This paper introduces the Integrated Security Embedded Resilience Architecture (ISERA) as an advanced resilience mechanism for Industrial Control Systems (ICS) and Operational Technology (OT) environments. The ISERA f...This paper introduces the Integrated Security Embedded Resilience Architecture (ISERA) as an advanced resilience mechanism for Industrial Control Systems (ICS) and Operational Technology (OT) environments. The ISERA framework integrates security by design principles, micro-segmentation, and Island Mode Operation (IMO) to enhance cyber resilience and ensure continuous, secure operations. The methodology deploys a Forward-Thinking Architecture Strategy (FTAS) algorithm, which utilises an industrial Intrusion Detection System (IDS) implemented with Python’s Network Intrusion Detection System (NIDS) library. The FTAS algorithm successfully identified and responded to cyber-attacks, ensuring minimal system disruption. ISERA has been validated through comprehensive testing scenarios simulating Denial of Service (DoS) attacks and malware intrusions, at both the IT and OT layers where it successfully mitigates the impact of malicious activity. Results demonstrate ISERA’s efficacy in real-time threat detection, containment, and incident response, thus ensuring the integrity and reliability of critical infrastructure systems. ISERA’s decentralised approach contributes to global net zero goals by optimising resource use and minimising environmental impact. By adopting a decentralised control architecture and leveraging virtualisation, ISERA significantly enhances the cyber resilience and sustainability of critical infrastructure systems. This approach not only strengthens defences against evolving cyber threats but also optimises resource allocation, reducing the system’s carbon footprint. As a result, ISERA ensures the uninterrupted operation of essential services while contributing to broader net zero goals.展开更多
Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerica...Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerical simulations of ice formation on thin flat plates using CFD and FENSAP-ICE,exploring how air temperature,wind velocity,and angle of attack(AOA)affect icing behavior and aerodynamic characteristics.Results indicate that ice thickness increases linearly over time.Rime ice forms at low temperatures due to immediate droplet freezing,whereas glaze ice develops at higher temperatures when a water film forms and subsequently refreezes into protruding ice horns;under identical conditions,rime ice consistently produces thicker ice layers than glaze ice.Increasing wind speed substantially enhances ice growth and coverage,while speeds as low as 1 m/s result in minimal accretion.Changes in AOA shift the icing region toward the pressure side,and AOAs of equal magnitude but opposite sign yield symmetrical ice accretion patterns and identical maximum thickness values.After icing,the plate’s leading edge becomes smoother,slightly reducing drag while increasing lift and moment coefficients.These findings highlight the dominant roles of temperature,wind speed,and AOA in determining ice morphology,extent,and aerodynamic impact,providing valuable insights for predicting icing effects and developing mitigation strategies for structures operating in icing-prone regions.展开更多
Based on comprehensive observations of 20 wire icing events during winter from 2019 to 2021,we investigated the characteristics of the icing properties,the atmospheric boundary layer structure,the raindrop size distri...Based on comprehensive observations of 20 wire icing events during winter from 2019 to 2021,we investigated the characteristics of the icing properties,the atmospheric boundary layer structure,the raindrop size distribution,and their associated effects on the ice accretion mechanism in the mountainous region of Southwest China.The maximum ice weight was positively correlated with the duration of ice accretion in the mountainous area.The duration of precipitation accounted for less than 20%of the icing period in the mountainous area,with solid-phase hydrometeors being predominant.Icing events,dominated by freezing rain(FR)and mixed rain–graupel(more than 70%),were characterized by glaze or highdensity mixed icing.The relationship between the melting energy and refreezing energy reflected the distribution characteristics of the proportion of FR under mixed-phase precipitation.The intensity of the warm layer and the dominant precipitation phase significantly affected the variations in the microphysical properties of FR.The melting of large dry snowflakes significantly contributed to FR in the mountainous areas,resulting in smaller generalized intercepts and larger mass-weighted mean diameters in the presence of a stronger warm layer.Under a weaker warm layer,the value of the massweighted mean diameter was significantly smaller because of the inability of large solid particles to melt.Finally,FR in the mountainous area dominated the ice weight during the rapid ice accumulation period.A numerical simulation of FR icing on wires effectively revealed the evolution of disaster-causing icing in mountainous areas.展开更多
The International Commission on Stratigraphy(ICS)has been producing and updating its International Chro-nostratigraphic Chart for several decades.The chart communicates higher-order divisions of geological time and ac...The International Commission on Stratigraphy(ICS)has been producing and updating its International Chro-nostratigraphic Chart for several decades.The chart communicates higher-order divisions of geological time and actual knowledge on the numerical ages of their bound-aries.Distributed via the ICS website www.stratigraphy.org the chart promotes use in graphic,tabulated and further digital forms in multiple languages.This paper is a status update,eleven years since the last such publication,cov-ering activities between 2012 and 2024.Chart updates during the past decade have echoed the ICS’s primary objective of precisely defining a global standard set of time-correlative units(Systems,Series,Stages)for stratigraphic successions worldwide.These units are,in turn,the basis for the Periods,Epochs,and Ages of the Geological Time Scale.Their standardization is fundamental for expressing geological knowledge,in application and education,out-reach and continuing research.The chart offers a frame-work through which regional-scale higher-resolution divisions can be linked,equated and collated.Likewise it offers a framework for digital representation of the Geological Time Scale.Maintenance and distribution of chart versions on the web has been a manual endeavour,a process that ICS is upgrading to serve an increasingly digital world.展开更多
