Jamming Mechanism Research Articles

Jamming mechanism on the scale-free network with heterogeneous node capacity

To understand how the jamming on real communication networks depends on node capacity, we study the traffic model with heterogeneous node capacity. In this model, each movable packet takes a biased random walk and the capacity of a node with degree k is given as C(k) ∼ k x with a tunable parameter x. Each packet disappears when it arrives at the preassigned target node. We analytically and numerically show that the transition from the free-flow phase to the jammed phase occurs when the balance between the packet generations and removals is broken. The balance breaking condition for the jamming is analytically determined by the competition between C(k) and the average number of packets on a node of degree k, m f (k), in the free-flow phase. Based on the analytic arguments, we find that there exist three different jamming patterns depending on C(k). The analytic conjectures for jamming patterns are verified by numerical simulations.

Large amplitude oscillatory shear rheology of three different shear-thickening particle dispersions

We present a large amplitude oscillatory shear rheology (LAOS) investigation of three different shear-thickening particle dispersions - fumed silica in polyethylene oxide (FLOC), fumed silica in polypropylene glycol (HydroC), and cornstarch in water (JAM). These systems shear-thicken by three different mechanisms - shear-induced formation of particle clusters flocculated by polymer bridging, hydrocluster formation, and jamming. The viscoelastic non-linearities of the three fluids were studied as a function of strain and strain-rate space through the use of Lissajous-Bowditch curves and local nonlinear viscoelastic moduli of an oscillatory shear cycle. The nonlinear behaviors of the three fluids were compared and contrasted to understand the nonlinear shear-thickening mechanism of each. Both HydroC and JAM dispersions were found to exhibit strong strain stiffening of the elastic moduli and strain thickening of the loss moduli behavior associated with possible hydrocluster formation and particle jamming. However, the FLOC dispersion, in contrast, showed strong strain softening and strain thinning behavior at large strain amplitudes associated with yielding of the microstructure. The expected thickening of the loss modulus of FLOC in LAOS with increasing strain was not observed even though viscosity of FLOC was found to shear-thicken in steady-shear measurements. This disagreement is likely due to very large strain amplitudes required for shear-thickening to occur by shear-induced polymer bridging mechanism. The hypothesis was confirmed through stress growth experiments. Conversely, the HydroC and JAM dispersions required relatively small applied strains for shear-thickening to occur by hydrocluster and jamming mechanism. The comparison of local intra-cycle nonlinearity through Lissajous-Bowditch plots and nonlinear viscoelastic parameters indicated that the elastic nonlinearities of all three systems are primarily driven by a strong dependence on the magnitude of the applied strain-rates within an oscillatory cycle rather than the amplitude of the applied strain. A close inspection of the LAOS data reveals strong differences in the viscoelastic nonlinearities of these three different shear-thickening dispersions which can be used to create a nonlinear rheological fingerprint for each and offers valuable new insights into the nonlinear dynamics associated with each of the shear-thickening mechanisms.

Vibration analysis for vehicle with Vacuum Packed Particles suspension

The paper concerns an effect of the damping force controlling a vehicle suspension system. The investigated vehicle suspension system consists of innovatory Vacuum Packed Particles controllable dampers which allow controlling the vehicle body vibration. The main objective of performed and presented in the paper studies is to determine properties of the Vacuum Packed Particles (VPP) damper and propose a preliminary control strategy. The control in the vehicle suspension system can be realized by controlling the underpressure resulting in various jamming mechanisms in the granular core. Some algorithms of vibration control are also proposed and discussed.

Inertially excited beam vibrations damped by Vacuum Packed Particles

The dynamics of an inertially excited steel cantilever beam encapsulated in a hermetic sleeve filled with polypropylene grains is investigated experimentally and theoretically. An electric motor rotating an unbalanced mass is attached at the end of the beam to generate forced vibrations of the system. Changing the underpressure in the sleeve results in changes of the stiffness and dissipative properties of the composite structure, which allow one to control the resonant characteristics of the system. Is is shown that the amplitude of vibrations can be reduced in this way. This innovative semi-active method of vibration damping is based on the jamming mechanism of the granules, and proved to be efficient in the reduction of the free vibrations of the beam, which was studied in the authors’ latest paper. In the present work, it is confirmed that the classical Bernoulli–Euler beam model with Kelvin–Voigt damping provides a satisfactory explanation of the observed relation between the vibrations amplitude and underpressure.

