The dying-back hypothesis holds that the damage to neuromuscular junctions and distal axons in amyotrophic lateral sclerosis occurs at the earliest stage of the disease.Previous basic studies have confirmed early dama...The dying-back hypothesis holds that the damage to neuromuscular junctions and distal axons in amyotrophic lateral sclerosis occurs at the earliest stage of the disease.Previous basic studies have confirmed early damage to neuromuscular junctions,but it is difficult to obtain such evidence directly in clinical practice.In this prospective cross-sectional study,we recruited 22 patients with early amyotrophic lateral sclerosis with disease duration < 12 months and with clinical symptoms limited to the upper limbs.We also recruited 32 healthy controls.Repetitive nerve stimulation was performed,and patients were followed for 12 months.We found a significant change in the response to repetitive nerve stimulation in amyotrophic lateral sclerosis patients without spontaneous electromyographic activity.Patients that were prone to denervation had an increased decrement response of target muscles after repetitive nerve stimulation.These results suggest that changes in response to repetitive nerve stimulation may occur before denervation in amyotrophic lateral sclerosis patients.The damage to lower motor neurons is more obvious in patients with a higher percentage of repetitive never stimulation-related amplitude decrements.This study was approved by the Institutional Ethics Committee of Peking University Third Hospital(approval No.M2017198) on August 24,2017.展开更多
现代的大型复杂结构,如大坝、高层建筑、桥梁及海洋平台等,处于复杂的环境载荷作用下,这些环境载荷往往是无法测量的。在仅有输出响应时,应用随机减量法RDT获得自由衰减响应信号,而后用时域复指数拟合法、ITD法、特征系统实现算法ERA等...现代的大型复杂结构,如大坝、高层建筑、桥梁及海洋平台等,处于复杂的环境载荷作用下,这些环境载荷往往是无法测量的。在仅有输出响应时,应用随机减量法RDT获得自由衰减响应信号,而后用时域复指数拟合法、ITD法、特征系统实现算法ERA等算法获得结构的模态参数是一种有效的方法。但在数据量有限时,随机减量函数的平均次数过少,导致RD函数的收敛性较差。为此提出了利用Vector Random Decrement技术(VRDT)提取自由衰减响应信号,而后利用特征系统实现算法ERA求得模态参数的方法,新算法能够有效地提高模态参数识别精度。数值算例验证了所提算法的有效性。展开更多
Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–...Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy–Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy–Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.展开更多
Frequent item sets mining plays an important role in association rules mining. A variety of algorithms for finding frequent item sets in very large transaction databases have been developed. Although many techniques w...Frequent item sets mining plays an important role in association rules mining. A variety of algorithms for finding frequent item sets in very large transaction databases have been developed. Although many techniques were proposed for maintenance of the discovered rules when new transactions are added, little work is done for maintaining the discovered rules when some transactions are deleted from the database. Updates are fundamental aspect of data management. In this paper, a decremental association rules mining algorithm is present for updating the discovered association rules when some transactions are removed from the original data set. Extensive experiments were conducted to evaluate the performance of the proposed algorithm. The results show that the proposed algorithm is efficient and outperforms other well-known algorithms.展开更多
The observation of a left sided accessory pathway with decremental properties is rare. We describe the behaviour of one of these pathways which was characterized by the presence of retrograde conduction (not previousl...The observation of a left sided accessory pathway with decremental properties is rare. We describe the behaviour of one of these pathways which was characterized by the presence of retrograde conduction (not previously reported) and thus inducibility of atrio-ventricular orthodromic reentrant tachycardia.展开更多
We compile the observed intensity ratios of the Balmer lines for low redshift quasars and Seyfert Ⅰ galaxies. In the framework of the Cerenkov line emission theory, we compare the theoretical intensity ratios with th...We compile the observed intensity ratios of the Balmer lines for low redshift quasars and Seyfert Ⅰ galaxies. In the framework of the Cerenkov line emission theory, we compare the theoretical intensity ratios with those of observations, and find that the observed intensity ratios for the radio-loud quasars and the Seyfert Ⅰ galaxies are nearer to the theoretical expectation than those for the radio-quiet sources. It seems that for the radio-loud AGNs, the characteristics of the Cerenkov line emission are more remarkable because of the existence of a great number of relativistic electrons. We also discuss the reddening by dust in quasars and the Seyfert galaxies. The fact that the reddening of the Seyfert galaxies is more serious than quasars shows that the Seyfert galaxies have more dust than quasars. This is in agreement with the present point of view.展开更多
