Gain Increments Research Articles

Adaptive control to actively damp bistabilities in highly interrupted turning processes using a hardware-in-the-loop simulator

Interruptions in turning make the process forces non-smooth and nonlinear. Smooth nonlinear cutting forces result in the process of being stable for small perturbations and unstable for larger ones. Re-entry after interruptions acts as perturbations making the process exhibit bistabilities. Stability for such processes is characterized by Hopf bifurcations resulting in lobes and period-doubling bifurcations resulting in narrow unstable lenses. Interrupted turning remains an important technological problem, and since experimentation to investigate and mitigate instabilities are difficult, this paper instead emulates these phenomena on a controlled hardware-in-the-loop simulator. Emulated cutting on the simulator confirms that bistabilities persist with lobes and lenses. Cutting in bistable regimes should be avoided due to conditional stability. Hence, we demonstrate the use of active damping to stabilize cutting with interruptions/perturbations. To stabilize cutting with small/large perturbations, we successfully implement an adaptive gain tuning scheme that adapts the gain to the level of interruption/perturbation. To facilitate real-time detection of instabilities and their control, we characterize the efficacy of the updating scheme for its dependence on the time required to update the gain and for its dependence on the levels of gain increments. We observe that higher gain increments with shorter updating times result in the process being stabilized quicker. Such results are instructive for active damping of real processes exhibiting conditional instabilities prone to perturbations.

Vitamin D Status of Very Low Birth Weight Neonates at Baseline and Follow-up after Daily Intake of 800 IU Vitamin D.

Vitamin D deficiency (VDD) is rampant in neonates. Recommendations for supplementation are variable. An observational study was done on less than 32 weeks of very low birth weight neonates to find prevalence of VDD (<20 ng/ml) at baseline; at 38 ± 2 weeks post-menstrual age (PMA) after daily intake of 800 IU vitamin D (vit D). Secondary objectives were to find determinants of VDD, to compare growth in deficient; vit D sufficient (VDS) neonates; to find vit D toxicity. Of 83 neonates, 81 (97.6%) were VDD at baseline and 5 (6%) at 38 ± 2 weeks PMA. Determinants for VDD at baseline were inadequate maternal sun exposure (p < 0.001) and vit D supplementation (p = 0.007). Factors for VDD at 38 ± 2 weeks PMA were male gender (p = 0.049), morbidities (p = 0.006), ventilation >24 h (<0.001), sepsis (p = 0.032), caffeine (p ≤ 0.001) and missed supplements (p < 0.001). Weight and length gain of VDD to VDS neonates were (6.70 ± 2.40 to 8.96 ± 2.21 g/day); (0.82 ± 0.34 to 1.08 ± 0.37 cm/week), respectively (p < 0.001). Head circumference gain (cm/week) of VDS; VDD neonates was 0.58 ± 0.09; 0.54 ± 0.06 (p = 0.054), respectively. No neonates developed vit D toxicity. In preterm VLBW neonates, the prevalence of VDD was 97.6% but decreased by >90% at 38 ± 2 weeks with a daily intake of 800 IU vit D. Inadequate maternal vit D intake and sun exposure determined low baseline vit D status of neonates. Male gender, morbidities, ventilation, sepsis, caffeine, missed vitamin D supplements were determinants of poor vit D status at follow-up. Weight gain and length increments were more in the VDS group.

Assessment of sowing dates and plant densities using CSM-CROPGRO-Soybean for soybean maturity groups in low latitude

AbstractCrop models can be used to explain yield variations associated with management practices, environment and genotype. This study aimed to assess the effect of plant densities using CSM-CROPGRO-Soybean for low latitudes. The crop model was calibrated and evaluated using data from field experiments, including plant densities (10, 20, 30 and 40 plants per m2), maturity groups (MG 7.7 and 8.8) and sowing dates (calibration: 06 Jan., 19 Jan., 16 Feb. 2018; and evaluation: 19 Jan. 2019). The model simulated phenology with a bias lower than 2 days for calibration and 7 days for evaluation. Relative root mean square error for the maximum leaf area index varied from 12.2 to 31.3%; while that for grain yield varied between 3 and 32%. The calibrated model was used to simulate different management scenarios across six sites located in the low latitude, considering 33 growing seasons. Simulations showed a higher yield for 40 pl per m2, as expected, but with greater yield gain increments occurring at low plant density going from 10 to 20 pl per m2. In Santarém, Brazil, MG 8.8 sown on 21 Feb. had a median yield of 2658, 3197, 3442 and 3583 kg/ha, respectively, for 10, 20, 30 and 40 pl per m2, resulting in a relative increase of 20, 8 and 4% for each additional 10 pl per m2. Overall, the crop model had adequate performance, indicating a minimum recommended plant density of 20 pl per m2, while sowing dates and maturity groups showed different yield level and pattern across sites in function of the local climate.

