Lateral Pulse Research Articles

Temporal and lateral electron pulse compression by a compact spherical electrostatic capacitor

A novel solution for high intensity electron pulse compression in both space and time is proposed in this paper. Based on the unique properties of the central-force electrostatic field of a spherical electrostatic capacitor, the newly developed α-Spherical Deflector Analyzer (α-SDA) with 2π total deflection is utilized for the practical realization of femtosecond electron pulse compression. The mirror symmetry of the system at π deflection causes not only the cancellation of the geometrical and chromatic aberrations at 2π, but also leads to aberration-free time reversal of the electron pulse in the exit plane. As a consequence, the time-divergent electrons at the input are transformed to a time-convergent pulse at the output. In the symmetric case with the first time compression exactly at π, the shortest electron pulse behind the α-SDA analyzer is a mirror symmetric to the original electron pulse at the photocathode. It results in extremely short final electron pulses that are limited only by the duration of the laser pulse, the emittance of the electron bunch, and by imperfections of the real system.

Range Prediction and Trajectory Correction of Long Range Rocket with Attitude Stabilization

The dispersion of long range rocket is significantly suppressed by the attitude stabilization in the boost phase. However, the attitude stabilization system cannot govern the propellant impulse error and mass error, which induces large dispersion in the longitudinal direction. Therefore, it is necessary to conduct range correction in the post-boost phase of flight trajectory. A range prediction method based on the elliptic ballistic theory is proposed in this paper. Elliptic ballistic equations and range estimation equations are derived and the modified range prediction method with correction factor is presented. It is verified that the proposed method can predict the residual flight range accurately. After that, the lateral pulse jets control is presented and utilized to correct the trajectory and eliminate the range error. A unique control law is reported that combines elliptic ballistic theory and control mode for lateral pulse jets. The impact point is directly controlled and rocket dispersion in the longitudinal direction is efficiently reduced.

Design of Missile Autopilot with Aerodynamic Lift and Reaction Jets Based on Auto Disturbance Rejection Controller

First a new autopilot design model is presented for the interceptor missile with the blended aerodynamic lift and reaction jet. The reaction jet can improve the response speed, but the structure of control system becomes more complex. Therefore how to design control strategy properly is an urgent problem. Second, considering the discrete property of the lateral pulse jet thrusters and the continuous property of the aerodynamic fins, a kind of ADRC (active disturbance rejection control) autopilot system was designed for the aerodynamic lift/reaction jet missile. Finally, through a testing in the simulation of MATLAB, it is shown that, due to the sufficient utilization of the reaction jet, there is a significant improvement in the fast response and robust performance of the proposed controller. It is applicable to design the autopilot of aerodynamic lift and reaction jet blended missile.

Spatial Distribution of Nutrient Limitation in the Danube River Floodplain in Relation to Hydrological Connectivity

In this paper, we describe the influence of flooding on nutrient conditions and phytoplankton Chl-a concentrations in a hydrologically dynamic Danube floodplain in North–Eastern Croatia. Based on hydrological typology, the connectivity gradient extends from the main river stream (Eupotamal) to the backwater channels and side-arms (Parapotamal) to the edge of the floodplain (Paleopotamal). A spatial gradient of phytoplankton Chl-a occurred during low water levels, while uniformity of Chl-a across wetland habitats was observed during high water levels. Nutrient enrichment assays indicated that inorganic nutrients in Eupotamal waters (N/P ratio 16–22) could support a higher growth rate of the assay alga Chlorella kessleri, while potential N limitation was found in Parapotamal and Paleopotamal waters (both with N/P ratios < 14). Spatial expansion of N limitation toward the main river was observed as inundation continued. Lateral flood pulse connectivity along with the duration of inundation period affects the input and the retention of nutrients, especially of nitrogen. Understanding of the relationship between spatial (location of the floodplain waterbodies regarding the river) and temporal (hydrological connectivity between the river and its floodplain) dimensions contribute to the importance of healthy floodplains for the maintenance of water quality and environmental conditions in the Danube River.

Elastodynamic analysis of a thin layer bonded on a visco-elastic medium under combined in-plane and lateral pulse loads

An analytic solution of a thin layer bonded on a visco-elastic medium under the action of in-plane and lateral pulse loads is presented. The analysis is based on double integral transforms with respect to space and time. Representative examples are studied and discussed to determine the influence of the (a) damping and elastic coefficients of visco-elastic medium, and (b) in-plane compression and stretching of the thin layer on wave propagation.