The random decrement technique （RDT）, introduced in the sixties by Cole [NASA CR- 2005, 1973], is a very performing method of analysis for vibration signature of a structure under ambient loading. But the real natur...The random decrement technique （RDT）, introduced in the sixties by Cole [NASA CR- 2005, 1973], is a very performing method of analysis for vibration signature of a structure under ambient loading. But the real nature of the random decrement signature has been misunderstood until now. Moreover, the various interpretations were made in continuous time setting, while real experimental data are obtained in discrete time. In this paper, the really implemental discrete time algorithms are studied. The asymptotic analysis as the number of triggering points go to infinity is achieved, and a Law of Large Numbers as well as a Central Limit Theorem is proved. Moreover, the limit as the discretization time step goes to zero is computed, giving more tractable formulas to approximate the random decrement. This is a new approach of the famous ＂Kac-Slepian paradox＂ [Ann. Math. Star., 30, 1215-1228 （1959）]. The main point might be that the RDT is a very efficient functional estimator of the correlation function of a stationary ergodic Gaussian process. Very fast, it is to classical estimators what Fast Fourier Transform （FFT） is to ordinary Discrete Fourier Transforms.展开更多
Construction land use has always been a key point for the planning department to practice national transformation strategy. In the new round of compilation of Beijing City Master Plan, the management of construction l...Construction land use has always been a key point for the planning department to practice national transformation strategy. In the new round of compilation of Beijing City Master Plan, the management of construction land use is under the rigid restriction of the bearing capacity of resources and the environment. Setting the upper-limit of the population size, a general strategy of decremented development of urban-rural construction land has been put forward, in order to realize a transition from quantitative expansion planning to qualitative upgrading planning. By "decremented development," "decremented" means a more rigid bottom-line restriction, and "development" means a more scientific allocation of resources. From the master planning level, the new Beijing City Master Plan establishes a comprehensive control framework and restrictive index system from perspectives including land use scale, construction scale, space boundary, urban and rural structure, land use structure, and cross-boundary collaboration; and in practice, it promotes strict management methods by setting up a dismantle-construction land ratio, dismantle-construction building area ratio, employment and residence land ratio, and "two lines and three districts," which is an exploration on the planning management method of construction land use that is stock-based and decremented master planning. Considering that decremented development is a major reform and a special challenge to planning implementation, the Beijing City Master Plan carries out explorations in terms of the planning management method, land policy, jurisdiction division, assessment and supervision, etc.展开更多
In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters...In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters is presented. This approach firstly uses random decrement technique to gain free decays corresponding to the acceleration response of the structure to some non-zero initial conditions. Then the continuous Morlet wavelet transformation of the free decays is performed; and the Parseval formula and residue theorem are used to simplify the transformation. The maximal wavelet transformation coefficients in different scales are searched out by means of band-filtering characteristic of Morlet wavelet, and then the modal parameters are identified according to the relationships with maximal modulus and angle of the wavelet transform. In addition, the condition of modal uncoupling is discussed according to variation trend of flight flutter modal parameters in the flight flutter state. The analysis results of simulation and flight flutter test data show that this approach is not only simple, effective and feasible, but also having good noise immunity.展开更多
文摘The dying-back hypothesis holds that the damage to neuromuscular junctions and distal axons in amyotrophic lateral sclerosis occurs at the earliest stage of the disease.Previous basic studies have confirmed early damage to neuromuscular junctions,but it is difficult to obtain such evidence directly in clinical practice.In this prospective cross-sectional study,we recruited 22 patients with early amyotrophic lateral sclerosis with disease duration < 12 months and with clinical symptoms limited to the upper limbs.We also recruited 32 healthy controls.Repetitive nerve stimulation was performed,and patients were followed for 12 months.We found a significant change in the response to repetitive nerve stimulation in amyotrophic lateral sclerosis patients without spontaneous electromyographic activity.Patients that were prone to denervation had an increased decrement response of target muscles after repetitive nerve stimulation.These results suggest that changes in response to repetitive nerve stimulation may occur before denervation in amyotrophic lateral sclerosis patients.The damage to lower motor neurons is more obvious in patients with a higher percentage of repetitive never stimulation-related amplitude decrements.This study was approved by the Institutional Ethics Committee of Peking University Third Hospital(approval No.M2017198) on August 24,2017.
