Electrochemical hydrogen compression and purification versus competing technologies: Part Ⅱ. Challenges in electrocatalysis

Hydrogen will be at the basis of the World’s energy policy in forthcoming decades, owing to its decarbonized nature, at least when produced from renewables. For now, hydrogen is still essentially produced from fossil feedstock(and to a minor extent from biomass);in consequence the present hydrogen gas on the market is containing non-negligible amounts of impurities that prevent its immediate usage in specialty chemistry or as an energy carrier in fuel cells, e.g. in transportation applications(cars, buses, trains, boats, etc.) that gradually spread on the planet. For these purposes, hydrogen must be of sufficient purity but also sufficiently compressed(at high pressures, typically 70 MPa), rendering purification and compression steps unavoidable in the hydrogen cycle. As shown in the first part of this contribution "Electrochemical hydrogen compression and purification versus competing technologies: Part I. pros and cons", electrochemical hydrogen compressors(EHCs), which enable both hydrogen purification and compression, exhibit many theoretical(thermodynamic) and practical(kinetics) advantages over their mechanical counterparts. However, in order to be competitive, EHCs must operate in very intensive conditions(high current density and low cell voltage) that can only be reached if their core materials, e.g. the membrane and the electrodes/electrocatalysts, are optimized. This contribution will particularly focus on the properties electrocatalysts must exhibit to be used in EHCs: they shall promote(very) fast hydrogen oxidation reaction(HOR) in presence of impurities, which implies that they are(very) tolerant to poisons as well. This consists of a prerequisite for the operation of the anode of an EHC used for the purification-compression of hydrogen, and the materials developed for poison-tolerance in the vast literature on low-temperature fuel cells, may not always satisfy these two criteria, as this contribution will review.

Electrochemical hydrogen compression and purification versus competing technologies: Part Ⅰ. Pros and cons

It is undisputed that hydrogen will play a great role in our future energetic mix, because it enables the storage of renewable electricity(power-to-H2) and the reversible conversion into electricity in fuel cell, not to speak of its wide use in the(petro)chemical industry. Whereas in these applications, pure hydrogen is required, today’s hydrogen production is still largely based on fossil fuels and can therefore not be considered pure. Therefore, purification of hydrogen is mandatory, at a large scale. In addition, hydrogen being the lightest gas, its volumetric energy content is well-below its competing fuels, unless it is compressed at high pressures(typically 70 MPa), making compression unavoidable as well. This contribution will detail the means available today for both purification and for compression of hydrogen. It will show that among the available technologies, the electrochemical hydrogen compressor(EHC), which also enables hydrogen purification, has numerous advantages compared to the classical technologies currently used at the industrial scale. EHC has their thermodynamic and operational advantages, but also their ease of use. However, the deployment of EHCs will be viable only if they reach sufficient performances, which implies some specifications that their base materials should stick to. The present contribution will detail these specifications.

Timescales of interface-coupled dissolution-precipitation reactions oncarbonates

In the Earth's upper crust, where aqueous fluids can circulate freely, most mineral transformations are controlled by the coupling between the dissolution of a mineral that releases chemical species into the fluid and precipitation of new minerals that contain some of the released species in their crystal structure, the coupled process being driven by a reduction of the total free-energy of the system. Such coupled dissolution-precipitation processes occur at the fluid-mineral interface where the chemical gradients are highest and heterogeneous nucleation can be promoted, therefore controlling the growth kinetics of the new minerals. Time-lapse nanoscale imaging using Atomic Force Microscopy(AFM) can monitor the whole coupled process under in situ conditions and allow identifying the time scales involved and the controlling parameters. We have performed a series of experiments on carbonate minerals(calcite, siderite, dolomite and magnesite) where dissolution of the carbonate and precipitation of a new mineral was imaged and followed through time. In the presence of various species in the reacting fluid(e. g. antimony, selenium, arsenic, phosphate), the calcium released during calcite dissolution binds with these species to form new minerals that sequester these hazardous species in the form of a stable solid phase. For siderite, the coupling involves the release of Fe^(2+) ions that subsequently become oxidized and then precipitate in the form of FeIIIoxyhydroxides. For dolomite and magnesite,dissolution in the presence of pure water(undersaturated with any possible phase) results in the immediate precipitation of hydrated Mg-carbonate phases. In all these systems, dissolution and precipitation are coupled and occur directly in a boundary layer at the carbonate surface. Scaling arguments demonstrate that the thickness of this boundary layer is controlled by the rate of carbonate dissolution,the equilibrium concentration of the precipitates and the kinetics of diffusion of species in a boundary layer. From these parameters a characteristic time scale and a characteristic length scale of the boundary layer can be derived. This boundary layer grows with time and never reaches a steady state thickness as long as dissolution of the carbonate is faster than precipitation of the new mineral. At ambient temperature, the surface reactions of these dissolving carbonates occur on time-scales of the order of seconds to minutes, indicating the rapid surface rearrangement of carbonates in the presence of aqueous fluids. As a consequence, many carbonate-fluid reactions in low temperature environments are controlled by local thermodynamic equilibria rather than by the global equilibrium in the whole system.

