Calculation Of Gain Research Articles

Design, Characterization, and Applications of Index-Patterned Fabry–Pérot Lasers

The design and measured performance characteristics of a range of index-patterned diode laser sources are presented. These devices incorporate slotted regions etched into the laser ridge waveguide, which are formed in the same fabrication step as the ridge, thus avoiding the requirement for complex lithography and regrowth steps. We first demonstrate that the index profile of single and multimode devices can be obtained directly from an inverse problem solution based on a perturbative calculation of the threshold gain of the longitudinal modes of the cavity. Measurements of temperature stability, linewidth, and modulation bandwidth of single-mode devices obtained in this way are presented. It is then shown that the design of multimode devices including two-color and pulsed mode-locked devices designed to support a discrete comb of modes is also possible. We finally demonstrate a tunable source based on a multisection design defined using etched features. This device is shown to have wide tunability with narrow linewidth modes and fast wavelength switching speed.

Highly efficient tabletop x-ray laser atλ=41.8 nm in Pd-like xenon pumped by optical-field ionization in a cluster jet

The atomic-kinetic calculations of gain at 41.8 nm in Pd-like xenon are performed. The interpretation of known experiments has proved that x-ray laser in Pd-like xenon is feasible in the extremely wide range of atomic densities: 10${}^{17}$ \ensuremath{\leqslant} [Xe${}^{8+}$] \ensuremath{\leqslant} 3 \ifmmode\times\else\texttimes\fi{} 10${}^{19}$ cm${}^{\ensuremath{-}3}$. This result is due to the large cross sections (and rates) of level excitations in Pd-like xenon by electron impact. We propose a highly efficient tabletop x-ray laser pumped by optical-field ionization in a xenon cluster jet. The efficiency of \ensuremath{\sim}0.5% is possible with a pump laser pulse energy of \ensuremath{\geqslant}0.001 J and an intensity of \ensuremath{\sim}10${}^{16}$ W/cm${}^{2}$.

Aerodynamic coupling model development and autopilot design for highly manoeuvring skid-to-turn missiles

This article describes the aerodynamic coupling modelling problem and autopilot design method of highly manoeuvring skid-to-turn missiles. A well-defined linearized aerodynamic model of flight vehicle is necessary to design high-performance flight control system. Especially, in the case of missile with high angle of attack and large aerodynamic coupling effect, a linearized model used for the flight control system design plays an important role in determining the stability and performance of the overall system. Also, the partial derivatives of aerodynamic coefficients being used to derive the linearized model represent the primary characteristics that determine the stability of the control system. In this article, the calculation method of aerodynamic derivatives and autopilot design method which reflects the coupling effects of highly manoeuvrable missiles is proposed. First, two different calculation methods of aerodynamic derivatives are suggested. Also, the strength and weakness of each method are analysed. Also, it is explained that the calculation method of aerodynamic derivatives using the alpha–beta constant method is more reasonable than bank constant method for highly manoeuvrable missiles with severe coupling effects. In this case, the effective autopilot design approach is to directly apply the control schemes for multi-input multi-output systems. The suggested method is applied to the derivation of linearized aerodynamic coupling model for skid-to-turn missile which has heavy aerodynamic coupling due to high manoeuvrability. For validation of the suggested model, the autopilot design processes for a generic surface-to-air missile are performed. Non-linear simulation results are given to show that the proposed modelling method reflects the motion characteristics of non-linear missile system. In order to improve the performance of autopilot, the autopilot implementation procedures using the online gain calculation scheme are also discussed briefly.

Mechanical Cavopulmonary Assistance of a Patient-Specific Fontan Physiology: Numerical Simulations, Lumped Parameter Modeling, and Suction Experiments

