Wild-land fires are a dynamic and destructive force in natural ecosystems. In recent decades, fire disturbances have increased concerns and awareness over significant economic loss and landscape change. The focus of t...Wild-land fires are a dynamic and destructive force in natural ecosystems. In recent decades, fire disturbances have increased concerns and awareness over significant economic loss and landscape change. The focus of this research was to study two northern California wild-land fires: Butte Humboldt Complex and Butte Lightning Complex of 2008 and assessment of vegetation recovery after the fires via ground based measurements and utilization of Landsat 5 imagery and analysis software to assess landscape change. Multi-temporal and burn severity dynamics and assessment through satellite imagery were used to visually ascertain levels of landscape change, under two temporal scales. Visual interpretation indicated noticeable levels of landscape change and relevant insight into the magnitude and impact of both wild-land fires. Normalized Burn Ratio (NBR) and delta NBR (DNBR) data allowed for quantitative analysis of burn severity levels. DNBR results indicate low severity and low re-growth for Butte Humboldt Complex “burned center” subplots. In contrast, DNBR values for Butte Lightning Complex “burned center” subplots indicated low-moderate burn severity levels.展开更多
Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied ...Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied separately from adult trees,and the seedling lifespan,from seed to sapling,is poorly known.In the 50-ha Barro Colorado forest plot,we started intensive censuses of seeds and seedlings in 1994 in order to merge seedling and adult demography and document complete lifespans.Methods In 17 species abundant in seedling censuses,we subdivided populations into six size classes from seed to 1cm dbh,including seeds plus five seedling stages.The smallest seedling class was subdivided by age.Censuses in two consecutive years provided transition matrices describing the probability that a seedling in one stage moved to another one year later.For each species,we averaged the transition matrix across 25 censuses and used it to project the seedling lifespan,from seed until 1cm dbh or death.Results The predicted mean survival rate of seeds to 1cm dbh varied 1000-fold across species,from 2.9×10^(−6)to 4.4×10^(−3);the median was 2.0×10^(−4).The seedling lifespan,or the average time it takes a seed to grow to 1cm dbh,varied across species from 5.1 to 53.1 years,with a median of 20.3 years.In the median species,the 10%fastest-growing seeds would reach 1cm dbh in 9.0 years,and the slowest 10%in 34.6 years.Conclusions Combining seedling results with our previous study of lifespan after 1cm dbh,we estimate that the focal species have full lifespans varying from 41 years in a gap-demanding pioneer to 320 years in one shade-tolerant species.Lifetime demography can contribute precise survival rates and lifespans to forestry models.展开更多
Nanomaterials possess intriguing optical properties that depend sensitively on size, shape, and material content of the structures. Controlling such structural characteristics of the nanostructures allows the tailorin...Nanomaterials possess intriguing optical properties that depend sensitively on size, shape, and material content of the structures. Controlling such structural characteristics of the nanostructures allows the tailoring of their physical and chemical properties, e.g. optical, electronic, and catalytic, to achieve what is desired lot specific applications of interest. This review will cover the development of various shapes for silver and gold nanomaterials with emphasis on their relation to optical properties. Examples of various modern synthetic methods and characterization techniques are highlighted. The influence of the metal nanomaterial＇s shape and optical absorption on surface enhanced Raman scattering （SERS） and a final note on new emerging applications of metal nanostructures are also discussed.展开更多
Hybrid materials of vanadium nitride and porous carbon nanoparticles(VN/PCNPs) were fabricated by a facile pyrolysis process of vanadium pentoxide(V_2O_5) xerogel and melamine at relatively low temperature of 800 ...Hybrid materials of vanadium nitride and porous carbon nanoparticles(VN/PCNPs) were fabricated by a facile pyrolysis process of vanadium pentoxide(V_2O_5) xerogel and melamine at relatively low temperature of 800 °C for supercapacitor application. The effects of the feed ratio of V_2O_5 to melamine(r), and nitrogen flow rate on the microstructure and electrochemical performance were also investigated. It was found that the size of the as-synthesized nanoparticles is about 20 nm. Both r value and N_2 flow rate have enormous impacts on morphology and microstructure of the nanoparticle, which correspondingly determined the electrochemical performance of the material. The VN/C hybrid nanoparticles exhibited high capacitive properties, and a maximum specific capacitance of 255.0 Fg^(-1) was achieved at a current density of 1.0 Ag^(-1) in 2 M KOH aqueous electrolyte and the potential range from 0 to -1.15 V. In addition,symmetrical supercapacitor fabricated with the as-synthesized VN/PCNPs presents a high specific capacitance of 43.5 F g^(-1) at 0.5 A g^(-1) based on the entire cell, and an energy density of 8.0 Wh kg^(-1) when the power density was 575 W kg^(-1). Even when the power density increased to 2831.5 W kg^(-1), the energy density still remained 6.1 Wh kg^(-1).展开更多
As a novel zero-dimensional(0D)material,metal carbides and/or carbonitrides(MXenes)quantum dots(MQDs)show unique photoluminescence properties and excellent biocompatibility.However,due to the limited synthesis methods...As a novel zero-dimensional(0D)material,metal carbides and/or carbonitrides(MXenes)quantum dots(MQDs)show unique photoluminescence properties and excellent biocompatibility.However,due to the limited synthesis methods and research to date,many new features have yet to be uncovered.Here,to explore their new properties and expand biological applications,chlorine and nitrogen co-doped Ti_(3)C_(2)MXene quantum dots(Cl,N-Ti_(3)C_(2)MQDs)were designed and synthesized,and their hydroxyl radical scavenging properties were investigated for the first time,revealing outstanding performance.Cl,N-Ti_(3)C_(2)MQDs was directly stripped from bulk Ti_(3)Al C_(2)by electrochemical etching,while N and Cl are successfully introduced to carbon skeleton and Ti boundaries in the etching process by electrochemical reactions between selected electrolytes and Ti_(3)C_(2)skeleton,respectively.The obtained Cl,N-Ti_(3)C_(2)MQDs exhibit large surface-to-volume ratio due to small particle size(ca.3.45 nm)and excellent higher scavenging activity(93.3%)and lower usage(12.5μg/m L)towards hydroxyl radicals than the previous reported graphene-based nanoparticles.The underlying mechanism of scavenging activity was also studied based on the reduction experiment with potassium permanganate(KMnO_(4)).The reducing ability of the intrinsic Ti_(3)C_(2)structure and electron donation of double dopants are the main contributors to the outstanding scavenging activity.展开更多
