Envelope Variations Research Articles

Optimized Single-Shot Photonic Time-Stretch Digitizer Using Complementary Parallel Single-Sideband Modulation Architecture and Digital Signal Processing

A novel single-shot photonic time-stretch digitizer scheme is proposed based on complementary parallel single-sideband modulation architecture. Successive digital signal processing, including linearization operation and phase compensation, is employed to improve the performance. Both theoretical analysis and simulation results show that the proposed scheme can simultaneously solve the three vital problems in the single-shot photonic time-stretch digitizers, i.e., removal of the dynamic pulse envelope variation, the dispersion-induced penalty, and suppression of the modulation-induced distortion. Hence, the proposed single-shot photonic time-stretch digitizer can overcome the dispersion-induced bandwidth limitation and realize linearization performance.

Upper ocean O2 trends: 1958–2015

AbstractHistoric observations of dissolved oxygen (O2) in the ocean are analyzed to quantify multidecadal trends and variability from 1958 to 2015. Additional quality control is applied, and the resultant oxygen anomaly field is used to quantify upper ocean O2 trends at global and hemispheric scales. A widespread negative O2 trend is beginning to emerge from the envelope of interannual variability. Ocean reanalysis data are used to evaluate relationships with changes in ocean heat content (OHC) and oxygen solubility (O2,sat). Global O2 decline is evident after the 1980s, accompanied by an increase in global OHC. The global upper ocean O2 inventory (0–1000 m) changed at the rate of −243 ± 124 T mol O2 per decade. Further, the O2 inventory is negatively correlated with the OHC (r = −0.86; 0–1000 m) and the regression coefficient of O2 to OHC is approximately −8.2 ± 0.66 nmol O2 J−1, on the same order of magnitude as the simulated O2‐heat relationship typically found in ocean climate models. Variability and trends in the observed upper ocean O2 concentration are dominated by the apparent oxygen utilization component with relatively small contributions from O2,sat. This indicates that changing ocean circulation, mixing, and/or biochemical processes, rather than the direct thermally induced solubility effects, are the primary drivers for the observed O2 changes. The spatial patterns of the multidecadal trend include regions of enhanced ocean deoxygenation including the subpolar North Pacific, eastern boundary upwelling systems, and tropical oxygen minimum zones. Further studies are warranted to understand and attribute the global O2 trends and their regional expressions.

Speckle affected fringe detection based on three envelope extraction for self-mixing displacement measurement

Speckle is an especially relevant issue as far as self-mixing interferometry works onto diffusive targets and for large displacements sensing. This article proposed a new signal processing technique, based on three envelope extraction transition detection algorithm, to correctly extract and processes self-mixing signals corrupted by speckle. The algorithm also discriminates the direction of the target movement for different self-mixing regimes. The validity of the proposed method was demonstrated by means of simulated signals and confirmed by several experimental measurements with envelope variation of a decade in amplitude. The use of this technique effectively removes the need for optical/electro-mechanical component and strict sampling number determination.

Wavelet modulation: An alternative modulation with low energy consumption

This paper presents wavelet modulation, based on the discrete wavelet transform, as an alternative modulation with low energy consumption. The transmitted signal has low envelope variations, which induces a good efficiency for the power amplifier. Wavelet modulation is analyzed and compared for different wavelet families with orthogonal frequency division multiplexing (OFDM) in terms of peak-to-average power ratio (PAPR), power spectral density (PSD) properties, and the impact of the power amplifier on the spectral regrowth. The performance in terms of bit error rate and complexity of implementation are also evaluated, and several trade-offs are characterized.