木材贸易与全球森林消失

世界野生自然基金会(WWF)进行的一项研究指出,国际木材贸易是具有高水平生物多样性的森林退化和消失的主要原因。这个论点驳斥了过去关于森林消失与退化的流行的一种说法,即森林的退化与消失主要是由于农业的移耕和木材作为燃料的消耗而造成的。

Intrusive Thoughts and Executive Functions in Obsessive Compulsive Disorder

Objectives: Our aim was to compare the effects of an unwanted intrusive thought on executive function in a group of people with Obsessive Compulsive Disorder (OCD) and in a healthy group. Method: The Behavior Rating Inventory of Executive Function Adult (BRIEF-A) was used to measure executive dysfunction in everyday life in people with OCD. The study participants underwent either an intrusive thought induction or neutral thought induction prior to the administration of three computer-based tests of executive function. Results: The BRIEF-A results confirmed the impairment of executive function in everyday life for patients with OCD. In the number-letter task, patients with OCD displayed a longer reaction time (relative to the controls). There were no intergroup differences in the local-global task. In the go/no-go task, there was a significant impairment (p = 0.03) in the OCD group (with more commission errors than controls). There was a non-significant trend towards an effect of thought induction in both groups in the number-letter task. However, intrusive thought induction did not have a greater effect than neutral thought induction on the OCD group in any of the tasks. Conclusions: Intrusive thought induction has no effect on executive function in the two groups. The two groups differed with regard to two executive tasks.

Impaired Executive Function in Everyday Life: A Predictor of OCD Relapse?

Objectives: In the present study, we set out to establish whether executive function in everyday life is impaired in obsessive-compulsive disorder patients, and if it is more impaired (or not) in patients who relapsed after cognitive behavioural therapy than in treatment-na?ve obsessive-compulsive disorder patients. Method: The Behavior Rating Inventory of Executive Function— Adult Version (BRIEF-A) was used to measure executive function in everyday life in three groups of 19 participants: treatment-na?ve obsessive-compulsive disorderpatients, obsessive-compulsive disorder patients having relapsed after CBT, and healthy controls. Results: The BRIEF-A results revealed an impairment in executive function in the treatment-na?ve and relapsed obsessive-compulsive disorder groups, relative to the healthy control group. There was no significant difference in executive function between the two groups of patients. Conclusions: These results show that impaired executive function is not associated with relapse in patients with obsessive-compulsive disorder having undergone cognitive behavioural therapy.

