To investigate the cost-effectiveness of different maintenance treatments of highways in Jiangsu Province, the historical pavement maintenance records, traffic load information and pavement performance data in the pav...To investigate the cost-effectiveness of different maintenance treatments of highways in Jiangsu Province, the historical pavement maintenance records, traffic load information and pavement performance data in the pavement management system (PMS) are recorded and analyzed. Compared with the growth model, the linear model, the logarithm model and the exponential model, the cubic model has higher regression accuracy R2 and it can capture the sigmoid shape of the deterioration curve. So it is selected to simulate the pavement rotting development. The benefit over cost ratio is calculated to quantify the treatment cost- effectiveness. The analysis results show that thin hot mix asphalt (HMA) overlays and micro surfacing are more cost- effective than the. other two treatments on light and moderate traffic roads. Hot in-place recycling and thick HMA overlays have much longer service lives and greater cost-effectiveness under heavy or extra heavy traffic.展开更多
A new feature based on higher order statistics is proposed for classification of MPSKsignals, which is invariant with respect to translation (shift), scale and rotation transforms of MPSK signal constellations, and ca...A new feature based on higher order statistics is proposed for classification of MPSKsignals, which is invariant with respect to translation (shift), scale and rotation transforms of MPSK signal constellations, and can suppress additive color or white Gaussian noise. Application of the new feature to classification of MPSK signals, at medium signal-to-noise ratio with specified sample size, results in high probability of correct identification. Finally, computer simulations and comparisons with existing algorithms are given.展开更多
The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailab...The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.展开更多
The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Diptero- carpus forest in Manipur, Northeast India. Two forest stands (stand Ⅰ and Ⅱ) were earm...The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Diptero- carpus forest in Manipur, Northeast India. Two forest stands (stand Ⅰ and Ⅱ) were earmarked randomly in the study site for the evaluation of biomass in the different girth classes of tree species by harvest method. The total biomass was 22.50 t.ha^-1 and 18.27 t.ha^-1 in forest stand I and II respectively. Annual aboveground net primary production varied from 8.86 to 10.43 t.ha^-1 respectively in two forest stands (stand Ⅰ and Ⅱ). In the present study, the values of production efficiency and the biomass accumulation ratio indicate that the forest is at succession stage with high productive potential.展开更多
We presented a novel framework for automatic behavior clustering and unsupervised anomaly detection in a large video set. The framework consisted of the following key components: 1 ) Drawing from natural language pr...We presented a novel framework for automatic behavior clustering and unsupervised anomaly detection in a large video set. The framework consisted of the following key components: 1 ) Drawing from natural language processing, we introduced a compact and effective behavior representation method as a stochastic sequence of spatiotemporal events, where we analyzed the global structural information of behaviors using their local action statistics. 2) The natural grouping of behavior patterns was discovered through a novel clustering algorithm. 3 ) A run-time accumulative anomaly measure was introduced to detect abnormal behavior, whereas normal behavior patterns were recognized when sufficient visual evidence had become available based on an online Likelihood Ratio Test (LRT) method. This ensured robust and reliable anomaly detection and normal behavior recognition at the shortest possible time. Experimental results demonstrated the effectiveness and robustness of our approach using noisy and sparse data sets collected from a real surveillance scenario.展开更多
A computationally efficient method for jointly estimating both Directions Of Arrival (DOA) and ranges of near field sources is presented. The proposed algorithm does not need any spectral peak searching and the 2-D pa...A computationally efficient method for jointly estimating both Directions Of Arrival (DOA) and ranges of near field sources is presented. The proposed algorithm does not need any spectral peak searching and the 2-D parameters are automatically paired. It is suitable for arbitrary additive Gaussian noise environment. Furthermore, its performances are confirmed by computer simulations.展开更多
High acceleration of radar targets is analyzed using Acceleration Ambiguity Function (AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are deriva...High acceleration of radar targets is analyzed using Acceleration Ambiguity Function (AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar.展开更多
