Comparative carbon emission assessments of recycled and natural aggregate concrete: Environmental influence of cement content

This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications.The environmental influence of cement content,aggregate production,transportation,and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region.To obtain a detailed insight into the optimum life cycle parameters,a sensitivity study is carried out in which supplementary cementitious materials,different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered.The results show that carbon emissions were between 323 and 332 kgCO_(2)e per cubic metre of cement only natural aggregate concrete.These values can be reduced by up to 17%by replacing 25%of the cement with fly ash.By contrast,carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50%and 100%,and transportation is not included in analysis.However,the concrete with 50%recycled aggregate presented lower increase,only 0.3%and 3.4%for normal and high strength concrete,respectively.In some cases,the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%,and case-specific transportation distances were considered.In absolute values,the concrete mixes with 100%recycled aggregates and 25%fly ash had lower carbon emissions than concrete with cement and natural aggregates only.Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km)and the cement replacement by fly ash is equal or higher than 25%,considering that the mechanical properties are adequate for practical application.The observations from this paper show that recycled aggregate concrete with strength characteristics representative for structural members can have lower carbon emissions than conventional concrete,recommending them as an alternative to achieving global sustainability standards in construction.

Energy Efficiency of a Simulated Synthetic Natural Gas Combined Cycle (SNGCC)

The objective of this investigation is to analyze the impact of the flue gas recirculation (FGR) ratio on the different energy inputs and outputs of a SNGCC power plant as well as its overall efficiency. Simulation results indicate that increasing flue gas recirculation increases the energy consumed by the recirculation compressor and the energy produced by the gas turbine. On the other hand, it decreases the production of energy of the steam turbine and the energy consumed by the pump of the steam cycle. The overall energy efficiency of the SNGCC power plant is highest (41.09%) at a value of 0.20 of the flue gas recirculation. However, the flue gas composition with a FGR ratio of 0.37 is more suitable for effective absorption of carbon dioxide by amine solutions. Based on the low heating value (LHV) of hydrogen, the corresponding overall efficiency of the power plant is 39.18% and the net power output of the plant is 1273 kW for consumption of 97.5 kg/hr. of hydrogen.

A Relationship between Solar Activity and Frequency of Natural Disasters in China

The relationship between the length of the solar cycle, a good indicator of long-term change in solar activity, and natural disasters (drought, flood, and strong earthquakes) in China during the last 108 yearsis analyzed. The results suggest that the length of solar cycle may be a useful indicator for drought/flood and strong earthquakes. When the solar activity strengthens, we see the length of the solar cycle shorten and more floods occur in South China and frequent strong earthquakes happen in the Tibetan Plateau, but the droughts in East China as well as the strong earthquakes in Taiwan and at the western boundary of China are very few. The opposite frequencies occur when the solar activity weakens. The current study indicates that the solar activity may play an important role in the climate extremes and behavior in the lithosphere.

Natural thermoluminescence of fossil foraminiferals as a potential proxy for deep-sea temperature changes

Foraminiferal shells from two piston cores separately located at the Ninetyeast Ridge and the Bengal Fan of the Indian Ocean were selected and purified for measurements of natural thermoluminescence （NTL） intensity by a high precision thermoluminescence meter （RGD-3）. Variations of the NTL intensity along the two core sequences both spanning the last two glacial--interglacial cycles displayed a strong, identical signal of the global ice volume cycles, which matched well with their corresponding oxygen isotope data. As higher NTL intensity occurred within interglacial periods and changes in an NTL signal were most likely influenced by the temperature of ambient seawater in which the planktonic foraminiferal shells long existed, the NTL signal could be considered as a potential proxy for orbital scale temperature changes of bottom seawater in the tropical Indian Ocean.

