This work presents the results of the exact computation of (180)<sup>3</sup> = 5,832,000 third-order mixed sensitivities of the leakage response of a polyethylene-reflected plutonium (PERP) experimental be...This work presents the results of the exact computation of (180)<sup>3</sup> = 5,832,000 third-order mixed sensitivities of the leakage response of a polyethylene-reflected plutonium (PERP) experimental benchmark with respect to the benchmark’s 180 microscopic total cross sections. This computation was made possible by applying the Third-Order Adjoint Sensitivity Analysis Methodology developed by Cacuci. The numerical results obtained in this work revealed that many of the 3<sup>rd</sup>-order sensitivities are significantly larger than their corresponding 1<sup>st</sup>- and 2<sup>nd</sup>-order ones, which is contrary to the widely held belief that higher-order sensitivities are all much smaller and hence less important than the first-order ones, for reactor physics systems. In particular, the largest 3<sup>rd</sup>-order relative sensitivity is the mixed sensitivity <img src="Edit_754b8437-dfdf-487d-af68-c78c637e6d4e.png" width="180" height="24" alt="" />of the PERP leakage response with respect to the lowest energy-group (30) total cross sections of <sup>1</sup>H (“isotope 6”) and <sup>239</sup>Pu (“isotope 1”). These two isotopes are shown in this work to be the two most important parameters affecting the PERP benchmark’s leakage response. By comparison, the largest 1<sup>st</sup>-order sensitivity is that of the PERP leakage response with respect to the lowest energy-group total cross section of isotope <sup>1</sup>H, having the value <img src="Edit_a5cfcc11-6a99-41ee-b844-a5ee84b454b3.png" width="100" height="24" alt="" />, while the largest 2<sup>nd</sup>-order sensitivity is <img src="Edit_05166a2b-97f7-43f1-98ff-b21368c00228.png" width="120" height="22" alt="" />. The 3<sup>rd</sup>-order sensitivity analysis presented in this work is the first ever such analysis in the field of reactor physics. The consequences of the results presented in this work on the uncertainty analysis of the PERP benchmark’s leakage response will be presented in a subsequent work.展开更多
This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>...This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>nd</sup>-order response sensitivities to uncertain parameters and domain boundaries of linear systems. The model’s response (<em>i.e.</em>, model result of interest) is a generic nonlinear function of the model’s forward and adjoint state functions, and also depends on the imprecisely known boundaries and model parameters. In the practically important particular case when the response is a scalar-valued functional of the forward and adjoint state functions characterizing a model comprising N parameters, the 2<sup>nd</sup>-CASAM requires a single large-scale computation using the First-Level Adjoint Sensitivity System (1<sup>st</sup>-LASS) for obtaining all of the first-order response sensitivities, and at most N large-scale computations using the Second-Level Adjoint Sensitivity System (2<sup>nd</sup>-LASS) for obtaining exactly all of the second-order response sensitivities. In contradistinction, forward other methods would require (<em>N</em>2/2 + 3 <em>N</em>/2) large-scale computations for obtaining all of the first- and second-order sensitivities. This work also shows that constructing and solving the 2<sup>nd</sup>-LASS requires very little additional effort beyond the construction of the 1<sup>st</sup>-LASS needed for computing the first-order sensitivities. Solving the equations underlying the 1<sup>st</sup>-LASS and 2<sup>nd</sup>-LASS requires the same computational solvers as needed for solving (<em>i.e.</em>, “inverting”) either the forward or the adjoint linear operators underlying the initial model. Therefore, the same computer software and “solvers” used for solving the original system of equations can also be used for solving the 1<sup>st</sup>-LASS and the 2<sup>nd</sup>-LASS. Since neither the 1<sup>st</sup>-LASS nor the 2<sup>nd</sup>-LASS involves any differentials of the operators underlying the original system, the 1<sup>st</sup>-LASS is designated as a “<u>first-level</u>” (as opposed to a “first-order”) adjoint sensitivity system, while the 2<sup>nd</sup>-LASS is designated as a “<u>second-level</u>” (rather than a “second-order”) adjoint sensitivity system. Mixed second-order response sensitivities involving boundary parameters may arise from all source terms of the 2<sup>nd</sup>-LASS that involve the imprecisely known boundary parameters. Notably, the 2<sup>nd</sup>-LASS encompasses an automatic, inherent, and independent “solution verification” mechanism of the correctness and accuracy of the 2nd-level adjoint functions needed for the efficient and exact computation of the second-order sensitivities.展开更多
