In terms of security and privacy,mobile ad-hoc network(MANET)continues to be in demand for additional debate and development.As more MANET applications become data-oriented,implementing a secure and reliable data tran...In terms of security and privacy,mobile ad-hoc network(MANET)continues to be in demand for additional debate and development.As more MANET applications become data-oriented,implementing a secure and reliable data transfer protocol becomes a major concern in the architecture.However,MANET’s lack of infrastructure,unpredictable topology,and restricted resources,as well as the lack of a previously permitted trust relationship among connected nodes,contribute to the attack detection burden.A novel detection approach is presented in this paper to classify passive and active black-hole attacks.The proposed approach is based on the dipper throated optimization(DTO)algorithm,which presents a plausible path out of multiple paths for statistics transmission to boost MANETs’quality of service.A group of selected packet features will then be weighed by the DTO-based multi-layer perceptron(DTO-MLP),and these features are collected from nodes using the Low Energy Adaptive Clustering Hierarchical(LEACH)clustering technique.MLP is a powerful classifier and the DTO weight optimization method has a significant impact on improving the classification process by strengthening the weights of key features while suppressing the weights ofminor features.This hybridmethod is primarily designed to combat active black-hole assaults.Using the LEACH clustering phase,however,can also detect passive black-hole attacks.The effect of mobility variation on detection error and routing overhead is explored and evaluated using the suggested approach.For diverse mobility situations,the results demonstrate up to 97%detection accuracy and faster execution time.Furthermore,the suggested approach uses an adjustable threshold value to make a correct conclusion regarding whether a node is malicious or benign.展开更多
The Network Layer in wireless mesh networks is responsible for routing packets making it a prime target for intruders and hackers. Black-hole attack is a type of denial-of-service attack which when carried out can dis...The Network Layer in wireless mesh networks is responsible for routing packets making it a prime target for intruders and hackers. Black-hole attack is a type of denial-of-service attack which when carried out can disrupt the services of this layer. This paper takes a look at some important detection and mitigation techniques and presents the drawbacks. After analysis of current mechanisms, the paper proposes RID-AODV, a security solution for multiple black-hole attack in wireless mesh networks. Based on the backbone of AODV, RID-AODV combines the ability of route skipping of IDSAODV and route failure correction using reverse route establishment of RAODV. The enhanced protocol RID-AODV, AODV, IDSAODV, and RAODV are implemented in a simulated environment using ns-2.35 simulator. The networks for each protocol are bombarded with up to ten black-hole nodes starting from zero. The results obtained are then analyzed and compared and a discussion is presented.展开更多
We present the results of the spectral fits made to 59 Rossi X-ray Timing Explorer （RXTE） observations of the Galactic X-Ray Black-Hole Candidate XTE J1650–500 covering the first 30d of its 2001/2002 outburst when ...We present the results of the spectral fits made to 59 Rossi X-ray Timing Explorer （RXTE） observations of the Galactic X-Ray Black-Hole Candidate XTE J1650–500 covering the first 30d of its 2001/2002 outburst when the source was in a transition from the hard state to the soft state. The photon spectra can be well fit- ted with a phenomenological model of a power-law/cutoff power-law and a physical model of bulk-motion Comptonization. The spectral properties smoothly evolve away from the hard state and then stay in the soft state. The fitting results of the physical model reveal the peak of the burst had a flux of 2.90 × 10-8 erg cm-2 s-1 in the 2–100 keV energy range and was observed on 2001 Sep. 9; it transitioned to the hard state. The total flux decays by a factor of ～3 as it evolves into the soft state. The photon index Γ increases from ～1.5 in the hard state and stays at ～2.5 in the soft state. We found that the effective area of the high-energy X-ray emission region （the Compton cloud） decreases, i.e. the area of the Compton cloud decreases by a factor of ～23 during the transition from the hard state to the soft state. Combining the new radio and quasi-periodic oscillation studies, the model of total flux in the 2–100 keV energy range, the jet emission and the timing analysis during the state transition, we suggest a possible geometry and evolution for the （jet＋corona＋disk） system, like that proposed by Kalemci et al. based on enhanced lags and peak frequency shift during the transition.展开更多
In this work,we investigate a possible conceptual link between torus-shaped black hole solutions of the vacuum gravitational field equations in(1+3)-dimensional general relativity and mitochondrial DNA(mtDNA).We propo...In this work,we investigate a possible conceptual link between torus-shaped black hole solutions of the vacuum gravitational field equations in(1+3)-dimensional general relativity and mitochondrial DNA(mtDNA).We propose that this analogy could serve as a framework for transferring insights and methodologies between the study of mtDNA and toroidal black hole geometries.By establishing this connection,we aim to provide novel perspectives that could contribute to advancements in both theoretical physics and molecular biology,offering new tools for understanding complex structures in these disciplines.展开更多
