Discrete Pulses Research Articles

Manifestations of miocene acid intrusive magmatism on the southern slope of the Greater Caucasus: First evidence from isotope geochronology

New isotope-geochronological data (K-Ar, Rb-Sr) provide tight geochronological constraints on the history of Late Cenozoic magmatism on the southern slope of the Greater Caucasus. Several previously unknown, rhyodacite intrusive bodies with an emplacement age of 6.9 ± 0.3 Ma (Late Miocene) are reported from the Kakheti-Lechkhumi regional fault zone in the Kvemo Svaneti-Racha area. Therefore, a pulse of acid intrusive magmatism took place in a period previously considered amagmatic in the Greater Caucasus. The petrological, geochemical, and isotopic data suggest that these rhyodacites are produced by crystallization differentiation of mantle-derived magmas, which are similar in composition to Miocene mafic lavas that erupted a few hundred thousand years later in the adjacent Central Georgian neovolcanic area. The presented results allow the conclusion that the volcanic activity within the Central Georgian neovolcanic area occurred at 7.2–6.0 Ma in two discrete pulses: (1) the emplacement of acid intrusions and (2) the eruption of trachybasaltic lavas. The emplacement of rhyodacite intrusions in the Kvemo Svaneti-Racha area marked the first pulse of young magmatism on the southern slope of the Main Caucasus range and simultaneously represented the second magmatic pulse (after granitoid magmatism of the Caucasian Mineral Waters region) within the entire Greater Caucasus.

Power-Scalable, Sub-Nanosecond Mode-Locked Erbium-Doped Fiber Laser Based on a Frequency-Shifted-Feedback Ring Cavity Incorporating a Narrow Bandpass Filter

We present an all-fiberized power-scalable, sub-nanosecond mode-locked laser based on a frequency-shifted-feedback ring cavity comprised of an erbium-doped fiber, a downshifting acousto-optic modulator (AOM), and a bandpass filter (BPF). With the aid of the frequency-shifted feedback mechanism provided by the AOM and the narrow filter bandwidth of 0.45 nm, we generate self-starting, mode-locked optical pulses with a spectral bandwidth of ~0.098 nm and a pulsewidth of 432 to 536 ps. In particular, the output power is readily scalable with pump power while keeping the temporal shape and spectral bandwidth. This is obtained via the consolidation of bound pulse modes circulating at the fundamental repetition rate of the cavity. In fact, the consolidated pulses form a single-entity envelope of asymmetric Gaussian shape where no discrete internal pulses are perceived. This result highlights that the inclusion of the narrow BPF into the cavity is crucial to achieving the consolidated pulses.

Evolution of a Holocene, mixed-process, forced regressive shoreline: The Mitchell River delta, Queensland, Australia

Subtle changes in local accommodation, sediment flux, and wave, tide and fluvial processes can result in significant changes in the depositional style and architecture of coastal depositional systems. The detailed study of modern mixed-process depositional systems provides an opportunity to examine how such forcing factors affect shoreline evolution. The Mitchell River delta is a morphologically complex system that has prograded during a Holocene forced regression in a low accommodation epicontinental seaway. Relatively minor anthropogenic modification of the delta has occurred during the last 200 yr such that the considerable temporal and spatial variability of a mixed-influence coastal system can be observed in a de facto natural state. Of special interest is the link between preserved delta morphology and process change. A recent coastal process classification system was applied to the delta using desktop mapping and field ground-truthing and sedimentological analyses. The distribution and extent of 3400 wave-, tide- and fluvial-derived depositional elements were mapped across over 500 km2. These elements were grouped into 7 distinct progradational Element Complex Sets (ECS), defined by major reorganisations of the shoreline. The process classification of the overall delta system is tide dominated, fluvial influenced, wave affected (Tfw); however, the delta has evolved through three geometrically discrete pulses of delta progradation. The delta has evolved from (i) a symmetrical, wave-dominated, fluvial-influenced, tide-affected (Wft) system (early Holocene), to (ii) a rapidly prograding asymmetrical, tide-dominated, fluvial-influenced, wave-affected (Tfw) system (mid-Holocene), to (iii) an asymmetrical, tide-dominated, wave-influenced, fluvial-affected (Twf) system (at the modern shoreline). When the delta commenced progradation (6 ka BP), high accommodation-to-sediment-supply ratio (A/S) resulted in the deposition of wave formed depositional elements. As sea level fell and effective precipitation (EP) increased, reduced A/S resulted in more rapid progradation of tidal deposits until approximately 2 ka BP. The subsequent decrease in EP (and increased A/S) resulted in reduced rates of delta progradation and prompted multiple channel avulsions. Limited evidence suggests increased progradation rates at the modern channel mouth since 0.2 ka BP, which may be linked to increased sediment supply from anthropogenic catchment disturbance.

