Strategies to achieve effective nitrogen activation

Ammonia serves as a crucial chemical raw material and hydrogen energy carrier.Aqueous electrocatalytic nitrogen reduction reaction(NRR),powered by renewable energy,has attracted tremendous interest during the past few years.Although some achievements have been revealed in aqueous NRR,significant challenges have also been identified.The activity and selectivity are fundamentally limited by nitrogen activation and competitive hydrogen evolution.This review focuses on the hurdles of nitrogen activation and delves into complementary strategies,including materials design and system optimization(reactor,electrolyte,and mediator).Then,it introduces advanced interdisciplinary technologies that have recently emerged for nitrogen activation using high-energy physics such as plasma and triboelectrification.With a better understanding of the corresponding reaction mechanisms in the coming years,these technologies have the potential to be extended in further applications.This review provides further insight into the reaction mechanisms of selectivity and stability of different reaction systems.We then recommend a rigorous and detailed protocol for investigating NRR performance and also highlight several potential research directions in this exciting field,coupling with advanced interdisciplinary applications,in situ/operando characterizations,and theoretical calculations.

A transient model integrating the nanoconfinement effect and pore structure characteristics of oil transport through nanopores

Understanding the integrated transport behavior of oil in shale nanopores is critical to efficient shale oil development. In this paper, based on the time-dependent Poiseuille flow momentum equation, we present a novel transient model to describe oil transport in unsteady and steady states. The model incorporates the effect of the critical shift density, apparent viscosity, slip length, and alkane property, as well as pore tortuosity and surface roughness. We evaluated our model through a comparison with other models, experiments, and molecular dynamics simulations. The results show that the development rates of the volume flows of C_(6)–C_(12) alkane confined in inorganic nanopores and C_(12) alkane confined in organic nanopores were faster than that of the corresponding bulk alkane. In addition, the critical drift density positively promoted the volume flow development rate in the unsteady state and negatively inhibited the mass flow rate in the steady state. This effect was clearest in pores with a smaller radius and lower-energy wall and in alkane with shorter chain lengths. Furthermore, both the nanoconfinement effect and pore structure determined whether the volume flow enhancement rate was greater than or less than 1. The rate increased or decreased with time and was controlled mainly by the nanoconfinement effect. Moreover, as the wall energy increased, the flow inhibition effect increased;as the carbon number of alkane increased, the flow promotion effect increased. The results indicate that the proposed model can accurately describe oil transport in shale nanopores.

骨水泥加长柄人工股骨头置换对高龄严重骨质疏松性股骨转子间骨折患者术后活动能力和生活质量的影响

目的探讨高龄严重骨质疏松性股骨转子间骨折患者采用骨水泥加长柄人工股骨头置换治疗对患者术后活动能力和生活质量的影响。方法选取2011年7月-2016年8月该院收治的50例高龄股骨转子间粉碎骨折患者资料做回顾性分析,根据医师建议以及患者意愿,分为对照组和治疗组。对照组22例采用股骨近端防旋髓内钉(PFNA)治疗,治疗组28例采用骨水泥加长柄人工股骨头置换治疗。比较两组手术一般情况,术后不同时间点Harris髋关节功能评分、术后并发症以及术后不同时间点健康调查简表(SF-36)评分。结果治疗组手术时间、切口长度与对照组比较,差异有统计学意义(P<0.05),治疗组长于对照组;治疗组术中出血量多于对照组,下床活动时间短于对照组,差异有统计学意义(P<0.05);两组术中输血量比较,差异无统计学意义(P>0.05);治疗组术后1、3、6个月Harris评分与对照组比较,差异有统计学意义(P<0.05),治疗组高于对照组,两组Harris评分在术后12个月比较,差异无统计学意义(P>0.05);治疗组并发症发病率为7.14%,对照组并发症发病率为27.27%,两组比较差异无统计学意义(P>0.05);治疗组术后3个月,SF-36量表各维度评分高于对照组,差异有统计学意义(P<0.05),术后12个月,SF-36量表各维度评分与对照组比较差异无统计学意义(P>0.05)。结论相对于PFNA,加长柄人工股骨头置换治疗可有效缩短患者下床活动时间,术后早期髋关节功能恢复较好,生活质量较高,对于伴有严重骨质疏松的高龄股骨转子间骨折患者而言是较优选择。