文摘现代的大型复杂结构,如大坝、高层建筑、桥梁及海洋平台等,处于复杂的环境载荷作用下,这些环境载荷往往是无法测量的。在仅有输出响应时,应用随机减量法RDT获得自由衰减响应信号,而后用时域复指数拟合法、ITD法、特征系统实现算法ERA等算法获得结构的模态参数是一种有效的方法。但在数据量有限时,随机减量函数的平均次数过少,导致RD函数的收敛性较差。为此提出了利用Vector Random Decrement技术(VRDT)提取自由衰减响应信号,而后利用特征系统实现算法ERA求得模态参数的方法,新算法能够有效地提高模态参数识别精度。数值算例验证了所提算法的有效性。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41501240,41530855,41501241,and 41877026)the Natural Science Foundation of Chongqing CSTC(Grant No.cstc2018jcyjAX0318)the Fundamental Research Funds for the Central Universities,China(Grant No.XDJK2017B029)
文摘Surface potential is an important parameter related to the physical and chemical properties of charged particles. A simple analytical model for the estimation of surface potential is established based on the Poisson–Boltzmann theory with the consideration of the dielectric decrement in mixed electrolyte. The analytical relationships between surface potential and charge density are derived in different mixed electrolytes with monovalent and bivalent ions. The dielectric decrease on the charged surface strongly affects the surface potential at a high charge density with different ion strengths and concentration ratios of counter-ions. The surface potential based on the Gouy–Chapman model is underestimated because of the dielectric decrement on the surface. The diffuse layer can be regarded as a continuous uniform medium only when the surface charge density is lower than 0.3 C·m-2. However, the surface charge densities of many materials in practical applications are higher than 0.3 C·m-2. The new model for the estimation of surface potential can return to the results obtained based on the Gouy–Chapman model at a low charge density. Therefore, it is implied that the established model that considers the dielectric decrement is valid and widely applicable.
文摘Frequent item sets mining plays an important role in association rules mining. A variety of algorithms for finding frequent item sets in very large transaction databases have been developed. Although many techniques were proposed for maintenance of the discovered rules when new transactions are added, little work is done for maintaining the discovered rules when some transactions are deleted from the database. Updates are fundamental aspect of data management. In this paper, a decremental association rules mining algorithm is present for updating the discovered association rules when some transactions are removed from the original data set. Extensive experiments were conducted to evaluate the performance of the proposed algorithm. The results show that the proposed algorithm is efficient and outperforms other well-known algorithms.
文摘The observation of a left sided accessory pathway with decremental properties is rare. We describe the behaviour of one of these pathways which was characterized by the presence of retrograde conduction (not previously reported) and thus inducibility of atrio-ventricular orthodromic reentrant tachycardia.
基金Project supported by the National Natural Science Foundation of China.