PACKET-HIDING METHODS FOR PREVENTING SELECTIVE JAMMING ATTACKS

In this paper we develop an cryptography where efficient data packet are transferred in an wireless medium. The vulnerability of an wireless medium for its intentional interface attacks for its behaviour as its an open nature leads to intentional interference attacks known as jamming. Making use of these intentional interference attacks we perform lauchpad for mounting the Denial-of-Service attacks on these open wireless networks. As jamming is an external threat model used commonly over an wireless mediums which effects adversely to the protocol specifications which lead to low-effort jamming attacks in an network secreat which is very difficult to mount the error and detect the failure of network. For these problems we address selective jamming attacks in wireless medium network. We create a sensor that has four components. First historic model where detecting known protocol sequence is developed for probabilistic modelSecond is probabilistic model where sizes of packets and inter-packet timing of different packet types are arranged. Third is victim network to produce known sequences for historic analyzer using active jamming mechanism. Lastly online classifier which makes packet type classification decisions For a short period of time and selective targeting messages of high importance are active in these attacks which effect adversely. We evolve an advantage of selective jamming with respect to network adversary efforts and performance degradation is done by case studies such as on routing and attacks on TCP. These selective jamming attacks can be launched by means of performance in real-time packet classification at physical layer of TCP. To overcome these attacks we develop three schemas which prevent real time packet classification by combining cryptographic primitives with physical layer attributesToovercome these attacks we develop three schemas that prevent real-time packet classification by using combined cryptographic primitives with its physical layer attributes.

Analysis of Theory and Model of Background Magnetic Field of High-Spinning Projectile

At present, methods of the navigation and the attitude measurements of projectile utilizing the magnetic fields are facing the interference from the BMF (background magnetic field). The principle and mathematical model of the BMF for the spinning projectile are been researched to realize the high accuracy measurement of the geomagnetic field on projectile. The composition and jamming mechanism of the projectile's BMF are derived with the Faraday electromagnetic induction theory. High precision compensation model of the geomagnetic measurement is established by synthesizing the magnetic sensor error model. Based on the idea of the error transfer, the attitude measuring errors caused by the BMF are analyzed and the error calculation formulas are given. On this basis, numerical simulation is conducted combining with projectile's flight rules. The results show that the influence of attitude angle measuring precisions caused by the background interference magnetic field are much bigger than the errors caused by the sensor noise and the established compensation model has obvious effect. Besides, the effective BMF compensation of geomagnetic measurements on the projectile must be conducted if the attitude angle measurement error is in requirements within ±1 °.

Design and Implementation of Spectrally-Encoded Spread-Time CDMA Transceiver

In this paper, we present and discuss the physical implementation and testing of a Spectrally-Encoded Spread-Time Code Devision Multiple Access (SE/ST-CDMA) transceiver. The proposed design is suitable for multiple-access and anti jamming wireless communication systems. The design and implementation takes into account the ability to automatically detect and mitigate tone jammers by altering the corresponding Gold sequence codes assigned uniquely to each user and setting the corresponding code's chip to zero. A simple real-time anti jamming mechanism capable of dealing with frequency hopping jammers is also proposed. The simulation results are provided in terms of Bit Error Rate (BER) versus Signal to Noise Ratio (SNR) in one case and the number of multi tone jammers in another, both conditioned on the number of users. Finally, the experimental and simulation results are compared and we observe that they are in a very good agreement.

Transient response analysis of a steel beam with vacuum packed particles

In this paper the method of semi-active damping of vibrations is presented. Free vibrations of a cantilever steel beam encapsulated in a sleeve, filled with the granular material are investigated. Various values of the partial vacuum generated in the granular structure allow to control the global dissipative properties of the discussed system. The loose grains encapsulated in the hermetic, polyvinyl chloride (PVC) envelope transform into a rigid, viscoplastic body as the jamming mechanism occurs when the underpressure is generated. Such phenomenon enables original strategies for semi-active damping. A detailed discussion related to the experimental results concerning the amplitude of vibration, damping, stiffness, and frequency of the continuous granular beam system is provided. The simplified Finite Element Model succeeded in describing the dynamic response of the structure.