Fast gates for ion traps by splitting laser pulses

We present a fast phase gate scheme that is experimentally achievable and has an operation time more than two orders of magnitude faster than current experimental schemes for low numbers of pulses. The gate time improves with the number of pulses following an inverse power law. Unlike implemented schemes which excite precise motional sidebands, thus limiting the gate timescale, our scheme excites multiple motional states using discrete ultra-fast pulses. We use beam-splitters to divide pulses into smaller components to overcome limitations due to the finite laser pulse repetition rate. This provides gate times faster than proposed theoretical schemes when we optimize a practical setup.

Comparison of Transmitted Pulse Trains Predicted by Duhamel's Superposition Theorem and Direct Pulse Simulation in a 3-D Discrete Ordinates System

The transient response of transmittance in a scattering-absorbing cubic medium subjected to a diffuse square pulse train is predicted by two different methods, i.e., Duhamel's superposition theorem and the direct pulse simulation, in a 3-D discrete ordinates system. The computed results for each solution method are compared and are shown for different discrete approximations, optical thicknesses, scattering albedos, pulse widths, and pulse train intervals between two successive pulses. The computational time consumed for the direct pulse simulation is also presented. It is found that Duhamel's superposition theorem provides better accuracy and computational efficiency than the direct pulse simulation, because Duhamel's superposition theorem needs only one solution exposed to a single diffuse unit step square pulse for different problems subjected to a square pulse train with various pulse widths and pulse train intervals, whereas the direct pulse simulation is time-consuming and subject to increased numerical errors because of error accumulation.

Protection of Neuronal Diversity at the Expense of Neuronal Numbers during Nutrient Restriction in the Drosophila Visual System

SummarySystemic signals provided by nutrients and hormones are known to coordinate the growth and proliferation of different organs during development. However, within the brain, it is unclear how these signals influence neural progenitor divisions and neuronal diversity. Here, in the Drosophila visual system, we identify two developmental phases with different sensitivities to dietary nutrients. During early larval stages, nutrients regulate the size of the neural progenitor pool via insulin/PI3K/TOR-dependent symmetric neuroepithelial divisions. During late larval stages, neural proliferation becomes insensitive to dietary nutrients, and the steroid hormone ecdysone acts on Delta/Notch signaling to promote the switch from symmetric mitoses to asymmetric neurogenic divisions. This mechanism accounts for why sustained undernourishment during visual system development restricts neuronal numbers while protecting neuronal diversity. These studies reveal an adaptive mechanism that helps to retain a functional visual system over a range of different brain sizes in the face of suboptimal nutrition.

A new kind of low-inductance transformer type magnetic switch (TTMS) with coaxial cylindrical conductors

As important devices for voltage boosting and switching, respectively, pulse transformer and magnetic switch are widely used in pulsed power technology. In this paper, a new kind of transformer type magnetic switch (TTMS) with coaxial cylindrical conductors is put forward to combine the functions of voltage boosting and switching in one power device. As a compact combination device of discrete pulse transformer and magnetic switch, the compact TTMS decreases the required volume of magnetic cores in a large scale. The primary windings of the TTMS have a parallel combination structure so that the TTMS which only has 3 turns of secondary windings has a step-up ratio at 1:9. Before the magnetic core saturates, the TTMS has low unsaturated inductances of windings and good pulse response characteristics, so it can be used to substitute the Marx generator to charge the pulse forming line (PFL) at the ranges of several hundred kV and several hundred ns. After the core saturates, the cylindrical conductors can decrease the saturated inductance of the secondary windings of TTMS to a level less than 400 nH. As a result, the proposed TTMS can be used as the boosting transformer and main switch of helical Blumlein PFL to form the quasi-square voltage pulse on the 160 Ω load with a short pulse rise time only at 60 ns.

An overview of LULU operators and discrete pulse transform for image analysis

This paper presents an overview of LULU operators and discrete pulse transform (DPT). Data extraction from signals and images is a popular area of research. Different methods are being used for data extraction such as different types of linear and nonlinear operators. LULU operator is one of the most important rank selector nonlinear filters used for data analysis which is widely being used for signal analysis, especially in impulse noise filtering. It is computationally more efficient and the behaviour of the operator is simple to describe. Based on the composition of different orders of LULU operators, DPT on multi-resolution is defined, which describes the sequences into pulses with different magnitudes. DPT allows a multi-resolution measure of roughness of images and sequences. It is a powerful technique for image analysis and can also be used for the estimation of standard deviation of a random distribution.

