Improving the Hufnagel-Andrews-Phillips refractive index structure parameter model using turbulent intensity.

This paper proposes a modification of the Hufnagel-Andrews-Phillips (HAP) Refractive Index Structure Parameter model that will better characterize the HAP profile against experimental data using the turbulent intensity, which is the ratio of wind speed variance to the average wind speed-squared, and Korean Refractive Index Parameter yearly statistics, Comparisons between this modified HAP model, the Critical Laser Enhancing Atmospheric Research 1 (CLEAR 1) profile model and several of the data sets are made. These comparisons highlight that this new model offers a more consistent representation of the averaged experimental data profiles than the CLEAR 1 model did. In addition, comparisons between this model and various experimental data set reported in the literature will show good agreement between the model and averaged data, and reasonable agreement with non-averaged data sets.

Probability density function estimation for filament creation in lossy, turbulent, nonlinear media.

Optical Kerr effects induced by the propagation of high peak-power laser beams through real atmospheres have been a topic of interest to the nonlinear optics community for several decades. Previous work has focused on estimating the Filamentation Onset Distance (FOD) in real atmospheres but not its statistical variance. This paper describes two ad hoc engineering models for predicting the FOD Probability Density Function (PDF) for lossy, turbulent, nonlinear media.

Thermoelectric Energy Harvesting for Implantable Medical Devices.

A thermoelectric energy harvesting system is proposed to supplement the primary power supply of an implantable medical device. A low-power synchronous boost converter capable of boosting 10mV input voltage to 1V output voltage is designed in a 180nm CMOS process. To increase the charging speed, a maximum power transfer scheme is utilized.

Optical Kerr effect field measurements and ad hoc engineering model comparisons.

Optical Kerr effects induced by the propagation of high peak-power laser beams through real atmospheres have been a topic of interest to the nonlinear optics community for several decades. This paper proposes a new analytical model for predicting the filamentation/light channel onset distance in real atmospheres based on modulation instability model considerations. The normalized intensity increases exponentially as the beam propagates through the medium.

Adaptive optics model characterizing turbulence mitigation for free space optical communications link budgets.

Free-space optical communications (FSOC) is becoming an important option for both atmospheric and space-based high data rate networks. Long-range, mobile FSOC links in the former environments must mitigate the effects of turbulence if they are to provide reliable, high link availability under cloud-free atmospheric conditions. Adaptive optics (AO) has been proposed as one means of reducing link degradation in turbulence, but field validated AO performance models are few and not definitive.

Engineering equations for the filamentation collapse distance in lossy, turbulent, nonlinear media.

The propagation of high peak-power laser beams in real atmospheres has been an active research area for a couple of decades. Atmospheric turbulence and loss will induce decreases in the filamentation self-focusing collapse distance as the refractive index structure parameter and volume extinction coefficient, respectively, increase. This paper provides a validated analytical method for predicting the filamentation onset distance in lossy, turbulent, nonlinear media.

Engineering equation for filamentation self-focusing collapse distance in atmospheric turbulence.

The propagation of high peak-power laser beams in real atmospheres will be affected by both linear and nonlinear effects contained therein. Atmospheric turbulence usually will induce decreases in the filamentation self-focusing collapse distance for refractive index structure parameter increases. This paper provided the first validated analytical equation for predicting the nonlinear self-focusing collapse distance based on a modification of Petrishchev's and Marburger's theories.

Calculating RF-Induced Voltages for Implanted Medical Devices in MRI Using Computational Human Models.

Despite its import as a diagnostic tool, patients with active implantable medical devices (AIMDs) are generally denied access to magnetic resonance imaging (MRI). The complexity of MRI environments stems from a multiplicity of fields and numerous scan parameters. In order to perform a risk assessment for RF-induced malfunction, manufacturers perform electromagnetic simulations using computational human models (CHMs) to calculate RF induced energy at the AIMD ports.

Engineering equations for characterizing nonlinear laser intensity propagation in air with loss: erratum.

We present an erratum regarding the x-axis label in several figures, and one equation citation correction.

Engineering equations for characterizing non-linear laser intensity propagation in air with loss.

The propagation of high peak-power laser beams in real atmospheres will be affected at long range by both linear and nonlinear effects contained therein. Arguably, J. H.

Virtual Humans for Implantable Device Safety Assessment in MRI: Mitigating Magnetic Resonance Imaging Hazards for Implanted Medical Devices.

Magnetic resonance imaging (MRI) is the preferred modality for soft tissue imaging because of its nonionizing radiation and lack of contrast agent. Due to interactions between the MR system and active implantable medical devices (AIMDs), patients with implants such as pacemakers are generally denied access to MRI, which presents a detriment to that population. It has been estimated that 50-75% of patients with a cardiac device were denied access to MRI scanning and, moreover, that 17% of pacemaker patients need an MRI within 12 months of implantation [1].

MR conditional safety assessment of implanted medical devices: advantages of computational human phantoms.