Spectral Envelope Transformation in Singing Voice for Advanced Pitch Shifting

The aim of the present work is to perform a step towards more natural pitch shifting techniques in singing voice for its application in music production and entertainment systems. In this paper, we present an advanced method to achieve natural modifications when applying a pitch shifting process to singing voice by modifying the spectral envelope of the audio excerpt. To this end, an all-pole model has been selected to model the spectral envelope, which is estimated using a constrained non-linear optimization. The analysis of the global variations of the spectral envelope was carried out by identifying changes of the parameters of the model along with the changes of the pitch. With the obtained spectral envelope transformation functions, we applied our pitch shifting scheme to some sustained vowels in order to compare results with the same transformation made by using the Flex Pitch plugin of Logic Pro X and pitch synchronous overlap and add technique (PSOLA). This comparison has been carried out by means of both an objective and a subjective evaluation. The latter was done with a survey open to volunteers on our website.

Reconstruction of Ob River, Russia, discharge from ring widths of floodplain trees

The Ob is the third largest Eurasian river supplying heat and freshwater to the Arctic Ocean. These inputs influence water salinity, ice coverage, ocean temperatures and ocean circulation, and ultimately the global climate system. Variability of Ob River flow on long time scales is poorly understood, however, because gaged flow records are short. Eleven tree-ring width chronologies of Pinus sibirica and Larix sibirica are developed from the floodplain of the Lower Ob River, analyzed for hydroclimatic signal and applied as predictors in a regression model to reconstruct 8-month average (December-July) discharge of the Ob River at Salekhard over the interval 1705–2012 (308yrs). Correlation analysis suggests the signal for discharge comes through air temperature: high discharge and floodplain water levels favor cool growing-season air temperature, which limits tree growth for the sampled species at these high latitudes. The reconstruction model (R2=0.31, 1937–2009 calibration period) is strongly supported by cross-validation and analysis of residuals. Correlation of observed with reconstructed discharge improves with smoothing. The long-term reconstruction correlates significantly with a previous Ob River reconstruction from ring widths of trees outside the Ob River floodplain and extends that record by another century. Results suggest that large multi-decadal swings in discharge have occurred at irregular intervals, that variations in the 20th and 21st centuries have been within the envelope of natural variability of the past 3 centuries, and that discharge data for 1937–2009 underestimate both the variability and persistence of discharge in the last 3 centuries. The reconstruction gives ecologists, climatologists and water resource planners a long-term context for assessment of climate change impacts.

Fully-integrated bias control feed-back loop for efficiency enhancement of mmWave CMOS power amplifier

A single-stage mmWave class-A CMOS power amplifier (PA) is fabricated in a BiCMOS 55 nm technology. In order to improve the power added efficiency (PAE) behavior of the PA, a bias-control feedback loop is fully implemented on-chip in order to dynamically adjust the DC bias current of the PA according to RF envelope power level. A tunable envelope detector is connected directly at the output of the amplifier in order to track the envelope variations of the output signal. Under constant bias conditions, the PA has a power gain (Gp) of 4.2 dB, a maximum PAE of 14 %, and an output compression point of around 7.5 dBm while driving 25 mA under 1.2 V supply voltage. In adaptive bias mode, the mean value of the DC current is reduced down to 20.8 mA, while holding the same Gp, leading to a good enhancement of the PAE over the linear input dynamic range of the PA. Simulations and measurements with a modulated 16-QAM 700 MHz input signal show that the applied technique improves the average PAE and DC power consumption by 17 % (relative to is nominal value) without significant degradation of the signal quality. For our best knowledge, the measurements with modulated signal are the first to be done on a dynamically biased mmWave PA.

First study of complete genome of Dengue-3 virus from Rajasthan, India: genomic characterization, amino acid variations and phylogenetic analysis

First study on the complete genome characterization of Dengue-3 virus is reported from dengue endemic state Rajasthan, India. The genome of 10,672 base pairs was studied with reference to global and the regional genomes of Dengue-3 virus. 388 variations were observed in the nucleotide sequences with reference to the NCBI genome, including 34 variations in the amino acids. Of these 34 AA variations, 4 variations showed AA substitution in Envelope proteins and 1 in Anchored capsid region. The remaining 29 variations were observed in amino acids constituting non structural (NS) proteins. The reported mutations, especially those leading to amino acid variations in non-structural proteins of virus may influence the clinical profile of patients and accuracy of ongoing diagnostic tests. Reported amino acid variations in virus envelope may influence the immune response of patients. Phylogenetic studies showed similarity of reported genome with genomes from India, Pakistan and China.

