We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of ...We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of neutron stars. With the assumption that glitches are triggered by superfluid neutrons, the masses of glitching neutron stars can be estimated using observations of maximum glitches.Together with the observations of thermal emission from glitching pulsars Vela and J1709–4429, the slope of symmetry energy and incompressibility of nuclear matter at saturation density can be constrained.The slope of symmetry energy L should be larger than 67 MeV while the lower limit of incompressibility for symmetric nuclear matter K_0 is 215 MeV. We also obtain a relationship between L and K_0:6.173 MeV + 0.283 K_0≤ L ≤ 7.729 MeV + 0.291 K_0. The restricted EOSs are consistent with the observations of 2-solar-mass neutron stars and gravitational waves from a binary neutron star inspiral.展开更多
Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framew...Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym ＆ Pines, the glitch sizes（the relative increases of spin-frequencies during glitches） △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets（SNs） which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ？？/？ are smaller than those in the standard starquake model（with larger amounts of released energy）. Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches（e.g.,by the Square Kilometre Array）.展开更多
The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in...The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However7 the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4M⊙ canonical star, based on a microscopic equation of state for the neutron star＇s core using the Brueckner-Hartree-Fock approach. For this purpose, two requisite parameters are chosen as follows： the core-crust transition pressure is in the range of Pt = 0.2-0.65 MeV/fm3, and the fractional crust radius AR/R = 0.082 based on experiments. To account for the possibility of a heavier star, a larger value of AR/R = 0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.展开更多
Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from ...Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from 2000 to 2008, including several events which appear to be slow glitches. A wide variety of post-glitch behavior is observed with very little recovery in some pulsars and over-recovery in others. Analysis of the whole sample of known glitches shows that fractional glitch amplitudes are correlated with characteristic age with a peak at about 105 years, but there is a spread of two or three orders of magnitude at all ages. For individual pulsars with many glitches, the time until the next glitch is sometimes proportional to the fractional glitch amplitude.展开更多
A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC （computer number control） systems is presented. To reduce the glitch and increase the SFDR （spurious-free dynamic range）, a low crosspoint switch drive...A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC （computer number control） systems is presented. To reduce the glitch and increase the SFDR （spurious-free dynamic range）, a low crosspoint switch driver and a special dummy switch are applied. In addition, a 4-5-3 segmental structure is used to optimize the performance and layout area. After improvement, the biggest glitch energy decreased from 6.7 pVs to 1.7 pVs, the INL decreased from 2 LSB to 0.8 LSB, the SFDR is 78 dB at a 100-MSPS clock rate and 1 MHz output frequency. This DAC can deliver up to 20.8 mA full-scale current into a 50 Ω load. The power when operating at full-scale current is 163 mW. The layout area is 1.8 × 1.8 mm2 in a standard 0.35-um CMOS technology.展开更多
针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由G...针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由GF(24)转移到GF(22)上,减少硬件消耗的同时,又提高了算法的安全性。在乘法器分组中采用虚拟值方法,以保证满足门限方案的均匀性,并在反相器中引入分解法,以保证各信息分组相关独立且线性无关。分析验证表明,方案满足门限方案所需要的各项性质,并且可以抵御一阶、二阶DPA攻击。所有的信息分组都是独立且无联系的,所以该方案对于glitch攻击也具有相应的防护能力,具有较好的实用性。展开更多
基金supported by the National Basic Research Program of China (2014CB845800)the National Natural Science Foundation of China (Grant No. 11573014)
文摘We investigate the masses of glitching pulsars in order to constrain their equation of state(EOS). The observations of glitches(sudden jumps in rotational frequency) may provide information on the interior physics of neutron stars. With the assumption that glitches are triggered by superfluid neutrons, the masses of glitching neutron stars can be estimated using observations of maximum glitches.Together with the observations of thermal emission from glitching pulsars Vela and J1709–4429, the slope of symmetry energy and incompressibility of nuclear matter at saturation density can be constrained.The slope of symmetry energy L should be larger than 67 MeV while the lower limit of incompressibility for symmetric nuclear matter K_0 is 215 MeV. We also obtain a relationship between L and K_0:6.173 MeV + 0.283 K_0≤ L ≤ 7.729 MeV + 0.291 K_0. The restricted EOSs are consistent with the observations of 2-solar-mass neutron stars and gravitational waves from a binary neutron star inspiral.
基金supported by the National Natural Science Foundation of China (11203018)the West Light Foundation (XBBS-2014-23)+1 种基金the Science Project of Universities in Xinjiang (XJEDU2012S02)the Doctoral Science Foundation of Xinjiang University (BS120107)
文摘Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym ＆ Pines, the glitch sizes（the relative increases of spin-frequencies during glitches） △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets（SNs） which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ？？/？ are smaller than those in the standard starquake model（with larger amounts of released energy）. Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches（e.g.,by the Square Kilometre Array）.