Due to global warming, glaciers on the Tibetan Plateau(TP) are experiencing widespread shrinkage; however, the mechanisms controlling glacier variations across the TP are still rather unclear, especially on the northe...Due to global warming, glaciers on the Tibetan Plateau(TP) are experiencing widespread shrinkage; however, the mechanisms controlling glacier variations across the TP are still rather unclear, especially on the northeastern TP. In this study, a physically based, distributed surface-energy and mass-balance model was used to simulate glacier mass balance forced by meteorological data. The model was applied to Laohugou No. 12 Glacier, western Qilian Mountains, China, during2010~2012. The simulated albedo and mass balance were validated and calibrated by in situ measurements. The simulated annual glacier-wide mass balances were-385 mm water equivalent(w.e.) in 2010/2011 and-232 mm w.e. in 2011/2012,respectively. The mean equilibrium-line altitude(ELA) was 5,015 m a.s.l., during 2010~2012, which ascended by 215 m compared to that in the 1970 s. The mean accumulation area ratio(AAR) was 39% during the two years. Climatic-sensitivity experiments indicated that the change of glacier mass balance resulting from a 1.5 °C increase in air temperature could be offset by a 30% increase in annual precipitation. The glacier mass balance varied linearly with precipitation, at a rate of130 mm w.e. per 10% change in total precipitation.展开更多
The accurate diagnosis of tuberculosis caused by members of the Mycobacterium tuberculosis complex (MTBC) has remained a major challenge in clinical laboratories world-wide. Several studies have evaluated the use of h...The accurate diagnosis of tuberculosis caused by members of the Mycobacterium tuberculosis complex (MTBC) has remained a major challenge in clinical laboratories world-wide. Several studies have evaluated the use of highly specific in-house PCR assays targeting the IS6110, hupB, rpoB, oxyR, and IS1081 genes in the detection of MTBC species with reports on variable sensitivities depending on the geographical sourcing of isolates. In the present investigations, we evaluated the sensitivities of these PCR assays on 125 MTBC cultured isolates from five (West, Centre, Littoral, North West and South West) of the ten regions of Cameroon. Of this number, 124 (99.2%), 117 (93.6%), 123 (99.1%), 119 (95.2%) and 118 (94.4%) were positive by the IS6110, hupB, rpoB, oxyR, and IS1081-based PCR assays respectively. A total of 110 (88%) of the cultured isolates were also identified as MTBC by standard biochemical tests. Of this number, 109 (99.1%), 104 (94.5%), 109 (99.1%), 106 (96.4%) and 104 (94.5%) were positive in the IS6110, hupB, rpoB, oxyR, and IS1081-based PCR assays respectively. Concordant PCR results were obtained for 108 of the 125 samples. The 15 isolates that were negative biochemically scored sensitivities ranging from 100% (for the IS6110 assay) to 86.7% (for the hupB and oxyR assay). The combination of the IS6110 assay, which turned out to be the most sensitive, and each of the other assays gave 100% sensitivity. We conclude that the combined targeting of the IS6110 and rpoB genes is likely to yield the most sensitive PCR procedure for the diagnosis of MTBC infection in the five regions of Cameroon.展开更多
Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that disc...Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.展开更多
Relative sensitivities of 30 species of common woody plants to simulated acid rain with pH values of 2.0, 2.5, 3.0, 3.5, 4.5 and control were studied. The results showed that 6 species of these plants were sensitive t...Relative sensitivities of 30 species of common woody plants to simulated acid rain with pH values of 2.0, 2.5, 3.0, 3.5, 4.5 and control were studied. The results showed that 6 species of these plants were sensitive to simulated acid rain. The moderate included 18 species. The resistant included 6. Relative sensitivities to ambient acid rain and air pollutants and visible injury degree of 30 species of common woody plants in Chongqing City were investigated. Results showed that 6 species with foliage lesion rate at above 10 percent were sensitive, that 6 species with no lesion were resistant and that other 18 species with lesion at 10 percent below were moderate. Other 7 cities (Guiyang, Zunyi, Duyun, Changsha, Zhuzhou, Liuzhou and Guilin City) were also investigated and results were consistent with those of Chongqing City. The experimental and investigated results showed relative sensitivities and visible injury degree of woody plants to simulated acid rain were consistent with those of the woody展开更多
We investigated the sensitivities of atom interferometers in the usual fringe-scanning method(FSM) versus the fringelocking method(FLM). The theoretical analysis shows that for typical noises in atom interferometers, ...We investigated the sensitivities of atom interferometers in the usual fringe-scanning method(FSM) versus the fringelocking method(FLM). The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.展开更多