Although computational studies have demonstrated that metal ion doping can effectively narrow the bandgap of TiO_(2),the visible-light photoactivity of metal-doped TiO_(2) photoanodes is still far from satisfactory.He...Although computational studies have demonstrated that metal ion doping can effectively narrow the bandgap of TiO_(2),the visible-light photoactivity of metal-doped TiO_(2) photoanodes is still far from satisfactory.Herein,we report an effective strategy to activate the visible-light photoactivity of chromiumimplanted TiO_(2) via the incorporation of oxygen vacancies.The chromium-doped TiO_(2) activated by oxygen vacancies(Cr-TiO_(2)-vac)exhibited an incident photon-to-electron conversion efficiency(IPCE)of~6.8%at450 nm,which is one of the best values reported for metal-doped TiO_(2).Moreover,Cr-TiO_(2)-vac showed no obvious photocurrent decay after 100 h under visible-light illumination.展开更多
Hearing loss is a common military health problem and it is closely related to exposures to impulse noises from blast explosions and weapon firings. In a study based on test data of chinchillas and scaled to humans (Mi...Hearing loss is a common military health problem and it is closely related to exposures to impulse noises from blast explosions and weapon firings. In a study based on test data of chinchillas and scaled to humans (Military Medicine, 181: 59-69), an empirical injury model was constructed for exposure to multiple sound impulses of equal intensity. Building upon the empirical injury model, we conduct a mathematical study of the hearing loss injury caused by multiple impulses of non-uniform intensities. We adopt the theoretical framework of viewing individual sound exposures as separate injury causing events, and in that framework, we examine synergy for causing injury (fatigue) or negative synergy (immunity) or independence among a sequence of doses. Starting with the empirical logistic dose-response relation and the empirical dose combination rule, we show that for causing injury, a sequence of sound exposure events are not independent of each other. The phenomenological effect of a preceding event on the subsequent event is always immunity. We extend the empirical dose combination rule, which is applicable only in the case of homogeneous impulses of equal intensity, to accommodate the general case of multiple heterogeneous sound exposures with non-uniform intensities. In addition to studying and extending the empirical dose combination rule, we also explore the dose combination rule for the hypothetical case of independent events, and compare it with the empirical one. We measure the effect of immunity quantitatively using the immunity factor defined as the percentage of decrease in injury probability attributed to the sound exposure in the preceding event. Our main findings on the immunity factor are: 1) the immunity factor is primarily a function of the difference in SELA (A- weighted sound exposure level) between the two sound exposure events;it is virtually independent of the magnitude of the two SELA values as long as the difference is fixed;2) the immunity factor increases monotonically from 0 to 100% as the first dose is varied from being significantly below the second dose, to being moderately above the second dose. The extended dose-response formulation developed in this study provides a theoretical framework for assessing the injury risk in realistic situations.展开更多
A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection ...A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection diverge early in speciation and commonly cause reproductive incompatibilities has not been systematically investigated on a genome-wide scale. Here, I outline a research program for studying the genetic basis of speciation in broadcast spawning marine invertebrates that uses a priori genome-wide information on a large, unbiased sample of genes tested for positive selection. A targeted sequence capture approach is proposed that scores single-nucleotide polymorphisms （SNPs） in widely separated species populations at an early stage of allopatric divergence. The targeted capture of both coding and non-coding sequences enables SNPs to be characterized at known locations across the genome and at genes with known selective or neutral histories. The neutral coding and non-coding SNPs provide robust background distributions for identifying Fsm-outliers within genes that can, in principle, identify specific mutations experiencing diversifying selection. If natural hybridization occurs between species, the neutral coding and noncoding SNPs can provide a neutral admixture model for genomic clines analyses aimed at finding genes exhibiting strong blocks to introgression. Strongylocentrotid sea urchins are used as a model system to outline the approach but it can be used for any group that has a complete reference genome available.展开更多
We consider the hearing loss injury among subjects in a crowd with a wide spectrum of individual intrinsic injury probabilities due to biovariability. For multiple acoustic impulses, the observed injury risk of a crow...We consider the hearing loss injury among subjects in a crowd with a wide spectrum of individual intrinsic injury probabilities due to biovariability. For multiple acoustic impulses, the observed injury risk of a crowd vs the effective combined dose follows the logistic dose-response relation. The injury risk of a crowd is the average fraction of injured. The injury risk was measured in experiments as follows: each subject is individually exposed to a sequence of acoustic impulses of a given intensity and the injury is recorded;results of multiple individual subjects were assembled into data sets to mimic the response of a crowd. The effective combined dose was adjusted by varying the number of impulses in the sequence. The most prominent feature observed in experiments is that the injury risk of the crowd caused by multiple impulses is significantly less than the value predicted based on assumption that all impulses act independently in causing injury and all subjects in the crowd are statistically identical. Previously, in the case where all subjects are statistically identical (i.e., no biovariability), we interpreted the observed injury risk caused by multiple impulses in terms of the immunity effects of preceding impulses on subsequent impulses. In this study, we focus on the case where all sound exposure events act independently in causing injury regardless of whether one is preceded by another (i.e., no immunity effect). Instead, we explore the possibility of interpreting the observed logistic dose-response relation in the framework of biovariability of the crowd. Here biovariability means that subjects in the crowd have their own individual injury probabilities. That is, some subjects are biologically less or more susceptible to hearing loss injury than others. We derive analytically the distribution of individual injury probability that produces the observed logistic dose-response relation. For several parameter values, we prove that the derived distribution is mathematically a proper density function. We further study the asymptotic approximations for the density function and discuss their significance in practical numerical computation with finite precision arithmetic. Our mathematical analysis implies that the observed logistic dose-response relation can be theoretically explained in the framework of biovariability in the absence of immunity effect.展开更多
