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Effects of fiber curvature on the microstructure of the interfacial transition zone in fresh concrete

CHEN Huisu, SUN Wei, ZHAO Qingxin, L. J. Sluys, P. Stroeven

《结构与土木工程前沿（英文）》 2007年第1卷第1期页码 99-106 doi: 10.1007/s11709-007-0010-6

摘要： The study on the interfacial transition zone (ITZ) of concrete has received lots of attention in the last decade. However, no information is available on the influence of the curvature of a rigid surface on the microstructure of ITZ. This paper employed computer simulation technology to study the influence of fiber curvature on the initial microstructure of ITZ in concrete. For the sake of simplification, the investigation was first focused on the mono-size spherical particle packing system around a cylindrical fiber with different diameters. An algorithm of serial cylindrical sectioning was developed. The curve of the solid volume fraction versus the distance to the surface of the fiber was used as a parameter to characterize the microstructure of the ITZ. Then, the influence of the ratio of fiber diameter to particle diameter on the initial ITZ s microstructure was studied. These curves were compared with the ones from flat aggregate surface on which mono-size spherical particles were packed. Furthermore, the multi-size spherical particles system was further investigated. The simulation results demonstrate that no matter whether the spherical particles system is mono-size or multi-size, the fresh ITZ s microstructure is irrelevant to the curvature of the fiber. The shape of the curve of solid volume fraction versus the distance from the surface of the fiber is similar to that around a flat aggregate surface. In all cases, the horizontal coordinates of the first peak of the curves are located at around half the mean weight diameter of the particles. The thickness of ITZ reduces slightly with the decrease in water/cement ratio. Therefore, one may use the ITZ s microstructure around a flat aggregate surface to represent the ITZ s microstructure around a cylindrical fiber in the fresh state, and vice versa.

关键词： diameter initial microstructure influence surface spherical particle

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碳中和愿景下的中国能源转型之路 Article

张枢, 陈文颖

《工程（英文）》 2022年第14卷第7期页码 64-76 doi: 10.1016/j.eng.2021.09.004

摘要：

为了实现碳中和，中国能源系统需要经历深刻转型。本文利用能源-环境-经济模型China TIMES，设计了4个面向碳中和的能源转型情景，对因实现碳达峰时间不同和2050年碳排放量不同引起的转型路径差异进行了比较。结果显示，中国的二氧化碳排放量将在2025—2030年达到103亿~104亿吨的峰值。2050年，中国能源消费总量（电热当量）的60%、发电量的90%将由可再生能源提供，终端电气化率提升至接近60%。能源转型将带来持续的空气质量改善，2050年局地空气污染物排放较2020年减少85%，而提前达峰能够产生更多的近期收益。提前达峰要求在未来10年大量部署可再生能源，并在2025年后加速淘汰煤炭，这加大了近期的减排压力。然而，这些措施能尽早获得更好的空气质量，减少二氧化碳累计排放，为其他部门的转型争取更多时间。另外，本研究还发现，中国2050年的减排压力会在近期对可再生能源的发展、能源服务需求变化和福利损失产生影响。

关键词：碳中和能源转型气候变化减缓 China TIMES模型协同效应

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Effects of two transition metal sulfate salts on secondary organic aerosol formation in toluene/NO

