Showing papers by "Vikram Sarabhai Space Centre published in 2010"

Coastal Vulnerability Assessment for Orissa State, East Coast of India

Abstract: Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asia's largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for othe...

Aerosol temporal characteristics and its impact on shortwave radiative forcing at a location in the northeast of India

Abstract: [1] Measurements of aerosol optical depth (AOD) and mass concentration of composite and black carbon (BC) aerosols made with collocated instruments over Dibrugarh in Northeast India are used to estimate the aerosol radiative forcing for the period June 2008 to May 2009. AOD shows seasonal variation with maximum in premonsoon (0.69 ± 0.13 at 500 nm in March 2009) and minimum in the retreating monsoon (0.08 ± 0.01 at 500 nm in October 2008). Angstrom coefficients α and β are highest in monsoon and premonsoon season and are lowest in premonsoon and retreating monsoon, respectively. The size segregated mass concentration is minimum in the monsoon season for all the three modes nucleation, accumulation, and coarse and maximum in winter for accumulation and coarse and in premonsoon for nucleation mode. The BC mass concentration is highest 16.3 ± 1.4 μg m−3 in winter and lowest 3.4 ± 0.9 μg m−3 in monsoon. The estimated aerosol radiative forcing of the atmosphere, using Optical Properties of Aerosols and Clouds (OPAC) outputs as inputs for Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART), is maximum in premonsoon followed by that in winter and minimum in retreating monsoon. Negative forcing is observed at the surface, whereas the top of the atmosphere (TOA) forcing is nearly zero in retreating monsoon and is negative in rest of the seasons. The forcing efficiency and heating rate were highest during winter and premonsoon, respectively.

First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms

Abstract: [1] The Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft has produced for the first time an image of a lunar magnetic anomaly in backscattered hydrogen atoms The image shows that a partial void of the solar wind, a mini-magnetosphere, is formed above the strong magnetic anomaly near the Crisium antipode The mini-magnetosphere is 360 km across at the surface and is surrounded by a 300-km-thick region of enhanced plasma flux that results from the solar wind flowing around the mini-magnetosphere The mini-magnetosphere is visible only in hydrogen atoms with energy exceeding 150 eV Fluxes with energies below 100 eV do not show corresponding spatial variations While the high-energy atoms result from the backscattering process, the origin of the low-energy component is puzzling These observations reveal a new class of objects, mini-magnetospheres, and demonstrate a new observational technique to study airless bodies, imaging in backscattered neutral atoms

Effect of nanoclay on the mechanical, dynamic mechanical and thermal properties of cyanate ester syntactic foams

Abstract: Nanoclay reinforced, cyanate ester-based syntactic foams with varying nanoclay loadings were processed and evaluated for mechanical, dynamic mechanical and thermal properties. The volume percentage of the filler (microballoon + nanoclay) was kept constant at 70. X-ray diffraction studies showed intercalated morphology of the nanoclay particles in the foam composites. The properties of the nanoclay reinforced syntactic foams were compared with those of bare cyanate ester syntactic foams containing the same filler concentration. A considerable improvement in the mechanical properties viz. tensile, flexural and compressive strengths and corresponding moduli was observed for the foams on incorporation of nanoclay. The corresponding specific properties also showed substantial improvement. Nanoclay improved the toughness of the foam composites. The storage moduli were higher for the foam composites containing nanoclay. However, nanoclay diminished the Tg of the syntactic foams due to the plasticizing effect of the organic moiety of the nanoclay. The thermal properties of the syntactic foams were not significantly influenced by the addition of nanoclay.

Heterogeneity in pre-monsoon aerosol types over the Arabian Sea deduced from ship-borne measurements of spectral AODs

Abstract: . Ship-borne sunphotometer measurements obtained in the Arabian Sea (AS) in the pre-monsoon season (18 April–10 May 2006) during a cruise campaign (ICARB) have been used to retrieve the Aerosol Optical Depth (AOD; τ) and the Angstrom wavelength exponent (α). The continents surrounding the AS produce natural and anthropogenic aerosols that have distinctive influences on α and its spectral distribution. The α values were estimated by means of the least-squares method over the spectral bands 340–1020 nm and 340–870 nm. The spectral distribution of AOD in logarithmic co-ordinates could be fit using a 2nd order polynomial with higher accuracy in the wavelength band 340–1020 nm than in the 340–870 nm band. A polynomial fit analytically parameterizes the observed wavelength dependencies of AOD with least errors in spectral variation of α and yields accurate estimates of the coefficients (a1 and a2). The coarse-mode (positive curvature in the lnτλ vs. lnλ) aerosols are mainly depicted in the Northern part of the AS closely associated with the nearby arid areas while fine-mode aerosols are mainly observed over the far and coastal AS regions. In the study period the mean AOD at 500 nm is 0.25±0.11 and the α340-1020 is 0.90±0.19. The α340-870 exhibits similar values (0.92±0.18), while significant differences revealed for the constant terms of the polynomial fit (a1 and a2) proportionally to the wavelength band used for their determination. Observed day-to-day variability in the aerosol load and optical properties are direct consequence of the local winds and air-mass trajectories along with the position of the ship.