The experimental orchard on calcareous soils in the Tikves region has been established in 1999, in order to investigate the influence of the rootstocks on the behaviour of the peach trees. In the experiment we evaluat...The experimental orchard on calcareous soils in the Tikves region has been established in 1999, in order to investigate the influence of the rootstocks on the behaviour of the peach trees. In the experiment we evaluated next rootstocks: Nemaguard (Prunus persica × Prunus davidiana), seedlings of GF 677 (Prunus persica ×Prunus amygdalus), hybrids BMVA 1, BMVA 2, VAF 215 and Autochthones type and GF 677 (Prunus persica × Prunus amygdalus) clonal. As control rootstocks in our experiment was used seedlings from vineyard peach (Prunus persica). The experiment was established with one year old trees from Redhaven variety. Agronomical characteristics (vegetative growth, occurrence of leaf chlorosis, tree mortality, yield, productivity and fruit quality) of the trees on different rootstocks have been measured over a twelve-year period (1999-2010). Significant differences on the level of P 〈 0.05 have been observed on vigour of the trees. The most vigorous trees were those on GF 677 clonal, GF 677 seedling and BMVA 2. The trees on Vineyard peach and Nemaguard was the weakest ones. The highest cumulative yield was recorded on GF-677 clonal rootstock, and the lowest on Nemaguard. Occurrence of chlorosis was the highest at Vineyard peach, Nemaguard and Autochthones hybrid, GF 677 clonal was the only rootstock without iron chlorosis. The percent of tree mortality to twelfth year was the highest at Autochthones hybrid (33.3), and at GF 677 clonal and BMVA 1 had not tree mortality.展开更多
Research indicates that high levels of sedentary behavior(sitting or lying with low energy expenditure) are adversely associated with health. A key factor in improving our understanding of the impact of sedentary beha...Research indicates that high levels of sedentary behavior(sitting or lying with low energy expenditure) are adversely associated with health. A key factor in improving our understanding of the impact of sedentary behavior(and patterns of sedentary time accumulation) on health is the use of objective measurement tools that collect date and time-stamped activity information. One such tool is the activP AL monitor. This thigh-worn device uses accelerometer-derived information about thigh position to determine the start and end of each period spent sitting/lying, standing, and stepping, as well as stepping speed, step counts, and postural transitions. The activP AL is increasingly being used within field-based research for its ability to measure sitting/lying via posture. We summarise key issues to consider when using the activP AL in physical activity and sedentary behavior field-based research with adult populations. It is intended that the findings and discussion points be informative for researchers who are currently using activP AL monitors or are intending to use them. Pre-data collection decisions, monitor preparation and distribution, data collection considerations, and manual and automated data processing possibilities are presented using examples from current literature and experiences from 2 research groups from the UK and Australia.展开更多
Daily precipitation analyses for 659 Chinese meteorological stations from 1951 to 2010 show that the rapid urbanization may have triggered the significant increase of heavy rainfall in China. During the last decades, ...Daily precipitation analyses for 659 Chinese meteorological stations from 1951 to 2010 show that the rapid urbanization may have triggered the significant increase of heavy rainfall in China. During the last decades, HRAs (Heavy Rainfall Amounts), HRDs (Heavy Rainfall Days) and HRI (Heavy Rainfall Intensity) in China have increased. Impressively, the upward trends are not randomly observed among stations, but of robust consistency with quite large regional scale over large widely and significantly. Compared to the 1950s, the HRA, HRD, and HRI increased by 68.71%, 60.15% and 11.52% during the 2000s. The significant increase of accumulative heavy rainfall appears firstly in the southeastern coasts in the early period, and then gradually expands to the central, southwest, north and northeast China. Rapid urbanization is very likely the main cause of large-scale heavy rainfall increase in China. The urbanization indicators including the industrial production output (GDP2), UP (Urban Population) and annual average HDs (Haze Days) are in good agreement with the heavy rainfall variations, and these indicators can statistically explain the variance of HRA, HRD and HRI by 61.54%, 58.48% and 65.54%, respectively. Meanwhile, the explained variance by leading climate indices including WPSH (Western Pacific Subtropical High), ENSO (El Nino-Southern Oscillation), AMO (Atlantic Multi-decadal Oscillation) and AAO (Antarctic Oscillation) are respectively 24.30%, 26.23% and 21.92%, being only about 1/3 of the urbanization-related variance. Panel data analysis of county-level total population and annual average visibility days less than 10 km also show that these two indicators have significant correlation with decadal HRA, HRD & HRI and the spatial correlation coefficient increases gradually with time. These consistent temporal and spatial features strongly suggest that rapid urbanization most likely triggered the steady increase of heavy rainfall over China during the recent decades.展开更多
Banking institutions all over the world face significant challenge due to the cumulative loss due to defaults of borrowers of different types of loans. The cumulative default loss built up over a period of time could ...Banking institutions all over the world face significant challenge due to the cumulative loss due to defaults of borrowers of different types of loans. The cumulative default loss built up over a period of time could wipe out the capital cushion of the banks. The aim of this paper is to help the banks to forecast the cumulative loss and its volatility. Defaulting amounts are random and defaults occur at random instants of time. A non Markovian time dependent random point process is used to model the cumulative loss. The expected loss and volatility are evaluated analytically. They are functions of probability of default, probability of loss amount, recovery rate and time. Probability of default being the important contributor is evaluated using Hidden Markov modeling. Numerical results obtained validate the model.展开更多