Biwu CHU, Jiming HAO, Junhua LI, Hideto TAKEKAWA, Kun WANG, Jingkun JIANG

《环境科学与工程前沿（英文）》 2013年第7卷第1期页码 1-9 doi: 10.1007/s11783-012-0476-x

摘要： Aerosol phase reactions play a very important role on secondary organic aerosol (SOA) formation, and metal-containing aerosols are important components in the atmosphere. In this study, we tested the effects of two transition metal sulfate salts, manganese sulfate (MnSO ) and zinc sulfate (ZnSO ), on the photochemical reactions of a toluene/NO photooxidation system in a 2 m smog chamber. By comparing photochemical reaction products of experiments with and without transition metal sulfate seed aerosols, we evaluated the effects of transition metal sulfate seed aerosols on toluene consumption, NO conversion and the formation of ozone and SOA. MnSO and ZnSO seed aerosols were found to have similar effects on photochemical reactions, both enhance the SOA production, while showing negligible effects on the gas phase compounds. These observations are consistent when varying metal sulfate aerosol concentrations. This is attributed to the catalytic effects of MnSO and ZnSO seed aerosols which may enhance the formation of condensable semivolatile compounds. Their subsequent partitioning into the aerosol phase leads to the observed SOA formation enhancement.

关键词： manganese sulfate zinc sulfate seed aerosols toluene photooxidation secondary organic aerosol

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Epithelial-to-mesenchymal transition in cancer: complexity and opportunities

Yun Zhang, Robert A. Weinberg

《医学前沿（英文）》 2018年第12卷第4期页码 361-373 doi: 10.1007/s11684-018-0656-6

摘要：

The cell-biological program termed the epithelial-to-mesenchymal transition (EMT) plays an important role in both development and cancer progression. Depending on the contextual signals and intracellular gene circuits of a particular cell, this program can drive fully epithelial cells to enter into a series of phenotypic states arrayed along the epithelial-mesenchymal phenotypic axis. These cell states display distinctive cellular characteristics, including stemness, invasiveness, drug-resistance and the ability to form metastases at distant organs, and thereby contribute to cancer metastasis and relapse. Currently we still lack a coherent overview of the molecular and biochemical mechanisms inducing cells to enter various states along the epithelial-mesenchymal phenotypic spectrum. An improved understanding of the dynamic and plastic nature of the EMT program has the potential to yield novel therapies targeting this cellular program that may aid in the management of high-grade malignancies.

关键词： epithelial-to-mesenchymal transition cancer metastasis cancer stem cell

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Phase transition regulation and caloric effect

《能源前沿（英文）》 2023年第17卷第4期页码 463-477 doi: 10.1007/s11708-023-0860-1

摘要： Solid state refrigeration based on caloric effect is regarded as a potential candidate for replacing vapor-compression refrigeration. Numerous methods have been proposed to optimize the refrigeration properties of caloric materials, of which single field tuning as a relatively simple way has been systemically studied. However, single field tuning with few tunable parameters usually obtains an excellent performance in one specific aspect at the cost of worsening the performance in other aspects, like attaining a large caloric effect with narrowing the transition temperature range and introducing hysteresis. Because of the shortcomings of the caloric effect driven by a single field, multifield tuning on multicaloric materials that have a coupling between different ferro-orders came into view. This review mainly focuses on recent studies that apply this method to improve the cooling performance of materials, consisting of enlarging caloric effects, reducing hysteresis losses, adjusting transition temperatures, and widening transition temperature spans, which indicate that further progress can be made in the application of this method. Furthermore, research on the sign of lattice and spin contributions to the magnetocaloric effect found new phonon evolution mechanisms, calling for more attention on multicaloric effects. Other progress including improving cyclability of FeRh alloys by introducing second phases and realizing a large reversible barocaloric effect by hybridizing carbon chains and inorganic groups is described in brief.

关键词： phase transition regulation caloric effect solid state refrigeration

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Energy transition management towards a low-carbon world

《工程管理前沿（英文）》 2022年第9卷第3期页码 499-503 doi: 10.1007/s42524-022-0201-9

关键词： energy transition low-carbon technology system modeling transition path emission reduction

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Smart oilfield development and transition of petroleum-based cities

He LIU, Xinhua MA

《工程管理前沿（英文）》 2019年第6卷第2期页码 299-301 doi: 10.1007/s42524-019-0024-5

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Energy transition toward carbon-neutrality in China: Pathways, implications and uncertainties