In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridiona...In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides.This process,when coupled with deep convection,could be an important part of the short-term atmospheric dynamics of water escape.However,the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated.In this work,we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide(DW1)at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database(MCD)5.3,a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well.We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years(MYs)24 to 32.Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1.The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons.During regional dust storms,the tidal transport induces only limited diurnal motion of the water vapor.However,the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid-to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm.The tidal transport process during these two global dust storms can induce opposite effects on water escape.展开更多
OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, a...OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.展开更多
By using a broadband Lg attenuation model developed for the Tibetan Plateau,we isolate source terms by removing attenuation and site effects from the observed Lg-wave displacement spectra of the M 7.0 earthquake that ...By using a broadband Lg attenuation model developed for the Tibetan Plateau,we isolate source terms by removing attenuation and site effects from the observed Lg-wave displacement spectra of the M 7.0 earthquake that occurred on August 8,2017,in Jiuzhaigou,China,and its aftershock sequence.Thus,the source parameters,including the scalar seismic moment,comer frequency and stress drop,of these events can be further estimated.The estimated stress drops vary from 47.1 kPa to 7149.6 kPa,with a median value of 59.4 kPa and most values falling between 50 kPa and 75 kPa.The estimated stress drops show significant spatial variations.Lower stress drops were mainly found close to the mainshock and on the seismogenic fault plane with large coseismic slip.In contrast,the highest stress drop was 7.1 MPa for the mainshock,and relatively large stress drops were also found for aftershocks away from the major seismogenic fault and at depths deeper than the zone with large coseismic slip.By using a statistical method,we found self-similarity among some of the aftershocks with a nearly constant stress drop.In contrast,the stress drop increased with the seismic moment for other aftershocks.The amount of stress released during earthquakes is a fundamental characteristic of the earthquake rupture process.As such,the stress drop represents a key parameter for improving our understanding of earthquake source physics.展开更多
Understanding the Cenozoic vertical-axis rotation in the Tibetan Plateau is crucial for continental dynamic evolution. Paleomagnetic and rock magnetic investigations were carried out for the Oligocene and Miocene cont...Understanding the Cenozoic vertical-axis rotation in the Tibetan Plateau is crucial for continental dynamic evolution. Paleomagnetic and rock magnetic investigations were carried out for the Oligocene and Miocene continental rocks of the Hoh Xii basin in order to better understand the tectonic rotations of central Tibet. The study area was located in the Tongtianhe area located in the southern part of the Hoh Xil basin and northern margin of the Tanggula thrust system in central-northern Tibet. A total of 160 independently oriented paleomagnetic samples were drilled from the Tongtianhe section for this study. The magnetic properties of magnetite and hematite have been recognized by measurements of magnetic susceptibility vs. temperature curves and unbiocking temperatures. The mean directions of the Oligocene Yaxicuo Group in stratigraphic coordinates （Declination/Inclination = 354.9°/29.3°, k = 33.0, a9s = 13.5°, N =5 Sites） and of the Miocene Wudaoliang Group in stratigraphic coordinates （Declination/Inclination = 3.60/36.4°, k = 161.0, a9s = 9.7°, N =3 Sites） pass reversal tests, indicating the primary nature of the characteristic magnetizations. Our results suggested that the sampled areas in the Tuotuohe depression of the Hoh Xil basin have undergone no paleomagnetically detectable rotations under single thrusting from the Tanggula thrust system. Our findings, together with constraints from other tectonic characteristics reported by previous paleomagnetic studies, suggest tectonic rotations in the Cuoredejia and Wudaoliang depressions of the Hoh Xil basin were affected by strike-slip faulting of the Fenghuo Shan-Nangqian thrust systems. A closer examination of geological data and different vertical-axis rotation magnitudes suggest the tectonic history of the Hoh Xil basin may be controlled by thrust and strike-slip faulting since the Eocene.展开更多
The lightweight,rechargeable lithium-ion battery is one of the dominant energy storage devices globally in portable electronics due to its high energy density,no memory effect,wide operating voltage,lightweight,and go...The lightweight,rechargeable lithium-ion battery is one of the dominant energy storage devices globally in portable electronics due to its high energy density,no memory effect,wide operating voltage,lightweight,and good charge efficiency.However,due to safety concerns,the depletion of lithium reserves,and the corresponding increase of cost,an alternative battery system becomes more and more desirable.To develop alternative battery systems with low cost and high material abundance,for example,sodium,magnesium,zinc,and calcium,it is important to understand the chemical and electronic structure of materials.Soft X-ray spectroscopy,for example,X-ray absorption spectroscopy(XAS),X-ray emission spectroscopy(XES),and resonant inelastic soft X-ray scattering(RIXS),is an element-specific technique with sensitivity to the local chemical environment and structural order of the element of interest.Modern soft X-ray systems enable operando experiments that can be applied to amorphous and crystalline samples,making it a powerful tool for studying the electronic and structural changes in electrode and electrolyte species.In this article,the application of in situ/operando(soft)X-ray spectroscopy in beyond lithium-ion batteries is reviewed to demonstrate how such spectroscopic characterizations could facilitate the interpretation of interfacial phenomena under in situ/operando condition and subsequent development of the beyond lithium-ion batteries.展开更多