Thermodynamic analysis and combined cycle research on recoverable pressure energy in natural gas pipeline

Current research and ways of capturing mechanical energy are discussed in this paper. By the aid of the comprehensive thermodynamic analysis and Aspen simulation tool, the amount of a vailable work that can be produced from capturing the pressure energy has been calculated. Based on the comprehensive thermodynamic analysis, two systems have been proposed to capture pressure energy of natural gas to generate electricity. In this study, the expression of exergy is given which can be used in evaluating purposes. A problem with this multidisciplinary study is the complicated boundary condition. In conclusion, a technical prospect on recoverable natural gas pressure energy has been presented based on total energy system theory.

35 Ma－An Important Natural Periodicity in Geological History： Concept of Natural Crisis and Its Possible Cause

Among the cyclicity shown by the geologic evolution of the earth, the periodicity of ca 35 Ma is expressed most distinctly, which is evidenced not only by global sea-level changes, biotic mass extinctions, tectonic episodes, magmatic cycles and climatic changes. but also by magnetic reversals and impact craterings. It is suggested that the periodicity of ca 35 Ma may represent a natural stage by which the earth has evolved, and can be taken as an objective criterion of determining the 2nd-order eustatic cycles and their sedimentary records-the mesosequences. Major geologic events in the earth's history are apparently clustered at some specific periods, suggesting natural crises. They are thought to have been controlled mainly by astronomic cycles. especially related to the crossing of the Solar system through the Calactic plane.

The Core Mechanism of Natural Selection: How the Natural Cycle of Potassium Resources Affects the Biological Evolution and the Change of Human Society

Darwin’s theory of evolution believes that biological evolution is a process of natural selection. This theory has been supported by much evidence, but the internal biological mechanism is not clear. Here, I elaborate on the cycle of potassium resources on the earth and the biological utilization and efficiency, which may be the core mechanism of natural selection and affect the evolution of organisms and the development of human society.

Process Simulation of a 620 Mw-Natural Gas Combined Cycle Power Plant with Optimum Flue Gas Recirculation

The main objective of this investigation is to obtain an optimum value for the flue gas recirculation ratio in a 620 MW-Natural Gas Combined Cycle (NGCC) power plant with a 100% excess air in order to have a composition of the exhaust gas suitable for an effective absorption by amine solutions. To reach this goal, the recirculated flue gas is added to the secondary air (dilution air) used for cooling the turbine. The originality of this work is that the optimum value of a Flue Gas Recirculation (FGR) ratio of 0.42 is obtained from the change of the slope related to the effects of flue gas recirculation ratio on the molar percentage of oxygen in the exhaust gas. Compared to the NGCC power plant without flue gas recirculation, the molar percentage of carbon dioxide in the flue gas increases from 5% to 9.2% and the molar percentage of oxygen decreases from 10.9% to 3.5%. Since energy efficiency is the key parameter of energy conversion systems, the impact of the flue gas recirculation on the different energy inputs and outputs and the overall efficiency of the power plant are also investigated. It is found the positive effects of the flue gas recirculation on the electricity produced by the steam turbine generator (STG) are more important than its cooling effects on the power output of the combustion turbine generator (CTG). The flue gas recirculation has no effects on the water pump of the steam cycle and the increase of energy consumed by the compressor of flue gas is compensated by the decrease of energy consumed by the compressor of fresh air. Based on the Low heating value (LHV) of the natural gas, the flue gas recirculation increases the overall efficiency of the power plant by 1.1% from 57.5% from to 58.2%.

A Comparative Environmental Evaluation of the Coal and Natural Gas Life Cycle

Natural gas and coal are the main primary energy resources used in the Romanian energy sector, 73.7% in 2011, taking into account the fuel imports. The objective of the article consists in analyzing all the processes along the coal and the natural gas life cycle in order to assess their overall environmental impact. Two energy technologies were analyzed, for each resource: the pulverized coal combustion with supra-critical parameters and CO2 capture unit and the natural gas combined cycle. Considering the functional unit of electricity production for 1 year, it was found that the natural gas combined cycle remains the more interesting energy technology from an environmental point of view. However, the pulverized coal with supra-critical parameters equipped with a CO2 capture unit has the lowest environmental impact on the climate change. The weakest point of the coal technology is its low efficiency.