某混凝土结构爆裂的检测与加固

我国的工业蓬勃发展的同时,也产生了大量的固体废料,这些固体废料对环境造成了严重的污染,因此固体废料的综合再利用得到重视与思考,这些固体废料中粉煤灰和钢渣的一个主要用途是掺入混凝土中。混凝土中掺入粉煤灰可以提高混凝土的性能,亦可降低混凝土的成本。近年来掺入粉煤灰、钢渣等工业固体废料的混凝土得到普遍应用,这些固体废料未经预处理或预处理不充分,就会造成混凝土表面隆起、胀裂等现象。某项目竣工后,其地下车库顶板、墙柱混凝土表面出现大量鼓包、局部混凝土脱落现象。本文介绍了检测鉴定过程,对点状爆裂物质成分的检测和混凝土安定性的检测进行了阐述,对混凝土爆裂的原因进行了分析,并提出了经济可行的处理方案,对类似工程有一定的参考价值。

Chromium phosphide nanoparticles embedded in porous nitrogen-/phosphorus-doped carbon as efficient electrocatalysts for a nitrogen reduction reaction

The resource recovery of heavy metals from effluent has significant environmental implications and potential commercial value.Chromium phosphide nanoparticles embedded in a nitrogen-/phosphorus-doped porous carbon matrix(CrP/NPC)are synthesized via a consecutive Cr^(6+)leachate treatment and resource recovery process.Electrochemical testing shows that CrP/NPC shows excellent nitrogen reduction reaction(NRR)performance,which yields the highest NH_(3) production rate of 22.56μg h^(−1) mg^(−1)_(cat).and Faradaic efficiency(16.37%)at−0.5 V versus the reversible hydrogen electrode in a 0.05M Na_(2)SO_(4) aqueous solution,as well as robust catalytic stability.The isotopic experiments using ^(15)N^(2) as a nitrogen source confirm that the detected NH_(3) is derived from the NRR process.Finally,density functional theory(DFT)calculations show that the electron deficiency environment of the Cr site can significantly reduce the barrier of the NRR process and promote the formation of intermediate species.

Study on Expected Mature Age of Individual Ailanthus altissima

This study was conducted on the analytic tree and got the fitting empirical equation of tree growth,in which the tree growth rate was used as the variable and time as the independent variable.The arithmetical operation to the function got the mature age of tree growth,and the expected mature age of Ailanthus altissima was 21 a.In addition,the application as well as the research direction and matters needing attention were proposed.

Impact of Seven Valent Pneumococcal Conjugate Vaccine on Nasopharyngeal Carriage in Young Children in Okinawa, Japan

In Japan, the heptavalent pneumococcal conjugate vaccine (PCV7) became available in February 2010 and was subsidized by the national funding system from May 2011 in Okinawa, after which it was incorporated into the national immunization practice (NIP) in April 2013 using a 3 + 1 schedule for all infants. We conducted an annual survey in 2012 to determine the effect of PCV7 on nasopharyngeal colonization by pneumococcal serotypes and to analyze the risk factors for colonization in infants. Nasopharyngeal swabs for pneumococcal isolation and serotyping were obtained from infant 2 to 22 months of age before and after PCV7 immunization among 4 clinics in Okinawa, Japan. Between January 2012 and December 2012, nasopharyngeal swabs for bacterial cultures were obtained among 782 infants aged 2 to 22 months old and demographic data was obtained among 725 participant infants. Among the 725 evaluable infants, 193 pneumococcal strains were detected in 180 infants for an overall nasopharyngeal carriage of 24.8%. The main capsular serotypes isolated were 6C (16.1%), 19A (12.4%) and 15B (9.8%). Carriage of PCV7 serotypes accounted for 21.8% (42/193). The result of multivariate data analysis showed the pneumococcal carriage rate of non-PCV7 serotypes was significantly (P < 0.001) high in infant with siblings and daycare attendance. On the other hand, the result of multivariate data analysis showed that carriage rate of PCV7 serotype had only significantly high risk in infant with siblings and did not have a significant risk dependent on age and daycare attendance. Carriage PCV7 serotypes increased in the presence of other siblings, while PCV7 vaccination was shown to eliminate daycare attendance as a risk. The results of this study demonstrates that PCV7 vaccination decrease the overall nasopharyngeal carriage of PCV7 serotypes in vaccinated children including children at risk such as children attending day-care centers.

