Small glitches: the role of strange nuggets?

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）.

Observational features of pulsar glitches

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.

基于信号传输理论的Glitch物理不可克隆函数电路设计

通过对信号传输理论、竞争-冒险现象和物理不可克隆函数(Physical Unclonable Functions,PUF)电路的研究,论文提出一种基于信号传输理论的"毛刺"型物理不可克隆函数电路(Glitch Physical Unclonable Functions,Glitch-PUF)方案。该方案首先根据偏差延迟的信号传输理论,推导出获得稳定"毛刺"输出的电路级数;然后利用组合逻辑电路的传播延迟差异,结合"1"冒险和"0"冒险获得具有"毛刺"的输出波形,采用多级延迟采样电路实现Glitch-PUF的输出响应。由于"毛刺"信号具有显著的非线性特性,将其应用于PUF电路可有效解决模型攻击等问题。最后在TSMC 65 nm CMOS工艺下,设计128位数据输出的电路结构,Monte Carlo仿真结果表明Glitch-PUF电路具有良好的随机性。

基于秘密共享的AES的S盒实现与优化

针对构建新的密码结构抵抗DPA攻击尤其是glitch攻击的问题,通过将输入变换到复合域GF(((22)2)2)求逆,再变换回有限域GF(28)输出的方法构造了一个低消耗的AES的S盒;并基于秘密共享的思想分仿射变换、求逆变换、逆仿射变换3步对S盒进行分组,得到一个新的S盒。新的S盒在求逆变换中采用4×4的正确项分组法,相比于Nikova提出的经典方案,减少了实现所占用的空间,降低了消耗。通过分析验证,本文方案具有较为优良的消耗特性,且对1阶DPA攻击及glitch攻击具有与Nikova方案同等级的抵抗能力。

基于MLP算法的Glitch PUF机器学习攻击

随着攻击技术的不断进步,基于机器学习(Machine Learning,ML)、深度学习(Deep Learning,DL)等技术的建模攻击严重威胁了PUF的安全。针对Glitch PUF单元电路静态输出的缺陷,首次提出使用多层感知器(Multilayer Perceptron,MLP)算法对Glitch PUF进行机器学习,解决了Glitch PUF输出为非线性可分数据的问题,能够对Glitch PUF攻击并预测其输出。实验表明,对比于逻辑回归(Logistic Regression,LR)算法和随机森林(Random Forest,RF)二分类算法,提出的MLP算法显著降低了预测错误率。

高阶掩码防护的设计实现安全性研究

掩码对抗方案自提出以来,从一阶对抗逐渐发展至高阶对抗阶段,安全性及通用性也不断提高.最早的一阶掩码方案主要针对DES算法提出,而后出现的一阶掩码方案则大多以AES为防护目标,并针对于不同的软硬件平台,同时不断减少时间和空间耗费.在追求更高安全性的同时,高阶掩码方案也不断朝着通用化的方向发展,主要工作在于设计通用化的S盒掩码方案,保证可应用于任何S盒设计且可抵抗任意阶侧信道攻击.高阶掩码方案已被普遍接受为一种算法级可证明安全的侧信道防护方法,出现以ISW安全性框架为代表的理论安全性证明,以及在此框架下的任意阶掩码方案.然而面向侧信道分析,密码算法设计实现的安全性无法仅仅基于算法安全,针对这种掩码方案理论安全与实际安全间的差距,Roche与Prouff于2011年提出面向硬件设计的安全性掩码方案,但该方案无法运用于已有高阶掩码设计,只是对Rivain和Prouff在CHES2010上提出的RivP方案进行硬件级安全性实现.同时,以实现d阶安全的有限域乘法为例,实现需要加法和乘法的执行次数由O(d^2)增加到O(d^3),由于增加过多的设计资源而对执行效率有较大的影响,降低了方案的实用性.在高效安全的硬件设计平台上,首先,作者分析由于时延不同导致的glitch有可能泄露敏感信息.相比于组合逻辑设计,时序设计下的电路不会产生降阶泄露.除了已有的glitch泄露外,文中还发现存在与硬件设计结构相关的泄露.作者从密码芯片设计者的角度出发,对掩码方案中关键部件的不同硬件设计结构进行分析.作者利用互信息的方法分析并行设计所产生的安全性问题,从理论上证明并行设计存在的安全隐患.在找出掩码设计隐患的基础上给出安全、轻量的安全设计建议,并最终通过实验对比不同设计结构下高阶掩码方案硬件设计的安全性,证明实验结果与理论研究结论一致.