One-Dimensional Beam Scanning Transmitarray Lens Antenna Fed by Microstrip Linear Array

This paper proposed a one-dimensional beam scanning transmitarray lens antenna fed by a microstrip linear array antenna which owns a wide pattern in the plane orthogonal to the array axis and a narrow pattern in the plane that includes the array axis. The design principle of transmitarray lens aims to modulate a fan beam into a pencil beam by compensating phase shift of the linear array on the plane orthogonal to the array axis at X band. First, the Rotman lens feed network is used to implement nearly ±40° one-dimensional beam scanning for the linear array with 1 × 8 microstrip antenna elements. Then, a lowprofile transmitted element with only one-layer of the substrate is utilized to design the new transmitarray lens, which can reduce fabrication expense and difficulties. After adding the transmitarray lens, maximum gain increments of 7.81 and 7.65 dB in simulation and measurement can be obtained in quasi-boresight directions, and gain increment could be obtained within ±25° beam scanning range. Besides, the fan beams of the original linear array are smoothly transformed into pencil beams.

Discrimination of Gain Increments in Speech.

During a hearing-aid fitting, the gain applied across frequencies is often adjusted from an initial prescription in order to meet individual needs and preferences. These gain adjustments in one or more frequency bands are commonly verified using speech in quiet (e.g., the clinician’s own voice). Such adjustments may be unreliable and inefficient if they are not discriminable. To examine what adjustments are discriminable when made to speech, this study measured the just-noticeable differences (JNDs) for gain increments in male, single-talker sentences. Sentences were presented with prescribed gains to the better ears of 41 hearing-impaired listeners. JNDs were measured at d’ of 1 for octave-band, dual-octave-band, and broadband increments using a fixed-level, same-different task. The JNDs and interquartile ranges for 0.25, 1, and 4 kHz octave-band increments were 6.3 [4.0–7.8], 6.7 [4.6–9.1], and 9.6 [7.3–12.4] dB, respectively. The JNDs and interquartile ranges for low-, mid-, and high-frequency dual-octave-band increments were 3.7 [2.5–4.6], 3.8 [2.9–4.7], and 6.8 [4.7–9.1] dB, respectively. The JND for broadband increments was 2.0 [1.5–2.7] dB. High-frequency dual-octave-band JNDs were positively correlated with high-frequency pure-tone thresholds and sensation levels, suggesting an effect of audibility for this condition. All other JNDs were independent of pure-tone threshold and sensation level. JNDs were independent of age and hearing-aid experience. These results suggest using large initial adjustments when using short sentences in a hearing-aid fitting to ensure patient focus, followed by smaller subsequent adjustments, if necessary, to ensure audibility, comfort, and stability.

Discrimination of Gain Increments in Speech-Shaped Noises.

Frequency-dependent gain adjustments are routine in hearing-aid fittings, whether in matching to real-ear targets or fine-tuning to patient feedback. Patient feedback may be unreliable and fittings inefficient if adjustments are not discriminable. To examine what gain adjustments are discriminable, we measured the just-noticeable differences (JNDs) for level increments in speech-shaped noises processed with prescription gains. JNDs were measured in the better ears of 38 participants with hearing impairment using a fixed-level, same-different task. JNDs were measured for increments at six individual frequency-bands: a 0.25-kHz low-pass band; octave-wide bands at 0.5, 1, 2, and 4 kHz; and a 6-kHz high-pass band. JNDs for broadband increments were also measured. JNDs were estimated at d’ of 1 for a minimally discriminable increment in optimal laboratory conditions. The JND for frequency-band increments was 2.8 dB excluding the 0.25-kHz low-pass band, for which the JND was 4.5 dB. The JND for broadband increments was 1.5 dB. Participants’ median frequency-band and broadband JNDs were positively correlated. JNDs were mostly independent of age, pure-tone thresholds, and cognitive score. In consideration of self-fitting adjustments in noisier conditions, JNDs were additionally estimated at a more sensitive d’ of 2. These JNDs were 6 dB for bands below 1 kHz, and 5 dB for bands at and above 1 kHz. Overall, the results suggest noticeable fine-tuning adjustments of 3 dB and self-fitting adjustments of 5 dB.

