气藏平均地层压力跟踪计算新方法

平均地层压力是产能评价和动态分析的基础，准确、快速获取平均地层压力对高效开发气藏意义重大。基于地层压力随时间变化的规律，分析了平均地层压力的变化规律。研究结果表明：平均地层压力等效点仅随时间发生改变，平均地层压力的下降速率等于或者近似等于井底流压的下降速率。从封闭弹性驱动气藏的物质平衡方程出发，考虑偏差系数和井底流压随平均地层压力的变化，推导建立了平均地层压力跟踪计算新方法，根据生产数据可迭代计算平均地层压力。方法验证结果显示，采气速度和采出程度共同影响模型的计算结果。应用实例表明，跟踪计算法与压力恢复试井和物质平衡法之间的相对误差均较小，满足工程计算精度要求，且跟踪计算法不需依托生产测试数据，节约了测试费用，避免了测试占产。     

Theoretical study on a kind of cyclization mechanism of boron trichloride and hexamethyldisilazane to form the borazine ring for SiBCN ceramics precursor

Borazine rings act as a pivotal part in siliconboroncarbonitride ceramics (SiBCN) for high-temperature stability and great resistance to crystallization. A detailed investigation of the ring formation mechanism will guide the design and synthesis of SiBCN to meet application requirements under extreme conditions. Boron trichloride (BCl₃) and hexamethyldisilazane (HN(SiMe₃)₂) are common raw materials for the synthesis of precursors for SiBCN. In this paper, quantum chemical calculation was used to study the cyclization reaction mechanism between BCl₃ and HN(SiMe₃)₂ to form trichloroborazine (TCBZ) at the MP2/6-31G (d,p) level of theory. We discussed the structure properties, reaction pathways, energy barriers, reaction rates, and other aspects in detail. The results show that BCl₃ and HN(SiMe₃)₂ alternately participate in the reaction process, accompanied by the release of trimethylchlorosilane (TMCS), and that the entire reaction shows an absolute advantage in terms of energy. In the Step by step reaction, lower reaction barriers are formed due to the introduction of BCl₃ with more heat released compared to that for the introduction of HN(SiMe₃)₂. The final single-molecule cyclization and TMCS elimination steps are found to be faster compared to all previous bimolecular reactions.     

Responses to comments on the paper “two-dimensional Sc2C: A reversible and high capacity hydrogen storage material predicted by first-principles calculations”

A recent commentary by Santhosh and Ravindran on our paper (Int. J. Hydrogen Energy 2014, 39:10,606) demonstrated that the interaction between H₂ and MXene (Sc₂C and Ti₂C) phases are not Kubas-type and should be of weak physisorption, and thus made a conclusion that 2D Sc₂C and Ti₂C are not suitable for practical hydrogen storage applications. In this responses, we recalculated hydrogen adsorption on 2D Sc₂C and Ti₂C by using different exchange-correlation functionals. And based on the calculated results, bare MXenes (especially the Ti₂C) are suitable as hydrogen storage materials at temperatures of several tens degrees lower than room temperature. And the hydrogen adsorptions on the MXenes terminated with oxygen group were also investigated. Among the Ti₂C, Sc₂C and their oxygen-functional counterparts, the binding energy of H₂ on Sc₂CO₂ surface is the closest to the ideal range of 0.16–0.42 eV/H₂ at ambient conditions, and thus the Sc₂C with oxygen group is expected to be more suitable as hydrogen storage materials.     

Atomic-level insights into the modification mechanism of Fe (III) ion on smithsonite (1 0 1) surface from DFT calculation

Fe(III) ion can strongly inhibit the sulphidation amine flotation of smithsonite. However, its modification mechanism on smithsonite surface is still obscure. In this work, a systematic study of the modification of Fe(III) ion on smithsonite (1 0 1) surface was performed using DFT calculation. The optimal number of H₂O ligands for Fe(III) ion hydrates in aqueous conditions was probed, and [Fe(OH)₂(H₂O)₄]⁺ and [Fe(OH)₄]^? were identified as the major modification species, then their adsorption and bonding mechanisms were further revealed by analyzing the frontier orbitals, density of state, Mulliken population, and electron density. The calculated adsorption structures were consistent with the former experiment, and we found the O site that bonded to the C atom on smithsonite surface was the most favorable position for [Fe(OH)₂(H₂O)₄]⁺ and [Fe(OH)₄]^? adsorptions. Besides, their adsorption mechanisms on smithsonite surface were principally due to the combined effect of FeO bond and hydrogen bonding. Simultaneously, hydrogen bonding greatly enhanced the stability of the adsorption structures. Moreover, the dominant orbital contribution for the bonding of FeO was primarily due to the orbital hybridization between Fe 3d and O 2p orbitals. This work can help in deeper understanding of the depression of Fe(III) ion on the sulphidation amine flotation of smithsonite.     

Hydrogen release mechanisms of MgH2 over NiN4-embedded graphene nanosheet: First-principles calculations

In this study, first-principles calculations were performed to investigate the catalytic effect of NiN4-G on the dehydrogenation of MgH₂. Side-on MgH₂ can be adsorbed stably on the NiN4-G monolayer and is preferentially adsorbed on the NiN4 site compared with the graphene site. The hydrogen desorption process, in which MgH₂ dissociated to the Mg atom on the NiN4 site or graphene site and an H₂ molecule in the vacuum, should overcome lower barriers than pure MgH₂. This is because the corresponding Mg–H bond is weakened owing to the electron transfer between the Mg atom and the substrate. The hydrogen desorption enthalpies of the (MgH₂)₅ cluster on the NiN4 active and graphene sites are significantly smaller (0.11 eV and 1.50 eV, respectively) when H2+H2 is released from the cluster compared with those of the undoped MgH₂ cluster (2.48 eV). Therefore, the NiN4-G monolayer can provide the double effect of the NiN4 active and graphene sites on improving the dehydrogenation performance of MgH₂.     