This work extends to fourth-order previously published work on developing the adjoint sensitivity and uncertainty analysis of the numerical model of a <u>p</u>oly<u>e</u>thylene-<u>r</...This work extends to fourth-order previously published work on developing the adjoint sensitivity and uncertainty analysis of the numerical model of a <u>p</u>oly<u>e</u>thylene-<u>r</u>eflected <u>p</u>lutonium (acronym: PERP) OECD/NEA reactor physics benchmark. Previous works showed that the third-order sensitivities of the PERP leakage response with respect to these total microscopic cross sections are far larger than the corresponding 1<sup>st</sup>-order and 2<sup>nd</sup>-order ones, thereby having the largest impact on the uncertainties induced in the PERP benchmark’s response. This finding has motivated the development of the original 4<sup>th</sup>-order formulas presented in this work, which are valid not only for the PERP benchmark but can also be used for computing the 4<sup>th</sup>-order sensitivities of response of any nuclear system involving fissionable material and internal or external neutron sources. Subsequent works will use the adjoint-based mathematical expressions obtained in this work to compute exactly and efficiently the numerical values of the largest fourth-order sensitivities of the PERP benchmark’s response to the total microscopic cross sections, and use them for a pioneering fourth-order uncertainty analysis of the PERP benchmark’s response.展开更多
The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodica...The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodically time-varying mesh stiffness, the nonlinear tooth backlash, the lump-parameter model of the gear system is developed with one rotational and two translational freedoms of each gear. The eigen-values and eigenvectors are derived and analyzed on the basis of the real modal theory. The sensitivities of natural frequencies to design parameters including supporting and meshing stiffnesses, gear masses, and moments of inertia by the direct differential method are also calculated. The results show the quantitative and qualitative impact of the parameters to the natural characteristics of the gear system. Furthermore, the periodic steady state solutions are obtained by the numerical approach based on the nonlinear model. These results are employed to gain insights into the primary controlling parameters, to forecast the severity of the dynamic response, and to assess the acceptability of the gear design.展开更多
In this paper, structural static design is considered as a kind of inverse algebraiceigenvalue problem. It is the most important task for for the inverse problem to compute thesensitivities of eigenvalues and eigenvec...In this paper, structural static design is considered as a kind of inverse algebraiceigenvalue problem. It is the most important task for for the inverse problem to compute thesensitivities of eigenvalues and eigenvectors. Therefore. a complete set of higher ordersensitivity expressions has been presented based on the complex variables theory. Theseexpressions have solid mathematical foundation and practical significance.展开更多
The spark energy, E ES , required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the E ES values and impact sensitivity, expressed as drop energies E d of the...The spark energy, E ES , required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the E ES values and impact sensitivity, expressed as drop energies E d of the "first reaction", were established and discussed. The conclusion is made that depending on intermolecular interaction factors in crystals of energetic materials, the mechanism of impact energy transition to the reaction centre of their molecule can be differ from that of transition of energy of electric spark.展开更多
Cellular environments are in essence stochastic, owing to the random character of the biochemical reaction events in a single cell. Stochastic fluctuations may substantially contribute to the dynamics of systems with ...Cellular environments are in essence stochastic, owing to the random character of the biochemical reaction events in a single cell. Stochastic fluctuations may substantially contribute to the dynamics of systems with small copy numbers of some biochemical species. Then, stochastic models are indispensable for properly portraying the behaviour of the system. Sensitivity analysis is one of the central tools for studying stochastic models of cellular dynamics. Here, we propose some finite-difference strategies for estimating parametric sensitivities of higher-order moments of the system state for stochastic discrete biochemical kinetic models. To reduce the variance of the sensitivity estimator, we employ various coupling techniques. The advantages of the proposed methods are illustrated in several models of biochemical systems of practical relevance.展开更多
