Effect of diagenetic variation on the static and dynamic mechanical behavior of coral reef limestone

Coral reef limestone at different depositional depths and facies differ remarkably on the textural and mineralogical characteristics,owing to the complex sedimentary diagenesis.To explore the effects of pore structure and mineral composition associated with diagenetic variation on the mechanical behavior of reef limestone,a series of quasi-static and dynamic compression tests along with microscopic examinations were performed on the reef limestone at shallow and deep burial depths.It is revealed that the shallow reef limestone(SRL)is classified as a porous aragonite-type carbonate rock with high porosity(55.3±3.2)%and pore connectivity.In comparison,the deep reef limestone(DRL)is mainly composed of dense calcite-type calcium carbonate with low porosity(4.9±1.6)%and pore connectivity.The DRL strengthened and stiffened by the tight grain framework consistently displays much higher values of the dynamic compressive strength,elastic modulus,brittleness index,and specific energy absorption than those of the SRL.The gap between two types of limestone further increases with an increase in strain rate.It appears that the failure pattern of SRL is dominated by the inherent defects like weak bonding interfaces and growth lines,revealed by the intricate fracturing network and mixed failure.Likewise,although the preexisting megapores in DRL may affect the crack propagation on pore tips to a certain distance,it hardly alters the axial splitting failure of DRL under impacts.The stress wave propagation and attenuation in SRL is primarily controlled by the reflection and diffusion caused by plenty mesopores,as well as an energy dissipation in layer-wise pore collapse and adjacent grain crushing,while the stress wave in DRL is highly hinged on the insulation and diffraction induced by the isolated megapores.This process is accompanied by the energy dissipation behavior of inelastic deformation resulted from the pore-emanated microcracking.

Impact of air pollution on urbanization:evidence at China’s city level

This paper investigates the effect and transmission mechanism of air pollution on urbanization based on data from China’s 107 cities during 2005–2018.In order to identify the impact of air pollution on China’s urbanization,we utilized night light data to represent the level of urbanization and used temperature inversion as an instrumental variable to mitigate endogeneity within the two-stage least squares framework.The results suggest that air pollution significantly slowed China’s urbanization process with economic growth acting as the transmission mechanism.The heterogeneity analyses revealed that air pollution had a greater negative impact on urbanization in northern regions than that in southern regions,and a greater negative impact in resource-oriented cities than that in non-resource-based cities.We also find that air pollution was to the detriment of urbanization in larger cities,which have more than 3 million residents,while it did not have a significant impact on Type II large cities,which have fewer than 3 million residents.

Evaluation of the performance of alternative assessment configurations to account for the spatial heterogeneity in age-structure: a simulation study based on Indian Ocean albacore tuna

Various population structures or spatial heterogeneities in population distribution have been an important source of model misspecification and have had an impact on estimation performance in fisheries stock assessment.In this study,we simulated the Indian Ocean albacore spatial heterogeneity in age-structure using Stock Synthesis according to the stage-dependent migration rate and region-dependent fishing mortality rate and generated the stock assessment data.Based on these data,we investigated the performances of different spatial configurations,selectivity curves and selections of CPUE(catch per unit effort)indices of the assessment models which were used to account for spatial heterogeneity.The results showed:(1)although the spatially explicit configurations,which exactly matched the operating model,provided unbiased and accurate estimates of relative spawning biomass,relative fishing mortality rate and maximum sustainable yield in all simulation scenarios,their performance may be very poor if there were mismatches between them and the operating model due to gaps in knowledge and data;(2)for spatially explicit assessment configuration,the correct boundary was required,but for non-spatially explicit assessment configuration,it seemed more important for analysts to partition the area to properly reflect the transition in field data and to effectively account for the impacts of ignoring the spatial structure by using the additional spatially referenced parameters;(3)although the areas-as-fleets methods and flexible time-varying selectivity curves could be used as better alternative approaches to account for spatial structure,these configurations could not completely eliminate the impacts of model misspecification and the quality of estimates of different quantities from the same assessment model may be inconsistent or the performance of the same assessment configuration may fluctuate significantly between simulation scenarios;(4)although the worst estimates could generally be avoided by using multiple CPUE indices,there were no best solutions to select or regenerate the CPUE indices to account for the impacts of the ignored spatial structure to obviously improve the quality of stock assessment.Compared with the results of assessment model configurations which are used to account for the spatial structure by different modelers,the performances of the configurations are always casespecific except for spatially explicit configurations which exactly match the operating model.In this sense,our study will not only provide some insights into the current Indian Ocean albacore stock assessment but also enrich existing knowledge regarding the performance of assessment configurations to account for spatial structure.

Active plane modulation of Bi_(2)O_(3)nanosheets via Zn substitution for efficient electrocatalytic CO_(2)reduction to formic acid

Formic acid is considered one of the most economically viable products for electrocatalytic CO_(2)reduction reaction(CO_(2)RR).However,developing highly active and selective electrocatalysts for effective CO_(2)conversion remains a grand challenge.Herein,we report that structural modulation of the bismuth oxide nanosheet via Zn^(2+)cooperation has a profound positive effect on exposure of the active plane,thereby contributing to high electrocatalytic CO_(2)RR performance.The obtained Zn-Bi_(2)O_(3)catalyst demonstrates superior selectivity towards formate generation in a wide potential range;a high Faradaic efficiency of 95%and a desirable partial current density of around 20 mA·cm^(-2)are obtained at−0.9 V(vs.reversible hydrogen electrode(RHE)).As proposed by density functional theory calculations,Zn substitution is the most energetically feasible for forming and stabilizing the key OCHO*intermediate among the used metal ions.Moreover,the more negative adsorption energy of OCHO*and the relatively low energy barrier for the desorption of HCOOH*are responsible for the enhanced activity and selectivity.