A disformal rotating black-hole solution is a black-hole solution in quadratic degenerate higher-order scalar-tensor theories.It breaks the circular condition of spacetime different from the case of the usual Kerr spa...A disformal rotating black-hole solution is a black-hole solution in quadratic degenerate higher-order scalar-tensor theories.It breaks the circular condition of spacetime different from the case of the usual Kerr spacetime.This study investigated the dynamic behaviors of the motion of timelike particles in such disformal black-hole spacetime with an extra deformation parameter.Results showed that the characteristics of the particle’s motion depend on the sign of the deformation parameter.For the positive deformation parameter,the motion is regular and orderly.For the negative one,as the deformation parameter changes,the motion of the particles undergoes a series of transitions between the chaotic motion and the regular motion and falls into the horizon or escapes to spatial infinity.This means that the dynamic behavior of timelike particles in the disformal Kerr black-hole spacetime with noncircularity becomes richer than that in the usual Kerr black-hole case.展开更多
声学黑洞(acoustic black hole,ABH)作为一种高效的弯曲波控制技术,在振动控制领域得到了广泛应用。针对传统单个声学黑洞特征尺寸与有效作用频率难以协调的问题,借鉴声子晶体设计思路,充分发挥声学黑洞振子高阻尼、多模态的优势,提出...声学黑洞(acoustic black hole,ABH)作为一种高效的弯曲波控制技术,在振动控制领域得到了广泛应用。针对传统单个声学黑洞特征尺寸与有效作用频率难以协调的问题,借鉴声子晶体设计思路,充分发挥声学黑洞振子高阻尼、多模态的优势,提出了一种局域共振型声学黑洞夹层板周期结构。通过结合能带曲线的带隙边缘模态分析与振子的谐振特性,系统阐明了弯曲波带隙的形成机制,并探究了单胞设计参数对带隙的影响规律。同时,通过增加配重和引入阻尼等优化策略,进一步拓宽了带隙范围,并实现了更低频带隙的有效打开。建立了声学黑洞夹层板周期结构的仿真和试验模型,仿真和试验结果表明,该结构在300 Hz范围内形成了显著的带隙特性,带隙中心频率最低至50 Hz以下,表现出良好的振动衰减效果。这一研究为浮筏结构的低频宽频减振设计提供了思路与技术路径。展开更多
文摘In terms of security and privacy,mobile ad-hoc network(MANET)continues to be in demand for additional debate and development.As more MANET applications become data-oriented,implementing a secure and reliable data transfer protocol becomes a major concern in the architecture.However,MANET’s lack of infrastructure,unpredictable topology,and restricted resources,as well as the lack of a previously permitted trust relationship among connected nodes,contribute to the attack detection burden.A novel detection approach is presented in this paper to classify passive and active black-hole attacks.The proposed approach is based on the dipper throated optimization(DTO)algorithm,which presents a plausible path out of multiple paths for statistics transmission to boost MANETs’quality of service.A group of selected packet features will then be weighed by the DTO-based multi-layer perceptron(DTO-MLP),and these features are collected from nodes using the Low Energy Adaptive Clustering Hierarchical(LEACH)clustering technique.MLP is a powerful classifier and the DTO weight optimization method has a significant impact on improving the classification process by strengthening the weights of key features while suppressing the weights ofminor features.This hybridmethod is primarily designed to combat active black-hole assaults.Using the LEACH clustering phase,however,can also detect passive black-hole attacks.The effect of mobility variation on detection error and routing overhead is explored and evaluated using the suggested approach.For diverse mobility situations,the results demonstrate up to 97%detection accuracy and faster execution time.Furthermore,the suggested approach uses an adjustable threshold value to make a correct conclusion regarding whether a node is malicious or benign.
文摘The Network Layer in wireless mesh networks is responsible for routing packets making it a prime target for intruders and hackers. Black-hole attack is a type of denial-of-service attack which when carried out can disrupt the services of this layer. This paper takes a look at some important detection and mitigation techniques and presents the drawbacks. After analysis of current mechanisms, the paper proposes RID-AODV, a security solution for multiple black-hole attack in wireless mesh networks. Based on the backbone of AODV, RID-AODV combines the ability of route skipping of IDSAODV and route failure correction using reverse route establishment of RAODV. The enhanced protocol RID-AODV, AODV, IDSAODV, and RAODV are implemented in a simulated environment using ns-2.35 simulator. The networks for each protocol are bombarded with up to ten black-hole nodes starting from zero. The results obtained are then analyzed and compared and a discussion is presented.
基金partially supported by the Grant-in-Aid for Scientific Research on Priority Areas (Grant No. 14079101)financial supports from the National Natural Science Foundation of China (Grant No. 10778702)+1 种基金the National Basic Research Program of China (973 Program, Grant No. 2009CB824800)the Policy Research Program of Chinese Academy of Sciences (KJCX2-YWT24)
文摘We present the results of the spectral fits made to 59 Rossi X-ray Timing Explorer （RXTE） observations of the Galactic X-Ray Black-Hole Candidate XTE J1650–500 covering the first 30d of its 2001/2002 outburst when the source was in a transition from the hard state to the soft state. The photon spectra can be well fit- ted with a phenomenological model of a power-law/cutoff power-law and a physical model of bulk-motion Comptonization. The spectral properties smoothly evolve away from the hard state and then stay in the soft state. The fitting results of the physical model reveal the peak of the burst had a flux of 2.90 × 10-8 erg cm-2 s-1 in the 2–100 keV energy range and was observed on 2001 Sep. 9; it transitioned to the hard state. The total flux decays by a factor of ～3 as it evolves into the soft state. The photon index Γ increases from ～1.5 in the hard state and stays at ～2.5 in the soft state. We found that the effective area of the high-energy X-ray emission region （the Compton cloud） decreases, i.e. the area of the Compton cloud decreases by a factor of ～23 during the transition from the hard state to the soft state. Combining the new radio and quasi-periodic oscillation studies, the model of total flux in the 2–100 keV energy range, the jet emission and the timing analysis during the state transition, we suggest a possible geometry and evolution for the （jet＋corona＋disk） system, like that proposed by Kalemci et al. based on enhanced lags and peak frequency shift during the transition.