Nano hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX) was prepared using a bi-directional rotation mill and dried under different conditions(liquid, temperature and drying). It shows that the samples cake seriously and th...Nano hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX) was prepared using a bi-directional rotation mill and dried under different conditions(liquid, temperature and drying). It shows that the samples cake seriously and the particles grow up obviously by ordinary drying in different liquids at 70 C, which occurs again after vacuum drying. With the increase of temperature, the degrees of caking and aggregation are enhanced.Well dispersed sample maintaining constant particle size is extracted by supercritical drying, especially freeze drying. Furthermore, the mechanical sensitivities of I-RDX, O-RDX and F-RDX, of which the average sizes are 88.03 mm, 15.32 mm and 0.16 mm, respectively, are evaluated. Compared with I-RDX, the friction, impact and shock sensitivities of O-RDX are slightly lower. However, the friction, impact and shock sensitivities of F-RDX are reduced by 30%, 99.0% and 59.9%, respectively.展开更多
The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined forthe sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrat...The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined forthe sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management.Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with thefloating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing resultsindicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%,respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl.All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated inTianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg mL-1 andtheir resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorphhas been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivitiesof the pathogen were nearly normally distributed. Hence, their mean EC50 value [cymoxanil (0.1647 ± 0.0255) μg mL-1,dimethomorph (0.0970 ± 0.0052) μg mL-1] could be used as the baseline sensitivities for monitoring the field resistancedevelopment. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalentresults. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to theresistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should bereduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.展开更多
The etiological agent of severe acute respiratory syndrome(SARS) was identified as a new coronavirus,termed SARS-CoV. Establishment of an efficient and sensitive diagnostic system of SARS-CoV genetic materials is cruc...The etiological agent of severe acute respiratory syndrome(SARS) was identified as a new coronavirus,termed SARS-CoV. Establishment of an efficient and sensitive diagnostic system of SARS-CoV genetic materials is crucial for SARS control. In this study,we quantified SARS-CoV mRNAs in both infected cell culture lysate and in supernatant by using Real-time quantitative revere transcription-PCR based on EvaGreenTM dye and Taqman-MGB probes. For extensive evaluation of sensitivities and specificities,13 pairs of primers and 4 probes were designed based on different genes of SARS-CoV. Glyceraldehydes-3-phosphate dehydrogenase(GAPDH) was selected as the internal control gene. Results showed that S-gene-specific PCR was the most sensitive for detection,but because of its sequence variability in the different viral strains,primers and a probe based on the N gene were suitable substitutions. Meanwhile,we found the mRNA concentrations in cell culture lysates were much higher than in cell supernatant and facilited more sensitive detection of the SARS-CoV.展开更多
In ballistic penetration,a main failure mode for a projectile is adiabatic shear localization which results in macro cracks developing along ASBs which lead to the fracture of projectile.In this paper,the adiabatic sh...In ballistic penetration,a main failure mode for a projectile is adiabatic shear localization which results in macro cracks developing along ASBs which lead to the fracture of projectile.In this paper,the adiabatic shear sensitivity and ballistic performances of two high strength steels,30CrMnSi and 35CrWMo,with similar static mechanical properties were investigated.Split Hopkinson Pressure Bar(SHPB)for compression loading and ballistic experiments above the velocity of 1 000 m/s against thick concrete targets were performed.The SHPB and ballistic experimental results showed that the 30CrMnSi steel exhibits more adiabatic shear sensitivity,compared with the 35CrWMo steel.Even though these two steels have similar static mechanical properties,the 35CrWMo steel projectile exhibits better penetration performance than the 30CrMnSi projectile due to different adiabatic shear sensitivities.展开更多
α-Fe2O3 nanoparticles doped with various molar fractions of Cr3+ were synthesized by a forced hydrolysis route and were characterized by X-ray diffraction(XRD),scanning electronic microscopy(SEM),X-ray photoelectron ...α-Fe2O3 nanoparticles doped with various molar fractions of Cr3+ were synthesized by a forced hydrolysis route and were characterized by X-ray diffraction(XRD),scanning electronic microscopy(SEM),X-ray photoelectron spectroscopy(XPS) and inductive coupled plasma(ICP) techniques.The particles reserve shuttle-like shape in the presence of Cr3+.The crystallite sizes of Fe2O3 become smaller with the increased Cr3+ concentration in solution.The responses of Cr doped α-Fe2O3 sensors were studied towards reducing gases such as ethanol,methanol,acetone,gasoline and n-hexane.Gas sensors based on these materials have higher sensitivities and rapid response/recovery time to alcohol than to hydrocarbon.展开更多
