人类从应对气候变化走向低碳经济

从能源存量与增量的客观现实和人类开发利用能源的客观规律角度,论述人类走向低碳经济的必然性;分析发展中国家面临低碳经济路径突破困境,以及发达国家拥有低碳经济的诸多优势;考察中国高碳能源结构和高碳排放强度,从建立资源节约型、环境友好型社会目标出发,中国对低碳经济应持开放积极立场,采取有效措施推进低碳经济。     

API standard 521 guidance on mixing of hot/cold liquids and prevention of superheat limit explosions

American Petroleum Institute (API) standards and recommended practices have identified inadvertent mixing of hot and cold liquids as a potential cause for equipment overpressure since 1955. The limited guidance has been informative but provides minimal if any details on conditions that could cause an overpressure and its potential severity. Therefore, the user must interpret how and when to prevent and/or mitigate the scenario. This guidance has changed little over the years. In June 2020, API published the 7th Edition of API Standard 521 which now provides specific guidance as to conditions whereby pressure relief devices can be considered for protection and conditions where prevention remains as the only recourse. This paper discusses the basis for the revised guidance in API Standard 521 and includes supplemental guidance.     

Testing of dust clouds for the electrostatic-spark ignition hazard in industry. Need for a modified approach?

Current standard test methods for electric-spark minimum ignition energies (MIEs) of dust clouds in air require that a series inductance of at least 1–2 mH be included in the electric-spark discharge circuit. The reason is to prolong the spark discharge duration and thus minimize the spark energy required for ignition. However, when assessing the minimum electrostatic energy ½CU² for dust cloud ignition by accidental electrostatic-spark discharges, current testing standards require that the series inductance of at least 1–2 mH be removed from the spark discharge circuit. No other changes of apparatus and test procedure are required. The present paper questions whether this simple approach is always adequate. The reason is that in practice in industry accidental electrostatic-spark discharge circuits may contain large ohmic resistances due to corrosion, poor electrical grounding connections, poorly electrically conducting construction materials etc. The result is increased spark discharge durations and reduced mechanical disturbance of the dust cloud by the blast wave emitted by the spark. Therefore, testing for minimum ½CU² for ignition by accidental electrostatic spark discharges may not only require removal of the series inductance of 1–2 mH from the standard MIE spark discharge circuit. Additional tests may be needed with one or more quite large series resistances R_s inserted into the spark discharge circuit. The present paper proposes a modified standard test procedure for measurement of the minimum electrostatic-spark ignition energy of dust clouds that accounts for these effects.     

冻融循环作用下受荷砂岩的能量演化与破碎分形特征*

为研究冻融循环作用对岩石力学特性的影响,对砂岩试件依次进行冻融循环处理、单轴压缩实验以及筛分实验,分析不同冻融循环次数下砂岩试件加载过程中的能量演化、分配规律以及破坏后碎屑尺度分布的分形特征,并讨论冻融循环作用的影响效应。结果表明:随着冻融循环次数的增加,单轴抗压强度和弹性模量均呈指数衰减的趋势,峰值应力点对应的耗散应变能及其与总能量比值表现出类似的变化规律。这些试件破坏后的碎屑尺度分布具有分形特征,分形维数在2.50~2.61之间。数据拟合进一步表明冻融循环作用下耗散应变能与分形维数之间呈显著的线性正相关关系,这是因为冻融循环次数越大使得砂岩试件的抗压强度越小,破坏所需的耗散应变能越小,试件破碎程度越不严重,导致相应的分形维数越小。     

A simple formula for calculating the ionization potential of two-electron ions

The ionization potential of one-electron ions can be calculated from a well-known simple equation, but no such equation has been available for calculating the ionization potential of multi-electron ions. I report here an equation that accurately gives the ionization potential of helium-like (i.e., two-electron) ions as a function of the atomic number, the relative difference from experimental values being below 1% for all ions for which reliable experimental data were found (Z = 3–29). The equation also predicts the stability of the negative hydrogen ion (the hydride ion), H⁻, although with twice too large a value for the ionization potential.     

