Radiation from a current filament driven by a traveling wave

Solutions are presented for the electromagnetic fields radiated by an arbitrarily oriented current filament located above a perfectly conducting ground plane and excited by a traveling current wave. Both an approximate solution, valid in the fraunhofer region of the filament and predicting the radiation terms in the fields, and an exact solution, which predicts both near and far field components of the electromagnetic fields, are presented. Both solutions apply to current waveforms which propagate along the channel but are valid regardless of the actual waveshape. The exact solution is valid only for waves which propagate at the speed of light, and the approximate solution is formulated for arbitrary velocity of propagation. The spectrum-magnitude of the fourier transform-of the radiated fields is computed by assuming a compound exponential model for the current waveform. The effects of channel orientation and length, as well as velocity of propagation of the current waveform and location of the observer, are discussed. It is shown that both velocity of propagation and an effective channel length are important in determining the shape of the spectrum

Simulation of radiation from lightning return strokes: The effects of tortuosity

A Monte Carlo simulation has been developed for the electromagnetic fields radiated from a tortuous lightning channel. This was done using a piecewise linear model for the channel and employing for each element the field radiated by a traveling wave on an arbitrarily oriented filament over a conducting plane. The simulation reproduces experimental data reasonably well and had been used to study the effects of tortuousity on the fields radiated by return strokes. Tortuosity can significantly modify the radiated waveform, tending to render it less representative of the current pulse and more nearly unipolar than one would expect based on the theory for a long straight channel. In the frequency domain the effect of tortuosity is an increase in high frequency energy as compared with an equivalent straight channel. The extent of this increase depends on the mean length of the elements comprising the channel and can be significant

Rate statistics for radio noise from lightning

Radio frequency noise from lightning was measured at several frequencies in the HF - VHF range at the Kennedy Space Center, Florida. The data were examined to determine flashing rate statistics during periods of strong activity from nearby storms. It was found that the time between flashes is modeled reasonably well by a random variable with a lognormal distribution

High Frequency Scattering from Arbitrarily Oriented Dielectric Disks

Calculations have been made of electromagnetic wave scattering from dielectric disks of arbitrary shape and orientation in the high frequency (physical optics) regime. The solution is obtained by approximating the fields inside the disk with the fields induced inside an identically oriented slab (i.e. infinite parallel planes) with the same thickness and dielectric properties. The fields inside the disk excite conduction and polarization currents which are used to calculate the scattered fields by integrating the radiation from these sources over the volume of the disk. This computation has been executed for observers in the far field of the disk in the case of disks with arbitrary orientation and for arbitrary polarization of the incident radiation. The results have been expressed in the form of a dyadic scattering amplitude for the disk. The results apply to disks whose diameter is large compared to wavelength and whose thickness is small compared to diameter, but the thickness need not be small compared to wavelength. Examples of the dependence of the scattering amplitude on frequency, dielectric properties of the disk and disk orientation are presented for disks of circular cross section

Tourniquetless Total Knee Arthroplasty With Modern Perioperative Protocols Decreases Pain and Opioid Consumption in Women

Background This study examined whether a modern total knee arthroplasty (TKA) protocol without a tourniquet results in less patient-reported pain and in-hospital opioid consumption compared to TKA with a tourniquet. Methods A retrospective study of 203 primary unilateral cemented TKAs consecutively performed with or without tourniquet was performed. Identical perioperative pain and blood loss protocols were used in all cases. In tourniquetless TKAs, the tourniquet was not inflated at any time, and sterile CO2 gas compression maximized cement interdigitation. Results After exclusions for scientific confounds, 184 TKAs (93 with tourniquet; 91 tourniquetless) were analyzed. Controlling for multiple covariates, females with a tourniquet reported significantly more pain (P = .002) and opioid consumption (P < .001) the first 24 hours after surgery compared to females without a tourniquet. There were no differences in pain (P = .192) or amount of opioids consumed (P = .203) among males with and without a tourniquet. Tourniquet use resulted in a significant reduction in blood loss for both females (P ≤ .040) and males (P ≤ .020), although the total blood savings of approximately 200 mL is of unknown clinical significance. Conclusion Avoiding tourniquet use during TKA for females may be a relatively risk-free adjunct to minimize opioid consumption during hospitalization. Further study is warranted to elucidate the factors accounting for different outcomes in females and males