Narciclasine,a novel topoisomerase I inhibitor,exhibited potent anti-cancer activity against cancer cells

DNA topoisomerases are essential nuclear enzymes in correcting topological DNA errors and maintaining DNA integrity.Topoisomerase inhibitors are a significant class of cancer chemotherapeutics with a definite curative effect.Natural products are a rich source of lead compounds for drug discovery,including anti-tumor drugs.In this study,we found that narciclasine(NCS),an amaryllidaceae alkaloid,is a novel inhibitor of topoisomerase I(topo I).Our data demonstrated that NCS inhibited topo I activity and reversed its unwinding effect on p-HOT DNA substrate.However,it had no obvious effect on topo II activity.The molecular mechanism of NCS inhibited topo I showed that NCS did not stabilize topo-DNA covalent complexes in cells,indicating that NCS is not a topo I poison.A blind docking result showed that NCS could bind to topo I,suggesting that NCS might be a topo I suppressor.Additionally,NCS exhibited a potent anti-proliferation effect in various cancer cells.NCS arrested the cell cycle at G_(2)/M phase and induced cell apoptosis.Our study reveals the antitumor mechanisms of NCS and provides a good foundation for the development of anti-cancer drugs based on topo I inhibition.

焦炉煤气脱碳法及甲烷化法制液化天然气的生命周期环境影响分析

作为焦化副产品,焦炉煤气富含氢气和甲烷,采用焦炉煤气制液化天然气(LNG)已成为当前焦炉煤气利用的主要途径之一。为系统评估焦炉煤气制LNG工艺的能源消耗和环境影响,尤其是碳排放,本文采用生命周期评价方法对脱碳法和甲烷化法两种焦炉煤气制LNG工艺进行系统评价。结果表明,无论采用哪种方法,LNG生产阶段均为焦炉煤气制LNG工艺生命周期环境负荷的控制阶段;在脱碳法工艺中,中压蒸汽是环境影响贡献的关键物质,可通过干熄焦回收红焦余热副产蒸汽补充LNG生产消耗来降低环境负荷;在甲烷化工艺中,电力为主要贡献物质,在碳排放中占比41.09%,若采用可再生能源电力(太阳能发电、风电、水电)替代后环境影响显著降低;相比于脱碳法,采用甲烷化工艺环境性能更优,主要源于甲烷增产优势。本文研究结果可从生命周期角度为焦化行业焦炉煤气的综合利用提供理论支持。

引燃柴油量对双燃料发动机循环变动的影响

为了降低重型高压共轨柴油机燃用LNG-柴油的燃烧循环变动,优化引燃柴油量控制,通过双燃料发动机试验台架,研究了在最大转矩转速1600r/min,功率输出为73kW工况下,随引燃柴油喷油量的增加,峰值压力、峰值压力升高率、平均指示压力循环变动的变化趋势。研究结果表明,随引燃柴油量的增加,双燃料发动机的峰值压力、峰值压力升高率和平均指示压力的循环变动趋势相同,它们的均值均增大,标准差减小,循环分布集中,循环变动系数降低。在不导致爆震燃烧的前提下,适当增大引燃柴油量,能够改善双燃料发动机的燃烧稳定性。

冻融循环作用下天然浮石混凝土孔隙结构演变特征

采用核磁共振技术,对冻融循环后的LC20和LC30强度等级的天然浮石混凝土进行孔隙结构损伤特性研究,得到两种强度等级的天然浮石混凝土不同冻融循环次数的孔隙度、横向弛豫时间T_(2)谱分布及孔径分布。结果表明:随着冻融循环次数的增加,天然浮石混凝土的孔隙度先经历一段比较平缓的阶段,出现“拐点”后便呈现上升趋势,LC20和LC30天然浮石混凝土在0~25次冻融过程中没有发生损伤,在冻融循环次数100次和150次时,出现大尺寸孔隙中填充了部分小颗粒现象;两种强度等级天然浮石混凝土在冻融环境下,孔隙占比规律均为多害孔>少害孔>无害孔>有害孔,变化范围最大的是多害孔。