MEANDER-LINE BASED BROADBAND ARTIFICIAL MATERIAL FOR ENHANCING THE GAIN OF PRINTED END-FIRE ANTENNA

A broadband artificial material based on meander-line (ML) structures is proposed for enhancing the gain of printed end-fire antennas. The ML based material with an effective index of refraction greater than 1 behaves as a dielectric lens in improving the directivity of an end-fire antenna. The electric field intensity distribution can be changed by the material, resulting in a more directional emission. Simulated results indicate extending the length or width of the material can lead to more significant gain enhancement without destroying the impedance bandwidth of the antenna. Three printed end-fire antennas with and without material loading are fabricated and measured. The measurements show that end-fire antennas loaded with two and four rows of ML structures can obtain gain increments of 0.6-3.6 dB and 1.2-5.7 dB, respectively, and that the radiation patterns are narrowed in both E -a ndH-planes over the whole operating band (6-11.5 GHz).

Abstract 3149: Greater Fluid Retention is Associated with Increased Cardiovascular Death Risk in 34,003 CKD Patients on Hemodialysis

Background: Patients with chronic kidney disease (CKD) stage 5 who undergo hemodialysis (HD) treatment have striking similarities to heart failure (HF) patients, in that both populations retain fluid frequently, have excessively high mortality, and exhibit an obesity paradox. We hypothesized that in HD patients greater interdialytic fluid retention is associated with poor cardiovascular (CV) survival. Methods: We examined the 2-year (7/2001– 6/2003) CV mortality in 34,003 HD patients across the United States, who had an averaged weight gain of at least 0.5 kg above their end-dialysis dry weight by the time the subsequent HD treatment started. The 3-month averaged interdialytic weight gain was divided into 8 categories of 0.5 kg increments (up to &gt;= 4.0 kg). Results : In unadjusted analyses, higher weight gains were associated with better nutritional status (higher protein intake, serum albumin and body mass index) and tended to be linked to greater survival. However after multivariate adjustment for demographics (case-mix) and also surrogates of malnutrition-inflammation-cachexia syndrome (MICS), higher weight gain increments were associated with increased CV death risk. [Figure ] Conclusions: In HD patients greater fluid retention between two subsequent HD treatment sessions is associated with higher CV death risk. The mechanisms by which fluid retention influences survival in HD may be similar to HF patients and warrants further research.

Dynamics of pulses in optically coupled active optical fibres with different parameters

The dynamics of a wave packet formed by two modes propagating in optically coupled channels with different mode gain increments is studied. It is shown that in the case of a linear intermode coupling, radiation in such structures is decomposed into two autonomous partial pulses with different values of the effective dispersion parameters determining their dynamics. The conditions of the temporal compression and realisation of the superluminal velocity of the envelope maximum for partial pulses and the wave packet as a whole are also investigated.

Picosecond stimulated Raman scattering in crystals

The comparative values of the peak and integral cross sections of spontaneous Raman scattering and the optical dephasing time of molecular vibrations were determined for several oxide crystals by spontaneous Raman spectroscopy. The spectral, time, and energy parameters of stimulated Raman scattering (SRS) were measured for ten crystals using picosecond YLF: Nd laser pumping with a radiation wavelength of 1047 nm. An analysis of the experimental dependence of the threshold energy of pumping SRS on the integral and peak cross sections of spontaneous Raman scattering showed that the SRS gain increment explicitly depended on the integral cross section and was independent of the peak cross section of spontaneous Raman scattering as the ratio between the pumping pulse width (11 ps) and the time of optical dephasing of molecular vibrations changed from 0.42 to 9.3. The gain coefficients of steady-state stimulated Raman scattering under threshold stimulated Raman scattering conditions were determined for all the crystals studied on the basis of the measured threshold SRS pumping energies, the duration and width of the spectrum of pulses, the nonlinear interaction length, the intensity of pumping, and the theoretical dependences that relate the steady-state and transient SRS gain increments. The steady-state SRS gain coefficients obtained in this work fitted well a linear dependence on the peak cross sections of spontaneous Raman scattering, which substantiated the correctness of our analysis and measurements.

Association between supine hypertension and orthostatic hypotension in autonomic failure.