This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water drop...This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water droplet impingement characteristics is established.Then,considering the deformation and breaking effects during the movement,this method is extended to calculate the impingement characteristics of supercooled large droplets,as well as the bouncing and splashing effects during impingement.The impingement characteristics of supercooled large droplets is then investigated by this method.The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper.In addition,the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects.The bouncing effect mainly affects the mass loss near the impingement limits,while the splashing effect influences the result around the stagnation point.This investigation is beneficial for the analysis of aircraft icing and the design of anti⁃icing system with supercooled large droplet conditions.展开更多
The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ...The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft.The paper systematically investigates the effects of the supercooling degree,the surface temperature,and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces.To address the ice-prone nature of CFRCs,nanoparticle-modified anti-icing coatings are developed,and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed.Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation.Under conditions of droplet temperature(−15℃)and surface temperature(−18℃),the icing time of hydrophobic-modified CFRCs was delayed by over 1100 ms,representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.展开更多
Icing of water droplets is a ubiquitous phenomenon with significant implications across natural systems and industrial applications.Despite extensive research,the intricate interplay among heat transfer,mass transport...Icing of water droplets is a ubiquitous phenomenon with significant implications across natural systems and industrial applications.Despite extensive research,the intricate interplay among heat transfer,mass transport,and phase change during droplet freezing remains incompletely understood,particularly in the context of multiscale dynamics and environmental dependencies.This review critically examines recent advances in uncovering the fundamental mechanisms of droplet icing through experimental,theoretical,and computational approaches.We begin by revisiting the classical tip singularity problem in the freezing of pure water droplets,analyzing its mathematical formulation and physical significance.Subsequent sections explore how environmental boundary conditions and multicomponent effects influence freezing kinetics,solute redistribution,and ice morphology.Furthermore,we evaluate emerging hybrid numerical frameworks that resolve coupled multiphase physics during solidification processes.Finally,we identify key challenges and open questions that require further investigation in this field.展开更多
Polar ships face significant risks from ice accretion on decks,superstructures,and power systems.Ice formation on the power intake system particularly affects vessel stability and safety.While freshwater icing has bee...Polar ships face significant risks from ice accretion on decks,superstructures,and power systems.Ice formation on the power intake system particularly affects vessel stability and safety.While freshwater icing has been extensively researched,comprehensive multi-parameter studies on ice accretion for intake structures remain insufficient.This investigation examines the icing characteristics of the air shroud,a critical component of marine gas turbines,resulting from saltwater droplet freezing.The study utilized a custom-built cyclic ice wind tunnel,with flow field quality verified through Five-hole probe and Hot wire anemometer methods,and droplet field quality validated using Laser,Flowmeter,Ice blade,and Icing calibration grid techniques.The research analyzes ice distribution and thickness on the shroud under varying NaCl concentrations,considering temperature,liquid water content(LWC),and median volume diameter(MVD).The findings reveal that decreased salinity facilitates rime ice formation,resulting in rough ice texture.Temperature reduction,increased LWC,and larger MVD enhanced salinity's influence on ice thickness.The shroud exhibits substantial radial ice accretion,with coverage extending to approximately 90%.These results establish a foundation for further investigation of saltwater icing mechanisms and pioneer icing research in marine gas turbine intake systems.展开更多
The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–...The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.展开更多
The utility of ICS International Chronostratigraphic Charts(ICS Charts)relies on the accuracy and precision of reported geochronologic dates and their relationship to the bases of global chronostratigraphic units.Howe...The utility of ICS International Chronostratigraphic Charts(ICS Charts)relies on the accuracy and precision of reported geochronologic dates and their relationship to the bases of global chronostratigraphic units.However,an examination of some early Paleozoic dates(i.e.,Cambrian-Ordovician boundary and lowest Ordovician)on the ICS Charts shows that they differ from originally reported and late recalculated dates.Thus,they record a numerical precision that differs from these revised dates.The dates assigned to the bases of formal early Paleozoic chronostratigraphic units may be interpreted by the lay reader as precise determinations.展开更多
基金funded by the Office of Gas and Electricity Markets(Ofgem)and supported by De Montfort University(DMU)and Nottingham Trent University(NTU),UK.
