migrants Dynamic Survey (CMDS) in China. This survey is a large-scale national migratory population sampling survey organized by the China National Health Commission, covering 31 provinces (autonomous regions and cities) and other autonomous regions. This paper uses the dynamic monitoring and Alkire and Foster (A-F) method to study the multidimensional poverty problem of the floating population.

This study finds that income poverty is no longer the main type of poverty faced by the floating population. The multidimensional poverty of the floating population mainly occurs in the social security and education dimensions, of which social security has become the most severe poverty dimension of the floating population. From the perspective of group differences, compared with the floating population in urban areas, the multidimensional poverty of migrant workers is more serious. However, the poverty of migrant workers is mainly concentrated in one-dimensional poverty and two-dimensional poverty.

In the future, the authors should focus on the social security of the floating population in the place of influx and the education of the floating population.

Through the review of the existing literature, the authors find that the current research on the multidimensional poverty of the floating population is mainly concentrated on the migrant worker groups that move from rural areas to urban areas. However, insufficient attention is paid to the urban floating population groups moving between cities.

This paper proposes an intelligent fault diagnosis method, which aims to obtain the outstanding fault diagnosis results of the gearbox.

An intelligent fault diagnosis method based on energy entropy-weighted complementary ensemble empirical mode decomposition (EWCEEMD) and support vector machine (SVM) optimized by whale optimization algorithm (WOA) is proposed. The raw signal is first denoised by the wavelet noise reduction method. Then, complementary ensemble empirical mode decomposition (CEEMD) is used to generate several intrinsic mode functions (IMFs). Next, energy entropy is used as an indicator to measure the sensibility of the IMF and converted into a weight coefficient by function. After that, IMFs are linearly weighted to form the reconstruction signal, and several features are extracted from the new signal. Finally, the support vector machine optimized by the whale optimization algorithm (WOA-SVM) model is used for gearbox fault classification using feature vectors.

The fault features extracted by this method have a better clustering effect and clear boundaries under each fault mode than the unimproved method. At the same time, the accuracy of fault diagnosis is greatly improved.

In most studies of fault diagnosis, the sensitivity of IMF has not been appreciated. In this paper, energy entropy is chosen to quantify sensitivity. In addition, high classification accuracy can be achieved by applying WOA-SVM as the final classification model, improving the efficiency of fault diagnosis as well.

Graphene is a two-dimensional material. Its use has many advantages in gas sensing, but its long desorption process is problematic. The aim of this paper is to design a graphene-based gas sensor, study the response to NO₂ gas concentrations and find ways to accelerate the desorption process.

In one group, the sensor was placed in air to measure its initial resistance. Then, it was exposed to the NO₂ gas at a certain concentration. Finally, the sensor was exposed to light immediately after NO₂ gas exposure was ended. In another group, the sensor was heated using a heating plate at a stable temperature, before taking the measurements. Then the adsorption and desorption experiments were carried on.

Illumination and heating at a suitable temperature can expedite desorption of NO₂ molecules on graphene.

In the paper, two main methods are introduced to accelerate the desorption process when the NO₂ gas is absorbed on graphene. Through a series of experiments and analysis, the authors found that the recovery time could be reduced observably and the recovery performance of the graphene-based NO₂ sensor could be improved effectively.

This paper aims to estimate the international competitiveness of China’s biomass energy products during 2007-2016 in the context of the Belt and Road Initiative.

In this paper, the authors used the constant market share model and the revealed comparative advantage index to analyze the evolution trend of China’s biomass products’ international competitiveness during the past decade from 2007 to 2016 based on the market structure of the Belt and Road Initiative.

The results show that: China’s major biomass energy products have no comparative advantages in the world market, nevertheless, their international competitiveness is on the rise; China’s biomass energy products have been agglomerated to the regional markets where the market demand growth is fast in the Belt and Road countries; and the unreasonable structure is an important factor influencing the international competitiveness of China’s biomass exports.

The authors analyzed the international competitiveness of China’s biomass energy products based on the “Belt and Road Initiative” with all the trading items, in an effort to propose policy implications for enhancing the comparative advantages of China’s biomass products in the international market especially in the Belt and Road regions.

As foreign direct investment (FDI) plays an important role in economic globalization. This paper examines the structural features of the global FDI network based on FDI flows data and changes in the position of countries within the network.

In order to study the structural characteristics of the global FDI network and the status and changes of countries in the global FDI network, the authors build the investment network and apply the QAP (Quadratic Assignment Procedure) analysis to examine the evolutionary characteristics of the network and its influencing factors.

The global FDI network becomes more interconnected and has a clear “core-periphery” structure. The network connections and volumes have increased dramatically and most countries spread their assets across multiple countries, while only a handful of countries have concentrated investments. The topological structure of the global FDI network has changed noticeably, although this process has been slow and stable and countries in the core position have remained largely intact. The authors find that trade relations between countries, geographic distance and differences in economic size, income levels and institutional environments all have a significant impact on the global FDI network.

Although we find some valuable results, some aspects need further investigation. For example, how a country uses the investment network to boost its economy and how the different industries in the investment network change over time. It is important to get the industry-level details to understand the impact of the global investment network from a government's perspective.

FDI affects the distribution of international capital and contributes to the development of the global economy. Therefore, it is important to study the characteristics of the global FDI network and its development patterns. With more understanding about the network as well as its evolutionary pattern, the government can possibly carry out some policies to promote direct investments as well as economic development.

All countries should actively engage in international direct investments and strengthen their economic ties. At the same time, they can put more emphasis on inward or outward FDI based on their own level of economic development to better establish the circulation channel for domestic and international capital.

This paper examines foreign direct investments through the lens of a global network. In contrast to traditional bilateral studies, this paper focuses on the network structure and evolution, reflecting the dynamics of the entire direct investment system as well as the changing positions of participating countries.