Based on a Hamfltonian identity, we study one-dimensional generalized hypervirial theorem, Blanchardlike （non-diagonal case） and Kramers＇ （diagonal case） recurrence relations for arbitrary x^k which is independen...Based on a Hamfltonian identity, we study one-dimensional generalized hypervirial theorem, Blanchardlike （non-diagonal case） and Kramers＇ （diagonal case） recurrence relations for arbitrary x^k which is independent of the central potential V（x）. Some significant results in diagonal case are obtained for special k in xk （k ≥2）. In particular, we find the orthogonal relation 〈n1｜n2〉 = δh1,n2 （k = 0）, 〈n1[V＇（x）｜n2〉 = （En1-En2）^2〈n1｜x｜n2〉 （k = 1）, En = （n｜V＇（x）x/2｜n〉 ＋ （n｜V（x）｜n〉 （k = 2） and -4En（n｜x｜n） ~ 〈n｜V＇（x）x^2｜n〉 ＋ 4〈n｜V（x）x｜n〉 =0 （k=3）. The latter two formulas can be used directly to calculate the energy levels. We present useYul explicit relations for some well known physical potentials without requiring the energy spectra of quantum system.展开更多
We show that the breakdown of dipole approximation can be adopted to explain the asymmetry structure in the photoelectron momentum distributions along the beam propagation direction, which is defined as the photoelect...We show that the breakdown of dipole approximation can be adopted to explain the asymmetry structure in the photoelectron momentum distributions along the beam propagation direction, which is defined as the photoelectron longitudinal momentum distributions（PLMD）, in tunneling regime（K ？ 1）, based on the strong field approximation theory. The nondipole Hamiltonian for photoelectrons interacting with laser fields from a hydrogen-like atom is transformed into the Kramers–Henneberger frame in our model. To introduce the correction of dipole approximation, the spatial variable is kept in a vector potential （r, t）, demonstrating that the breakdown of dipole approximation is the major reason for the shift of the peak in PLMD. The nondipole effects are apparent when circularly polarized lasers are adopted to ionize the atoms, and clear tendency to increase offsets is found for increasing laser intensities.展开更多
We propose and investigate the use of a Kramers–Kronig(KK) receiver in a single sideband orthogonal frequency division multiplexing radio over fiber(SSB-OFDM-RoF) link based on an optical remote heterodyne solution. ...We propose and investigate the use of a Kramers–Kronig(KK) receiver in a single sideband orthogonal frequency division multiplexing radio over fiber(SSB-OFDM-RoF) link based on an optical remote heterodyne solution. This scheme is effective in eliminating the signal-to-signal beating interference introduced by square-law detection of a photo-detector in an SSB-OFDM-RoF link. We extensively study the influences of different carrier-to-signal power ratios(CSPRs), laser linewidths, and transmission distances on our proposed scheme. It is proved that the KK-based receiver can reduce optimal CSPR by more than 5 dB and provide about 1.1 dB gain over the conventional mixer-based receiver scheme with CSPR of 11 dB after 75 km fiber transmission.展开更多
In the legal and philosophical study of torture,two major problems arise:Why is torture evil(Problem 1)?And is there a form of permissible torture(Problem 2)?The key issue in Problem 1 is demonstrating the uniqueness ...In the legal and philosophical study of torture,two major problems arise:Why is torture evil(Problem 1)?And is there a form of permissible torture(Problem 2)?The key issue in Problem 1 is demonstrating the uniqueness of the evils of torture,while Problem 2 aims to find a suitable theory to balance the“intuitive rejection”and“intuition of exceptional cases”in the ticking bomb scenario.Existing mainstream approaches have generally failed to resolve these issues.However,Matthew Kramer’s view of torture addresses both aspects of these problems.For Problem 1,Kramer adopts a perpetrator-centered viewpoint,arguing that torture undermines the moral integrity of the perpetrator.Regarding Problem 2,he suggests that the situation we face is a moral conflict in which the use of torture is morally wrong but might be the best action in a given context,granting it a weaker form of permissibility.However,in terms of the evils of torture,Kramer fails to explain its uniqueness.His theory cannot apply to all types of torture,and his perpetrator-centered argument contains logical flaws.Regarding the permissibility of torture,while Kramer’s overall approach is correct,he does not provide a reasonable explanation of the moral obligation to“forbid torture”or the prima facie surrounding it.A correct view of torture should adhere to an inmate-centered viewpoint,understanding the evils of torture in an additive manner in Problem 1,and acknowledging the existence of moral conflict in Problem 2.It should not only demonstrate that,in some situations,the use of torture may be the morally best option,but also show that the moral obligation to prohibit torture is simply outweighed under these circumstances.展开更多
In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean...In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first- passage time （MFPT） of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kraraers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.展开更多