文摘We compile the observed intensity ratios of the Balmer lines for low redshift quasars and Seyfert Ⅰ galaxies. In the framework of the Cerenkov line emission theory, we compare the theoretical intensity ratios with those of observations, and find that the observed intensity ratios for the radio-loud quasars and the Seyfert Ⅰ galaxies are nearer to the theoretical expectation than those for the radio-quiet sources. It seems that for the radio-loud AGNs, the characteristics of the Cerenkov line emission are more remarkable because of the existence of a great number of relativistic electrons. We also discuss the reddening by dust in quasars and the Seyfert galaxies. The fact that the reddening of the Seyfert galaxies is more serious than quasars shows that the Seyfert galaxies have more dust than quasars. This is in agreement with the present point of view.
基金Supported by SRF for ROCS, SEMNational Natural Science Foundation of China (Grant No. 10701058)+1 种基金Science and Technology Program of Beijing Education Commission (Grant No. KM200810028002)Institute of Mathematics and Interdisciplinary Science (Capital Normal University)
文摘The random decrement technique （RDT）, introduced in the sixties by Cole [NASA CR- 2005, 1973], is a very performing method of analysis for vibration signature of a structure under ambient loading. But the real nature of the random decrement signature has been misunderstood until now. Moreover, the various interpretations were made in continuous time setting, while real experimental data are obtained in discrete time. In this paper, the really implemental discrete time algorithms are studied. The asymptotic analysis as the number of triggering points go to infinity is achieved, and a Law of Large Numbers as well as a Central Limit Theorem is proved. Moreover, the limit as the discretization time step goes to zero is computed, giving more tractable formulas to approximate the random decrement. This is a new approach of the famous ＂Kac-Slepian paradox＂ [Ann. Math. Star., 30, 1215-1228 （1959）]. The main point might be that the RDT is a very efficient functional estimator of the correlation function of a stationary ergodic Gaussian process. Very fast, it is to classical estimators what Fast Fourier Transform （FFT） is to ordinary Discrete Fourier Transforms.
文摘Construction land use has always been a key point for the planning department to practice national transformation strategy. In the new round of compilation of Beijing City Master Plan, the management of construction land use is under the rigid restriction of the bearing capacity of resources and the environment. Setting the upper-limit of the population size, a general strategy of decremented development of urban-rural construction land has been put forward, in order to realize a transition from quantitative expansion planning to qualitative upgrading planning. By "decremented development," "decremented" means a more rigid bottom-line restriction, and "development" means a more scientific allocation of resources. From the master planning level, the new Beijing City Master Plan establishes a comprehensive control framework and restrictive index system from perspectives including land use scale, construction scale, space boundary, urban and rural structure, land use structure, and cross-boundary collaboration; and in practice, it promotes strict management methods by setting up a dismantle-construction land ratio, dismantle-construction building area ratio, employment and residence land ratio, and "two lines and three districts," which is an exploration on the planning management method of construction land use that is stock-based and decremented master planning. Considering that decremented development is a major reform and a special challenge to planning implementation, the Beijing City Master Plan carries out explorations in terms of the planning management method, land policy, jurisdiction division, assessment and supervision, etc.
基金National Natural Science Foundation of China(60134010)
文摘In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters is presented. This approach firstly uses random decrement technique to gain free decays corresponding to the acceleration response of the structure to some non-zero initial conditions. Then the continuous Morlet wavelet transformation of the free decays is performed; and the Parseval formula and residue theorem are used to simplify the transformation. The maximal wavelet transformation coefficients in different scales are searched out by means of band-filtering characteristic of Morlet wavelet, and then the modal parameters are identified according to the relationships with maximal modulus and angle of the wavelet transform. In addition, the condition of modal uncoupling is discussed according to variation trend of flight flutter modal parameters in the flight flutter state. The analysis results of simulation and flight flutter test data show that this approach is not only simple, effective and feasible, but also having good noise immunity.