Development of electromagnetic shielding materials from the conductive blends of polystyrene polyaniline-clay nanocomposite

Abstract: Electromagnetic interference shielding composite materials were developed from the conductive blends of nanostructured polyaniline-clay composite (PANICN) and Polystyrene (PS) by a one step host matrix assisted emulsion polymerization of anilinium salt of 3-pentadecyl phenol-4-sulphonic acid (3-PDPSA) in clay. 3-PDPSA was derived from cashew nut shell liquid, a low cost renewable resource based product. These blends were characterized using Uv–visible and FT-IR spectroscopy, XRD, electrical conductivity, thermal property, dielectric property and electromagnetic shielding efficiency. The interactions between the primary particles and host matrix were elucidated from the studies made through spectroscopy and rheology. The key finding of the research is that this low cost PANICNPS blend with superior electrical conductivity (7.6 × 10−1 S/m), excellent thermal stability and EMI SE of 10–20 dB at 8 GHz makes them as a promising candidate for application in EMI shielding and antistatic discharge matrix for the encapsulation of micro electronic devices.

Optical, radiative, and source characteristics of aerosols at Minicoy, a remote island in the southern Arabian Sea

Abstract: Extensive measurements of aerosol radiative and microphysical properties were made at an island location, Minicoy (8.3 degrees N, 73.04 degrees E) in the southern Arabian Sea. A large variability in aerosol characteristics associated with changes in air mass and precipitation characteristics was observed. Six distinct transport pathways were identified on the basis of cluster analysis. The Indo-Gangetic Plain, along with the northern Arabian Sea and west Asia (NWA), was identified to be the region having the highest potential for aerosol mass loading at the island. This estimate is based on the concentration weighted trajectory as well as cluster analysis. Dust transport from the NWA region was found to make a substantial contribution to the supermicron mass fraction. The black carbon mass mixing ratios observed were the lowest compared to previous measurements over this region. Consequently, the atmospheric radiative forcing efficiency was low and was in the range 10-28 W m(-2).

Optical and physical characteristics of Bay of Bengal aerosols during W‐ICARB: Spatial and vertical heterogeneities in the marine atmospheric boundary layer and in the vertical column

Abstract: [1] Analysis of the continuous and collocated measurements of columnar spectral aerosol optical depths (AODs) and mass size distributions in the marine atmospheric boundary layer (MABL) over the Bay of Bengal (BoB), carried out from 27 December 2008 to 29 January 2009 during the Winter Integrated Campaign for Aerosols, Gases and Radiation Budget (W-ICARB), revealed distinct regional features in the spatial variations of the aerosol properties in the MABL and column. In general, AODs were high over the northern and northwestern parts of the BoB, with pockets of very high values, within which the AODs were as high as ∼0.8 while the smallest values (∼0.1) were observed over the northeastern BoB, off the Myanmar and Bangladesh coasts. Interestingly, though, this region had the highest Angstrom wavelength exponent α (∼1.5), notwithstanding the generally high values that prevailed over the eastern as well as northern coastal regions of India. Back trajectory analyses revealed the significant role of the advected aerosols in the observed spatial pattern. Within the MABL, high accumulation mode mass concentrations (MA) prevailed over the entire BoB with the accumulation fraction ranging from 0.6 to 0.95, whereas very high fine-mode (r < 0.1 μm) aerosol mass fractions (∼0.8) were observed over the northeastern and western coastal BoB adjoining the Indian mainland (where α was high to very high). The vertical distributions, inferred from the columnar and MABL properties as well as from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations data, revealed better homogeneity in the northeastern and eastern BoB, whereas significant heterogeneity was seen over other regions.