文摘This paper introduces the Integrated Security Embedded Resilience Architecture (ISERA) as an advanced resilience mechanism for Industrial Control Systems (ICS) and Operational Technology (OT) environments. The ISERA framework integrates security by design principles, micro-segmentation, and Island Mode Operation (IMO) to enhance cyber resilience and ensure continuous, secure operations. The methodology deploys a Forward-Thinking Architecture Strategy (FTAS) algorithm, which utilises an industrial Intrusion Detection System (IDS) implemented with Python’s Network Intrusion Detection System (NIDS) library. The FTAS algorithm successfully identified and responded to cyber-attacks, ensuring minimal system disruption. ISERA has been validated through comprehensive testing scenarios simulating Denial of Service (DoS) attacks and malware intrusions, at both the IT and OT layers where it successfully mitigates the impact of malicious activity. Results demonstrate ISERA’s efficacy in real-time threat detection, containment, and incident response, thus ensuring the integrity and reliability of critical infrastructure systems. ISERA’s decentralised approach contributes to global net zero goals by optimising resource use and minimising environmental impact. By adopting a decentralised control architecture and leveraging virtualisation, ISERA significantly enhances the cyber resilience and sustainability of critical infrastructure systems. This approach not only strengthens defences against evolving cyber threats but also optimises resource allocation, reducing the system’s carbon footprint. As a result, ISERA ensures the uninterrupted operation of essential services while contributing to broader net zero goals.
基金supported by the National Natural Science Foundation of China(52278532)Sichuan Science and Technology Program(2024NSFSC0153)。
文摘Ice accretion on structures such as aircraft wings and wind turbine blades poses serious risks to aerodynamic performance and operational safety,particularly in cold and humid environments.This study conducts numerical simulations of ice formation on thin flat plates using CFD and FENSAP-ICE,exploring how air temperature,wind velocity,and angle of attack(AOA)affect icing behavior and aerodynamic characteristics.Results indicate that ice thickness increases linearly over time.Rime ice forms at low temperatures due to immediate droplet freezing,whereas glaze ice develops at higher temperatures when a water film forms and subsequently refreezes into protruding ice horns;under identical conditions,rime ice consistently produces thicker ice layers than glaze ice.Increasing wind speed substantially enhances ice growth and coverage,while speeds as low as 1 m/s result in minimal accretion.Changes in AOA shift the icing region toward the pressure side,and AOAs of equal magnitude but opposite sign yield symmetrical ice accretion patterns and identical maximum thickness values.After icing,the plate’s leading edge becomes smoother,slightly reducing drag while increasing lift and moment coefficients.These findings highlight the dominant roles of temperature,wind speed,and AOA in determining ice morphology,extent,and aerodynamic impact,providing valuable insights for predicting icing effects and developing mitigation strategies for structures operating in icing-prone regions.
基金funded by the National Natural Science Foundation of China(Grant No.42325503)the Hubei Provincial Natural Science Foundation and the Meteorological Innovation and Development Project of China(Grant Nos.2023AFD096 and 2022CFD122)+1 种基金the Natural Science Foundation of Wuhan(Grant No.2024020901030454)the Beijige Foundation of NJIAS(Grant No.BJG202304)。
文摘Based on comprehensive observations of 20 wire icing events during winter from 2019 to 2021,we investigated the characteristics of the icing properties,the atmospheric boundary layer structure,the raindrop size distribution,and their associated effects on the ice accretion mechanism in the mountainous region of Southwest China.The maximum ice weight was positively correlated with the duration of ice accretion in the mountainous area.The duration of precipitation accounted for less than 20%of the icing period in the mountainous area,with solid-phase hydrometeors being predominant.Icing events,dominated by freezing rain(FR)and mixed rain–graupel(more than 70%),were characterized by glaze or highdensity mixed icing.The relationship between the melting energy and refreezing energy reflected the distribution characteristics of the proportion of FR under mixed-phase precipitation.The intensity of the warm layer and the dominant precipitation phase significantly affected the variations in the microphysical properties of FR.The melting of large dry snowflakes significantly contributed to FR in the mountainous areas,resulting in smaller generalized intercepts and larger mass-weighted mean diameters in the presence of a stronger warm layer.Under a weaker warm layer,the value of the massweighted mean diameter was significantly smaller because of the inability of large solid particles to melt.Finally,FR in the mountainous area dominated the ice weight during the rapid ice accumulation period.A numerical simulation of FR icing on wires effectively revealed the evolution of disaster-causing icing in mountainous areas.