This paper presents a nonlinear approach to estimate the consumed energy in electric power distribution feeders. The proposed method uses the statistical solution algorithm to analyze the active energy monthly consump...This paper presents a nonlinear approach to estimate the consumed energy in electric power distribution feeders. The proposed method uses the statistical solution algorithm to analyze the active energy monthly consumption, which enables one to estimate the energy consumption during any period of the year. The energy readings and the normalized accumulated energy profile are used to estimate the hourly consumed active power, which can be used for future planning and sizing the equipment of the electrical system. The effectiveness of the proposed method is demonstrated by comparing the simulated results with that of real measured data.展开更多
This paper studies the effect of different environmental factors, including the axle load weight, environmental temperature, vehicle speed, and the aging level of asphalt, on the fatigue performance of asphalt mixes b...This paper studies the effect of different environmental factors, including the axle load weight, environmental temperature, vehicle speed, and the aging level of asphalt, on the fatigue performance of asphalt mixes based on four-point bending beam fatigue tests. A fractional factorial design method named "uniform design" was applied in experimental design. The relations of the environmental factors to initial stiffness, fatigue life, phase angle and cumulative dissipated energy were established with the general linear modeling method. It is found that there exists very good correlativity between the environmental factors and the fatigue performance indices of asphalt mixes. The coefficients of total correlation are mainly beyond 0. 95. The results indicate that the consideration of the effect of environmental factors is necessary in the fatigue performance evaluation on real asphalt pavement.展开更多
This paper presents a brief analysis of the frequency and cumulative distributions of Americans' annual household income. In addition, a thorough discussion of the correlations between average income and some key dem...This paper presents a brief analysis of the frequency and cumulative distributions of Americans' annual household income. In addition, a thorough discussion of the correlations between average income and some key demographic variables are included. The data come from the 2004 Survey of Consumer Finances. Utilizing the Survey a new, extraordinarily close, power law, relationship between current annual household income and accumulated financial assets is demonstrated. Another startling result is that the dependence of mean annual income on portfolio composition has nearly perfect power law dependence too. As money has scale, and power laws do not, this makes no sense.展开更多
Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. ...Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function (PDF) of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a (a in (0,1]). To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio (BER), the Complementary Cumulative Distribution Function (CCDF) of Peak to Average Power Ratio (PAPR), and other analytical studies which adopt the PDF.展开更多
This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitori...This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as increasing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pillar strength using most common empirical techniques such as those proposed by Bieniawski and Salamon. While using lower pillar strength estimates may be considered conservative,it underestimates the actual capacity of pillars in accumulating much higher stress and strain energies,misleading the designer and inadvertently diminishing mine safety. The role of induced horizontal stress in mine pillars and surrounding strata is emphasized in coal pillar mechanics of violent failure. The triggering mechanism for the violent events is sudden loss of pillar confinement due to dynamic loading resulting from failure of overlying stiff and strong strata. Evidence of such mechanism is noted in the field by observed red-dust at the coal-rock interfaces at the location of coal bumps and irregular, periodic caving in room-and-pillar mines quantified through direct pressure measurements in the gob.展开更多
基金The Science and Technology Project of Jiangsu Provincial Communications Department(No.7621000078)
文摘To investigate the cost-effectiveness of different maintenance treatments of highways in Jiangsu Province, the historical pavement maintenance records, traffic load information and pavement performance data in the pavement management system (PMS) are recorded and analyzed. Compared with the growth model, the linear model, the logarithm model and the exponential model, the cubic model has higher regression accuracy R2 and it can capture the sigmoid shape of the deterioration curve. So it is selected to simulate the pavement rotting development. The benefit over cost ratio is calculated to quantify the treatment cost- effectiveness. The analysis results show that thin hot mix asphalt (HMA) overlays and micro surfacing are more cost- effective than the. other two treatments on light and moderate traffic roads. Hot in-place recycling and thick HMA overlays have much longer service lives and greater cost-effectiveness under heavy or extra heavy traffic.