Optimal proton acceleration from lateral limited foil sections and different laser pulse durations at relativistic intensity

The proton acceleration from a thin foil irradiated by a laser pulse at relativistic intensities is a process highly dependent on the electron dynamic at the rear side of the foil. By reducing the lateral size of the laser irradiated foil the hot electrons are confined in a small volume leading to an enhancement of both the maximum proton energy and the conversion efficiency in the target normal sheath acceleration regime. In this paper we demonstrate that an optimal lateral size of the target can be found. While a smaller target surface leads to a better hot electron confinement and enhances the Debye sheath accelerating the protons, it also leads to an increase of preplasma formation due to limited laser contrast available experimentally and hence to a decrease of the proton acceleration. The experimentally found optimum is in good agreement with analytic theory and 2D particle in cell simulations. In addition, the maximum proton energy as a function of pulse duration has been investigated. The experimental results fit to an analytical model.

An Entirely Subcutaneous Implantable Cardioverter–Defibrillator

Background Implantable cardioverter–defibrillators (ICDs) prevent sudden death from cardiac causes in selected patients but require the use of transvenous lead systems. To eliminate the need for venous access, we designed and tested an entirely subcutaneous ICD system. Methods First, we conducted two short-term clinical trials to identify a suitable device configuration and assess energy requirements. We evaluated four subcutaneous ICD configurations in 78 patients who were candidates for ICD implantation and subsequently tested the best configuration in 49 additional patients to determine the subcutaneous defibrillation threshold in comparison with that of the standard transvenous ICD. Then we evaluated the long-term use of subcutaneous ICDs in a pilot study, involving 6 patients, which was followed by a trial involving 55 patients. Results The best device configuration consisted of a parasternal electrode and a left lateral thoracic pulse generator. This configuration was as effective as a transvenous I...

Emergency department right atrial pressure and intravascular volume estimation using right ventricular tissue Doppler bedside ultrasonography

Abstract A 41 year old woman with a history of colon cancer metastatic to her lung and liver, presented to the emergency department severely dehydrated. Bedside ultrasonography revealed a tumor mass in her proximal inferior vena cava at the junction of the right atrium obstructing the ability to assess her volume status with inferior vena cava inspiratory collapse. Bedside emergency department cardiac tissue Doppler ultrasonography of the lateral right ventricle and pulse Doppler ultrasonography of the tricuspid valve was used to estimate her right atrial pressure and intravascular volume status.

Dynamic response of pre-stressed fibre metal laminate (FML) circular cylindrical shells subjected to lateral pressure pulse loads

Dynamic response of fiber metal laminate cylindrical shells subjected to initial combined axial load and internal pressure were studied in this paper. First order shear deformation theory (FSDT) was utilized in the shell’s equilibrium equations and strain–displacement relations were based on Love’s first approximation theory. Equilibrium equations for buckling, free and forced vibration problems of the shell were solved using Galerkin method. The influences of FML parameters such as material properties lay up, Metal Volume Fraction (MVF), fiber orientation and initial stresses on dynamic response were investigated. The results were indicated that the FML lay up, has a significant effect on natural frequencies as well as transient dynamic response with respect to various values of MVF as well as pre-stress.

Temporary fragmentation of a marginal lake and its effects on zooplankton community structure and organization

A river lateral lake (Coqueiral Lake marginal to Paranapanema River in its mouth zone into Jurumirim Reservoir, São Paulo, Brazil) presented fragmentation into four small isolated bodies of water during a prolonged drought period, disrupting the link with the river. The aim of this work was to compare the temporal modifications on zooplankton community structure (total abundance, species richness, and diversity) in the four water bodies. Zooplankton samplings and abiotic factor measurements were made in two periods--during isolation phase of the lake in relation to river and after re-establishment of hydrologic connectivity. A concentration effect on zooplankton abundance was recorded with drought progression, but without significant modifications in species richness and diversity. When the river inundation pulse occurred, a reduction in total zooplankton density was observed due to the dilution effect and a significant increase in species richness and diversity was recorded. Lateral water influx from the river to the lacustrine environment acts as a temporary disturbance factor on the zooplankton community structure. Zooplankton species composition presented some modifications between the two periods. Zooplankton organism drift in water from the river to the lake, removal of individuals from the aquatic macrophytes, and eclosion of resting eggs from sediment are probable factors that can increase zooplankton species richness immediately after lateral pulse inundation with water by the river.