文摘The International Commission on Stratigraphy(ICS)has been producing and updating its International Chro-nostratigraphic Chart for several decades.The chart communicates higher-order divisions of geological time and actual knowledge on the numerical ages of their bound-aries.Distributed via the ICS website www.stratigraphy.org the chart promotes use in graphic,tabulated and further digital forms in multiple languages.This paper is a status update,eleven years since the last such publication,cov-ering activities between 2012 and 2024.Chart updates during the past decade have echoed the ICS’s primary objective of precisely defining a global standard set of time-correlative units(Systems,Series,Stages)for stratigraphic successions worldwide.These units are,in turn,the basis for the Periods,Epochs,and Ages of the Geological Time Scale.Their standardization is fundamental for expressing geological knowledge,in application and education,out-reach and continuing research.The chart offers a frame-work through which regional-scale higher-resolution divisions can be linked,equated and collated.Likewise it offers a framework for digital representation of the Geological Time Scale.Maintenance and distribution of chart versions on the web has been a manual endeavour,a process that ICS is upgrading to serve an increasingly digital world.
基金supported in part by the National Natural Science Foundation of China(No.51806008)the Open Fund of Key Laboratory of Rotor Aerodynamics Key Laboratory(No.RAL202104-2)。
文摘This numerical simulation investigates the two⁃phase flow under the condition of supercooled large droplets impinging on the aircraft surface.Based on Eulerian framework,a method for calculating supercooled water droplet impingement characteristics is established.Then,considering the deformation and breaking effects during the movement,this method is extended to calculate the impingement characteristics of supercooled large droplets,as well as the bouncing and splashing effects during impingement.The impingement characteristics of supercooled large droplets is then investigated by this method.The results demonstrate that the deformation and breaking effects of supercooled large droplets have negligible influence on the impingement characteristics under the experimental conditions of this paper.In addition,the results of the impingement range and collection efficiency decrease when considering the bouncing and splashing effects.The bouncing effect mainly affects the mass loss near the impingement limits,while the splashing effect influences the result around the stagnation point.This investigation is beneficial for the analysis of aircraft icing and the design of anti⁃icing system with supercooled large droplet conditions.
基金supported by the National Key Laboratory of Advanced Composite Materials(No.KZ42191814)。
文摘The icing characteristics of supercooled large droplet(SLD)impacting carbon fiber-reinforced composites(CFRCs)remain poorly understood,hindering the enhancement of ice protection capabilities and the certification of ice-accreted composite aircraft.The paper systematically investigates the effects of the supercooling degree,the surface temperature,and the impact velocity on the ice accretion behavior of SLDs impacting carbon fiber-reinforced epoxy composite surfaces.To address the ice-prone nature of CFRCs,nanoparticle-modified anti-icing coatings are developed,and the icing characteristics of SLD-impacted modified carbon fiber-reinforced epoxy composite surfaces are analyzed.Results demonstrate that surface-modified carbon fiber-reinforced epoxy composite exhibits significantly delayed ice formation.Under conditions of droplet temperature(−15℃)and surface temperature(−18℃),the icing time of hydrophobic-modified CFRCs was delayed by over 1100 ms,representing a 5.4-fold improvement compared to the unmodified carbon fiber-reinforced epoxy composite.
基金supported by National Natural Science Foundation of China Excellence Research Group Program for“Multiscale Problems in Nonlinear Mechanics”(Grant No.12588201)the National Natural Science Foundation of China(Grant No.12402321)+3 种基金the National Key R&D Program of China(Grant No.2021YFA0716201)the New Cornerstone Science Foundation through the New Cornerstone Investigator Program and the XPLORER PRIZEthe Postdoctoral Fellowship Program of the China Postdoctoral Science Foundation(Grant Nos.GZB20240366 and 2024M751637)Shuimu Tsinghua Scholar Program(Grant No.2023SM038).
文摘Icing of water droplets is a ubiquitous phenomenon with significant implications across natural systems and industrial applications.Despite extensive research,the intricate interplay among heat transfer,mass transport,and phase change during droplet freezing remains incompletely understood,particularly in the context of multiscale dynamics and environmental dependencies.This review critically examines recent advances in uncovering the fundamental mechanisms of droplet icing through experimental,theoretical,and computational approaches.We begin by revisiting the classical tip singularity problem in the freezing of pure water droplets,analyzing its mathematical formulation and physical significance.Subsequent sections explore how environmental boundary conditions and multicomponent effects influence freezing kinetics,solute redistribution,and ice morphology.Furthermore,we evaluate emerging hybrid numerical frameworks that resolve coupled multiphase physics during solidification processes.Finally,we identify key challenges and open questions that require further investigation in this field.