文摘A new feature based on higher order statistics is proposed for classification of MPSKsignals, which is invariant with respect to translation (shift), scale and rotation transforms of MPSK signal constellations, and can suppress additive color or white Gaussian noise. Application of the new feature to classification of MPSK signals, at medium signal-to-noise ratio with specified sample size, results in high probability of correct identification. Finally, computer simulations and comparisons with existing algorithms are given.
基金Project(2012CB725400)supported by the National Basic Research Program of ChinaProjects(71271023,71322102,7121001)supported by the National Natural Science Foundation of China
文摘The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.
文摘The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Diptero- carpus forest in Manipur, Northeast India. Two forest stands (stand Ⅰ and Ⅱ) were earmarked randomly in the study site for the evaluation of biomass in the different girth classes of tree species by harvest method. The total biomass was 22.50 t.ha^-1 and 18.27 t.ha^-1 in forest stand I and II respectively. Annual aboveground net primary production varied from 8.86 to 10.43 t.ha^-1 respectively in two forest stands (stand Ⅰ and Ⅱ). In the present study, the values of production efficiency and the biomass accumulation ratio indicate that the forest is at succession stage with high productive potential.
基金This work is supported by National Natural Science Foundation of China (NSFC) under Grant No. 60573139 andNational Science & Technology Pillar Program of China under Grant NO. 2008BAH221303.
文摘We presented a novel framework for automatic behavior clustering and unsupervised anomaly detection in a large video set. The framework consisted of the following key components: 1 ) Drawing from natural language processing, we introduced a compact and effective behavior representation method as a stochastic sequence of spatiotemporal events, where we analyzed the global structural information of behaviors using their local action statistics. 2) The natural grouping of behavior patterns was discovered through a novel clustering algorithm. 3 ) A run-time accumulative anomaly measure was introduced to detect abnormal behavior, whereas normal behavior patterns were recognized when sufficient visual evidence had become available based on an online Likelihood Ratio Test (LRT) method. This ensured robust and reliable anomaly detection and normal behavior recognition at the shortest possible time. Experimental results demonstrated the effectiveness and robustness of our approach using noisy and sparse data sets collected from a real surveillance scenario.
基金Supported in part by Trans-Century Trainning Programme Foundation for the Talents by the State Education Commission and the National Natural Science Foundation of China (No.60172028)
文摘A computationally efficient method for jointly estimating both Directions Of Arrival (DOA) and ranges of near field sources is presented. The proposed algorithm does not need any spectral peak searching and the 2-D parameters are automatically paired. It is suitable for arbitrary additive Gaussian noise environment. Furthermore, its performances are confirmed by computer simulations.
文摘High acceleration of radar targets is analyzed using Acceleration Ambiguity Function (AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar.