Long-range cargo transport on crowded microtubules: The motor jamming mechanism

The hopping model for cargo transport by molecular motors introduced in Goldman and Sena (2009), Goldman (2010) is extended here in order to incorporate the movement of cargo–motor complexes (C–MC). Hopping processes in this context express the possibility for cargo to be exchanged between neighboring motors at a microtubule where the transport takes place. Jamming of motors is essential for cargos to execute long-range movement in this way. Results from computer simulations accompanied by a mean-field analysis of the extended model confirm our previous analytical results and suggests that an interplay between cargo hopping and the movement of the C–MC’s would control the efficiency of cargo transfer and cargo delivery in these model systems.

隐身对电视导引头的干扰效应研究

The stealthy jamming effect on a TV homing seeker is investigated by flight test in which the seeker is loaded on an unmanned airship.The basic law of stealthy jamming effect on the performance of the TV homing seeker is discovered and explained.The results are referential for the study of stealthy jamming mechanism and the anti-jamming design of imaging seekers.

Detection of jamming attacks in 802.11b wireless networks

The work in this paper is about to detect and classify jamming attacks in 802.11b wireless networks. The number of jamming detection and classification techniques has been proposed in the literature. Majority of them model individual parameters like signal strength, carrier sensing time, and packet delivery ratio to detect the presence of a jammer and to classify the jamming attacks. The demonstrated results by the authors are often overlapping as most of the jamming regions are closely marked, and they do not help to clearly distinguish different jamming mechanisms. We investigate a multi-modal scheme that models different jamming attacks by discovering the correlation between three parameters: packet delivery ratio, signal strength variation, and pulse width of the received signal. Based on that, profiles are generated in normal scenarios during training sessions which are then compared with test sessions to detect and classify jamming attacks. Our proposed model helps in clearly differentiating the jammed regions for various types of jamming attacks. In addition, it is equally effective for both the protocol-aware and protocol-unaware jammers. The reported results are not based on simulations, but a test-bed was established to experiment real scenarios demonstrating significant enhancements in previous results reported in the literature.

Reliable and Secure Cooperative Communication for Wireless Sensor Networks Making Use of Cooperative Jamming with Physical Layer Security

Interference is generally considered as the redundant and unwanted occurrence in wireless communication. This research work proposes a novel cooperative jamming mechanism for scalable networks like wireless sensor networks which makes use of friendly interference to confuse the eavesdropper and increase its uncertainty about the source message. The communication link is built with the help of Information theoretic source and channel coding mechanisms. The whole idea is to make use of normally inactive relay nodes in the selective Decode and Forward cooperative communication and let them work as cooperative jamming sources to increase the equivocation of the eavesdropper. In this work, eavesdropper's equivocation is compared with the main channel in terms of mutual information and secrecy capacity.

Hybrid relaying and jamming for wireless physical layer security based on cooperative beamforming

To improve the information-theoretic security of two-way wireless cooperative communication systems, we propose in this study a hybrid relaying and jamming mechanism based on multi-node cooperative beamforming to enhance the security of the physical layer transmission of information. The basic concept is that in the cooperative transmission phase, some intermediate nodes adopt distributed beamforming to help the transmitter send messages to legitimate users and simultaneously others jam the eavesdropper, which can significantly improve the security performance of the system in the broadcast phase. Two different cooperative beamforming schemes are proposed with and without the instantaneous channel state information (CSI) of the eavesdropper. We show that optimizing both the schemes requires the mathematical solving of one or a series of second-order convex cone programming (SOCP) problems, which can be executed by efficiently using the interior point method. Simulation and comparisons show that our proposed hybrid relaying, jamming mechanism and beamforming approaches significantly increase the security sum rate of the two source terminals and outperform both the relays-only and jammers-only mechanisms when the number of intermediate nodes is relatively large.