We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is abov...We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is above the activation temperature. Withdrawal reflex occurs when the activated volume reaches a threshold. Previously we studied static beams with 3 types of power density distribution: Gaussian, super-Gaussian, and flat-top. We found that the flaptop is the best and the Gaussian is the worst in their performance with regard to 1) minimizing the time to withdrawal reflex, 2) minimizing the energy consumption and 3) minimizing the maximum temperature increase. The less-than-desirable performance of Gaussian beams is attributed to the uneven distribution of power density resulting in low energy efficiency: near the beam center the high power density does not contribute proportionally to increasing the activated volume;outside the beam effective radius the low power density fails to activate nociceptors. To overcome the drawbacks of Gaussian beams, in this study, we revolve a Gaussian beam around a fixed point to make the power density more uniformly distributed. We optimize the performance over two parameters: the spot size of static beam and the radius of beam revolution. We find that in comparison with a static Gaussian beam, a revolving Gaussian beam can reduce the energy consumption, and at the same time lower the maximum temperature.展开更多
Echolocating bats have developed advanced auditory perception systems, predominantly using acoustic signaling to communicate with each other They can emit a diverse range of social calls in complex behavioral contexts...Echolocating bats have developed advanced auditory perception systems, predominantly using acoustic signaling to communicate with each other They can emit a diverse range of social calls in complex behavioral contexts. This study examined the vocal repertoire of five pregnant big-footed myotis bats （Myotis macrodactylus）. In the process of clustering the last individual to return to the colony （LI） emitted social calls that correlated with behavior, as recorded on a PC-based digital recorder. These last individuals could emit 10 simple monosyllabic and 27 complex multisyllabic types of calls, constituting four types of syllables. The social calls were composed of highly stereotyped syllables, hierarchically organized by a common set of syllables. However, intra-specific variation was also found in the number of syllables, syllable order and patterns of syllable repetition across call renditions. Data were obtained to characterize the significant individual differences that existed in the maximum frequency and duration of calls. Time taken to return to the roost was negatively associated with the diversity of social calls. Our findings indicate that variability in social calls may be an effective strategy taken by individuals during reintegration into clusters of female M. macrodactylus.展开更多
In our recent work (Wang, Burgei, and Zhou, 2018) we studied the hearing loss injury among subjects in a crowd with a wide spectrum of heterogeneous individual injury susceptibility due to biovariability. The injury r...In our recent work (Wang, Burgei, and Zhou, 2018) we studied the hearing loss injury among subjects in a crowd with a wide spectrum of heterogeneous individual injury susceptibility due to biovariability. The injury risk of a crowd is defined as the average fraction of injured. We examined mathematically the injury risk of a crowd vs the number of acoustic impulses the crowd is exposed to, under the assumption that all impulses act independently in causing injury regardless of whether one is preceded by another. We concluded that the observed dose-response relation can be explained solely on the basis of biovariability in the form of heterogeneous susceptibility. We derived an analytical solution for the distribution density of injury susceptibility, as a power series expansion in terms of scaled log individual non-injury probability. While theoretically the power series converges for all argument values, in practical computations with IEEE double precision, at large argument values, the numerical accuracy of the power series summation is completely wiped out by the accumulation of round-off errors. In this study, we derive a general asymptotic approximation at large argument values, for the distribution density. The combination of the power series and the asymptotics provides a practical numerical tool for computing the distribution density. We then use this tool to verify numerically that the distribution obtained in our previous theoretical study is indeed a proper density. In addition, we will also develop a very efficient and accurate Pade approximation for the distribution density.展开更多
We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is abov...We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is above the activation temperature. Withdrawal reflex occurs when the activated volume reaches a threshold. We non-dimensionalize the problem to write the temperature as the product of a parameter-free function of non-dimensional variables and a function of beam parameters. This formulation allows studying beam parameters without knowing skin material parameters. We examine the effects of spot size, total power and distribution type of the electromagnetic beam on 3 quantities at reflex: 1) the time to reflex, 2) the maximum temperature increase, and 3) the total energy consumption. We find that the flat-top beam is the best, with the lowest energy consumption and the smallest maximum temperature increase. The Super-Gaussian beam is only slightly inferior to the flat-top. The Gaussian beam has by far the worst performance among these three.展开更多
This paper investigates the effect of launching multiple weapons against an area target of normally distributed elements. We provide an analytical form of the average damage fraction and then apply it to obtain optima...This paper investigates the effect of launching multiple weapons against an area target of normally distributed elements. We provide an analytical form of the average damage fraction and then apply it to obtain optimal aimpoints. To facilitate the computational efforts in practice, we also consider optimizations over given constrained patterns of aimpoints. Finally, we derive scaling laws for optimal aimpoints and optimal damage fraction with respect to the radius of the area target.展开更多
文摘Wild-land fires are a dynamic and destructive force in natural ecosystems. In recent decades, fire disturbances have increased concerns and awareness over significant economic loss and landscape change. The focus of this research was to study two northern California wild-land fires: Butte Humboldt Complex and Butte Lightning Complex of 2008 and assessment of vegetation recovery after the fires via ground based measurements and utilization of Landsat 5 imagery and analysis software to assess landscape change. Multi-temporal and burn severity dynamics and assessment through satellite imagery were used to visually ascertain levels of landscape change, under two temporal scales. Visual interpretation indicated noticeable levels of landscape change and relevant insight into the magnitude and impact of both wild-land fires. Normalized Burn Ratio (NBR) and delta NBR (DNBR) data allowed for quantitative analysis of burn severity levels. DNBR results indicate low severity and low re-growth for Butte Humboldt Complex “burned center” subplots. In contrast, DNBR values for Butte Lightning Complex “burned center” subplots indicated low-moderate burn severity levels.