《工程管理前沿（英文）》 2023年第10卷第2期页码 358-372 doi: 10.1007/s42524-022-0202-8

摘要： Achieving carbon neutrality in China before 2060 requires a radical energy transition. To identify the possible transition pathways of China’s energy system, this study presents a scenario-based assessment using the Low Emissions Analysis Platform (LEAP) model. China could peak the carbon dioxide (CO₂) emissions before 2030 with current policies, while carbon neutrality entails a reduction of 7.8 Gt CO₂ in emissions in 2060 and requires an energy system overhaul. The assessment of the relationship between the energy transition and energy return on investment (EROI) reveals that energy transition may decrease the EROI, which would trigger increased energy investment, energy demand, and emissions. Uncertainty analysis further shows that the slow renewable energy integration policies and carbon capture and storage (CCS) penetration pace could hinder the emission mitigation, and the possible fossil fuel shortage calls for a much rapid proliferation of wind and solar power. Results suggest a continuation of the current preferential policies for renewables and further research and development on deployment of CCS. The results also indicate the need for backup capacities to enhance the energy security during the transition.

关键词： carbon neutrality energy transition uncertainty EROI LEAP

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Policy entry points for facilitating a transition towards a low-carbon electricity future

《工程管理前沿（英文）》页码 462-472 doi: 10.1007/s42524-022-0214-4

摘要： This study extends the ambit of the debate on electricity transition by specifically identifying possible policy entry points through which transformative and enduring changes can be made in the electricity and socio–economic systems to facilitate the transition process. Guided by the “essence” of the multi-level perspective — a prominent framework for the study of energy transition, four such entry points have been identified: 1) destabilising the dominant, fossil fuel-based electricity regime to create room for renewable technologies to break through; 2) reconfiguring the electricity regime, which encompasses technology, short-term operational practices and long-term planning processes, to improve flexibility for accommodating large outputs from variable renewable sources whilst maintaining supply security; 3) addressing the impact of coal power phase-out on coal mining regions in terms of economic development and jobs; and 4) facilitating a shift in transition governance towards a learning-based, reflexive process. Specific areas for policy interventions within each of these entry points have also been discussed in the paper.

关键词： electricity transition multi-level perspective policy entry points

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Kinetic roughening transition and missing regime transition of melt crystallized polybutene-1 tetragonal

Motoi YAMASHITA

《化学科学与工程前沿（英文）》 2009年第3卷第2期页码 125-134 doi: 10.1007/s11705-009-0001-3

摘要： The morphology and lateral growth rate of polybutene-1 ( -PB1) have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110°C. The morphology of -PB1 crystals is a rounded shape at crystallization temperatures lower than 85°C, while lamellar single crystals possess faceted morphology at higher crystallization temperatures. The kinetic roughening transition occurs around 85°C. The nucleation and growth mechanism for crystallization does not work below 85°C, since the growth face is rough. However, the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism. The nucleation theory seems still to work even for rough surface growth. Possible mechanisms for the crystal growth of this polymer are discussed.

关键词： isotactic polybutene-1 tetragonal phase (form Ⅱ) melt crystallization growth rate kinetic roughening morphology

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Microwave-induced high-energy sites and targeted energy transition promising for efficient energy deployment

《能源前沿（英文）》 2022年第16卷第6期页码 931-942 doi: 10.1007/s11708-021-0771-y

摘要： Diverse interactions between microwaves and irradiated media provide a solid foundation for identifying novel organization pathways for energy flow. In this study, a high-energy-site phenomenon and targeted-energy transition mechanism were identified in a particular microwave heating (MH) process. Intense discharges were observed when microwaves were imposed on irregularly sized SiC particles, producing tremendous heat that was 8-fold the amount generated in the discharge-free case. Energy efficiency was thereby greatly improved in the electricity-microwaves-effective heat transition. Meanwhile, the dispersed microwave field energy concentrated in small sites, where local temperatures could reach 2000°C– 4000°C, with the energy density reaching up to 4.0 × 10⁵ W/kg. This can be called a high-energy site phenomenon which could induce further processes or reactions enhancement by coupling effects of heat, light, and plasma. The whole process, including microwave energy concentration and intense site-energy release, shapes a targeted-energy transition mechanism that can be optimized in a controlled manner through morphology design. In particular, the discharge intensity, frequency, and high-energy sites were strengthened through the fabrication of sharp nano/microstructures, conferring twice the energy efficiency of untreated metal wires. The microwave-induced high-energy sites and targeted energy transition provide an important pathway for high-efficiency energy deployment and may lead to promising applications.