Energy performance analysis of variable reflectivity envelope systems for commercial buildings

This paper evaluates potential energy savings associated with variable reflectivity envelope systems (VRCs) including cool roofs associated the application of coatings that can change their reflective properties over time depending on outdoor conditions and desired controlled strategies. It is well known that static cool roofs can save energy use during cooling periods but may increase energy consumption during swing or heating seasons due to lower beneficial heat gains. In the analysis, a two-step control strategy is considered to modify the properties of the cool roof coatings based on the temperature difference between internal and external roof surfaces. Using a simulation environment capable of modeling variable properties of outer surface of building envelope, a comparative analysis is carried out to evaluate the impact of VRCs on the heating and cooling energy end-uses for commercial buildings in four US climates. It is observed that VRCs can save heating energy use compared to static cool roofs for all four US climates for both commercial buildings. In particular, it is found that VRCs have the potential to reduce annual energy use in commercial buildings up to 11% compared to the static cool roofs.

Calculation of sound radiation in infinite domain using a meshless method

A meshless method coupling with a variable order infinite acoustic wave envelope element for sound radiation calculation in infinite domain is presented with the aim of accurately calculating the acoustic radiation and improving computational efficiency. It is based on using the element-free Galerkin method in the inner region enclosing the radiator and a variable order infinite acoustic wave envelope element in the outer region for the proper modeling of the pressure amplitude decay. The details are provided for the derivation and implementation of this method. The factors of influencing the performance of the method, which include the shape function constructing, the number of integration points, the weight functions, and the support domain, are discussed. A hybrid adaptive Gauss-Legendre quadrature is devised to obtain good integration accuracy. The suitable radius of the support domain for the acoustic field calculation in free space is also determined by use of numerical experiments. A complex structure is designed for simulation to validate the method. The results illustrate the accuracy, applicability, and effectiveness of this method.

Projections of the shifting envelope of Water cycle variability

The time of departure of water cycle variables from historical climatic conditions is quantified from multi-model suites of climate change simulations. Two thresholds are examined: the historical (1860–2005) mean and the range of variability during that same period. The metric is the year when the future range of variability in RCP4.5 and RCP8.5 moves permanently above or below the historical mean for seasonal average values of precipitation, runoff and surface soil moisture. There is a large range of inter-model variability, so both multi-model means of the year of departure and the fraction of models exceeding thresholds by the end of the 21st century are calculated. There is a strong tendency for transition to wetter winter conditions at high northern latitudes for precipitation, but a predominance of dry departures in JJA, with a slight tendency for positive departures in precipitation when considered globally across the year. For runoff there are approximately equal areas of permanently wetter and drier conditions, but runoff is the most sensitive term with the largest areas of departure early in the 21st century, and the greatest propensity to move outside the historical range of variability. Soil moisture trends are predominantly negative with large regions shifting to permanently drier conditions. For all three variables there is a clear increase over time in the total area becoming permanently wetter or drier than the historical mean. The termination of many models’ simulations at 2100, often before permanent transitions are reached, affects the calculations, leading to earlier transition dates than if simulations are extended.

Optical spectrum variations of IL Cep A

The results of many-year uniform spectroscopic observations of the Herbig Ae/Be star IL Cep A are presented. Its Hα line has either a single or a barely resolved two-component emission profile. The Hβ emission line is clearly divided into two components with a deep central absorption. Smooth variations of the observed parameters of individual spectral lines over nine years are observed. The He I λ5876 A line has a complex absorption profile, probably with superposed emission components. The NaI D1, D2 doublet exhibits weak changes due to variations in the circumstellar envelope. The variations observed in the stellar spectrum can be explained by either binarity or variations of the magnetic field in the stellar disk. Difficulties associated with both these possibilities are discussed.