Pore pressure prediction in offshore Niger delta using data-driven approach: Implications on drilling and reservoir quality

Despite exploration and production success in Niger Delta,several failed wells have been encountered due to overpressures.Hence,it is very essential to understand the spatial distribution of pore pressure and the generating mechanisms in order to mitigate the pitfalls that might arise during drilling.This research provides estimates of pore pressure along three offshore wells using the Eaton's transit time method,multi-layer perceptron artificial neural network(MLP-ANN)and random forest regression(RFR)algorithms.Our results show that there are three pressure magnitude regimes:normal pressure zone(hydrostatic pressure),transition pressure zone(slightly above hydrostatic pressure),and over pressured zone(significantly above hydrostatic pressure).The top of the geopressured zone(2873 mbRT or 9425.853 ft)averagely marks the onset of overpressurization with the excess pore pressure above hydrostatic pressure(P∗)varying averagely along the three wells between 1.06−24.75 MPa.The results from the three methods are self-consistent with strong correlation between the Eaton's method and the two machine learning models.The models have high accuracy of about>97%,low mean absolute percentage error(MAPE<3%)and coefficient of determination(R2>0.98).Our results have also shown that the principal generating mechanisms responsible for high pore pressure in the offshore Niger Delta are disequilibrium compaction,unloading(fluid expansion)and shale diagenesis.

纯银璀璨 星光闪耀

Season’S Holiday,到处都是星光熠熠,而在圣诞树闪烁的光芒下,最璀璨的却是925纯银的光辉,亮丽却不失优雅。这是高雅恒久的生活精品,反映今天的社会对文化、设计、传统和优秀工艺的追求与礼赞,绽放具有时尚格调及跨越时代的美感。925纯银精制,代表了不经意间流露的独特个性。

Relocation of hypocenters from DOMERAPI and BMKG networks： a preliminary result from DOMERAPI project

Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification,arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger＇s method（Geiger 1912） for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics（BMKG） seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip.

Preface

This focused issue of the Communications on Applied Mathematics and Computation is in Honour of Prof.Rémi Abgrall on the Occasion of His 61th Birthday.Rémi Abgrall has been a student in mathematics(1981–1985)of Ecole Normale Supérieure de Saint Cloud(now part of ENS Lyon).After his studies in pure mathematics,he changed orientation tofluid mechanics.He did his PhD at the Laboratoire de Météorologie Dynamique(LMD)at Ecole Normale Supérieure under the supervision of Claude Basdevant.He graduated in December 1987 with a thesis on a semi-Lagrangian model of 2D turbulence,refereed by Olivier Pironneau and Marcel Lesieur.

大陆俯冲界面之上大规模硅富集流体的地球物理学证据

俯冲带中的流体可能对俯冲过程产生重要影响.然而,关于大陆俯冲期间流体规模及其作用的地球物理约束仍然有限.西阿尔卑斯造山带是全球保存最完好的大陆俯冲带之一,为认识大陆俯冲过程中流体作用的影响提供了重要的参考.本文综合多种地球物理方法分析了西阿尔卑斯造山带地区的V_(P)/V_(S)比值,发现在俯冲区的上盘侧存在高V_(P)/V_(S)(>1.9)带,与部分蛇纹岩化的上覆地幔楔位置一致;而在下盘侧存在异常低的V_(P)/V_(S)(<1.7)带,异常深度浅于30km.本文认为,观测到的低V_(P)/V_(S)比值异常是由地壳内广泛分布的富硅岩脉导致,指示了在俯冲时期大陆俯冲界面之上可能存在的富硅流体流动.本文的结果暗示俯冲时期的流体流动可能降低了俯冲界面的有效应力,从而促进了大陆俯冲.

Bidirectional energy-controlled piezoelectric shunt damping technology and its vibration attenuation performance

Piezoelectric material-based semi-active vibration control systems may effectively suppress vibration amplitude without any external power supply,or even harvest electrical energy.This bidirectional electrical energy control phenomenon is theoretically introduced and validated in this paper.A flyback transformer-based switching piezoelectric shunt circuit that can extract energy from or inject energy into piezoelectric elements is proposed.The analytical expressions of the controlled energy and the corresponding vibration attenuation are therefore derived for a classical electromechanical cantilever beam.Theoretical predictions validated by the experimental results show that the structure vibration attenuation can be tuned from−5 to−25 dB under the given electrical quality factor of the circuit and figure of merit of the electromechanical structure,and the consumed power is in the range of−13 to 25 mW,which is a good theoretical basis for the development of self-sensing,self-adapting,and self-powered piezoelectric vibration control systems.