文摘This work presents the results of the exact computation of (180)<sup>3</sup> = 5,832,000 third-order mixed sensitivities of the leakage response of a polyethylene-reflected plutonium (PERP) experimental benchmark with respect to the benchmark’s 180 microscopic total cross sections. This computation was made possible by applying the Third-Order Adjoint Sensitivity Analysis Methodology developed by Cacuci. The numerical results obtained in this work revealed that many of the 3<sup>rd</sup>-order sensitivities are significantly larger than their corresponding 1<sup>st</sup>- and 2<sup>nd</sup>-order ones, which is contrary to the widely held belief that higher-order sensitivities are all much smaller and hence less important than the first-order ones, for reactor physics systems. In particular, the largest 3<sup>rd</sup>-order relative sensitivity is the mixed sensitivity <img src="Edit_754b8437-dfdf-487d-af68-c78c637e6d4e.png" width="180" height="24" alt="" />of the PERP leakage response with respect to the lowest energy-group (30) total cross sections of <sup>1</sup>H (“isotope 6”) and <sup>239</sup>Pu (“isotope 1”). These two isotopes are shown in this work to be the two most important parameters affecting the PERP benchmark’s leakage response. By comparison, the largest 1<sup>st</sup>-order sensitivity is that of the PERP leakage response with respect to the lowest energy-group total cross section of isotope <sup>1</sup>H, having the value <img src="Edit_a5cfcc11-6a99-41ee-b844-a5ee84b454b3.png" width="100" height="24" alt="" />, while the largest 2<sup>nd</sup>-order sensitivity is <img src="Edit_05166a2b-97f7-43f1-98ff-b21368c00228.png" width="120" height="22" alt="" />. The 3<sup>rd</sup>-order sensitivity analysis presented in this work is the first ever such analysis in the field of reactor physics. The consequences of the results presented in this work on the uncertainty analysis of the PERP benchmark’s leakage response will be presented in a subsequent work.
文摘This work presents the “Second-Order Comprehensive Adjoint Sensitivity Analysis Methodology (2<sup>nd</sup>-CASAM)” for the efficient and exact computation of 1<sup>st</sup>- and 2<sup>nd</sup>-order response sensitivities to uncertain parameters and domain boundaries of linear systems. The model’s response (<em>i.e.</em>, model result of interest) is a generic nonlinear function of the model’s forward and adjoint state functions, and also depends on the imprecisely known boundaries and model parameters. In the practically important particular case when the response is a scalar-valued functional of the forward and adjoint state functions characterizing a model comprising N parameters, the 2<sup>nd</sup>-CASAM requires a single large-scale computation using the First-Level Adjoint Sensitivity System (1<sup>st</sup>-LASS) for obtaining all of the first-order response sensitivities, and at most N large-scale computations using the Second-Level Adjoint Sensitivity System (2<sup>nd</sup>-LASS) for obtaining exactly all of the second-order response sensitivities. In contradistinction, forward other methods would require (<em>N</em>2/2 + 3 <em>N</em>/2) large-scale computations for obtaining all of the first- and second-order sensitivities. This work also shows that constructing and solving the 2<sup>nd</sup>-LASS requires very little additional effort beyond the construction of the 1<sup>st</sup>-LASS needed for computing the first-order sensitivities. Solving the equations underlying the 1<sup>st</sup>-LASS and 2<sup>nd</sup>-LASS requires the same computational solvers as needed for solving (<em>i.e.</em>, “inverting”) either the forward or the adjoint linear operators underlying the initial model. Therefore, the same computer software and “solvers” used for solving the original system of equations can also be used for solving the 1<sup>st</sup>-LASS and the 2<sup>nd</sup>-LASS. Since neither the 1<sup>st</sup>-LASS nor the 2<sup>nd</sup>-LASS involves any differentials of the operators underlying the original system, the 1<sup>st</sup>-LASS is designated as a “<u>first-level</u>” (as opposed to a “first-order”) adjoint sensitivity system, while the 2<sup>nd</sup>-LASS is designated as a “<u>second-level</u>” (rather than a “second-order”) adjoint sensitivity system. Mixed second-order response sensitivities involving boundary parameters may arise from all source terms of the 2<sup>nd</sup>-LASS that involve the imprecisely known boundary parameters. Notably, the 2<sup>nd</sup>-LASS encompasses an automatic, inherent, and independent “solution verification” mechanism of the correctness and accuracy of the 2nd-level adjoint functions needed for the efficient and exact computation of the second-order sensitivities.