基金supported by the National Natural Science Foundation of China(Grant No.U2241270)China Postdoctoral Science Foundation(Grant No.2025M774341)+1 种基金the Heilongjiang Province Postdoctoral Special Funding Project(Grant No.LBHTZ2408)the Outstanding Doctoral Dissertation Funding Project of Heilongjiang in the New Era(Grant No.LJYXL2024-007)。
文摘Polar ships face significant risks from ice accretion on decks,superstructures,and power systems.Ice formation on the power intake system particularly affects vessel stability and safety.While freshwater icing has been extensively researched,comprehensive multi-parameter studies on ice accretion for intake structures remain insufficient.This investigation examines the icing characteristics of the air shroud,a critical component of marine gas turbines,resulting from saltwater droplet freezing.The study utilized a custom-built cyclic ice wind tunnel,with flow field quality verified through Five-hole probe and Hot wire anemometer methods,and droplet field quality validated using Laser,Flowmeter,Ice blade,and Icing calibration grid techniques.The research analyzes ice distribution and thickness on the shroud under varying NaCl concentrations,considering temperature,liquid water content(LWC),and median volume diameter(MVD).The findings reveal that decreased salinity facilitates rime ice formation,resulting in rough ice texture.Temperature reduction,increased LWC,and larger MVD enhanced salinity's influence on ice thickness.The shroud exhibits substantial radial ice accretion,with coverage extending to approximately 90%.These results establish a foundation for further investigation of saltwater icing mechanisms and pioneer icing research in marine gas turbine intake systems.
文摘目的探究及观察白葡奈氏菌片联合吸入糖皮质激素+长效β2受体激动剂(inhaled corticosteroid+long-acting β_(2)-agonist,ICS+LABA)治疗中重度慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)急性发作的疗效及对生活质量的影响。方法将2020年6月—2021年12月山东第一医科大学附属省立医院的80例中重度COPD急性发作患者根据随机数字表法分为2组。对照组的40例采用ICS+LABA进行治疗,观察组的40例则在对照组的基础上加用白葡奈氏菌片。比较2组的COPD治疗总有效率、不良反应发生率、治疗前后的症状体征积分、疾病状态[慢性阻塞性肺疾病评分(COPD assessment test,CAT评分)]及生活质量[世界卫生组织生存质量测定量表简表(World Health Organization on quality of life brief scale,WHOQOL-BREF评分)]。结果治疗1、2周后观察组的COPD治疗总有效率显著高于对照组,差异有统计学意义(P<0.05),2组的不良反应发生率比较,差异无统计学意义(P>0.05),治疗1、2周后观察组的COPD相关症状体征积分显著低于对照组,CAT评分构成则显著优于对照组,WHOQOL-BREF评分显著高于对照组,差异有统计学意义(P<0.05)。结论白葡奈氏菌片联合ICS+LABA治疗中重度COPD急性发作的疗效较好,且可显著改善患者的生活质量。
文摘The base of the ICS(International Commission on Stratigraphy)Geological Time Scale was ratified in 2022 by defining a new Global Stratigraphic Standard Age(GSSA)for the lower boundary of the Hadean Eon(formerly 4000–3600 Ma);the age of the Solar System based on the oldest solids,calcium-aluminium inclusions(CAIs),generated in the protoplanetary disk.The formal GSSA for the Hadean base is the oldest reliable,weighted mean Ucorrected Pb–Pb age of 4567.30±0.16 Ma obtained for CAIs in primitive meteorites Allende and Efremovka.This age is supported by the 4568–4567 Ma U-corrected Pb–Pb ages of chondrules in Northwest African meteorites.The boundary sets an upper lifetime for the protoplanetary disk and timing of planet formation.
文摘The utility of ICS International Chronostratigraphic Charts(ICS Charts)relies on the accuracy and precision of reported geochronologic dates and their relationship to the bases of global chronostratigraphic units.However,an examination of some early Paleozoic dates(i.e.,Cambrian-Ordovician boundary and lowest Ordovician)on the ICS Charts shows that they differ from originally reported and late recalculated dates.Thus,they record a numerical precision that differs from these revised dates.The dates assigned to the bases of formal early Paleozoic chronostratigraphic units may be interpreted by the lay reader as precise determinations.