基金Supported by the National Natural Science Foundation of China under Grant No U1431107
文摘The problem of glitch crisis has been a great deal of debate recently. It might challenge the standard two- component model, where glitches are thought to be triggered by the sudden unpinning of superfluid vortices in the neutron-star crust. It says that due to crustal entrainment the amount of superfluid in the crust cannot explain the changes in angular momentum required to account for the glitches. However7 the argument of this crisis is based on the assumption that the core superfluid is completely coupled to the crust when a glitch happens. The fraction of the coupled core part is actually a quite uncertain problem so far. In this work, we take three possible values for the fraction of the coupled core part and study in detail the crisis problem for a 1.4M⊙ canonical star, based on a microscopic equation of state for the neutron star＇s core using the Brueckner-Hartree-Fock approach. For this purpose, two requisite parameters are chosen as follows： the core-crust transition pressure is in the range of Pt = 0.2-0.65 MeV/fm3, and the fractional crust radius AR/R = 0.082 based on experiments. To account for the possibility of a heavier star, a larger value of AR/R = 0.15 is also chosen for comparison. Then we take the crustal entrainment into account, and evaluate the predictions for the fractional moment of inertia at various conditions. The results show that there is commonly no such glitch crisis, as long as one considers only a small fraction of the core neutron superfluid will contribute to the charged component of the star. Only if the core-crust transition pressure is determined to be a low value, the crisis problem may appear for complete core-crust coupling. This is consistent with a recent study in a phenomenological model.
基金supported by the National Basic Research Program of China (Grant No. 2009CB824800)the National Natural Science Foundation of China (Grant No. 10673021)the Knowledge Innovation Program of CAS Project (Grant No. KJCX2-YW-T09)
文摘Pulsar glitches are sudden increases in the rotation rate which probably result from angular momentum transfer within the neutron star. We review the observational features of the 39 glitches detected at Nanshan from 2000 to 2008, including several events which appear to be slow glitches. A wide variety of post-glitch behavior is observed with very little recovery in some pulsars and over-recovery in others. Analysis of the whole sample of known glitches shows that fractional glitch amplitudes are correlated with characteristic age with a peak at about 105 years, but there is a spread of two or three orders of magnitude at all ages. For individual pulsars with many glitches, the time until the next glitch is sometimes proportional to the fractional glitch amplitude.
基金Project supported by the Hubei Natural Science Foundation of China(No.2010CDB02706)
文摘A 12-bit, 100-MHz CMOS current-steering D/A converter for CNC （computer number control） systems is presented. To reduce the glitch and increase the SFDR （spurious-free dynamic range）, a low crosspoint switch driver and a special dummy switch are applied. In addition, a 4-5-3 segmental structure is used to optimize the performance and layout area. After improvement, the biggest glitch energy decreased from 6.7 pVs to 1.7 pVs, the INL decreased from 2 LSB to 0.8 LSB, the SFDR is 78 dB at a 100-MSPS clock rate and 1 MHz output frequency. This DAC can deliver up to 20.8 mA full-scale current into a 50 Ω load. The power when operating at full-scale current is 163 mW. The layout area is 1.8 × 1.8 mm2 in a standard 0.35-um CMOS technology.
文摘通过对比NICER(Neutron Star Interior Composition Explorer)和XPNAV-1(X-ray Pulsar Navigation-1)关于Crab脉冲星同一时段(108天)观测数据的计时处理结果,发现在周期跃变发生前的时段(95天),NICER数据的拟合前计时残差的RMS(root mean square)为5.77μs,远优于XPNAV-1数据的拟合前计时残差的RMS 51.56μs,体现了NICER在有效面积、探测效率、数据采集等方面的优势,给未来我国的X射线脉冲星探测器研制提供了发展方向;而在周期跃变发生后的时段(13天),发现XPNAV-1数据的拟合前计时残差的RMS为55.87μs,而NICER数据的拟合前计时残差的RMS为167.27μs,周期跃变对NICER的影响更大,说明在处理周期跃变发生后时段的NICER数据时,由于NICER的观测精度非常高,需要更频繁地更新Crab星历。最后分别得到了两个探测器整段数据的计时残差。XPNAV-1数据的拟合前计时残差的RMS为55.94μs,而NICER数据的拟合前计时残差的RMS为64.34μs,这说明NICER数据受周期跃变影响更为明显,进一步证明了上述结论。
文摘针对LBlock算法在侧信道攻击前脆弱的问题,文章提出一种可以抵抗一阶和二阶差分功耗攻击(Differential Power Analysis,DPA)的门限防护方案。该方案以秘密共享原理为基础理论,并且在算法进行运算时采用了复合域的概念,将算法的运算域由GF(24)转移到GF(22)上,减少硬件消耗的同时,又提高了算法的安全性。在乘法器分组中采用虚拟值方法,以保证满足门限方案的均匀性,并在反相器中引入分解法,以保证各信息分组相关独立且线性无关。分析验证表明,方案满足门限方案所需要的各项性质,并且可以抵御一阶、二阶DPA攻击。所有的信息分组都是独立且无联系的,所以该方案对于glitch攻击也具有相应的防护能力,具有较好的实用性。