基金supported by the Chinese Academy of Sciences(KJZD-EW-G03-04)the National Natural Science Foundation of China(41721091,41671071)Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(No.2017490711)
文摘Due to global warming, glaciers on the Tibetan Plateau(TP) are experiencing widespread shrinkage; however, the mechanisms controlling glacier variations across the TP are still rather unclear, especially on the northeastern TP. In this study, a physically based, distributed surface-energy and mass-balance model was used to simulate glacier mass balance forced by meteorological data. The model was applied to Laohugou No. 12 Glacier, western Qilian Mountains, China, during2010~2012. The simulated albedo and mass balance were validated and calibrated by in situ measurements. The simulated annual glacier-wide mass balances were-385 mm water equivalent(w.e.) in 2010/2011 and-232 mm w.e. in 2011/2012,respectively. The mean equilibrium-line altitude(ELA) was 5,015 m a.s.l., during 2010~2012, which ascended by 215 m compared to that in the 1970 s. The mean accumulation area ratio(AAR) was 39% during the two years. Climatic-sensitivity experiments indicated that the change of glacier mass balance resulting from a 1.5 °C increase in air temperature could be offset by a 30% increase in annual precipitation. The glacier mass balance varied linearly with precipitation, at a rate of130 mm w.e. per 10% change in total precipitation.
文摘The accurate diagnosis of tuberculosis caused by members of the Mycobacterium tuberculosis complex (MTBC) has remained a major challenge in clinical laboratories world-wide. Several studies have evaluated the use of highly specific in-house PCR assays targeting the IS6110, hupB, rpoB, oxyR, and IS1081 genes in the detection of MTBC species with reports on variable sensitivities depending on the geographical sourcing of isolates. In the present investigations, we evaluated the sensitivities of these PCR assays on 125 MTBC cultured isolates from five (West, Centre, Littoral, North West and South West) of the ten regions of Cameroon. Of this number, 124 (99.2%), 117 (93.6%), 123 (99.1%), 119 (95.2%) and 118 (94.4%) were positive by the IS6110, hupB, rpoB, oxyR, and IS1081-based PCR assays respectively. A total of 110 (88%) of the cultured isolates were also identified as MTBC by standard biochemical tests. Of this number, 109 (99.1%), 104 (94.5%), 109 (99.1%), 106 (96.4%) and 104 (94.5%) were positive in the IS6110, hupB, rpoB, oxyR, and IS1081-based PCR assays respectively. Concordant PCR results were obtained for 108 of the 125 samples. The 15 isolates that were negative biochemically scored sensitivities ranging from 100% (for the IS6110 assay) to 86.7% (for the hupB and oxyR assay). The combination of the IS6110 assay, which turned out to be the most sensitive, and each of the other assays gave 100% sensitivity. We conclude that the combined targeting of the IS6110 and rpoB genes is likely to yield the most sensitive PCR procedure for the diagnosis of MTBC infection in the five regions of Cameroon.
基金sponsored by the Alpha Foundation for the Improvement of Mine Safety and Health, Inc. (Alpha Foundation)the funding provided for this project by the Alpha Foundationpartially funded by the National Institute of Occupational Health and Science (NIOSH) under Grant Number 200-2016-90154.
文摘Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.