文摘The experimental orchard on calcareous soils in the Tikves region has been established in 1999, in order to investigate the influence of the rootstocks on the behaviour of the peach trees. In the experiment we evaluated next rootstocks: Nemaguard (Prunus persica × Prunus davidiana), seedlings of GF 677 (Prunus persica ×Prunus amygdalus), hybrids BMVA 1, BMVA 2, VAF 215 and Autochthones type and GF 677 (Prunus persica × Prunus amygdalus) clonal. As control rootstocks in our experiment was used seedlings from vineyard peach (Prunus persica). The experiment was established with one year old trees from Redhaven variety. Agronomical characteristics (vegetative growth, occurrence of leaf chlorosis, tree mortality, yield, productivity and fruit quality) of the trees on different rootstocks have been measured over a twelve-year period (1999-2010). Significant differences on the level of P 〈 0.05 have been observed on vigour of the trees. The most vigorous trees were those on GF 677 clonal, GF 677 seedling and BMVA 2. The trees on Vineyard peach and Nemaguard was the weakest ones. The highest cumulative yield was recorded on GF-677 clonal rootstock, and the lowest on Nemaguard. Occurrence of chlorosis was the highest at Vineyard peach, Nemaguard and Autochthones hybrid, GF 677 clonal was the only rootstock without iron chlorosis. The percent of tree mortality to twelfth year was the highest at Autochthones hybrid (33.3), and at GF 677 clonal and BMVA 1 had not tree mortality.
基金supported by the National Institute for Health Researsch (NIHR) DietLifestyle & Physical Activity Biomedical Research Unit based at University Hospitals of Leicester and Loughborough University+5 种基金the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care-East Midlands (NIHR CLAHRC- EM)the Leicester Clinical Trials Unitsupported by a National Health and Medical Research Council (NHMRC) Centre for Research Excellence Grant on Sitting Time and Chronic Disease Prevention-Measurement, Mechanisms and Interventions (APP1057608)supported by a Heart Foundation Postdoctoral (PH 12B 7054)NHMRC Career Development (#1086029) Fellowshipsupported by an Australian Research Council Future Fellowship (FTE 100100918)
文摘Research indicates that high levels of sedentary behavior(sitting or lying with low energy expenditure) are adversely associated with health. A key factor in improving our understanding of the impact of sedentary behavior(and patterns of sedentary time accumulation) on health is the use of objective measurement tools that collect date and time-stamped activity information. One such tool is the activP AL monitor. This thigh-worn device uses accelerometer-derived information about thigh position to determine the start and end of each period spent sitting/lying, standing, and stepping, as well as stepping speed, step counts, and postural transitions. The activP AL is increasingly being used within field-based research for its ability to measure sitting/lying via posture. We summarise key issues to consider when using the activP AL in physical activity and sedentary behavior field-based research with adult populations. It is intended that the findings and discussion points be informative for researchers who are currently using activP AL monitors or are intending to use them. Pre-data collection decisions, monitor preparation and distribution, data collection considerations, and manual and automated data processing possibilities are presented using examples from current literature and experiences from 2 research groups from the UK and Australia.
文摘Daily precipitation analyses for 659 Chinese meteorological stations from 1951 to 2010 show that the rapid urbanization may have triggered the significant increase of heavy rainfall in China. During the last decades, HRAs (Heavy Rainfall Amounts), HRDs (Heavy Rainfall Days) and HRI (Heavy Rainfall Intensity) in China have increased. Impressively, the upward trends are not randomly observed among stations, but of robust consistency with quite large regional scale over large widely and significantly. Compared to the 1950s, the HRA, HRD, and HRI increased by 68.71%, 60.15% and 11.52% during the 2000s. The significant increase of accumulative heavy rainfall appears firstly in the southeastern coasts in the early period, and then gradually expands to the central, southwest, north and northeast China. Rapid urbanization is very likely the main cause of large-scale heavy rainfall increase in China. The urbanization indicators including the industrial production output (GDP2), UP (Urban Population) and annual average HDs (Haze Days) are in good agreement with the heavy rainfall variations, and these indicators can statistically explain the variance of HRA, HRD and HRI by 61.54%, 58.48% and 65.54%, respectively. Meanwhile, the explained variance by leading climate indices including WPSH (Western Pacific Subtropical High), ENSO (El Nino-Southern Oscillation), AMO (Atlantic Multi-decadal Oscillation) and AAO (Antarctic Oscillation) are respectively 24.30%, 26.23% and 21.92%, being only about 1/3 of the urbanization-related variance. Panel data analysis of county-level total population and annual average visibility days less than 10 km also show that these two indicators have significant correlation with decadal HRA, HRD & HRI and the spatial correlation coefficient increases gradually with time. These consistent temporal and spatial features strongly suggest that rapid urbanization most likely triggered the steady increase of heavy rainfall over China during the recent decades.