A crude model to study radio frequency induced density modification close to launchers

The interplay between radio frequency (RF) waves and the density is discussed by adopting the general framework of a 2-time-scale multi-fluid treatment, allowing to separate the dynamics on the RF time scale from that on the time scale on which macroscopic density and flows vary as a result of the presence of electromagnetic and/or electrostatic fields. The focus is on regions close to launchers where charge neutrality is incomplete and waves are commonly evanescent. The fast time scale dynamics influences the slow time scale behavior via quasilinear terms (the Ponderomotive force for the case of the equation of motion). Electrons and ions are treated on the same footing. Also, both fast and slow waves are retained in the wave description. Although this work is meant as a subtopic of a large study-the wave induced "convective cell" physics at hand is of a 2- or 3-dimensional nature while this paper limits itself to a single dimension-a few tentative examples are presented

Machine learning-driven approach for large scale decision making with the analytic hierarchy process

The Analytic Hierarchy Process (AHP) multicriteria method can be cognitively demanding for large-scale decision problems due to the requirement for the decision maker to make pairwise evaluations of all alternatives. To address this issue, this paper presents an interactive method that uses online learning to provide scalability for AHP. The proposed method involves a machine learning algorithm that learns the decision maker’s preferences through evaluations of small subsets of solutions, and guides the search for the optimal solution. The methodology was tested on four optimization problems with different surfaces to validate the results. We conducted a one factor at a time experimentation of each hyperparameter implemented, such as the number of alternatives to query the decision maker, the learner method, and the strategies for solution selection and recommendation. The results demonstrate that the model is able to learn the utility function that characterizes the decision maker in approximately 15 iterations with only a few comparisons, resulting in significant time and cognitive effort savings. The initial subset of solutions can be chosen randomly or from a cluster. The subsequent ones are recommended during the iterative process, with the best selection strategy depending on the problem type. Recommendation based solely on the smallest Euclidean or Cosine distances reveals better results on linear problems. The proposed methodology can also easily incorporate new parameters and multicriteria methods based on pairwise comparisons.This research was funded by National Funds through the FCT—Portuguese Foundation for Science and Technology, References UIDB/05256/2020 and UIDP/05256/2020

Little Creek Naval Amphibious Base Chesapeake Bay Shoreline

Little Creek Naval Amphibious Base (NAB) is located in Virginia Beach, Virginia. It’s shoreline along the southern Chesapeake Bay extends from Little Creek Inlet eastward approximately 1.5 miles to the NAB’s eastern boundary. In 1997, a study and report entitled “LITTLE CREEK NAVAL AMPHIBIOUS BASE, CHESAPEAKE BAY SHORELINE, SHORELINE MANAGEMENT PLAN and OFFICER’S BEACH SHORE PROTECTION EVALUATION” was produced by VIMS’s Shoreline Studies Program (Hardaway et al., 1997). The purpose of that report was to assess the rates and patterns of beach change along the Chesapeake Bay shoreline at Little Creek NAB in order to develop a shoreline management plan, particularly for the Officer’s Beach (“O” Beach). Field surveys, historical aerial imagery, empirical models and computer models were used to address these objectives. Plan recommendations resulted in the construction of a headland breakwater system and revetments at the “O” Beach as well as a series of proposed breakwaters along the length of the Little Creek NAB coast. In 2002, an update to the shoreline management plan was performed (Hardaway et al., 2004). The purposes of that effort were to update the Hardaway et al. (1997) study and to determine if additional management strategies should be implemented. Elements of the previous report were presented to provide the background perspective and bring the reader up-to-date. Generally, the shoreline subreach just west of the “O” Beach has continued to erode from the existing revetment westward toward the Enlisted Beach (“E” Beach). This trend was prevalent prior to 1997 and was predicted to continue in the previous study. The question is how long will this trend continue and what impact will it have on the Base’s shoreline, particularly the Bayfronting primary dune system which is eroding along much of the coast? This report attempts to detail the potential impacts to Little Creek NAB Chesapeake Bay coast if the updated management plan is implemented. It was determine that the impact will be to the shoreline position and consequently to the associated beach/dune system. The management recommendations of the updated plan are to create headland features with large stone breakwaters and to allow the adjacent coast to continue to recede toward dynamic equilibrium. Dynamic equilibrium is a concept whereby shoreline embayments, whether natural or man-made, will attain a state where the shore planform is stable given the input and output of littoral sands. In the case of Little Creek NAB, the input of sand from ongoing beach nourishment efforts west of Lynnhaven Inlet is a significant factor