文摘Relative sensitivities of 30 species of common woody plants to simulated acid rain with pH values of 2.0, 2.5, 3.0, 3.5, 4.5 and control were studied. The results showed that 6 species of these plants were sensitive to simulated acid rain. The moderate included 18 species. The resistant included 6. Relative sensitivities to ambient acid rain and air pollutants and visible injury degree of 30 species of common woody plants in Chongqing City were investigated. Results showed that 6 species with foliage lesion rate at above 10 percent were sensitive, that 6 species with no lesion were resistant and that other 18 species with lesion at 10 percent below were moderate. Other 7 cities (Guiyang, Zunyi, Duyun, Changsha, Zhuzhou, Liuzhou and Guilin City) were also investigated and results were consistent with those of Chongqing City. The experimental and investigated results showed relative sensitivities and visible injury degree of woody plants to simulated acid rain were consistent with those of the woody
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41127002,11574099,41504034,and 11474115)the National Basic Research Program of China(Grant No.2010CB832806)
文摘We investigated the sensitivities of atom interferometers in the usual fringe-scanning method(FSM) versus the fringelocking method(FLM). The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.
文摘This work extends to fourth-order previously published work on developing the adjoint sensitivity and uncertainty analysis of the numerical model of a <u>p</u>oly<u>e</u>thylene-<u>r</u>eflected <u>p</u>lutonium (acronym: PERP) OECD/NEA reactor physics benchmark. Previous works showed that the third-order sensitivities of the PERP leakage response with respect to these total microscopic cross sections are far larger than the corresponding 1<sup>st</sup>-order and 2<sup>nd</sup>-order ones, thereby having the largest impact on the uncertainties induced in the PERP benchmark’s response. This finding has motivated the development of the original 4<sup>th</sup>-order formulas presented in this work, which are valid not only for the PERP benchmark but can also be used for computing the 4<sup>th</sup>-order sensitivities of response of any nuclear system involving fissionable material and internal or external neutron sources. Subsequent works will use the adjoint-based mathematical expressions obtained in this work to compute exactly and efficiently the numerical values of the largest fourth-order sensitivities of the PERP benchmark’s response to the total microscopic cross sections, and use them for a pioneering fourth-order uncertainty analysis of the PERP benchmark’s response.
基金The China Major Scientific and Technological Programs(2009ZX04011-053)the China NSFC Fund(50975047)
文摘The dynamic transmission characteristics and the sensitivities of the three stage idler gear system of the new NC power turret are studied in the paper. Considering the strongly nonlinear factors such as the periodically time-varying mesh stiffness, the nonlinear tooth backlash, the lump-parameter model of the gear system is developed with one rotational and two translational freedoms of each gear. The eigen-values and eigenvectors are derived and analyzed on the basis of the real modal theory. The sensitivities of natural frequencies to design parameters including supporting and meshing stiffnesses, gear masses, and moments of inertia by the direct differential method are also calculated. The results show the quantitative and qualitative impact of the parameters to the natural characteristics of the gear system. Furthermore, the periodic steady state solutions are obtained by the numerical approach based on the nonlinear model. These results are employed to gain insights into the primary controlling parameters, to forecast the severity of the dynamic response, and to assess the acceptability of the gear design.
文摘In this paper, structural static design is considered as a kind of inverse algebraiceigenvalue problem. It is the most important task for for the inverse problem to compute thesensitivities of eigenvalues and eigenvectors. Therefore. a complete set of higher ordersensitivity expressions has been presented based on the complex variables theory. Theseexpressions have solid mathematical foundation and practical significance.
文摘The spark energy, E ES , required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the E ES values and impact sensitivity, expressed as drop energies E d of the "first reaction", were established and discussed. The conclusion is made that depending on intermolecular interaction factors in crystals of energetic materials, the mechanism of impact energy transition to the reaction centre of their molecule can be differ from that of transition of energy of electric spark.
文摘Cellular environments are in essence stochastic, owing to the random character of the biochemical reaction events in a single cell. Stochastic fluctuations may substantially contribute to the dynamics of systems with small copy numbers of some biochemical species. Then, stochastic models are indispensable for properly portraying the behaviour of the system. Sensitivity analysis is one of the central tools for studying stochastic models of cellular dynamics. Here, we propose some finite-difference strategies for estimating parametric sensitivities of higher-order moments of the system state for stochastic discrete biochemical kinetic models. To reduce the variance of the sensitivity estimator, we employ various coupling techniques. The advantages of the proposed methods are illustrated in several models of biochemical systems of practical relevance.