关键词： microwave discharge high-energy sites targeted-energy transition morphology design energy efficiency

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Special issue: Transition management of energy systems towards carbon neutrality

《工程管理前沿（英文）》 2022年第9卷第3期页码 355-357 doi: 10.1007/s42524-022-0219-z

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On Social-technical Control of Safety Development in Economic Transition Background

Xue-qiu He,Song Li

《工程管理前沿（英文）》 2015年第2卷第3期页码 234-240 doi: 10.15302/J-FEM-2015025

摘要： Industrial safety and economic growth, two vital and inextricable forces affecting national culture and development, are worthy of much more interest and attention than this article can hope to generate. Following economic growth, industrial safety remains as a high priority in this nation’s quest for sustainable development. At present, while China is on its way to transforming its economic structure and growth models, talk of industrial safety appears with special regularity, for it also is undergoing profound changes as an important facet of modern China.

关键词： safety development economic growth economic transition social-technical control

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中国能源困境与转型

石元春

《中国工程科学》 2009年第11卷第11期页码 4-12

摘要：

中国石油和天然气资源贫乏，进口依存度超过50 %，煤炭的储产比也降到了50以下。中国能源消费结构中煤炭占到七成，CO₂排放超过美国。能源转型是当今世界，也是中国发展的大趋势。能源转型的方向是清洁能源，发展清洁能源的重点是可再生能源。中国清洁能源资源具有替代现能源消费总量七成以上的潜力；可再生能源中的小水电、风能和生物质能的可经济利用资源量分别是0.63亿吨，1.23亿吨和10.47亿吨（标煤）。中国生物质原料资源最丰富，而且可以立竿见影地增加农民收入，促进农村经济发展，是发展可再生能源和能源转型的战略重点。

关键词：中国能源困境转型

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Promotion of transition metal oxides on the NH

Weiman Li, Haidi Liu, Yunfa Chen

《环境科学与工程前沿（英文）》 2017年第11卷第2期 doi: 10.1007/s11783-017-0914-x

摘要： Manganese and chromium oxides promote the NH -SCR activity of Zr-Ce mixed oxide. Cr-Zr-Ce mixed oxide exhibited>80% NO conversion at a wide temperature window. More acid sites and higher reducibility may responsible for the high SCR ability. Chromium oxide and manganese oxide promoted ZrO -CeO catalysts were prepared by a homogeneous precipitation method for the selective catalytic reduction of NO with NH . A series of characterization including X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), Brunauer–Emmett–Teller (BET) surface area analysis, H temperature-programmed reduction (H -TPR), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the influence of the physicochemical properties on NH -SCR activity. Cr-Zr-Ce and Mn-Zr-Ce catalysts are much more active than ZrO -CeO binary oxide for the low temperature NH -SCR, mainly because of the high specific surface area, more surface oxygen species, improved reducibility derived from synergistic effect among different elements. Mn-Zr-Ce catalyst exhibited high tolerance to SO and H O. Cr-Zr-Ce mixed oxide exhibited>80% NO conversion at a wide temperature window of 100°C–300°C. DRIFT studies showed that the addition of Cr is beneficial to the formation of Bronsted acid sites and prevents the formation of stable nitrate species because of the presence of Cr . The present mixed oxide can be a candidate for the low temperature abatement of NO .

关键词： NH₃-selective catalytic reduction NO_x Low temperature Cr-Zr-Ce