基于双级节流制冷循环的天然气液化工艺模拟与优化

液化天然气以其安全可靠、汽化潜热高、环境污染小等特点,在天然气贸易中占据重要位置,但天然气液化工艺系统功耗大以及液化成本较高等问题仍然存在。为此,基于2个双级节流制冷循环的天然气液化工艺系统,采用Aspen HYSYS软件,以比功耗、㶲效率、液化率和总成本作为评价指标,分析了关键参数对系统性能的影响;然后对2个系统进行了单目标和多目标优化,确定了系统的最优运行工况;最后对2个系统的最优性能进行对比,并采用LINMAP与TOPSIS方法对Pareto前沿进行决策,在最优工况下对系统设备进行了㶲分析。研究结果表明:①节流阀V1、V3、V4的节流压力增大,或乙烯质量流量增大,均会使系统比功耗先减后增;单目标优化结果显示系统B性能优于系统A;②采用LINMAP与TOPSIS方法对Pareto前沿的决策结果有所差别,基于LINMAP方法的决策结果表明,系统B的总成本优于系统A,系统A的比功耗和㶲效率更优,综合性能更好;③基于TOPSIS方法的决策结果表明,系统A的比功耗优于系统B,系统B的㶲效率和总成本更优,综合性能更好;④㶲分析结果显示,节流阀及换热器的㶲损较大。结论认为,开展双级节流制冷循环天然气液化工艺研究,对其进行参数分析和优化,能够为天然气液化工艺设计创新提供借鉴,将有助于天然气液化行业的高质量发展。

玄武岩纤维混凝土抗硫酸盐侵蚀性能研究

为探究掺玄武岩纤维混凝土抗硫酸盐侵蚀性能,在混凝土试件中分别掺入体积掺量为0、0.1%、0.2%、0.3%的玄武岩纤维,以试件的外观、质量损失率和抗压强度为主要评价指标,进行了不同侵蚀环境下玄武岩纤维混凝土的抗硫酸盐侵蚀性能试验研究。研究结果表明:体积掺量为0.2%的试件在质量损失率、抗压强度方面表现最佳,而体积掺量为0.1%的试件抗折强度增幅最大;干湿循环条件下试件的外观、质量和抗压强度波动幅度较自然侵蚀环境下更大,且干湿周期越短侵蚀程度越严重;试件的微观结构分析发现,侵蚀前混凝土试件内部因水泥水化作用,存在少量C-S-H(水化硅酸钙)、Ca(OH)_(2)等水化产物,掺入玄武岩纤维后使混凝土内部黏结十分紧密,试件内部裂缝发育较缓,减少了侵蚀产物的生成,一定程度上提高了混凝土的力学性能。

中国共产党跳出治乱兴衰历史周期率两个答案中的人民性思想

作为历经百年风雨而风华正茂的马克思主义政党,中国共产党成功的一个重要密码就在于将人民性思想体现在治国理政的全过程中,跳出治乱兴衰历史周期率的两个答案就是一个典型范例。从“民主新路”到“自我革命”,是中国共产党在承袭马克思主义人民观、借鉴中国传统民本思想和总结党长期发展经验的基础上,在带领人民实现站起来、富起来到强起来的进程中,对中国共产党实际发展的积极回应,两个答案在价值追求、品质体现、目标导向等方面有着共同特质。新征程上,必须在“变”与“不变”中深化对人民性的理解、在强化制度建设中促使人民性原则落地生根、在良好的党群关系中有效助推党的自我革命,才能更好地理解这两个答案中坚持人民性思想的意义,更好地践行“两个答案”。