Supine hypertension occurs commonly in primary chronic autonomic failure. This study explored whether supine hypertension in this setting is associated with orthostatic hypotension (OH), and if so, what mechanisms might underlie this association. Supine and upright blood pressures, hemodynamic responses to the Valsalva maneuver, baroreflex-cardiovagal gain, and plasma norepinephrine (NE) levels were measured in pure autonomic failure (PAF), multiple-system atrophy (MSA) with or without OH, and Parkinson's disease (PD) with or without OH. Controls included age-matched, healthy volunteers and patients with essential hypertension or those referred for dysautonomia. Baroreflex-cardiovagal gain was calculated from the relation between the interbeat interval and systolic pressure during the Valsalva maneuver. PAF, MSA with OH, and PD with OH all featured supine hypertension, which was equivalent in severity to that in essential hypertension, regardless of fludrocortisone treatment. Among patients with PD or MSA, those with OH had higher mean arterial pressure during supine rest (109+/-3 mm Hg) than did those lacking OH (96+/-3 mm Hg, P=0.002). Baroreflex-cardiovagal gain and orthostatic increments in plasma NE levels were markedly decreased in all 3 groups with OH. Among patients with PD or MSA, those with OH had much lower mean baroreflex-cardiovagal gain (0.74+/-0.10 ms/mm Hg) than did those lacking OH (3.13+/-0.72 ms/mm Hg, P=0.0002). In chronic autonomic failure, supine hypertension is linked to both OH and low baroreflex-cardiovagal gain [corrected]. The finding of lower plasma NE levels in patients with than without supine hypertension suggests involvement of pressor mechanisms independent of the sympathetic nervous system.

Magneto-acoustic ceramics for parametric sound wave phase conjugators

The paper reflects the recent experimental results on the elaboration and study of active materials for magneto-acoustic phase conjugators (MAPCs). The results of complex measurements of MAPC parameters are demonstrated on typical samples of NiFe 2O 4 magnetostrictive ceramics. The mechanism of strong dispersion of gain increments and output power of MAPCs is studied and explained by dispersion of critical values of the parametric modulation depth of sound velocity. A maximum output power 240 W at frequency 5 MHz is obtained for active element MAPC with critical current I c=9 A and electrical Q-factor equal to 80.

Influence of the addition of fish meal to diets of roughage or roughage and concentrate on the consumption and live-weight gain of growing cattle

Two feeding trials were carried out to evaluate the influence of the addition of fish meal (F) to diets based on two tropical roughages of different nutritive value supplemented or not with a rumen degradable concentrate (C), on the intake and live-weight (LW) gain of growing cattle. A factorial 2 × 2 arrangement was used with the following treatments: zero or 300 g day −1 F supplementing diets of roughage or roughage plus 1.0 kg day −1 C. Twenty 190 kg Brahman × Holstein animals were used in each experiment over 12 or 11 week periods with basal diets of fresh forage or sorghum silage. The consumption of forage and silage in control treatments without supplements were 25.8 and 15.1 g kg −1 LW, the crude protein (CP) contents were of 81 and 69 g kg −1 dry matter (DM) and DM disappearances in nylon bags at 48 h (DMD48h) were of 579 and 400 g kg −1 DM. The N degradability of concentrate and fish meal were 0.88 and 0.36. Another two trials were carried out with rumen-fistulated animals to evaluate the influence of these supplements on some parameters of rumen digestion. It was found that forage DMD48h was slightly decreased and its rate of digestion in nylon bags was reduced ( P < 0.05) with F, but not with C. In the feeding trials F slightly increased ( P > 0.05) silage intake and decreased forage consumption, and the LW gain responses to this supplement varied with the quality of the roughage. They were higher with the silage of lower quality than with the forage, with increments of 0.33 and 0.16 kg day −1, respectively. These responses were very similar for each roughage given alone or supplemented with concentrate. LW gain was appreciably increased by F and C in both trials ( P < 0.01), but the magnitude of the responses per unit supplement was different between sources and roughages. LW gain increments were 50 and 108 g per 100 g F with forage and low quality silage, and 33 per 100 g C with both roughages. These results indicate that LW gain response to fish meal is very large with low quality tropical forages, and as its quality improves this response is appreciably reduced and tends to be similar to those obtained with concentrates based in degradable sources of nitrogen.