Regional distribution of deep clouds and cloud top altitudes over the Indian subcontinent and the surrounding oceans

Abstract: [1] The Bay of Bengal (BoB) and the east equatorial Indian Ocean are among the most intense deep convective regions over the tropics. Long-term monthly mean distributions of deep clouds and the regional differences in the cloud top brightness temperature (CTBT) over the Indian subcontinent and the surrounding oceanic regions (the northern and eastern BoB, the southeast Arabian Sea, and the eastern equatorial Indian Ocean) are derived using National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer data for a period of 10 years and are compared with the direct observations of cloud top altitude (CTA) using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). The deepest clouds are found to occur over the northern BoB (NBoB) during the June–August period. The most probable CTBT in this region is ∼12 K lower than that over the other deep convective regions. CALIPSO observations also show that the frequency of occurrence of CTA peaks at an altitude of ∼16.5 km over the NBoB, which is ∼1 km higher than that over the other regions. Strong convergence of horizontal wind between the surface and ∼200 hpa level and large divergence above, combined with the most favorable sea surface temperature (>28°C), might be mainly responsible for the highest CTA being observed over the NBoB. The annual variation of the base altitude and thickness of the tropical tropopause layer (TTL) and the upper tropospheric temperature are closely associated with the corresponding variations in the deep cloud fraction. Considerable fraction of deep clouds occurs within the TTL over the BoB during the June–August period.

Synthesis, Characterization and Ceramic Conversion Studies of Borosiloxane Oligomers from Phenyltrialkoxysilanes

Abstract: Borosiloxane oligomers, which give ceramic residue in the range of 64–75% (at 900 °C in inert atmosphere), were synthesized through the condensation of boric acid with phenyltrimethoxysilane (PTMOS) and phenyltriethoxysilane in diglyme both in the presence and absence of hydrochloric acid as catalyst. The effect of concentration of the reactants and reaction time on the processability, yield and thermal stability of the product obtained was studied. The oligomers obtained are soluble in common organic solvents and were characterized by FT-IR and NMR spectroscopy, GPC and TGA. The ceramic conversion of one of the oligomers was carried out by heat treatment at 900, 1,500 and 1,650 °C in inert atmosphere. XRD studies reveal that the ceramic formed at 1,500 °C is amorphous and undergoes crystallization to β-SiC when heat treated at 1,650 °C.

Dynamics of solar wind protons reflected by the Moon

Abstract: [1] Solar system bodies that lack a significant atmosphere and significant internal magnetic fields, such as the Moon and asteroids, have been considered passive absorbers of the solar wind. However, ion observations near the Moon by the SELENE spacecraft show that a fraction of the impacting solar wind protons are reflected by the surface of the Moon. Using new observations of the velocity spectrum of these reflected protons by the SARA experiment on board the Chandrayaan-1 spacecraft at the Moon, we show by modeling that the reflection of solar wind protons will affect the global plasma environment. These global perturbations of the ion fluxes and the magnetic fields will depend on microscopic properties of the object's reflecting surface. This solar wind reflection process could explain past ion observations at the Moon, and the process should occur universally at all atmosphereless nonmagnetized objects.

Size Distribution of Particles in Combustion Products of Aluminized Composite Propellant

Abstract: An experimental study is carried out to measure the size distribution of condensed particles in the combustion products of aluminized composite propellant using quench bomb technique. One meter long and 200 mm diameter quench bomb with propellant specimens of mass ∼32 g is used. The effects of geometry of propellant specimen, quench distance, and chamber pressure on the particle size distribution are investigated. Size distribution of the particles is measured by laser diffraction particle size analyzer and the surface structure is examined by scanning electron microscope. The study shows that the particles are spherical and their sizes vary from 0.1 to 300 μm. The particles have trimodal distribution with modes at ∼1 μm, ∼4 μm, and μ70 μm. Although modes 1 and 4 μm particles are alumina, mode 70 μm particles are aluminum agglomerates. About 30% of aluminum present in the propellant converts into agglomerates. Results also show that coalescence of particles is higher if the particles have higher residence time in the high-temperature region or when the flow is more turbulent. From the particle size distribution obtained in the quench bomb tests, the size distribution is deduced for the combustion chamber of rocket motor.

Protons in the near‐lunar wake observed by the Sub‐keV Atom Reflection Analyzer on board Chandrayaan‐1

Abstract: [1] Significant proton fluxes were detected in the near-wake region of the Moon by an ion mass spectrometer on board Chandrayaan-1. The energy of these nightside protons is slightly higher than the energy of the solar wind protons. The protons are detected close to the lunar equatorial plane at a 140° solar zenith angle, that is, ∼50° behind the terminator at a height of 100 km. The protons come from just above the local horizon and move along the magnetic field in the solar wind reference frame. We compare the observed proton flux with the predictions from analytical models of an electrostatic plasma expansion into a vacuum. The observed velocity is higher by a factor of 2 to 3 than the velocity predicted by analytical models. The simple analytical models cannot explain the observed ion dynamics along the magnetic field in the vicinity of the Moon.