基金funded by the Environmental Seed Arrival and Interspecific Associations in Seedling Sciences Program of the Smithsonian Institutionthe National Science Foundation (DEB-0075102,DEB-0823728,DEB-0640386,DEB-1242622,DEB-1464389)the Andrew Mellon Foundation,The Ohio State University,and Yale University
文摘Background The full lifespan of long-lived trees includes a seedling phase,during which a seed germinates and grows to a size large enough to be measured in forest inventories.Seedling populations are usually studied separately from adult trees,and the seedling lifespan,from seed to sapling,is poorly known.In the 50-ha Barro Colorado forest plot,we started intensive censuses of seeds and seedlings in 1994 in order to merge seedling and adult demography and document complete lifespans.Methods In 17 species abundant in seedling censuses,we subdivided populations into six size classes from seed to 1cm dbh,including seeds plus five seedling stages.The smallest seedling class was subdivided by age.Censuses in two consecutive years provided transition matrices describing the probability that a seedling in one stage moved to another one year later.For each species,we averaged the transition matrix across 25 censuses and used it to project the seedling lifespan,from seed until 1cm dbh or death.Results The predicted mean survival rate of seeds to 1cm dbh varied 1000-fold across species,from 2.9×10^(−6)to 4.4×10^(−3);the median was 2.0×10^(−4).The seedling lifespan,or the average time it takes a seed to grow to 1cm dbh,varied across species from 5.1 to 53.1 years,with a median of 20.3 years.In the median species,the 10%fastest-growing seeds would reach 1cm dbh in 9.0 years,and the slowest 10%in 34.6 years.Conclusions Combining seedling results with our previous study of lifespan after 1cm dbh,we estimate that the focal species have full lifespans varying from 41 years in a gap-demanding pioneer to 320 years in one shade-tolerant species.Lifetime demography can contribute precise survival rates and lifespans to forestry models.
基金the National Science Foundation,NASA-UARC,US Armythe Lawrence Scholar Program(formerly known as Student Employee Graduate Research Fellowship).
文摘Nanomaterials possess intriguing optical properties that depend sensitively on size, shape, and material content of the structures. Controlling such structural characteristics of the nanostructures allows the tailoring of their physical and chemical properties, e.g. optical, electronic, and catalytic, to achieve what is desired lot specific applications of interest. This review will cover the development of various shapes for silver and gold nanomaterials with emphasis on their relation to optical properties. Examples of various modern synthetic methods and characterization techniques are highlighted. The influence of the metal nanomaterial＇s shape and optical absorption on surface enhanced Raman scattering （SERS） and a final note on new emerging applications of metal nanostructures are also discussed.
基金supported by the National Natural Science Foundation of China (51203071, 51363014 and 51463012)China Postdoctoral Science Foundation (2014M552509, 2015T81064)+2 种基金Natural Science Funds of the Gansu Province (2015GS05123)Program for Hongliu Distinguished Young Scholars in Lanzhou University of Technology (J201402)University Scientific Research Project of Gansu Province (2014B-025)
文摘Hybrid materials of vanadium nitride and porous carbon nanoparticles(VN/PCNPs) were fabricated by a facile pyrolysis process of vanadium pentoxide(V_2O_5) xerogel and melamine at relatively low temperature of 800 °C for supercapacitor application. The effects of the feed ratio of V_2O_5 to melamine(r), and nitrogen flow rate on the microstructure and electrochemical performance were also investigated. It was found that the size of the as-synthesized nanoparticles is about 20 nm. Both r value and N_2 flow rate have enormous impacts on morphology and microstructure of the nanoparticle, which correspondingly determined the electrochemical performance of the material. The VN/C hybrid nanoparticles exhibited high capacitive properties, and a maximum specific capacitance of 255.0 Fg^(-1) was achieved at a current density of 1.0 Ag^(-1) in 2 M KOH aqueous electrolyte and the potential range from 0 to -1.15 V. In addition,symmetrical supercapacitor fabricated with the as-synthesized VN/PCNPs presents a high specific capacitance of 43.5 F g^(-1) at 0.5 A g^(-1) based on the entire cell, and an energy density of 8.0 Wh kg^(-1) when the power density was 575 W kg^(-1). Even when the power density increased to 2831.5 W kg^(-1), the energy density still remained 6.1 Wh kg^(-1).
基金National Natural Science Foundation of China(Grant No.21674011,21404008)Beijing Municipal Natural Science Foundation(Grant No.2172040)+1 种基金Beijing Organization department outstanding talented person project(2013D009006000001)the Fundamental Research Funds for the Central Universities(FRF-GF-17-B11)。
文摘As a novel zero-dimensional(0D)material,metal carbides and/or carbonitrides(MXenes)quantum dots(MQDs)show unique photoluminescence properties and excellent biocompatibility.However,due to the limited synthesis methods and research to date,many new features have yet to be uncovered.Here,to explore their new properties and expand biological applications,chlorine and nitrogen co-doped Ti_(3)C_(2)MXene quantum dots(Cl,N-Ti_(3)C_(2)MQDs)were designed and synthesized,and their hydroxyl radical scavenging properties were investigated for the first time,revealing outstanding performance.Cl,N-Ti_(3)C_(2)MQDs was directly stripped from bulk Ti_(3)Al C_(2)by electrochemical etching,while N and Cl are successfully introduced to carbon skeleton and Ti boundaries in the etching process by electrochemical reactions between selected electrolytes and Ti_(3)C_(2)skeleton,respectively.The obtained Cl,N-Ti_(3)C_(2)MQDs exhibit large surface-to-volume ratio due to small particle size(ca.3.45 nm)and excellent higher scavenging activity(93.3%)and lower usage(12.5μg/m L)towards hydroxyl radicals than the previous reported graphene-based nanoparticles.The underlying mechanism of scavenging activity was also studied based on the reduction experiment with potassium permanganate(KMnO_(4)).The reducing ability of the intrinsic Ti_(3)C_(2)structure and electron donation of double dopants are the main contributors to the outstanding scavenging activity.