文摘Nano hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX) was prepared using a bi-directional rotation mill and dried under different conditions(liquid, temperature and drying). It shows that the samples cake seriously and the particles grow up obviously by ordinary drying in different liquids at 70 C, which occurs again after vacuum drying. With the increase of temperature, the degrees of caking and aggregation are enhanced.Well dispersed sample maintaining constant particle size is extracted by supercritical drying, especially freeze drying. Furthermore, the mechanical sensitivities of I-RDX, O-RDX and F-RDX, of which the average sizes are 88.03 mm, 15.32 mm and 0.16 mm, respectively, are evaluated. Compared with I-RDX, the friction, impact and shock sensitivities of O-RDX are slightly lower. However, the friction, impact and shock sensitivities of F-RDX are reduced by 30%, 99.0% and 59.9%, respectively.
文摘The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined forthe sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management.Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with thefloating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing resultsindicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%,respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl.All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated inTianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg mL-1 andtheir resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorphhas been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivitiesof the pathogen were nearly normally distributed. Hence, their mean EC50 value [cymoxanil (0.1647 ± 0.0255) μg mL-1,dimethomorph (0.0970 ± 0.0052) μg mL-1] could be used as the baseline sensitivities for monitoring the field resistancedevelopment. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalentresults. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to theresistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should bereduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.
基金The Knowledge Innovation Program of Chinese Academy of Sciences (KSCX2-YW-N-065)FP6 projects DISSECT (N°SP22-CT-2004-511060)EPIS-ARS (N°SP22-CT-2004-511603)
文摘The etiological agent of severe acute respiratory syndrome(SARS) was identified as a new coronavirus,termed SARS-CoV. Establishment of an efficient and sensitive diagnostic system of SARS-CoV genetic materials is crucial for SARS control. In this study,we quantified SARS-CoV mRNAs in both infected cell culture lysate and in supernatant by using Real-time quantitative revere transcription-PCR based on EvaGreenTM dye and Taqman-MGB probes. For extensive evaluation of sensitivities and specificities,13 pairs of primers and 4 probes were designed based on different genes of SARS-CoV. Glyceraldehydes-3-phosphate dehydrogenase(GAPDH) was selected as the internal control gene. Results showed that S-gene-specific PCR was the most sensitive for detection,but because of its sequence variability in the different viral strains,primers and a probe based on the N gene were suitable substitutions. Meanwhile,we found the mRNA concentrations in cell culture lysates were much higher than in cell supernatant and facilited more sensitive detection of the SARS-CoV.
文摘In ballistic penetration,a main failure mode for a projectile is adiabatic shear localization which results in macro cracks developing along ASBs which lead to the fracture of projectile.In this paper,the adiabatic shear sensitivity and ballistic performances of two high strength steels,30CrMnSi and 35CrWMo,with similar static mechanical properties were investigated.Split Hopkinson Pressure Bar(SHPB)for compression loading and ballistic experiments above the velocity of 1 000 m/s against thick concrete targets were performed.The SHPB and ballistic experimental results showed that the 30CrMnSi steel exhibits more adiabatic shear sensitivity,compared with the 35CrWMo steel.Even though these two steels have similar static mechanical properties,the 35CrWMo steel projectile exhibits better penetration performance than the 30CrMnSi projectile due to different adiabatic shear sensitivities.
基金Supported by the National Natural Science Foundation of China(No.40772026)
文摘α-Fe2O3 nanoparticles doped with various molar fractions of Cr3+ were synthesized by a forced hydrolysis route and were characterized by X-ray diffraction(XRD),scanning electronic microscopy(SEM),X-ray photoelectron spectroscopy(XPS) and inductive coupled plasma(ICP) techniques.The particles reserve shuttle-like shape in the presence of Cr3+.The crystallite sizes of Fe2O3 become smaller with the increased Cr3+ concentration in solution.The responses of Cr doped α-Fe2O3 sensors were studied towards reducing gases such as ethanol,methanol,acetone,gasoline and n-hexane.Gas sensors based on these materials have higher sensitivities and rapid response/recovery time to alcohol than to hydrocarbon.
基金Supported by the National Natural Science Foundation of China （51274013） the International Cooperation Projects of Anhui, China （10080703026） Acknowledgements We thank the work group of soil information systems and solute transport models from Osnabrueck University of Applied Sciences, Germany for providing us their experimental work.