This study investigated the performance of a magnetically levitated, intravascular axial flow blood pump for mechanical circulatory support of the thousands of Fontan patients in desperate need of a therapeutic alternative. Four models of the extracardiac, total cavopulmonary connection (TCPC) Fontan configuration were evaluated to formulate numerical predictions: an idealized TCPC, a patient-specific TCPC per magnetic resonance imaging data, and each of these two models having a blood pump in the inferior vena cava (IVC). A lumped parameter model of the Fontan physiology was used to specify boundary conditions. Pressure-flow characteristics, energy gain calculations, scalar stress levels, and blood damage estimations were executed for each model. Suction limitation experiments using the Sylgard elastomer tubing were also conducted. The pump produced pressures of 1-16 mm Hg for 2000-6000 rpm and flow rates of 0.5-4.5 L/min. The pump inlet or IVC pressure was found to decrease at higher rotational speeds. Maximum scalar stress estimations were 3 Pa for the nonpump models and 290 Pa for the pump-supported cases. The blood residence times for the pump-supported cases were shorter (0.9 s) as compared with the nonsupported configurations (2.5 s). However, the blood damage indices were higher (1.5%) for the anatomic model with pump support. The pump successfully augmented pressure in the TCPC junction and increased the hydraulic energy of the TCPC as a function of flow rate and rotational speed. The suction experiments revealed minimal deformation (<3%) at 9000 rpm. The findings of this study support the continued design and development of this blood pump.

Gain calculation of a free-electron laser operating with a non-uniform ion-channel guide

Amplification of an electromagnetic wave by a free electron laser (FEL) with a helical wiggler and an ion channel with a periodically varying ion density is examined. The relativistic equation of motion for a single electron in the combined wiggler and the periodic ion-channel fields is solved and the classes of possible trajectories in this configuration are discussed. The gain equation for the FEL in the low-gain-per-pass limit is obtained by adding the effect of the periodic ion channel. Numerical calculation is employed to analyse the gain induced by the effects of the non-uniform ion density. The variation of gain with ion-channel density is demonstrated. It is shown that there is a gain enhancement for group I orbits in the presence of a non-uniform ion-channel but not in a uniform one. It is also shown that periodic ion-channel guiding is used to reach the maximum peak gain in a low ion-channel frequency (low ion density).

Will Quantum Dots Replace Quantum Wells As the Active Medium of Choice in Future Semiconductor Lasers?

The lasing capabilities and limitations of quantum dots are assessed using a first-principles theory with a rigorous treatment of relevant physics and without the free parameters plaguing predictive capabilities in usual gain calculations. Our results reveal quantitatively the extent the reduced threshold advantage is confronted with a larger sensitivity to saturation effects. Added to this intrinsic constraint is the present experimental performance limitation arising from inhomogeneous broadening due to growth fluctuations.

Squatting test: a dynamic postural manoeuvre to study baroreflex sensitivity

Squatting is an active posture test that can be used to assess baroreflex sensitivity. Indeed, the shift from squatting to standing imposes a major orthostatic stress leading to rapid and large changes in arterial blood pressure (BP) and heart rate (HR) allowing precise baroreflex assessment. BP and HR can be continuously and non-invasively monitored with a Finapres device. The standing to squatting transition is accompanied by rises in BP, pulse pressure and cardiac output, mainly due to increased venous return, and by a secondary reduction in HR. Conversely, the squatting to standing transition is associated with an immediate drop in BP and both reflex tachycardia and vasoconstriction. This mirror changes in BP and HR, mimicking those observed with the classical pharmacological approach using vasopressor/vasodilating agents, allows the calculation of the so-called baroreflex gain. The present review describes the haemodynamic changes occurring in normal subjects during the shifts from standing to squatting and from squatting to standing and discusses the underlying cardiovascular and autonomic mechanisms. This careful analysis in healthy individuals should help in the understanding of disturbances that may be observed in patients with autonomic dysfunction, such as in diabetic patients with cardiovascular autonomic neuropathy.

Millimeter-Wave High Radiation Efficiency Planar Waveguide Series-Fed Dielectric Resonator Antenna (DRA) Array: Analysis, Design, and Measurements

A low cost general architecture for a substrate integrated waveguide (SIW) series-fed dielectric resonator antenna (DRA) array, formed by two different slot polarizations, is proposed. In addition, a novel, simple, and generic transmission line (T.L.) circuit model, along with a fast and generic formulation for the new linear array antenna, is developed. The model can be used for reflection coefficient and radiation pattern (gain) calculations. The experimental data from two linear array modules, operating at the millimeter-wave band, are used to verify the simulated results of HFSS and the proposed model results. The measured radiation pattern for a 4 t 1 SIW-DRA array demonstrates a broadside beam with a radiated gain of 11.70 dB over an operating impedance bandwidth of 4.70%. Moreover, the simulated radiation efficiency is more than 90%.

