在英国民间的传说中,一直有一个著名的侠盗RobinHood为世人所熟知,他的故事可以说在当地是家喻户晓。同样的,即使在中国,侠盗罗宾汉的名字作为正义、勇敢的化身也为很多朋友所熟悉。作为一个虚构的人物,能有如此之多的朋友对这位侠盗的...在英国民间的传说中,一直有一个著名的侠盗RobinHood为世人所熟知,他的故事可以说在当地是家喻户晓。同样的,即使在中国,侠盗罗宾汉的名字作为正义、勇敢的化身也为很多朋友所熟悉。作为一个虚构的人物,能有如此之多的朋友对这位侠盗的传奇产生兴趣,确实很不一般。那么现在令大家激动的是,你将有机会通过由国外的Spellbound公司翻作,国内怡采科技代理的大作:《罗宾汉——舍伍德的传说》(RobinHood:Legend of Sherwood)来真正身临其境地与罗宾汉一同体验一次次惊险的冒险旅程,这未尝不是一件愉快的事情。下面,笔者就带领大家一同来领略一下这款即将上市的大作的特别之处。展开更多
Let T be pure subnormal operator. In this paper necessary and sufficiert conditions that T=N+K are given,where N is normal, K is quasinormal and NK=KN.
Heroin is considered potent and addictive and users are often stigmatised as the other. On the internet, however, hegemonic ideas about drugs can be resisted. This study elucidates how efforts to uormalise and demonis...Heroin is considered potent and addictive and users are often stigmatised as the other. On the internet, however, hegemonic ideas about drugs can be resisted. This study elucidates how efforts to uormalise and demonise heroin meet at a Swedish online message board （Flashback Forum）. The study aims at analysing how heroin use is given meaning by discussants in a thread called ＂I will start with heroin＂. The data were perceived and structured as a collaborative, overarching narrative about when, why, and for whom heroin use can make sense. Discussants used stories about pleasure-seekers, miserable junkies, and self-medicating addicts to depict the activity as unproblematic and rational, problematic and irrational, or as problematic and rational. No stories about heroin use departed from the plot-lines of pleasure maximisation and pain minimisation. Results elucidate a discursive battle in which： （1） heroin use as minimisation of pain ＂wins＂ over heroin use as maximisation of pleasure; and （2） there is a general agreement that heroin use cannot be irrational and unproblematic at the same time. It is suggested that these features are central to contemporary drug discourse, and that they probably hinder public understanding of why people use heroin and therefore contribute to keep users stigmatised.展开更多
While the scattering phase for several one-dimensional potentials can be exactly derived, less is known in multi-dimensional quantum systems. This work provides a method to extend the one-dimensional phase knowledge t...While the scattering phase for several one-dimensional potentials can be exactly derived, less is known in multi-dimensional quantum systems. This work provides a method to extend the one-dimensional phase knowledge to multi-dimensional quantization rules. The extension is illustrated in the example of Bogomolny＇s transfer operator method applied in two quantum wells bounded by step potentials of different heights. This generalized semiclassical method accurately determines the energy spectrum of the systems, which indicates the substantial role of the proposed phase correction. Theoretically, the result can be extended to other semiclassical methods, such as Gutzwiller trace formula, dynamical zeta functions, and semielassical Landauer Buttiker formula. In practice, this recipe enhances the applicability of semiclassical methods to multi-dimensional quantum systems bounded by general soft potentials.展开更多
Compressed Sensing （CS） offers a method to solve the channel estimation problems for an underwater acoustic system, based on the existence of a sparse representation of the treated signal and an overcomplete diction...Compressed Sensing （CS） offers a method to solve the channel estimation problems for an underwater acoustic system, based on the existence of a sparse representation of the treated signal and an overcomplete dictionary with a set of non-orthogonal bases. In this paper, we proposed a new approach to optimize dictionaries by decreasing the average measure of the mutual coherence of the effective dictionary. A fixed link between the average mutual coherence and the CS perforrmnce is indicated by designing three factors： operating bandwidth, the number of pilot subcarriers, and coherence bandwidth. Both the Orthogonal Matching Pursuit （OMP） and the Basis Pursuit De-Noising （BPDN） are compared to the Dantzig Selector （DS） for different Signal Noise Ratio （SNR） and shown to benefit from the newly designed dictionary. Nurnerical sinmlations and experimental data of an OFDM receiver are used to evaluate the proposed method in comparison with the conventional LeastSquare （LS） estirmtor. The results show that the dictionary with a better condition considerably improves the perforrmnce of the channel estimation.展开更多
Power-line interference is one of the most common noises in magnetotelluric(MT)data.It usually causes distortion at the fundamental frequency and its odd harmonics,and may also affect other frequency bands.Although tr...Power-line interference is one of the most common noises in magnetotelluric(MT)data.It usually causes distortion at the fundamental frequency and its odd harmonics,and may also affect other frequency bands.Although trap circuits are designed to suppress such noise in most of the modern acquisition devices,strong interferences are still found in MT data,and the power-line interference will fluctuate with the changing of load current.The fixed trap circuits often fail to deal with it.This paper proposes an alternative scheme for power-line interference removal based on frequency-domain sparse decomposition.Firstly,the fast Fourier transform of the acquired MT signal is performed.Subsequently,a redundant dictionary is designed to match with the power-line interference which is insensitive to the useful signal.Power-line interference is separated by using the dictionary and a signal reconstruction algorithm of compressive sensing called improved orthogonal matching pursuit(IOMP).Finally,the frequency domain data are switched back to the time domain by the inverse fast Fourier transform.Simulation experiments and real data examples from Lu-Zong ore district illustrate that this scheme can effectively suppress the power-line interference and significantly improve data quality.Compared with time domain sparse decomposition,this scheme takes less time consumption and acquires better results.展开更多
文摘在英国民间的传说中,一直有一个著名的侠盗RobinHood为世人所熟知,他的故事可以说在当地是家喻户晓。同样的,即使在中国,侠盗罗宾汉的名字作为正义、勇敢的化身也为很多朋友所熟悉。作为一个虚构的人物,能有如此之多的朋友对这位侠盗的传奇产生兴趣,确实很不一般。那么现在令大家激动的是,你将有机会通过由国外的Spellbound公司翻作,国内怡采科技代理的大作:《罗宾汉——舍伍德的传说》(RobinHood:Legend of Sherwood)来真正身临其境地与罗宾汉一同体验一次次惊险的冒险旅程,这未尝不是一件愉快的事情。下面,笔者就带领大家一同来领略一下这款即将上市的大作的特别之处。
文摘Let T be pure subnormal operator. In this paper necessary and sufficiert conditions that T=N+K are given,where N is normal, K is quasinormal and NK=KN.