基金financially supported by the National Natural Science Foundation of China(U1867215,11722543,11875211,U1932134)the Suzhou Key Industrial Technology Innovation Project(SYG201828)+2 种基金the Hubei Provincial Natural Science Foundation(2019CFA036)the Fundamental Research Funds for the Central Universities(2042020kf0211)the financial support from the National Science Foundation(U.S.)under grant no.DMR-2003563。
文摘Although computational studies have demonstrated that metal ion doping can effectively narrow the bandgap of TiO_(2),the visible-light photoactivity of metal-doped TiO_(2) photoanodes is still far from satisfactory.Herein,we report an effective strategy to activate the visible-light photoactivity of chromiumimplanted TiO_(2) via the incorporation of oxygen vacancies.The chromium-doped TiO_(2) activated by oxygen vacancies(Cr-TiO_(2)-vac)exhibited an incident photon-to-electron conversion efficiency(IPCE)of~6.8%at450 nm,which is one of the best values reported for metal-doped TiO_(2).Moreover,Cr-TiO_(2)-vac showed no obvious photocurrent decay after 100 h under visible-light illumination.
文摘Hearing loss is a common military health problem and it is closely related to exposures to impulse noises from blast explosions and weapon firings. In a study based on test data of chinchillas and scaled to humans (Military Medicine, 181: 59-69), an empirical injury model was constructed for exposure to multiple sound impulses of equal intensity. Building upon the empirical injury model, we conduct a mathematical study of the hearing loss injury caused by multiple impulses of non-uniform intensities. We adopt the theoretical framework of viewing individual sound exposures as separate injury causing events, and in that framework, we examine synergy for causing injury (fatigue) or negative synergy (immunity) or independence among a sequence of doses. Starting with the empirical logistic dose-response relation and the empirical dose combination rule, we show that for causing injury, a sequence of sound exposure events are not independent of each other. The phenomenological effect of a preceding event on the subsequent event is always immunity. We extend the empirical dose combination rule, which is applicable only in the case of homogeneous impulses of equal intensity, to accommodate the general case of multiple heterogeneous sound exposures with non-uniform intensities. In addition to studying and extending the empirical dose combination rule, we also explore the dose combination rule for the hypothetical case of independent events, and compare it with the empirical one. We measure the effect of immunity quantitatively using the immunity factor defined as the percentage of decrease in injury probability attributed to the sound exposure in the preceding event. Our main findings on the immunity factor are: 1) the immunity factor is primarily a function of the difference in SELA (A- weighted sound exposure level) between the two sound exposure events;it is virtually independent of the magnitude of the two SELA values as long as the difference is fixed;2) the immunity factor increases monotonically from 0 to 100% as the first dose is varied from being significantly below the second dose, to being moderately above the second dose. The extended dose-response formulation developed in this study provides a theoretical framework for assessing the injury risk in realistic situations.
基金Acknowledgments I would like to thank Nicolas Bierne for the opportunity of contributing to the Special Column： Population Genomics in the Sea. Helpful comments on the manuscript were provided by Nicolas Bierne and two anonymous reviewers.Partial funding for the work described on strongylocentrotid sea urchins was provided by the Natinal Science Foundation （DEB-1011061 ）.
文摘A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection diverge early in speciation and commonly cause reproductive incompatibilities has not been systematically investigated on a genome-wide scale. Here, I outline a research program for studying the genetic basis of speciation in broadcast spawning marine invertebrates that uses a priori genome-wide information on a large, unbiased sample of genes tested for positive selection. A targeted sequence capture approach is proposed that scores single-nucleotide polymorphisms （SNPs） in widely separated species populations at an early stage of allopatric divergence. The targeted capture of both coding and non-coding sequences enables SNPs to be characterized at known locations across the genome and at genes with known selective or neutral histories. The neutral coding and non-coding SNPs provide robust background distributions for identifying Fsm-outliers within genes that can, in principle, identify specific mutations experiencing diversifying selection. If natural hybridization occurs between species, the neutral coding and noncoding SNPs can provide a neutral admixture model for genomic clines analyses aimed at finding genes exhibiting strong blocks to introgression. Strongylocentrotid sea urchins are used as a model system to outline the approach but it can be used for any group that has a complete reference genome available.
文摘We consider the hearing loss injury among subjects in a crowd with a wide spectrum of individual intrinsic injury probabilities due to biovariability. For multiple acoustic impulses, the observed injury risk of a crowd vs the effective combined dose follows the logistic dose-response relation. The injury risk of a crowd is the average fraction of injured. The injury risk was measured in experiments as follows: each subject is individually exposed to a sequence of acoustic impulses of a given intensity and the injury is recorded;results of multiple individual subjects were assembled into data sets to mimic the response of a crowd. The effective combined dose was adjusted by varying the number of impulses in the sequence. The most prominent feature observed in experiments is that the injury risk of the crowd caused by multiple impulses is significantly less than the value predicted based on assumption that all impulses act independently in causing injury and all subjects in the crowd are statistically identical. Previously, in the case where all subjects are statistically identical (i.e., no biovariability), we interpreted the observed injury risk caused by multiple impulses in terms of the immunity effects of preceding impulses on subsequent impulses. In this study, we focus on the case where all sound exposure events act independently in causing injury regardless of whether one is preceded by another (i.e., no immunity effect). Instead, we explore the possibility of interpreting the observed logistic dose-response relation in the framework of biovariability of the crowd. Here biovariability means that subjects in the crowd have their own individual injury probabilities. That is, some subjects are biologically less or more susceptible to hearing loss injury than others. We derive analytically the distribution of individual injury probability that produces the observed logistic dose-response relation. For several parameter values, we prove that the derived distribution is mathematically a proper density function. We further study the asymptotic approximations for the density function and discuss their significance in practical numerical computation with finite precision arithmetic. Our mathematical analysis implies that the observed logistic dose-response relation can be theoretically explained in the framework of biovariability in the absence of immunity effect.