CO2-triggered liquid–solid switching through a jamming mechanism

The concept of jamming is introduced into a CO2-responsive microgel suspension. The particle size of the microgel changes with the pH of the solvent and the rheological properties of the suspension are responsive to the triggering of CO2. At a certain concentration of the microgel, the microgel suspension transforms from a liquid into a solid-like material as CO2 is bubbled into it, and it returns to a liquid after the CO2 is blown away with N2. The CO2-triggered jamming is rapid and reversible, leading to many interesting applications of the system.

A Novel Layer Jamming Mechanism With Tunable Stiffness Capability for Minimally Invasive Surgery

This paper presents a novel “layer jamming” mechanism that can achieve variable stiffness. The layer jamming mechanism exploits the friction present between layers of thin material, which can be controlled by a confining pressure. Due to the mechanism's hollow geometry, compact size, and light weight, it is well suited for various minimally invasive surgery applications, where stiffness change is required. This paper describes the concept, the mathematical model, and a tubular snake-like manipulator prototype. Various characteristics of layer jamming, such as stiffness and yield strength, are studied both theoretically and experimentally.

1A2-B13 真空硬化性を有する腹腔内膨脹型リトラクタ(医療ロボティクス・メカトロニクス(2))

1A2-B13 真空硬化性を有する腹腔内膨脹型リトラクタ(医療ロボティクス・メカトロニクス(2))

激光对红外热成像设备自动增益控制电路的干扰效果

Based on the analysis of the working principle of automatic gain control (AGC) circuit, the mechanism of laser jamming on AGC circuit is discussed, and the experiment of laser jamming on the AGC circuit of an infrared thermal imaging device is carried out. An analysis method which uses the change of regional gray scale to test the gain of AGC circuit is then proposed. Finally, a quantitative analysis is conducted on the experiment data, and the result indicates that, the persistent effective interference of laser on AGC circuit of infrared thermal imaging device can be realized, on condition that the pulse period of interference laser is less than the adjustment time of automatic gain.

A Basic Study on the Jamming Mechanisms and Characteristics against GPS/GNSS Based on Navigation Warfare

It has been recognized that the risk from the vulnerability of GPS can lead to the extreme damage in the infrastructure of the civil and military in recent years. As an example, the intentional interference to GPS signal, named GPS jamming, was really performed to misguide GPS guided weapons during Iraq war in 2003, and the fact has also followed by the serious issues on GPS in civilian community. In the modernized military society, the navigation warfare(NAVWAR) based on the GPS jamming has been emerged and introduced as a military operation. The intentional interference to the future global navigation satellite system(GNSS) involving GPS must be also an important issue to civilian users in near future. This study is focused on the fundamental research prior to the research on "Potential principle of NAVWAR" under NAVWAR of the future warfare. In this paper, we would study on the investigation of NAVWAR based on electronic warfare(EW) and analyze characteristics of the jamming against GNSS's receivers. Then the general mechanism on GNSS jamming is proposed.

Career concerns incentives: An experimental test

Holmström’s [Holmström, B., 1982/1999. Managerial incentive problems: a dynamic perspective. Review of Economic Studies 66, 169–182. Originally published in: Essays in Economics and Management in Honour of Lars Wahlbeck, Helsinki] career concerns model has become a workhorse for analyzing agency issues in many fields. The underlying signal jamming argument requires players to use information in a Bayesian way, which is difficult to directly test with field data: typically little is known about the information that individuals base their decisions on. Our laboratory experiment provides prima facie evidence: (i) the signal jamming mechanism successfully creates incentives on the labor supply side; (ii) decision errors take time to decrease; (iii) while subjects’ average beliefs are remarkably consistent with play, a mild winner’s curse arises on the labor demand side.

Locking, Jamming, and Ratchet Mechanisms of Sliding Surgical Knots Topologically Revisited

The geometry of lockable, ratchet, or jamming sliding surgical knots was assessed to enhance practical and topological understanding of knots among surgeons. Using a database of more than 100 surgical knots, 29 knots that reportedly feature locking, ratchet, or jamming mechanisms were topologically assessed for their ability to lock antegradely or retrogradely, to lock by assuming their flat geometry, or to jam. Eighteen of the 29 investigated surgical knots have previously been mistakenly categorized. Topologically, the concept of a true ratchet knot is a fallacy. Surgical knots may be consistently classified on the basis of precise and detailed definition of various anti-backsliding geometrical characteristics of knots.