Simulation of the Thermal Behaviour of a Building Retrofitted with a Green Roof: Optimization of Energy Efficiency with Reference to Italian Climatic Zones

Abstract Running a building energy simulation program (EnergyPlus), simulations were conducted on a ‘public housing’ building type, in order to evaluate the energy savings achieved by a green roof coupled with different configurations of external wall. EnergyPlus enabled the investigation of the thermal behaviour variations of the building envelope, and the possible consequences, in terms of comfort, on the temperature of the internal spaces. The variation of the energy behaviour of the building envelope type was assessed primarily through the analysis of the operative temperature T ° of the elements of surface casing, the trend of the surface heat fluxes on the faces of the elements of internal and external housing, the variation of the operating temperature inside the rooms. The energy savings achieved with a green roof varies considerably in relation to the reference performance obtained without this kind of insulating structure. The main parameters, useful to define the contribution of the green roof to the reduction of the loads of cooling plants, consist of the specific climate and the thermal isolation level of the initial coverage.

Glacier response to North Atlantic climate variability during the Holocene

Abstract. Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of the cryosphere. The data provide a longer-term perspective on the rate of 20th century glacier retreat and indicate that recent anthropogenic-driven warming has already impacted the regional cryosphere in a manner outside the natural range of Holocene variability.

The study of burst pulses envelope in Ytterbium-doped fiber amplifier modulating by pulsed pump source

The characteristics of fiber amplifiers of burst pulses envelope during the propagation are comprehensively studied under the conditions of pulsed pump with low repetition rate. The variation of signal envelopes, pump power and upper-level population distribution are discussed in this paper. The impacts of linear varied and exponential varied pump to the raising edge and tailing edge of the output pulses' envelope, are mainly emphasized. Finally, the genetic algorithm is employed to reshape the pulses' envelopes.

Moments Of Microdiversity EGC Receivers And Macrodiversity SC Receiver Output Signal Over Gamma Shadowed Nakagami–m Multipath Fading Channel

Abstract A system with macrodiversity selection combining (SC) receiver and for microdiversity equal gain combining (EGC) receivers is considered. Received signal is subjected, simultaneously to multipath fading and shadowing, resulting in signal envelope and signal power variation. Closed form expressions for moments of macrodiversity SC receiver output signal envelope are calculated. Numerical expressions are plotted to present the influences of Gamma shadowing severity and Nakagami-m severity on moments of proposed system output signal.

Low PMEPR OFDM Radar Waveform Design Using the Iterative Least Squares Algorithm

This letter considers waveform design of orthogonal frequency division multiplexing (OFDM) signal for radar applications, and aims at mitigating the envelope fluctuation in OFDM. A novel method is proposed to reduce the peak-to-mean envelope power ratio (PMEPR), which is commonly used to evaluate the fluctuation. The proposed method is based on the tone reservation approach, in which some bits or subcarriers of OFDM are allocated for decreasing PMEPR. We introduce the coefficient of variation of envelopes (CVE) as the cost function for waveform optimization, and develop an iterative least squares algorithm. Minimizing CVE leads to distinct PMEPR reduction, and it is guaranteed that the cost function monotonically decreases by applying the iterative algorithm. Simulations demonstrate that the envelope is significantly smoothed by the proposed method.