Maximizing Resilient Throughput in Peer-to-Peer Network

A unique challenge in P2P network is that the peer dynamics (departure or failure) cause unavoidable disruption to the downstream peers. While many works have been dedicated to consider fault resilience in peer selection, little understanding is achieved regarding the solvability and solution complexity of this problem from the optimization perspective. To this end, we propose an optimization framework based on the generalized flow theory. Key concepts introduced by this framework include resilience factor, resilience index, and generalized throughput, which collectively model the peer resilience in a probabilistic measure. Under this framework, we divide the domain of optimal peer selection along several dimensions including network topology, overlay organization, and the definition of resilience factor and generalized flow. Within each sub-problem, we focus on studying the problem complexity and finding optimal solutions. Simulation study is also performed to evaluate the effectiveness of our model and performance of the proposed algorithms.

Orientation controlled photogenerated carriers on selfsupporting CdS/Ni_(3)S_(2) paper toward photocatalytic hydrogen evolution and biomass upgrading

The appropriate regulation of band structure is an effective strategy in constructing efficient photocatalytic systems.Present photocatalytic system mainly employs powder photocatalysts,which makes their recovery reliant on expensive separation processes and severely limits their industrial application.Herein,we constructed a novel CdS/Ni_(3)S_(2)heterostructure using free-standing and flexible nickel fiber paper as the matrix.The regulated energy band structure achieves effective electron–hole separation.The as-synthesized flexible photocatalyst exhibits considerable photocatalytic activity toward the H_(2)evolution reaction under visible-light irradiation,with an H_(2)production rate of5.63μmol·cm^(-2)·h^(-1)(14.1 mmol·g^(-1)cat·h^(-1)according to the catalyst loading content).Additionally,the otherwisewasted excited holes simultaneously drive organic transformations to yield value-added organic products,thus markedly improving the photocatalytic H_(2)evolution rate.Such a photocatalytic system is scaled up further,where a self-supported 20 cm×25 cm sample achieves a champion H_(2)production rate of 60-80μmol·h^(-1)under practical sun irradiation.This newly developed self-supported photocatalyst produces opportunities for practical solar H2production with biomass upgrading.

Two-dimensional bifunctional electrocatalyst(Mo-NiFe-LDH)with multilevel structure for highly efficient overall water splitting

To effectively address energy challenges,it is crucial to explore efficient and stable bifunctional nonprecious metal catalysts.In this study,a Mo-doped nickeliron layered double hydroxide with flower-cluster architecture was successfully prepared by a one-step hydrothermal method,which demonstrated a good water splitting performance.After an appropriate amount of Mo doping,some lattice distortions in the material provided reactive sites for the adsorption and conversion of intermediates,thus optimising the charge distribution of the material.Moreover,the multidimensional void structures formed after doping had a larger specific surface area and accelerated the penetration of the electrolyte,which significantly improved the activity of the catalyst in alkaline media.At 10 mA·cm^(-2),the hydrogen and oxygen evolution overpotentials of Mo-doped nickel-iron double hydroxides(Mo-NiFe LDH/NF-0.2)were 167 and 220 mV,respectively,with an excellent durability up to 24 h.When the Mo-NiFe LDH/NF-0,2 catalyst was used as the cathode and anode of an electrolytic cell,the catalyst achieved a current density of 10 mA·cm^(-2)at an applied voltage of 1.643 V.This study provides a novel approach for designing excellent bifunctional electrocatalysts containing nonprecious metals.

压缩机润滑油雾滤芯过滤性能分析与改进研究

利用现场高压和实验室常压滤芯性能评价装置,对比了不同工况下的滤芯过滤性能,分析了液体物性和油雾浓度对滤芯过滤性能的影响规律,提出了滤芯改进方法并进行了效果验证。结果表明,由于气液相互作用改变,高压下滤芯过滤效率相比常压略低,但常压工况过滤性能变化规律能反映现场实际运行性能。与气体流量相比,液体黏度对中效滤芯的过滤效率影响更大,且滤芯在过滤高黏度液体时才会出现压降的显著上升。油雾浓度对中效滤芯的压降影响受液体黏度控制,高黏度时压降随油雾浓度升高而升高,但低黏度时压降基本不随油雾浓度变化。由于流量对液滴扩散捕集作用的影响,低流量时滤芯对高黏度液体的过滤效率随油雾浓度降低反而升高。通过调整滤芯内部的滤材组成及排布方式,可实现小尺寸液滴的高效捕集,对癸二酸二辛酯液滴的过滤效率相比原滤芯至少提升50%。研究结果对于指导天然气储运过程中滤芯性能提升与机理认识具有重要意义。