Method for Accurate Gain Calculation of a Highly ${\rm Yb}^{3+}/{\rm Er}^{3+}$-Codoped Waveguide Amplifier in Migration-Assisted Upconversion Regime

The performance of a highly Yb3+/Er3+-codoped phosphate glass femtosecond-laser written waveguide amplifier is numerically analyzed using a macroscopic rate-equation propagation model where concentration-dependent rates for the interatomic migration-assisted energy-transfer mechanisms are considered. The Er3+-upconversion rate is obtained by a rigorous microscopic statistical modeling of the migration-assisted homogeneous upconversion, and the concentration dependence of the experimental Yb3+-sensitization rate utilized reflects the presence of migration among the Yb3+ ions. The results of the amplifier gain dependence on the dopant concentrations illustrate the influence of migration and the need of a careful modeling of interatomic energy-transfer mechanisms for high-concentration rare-earth-doped fiber or waveguide active devices.

Patterns of genetic parameters for height in field genetic tests of Picea abies and Pinus sylvestris in Sweden

We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between parameter values and test environments. Results showed moderate narrow-sense heritabilities (\( {\hat{h}^2} \): mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway spruce, \( {\hat{h}^2} \) increased with better growth and decreased with tree age, while for Scots pine, \( {\hat{h}^2} \) increased with tree age and southward transfer. The additive genetic coefficient of variation (Open image in new window; mean 15%), in Norway spruce, decreased with growth as well as site latitude. Open image in new window in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site genetic age-age correlations in Norway spruce were high, with mean rA and rG of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites.

Examining 40-year stand development following vegetation control: white spruce planted in a trembling aspen dominated cutover

Many of the major questions regarding stand establishment practices involve implications for longer-term ecosystem development. We examined 41-year treatment effects on stand composition and dynamics using a white spruce ( Picea glauca (Moench) Voss) planting, mechanical site preparation (MSP) – herbicide (2,4-D plus 2,4,5-T) trial in a trembling aspen ( Populus tremuloides Michx.) dominated mixedwood. Both barrel and blade MSP with planting increased total and white spruce year 41 stand-level biomass over that in untreated areas. Year 2 herbicide application reduced year 41 trembling aspen biomass without substantially increasing that of white spruce, resulting in total yields similar to those in untreated areas. Barrel MSP increased year 41 trembling aspen biomass over that of untreated areas whereas blade MSP reduced it. Herbicide-related declines in trembling aspen biomass persisted or increased with time whereas white spruce response to herbicide varied with time and MSP. By accounting for inherent growth patterns, age shift calculations gave more balanced temporal depictions of planted white spruce response than effect size or percentage gain calculations. With barrel MSP, stand composition demonstrated a degree of mixedwood homeostasis whereas with blading, trembling aspen composition declined unilaterally from year 20 to 41.

Evaluation of the smooth pursuit tests in multiple sclerosis patients

In multiple sclerosis (MS), randomly located demyelination lesions may involve a large part of the central nervous system and disturb oculomotor activity, including impairment of saccadic and pursuit systems. The aim of the work was to determine the frequency of smooth pursuit disturbances in MS patients and assess the feasibility of various methods for smooth pursuit assessment: the clinical bedside examination and quantitative electrooculographic (EOG) recordings. In addition, we analyzed the effects of age on the results of smooth pursuit tests. Sixty MS patients and 50 volunteers underwent clinical bedside examination and EOG evaluation in a tertiary referral university hospital. EOG recordings of smooth pursuit tests with 0.3, 0.4, 0.5 and 15Hz amplitude and gain calculation were preformed. In clinical bedside examination, disorders were found in 25%, and with EOG in 76.6% of patients. In the MS patients and subgroups the mean gain for all frequencies were significantly lower compared with the control group. There were significant differences in gain between younger and older subjects in the control group but no significance in all MS patients their subgroups. Patients with abnormalities in clinical bedside examination had poorer results in EOG tests. There were correlations between gain values and Expanded Disability Status Scale score in MS patients. Smooth pursuit examination provides a valuable parameter of brain dysfunction in MS patients. The EOG test is more useful in detecting subclinical cases than clinical bedside examination, and is not affected by test paradigm or age in MS patients.

Comment on “Increase in voice level and speaker comfort in lecture rooms” [J. Acoust. Soc. Am. 125, 2072–2082 (2009)] (L)

Recently, a paper written by Brunskog Gade, Payá-Ballester and Reig-Calbo, "Increase in voice level and speaker comfort in lecture rooms" [J. Acoust. Soc. Am. 125, 2072-2082 (2009)] related teachers' variation in vocal intensity during lecturing to the room acoustic conditions, introducing an objective parameter called "room gain" to describe these variations. In a failed attempt to replicate the objective measurements by Brunskog et al., a simplified and improved method for the calculation of room gain is proposed, in addition with an alternative magnitude called "voice support." The measured parameters are consistent with those of other studies and are used here to build two empirical models relating the voice power levels measured by Brunskog et al., to the room gain and the voice support.