文摘In this work,we investigate a possible conceptual link between torus-shaped black hole solutions of the vacuum gravitational field equations in(1+3)-dimensional general relativity and mitochondrial DNA(mtDNA).We propose that this analogy could serve as a framework for transferring insights and methodologies between the study of mtDNA and toroidal black hole geometries.By establishing this connection,we aim to provide novel perspectives that could contribute to advancements in both theoretical physics and molecular biology,offering new tools for understanding complex structures in these disciplines.
基金supported by the National Natural Science Foundation of China(Grant Nos.11875026,11875025,12035005,and2020YFC2201403)。
文摘A disformal rotating black-hole solution is a black-hole solution in quadratic degenerate higher-order scalar-tensor theories.It breaks the circular condition of spacetime different from the case of the usual Kerr spacetime.This study investigated the dynamic behaviors of the motion of timelike particles in such disformal black-hole spacetime with an extra deformation parameter.Results showed that the characteristics of the particle’s motion depend on the sign of the deformation parameter.For the positive deformation parameter,the motion is regular and orderly.For the negative one,as the deformation parameter changes,the motion of the particles undergoes a series of transitions between the chaotic motion and the regular motion and falls into the horizon or escapes to spatial infinity.This means that the dynamic behavior of timelike particles in the disformal Kerr black-hole spacetime with noncircularity becomes richer than that in the usual Kerr black-hole case.
文摘2025年,天文学研究在多个领域取得系统性进展,依托先进观测设备与深度数据分析,显著拓展了对宇宙多层次结构的认知。在银河系研究方面,郭守敬望远镜(Large Sky Area Multi-Object Fiber Spectroscopy Telescope,LAMOST)结合盖亚(Gaia)天文卫星的数据绘制出高精度银河系三维尘埃消光图,并揭示银河系英仙臂中存在直径超千秒差距的“超泡”结构。中国天眼(Five-hundred-meter Aperture Spherical radio Telescope,FAST)捕获了罕见的“脉冲星-氦星”双星系统,并首次揭示超高速中性氢云内部由湍流主导的复杂丝状网络。在太阳系探索中,嫦娥六号返回的月球背面样品分析,揭示了月幔的贫水特征、极端亏损的同位素组成以及南极-艾特肯盆地可能的撞击方向,为月球不对称演化提供了关键证据。宇宙学领域,暗能量光谱仪(Dark Energy Spectroscopic Instrument,DESI)巡天数据结合超新星观测数据,对暗能量状态方程是否随时间演化提出了约3σ显著性的观测指征。时域天文方面,“天关”卫星(Einstein Probe,EP)成功捕捉到高红移伽马暴的X射线前兆与新型弱喷流超新星暂现源。此外,盖亚天文卫星完成使命退役,留下宝贵遗产,欧几里得(Euclid)空间望远镜与薇拉·鲁宾天文台发布首批数据开启新时代,人类迎来第3位星际访客并完成立体观测,韦布空间望远镜(James Webb Space Telescope,JWST)直接成像年轻行星,以及事件视界望远镜(Event Horizon Telescope,EHT)揭示M87黑洞偏振结构的演化。这些成果再次印证了天文学领域地面与空间协同、多波段覆盖、时域监测与静态测绘并重这一综合探索范式的强大威力,并为理解从行星系统到宇宙尺度的形成与演化奠定了更加坚实的基础。
文摘声学黑洞(acoustic black hole,ABH)作为一种高效的弯曲波控制技术,在振动控制领域得到了广泛应用。针对传统单个声学黑洞特征尺寸与有效作用频率难以协调的问题,借鉴声子晶体设计思路,充分发挥声学黑洞振子高阻尼、多模态的优势,提出了一种局域共振型声学黑洞夹层板周期结构。通过结合能带曲线的带隙边缘模态分析与振子的谐振特性,系统阐明了弯曲波带隙的形成机制,并探究了单胞设计参数对带隙的影响规律。同时,通过增加配重和引入阻尼等优化策略,进一步拓宽了带隙范围,并实现了更低频带隙的有效打开。建立了声学黑洞夹层板周期结构的仿真和试验模型,仿真和试验结果表明,该结构在300 Hz范围内形成了显著的带隙特性,带隙中心频率最低至50 Hz以下,表现出良好的振动衰减效果。这一研究为浮筏结构的低频宽频减振设计提供了思路与技术路径。