文摘Heroin is considered potent and addictive and users are often stigmatised as the other. On the internet, however, hegemonic ideas about drugs can be resisted. This study elucidates how efforts to uormalise and demonise heroin meet at a Swedish online message board （Flashback Forum）. The study aims at analysing how heroin use is given meaning by discussants in a thread called ＂I will start with heroin＂. The data were perceived and structured as a collaborative, overarching narrative about when, why, and for whom heroin use can make sense. Discussants used stories about pleasure-seekers, miserable junkies, and self-medicating addicts to depict the activity as unproblematic and rational, problematic and irrational, or as problematic and rational. No stories about heroin use departed from the plot-lines of pleasure maximisation and pain minimisation. Results elucidate a discursive battle in which： （1） heroin use as minimisation of pain ＂wins＂ over heroin use as maximisation of pleasure; and （2） there is a general agreement that heroin use cannot be irrational and unproblematic at the same time. It is suggested that these features are central to contemporary drug discourse, and that they probably hinder public understanding of why people use heroin and therefore contribute to keep users stigmatised.
基金Supported by the National Science Council at Taiwan through Grants No. NSC 97-2112-M-009-008-MY3
文摘While the scattering phase for several one-dimensional potentials can be exactly derived, less is known in multi-dimensional quantum systems. This work provides a method to extend the one-dimensional phase knowledge to multi-dimensional quantization rules. The extension is illustrated in the example of Bogomolny＇s transfer operator method applied in two quantum wells bounded by step potentials of different heights. This generalized semiclassical method accurately determines the energy spectrum of the systems, which indicates the substantial role of the proposed phase correction. Theoretically, the result can be extended to other semiclassical methods, such as Gutzwiller trace formula, dynamical zeta functions, and semielassical Landauer Buttiker formula. In practice, this recipe enhances the applicability of semiclassical methods to multi-dimensional quantum systems bounded by general soft potentials.
基金Acknowledgements This work was supported by the National Science Foundation of China under Grant No. 60976065. The authors would like to thank the anonymous reviewers for comments that helped improve the paper.
文摘Compressed Sensing （CS） offers a method to solve the channel estimation problems for an underwater acoustic system, based on the existence of a sparse representation of the treated signal and an overcomplete dictionary with a set of non-orthogonal bases. In this paper, we proposed a new approach to optimize dictionaries by decreasing the average measure of the mutual coherence of the effective dictionary. A fixed link between the average mutual coherence and the CS perforrmnce is indicated by designing three factors： operating bandwidth, the number of pilot subcarriers, and coherence bandwidth. Both the Orthogonal Matching Pursuit （OMP） and the Basis Pursuit De-Noising （BPDN） are compared to the Dantzig Selector （DS） for different Signal Noise Ratio （SNR） and shown to benefit from the newly designed dictionary. Nurnerical sinmlations and experimental data of an OFDM receiver are used to evaluate the proposed method in comparison with the conventional LeastSquare （LS） estirmtor. The results show that the dictionary with a better condition considerably improves the perforrmnce of the channel estimation.
基金Project(2014AA06A602)supported by the National High-Tech Research and Development Program of ChinaProjects(41404111,41304098)supported by the National Natural Science Foundation of ChinaProject(2015JJ3088)supported by the Natural Science Foundation of Hunan Province,China
文摘Power-line interference is one of the most common noises in magnetotelluric(MT)data.It usually causes distortion at the fundamental frequency and its odd harmonics,and may also affect other frequency bands.Although trap circuits are designed to suppress such noise in most of the modern acquisition devices,strong interferences are still found in MT data,and the power-line interference will fluctuate with the changing of load current.The fixed trap circuits often fail to deal with it.This paper proposes an alternative scheme for power-line interference removal based on frequency-domain sparse decomposition.Firstly,the fast Fourier transform of the acquired MT signal is performed.Subsequently,a redundant dictionary is designed to match with the power-line interference which is insensitive to the useful signal.Power-line interference is separated by using the dictionary and a signal reconstruction algorithm of compressive sensing called improved orthogonal matching pursuit(IOMP).Finally,the frequency domain data are switched back to the time domain by the inverse fast Fourier transform.Simulation experiments and real data examples from Lu-Zong ore district illustrate that this scheme can effectively suppress the power-line interference and significantly improve data quality.Compared with time domain sparse decomposition,this scheme takes less time consumption and acquires better results.