Bilirubin inhibits lung carcinogenesis by up-regulating cystatin A expression in tumor-infiltrating macrophages

As one of the leading causes of cancer deaths worldwide,the pathogenesis of lung cancer is still not completely understood.Bilirubin,a product of heme metabolism,has long been considered a waste product of the body.Increasing evidence suggests that bilirubin has additional antioxidant,anti-inflammatory,and proteasome inhibitory activities.However,the specific role of bilirubin in the formation and development of lung cancer has not been elucidated.

Structural engineering of Fe single-atom oxygen reduction catalyst with high site density and improved mass transfer

Fe-N-C catalysts are widely considered as promising non-precious-metal candidates for electrocatalytic oxygen reduction reaction(ORR),Yet despite their high catalytic activity through rational modulation,challenges remain in their low site density and unsatisfactory mass transfer structure.Herein,we present a structural engineering approach employing a soft-template coating strategy to fabricate a hollow and hierarchically porous N-doped carbon framework anchored with atomically dispersed Fe sites(FeNCh) as an efficient ORR catalyst.The combination of hierarchical porosity and high exterior surface area is proven crucial for exposing more active sites,which gives rise to a remarkable ORR performance with a half-wave potential of 0.902 V in 0.1 m KOH and 0.814 V in 0.1 m HClO_(4),significantly outperforming its counterpart with solid structure and dominance of micropores(FeNC-s).The mass transfer property is revealed by in-situ electrochemical impedance spectroscopy(EIS) measurement.The distribution of relaxation time(DRT) analysis is further introduced to deconvolve the kinetic and mass transport processes,which demonstrates an alleviated mass transport resistance for FeNC-h,validating the effectiveness of structural engineering.This work not only provides an effective structural engineering approach but also contributes to the comprehensive mass transfer evaluation on advanced electrocatalyst for energy conversion applications.

Analysis of traffic safety in airport aircraft activity areas based on bayesian networks and fault trees

To assess road traffic safety risk in civil aviation airports and develop effective accident prevention measures,this study proposed a risk assessment method based on accident tree and Bayesian network for airport aircraft activity areas.It identified influencing factors in the aircraft activity area from the perspectives of person-vehicle-road-environment-management and analyzed their relationships.The Bayesian network was utilized to determine initial probabilities for each influencing factor.Findings indicated a relatively high overall safety level in the airport's road traffic system.Accident trees were employed to qualitatively and quantitatively analyze common human-vehicle accident patterns.The initial probabilities obtained from the Bayesian network served as basic event probabilities in the accident tree to determine the occurrence probability of the top event.Taking a 4F airport in China as an example,accident cause analysis identified five important risk sources in human-vehicle accidents,including blind spots for special vehicles,illegal driving by drivers,pedestrians violating regulations,passengers entering restricted areas,and blind spots at intersections.Corresponding safety management measures were formulated.The study concluded that the integration of Bayesian networks and accident trees effectively determines accident probabilities and offers specific solutions,thus playing a crucial role in enhancing road traffic safety management within aviation airports.

二维纳米材料g-C_(3)N_(4)在电化学发光中的应用研究

电化学发光(ECL)兼备电化学和化学发光的特点,灵敏度高、线性范围宽、背景干扰小,得到了广大分析科学研究者的关注;传统的ECL材料虽然发光效率高,但仍存在价格昂贵、负载量低等缺点。g-C_(3)N_(4)是一种不含金属的半导体纳米材料,主要以三嗪环或七嗪环为基本结构单元,通过层间的范德华力以及层内的C—N共价键结合,构成类石墨的二维层状结构,具有性质稳定、能带结构独特、生物兼容性好、环保无毒、易于功能化、原料价廉、制备过程简单等优点。自2012年g-C_(3)N_(4)首次被发现具备ECL的性能,至今已被广泛应用到ECL中。本文根据ECL的发光机理、传感器的作用效果、传感的信号类型以及不同的检测对象进行了分类,综述了近年来g-C_(3)N_(4)在ECL传感器构建中的研究进展,并阐述了g-C_(3)N_(4)在ECL发展中存在的挑战和前景。

GPU-BASED FLUID SIMULATION WITH FAST COLLISION DETECTION ON BOUNDARIES

In this paper,we present a method for fluid simulation based on smoothed particle hydrodynamic(SPH)with fast collision detection on boundaries on GPU.The major goal of our algorithm is to get a fast SPH simulation and rendering on GPU.Additionally,our algorithm has the following three features:At first,to make the SPH method GPU-friendly,we introduce a spatial hash method for neighbor search.After sorting the particles based on their grid index,neighbor search can be done quickly on GPU.Second,we propose a fast particle-boundary collision detection method.By precomputing the distance field of scene boundaries,collision detection’s computing cost arrived as O(n),which is much faster than the traditional way.Third,we propose a pipeline with fine-detail surface reconstruction,and progressive photon mapping working on GPU.We experiment our algorithm on different situations and particle numbers of scenes,and find out that our method gets good results.Our experimental data shows that we can simulate 100K particles,and up to 1000K particles scene at a rate of approximately 2 times per second.