基于秘密共享的LBlock的S盒防御方案

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。

Pulsar B0531 + 21 in the Crab Nebula

The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab Nebula are regularly observed on the Large Phased Array of the Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute at a frequency 111 MHz. The connection between the scattering time scale of radio pulses and the dispersion measure of the pulsar, which was established earlier together with Jodrell Bank, is confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by dense plasma clouds with fluctuations in the electron density significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between period failers (glitches), dispersion measure variations, radio pulses scattering and gamma-ray flares is discussed.

基于延时控制的Glitch PUF电路设计

Glitch PUF具有良好的非线性特性,可以很好地抵御建模攻击的威胁,保证信息安全。提出一种延时控制的Glitch PUF电路架构。利用延时调节模块控制不同路径的延时大小,T触发器利用产生毛刺数量的奇偶性判决响应比特,使用Monte Carlo仿真验证所设计电路的性能。实验结果表明,所设计的Glitch PUF具有良好的唯一性和稳定性,且节约了资源。

A deeper understanding of the gut microbiota of different human races in search of disease specific microbial and metabolic biomarkers

Objective:Resident microorganisms live in dynamic harmony with their hosts to influence various physical and psychological health aspects.The majority of the resident microbes are found in the digestive tract,aka the gut of mammals.If and when perturbed,the composition of gut microbiota could jeopardize the physiological balance or homeostasis.In this article,we aim to establish how different diseases could be accompanied by notable changes in gut microbial composition and lend insight into microbial regulation of health.Methods:Literature search was done in PubMed using relevant keywords and summarized in tabular form as well as in narration.Results:We try to focus on the concept of microbial and metabolite biomarkers for diseases.We also try to capture the renewed perspective of good and harmful microorganisms in the context of host health.We have presented a comparative network analysis of microbial roles in select diseases.Recent findings also suggested that the growth of some traditionally disease-causing pathogenic microorganisms promotes health in other human communities.We have listed major taxa of gut microbes in communities worldwide,which signifies that gut microbiota can be healthy or harmful depending on the urbanization and ethnicity of the hosts.The traditional and current schools of thoughts are both limited by the technology of metagenomic studies;we have elucidated some of their shortcomings.Conclusion:Research in the field of gut microbiota must take into account the different populations and the changing narrative of healthy and harmful microbes.

一种分组密码S盒抗Glitch攻击的方案

伴随着网络信息时代的飞速发展,各种电子产品应运而生,人们的生活变得越来越智能,越来越便捷,然而在便捷的背后却隐藏着重大的安全隐患。密码芯片是保障信息安全的重要手段之一,所以提高密码芯片的安全性迫在眉睫。以Stefan等人的针对分组密码芯片S盒的Glitch攻击为模型背景,通过加入一组同步寄存器提出基于FPGA的一种针对分组密码S盒抗Glitch攻击的方案,并通过CMOS器件的属性和Altera公司在QuatusⅡ软件中嵌入的Signal Tap功能,从理论和仿真两方面分别验证了该方案不但能够大幅度减少Glitch的个数,还能够减少各级电路产生Glitch的相关性,从而降低了攻击的成功率,提高了分组密码S盒实现的安全性,为后续FPGA密码芯片的防护提供了依据。

Burgers方程的声速点故障问题

研究了在Burgers方程跨声速稀疏波计算中遇到的sonic point glitch问题,对它产生的原因及其与数值格式熵条件的关系进行了分析.对若干著名格式,按照是否满足熵条件进行了分类.为了消除sonic point glitch现象,提出了一种新的两步分裂方法,并用这种方法改进了一系列典型格式.数值试验表明这是一种很好的消除sonic point glitch的方法.