基金This work is supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(grant XDB41000000)the pre-research project on Civil Aerospace Technologies of the China National Space Administration(grant D020105).T.L.and J.C.acknowledge support from the National Natural Science Foundation of China through grants 41525015 and 41774186 to J.C.,and grants 41674149 and 41974175 to T.L.X.Z.acknowledges support from the National Science Foundation(grant AST1740921).J.L.acknowledges support from the Open Research Program of the Chinese Academy of Sciences Key Laboratory of Geospace Environment.Z.W.acknowledges support from the Guangdong Basic and Applied Basic Research Foundation(grant 2019A1515110815)the Chinese Academy of Sciences Key Laboratory of Lunar and Deep Space Exploration(grant LDSE201803).We would like to thank the MCD teams for making the MCD 5.3 data sets available online at http://www-mars.lmd.jussieu.fr/mars/access.html.
文摘In recent studies of the Martian atmosphere,strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms,which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides.This process,when coupled with deep convection,could be an important part of the short-term atmospheric dynamics of water escape.However,the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated.In this work,we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide(DW1)at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database(MCD)5.3,a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well.We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years(MYs)24 to 32.Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1.The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons.During regional dust storms,the tidal transport induces only limited diurnal motion of the water vapor.However,the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid-to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm.The tidal transport process during these two global dust storms can induce opposite effects on water escape.
文摘OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.
基金The authors are grateful to the two anonymous reviewers,whose constructive comments have improved this paperThis work was supported by the Special Fund of China Seismic Experimental Site(Nos.2019CSES0103,2018CESE0102 and 2016CESE0203)+1 种基金the National Natural Science Foundation of China(Nos.41630210,41674060 and 41974054)the 13th Five-year Informatization Plan of Chinese Academy of Sciences(grant No.XXH13505-06)。
文摘By using a broadband Lg attenuation model developed for the Tibetan Plateau,we isolate source terms by removing attenuation and site effects from the observed Lg-wave displacement spectra of the M 7.0 earthquake that occurred on August 8,2017,in Jiuzhaigou,China,and its aftershock sequence.Thus,the source parameters,including the scalar seismic moment,comer frequency and stress drop,of these events can be further estimated.The estimated stress drops vary from 47.1 kPa to 7149.6 kPa,with a median value of 59.4 kPa and most values falling between 50 kPa and 75 kPa.The estimated stress drops show significant spatial variations.Lower stress drops were mainly found close to the mainshock and on the seismogenic fault plane with large coseismic slip.In contrast,the highest stress drop was 7.1 MPa for the mainshock,and relatively large stress drops were also found for aftershocks away from the major seismogenic fault and at depths deeper than the zone with large coseismic slip.By using a statistical method,we found self-similarity among some of the aftershocks with a nearly constant stress drop.In contrast,the stress drop increased with the seismic moment for other aftershocks.The amount of stress released during earthquakes is a fundamental characteristic of the earthquake rupture process.As such,the stress drop represents a key parameter for improving our understanding of earthquake source physics.
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.41102064 and 41230313US National Science Foundation project EAR 1250444
文摘Understanding the Cenozoic vertical-axis rotation in the Tibetan Plateau is crucial for continental dynamic evolution. Paleomagnetic and rock magnetic investigations were carried out for the Oligocene and Miocene continental rocks of the Hoh Xii basin in order to better understand the tectonic rotations of central Tibet. The study area was located in the Tongtianhe area located in the southern part of the Hoh Xil basin and northern margin of the Tanggula thrust system in central-northern Tibet. A total of 160 independently oriented paleomagnetic samples were drilled from the Tongtianhe section for this study. The magnetic properties of magnetite and hematite have been recognized by measurements of magnetic susceptibility vs. temperature curves and unbiocking temperatures. The mean directions of the Oligocene Yaxicuo Group in stratigraphic coordinates （Declination/Inclination = 354.9°/29.3°, k = 33.0, a9s = 13.5°, N =5 Sites） and of the Miocene Wudaoliang Group in stratigraphic coordinates （Declination/Inclination = 3.60/36.4°, k = 161.0, a9s = 9.7°, N =3 Sites） pass reversal tests, indicating the primary nature of the characteristic magnetizations. Our results suggested that the sampled areas in the Tuotuohe depression of the Hoh Xil basin have undergone no paleomagnetically detectable rotations under single thrusting from the Tanggula thrust system. Our findings, together with constraints from other tectonic characteristics reported by previous paleomagnetic studies, suggest tectonic rotations in the Cuoredejia and Wudaoliang depressions of the Hoh Xil basin were affected by strike-slip faulting of the Fenghuo Shan-Nangqian thrust systems. A closer examination of geological data and different vertical-axis rotation magnitudes suggest the tectonic history of the Hoh Xil basin may be controlled by thrust and strike-slip faulting since the Eocene.