Spatial distribution of Illex argentinus in San Matias Gulf (Northern Patagonia, Argentina) in relation to environmental variables: A contribution to the new interpretation of the population structuring

Traditionally, it was assumed that major spawning activity of Illex argentinus occurs in discrete pulses along the outer-shelf/slope off Argentina/southern Brazil during late-fall/winter and that early life stages develop near the Brazil–Malvinas Confluence (BMC). However, a novel hypothesis of the population structuring of the species was proposed that states that coastal waters may be important as spawning and feeding grounds. Here, we analyzed the spatial distribution of Illex argentinus inside San Matias Gulf based on the position of the CPUE of jiggers in order to improve the knowledge of the population structuring in coastal regions. Squids were mainly concentrated on the northern region of the gulf where favorable oceanographic conditions (e.g. water stratification, chlorophyll-a concentration peaks) to feeding and spawning are present. These results provided empirical evidences that individuals of I. argentinus use Argentinean coastal waters, particularly San Matias Gulf, as permanent feeding and spawning grounds which supports the new hypothesis.

3D shape from focus using LULU operators and discrete pulse transform in the presence of noise

3D shape recovery is an interesting and challenging area of research. Recovering the depth information of an object from a sequence of 2D images with varying focus is known as shape from focus. Focus value of an image carries information about the object and shape from focus is a method which depends on different focused value images. It reconstructs the shape/surface/depth of an object based on the different focused values of the object. These different focused valued images should be captured from the same angle. Calculating the shape of the object from different images with different focused values can be done by applying sharpness detection methods to maximize and detect the focused values. In this paper, we propose new 3D shape recovery techniques based on LULU operators and discrete pulse transform. LULU operators are nonlinear rank selector operators that are efficient with low complexity. They hold consistent separation, total variation and shape preservation properties. Discrete pulse transform is a transform that decomposes image into pulses. Therefore selection of right pulses, give sharpest focus values. The proposed techniques provide better result than traditional techniques in a noisy environment.

Nonlinear Filters and Characterization of the Discrete Pulse Transform of Images

The Discrete Pulse Transform (DPT) for images and videos has been developed over the past few years and provides aВ theoretically sound setting for a nonlinear decomposition of an image or video. In [1] the theoretical basis of the DPT was presented. In this paper we now present a soundВ characterization of this useful nonlinear hierarchical decomposition by referring to its ability as a separator, the consistency of the decomposition, as well as the smoothing ability of the decomposition.

Investigation of the Soft-Switched Electron Load

A high frequency pulse D.C. Link Soft-Switched Electron load based on Discrete Pulse Modulation (DPM) control is introduced. The method of energy recovery is used to implement various discharging of the storage battery．The electron load developed has good performances such as a good sinusoidal output wave，a rapid dynamic response and a good stability etc.．

HIFU treatment time reduction through heating approach optimisation

Purpose: This study evaluated the HIFU treatment time reductions attainable for several scan paths when optimising the heating approach used (single, discrete pulses versus volumetric scanning) and the paths’ focal zone heating locations’; number (NFZL), spacings, sequencing order, number of heating cycles (NCYCLES), and heating times. Also evaluated were the effects of focal zone size, increased tissue absorptivity due to heating, and optimisation technique.Materials and methods: Treatments of homogeneous constant property tumours were simulated for several simple generic tumour shapes and sizes. The concentrated heating approach (which delivered the desired thermal dose to each location in one discrete heating pulse (NCYCLES = 1)) was compared to the fractionated heating approach (which dosed the tumour using multiple, shorter pulses repeatedly scanned around the heating path (i.e. ‘volumetric scanning’ with NCYCLES > 1)). Treatment times were minimised using both simultaneous, collective pulse optimisation (which used full a priori knowledge of the interacting effects of all pulses) and sequential, single pulse optimisation (which used only the information from previous pulses and cooling of the current pulse).Results: Optimised concentrated heating always had shorter treatment times than optimised fractionated heating, and concentrated heating resulted in less normal tissue heating. When large, rapid tissue absorptivity changes were present (doubled or quadrupled immediately after heating) the optimal ordering of the scan path's sequence of focal zone locations changed.Conclusions: Concentrated heating yields significant treatment time reductions and less normal tissue heating when compared to all fractionated scanning approaches, e.g. volumetric scanning.

