Science China Technological Sciences最新文献

Energy efficiency improvement in Chinese construction has progressed rapidly over the past two decades. Nearly zero energy buildings (NZEBs), as an integrated solution for energy-efficient construction, have gained significant attention during China’s 13th Five-Year Plan period, with continuous maturation of the technical system. In this study, a research framework built upon the accomplishments of China’s National Key Research and Development Program is developed, and an in-depth analysis of the most cutting-edge research is provided by thoroughly reviewing the work conducted earlier. Developing NZEB in China has been categorized into three stages based on the characteristics of technological development: (1) definition and standards, (2) demonstration and promotion, and (3) cross-domain integration. This study discerns four noteworthy development trends by examining comprehensive data spanning the last decade from 100 NZEB and zero energy building. Further, a comprehensive analysis of essential technology advancements in line with these identified trends is performed. The issues and challenges arising from the increased application of renewable energy in the context of China’s carbon peak and carbon neutrality goals have also been discussed. Finally, based on this analysis, the challenges and corresponding suggestions for future research directions were proposed to help guide future studies exploring emerging trends in the NZEB field.

Carbon emissions associated with buildings are a major source of urban emissions. To put forward the methods and strategies to curb carbon emissions from urban building stock, it is not only necessary to establish a carbon emission calculation method for fine statistical analysis, but also to evaluate carbon emissions of urban planning schemes with applicable indexes. Currently, researches mainly focus on carbon emissions of individual buildings. When expanded to urban building stock, the calculation faces the lack of basic data, inadequate spatial analysis and unspecific carbon reduction indexes. Therefore, this study proposes a bottom-up calculation method for urban building stock, conducts spatial analysis based on carbon balance of urban grids, reveals the coupling mechanism between urban carbon reduction indexes and grid carbon emissions, and systematically establishes a carbon-reduction-oriented urban planning method that comprises calculation, analysis and evaluation, which is applied to Xi’an, China. This study provides a theoretical reference for cities to formulate carbon reduction targets and implement planning strategies by evaluating and predicting carbon emissions from urban building stock.

Based on thermal-entransy theory, the multi-objective constructal design of quadrilateral heat generation body (HGB) with similar shapes of leaves is studied further. The relationship between the aspect ratio of quadrilateral HGB and average temperature difference based on thermal-entransy dissipation is compared with that between the aspect ratio of quadrilateral HGB and the maximum temperature difference (MTD). The relationship between a composite function, consisting of linear weighting sum of the average temperature difference and MTD, and aspect ratio is obtained, and the optimal aspect ratios under minimum composite function with different weighting coefficients are obtained. Using the NSGA-II algorithm, the Pareto frontier containing a series of compromise results of average temperature difference and MTD is obtained, and optimization results are compared using the deviation index. There is no aspect ratio to make both MTD and average temperature difference reach the minimum, and the optimal aspect ratio under the minimum MTD is smaller than that under the minimum average temperature difference. The optimal aspect ratio is obtained by making the composite function reach the minimum, and the optimal aspect ratios obtained by minimizing the composite function with different weighting coefficients are different. Compared with the construct of the initial design, the value of the composite function with optimal construct decreases by 1.9%, and the aspect ratio of the quadrilateral HGB decreases by 9.1%. The average temperature difference with the optimal construct increases by 2.1%, and the MTD with the optimal construct decreases by 5.6%. The deviation index under multi-objective optimization is smaller than that under single-objective optimization, and the obtained construct has better comprehensive thermal conductivity. Compared with TOPSIS and LINMAP decision-making methods, the average temperature difference with composite function optimization increases by 0.55% and 0.62% respectively, but the MTD with composite function optimization decreases by 0.84% and 0.96%.