Until recently, patients with active implantable medical devices (AIMDs) have been contraindicated for magnetic resonance imaging (MRI). Current efforts to demonstrate safety of these devices separate the interaction of the device and MRI into several hazards. For several of these hazards, computational human phantoms (CHPs) are used to provide conservative conditions for a risk-based analysis.

SAW-LC coupled resonator wideband VCO for medical telemetry.

Wireless links with implantable devices can help in real-time monitoring of symptoms, irregularities, implanted device efficacy and their reconfiguration. We present the design of a low-power wideband voltage controlled oscillator (VCO) to facilitate implantable wireless telemetry. A coupled SAW-LC resonator design combines high Q and spectral purity of a SAW element and tunability of an LC-tank.

Statistical detection of resolved targets in background clutter using optical/infrared imagery.

The use of optics to detect targets has been around for a long time. Early attempts at automatic target detection assumed target plus noise, which means that the targets were small compared to the pixel field of view and therefore unresolved. However, the advent of advanced focal plane technology has resulted in optical systems that can provide highly resolved target images.

High-sensitivity DPSK receiver for high-bandwidth free-space optical communication links.

A high-sensitivity modem and high-dynamic range optical automatic gain controller (OAGC) have been developed to provide maximum link margin and to overcome the dynamic nature of free-space optical links. A sensitivity of -48.9 dBm (10 photons per bit) at 10 Gbps was achieved employing a return-to-zero differential phase shift keying based modem and a commercial Reed-Solomon forward error correction system.

Free-space optical communications link budget estimation.

This paper describes a new methodology of estimating free-space optical communications link budgets to be expected in conditions of severe turbulence. The approach is derived from observing that the ability of an adaptive optics (AO) system to compensate turbulence along a path is limited by the transmitter and receiver Rayleigh range, proportional to the diameter of the optics squared and inverse of the wavelength of light utilized. The method uses the Fried parameter computed over the range outside of the transmitter and receiver Rayleigh ranges, to calculate the Strehl ratios that yield a reasonable prediction of the light impinging on the receiving telescope aperture and the power coupling into the fiber.

Probability of Interference between LP-LDC and LBT MICS implants in a medical care facility.

The latest generation of medical implants incorporate RF telemetry to facilitate communication of patient data to the patient's physician. Regulatory agencies have enabled medical implant telemetry by allocating RF spectrum in the 402-405 MHz band. The first generation of regulations mandated the use of a Listen-Before-Talk (LBT) protocol.

Quantitative, low cycle, crack initiation fatigue testing of fine wires and CENELEC standard pacing coil.

Uniaxial fatigue testing was performed on different diameters of fine wires made from MP35N. The fatigue limits of the wires differed from each other based on the diameter of the wire. Multiaxial (shear) fatigue testing was also performed on a benchmark coil used to evaluate the fatigue life of all modern pacemaker leads (the CENELEC standard coil).

Bipolar pacemaker leads: new materials, new technology.

This commentary is in response to a review published earlier in this journal. It is intended to provide additional information and supplement the original paper. A short review of the failure mechanisms of polyurethane pacing lead materials is provided.

New ICD-technologies: first clinical experience with dual-chamber sensing for differentiation of supraventricular tachyarrhythmias.

Inappropriate ICD therapy for supraventricular arrhythmias remains an unsolved problem and may lead to serious clinical situations. Current algorithms for differentiation of supraventricular and ventricular arrhythmias are based on ventricular sensing solely and, therefore, lack sensitivity and specificity. This preliminary analysis from a multicenter trial comprises data from the first 26 patients who received a Res-Q Micron active-can ICD (Sulzer Intermedics) with a ventricular defibrillation lead and an additional bipolar lead for atrial sensing.

The patient alert system--pilot study of built-in warning systems for pacemakers.

Malfunction of a pacing system can be life-threatening for a pacemaker-dependent patient. It would be desirable for implantable pulse generators to have a built-in automatic warning system capable of alerting the patient as soon as a potentially dangerous disorder is detected. In this study, seven patients (mean age, 72.

Does reducing capacitance have potential for further miniaturisation of implantable defibrillators?

Objective: To determine whether considerably smaller capacitors could replace 125 microF capacitors as the standard for use in implantable defibrillators.

Methods: Measured energy, impedance, voltage, and current delivered were compared at defibrillation threshold in 10 mongrel dogs for defibrillation using 75 microF and 125 microF capacitors alternated randomly. Defibrillation was attempted with biphasic shocks of comparable tilt between an endocardial lead in the right ventricular apex and a "dummy" active can of an experimental implantable device placed in the subpectoral position.

Automatic target detection and recognition in multiband imagery: a unified ML detection and estimation approach.

Multispectral or hyperspectral sensors can facilitate automatic target detection and recognition in clutter since natural clutter from vegetation is characterized by a grey body, and man-made objects, compared with blackbody radiators, emit radiation more strongly at some wavelengths. Various types of data fusion of the spectral-spatial features contained in multiband imagery developed for detecting and recognizing low-contrast targets in clutter appear to have a common framework. A generalized hypothesis test on the observed data is formulated by partitioning the received bands into two groups.