Degradation analysis of the core components of metal plate proton exchange membrane fuel cell stack under dynamic load cycles

The durability of metal plate proton exchange membrane fuel cell (PEMFC) stack is still an important factor that hinders its large-scale commercial application. In this paper, we have conducted a 1000 h durability test on a 1 kW metal plate PEMFC stack, and explored the degradation of the core components. After 1000 h of dynamic load cycles, the voltage decay percentage of the stack under the current densities of 1000 mA cm^?2 is 5.67%. By analyzing the scanning electron microscopy (SEM) images, the surfaces of the metal plates are contaminated locally by organic matter precipitated from the membrane electrode assembly (MEA). The SEM images of the catalyst coated membrane (CCM) cross section indicate that the MEA has undergone severe degradation, including the agglomeration of the catalyst layer, and the thinning and perforation of the PEM. These are the main factors that cause the rapid increase in hydrogen crossover flow rate and performance decay of the PEMFC stack.     

Nanoarchitectonics of CdS/ZnSnO3 heterostructures for Z-Scheme mediated directional transfer of photo-generated charges with enhanced photocatalytic performance

The construction of heterostructure is an effective strategy to synergetically couple wide-band-gap with the narrow-band-gap semiconductor with a mediate optical property and charge transfer capability. Herein, the Z-Scheme CdS/ZnSnO₃ (CdS/ZSO) heterostructures were constructed by anchoring CdS nanoparticles on the surface of double-shell hollow cubic ZnSnO₃ via the hydrothermal method. The direct recombination of excited electrons in the conduction band (CB) of ZSO and holes in the valence band (VB) of CdS via d-p conjugation at the interface greatly accelerated the internal electric field (IEF). The transfer mode follows the Z-Scheme mechanism, where CdS/ZSO synergistically facilitates the efficient charges transfer from CdS to ZnSnO₃ through the intimate interface. Here, ZnSnO₃ and CdS serve as an oxidation photocatalyst (OP) and reduction photocatalyst (RP), respectively. Thus, it can promote synergistically the oxidation half-reaction and reduction half-reaction of H₂ evolution. The density-functional theory (DFT) calculation further confirms the charges transfer from CdS to ZnSnO₃. The hydrogen evolution of 5% CdS/ZSO heterostructure reached 1167.3 μmol g^?1, which was about 8 and 3 folds high compared to pristine ZSO (141.9 μmol g^?1) and CdS (315.5 μmol g^?1), during 3 h of reaction respectively. Furthermore, the CdS/ZSO heterostructures could suppress the photo corrosion of CdS, resulting in its high stability. This work is expected to enlighten the rational design of heterostructure for OP and RP to promote the hybrid heterostructures photocatalytic H₂ evolution.     

箱形横梁的水压爆破拆除

某电影院大厅内钢筋混凝土箱形横梁长25m,断面尺寸1 6m×2 4m,用水压爆破拆除。通过梁的受力分析得知,为避免横梁的挠度过大,在吊梁拆除后必须另补支撑,以确保水压爆破正常进行。文中对水压爆破炸药用量的计算公式进行了比较和简评。在参考计算结果和考虑厅内环境的基础上,并结合以往水压爆破工程的经验,确定了合理、有效的药量,保证了主体结构的绝对安全。     

“灰绿”协同措施对银川市合流制溢流污染的影响EI北大核心CSCD

针对合流制管网系统在雨天溢流污染严重,造成城市水体黑臭现象的问题,以银川市某高密度城区合流制管网系统为例,基于SWMM模型,在短历时设计降雨和长历时设计降雨两种条件下,模拟分析了合流制溢流(CSO)调蓄池、雨污管道混错接改造、绿化带海绵化改造等“灰绿”协同措施对CSO污染的影响。结果表明:CSO调蓄池、雨污管道混错接改造、绿化带海绵化改造及“灰绿”措施结合4种方案在短历时、长历时设计降雨条件下,随着降水量的增加,溢流水量及溢流污染物负荷均增加,溢流削减率均逐渐减小,其中“灰绿”措施结合方案对溢流污染的削减效果最为显著;重现期小于5 a时,溢流水量削减率与溢流污染物负荷削减率基本达到80%;降雨条件为中雨时,污染物负荷削减率基本达到75%;重现期为20 a时,溢流水量削减率及TSS、COD、TP、NH^(+)_(4)-N负荷削减率分别达到64%、70%、70%、70%、70%;降雨条件为大雨时,溢流水量削减率及TSS、COD、TP、NH^(+)_(4)-N负荷削减率分别达到28%、32%、26%、31%、33%。     

基于跨临界CO2热泵的茶叶生产能源系统负荷削减潜力

乡村产业中的化石能源设备逐渐被电能技术替代，引起了乡村负荷波动增大、部分时段产生集中高负荷的问题。为了解决以上问题，将低品位清洁能源应用至乡村的茶叶生产中，针对烘茶全过程的工艺要求提出了跨临界CO₂热泵烘茶技术；并以某茶叶生产乡村为对象，对其代表台区的全年日用电量及产茶日负荷进行了分析，得出采用CO₂热泵烘茶后其负荷得到大幅度削减，整体可降低至原负荷的39.6%~46.8%，峰值负荷与平时负荷的比值由原本的13.6降至5.4~6.2。跨临界CO₂热泵应用至农产品生产中可有效缓解乡村供电压力。