Geophysical evidence of large-scale silica-rich fluid flow above the continental subduction interface

Fluids in subduction zones can have major effects on subduction dynamics.However,geophysical constraints on the scale and impact of fluid flow during continental subduction are still limited.Here we analyze the VP/VS ratios in the Western Alpine region,hosting one of the best-preserved fossil continental subduction zones worldwide,to investigate the impact of fluid flow during continental subduction.We found a belt of high VP/VS ratios>1.9 on the upper-plate side of the subduction zone,consistent with a partially serpentinized upper-plate mantle,and a belt of unusually low VP/VS ratios<1.7 on the lower-plate side,at depths shallower than 30 km.We propose that these low VP/VS ratios result from a widespread network of silica-rich veins,indicating past fluid flow along the continental subduction interface.Our results suggest that past fluid flow may have reduced the effective stress along the subduction interface thus favoring continental subduction.

Catalytic decomposition performance for O_3 and NO_2 in humid indoor air on a MnO_x/Al_2O_3 catalyst modified by a cost-effective chemical grafting method

Processes based on non-thermal plasma（NTP） for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone（O3） and nitrogen oxides（NOx）. Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiOx, CoOxand MnOxwith different weight percentage 1, 5 and 10 wt.%,deposited on a γ-Al2O3 support. The O3 removal efficiency（ORE） and the NOxremoval efficiency（NRE） were very encouraging in dry air： about 65% and 80%, respectively, by using2 g 5 wt.% MnOx/Al2O3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity（RH） on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnOx/Al2O3 catalyst with different trichloro（alkyl）silanes（TCAS）.The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/gcatof modifying agent represents the best catalytic decomposition performance for O3. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst.

Study of the CKM angleγsensitivity using flavor untagged B_(s)^(0)→D^(+)^(0)Ф decays

A sensitivity study on the measurement of the CKM angle γ from B_(s)^(0)→D^(+)^(0)Ф decays is conducted us-ing the D-meson reconstructed in the quasi flavour-specific modes Kπ,K3π,and Kππ^(0),as well as CP-eigenstate modes KK and m,where the notation DO corresponds toa D0 or D0 meson.The LHCb experiment is presented as a use case.A statistical uncertainty of approximately 8°-19°can be achieved with the pp collision data collcted in the LHCb experiment from 2011 to 2018.The sensitivity to r should be of the order 3°-8°after accumulating 23 fb^(-1) of pp collision data by 2025,whereas it is expected to improve further by 300 fb^(-1) by the second half of the 2030 decade.The accuracy is dependent on the strong parameters r and og,which together with ydescribe the interfer-ence between the leading ampliudes of the B_(s)^(0)→D^(+)^(0)Ф decays.

Study of the Mechanical Properties of 3D-printed Onyx Parts: Investigation on Printing Parameters and Effect of Humidity

Recently,an increasing number of parts have been produced using additive manufacturing technology.They are no longer simply prototypes but structural parts whose mechanical characteristics must be known before printing.One of the weaknesses of 3D printing is the significant variability in the dimensions and geometrical and mechanical properties of the printed parts.These properties depend on specific printing parameters and environmental conditions.This study aims to determine the influence of two printing parameters,namely,the orientation and positioning of the parts on the printing platform and the influence of humidity on the mechanical properties of the parts.The studied samples were fabricated with onyx using a Markforged X7 printer.The results showed that onyx could be considered an isotropic material to a certain extent because its mechanical properties do not vary sufficiently according to the orientation angle on the printing platform;a maximum deviation of 10%was observed between the different orientations.In contrast to the orientation,the positioning(flat or XY,on-edge or XZ,and upright or ZX)of the workpieces significantly influenced the mechanical properties.Positioning on the edge allowed the Young’s modulus to be up to 50% greater than that of flat and upright positioning.The study of the sensitivity to humidity revealed that a specimen absorbs approximately 2%of the humidity and loses up to 65%of its Young’s modulus after 165 days of exposure,significantly influencing the mechanical properties of the parts.Consideration should be given to this aging of onyx when using printed parts as structural parts.