基金Supported in part by Project 20150964-SIP-IPN,COFAA-IPN,Mexico
文摘Based on a Hamfltonian identity, we study one-dimensional generalized hypervirial theorem, Blanchardlike （non-diagonal case） and Kramers＇ （diagonal case） recurrence relations for arbitrary x^k which is independent of the central potential V（x）. Some significant results in diagonal case are obtained for special k in xk （k ≥2）. In particular, we find the orthogonal relation 〈n1｜n2〉 = δh1,n2 （k = 0）, 〈n1[V＇（x）｜n2〉 = （En1-En2）^2〈n1｜x｜n2〉 （k = 1）, En = （n｜V＇（x）x/2｜n〉 ＋ （n｜V（x）｜n〉 （k = 2） and -4En（n｜x｜n） ~ 〈n｜V＇（x）x^2｜n〉 ＋ 4〈n｜V（x）x｜n〉 =0 （k=3）. The latter two formulas can be used directly to calculate the energy levels. We present useYul explicit relations for some well known physical potentials without requiring the energy spectra of quantum system.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274149 and 11304185the Program of Shenyang Key Laboratory of Optoelectronic Materials and Technology under Grant No F12-254-1-00
文摘We show that the breakdown of dipole approximation can be adopted to explain the asymmetry structure in the photoelectron momentum distributions along the beam propagation direction, which is defined as the photoelectron longitudinal momentum distributions（PLMD）, in tunneling regime（K ？ 1）, based on the strong field approximation theory. The nondipole Hamiltonian for photoelectrons interacting with laser fields from a hydrogen-like atom is transformed into the Kramers–Henneberger frame in our model. To introduce the correction of dipole approximation, the spatial variable is kept in a vector potential （r, t）, demonstrating that the breakdown of dipole approximation is the major reason for the shift of the peak in PLMD. The nondipole effects are apparent when circularly polarized lasers are adopted to ionize the atoms, and clear tendency to increase offsets is found for increasing laser intensities.
基金supported by the National Natural Science Foundation of China(Nos.61420106011 and 61471088)the Fundamental Research Funds for the Central Universities(No.ZYGX2016J014)
文摘We propose and investigate the use of a Kramers–Kronig(KK) receiver in a single sideband orthogonal frequency division multiplexing radio over fiber(SSB-OFDM-RoF) link based on an optical remote heterodyne solution. This scheme is effective in eliminating the signal-to-signal beating interference introduced by square-law detection of a photo-detector in an SSB-OFDM-RoF link. We extensively study the influences of different carrier-to-signal power ratios(CSPRs), laser linewidths, and transmission distances on our proposed scheme. It is proved that the KK-based receiver can reduce optimal CSPR by more than 5 dB and provide about 1.1 dB gain over the conventional mixer-based receiver scheme with CSPR of 11 dB after 75 km fiber transmission.
基金This text represents a periodic outcome of the Beijing Social Science Fund Youth Project(Project Approval Number 22FXC018).
文摘In the legal and philosophical study of torture,two major problems arise:Why is torture evil(Problem 1)?And is there a form of permissible torture(Problem 2)?The key issue in Problem 1 is demonstrating the uniqueness of the evils of torture,while Problem 2 aims to find a suitable theory to balance the“intuitive rejection”and“intuition of exceptional cases”in the ticking bomb scenario.Existing mainstream approaches have generally failed to resolve these issues.However,Matthew Kramer’s view of torture addresses both aspects of these problems.For Problem 1,Kramer adopts a perpetrator-centered viewpoint,arguing that torture undermines the moral integrity of the perpetrator.Regarding Problem 2,he suggests that the situation we face is a moral conflict in which the use of torture is morally wrong but might be the best action in a given context,granting it a weaker form of permissibility.However,in terms of the evils of torture,Kramer fails to explain its uniqueness.His theory cannot apply to all types of torture,and his perpetrator-centered argument contains logical flaws.Regarding the permissibility of torture,while Kramer’s overall approach is correct,he does not provide a reasonable explanation of the moral obligation to“forbid torture”or the prima facie surrounding it.A correct view of torture should adhere to an inmate-centered viewpoint,understanding the evils of torture in an additive manner in Problem 1,and acknowledging the existence of moral conflict in Problem 2.It should not only demonstrate that,in some situations,the use of torture may be the morally best option,but also show that the moral obligation to prohibit torture is simply outweighed under these circumstances.
基金Project supported by the National Natural Science Foundation of China （Key Grant No 10332030）, the Specialized Research Fund for the Doctoral Program of Higher Education of China （Grant No 20060335125） and the National Science Foundation for Post-doctoral Scientists of China （Grant No 20060390338）.
文摘In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first- passage time （MFPT） of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kraraers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.