Simple equations for diffusion in response to heating

The diffusive closure temperature of minerals (TC) was originally conceived for application to systems undergoing cooling (Dodson, 1973) and is of limited use for cases of diffusive “opening” during heating or for complete heating–cooling cycles. Here we use a combination of numerical simulations and mathematics to arrive at general equations for progressive diffusive loss from a sphere when temperature increases linearly with time, and also for discrete thermal pulses. For linear heating (T∝time), and with constant surface concentration and no radiogenic in-growth, prograde “diffusive opening” is accurately described byTrt%=0.457⋅Ea/Rχh+logEa⋅D0R⋅dT/dt⋅a2where D0 (m2/s) and Ea (J/mol) are the Arrhenius parameters for the diffusant of interest, dT/dt is the heating rate (°/s), a is the radius (in meters) of the spherical domain under consideration, R is the gas constant (J/°-mol), and χh is a constant. For a given heating trajectory, Trt% is the temperature (in kelvins) at which a specific fractional retention (or loss) is reached, and where the constant χh has a specific value. For retention levels of 50%, 99% and 99.9%, χh has values of −0.785, 2.756 and 4.751, respectively. The equation is accurate to within 5° for the vast majority of measured diffusion laws, and to within ~2° for ~90% of them. For noble gases specifically it is accurate to within 1° in almost all cases. There are essentially no restrictions on the grain size or heating rate (up to 2000°C/Myr) that can be assumed without loss of accuracy.For thermal pulses in which the temperature of the spherical grain of interest rises at a constant rate from 293K to a maximum value and then falls back linearly to the starting temperature (i.e., a “steeple” T–t path), the diffusive response for the thermal cycle is given bylogζ=logD0τa2+195Tpk−0.4416EaRTpk−1.35,where ζ=a−2∫t=0τD(t)dt, τ is the duration of the heating event (in seconds) and Tpk is the peak temperature in kelvins. The total fractional loss (F) is uniquely determined by the value of ζ; conversion of logζ to F is straightforward, as discussed in the text.Diffusive loss during parabolic T–t paths conforms to a similar relation:logζ=logD0τa2+140Tpk−0.437EaRTpk−0.8.Given knowledge of the Arrhenius law for the diffusant of interest, these equations provide accurate estimates of the total diffusive loss for a steeple- or parabola-shaped T–t path of any duration and intensity—including asymmetrical paths.

A Dual Golay Complementary Pair of Sequences for Improving the Performance of Phase-Shift Pulse BOTDA Fiber Sensor

We propose in this paper to configure a dual Golay complementary pair of sequences (DGCP) by nesting one Golay complementary pair of sequences (GCP) into the other GCP. We show that the DGCP also has the unique property that the side lobes of the correlation functions are cancelled exactly as the conventional GCP. The DGCP allows the simultaneous use of coded RZ-pulses and coded NRZ-pulses in the pump light of the Brillouin optical time-domain analysis (BOTDA). We call them in this paper coded discrete pulses and coded continuous pulses, respectively. The simultaneous use of both types of coded pulses for the BOTDA makes it possible to employ virtually longer code than the use of only one kind of coded pulses. We theoretically show the dependence of signal-to-noise ratio enhancement (SNRE) on the code length of the DGCP as well as on the code lengths of the GCPs used for the discrete and continuous pulses. Examination of the spatial resolution is also given. Experimental results illustrate the theoretical considerations; about 7 dB of SNRE and 10-cm of spatial resolution are achieved by using DGCP, being in accordance with the theory.

On partial discharge measurement in dielectric liquids

Partial discharge detection in dielectric liquids requires particular PD measurement techniques and instruments. Simultaneous partial discharge (PD) measurements that are employed on insulating liquids, using dual narrow/wide band detectors, are described. Narrow band PD detectors, which are of the integrating type are suitable for the measurement of the total charge transfer in pC of the overall discharge event. Wide band measurement techniques permit the acquisition of the discrete PD pulses in dielectric liquids, that comprise the overall PD pulse burst signal. These PD pulse bursts are comprised of discrete high frequency pulses of usually ascending magnitude charge transfers. The time position of these pulses within the pulse burst is determined by the times at which the Paschen's minima occur across the expanding cavity due to the small size of the microcavities. In order for them to undergo discharge requires enormously high internal pressures (ca 10 MPa) to ensure a sufficient number of charge carriers. The life duration of these cavities is of the order of several's, with the cavity collapsing, when its size reaches dynamic instability.