Green and large-scale production of ammonia:Laser-driven pyrolysis of nitrogen-enriched biomass

As a vital chemical,ammonia(NH3)plays an irreplaceable role in many fields such as chemical synthesis and energy storage.Green renewable biomass can be converted into biofuels,but its nitrogen resources are underused throughout.Laser-driven pyrolysis is envisaged to debuts as a bridge to connect them to realize the direct conversion from nitrogen-rich biomass into ammonia.The pulsed laser-induced local-transient thermal effect recognized the biological nitrogen resources conversion,such as cheap and plentiful yeasts,to small gaseous molecules and achieved spectacular ammonia production rate up to 260.4 mg/h,an order of magnitude higher performance than thermochemical ammonia synthesis.Simultaneously,the tiny hot point generated by a low-energy laser(20W)guarantees the whole ammonia synthesis reaction systemis in amild environment of low temperature and normal pressure.Additionally,the remaining solid residue after laser-driven pyrolysis also can be further exploited as a highly active catalyst for electrocatalytic nitrate reduction reaction(NIRR).

Emerging Internet of Things driven carbon nanotubes-based devices

Carbon nanotubes(CNTs)have attracted great attentions in the field of electronics,sensors,healthcare,and energy conversion.Such emerging applications have driven the carbon nanotube research in a rapid fashion.Indeed,the structure control over CNTs has inspired an intensive research vortex due to the high promises in electronic and optical device applications.Here,this in-depth review is anticipated to provide insights into the controllable synthesis and applications of high-quality CNTs.First,the general synthesis and post-purification of CNTs are briefly discussed.Then,the state-of-the-art electronic device applications are discussed,including field-effect transistors,gas sensors,DNA biosensors,and pressure gauges.Besides,the optical sensors are delivered based on the photoluminescence.In addition,energy applications of CNTs are discussed such as thermoelectric energy generators.Eventually,future opportunities are proposed for the Internet of Things(IoT)oriented sensors,data processing,and artificial intelligence.

Waste-yeast biomass as nitrogen/phosphorus sources and carbon template:Environment-friendly synthesis of N,P-Mo_(2)C nanoparticles on porous carbon matrix for efficient hydrogen evolution

Tailor-made advanced electrocatalysts with high active and stable for hydrogen evolution reaction(HER)play a key role in the development of hydrogen economy.Herein,a N,P-co-doped molybdenum carbide confined in porous carbon matrix(N,P-Mo_(2)C/NPC)with a hierarchical structure is prepared by a resources recovery process.The N,P-Mo_(2)C/NPC compound exhibits outstanding HER activity with a low overpotential of 84 mV to achieve 10 mA/cm^(2),and excellent stability in alkaline media.The electrochemical measurements confirm that the enhanced HER activity of N,P-Mo_(2)C/NPC is ascribe to the synergy of N,P-codoped and porous carbon matrix.Density functional theory calculations further reveal that the electron density of active sites on Mo_(2)C can be regulated by the N/P doping,leading to optimal H adsorption strength.In this work,the proof-of-concept resource utilization,a microorganism derived molybdenum carbide electrocatalyst for HER is fabricated,which may inaugurate a new way for designing electrocatalysts by the utilization of solid waste.

Review of different fault detection methods and their impact on pre-emptive VSC-HVDC dc protection performance

Multi-terminal voltage-sourced converters(VSC)high-voltage direct current(HVDC)transmission system is expected to play a vital role in future power systems.Compared with ac power transmission,dc transmission is more vulnerable to faults due to low dc-side impedances and sensitive power electronics in the converters.Dc protection issues must be tackled before any multi-terminal VSC-HVDC grid can be built.The multi-terminal VSC-HVDC system is studied in detail using switching models for two-level converters,detailed equivalent models for the modular multi-level converters,detailed hybrid circuit breaker switching models and frequency-dependent phase models for dc cables.Using such high-fidelity system models,a systematic study of HVDC fault protection methodologies in more detail than previous studies is conducted.This is the first comprehensive study that includes pre-emptive circuit breaker operation.The results presented in this study underline the benefits of such a detailed treatment of the breaker,and of considering it as part of a fast power electronics system rather than isolated dc equipment.The study identifies the best existing fault detection method and tests it extensively.In order to further improve post-fault system recovery response,which is a key but often neglected part of previous studies,a novel bump-less transfer control has been implemented in the converters.