文摘Banking institutions all over the world face significant challenge due to the cumulative loss due to defaults of borrowers of different types of loans. The cumulative default loss built up over a period of time could wipe out the capital cushion of the banks. The aim of this paper is to help the banks to forecast the cumulative loss and its volatility. Defaulting amounts are random and defaults occur at random instants of time. A non Markovian time dependent random point process is used to model the cumulative loss. The expected loss and volatility are evaluated analytically. They are functions of probability of default, probability of loss amount, recovery rate and time. Probability of default being the important contributor is evaluated using Hidden Markov modeling. Numerical results obtained validate the model.
文摘This paper presents a nonlinear approach to estimate the consumed energy in electric power distribution feeders. The proposed method uses the statistical solution algorithm to analyze the active energy monthly consumption, which enables one to estimate the energy consumption during any period of the year. The energy readings and the normalized accumulated energy profile are used to estimate the hourly consumed active power, which can be used for future planning and sizing the equipment of the electrical system. The effectiveness of the proposed method is demonstrated by comparing the simulated results with that of real measured data.
文摘This paper studies the effect of different environmental factors, including the axle load weight, environmental temperature, vehicle speed, and the aging level of asphalt, on the fatigue performance of asphalt mixes based on four-point bending beam fatigue tests. A fractional factorial design method named "uniform design" was applied in experimental design. The relations of the environmental factors to initial stiffness, fatigue life, phase angle and cumulative dissipated energy were established with the general linear modeling method. It is found that there exists very good correlativity between the environmental factors and the fatigue performance indices of asphalt mixes. The coefficients of total correlation are mainly beyond 0. 95. The results indicate that the consideration of the effect of environmental factors is necessary in the fatigue performance evaluation on real asphalt pavement.
文摘This paper presents a brief analysis of the frequency and cumulative distributions of Americans' annual household income. In addition, a thorough discussion of the correlations between average income and some key demographic variables are included. The data come from the 2004 Survey of Consumer Finances. Utilizing the Survey a new, extraordinarily close, power law, relationship between current annual household income and accumulated financial assets is demonstrated. Another startling result is that the dependence of mean annual income on portfolio composition has nearly perfect power law dependence too. As money has scale, and power laws do not, this makes no sense.
基金supported by the National Natural Science Foundation General Program of China(No.61201146)the National Basic Research Program of China(2013CB329003)the Fundamental Research Funds for the Central Universities(HIT.NSRIF.2015022)
文摘Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function (PDF) of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a (a in (0,1]). To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio (BER), the Complementary Cumulative Distribution Function (CCDF) of Peak to Average Power Ratio (PAPR), and other analytical studies which adopt the PDF.
文摘This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as increasing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pillar strength using most common empirical techniques such as those proposed by Bieniawski and Salamon. While using lower pillar strength estimates may be considered conservative,it underestimates the actual capacity of pillars in accumulating much higher stress and strain energies,misleading the designer and inadvertently diminishing mine safety. The role of induced horizontal stress in mine pillars and surrounding strata is emphasized in coal pillar mechanics of violent failure. The triggering mechanism for the violent events is sudden loss of pillar confinement due to dynamic loading resulting from failure of overlying stiff and strong strata. Evidence of such mechanism is noted in the field by observed red-dust at the coal-rock interfaces at the location of coal bumps and irregular, periodic caving in room-and-pillar mines quantified through direct pressure measurements in the gob.