Sedimentary record of the Dukla Basin (Outer Carpathians) and its implications for basin evolution

The Late Cretaceous to Oligocene strata of the Dukla Nappe, which is a part of the accretionary wedge formed in front of the Carpathian orogen, record a history of the basin development from remnant to foreland basin stages. The lower part of the succession indicates the first stage of basin evolution characterized by turbidite systems fed from the E (NE) to W (SW). The system encompasses deposits of the Łupkow and Cisna formations deposited in a channel-lobe transition (Łupkow Fm.) and in sandstone-rich channelized lobes (Cisna Fm.) The transitional phase is represented by deposits of the Submenilite Formation derived from two different sources (SE and N) and deposited in a submarine slope/ramp environment. The third stage of basin evolution is marked by the advancing front of the Carpathian orogen resulting in peripheral foreland basin development. Increased tectonic activity led to a switch in sediment source from the SE to the NW, more complex topography of the basin and a change in sediment distribution. The initial phase of this stage is characterized by low-density turbidites and suspension fall-out sediments of the Menilite Fm. Discrete tectonic pulses are recorded by the thick Cergowa sandstones, mostly deposited by hybrid flows and high-density turbidity currents. A decrease in tectonic activity is suggested by heterolithic deposits of the Krosno Fm. capping the sedimentary succession.

Arrival-time model with femtosecond precision for simulating laser pulses propagating through atmospheric turbulence

A theoretical arrival-time model with femtosecond precision is proposed. The model samples a laser pulse, then delays the discrete pulse sequence precisely. By reconstructing the delayed sequence we obtain the laser pulse in the analog domain with desired arrival-time. The kernel of the model is a filter bank, which is a cascade of digital unit delay filters, followed by a fractional delay filter. Furthermore, physical parameters such as the turbulence structure parameter, mean refractive index, turbulence outer scale and path-length along the propagating path are incorporated in the kernel. At last, through numerical examples, the femtosecond precision is manifested.

FULL WAVEFORM LIDAR EXPLOITATION TECHNIQUE AND ITS EVALUATION IN THE MIXED FOREST HILLY REGION

Abstract. In this paper a full waveform exploitation technique and its evaluation in the mixed forest hilly region is presented. The increment in ground penetration by using the full waveform exploitation technique compared to the discrete LiDAR pulses during autumn and winter season is evaluated. The results showed that the technique used for the full waveform exploitation has effectively increased the ground penetration by 50 % and 20 %, respectively, during autumn and winter in the mixed forest hilly region compared to the discrete return pulses. The accuracy test of the LiDAR derived terrain model constructed from the discrete LiDAR pulses and full waveform LiDAR pulses obtained during autumn and winter has also been performed. The RMSE of the LiDAR derived DTM with 1m grid size constructed from the discrete LiDAR pulses obtained during autumn and winter were 0.73 m and 0.22 m respectively. Likewise, the RMSE of the LiDAR derived DTM constructed from the full waveform LiDAR pulses obtained during autumn and winter were 0.59 m and 0.21 m respectively. The results also showed that by using full waveform return pulses, DTM constructed for both seasons were improved compared to the DTM generated from discrete LiDAR pulses.

Depositional processes and gas pore pressure in pyroclastic flows: an experimental perspective

The depositional processes and gas pore pressure in pyroclastic flows are investigated through scaled experiments on transient, initially fluidized granular flows. The flow structure consists of a sliding head whose basal velocity decreases backwards from the front velocity (Uf) until onset of deposition occurs, which marks transition to the flow body where the basal deposit grows continuously. The flows propagate in a fluid-inertial regime despite formation of the deposit. Their head generates underpressure proportional to Uf2 whereas their body generates overpressure whose values suggest that pore pressure diffuses during emplacement. Complementary experiments on defluidizing static columns prove that the concept of pore pressure diffusion is relevant for gas-particle mixtures and allow characterization of the diffusion timescale (td) as a function of the material properties. Initial material expansion increases the diffusion time compared with the nonexpanded state, suggesting that pore pressure is self-generated during compaction. Application to pyroclastic flows gives minimum diffusion timescales of seconds to tens of minutes, depending principally on the flow height and permeability. This study also helps to reconcile the concepts of en masse and progressive deposition of pyroclastic flow units or discrete pulses. Onset of deposition, whose causes deserve further investigation, is the most critical parameter for determining the structure of the deposits. Even if sedimentation is fundamentally continuous, it is proposed that late onset of deposition and rapid aggradation in relatively thin flows can generate deposits that are almost snapshots of the flow structure. In this context, deposition can be considered as occurring en masse, though not strictly instantaneously.