基金supported as part of the Joint Center for Energy Storage Research(JCESR)an Energy Innovation Hub funded by the U.S.Department of Energy(DOE),Office of Science,Basic Energy Sciences
文摘The lightweight,rechargeable lithium-ion battery is one of the dominant energy storage devices globally in portable electronics due to its high energy density,no memory effect,wide operating voltage,lightweight,and good charge efficiency.However,due to safety concerns,the depletion of lithium reserves,and the corresponding increase of cost,an alternative battery system becomes more and more desirable.To develop alternative battery systems with low cost and high material abundance,for example,sodium,magnesium,zinc,and calcium,it is important to understand the chemical and electronic structure of materials.Soft X-ray spectroscopy,for example,X-ray absorption spectroscopy(XAS),X-ray emission spectroscopy(XES),and resonant inelastic soft X-ray scattering(RIXS),is an element-specific technique with sensitivity to the local chemical environment and structural order of the element of interest.Modern soft X-ray systems enable operando experiments that can be applied to amorphous and crystalline samples,making it a powerful tool for studying the electronic and structural changes in electrode and electrolyte species.In this article,the application of in situ/operando(soft)X-ray spectroscopy in beyond lithium-ion batteries is reviewed to demonstrate how such spectroscopic characterizations could facilitate the interpretation of interfacial phenomena under in situ/operando condition and subsequent development of the beyond lithium-ion batteries.
文摘We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is above the activation temperature. Withdrawal reflex occurs when the activated volume reaches a threshold. Previously we studied static beams with 3 types of power density distribution: Gaussian, super-Gaussian, and flat-top. We found that the flaptop is the best and the Gaussian is the worst in their performance with regard to 1) minimizing the time to withdrawal reflex, 2) minimizing the energy consumption and 3) minimizing the maximum temperature increase. The less-than-desirable performance of Gaussian beams is attributed to the uneven distribution of power density resulting in low energy efficiency: near the beam center the high power density does not contribute proportionally to increasing the activated volume;outside the beam effective radius the low power density fails to activate nociceptors. To overcome the drawbacks of Gaussian beams, in this study, we revolve a Gaussian beam around a fixed point to make the power density more uniformly distributed. We optimize the performance over two parameters: the spot size of static beam and the radius of beam revolution. We find that in comparison with a static Gaussian beam, a revolving Gaussian beam can reduce the energy consumption, and at the same time lower the maximum temperature.
基金supported by the National Natural Science Foundation of China(31700319,31670390)the Fundamental Research Funds for the Central Universities(2412017QD026)+1 种基金U.S National Science Foundation(NSF)(DEB-1115895)the NSF East Asian Pacific Summer Institute Program IIA-1415092
文摘Echolocating bats have developed advanced auditory perception systems, predominantly using acoustic signaling to communicate with each other They can emit a diverse range of social calls in complex behavioral contexts. This study examined the vocal repertoire of five pregnant big-footed myotis bats （Myotis macrodactylus）. In the process of clustering the last individual to return to the colony （LI） emitted social calls that correlated with behavior, as recorded on a PC-based digital recorder. These last individuals could emit 10 simple monosyllabic and 27 complex multisyllabic types of calls, constituting four types of syllables. The social calls were composed of highly stereotyped syllables, hierarchically organized by a common set of syllables. However, intra-specific variation was also found in the number of syllables, syllable order and patterns of syllable repetition across call renditions. Data were obtained to characterize the significant individual differences that existed in the maximum frequency and duration of calls. Time taken to return to the roost was negatively associated with the diversity of social calls. Our findings indicate that variability in social calls may be an effective strategy taken by individuals during reintegration into clusters of female M. macrodactylus.
文摘In our recent work (Wang, Burgei, and Zhou, 2018) we studied the hearing loss injury among subjects in a crowd with a wide spectrum of heterogeneous individual injury susceptibility due to biovariability. The injury risk of a crowd is defined as the average fraction of injured. We examined mathematically the injury risk of a crowd vs the number of acoustic impulses the crowd is exposed to, under the assumption that all impulses act independently in causing injury regardless of whether one is preceded by another. We concluded that the observed dose-response relation can be explained solely on the basis of biovariability in the form of heterogeneous susceptibility. We derived an analytical solution for the distribution density of injury susceptibility, as a power series expansion in terms of scaled log individual non-injury probability. While theoretically the power series converges for all argument values, in practical computations with IEEE double precision, at large argument values, the numerical accuracy of the power series summation is completely wiped out by the accumulation of round-off errors. In this study, we derive a general asymptotic approximation at large argument values, for the distribution density. The combination of the power series and the asymptotics provides a practical numerical tool for computing the distribution density. We then use this tool to verify numerically that the distribution obtained in our previous theoretical study is indeed a proper density. In addition, we will also develop a very efficient and accurate Pade approximation for the distribution density.
文摘We consider the problem of inducing withdrawal reflex on a test subject by exposing the subject’s skin to an electromagnetic beam. Heat-sensitive nociceptors in the skin are activated wherever the temperature is above the activation temperature. Withdrawal reflex occurs when the activated volume reaches a threshold. We non-dimensionalize the problem to write the temperature as the product of a parameter-free function of non-dimensional variables and a function of beam parameters. This formulation allows studying beam parameters without knowing skin material parameters. We examine the effects of spot size, total power and distribution type of the electromagnetic beam on 3 quantities at reflex: 1) the time to reflex, 2) the maximum temperature increase, and 3) the total energy consumption. We find that the flat-top beam is the best, with the lowest energy consumption and the smallest maximum temperature increase. The Super-Gaussian beam is only slightly inferior to the flat-top. The Gaussian beam has by far the worst performance among these three.
文摘This paper investigates the effect of launching multiple weapons against an area target of normally distributed elements. We provide an analytical form of the average damage fraction and then apply it to obtain optimal aimpoints. To facilitate the computational efforts in practice, we also consider optimizations over given constrained patterns of aimpoints. Finally, we derive scaling laws for optimal aimpoints and optimal damage fraction with respect to the radius of the area target.