Predictive Guidance of a Projectile for Hit-to-Kill Interception

In this paper, a predictive guidance algorithm is developed for a spin-stabilized hit-to-kill guided projectile. The projectile is used as an interceptor against rockets, mortar, and artillery. Guidance is based on a new rapid trajectory prediction algorithm for projectiles fired at high quadrant elevations. The interceptor uses lateral pulse jets located near the mass center for control. High spin rates require additional guidance compensation for gyroscopic effects when compared to a fin-stabilized projectile. The probability of kill (PK) is evaluated based on typical gun pointing errors, roll angle uncertainty, and target acquisition errors. It is shown that guided interceptors can achieve a 90% PK by using as few as 5 projectiles in the presence of roll, gun pointing, and target errors. It is also shown that, despite sensitivity to errors in gun pointing and target errors, the predictive guidance system is able to achieve an acceptable PK. For a spin-stabilized interceptor, estimated-roll orientation errors may become large. Simulations are performed for errors in the estimated roll, and it is demonstrated that roll does not need to be precisely known for a successful interception.

O.012 A physical model of occlusive hydrocephalus

Cerebrospinal fluid (CSF) pulsations result from change of blood volume in the closed craniospinal cavity. We used cine phase contrast MR analysis to determine whether spinal CSF pulsations result from spinal vascular pulsations or intracranial subarachnoid pulsations, whether intracranial CSF pulsations result from intracranial large arteries pulsations or cerebrovascular bed changes. We performed a quantified physiological mapping of CSF velocity waveforms along the craniospinal axis. Thirty-six volunteers participated in the study. MR acquisitions were obtained at the intracranial level, the upper, midcervical, cervicothoracic, mid thoracic, and/or the thoracolumbar levels. The temporal velocity information were plotted as wave form and key temporal parameters were determined and analyzed; intervals from the R wave to the onset of CSF systole, to CSF systolic peak, to the end of systole, as well as duration of systole. Three kinds of dynamic channels could be differentiated along the spinal axis, the lateral, medioventral and mediodorsal channels. Lateral spinal CSF pulse waves show significant craniocaudal propagation. No such significant progression was detected through the medial channels along the spine. Through the medial channels, a cephalic progression was observed from the upper cervical level to the intracranial level. At the craniocervical junction, mediodorsal CSF systole appeared the earliest one whereas in the anterior intracranial basal cistern, CSF systole appeared delayed. In conclusion, spinal CSF pulsations seem to result mainly from intracranial pulsations in the lateral channels, whereas local vascular pulsations could modify CSF pulse wave mainly in the medial channels. At the craniocervical junction, our results suggest that blood volume change in the richly vascularised cerebellar tonsils is the main initiating factor of CSF systole; and that spinal vascular pulsations could be considered as an additional early and variable CSF pump.

Bounding the Output Error in a Buck Power Converter Using Perturbation Theory

We show the main results obtained when applying the average theory to Zero Average Dynamic control technique in a buck power converter with pulse‐width modulation (PWM). In particular, we have obtained the bound values for output error and sliding surface. The PWM with centered and lateral pulse configurations were analyzed. The analytical results have confirmed the numerical and experimental results already obtained in previous publications. Moreover, through an important lemma, we have generalized the theory for any stable second‐order system with relative degree 2, using properties related to transformations and stability of linear systems.

EXACT FORMULAS FOR THE LATERAL ELECTROMAGNETIC PULSES FROM A HORIZONTAL ELECTRIC DIPOLE ON THE BOUNDARY BETWEEN A ISOTROPIC MEDIUM AND ONE-DIMENSIONALLY ANISOTROPIC MEDIUM

In this paper, the exact formulas are derived for the timedomain electromagnetic field generated by a delta-function current in a horizontal electric dipole located on the planar boundary between a homogeneous isotropic medium and one-dimensionally anisotropic medium. Similar to the isotropic case, the amplitude of the tangential pulsed electric field along the boundary is 1/ρ2, which is characteristic of the surface-wave or lateral pulse. The tangential electric field consists of a delta-function pulse travelling in Region 2 (anisotropic medium), a oppositely directed delta-function travelling in Region 1 (isotropic medium), and a final static electric field due to the charges left on the dipole. It is seen that the pulsed electromagnetic field components consist of the first and second pulsed in the two regions with different velocities.

ICARUS: imaging pulse compression algorithm through remapping of ultrasound

In this work we tackle the problem of applying to echographic imaging those synthetic aperture focusing techniques (SAFT) in the frequency domain commonly used in the field of synthetic aperture radars (SAR). The aim of this research is to improve echographic image resolution by using chirp transmit signals, and by performing pulse compression in both dimensions (depth and lateral). The curved geometry present in the unfocused radio-frequency (RF) ultrasonic image is the main cause of inaccuracy in the direct application of frequency domain SAFT algorithms to echographic imaging. The focusing method proposed in this work, after pulse compression in the depth dimension, performs lateral focusing in the mixed depth-lateral spatial frequency domain by means of a depth variant remapping followed by lateral pulse compression. This technique has the advantage of providing a resolution that is uniform in nonfrequency selective attenuation media, and improved with respect to conventional time domain SAFT, without requiring the acquisition and processing of channel data necessary for the most advanced synthetic transmit aperture techniques. Therefore, the presented method is suitable for easy real-time implementation with current generation hardware.