Impedancemetry of multiplexed quantum devices using an on-chip cryogenic complementary metal-oxide-semiconductor active inductor

In the pursuit for scalable quantum processors,significanteffort has been devoted to the development of cryogenic classical hardware for the control and readout of a growingnumber of qubits.The current work presented a novelapproach called impedancemetry that is suitable for measuringthe quantum capacitance of semiconductor qubits connected toa resonant LC-circuit.The impedancemetry circuit exploits theintegration of a complementary metal-oxide-semiconductor(CMOS)active inductor in the resonator with tunable resonance frequency and quality factor,enabling the optimizationof readout sensitivity for quantum devices.The realized cryogenic circuit allows fast impedance detection with a measuredcapacitance resolution down to 10 aF and an input-referrednoise of 3.7 aF/Hz p.At 4.2 K,the power consumption of theactive inductor amounts to 120μW,with an additional dissipation for on-chip current excitation(0.15μW)and voltageamplification(2.9 mW)of the impedance measurement.Compared to the commonly used schemes based on dispersiveRF reflectometry which require millimeter-scale passive inductors,the circuit exhibits a notably reduced footprint(50μm360μm),facilitating its integration in a scalable quantumclassical architecture.The impedancemetry method has been applied at 4.2 K to the detection of quantum effects in the gatecapacitance of on-chip nanometric CMOS transistors that areindividually addressed via multiplexing.

An efficient sensitivity analysis for energy performance of building envelope: A continuous derivative based approach

Within the framework of building energy assessment,this article proposes to use a derivative based sensitivity analysis of heat transfer models in a building envelope.Two,global and local,estimators are obtained at low computational cost,to evaluate the influence of the parameters on the model outputs.Ranking of these estimators values allows to reduce the number of model unknown parameters by excluding non-significant parameters.A comparison with variance and regression-based methods is carried out and the results highlight the satisfactory accuracy of the continuous-based approach.Moreover,for the carried investigations the approach is 100 times faster compared to the variance-based methods.A case study applies the method to a real-world building wall.The sensitivity of the thermal loads to local or global variations of the wall thermal properties is investigated.Additionally,a case study of wall with window is analyzed.

Dispersive Shallow Water Wave Modelling.Part II:Numerical Simulation on a Globally Flat Space

In this paper we describe a numerical method to solve numerically the weakly dispersive fully nonlinear SERRE-GREEN-NAGHDI(SGN)celebrated model.Namely,our scheme is based on reliable finite volume methods,proven to be very efficient for the hyperbolic part of equations.The particularity of our study is that we develop an adaptive numerical model using moving grids.Moreover,we use a special form of the SGN equations where non-hydrostatic part of pressure is found by solving a linear elliptic equation.Moreover,this form of governing equations allows to determine the natural form of boundary conditions to obtain a well-posed(numerical)problem.

Exploiting the Community Structure of Fraudulent Keywords for Fraud Detection in Web Search

Internet users heavily rely on web search engines for their intended information.The major revenue of search engines is advertisements(or ads).However,the search advertising suffers from fraud.Fraudsters generate fake traffic which does not reach the intended audience,and increases the cost of the advertisers.Therefore,it is critical to detect fraud in web search.Previous studies solve this problem through fraudster detection(especially bots)by leveraging fraudsters'unique behaviors.However,they may fail to detect new means of fraud,such as crowdsourcing fraud,since crowd workers behave in part like normal users.To this end,this paper proposes an approach to detecting fraud in web search from the perspective of fraudulent keywords.We begin by using a unique dataset of 150 million web search logs to examine the discriminating features of fraudulent keywords.Specifically,we model the temporal correlation of fraudulent keywords as a graph,which reveals a very well-connected community structure.Next,we design DFW(detection of fraudulent keywords)that mines the temporal correlations between candidate fraudulent keywords and a given list of seeds.In particular,DFW leverages several refinements to filter out non-fraudulent keywords that co-occur with seeds occasionally.The evaluation using the search logs shows that DFW achieves high fraud detection precision(99%)and accuracy(93%).A further analysis reveals several typical temporal evolution patterns of fraudulent keywords and the co-existence of both bots and crowd workers as fraudsters for web search fraud.