Cosmic vacuum energy decay and creation of cosmic matter

In the more recent literature on cosmological evolutions of the universe, the cosmic vacuum energy has become a nonrenouncable ingredient. The cosmological constant Λ, first invented by Einstein, but later also rejected by him, presently experiences an astonishing revival. Interestingly enough, it acts like a constant vacuum energy density would also do. Namely, it has an accelerating action on cosmic dynamics, without which, as it appears, presently obtained cosmological data cannot be conciliated with theory. As we are going to show in this review, however, the concept of a constant vacuum energy density is unsatisfactory for very basic reasons because it would claim for a physical reality that acts upon spacetime and matter dynamics without itself being acted upon by spacetime or matter.     

Wolfgang Priester: from the big bounce to the $\Lambda$-dominated universe

Wolfgang Priester (1924–2005) was one of Germany’s most versatile and quixotic astrophysicists, reinventing himself successively as a radio astronomer, space physicist and cosmologist, and making a lasting impact on each field. We focus in this personal account on his contributions to cosmology, where he will be most remembered for his association with quasars, his promotion of the idea of a nonsingular “big bounce” at the beginning of the current expansionary phase, and his recognition of the importance of dark energy (Einstein’s cosmological constant Λ) well before this became the standard paradigm in cosmology. In memoriam Wolfgang Priester, 22 April 1924 – 9 July 2005     

Hydrogen and transportation: alternative scenarios

If hydrogen (H₂) is to significantly reduce greenhouse gas emissions and oil use, it needs to displace conventional transport fuels and be produced in ways that do not generate significant greenhouse gas emissions. This paper analyses alternative ways H₂ can be produced, transported and used to achieve these goals. Several H₂ scenarios are developed and compared to each other. In addition, other technology options to achieve these goals are analyzed. A full fuel cycle analysis is used to compare the energy use and carbon (C) emissions of different fuel and vehicle strategies. Fuel and vehicle costs are presented as well as cost-effectiveness estimates. Lowest hydrogen fuel costs are achieved using fossil fuels with carbon capture and storage. The fuel supply cost for a H₂ fuel cell car would be close to those for an advanced gasoline car, once a large-scale supply system has been established. Biomass, wind, nuclear and solar sources are estimated to be considerably more expensive. However fuel cells cost much more than combustion engines. When vehicle costs are considered, climate policy incentives are probably insufficient to achieve a switch to H₂. The carbon dioxide (CO₂) mitigation cost would amount to several hundred US$ per ton of CO₂. Energy security goals and the eventual need to stabilize greenhouse gas concentrations could be sufficient. Nonetheless, substantial development of related technologies, such as C capture and storage will be needed. Significant H₂ use will also require substantial market intervention during a transition period when there are too few vehicles to motivate widely available H₂ refueling.

用于湿法净化黑烟表面活性剂筛选的数学模型研究

湿法净化燃煤窑炉中的黑烟,关键在于表面活性剂对炭黑的润湿、增溶和降低表面张力作用.根据研究筛选的数学模型,计算AEO-9和SDBS混合表面活性剂溶液的亲水亲油平衡值HLB、临界胶束浓度CMC与胶束形成吉布斯自由能ΔG0mf.通过实验测得不同配比AEO-9和SDBS溶液的CMC和处于该CMC时黑烟的去除效率η,分析混合溶液中HLB、CMC、ΔG0mf与η的关系,建立新的数学模型.结果表明,理论CMC与实测CMC吻合度较好;HLB与ln[CMC]线性相关;ΔG0mf与η存在二次函数关系.降低CMC可以有效增大HLB,增加溶解度,减小形成胶束的吉布斯自由能,降低表面张力,使形成胶束的反应更容易自发进行,有效提高黑烟去除效率.     

应用多元线性溶剂化能关系研究有机膨润土的吸附特征

以十六烷基三甲基溴化铵(CTMAB)制备的有机膨润土为代表,设置有机膨润土中CTMAB的负载量为1.0倍的阳离子交换量(CEC),测试了其吸附酚类、胺类、硝基类等25种有机物的有机碳标化的吸附系数(K∝)值.在此基础上,运用多元线性回归方法得到了有机膨润土吸附有机物的多元线性溶剂化能关系(LSER)模型,以明确各种作用...