The rapid urban development has caused serious problems such as high energy consumption and carbon emissions, especially under the context of climate change. Buildings are particularly energy-intensive, generating about one third of global energy-related carbon emissions. Compared with active solutions (like mechanical systems), passive solutions offer the potential to balance energy consumption, thermal comfort, and ecological benefits. One potential solution is the integration of green glass space (GGS) into passive building design. GGS is a transitional building space with glass curtain walls that exhibit excellent insulation performance during winter. However, GGS is susceptible to overheating during summer, which limits its applicability. Therefore, this work proposes a strategy of integrating vertical greenery into GGS, leveraging the nature-based solution of greenery (i.e., flourishes in summer and withers in winter) to address this seasonal challenge of GGS. The results demonstrated that the strategic application of vertical greenery can effectively mitigate the overheating in GGS and improve comprehensive benefits. By using full coverage of vertical greenery in a linear layout, the air temperature of GGS and cooling energy consumption were largely reduced by 8.02°C and 12.2%, respectively, while the carbon abatement was enhanced by up to 101.11 tons. Based on a comprehensive evaluation of energy, economy, and environmental benefits, it is recommended to use a greenery configuration with 50% coverage in a vertical linear layout for GGS. The integration of greenery into building design can mitigate adverse environmental impacts, reduce energy consumption, and contribute to the sustainable development of low-carbon cities.

A major goal of current international urban development and construction is to lower carbon emissions. Synergies exist between the preservation of historic cities and the development of low-carbon cities; however, the relationship between preservation of historic cities and carbon emissions remains unclear. This study focuses on the cities in the “Yellow-Canal-Yangtze” watershed community, which includes the Yellow River Basin, Yangtze River Basin, and the Grand Canal region, and aims to verify the differences in CO₂ emissions (CE) between historic and non-historic cities through multiple comparisons after ANOVA. Additionally, Ridge Regression was used to determine the impact and dimensions of the relevant variables associated with the preservation of historic cities on CE. Combined with national development goals, this study predicts changes in the CE of historic city preservation under different scenarios. This study found significant differences between historic and non-historic cities, as the total CE of historic cities is 2.42 times higher than that of non-historic cities. The dimension with the largest difference was the CE related to transportation, with aviation emissions of historic cities reaching 15.22 times higher than that of non-historic cities. Although the preservation of historic cities has led to an overall increase in the CE, there is significant potential for CE reduction in land use, transportation infrastructure, and tourism development related to historic city preservation. In the future, historic cities can contribute to China’s carbon neutrality and the United Nation’s development goals through the creation of larger historical preservation areas, more convenient public transportation, and more vibrant tourism.

In this paper, a command filter-based adaptive fuzzy predefined-time event-triggered tracking control problem is investigated for uncertain nonlinear systems with time-varying full-state constraints. By designing a sliding mode differentiator, the inherent computational complexity problem within the predefined-time backstepping framework is solved. Different from the existing command filter-based finite-time and fixed-time control strategies that the convergence time of the filtering error is adjusted through the system initial value or numerous parameters, a novel command filtering error compensation method is presented, which tunes one control parameter to make the filtering error converge in the predefined time, thereby reducing the complexity of design and analysis of processing the filtering error. Then, an improved event-triggered mechanism (ETM) that builds upon the switching threshold strategy, in which an inverse cotangent function is designed to replace the residual term of the ETM, is proposed to gradually release the controller’s dependence on the residual term with increasing time. Furthermore, a tan-type nonlinear mapping technique is applied to tackle the time-varying full-state constraints problem. By the predefined-time stability theory, all signals in the uncertain nonlinear systems exhibit predefined-time stability. Finally, the feasibility of the proposed algorithm is substantiated through two simulation results.

Refrigeration challenges in regions with electricity shortages significantly decrease the quality of life for residents. In response to the prevalent refrigeration challenges in power-deficient areas, a novel distributed solar refrigeration system, comprising an evacuated U-tube solar collector and elastocaloric refrigerator, is theoretically introduced. Theoretical formulations for the energy efficiency and cooling power of the solar refrigeration system are presented to facilitate predictive assessments of the performance properties. Under typical conditions, the energy efficiency and cooling power of the solar refrigeration system are, respectively, 4.84% and 200.15 W. Subsequently, an extensive parameter study is conducted to comprehensively uncover key performance influencers and identify avenues for improvement. In addition, local sensitivity analyses identify that the length ratio is the top influential parameter, while the heat transfer fluid flow rate is the least sensitivity. A pragmatic case study, conducted with the weather data of Ningbo City, China, serves to empirically predict the performance of the hybrid system within the constraints of practical circumstances.