Polarization characteristics of a noncoplanar concurrent four-wave interaction in resonant media

An analysis is made of a noncoplanar concurrent four-wave interaction in the field of linearly polarized pump waves in resonant media modeled by linear (or circular) dipoles. The parametric gain increments and the polarization of weak radiation are determined, in the cubic approximation, as a function of the polarization characteristics of the waves being mixed and of the properties of the resonant medium. In the case of orthogonally polarized pump waves the polarization of the signal is conserved irrespective of the model adopted for a resonant medium and the polarization of a diffracted wave is reversed relative to the signal. In the case of parallel orientation of the pump wave vectors the polarization of a linearly polarized signal is retained if the vector of its amplitude is oriented parallel or orthogonal to the pump waves. In a medium modeled by an ensemble of randomly oriented dipoles when the angle between the pump wave vectors is 2π/3 or π/3 the radiation is linearly polarized irrespective of the polarization structure of the input signal.

The structure of the Stokes' fields reflected in SBS in a light guide

The calculation of gain increments and the spatial structure of the scattered Stokes' radiation is carried out on the basis of a proposed theoretical method. The so-called rotated modes are shown to be trapped into a spatial resonance with the central reversed mode. These spatial configurations are discovered experimentally with the help of an interferometer with wavefront-reversing mirrors based on stimulated Brillouin scattering. The rotated modes are concentrated in a so-called 'background pedestal' for which the divergence theta /sub b/ increases with the gain increment at the longitudinal correlation length Gamma /sub c/. For a fixed Gamma /sub c/ the relationship between the energy of the Stokes' signal reproducing exactly the spatial structure of the pump radiation and the energy of the background pedestal varies randomly from one laser pulse to another, resulting in a strong dispersion of the energy of the Stokes' waves measured in both interferometer arms.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Influence of the spatial phase locking on amplification of pump-correlated Stokes fields in stimulated Brillouin scattering in a light guide

A theoretical method is proposed and used to calculate the gain increments and the spatial structure of scattered Stokes radiation. An allowance is made for distortions of two types: pump-uncorrelated noise and what are called rotated modes. It is shown that the latter are locked in a spatial resonance with the central reversed (phase-conjugated) mode. Such locking can occur in phase and in antiphase, with corresponding increments higher and lower than the Gaussian value of 2. The quality of wavefront reversal is estimated for a typical experimental situation.

Brillouin reversal of optical fields with a time-dependent speckle structure

An analysis is made of stimulated backscattering in the case when the pump (laser) radiation has a continuous frequency spectrum and a time-dependent (nonfactorizable) speckle structure. The gain increments μ(p) and the corresponding specklon solution for a Stokes wave are found in the case of an arbitrary ratio of the widths of the pump line Δωl, and of the stimulated scattering line Γ. These solutions correspond to partial wavefront reversal, i.e., to reversal of the spectral band of the pump radiation within an interval of width of the order of Γ/2 around a certain frequency p. A comparison of the specklon gain increments with the increments for uncorrelated waves makes it possible to determine the conditions for wavefront reversal.

Investigation of the forward and backward scattering of spatially noncoherent pump radiation

A new method developed by the authors for the analysis of stimulated scattering of spatially noncoherent radiation is used in a comparative study of the concurrent and opposed interactions of a Stokes field with pump radiation. If there is no correlation between the Stokes and pump waves, the interaction is independent of the relative direction of propagation of the waves. However, if the Stokes and pump waves are correlated, the interaction efficiency depends strongly on the relative directions of the waves. Exact expressions are obtained for the structure of the wave fields and gain increments in the backscattering case and approximate expressions are obtained for the forward scattering. The physical reason for the asymmetry in the amplification is the reproduction by the Stokes signal spectrum of the pump spectrum in the forward scattering case and inversion of this spectrum in the backscattering case. The same reason accounts for a deterioration of the quality of wavefront reversal in the backscattering case compared with the forward scattering.

Gain increments of Stokes fields in stimulated scattering of spatially inhomogeneous radiation

An experimental study was made of the amplification of Stokes components of stimulated Brillouin scattering correlated and uncorrelated with spatially inhomogeneous pump radiation. It was found that the ratio of the gain increments for the correlated and uncorrelated components was 2.0 ±0.2.

Analysis of conditions for stimulated Raman scattering of multimode pump radiation in dispersive media

A theoretical analysis is made of stimulated Raman scattering of multimode pump radiation in a dispersive active medium. Gain increments and the form of the scattered field are determined for arbitrary lengths of active medium and pump intensities.