Mixed brittle and viscous strain localisation in pelagic sediments seaward of the Hikurangi margin, New Zealand

Calcareous‐pelagic input sediments are present at several subduction zones and deform differently to their siliciclastic counterparts. We investigate deformation in calcareous‐pelagic sediments drilled ~20 km seaward of the Hikurangi megathrust toe at Site U1520 during IODP Expeditions 372 and 375. Clusters of normal faults and subhorizontal stylolites in the sediments indicate both brittle faulting and viscous pressure solution operated at 150°C where frictional (possibly seismic) slip likely predominates. Plain Language Summary The type of sediments entering subduction zones will influence the way the plates in the subduction zone slide past one another. We looked at limestones in sediments drilled before they reach the subduction zone and found that because of the pressure they are under, they begin to crack and dissolve at very shallow depths. Most of the dissolution happens on thin layers where it concentrates clay by removing other, more soluble minerals. We compare how much vertical shortening we see in the sediments to a computer model. The model overestimates vertical shortening over the history of the sediment unless either high pressure fluids reduce the pressure felt by the sediments, or dissolution is governed by the largest sediment grains rather than their average size. Dissolving and cracking make the sediments weaker by concentrating soft materials such as clay. When these sediments enter the subduction zone, the two plates might slip past one another more easily on these weak regions, possibly during slow slip events

New bioassays reveal susceptibility of stone-fruit rootstocks to capnodis tenebrionis larvae

Larvae of Capnodis tenebrionis (L.) (Coleoptera Buprestidae) feed and develop in roots of stone-fruit trees, thereby decreasing their efficiency, which can lead to plant death. The control of these larvae is critical, due to their localization in the root, and the management of this pest is focused on adults, mainly by using non-specific synthetic insecticides. Less susceptible Prunus rootstocks might be applied as a preventative management of larval infestation by this pest. The current research investigated the susceptibility to C. tenebrionis larvae of the most commonly used rootstocks by combining two bio-assays during two-year trials: development of larvae assayed on semi-artificial substrates containing rootstock bark flour; infestation by neonate larvae on rootstock twigs. The rearing assay on semi-artificial substrates made it possible to distinguish (1) a rootstock cluster (Montclar and GF677) in which larvae developed faster and heavier and produced larger adults, (2) a cluster (Adesoto, CAB6P, Colt and MaxMa60) in which larval growth was less efficient as well as adult size, and (3) a cluster (Garnem and Myrabolan 29C) with intermediate responses in larval development and adult size. The twig infestation assay by neonates showed the most infested (Colt) and least infested (Barrier, MaxMa60 and Marianna 26) rootstocks. When the results of both assays are combined, GF677 and Myrabolan 29C appear more susceptible, while Adesoto and MaxMa60 less susceptible to C. tenebrionis larvae, although Barrier and Marianna 26 require further investigation. The experimental model applied in the current trials can enable processing of a large number of tests on different rootstocks, thereby allowing the accumulation of a large quantity of data on the potential susceptibility of rootstocks. The possibility of rearing larvae on a substrate can allow comparison of additional compounds that could interact with larval growth