CMOS集成电路中Glitch Power的分析方法研究

在集成电路中器件延迟数学模型的基础上,介绍了如何利用定时布尔函数和定时有序二值决策图对集成电路GlitchPower进行分析;借助CUDD软件包,构建了电路的Timed-OBDD表达形式,对一些典型的BenchMark进行了仿真。

The symmetry energy and incompressibility constrained by the observations of glitching pulsars

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.

Glitch Crisis or Not:a Microscopic Study

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.

Efficient parameter inference for gravitational wave signals in the presence of transient noises using temporal and time-spectral fusion normalizing flow

Glitches represent a category of non-Gaussian and transient noise that frequently intersects with gravitational wave(GW)signals,thereby exerting a notable impact on the processing of GW data.The inference of GW parameters,crucial for GW astronomy research,is particularly susceptible to such interference.In this study,we pioneer the utilization of a temporal and time-spectral fusion normalizing flow for likelihood-free inference of GW parameters,seamlessly integrating the high temporal resolution of the time domain with the frequency separation characteristics of both time and frequency domains.Remarkably,our findings indicate that the accuracy of this inference method is comparable to that of traditional non-glitch sampling techniques.Furthermore,our approach exhibits a greater efficiency,boasting processing times on the order of milliseconds.In conclusion,the application of a normalizing flow emerges as pivotal in handling GW signals affected by transient noises,offering a promising avenue for enhancing the field of GW astronomy research.

Neutron star core-crust transition and the crustal moment of inertia in the nonlinear relativistic Hartree approximation

We investigate the effects of theσmeson mass(m_(σ)),symmetry energy,and slope of the symmetry energy on the neutron star core-crust transition density and the crustal moment of inertia(ΔI/I)in the nonlinear relativistic Hartree approach(RHA),which includes vacuum polarization.Although the core-crust transition density(ρ_(t)),pressure(P_(t)),and neutron star radius(R),which are all dependent on the symmetry energy,contribute to determiningΔI/I,we find that changing only the slope of symmetry energy within a reasonable range is not sufficient to reachΔI/I≥7%to achieve the large glitches of the Vela pulsar.However,since all three factors(ρ_(t),P_(t),and R)increase with the increase in mσthrough scalar vacuum polarization,adjusting mσcan easily achieveΔI/I≥7%.

Crust-core properties of neutron stars in the Nambu–Jona-Lasinio model

We adopt the Nambu–Jona-Lasinio(NJL) model to study the crust-core transition properties in neutron stars(NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure.Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 Me V, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction(7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 Me V and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 M.

A low reference spur quadrature phase-locked loop for UWB systems

This paper presents a low phase noise and low reference spur quadrature phase-locked loop （QPLL） circuit that is implemented as a part ofa fi＇equency synthesizer for China UWB standard systems. A glitch-suppressed charge pump （CP） is employed for reference spur reduction. By forcing the phase frequency detector and CP to operate in a linear region of its transfer function, the linearity of the QPLL is further improved. With the proposed series-quadrature voltage-controlled oscillator, the phase accuracy of the QPLL is guaranteed. The circuit is fab- ricated in the TSMC 0.13/Jm CMOS process and operated at 1.2-V supply voltage. The QPLL measures a phase noise of -95 dBc/Hz at 100-kHz offset and a reference spur of-71 dBc. The fully-integrated QPLL dissipates a current of 13 mA.

A low glitch 12-bit current-steering CMOS DAC for CNC systems

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.