La plastie de Malingue dans les rétractions digitales de la maladie de Dupuytren : principe, modélisation et application clinique

Introduction Malingue's procedure is a modified Z-plasty for the treatment of digital retraction in Dupuytren's contracture. Geometrical modelling was used to determine the theoretical efficacy of the technique, and the clinical value of the method was assessed with a follow-up of 23 patients over at least two years. Material and Methods Unlike Z-plasty, in which the skin flaps transposed are triangular, the Malingue plasty uses trapezoidal flaps. The direct longitudinal approach is used for the cords and the incision lines cut obliquely across the flexion folds. Euclidean geometry allows calculation of the average theoretical gain with a 45 plasty for a finger of width a, the initial surface being given by S1 = a 2 √2, and the surface after plasty by S2 = a 2(3/4 × [√2 + 1]). A continuous, homogeneous, retrospective series of 27 patients operated by the same surgeon for Dupuytren's contracture with digital flexion contracture was reviewed by a neutral observer. The technique, which combined open-palm fasciectomy with the Malingue plasty, reduced the loss of skin by extending the finger after excising the cords. The plasty was adapted to cover various skin conditions and degrees of finger flexion contracture. Results The Malingue procedure was performed as an outpatient procedure in 23 cases. The average theoretical gain of the skin surface was 46%. The results were evaluated immediately after surgery and over a mean follow-up of 31 months. There were ten cases for a first operation, ten with a first recurrence, and seven with a second recurrence. The operated fingers healed within three weeks with no skin distress or dehiscence. The only surgical complication involved a sectioned collateral radial nerve of the ring finger in a recurrence of Dupuytren's contracture; a venous sleeve was used to re-establish the continuity of the nerve. Midterm complications included CRPS in one patient, recurrence of contracture in three patients, and benign lateral hypoesthesia of the first phalanx in two patients. The mean Tubiana score, which fell from 4.0 to 0.18 immediately after surgery, was 0.67 at the last follow-up, with an overall patient satisfaction index of 95%. Conclusion The Malingue plasty follows a strict but easily applicable protocol. Avoiding the use of skin grafts or flaps, the technique offers satisfactory treatment in most cases of Dupuytren's contracture.

Gain of blue and cyan InGaN laser diodes

Experimental gain spectra of 450 and 490 nm laser diodes on c-plane GaN are analyzed by detailed comparison with the results of a fully microscopic theory. The gain calculation shows the importance of electron LO-phonon coupling. The whole spectral gain shape, not only the low energy tail, is strongly influenced by the LO-phonon contribution. The inhomogeneous broadening parameter increases by a factor of about two for the cyan laser diode in comparison with the blue laser structure. This indicates an increase in alloy and thickness fluctuations for the longer wavelength material.

CMOS图像传感器芯片的自动白平衡算法

A method of gain calculation for auto white balance is proposed which is suitable for hardware implement in CMOS image sensors chip.Based on the method,an auto white balance algorithm used in CMOS image sensors chip is completed.Iterative method and calculation method are combined in this algorithm,and comparator and shift registers are used instead of complex combination logic cells.The computation accuracy and processing speed are improved without hardware expenses.

Modelling radiation-effects in semiconductor lasers for use in SLHC experiments

Optical link components in the SLHC inner detectors are to be exposed to intense radiation fields during operation, and, hence, their qualification in terms of radiation tolerance is required. We have created a model that describes a semiconductor laser undergoing irradiation to enable the extrapolation to full lifetime total fluences from lower fluence radiation tests. This model uses a rate-equation approach with modified gain calculation that takes thermal rollover into account. The model is used to fit experimental data obtained during high-fluence (in excess of 1015 particles/cm2) neutron and pion irradiation tests and evaluate its prediction capability.