Eliminating Light Intensity Disturbance With Reference Compensation in Interferometers

In this letter, we introduce an improved phase-generated carrier (PGC) demodulation algorithm using reference compensation method to eliminate the influence of light intensity disturbance (LID) in interferometric fiber-optic sensors. In this method, the impacts of LID on acoustic signal and reference signal are the same. The impact of LID on reference signal can be measured via calculating the envelope variation of demodulated reference signal. Then, the impact of LID on acoustic signal is divided off through reference compensation. The improved PGC demodulation algorithm with merit of resisting LID was experimentally demonstrated. The signal-to-noise ratio of demodulation result based on the improved PGC algorithm achieves a gain of 11.78 dB over PGC algorithm using differential-cross-multiplying.

Climate and carbon cycle dynamics in a CESM simulation from 850 to 2100 CE

Abstract. Under the protocols of phase 3 of the Paleoclimate Modelling Intercomparison Project, a number of simulations were produced that provide a range of potential climate evolutions from the last millennium to the end of the current century. Here, we present the first simulation with the Community Earth System Model (CESM), which includes an interactive carbon cycle, that covers the last millennium. The simulation is continued to the end of the twenty-first century. Besides state-of-the-art forcing reconstructions, we apply a modified reconstruction of total solar irradiance to shed light on the issue of forcing uncertainty in the context of the last millennium. Nevertheless, we find that structural uncertainties between different models can still dominate over forcing uncertainty for quantities such as hemispheric temperatures or the land and ocean carbon cycle response. Compared to other model simulations, we find forced decadal-scale variability to occur mainly after volcanic eruptions, while during other periods internal variability masks potentially forced signals and calls for larger ensembles in paleoclimate modeling studies. At the same time, we were not able to attribute millennial temperature trends to orbital forcing, as has been suggested recently. The climate–carbon-cycle sensitivity in CESM during the last millennium is estimated to be between 1.0 and 2.1 ppm °C−1. However, the dependence of this sensitivity on the exact time period and scale illustrates the prevailing challenge of deriving robust constraints on this quantity from paleoclimate proxies. In particular, the response of the land carbon cycle to volcanic forcing shows fundamental differences between different models. In CESM the tropical land dictates the response to volcanoes, with a distinct behavior for large and moderate eruptions. Under anthropogenic emissions, global land and ocean carbon uptake rates emerge from the envelope of interannual natural variability by about year 1947 and 1877, respectively, as simulated for the last millennium.

On the Frontline: Tracking Ocean Acidification in an Alaskan Shellfish Hatchery

The invasion of anthropogenic carbon dioxide (CO2) into the ocean is shifting the marine carbonate system such that saturation states of calcium carbonate (CaCO3) minerals are decreasing, and this is having a detrimental impact on early life stages of select shellfish species. The global, secular decrease in CaCO3 saturation states is occurring on top of a backdrop of large natural variability in coastal settings; progressively shifting the envelope of variability and leading to longer and more frequent exposure to adverse conditions. This is a great concern in the State of Alaska, a high-latitude setting vulnerable to rapid changes in the marine carbonate system, where an emerging shellfish industry plans major growth over the coming decades. Currently, the Alutiiq Pride Shellfish Hatchery (APSH) in Seward, Alaska is the only hatchery in the state, and produces many shellfish species with early life stages known to be sensitive to low CaCO3 saturation states. Here we present the first land-based OA measurements made in an Alaskan shellfish hatchery, and detail the trends in the saturation state of aragonite (Ωarag), the more soluble form of CaCO3, over a 10-month period in the APSH seawater supply. These data indicate the largest changes are on the seasonal time scale, with extended periods of sub-optimal Ωarag levels (Ωarag < 1.5) in winter and autumn associated with elevated water column respiration and short-lived runoff events, respectively. The data pinpoint a 5-month window of reprieve with favorable Ωarag conditions above the sub-optimal Ωarag threshold, which under predicted upper-bound CO2 emissions trajectories is estimated to close by 2040. To date, many species in production at APSH remain untested in their response to OA, and the data presented here establish the current conditions at APSH as well as provide a framework for hatchery-based measurements in Alaska. The current and expected conditions seen at APSH are essential to consider for this developing Alaskan industry.