EXACT FORMULAS FOR THE LATERAL ELECTROMAGNETIC PULSES GENERATED BY A HORIZONTAL ELECTRIC DIPOLE IN THE INTERFACE OF TWO DIELECTRICS

The Sommerfeld integrals for the electromagnetic field due to a delta-function current in a horizontal electric dipole located on the planar boundary between air and a homogeneous dielectric are examined in detail. Similar to the case of the vertical dipole, the tangential electric fields consist of a delta-function pulse travelling in the air with the velocity c, the oppositely directed delta-function pulse travelling in the dielectric with the velocity c/ 1/2 for the component Eρ and the velocity c 1/2 for the component Eφ, and the final static electric fields due to the charge left on the dipole. The appearance of the vertical magnetic field is similar to that of the tangential electric field. It is pointed out that the amplitude of the pulsed field along the boundary is 1/ρ2, which is characteristic of the surface-wave or lateral pulse.

Model Predictive Lateral Pulse Jet Control of an Atmospheric Rocket

Uncontrolled direct fire atmospheric rockets exhibit high impact point dispersion, even at relatively short range, and, as such, have been employed as area weapons on the battlefield. To reduce the dispersion of a direct fire rocket, the use of a small number of short-duration lateral pulses acting as a control mechanism is investigated. A unique control law is reported that combines model predictive control and linear projectile theory for lateral pulse jet control of an atmospheric rocket. The impact point in the target plane is directly controlled. Through simulation, this model predictive flight control law is shown to efficiently reduce direct fire rocket dispersion. A parametric trade study on an example rocket configuration is reported that details the effect of the number and amplitude of individual pulse jets, as well as the effect of the flight control system computation cycle time.

Prediction of swerving motion of a dual-spin projectile with lateral pulse jets in atmospheric flight

Using the linear theory for a dual-spin projectile in atmospheric flight, closed form expressions are obtained for swerving motion under the action of lateral pulse jets. Trajectory results generated by the linear theory equations and a fully nonlinear seven degree-of-freedom dual spin projectile model agree favorably. The analytic solution provides a relatively straightforward and computationally efficient means of trajectory estimation which is useful within smart weapon flight control systems. In order to accurately predict the impact point using the analytic solution, the dual-spin projectile linear model must be updated periodically. Terminal impact point prediction degrades rapidly as the linear model update interval is increased beyond a critical value. Control authority, as defined by the change in impact location due to a pulse jet firing, steadily decreases as a function of projectile down range position.

SPATIALLY DEPENDENT AMPLIFICATION OF AN EXCITONIC BOSE-EINSTEIN CONDENSATE IN Cu2O

Experimental results are presented on the spatial dependence of amplification of a travelling Bose-Einstein condensate of excitons in Cu 2 O . The exciton condensate is created at T = 1.8 K by high intensity pulsed laser illumination (λ = 532 nm). Amplification of the moving condensate is triggered by the local, time-delayed injection of thermal excitons created by a lateral laser pulse tuned at the 1S orthoexciton resonance (λ = 609.48 nm), perpendicular to the path of the condensate. The amplification factor depends on the trigger time of the lateral laser pulse and is related to the stimulated scattering into the condensate of non-condensed excitons present in the crystal volume. A spatial correlation is also observed between the amplification factor and the optical attenuation of the lateral laser radiation induced by the passing condensate.

Response of long rods to moving lateral pressure pulse: numerical evaluation in DYNA3D

In this paper a convenient method to study the response of long rod projectiles subjected to a traversing lateral load pulse is presented. This problem mimics the lateral interaction of a yawed projectile with an oblique plate target. There are certain numerical difficulties in using Lagrangian wavecodes directly to compute the lateral penetration interaction behavior associated with erosion of elements, which leads to apparent numerical instabilities and large scale lateral surface erosion of the penetrator. It is known from experiments that for low yaw angles, lateral erosion is absent. In such cases, we show that the plate target can be replaced by a loading pulse, which moves relative to the rod at a speed completely determined from the geometry. In addition to avoiding problems associated with erosion algorithm, this method results in a tremendous reduction in computation time due to absence of the target grid. Using this method, rod deflection is successfully computed, and fracture locations are identified.