关中奶山羊发情期不同时段宫颈阴道粘液非靶向代谢组学比较分析研究

为了揭示关中奶山羊自然发情状态下发情期生殖道代谢特征,探索关中奶山羊发情期特异性化学信号,为精准发情鉴定和适时人工授精等繁殖工作提供代谢机制层面的理论依据,以3只2~3岁经产母羊为研究对象,采集关中奶山羊发情期0~12 h(A组),12~24 h(B组),24~36 h(C组)的宫颈阴道粘液,采用气相色谱-质谱法(GC-MS)测定关中奶山羊发情期宫颈阴道粘液中的代谢产物。结果显示,来自发情期不同时段的关中奶山羊宫颈阴道粘液中共检出221种不同的代谢产物,其主要分类是碳水化合物、脂质、氨基酸、核苷酸、异生素、辅助因子和维生素、肽类、能量等;0~12 h VS 12~24 h的差异代谢物有6种,12~24 h VS 24~36 h的差异代谢物有3种,0~12 h VS 24~36 h的差异代谢物有14种;这些差异代谢物主要富集在半乳糖代谢、碳水化合物消化吸收、矿物质吸收、甘油酯代谢、ABC蛋白转运、嘧啶代谢等通路上。

功能化脂质体及其在植物源天然产物递送中的应用

植物源天然产物具有广泛的药理特性,在药物发现中占据关键地位,同时以植物膳食补充剂的形式满足人体营养需求。植物源天然产物功效强大,但普遍存在溶解性低、稳定性差、缺乏靶向性、有毒副作用、有特殊气味等限制因素,为临床药物转化带来了挑战。近年来,纳米技术的发展为植物源天然产物的应用提供了新途径。其中,脂质体是一种由两亲性物质合成的双分子层纳米囊泡,具有高载药量、稳定性强等优势。与其他纳米颗粒相比,脂质体易于制备和扩展,它的扩展基于脂质体能被灵活修饰的表面特性。通过在脂质体表面修饰具备不同功能的元件可以使脂质体功能化,这些功能体现在靶向递送、药物控释、局部释放、改善药代动力学等。使用不同类型的功能化脂质体负载植物源天然产物不仅可以增强天然产物的稳定性、提高靶向性、减少副作用,还可以掩盖天然产物的刺激性气味,提升大众的接受度。本综述围绕当前植物源天然产物面临的典型问题,结合功能化脂质体在其中的具体应用做出总结。此外,本文还将回顾功能化脂质体进入临床治疗所面临的机遇和挑战,并探讨克服这些问题的机会,以期更好地实现植物纳米药物的精准控制,为相关领域研究人员及相关产业工作人员提供思路与启发。

枯竭气藏型储气库多周期损耗计算方法及其应用

地下储气库在生产运行过程中不可避免地会产生天然气损耗。目前对储气库气体损耗的研究仅停留在定性描述阶段,无法满足储气库经济性定量评价的要求。结合清单分析理论和注采机理实验,针对地下储气库注采过程中存在的微渗漏、溶解扩散、异常漏气和宏观漏气现象,建立了天然气损耗评价数学模型,对地下储气库气体损耗进行定量评价。结果表明:宏观驱替过程中的气体损耗是储气库气体损耗的主要组成部分,随着注采周期的增加而减小;在此基础上,建立了储气库型储气库天然气损耗定量评价方法,并以中原油田某地下储气库天然气损耗计算结果为例,利用该方法核算了该储气库自建库以来的各部分损耗情况并制定了降低损耗的技术对策。依托该计算方法可合理制定降低储气库天然气损耗政策,提供泄漏风险预警,提高储气库经济效益和注采安全性。

基于“自然—社会”二元水循环的流域综合治理模式——以湖北省枝江市“五水共建”为例

以水为脉络开展国土空间治理逐渐成为生态文明时代的关注重点。流域治理逐步从关注水的自然资源属性向结合社会经济发展的综合治理模式转变。在总结各地多种“多水共治”模式的基础上,提出流域综合治理应聚焦于“自然—社会”二元水循环所涉及的内涵,根据自然循环产生的防御需求与生态作用、社会循环产生的环境影响与经济文化属性,提出水安全、水环境、水生态、水景观、水文化“五水共建”的治理模式,并以湖北省枝江市为例,提出“五水共建”的总体思路与规划方案。