Electron-Beam-Initiated Polymerization of Poly(ethylene glycol)-Based Wood Impregnants

The current study demonstrates that methacrylate and acrylate poly(ethylene glycol) (PEG) functional oligomers can be effectively impregnated into wood blocks, and cured efficiently to high conversions without catalyst by e-beam radiation, allowing for less susceptibility to leaching, and favorable properties including higher Brinell hardness values. PEG based monomers were chosen because there is a long history of this water-soluble monomer being able to penetrate the cell wall, thus bulking it and decreasing the uptake of water which further protects the wood from fungal attack. Diacrylate, dimethacrylate, and dihydroxyl functional PEG of M(w) 550-575, of concentrations 0, 30, 60, and 100 wt % in water, were vacuum pressure impregnated into Scots Pine blocks of 15 × 25 × 50 mm in an effort to bulk the cell wall. The samples were then irradiated and compared with nonirradiated samples. It was shown by IR, DSC that the acrylate polymers were fully cured to much higher conversions than can be reached with conventional methods. Leaching studies indicated a much lower amount of oligomer loss from the cured vinyl functional PEG chains in comparison to hydroxyl functional PEG indicating a high degree of fastening of the polymer in the wood. The Brinell hardness indicated a significant increase in hardness to hardwood levels in the modified samples compared to the samples of hydroxyl functional PEG and uncured vinyl PEG samples, which actually became softer than the untreated Scots Pine. By monitoring the dimensions of the sample it was found by weight percent gain calculations (WPG %) that water helps to swell the wood structure and allow better access of the oligomers into the cell wall. Further, the cure shrinkage of the wood samples demonstrated infiltration of the oligomers into the cell wall as this was not observed for methyl methacrylate which is well-documented to remain in the lumen. However, dimensional stability of the vinyl polymer modified blocks when placed in water was not observed to the same extent as PEG.

Exigências proteicas de bovinos de corte suplementados a pasto

Objetivou-se determinar as exigências proteicas de bovinos anelorados, em pastagem com Brachiaria decumbens suplementada com concentrado. Foram utilizados 28 novilhos zebuínos não-castrados com média de 7 meses de idade e 180 kg. Foram abatidos oitos animais-referência para determinação da composição corporal inicial. Os 20 animais restantes foram divididos em cinco lotes de quatro animais, em delineamento inteiramente ao acaso, de modo que cada lote recebeu um dos cinco planos nutricionais: mantença; mistura mineral; e suplementação nos níveis de 0,75; 1,50 e 2,25 kg/animal/dia. A meia-carcaça direita de todos os animais foi dissecada em músculo, gordura e ossos e todos os constituintes do corpo foram pesados para determinação do peso de corpo vazio e da composição corporal. De posse desses dados, procedeu-se ao cálculo das exigências líquidas para ganho de peso em diversas faixas de peso corporal dos animais. Os conteúdos de proteína retidos no corpo dos animais foram regredidos em função do ganho de peso de corpo vazio e da energia retida. As exigências de proteína metabolizável total de um animal de 350 kg e ganho diário de 1,0 kg, foram de 593,59 g/dia. Esse mesmo animal, consumindo 7,40 kg de MS/dia, necessita de dietas com 12,97% de PB na MS total. A exigência líquida de proteína para ganho de peso de animais anelorados não-castrados em pastejo, com até 350 kg de peso corporal, reduzem conforme o peso corporal ou a energia retida aumentam e pode ser estimada a partir da equação: PR (g/dia) = -26,2946 + 247,4853 x GPCVZ - 24,8436 x ER.

Design of a surface-emitting, subwavelength metal-clad disk laser in the visible spectrum

We analyze metal-clad disk cavities designed for nanolasers in the visible red spectrum with subwavelength device size and mode volume. Metal cladding suppresses radiation loss and supports low order modes with room temperature Q of 200 to 300. Non-degenerate single-mode operation with enhanced spontaneous emission coupling factor β is expected with the TE(011) mode that has a 0.46(λ(0)/n)(3) mode volume and Q = 210 in a device of size 0.12λ(0)(3). Threshold gain calculations show that room temperature lasing is possible using multiple GaInP/AlGaInP quantum wells as the gain medium. Placing a planar metal reflector under the cavity can enhance radiation and extraction efficiencies or increase the Q, without incurring additional metallic absorption loss. We show that the far-field radiation characteristics are strongly affected by the devices' immediate surroundings, such as changes in metal cladding thickness, even as the resonant mode profile, frequency, and Q remain the same. When the metal cladding is 1 mm thick, light radiates upward with a distinct intensity maximum at 45° when the cladding is 100 nm thick, the emitted light spreads in a near-horizontal direction.