Cadmium (Cd) contamination in soil pore water is the primary pathway for Cd uptake by food crops, such as rice (Oryza sativa L.), posing significant risks to both food safety and human health. This study presents a novel soil pore water metal sensor (SPW-Msensor) for in situ and online monitoring of Cd in soil pore water (Cd_pw). The SPW-Msensor integrates an automated sampling device, comprising a Rhizon sampler and a reciprocating series pump with an independent dual plunger drive, along with a portable electrochemical sensor consisting of a screen-printed electrode, flow cell, and portable potentiostat. The SPW-Msensor enables the detection of Cd within a linear range of 50 to 300 ppb while exhibiting high anti-interference capability. Moreover, it demonstrates excellent repeatability (relative standard deviation values (RSDs) <3.6%) across 30 measurements conducted within a 2-h period. The method exhibits good agreement with results obtained using the standard ICP-MS method (RSDs < 5%). Additionally, this study establishes a positive correlation between Cd_pw detected by the SPW-Msensor and total Cd concentration (Cd_total) in the soil with an R² value equal to 0.89. Data acquired from the SPW-Msensor can be utilized for predicting Cd_total through partial least squares regression modeling, achieving model quality score (Q²) of 0.69, adjusted R² of 0.9345, and root mean square error (RMSE) of 0.1912. The SPW-Msensor demonstrates real-time monitoring capabilities for assessing Cd levels in acidified soils. This SPW-Msensor offers an efficient approach for in-situ and continuous monitoring of Cd_pw that provides valuable insights applicable to environmental and agricultural domains.

Computer vision tasks are crucial for aerospace missions as they help spacecraft to understand and interpret the space environment, such as estimating position and orientation, reconstructing 3D models, and recognizing objects, which have been extensively studied to successfully carry out the missions. However, traditional methods like Kalman filtering, structure from motion, and multi-view stereo are not robust enough to handle harsh conditions, leading to unreliable results. In recent years, deep learning (DL)-based perception technologies have shown great potential and outperformed traditional methods, especially in terms of their robustness to changing environments. To further advance DL-based aerospace perception, various frameworks, datasets, and strategies have been proposed, indicating significant potential for future applications. In this survey, we aim to explore the promising techniques used in perception tasks and emphasize the importance of DL-based aerospace perception. We begin by providing an overview of aerospace perception, including classical space programs developed in recent years, commonly used sensors, and traditional perception methods. Subsequently, we delve into three fundamental perception tasks in aerospace missions: pose estimation, 3D reconstruction, and recognition, as they are basic and crucial for subsequent decision-making and control. Finally, we discuss the limitations and possibilities in current research and provide an outlook on future developments, including the challenges of working with limited datasets, the need for improved algorithms, and the potential benefits of multi-source information fusion.

The tunneling-induced stress redistribution is dependent on the tunnel shape and the in-situ stress field, and the previous arch characterization method based on the circumferential or maximum principal stresses is only suitable for the circular tunnels under the hydrostatic stress field. In this study, a unified characterization method of the pressure arch for non-circular tunnels under the arbitrary stress field is proposed. By comparing the variations of compressive stress in different directions due to excavation, the ratio of the most significant increase in compressive stress is presented to characterize the arch effect, and the corresponding numerical algorithm is given. Since the proposed method takes the stress element as the basic analytical model, it can be easily applied to various complex excavation situations. Thereafter, combined with the established folding catastrophic model, an objective and unified quantitative method of the pressure arch boundaries is given. Using the proposed method, the longitudinal evolution of the pressure arch is analyzed. According to the expansion rate of the arch boundaries, three evolution stages including the initial formation, rapid expansion and stabilization are categorized. Parametric studies are conducted to illustrate the effect of ground properties and support stiffness on the pressure arch formation. It is found that the ground strength parameters and burial depth affect the arch range at a decreasing rate, while they have little effect on the arch shape. The lateral pressure coefficient has a significant effect on both the shape and range of the pressure arch. Increasing the support stiffness helps reduce the pressure arch range with a decreasing rate, while the synchronous variation of the elastic moduli of the surrounding rock and support does not affect the arch range under a certain relative elastic modulus. Finally, field monitoring is conducted to validate the proposed method in actual support design.