Black carbon aerosols over coastal Antarctica and its scavenging by snow during the Southern Hemispheric summer

Abstract: [1] Mass concentrations of aerosol black carbon (BC) and of the composite (total) aerosols (MB and MT, respectively) were measured over two Antarctic locations, Maitri [70°S, 12°E, 123 m mean sea level (msl)] and Larsemann Hills (LH; 69°S, 77°E, 48 m msl) as a part of the twenty-eighth Indian Scientific Expedition to Antarctica during the Southern Hemispheric summer of 2009. Despite being very low compared to Northern Hemisphere locations, MB and its mass mixing ratio to the total aerosols were much high over Maitri (∼75 ng m−3 and 2%) compared to LH (13 ng m−3 and 0.2%). At both locations, MB fell abruptly after blizzards, after which the values reduced to nearly half the pre-blizzard values. This BC scavenging by snow can lead to change in snow albedo and has strong climate implications. The Angstrom exponent (αabs) estimated from the spectral values of absorption coefficients (σabs) is found to vary from 0.5 to 1, indicating higher a BC-to-organic carbon ratio typical of fossil fuel origin.

Features of the F3 layer occurrence over the equatorial location of Trivandrum

Abstract: . The general features of the F3 layer occurrence over the magnetic equatorial location of Trivandrum (8.5° N; 77° E; dip lat ~0.5° N) in India during the period from 1996–2005 are presented using the ionosonde observations. The study brings out that the F3 layer occurrence over Trivandrum is weak and rare compared to the other equatorial locations. The F3 layer occurrence is relatively more pronounced during the magnetically active conditions, thus indicating the dependence of the layer formation over Trivandrum on magnetic activity. It is also observed that the percentage occurrence of the F3 layer decreases with increasing solar activity.

X-rays from Saturn: a study with XMM-Newton and Chandra over the years 2002–05

Abstract: Aims. We approach the study of Saturn and its environment in a novel way using X-ray data, by making a systematic and uniform spectral analysis of all the X-ray observations of the planet to date. Methods. We present the results of the two most recent (2005) XMM-Newton observations of Saturn together with the re-analysis of an earlier (2002) observation from the XMM-Newton archive and of three Chandra observations in 2003 and 2004. While the XMM-Newton telescope resolution does not enable us to resolve spatially the contributions of the planet's disk and rings to the X-ray flux, we can estimate their strengths and their evolution over the years from spectral analysis, and compare them with those observed with Chandra.Results. The spectrum of the X-ray emission is well fitted by an optically thin coronal model with an average temperature of 0.5 keV. The addition of a fluorescent oxygen emission line at ~0.53 keV improves the fits significantly. In accordance with earlier reports, we interpret the coronal component as emission from the planetary disk, produced by the scattering of solar X-rays in Saturn's upper atmosphere, and the line as originating from the Saturnian rings. The strength of the disk X-ray emission is seen to decrease over the period 2002–2005, following the decay of solar activity towards the current minimum in the solar cycle. By comparing the relative fluxes of the disk X-ray emission and the oxygen line, we suggest that the line strength does not vary over the years in the same fashion as the disk flux. We consider possible alternatives for the origin of the line. The connection between solar activity and the strength of Saturn's disk X-ray emission is investigated and compared with that of Jupiter. We also discuss the apparent lack of X-ray aurorae on Saturn; by comparing the planet's parameters relevant to aurora production with those of Jupiter we conclude that Saturnian X-ray aurorae are likely to have gone undetected because they are below the sensitivity threshold of current Earth-bound observatories. A similar comparison for Uranus and Neptune leads to the same disappointing conclusion, which is likely to hold true also with the planned next generation International X-ray Observatory. The next step in advancing this research can only be realised with in-situ X-ray observations at the planets.

Nanoclay reinforced thermoplastic toughened epoxy hybrid syntactic foam: Surface morphology, mechanical and thermo mechanical properties

Abstract: Epoxy hybrid syntactic foams were prepared with diglycidyl ether of bisphenol A (DGEBA) epoxy resin, diamino diphenyl sulfone (DDS), hydroxyl terminated polyether ether ketone having pendant methyl group (PEEKMOH), microballoon and nanoclay. The density of the foam was maintained between 0.6 and 0.72 g/cc for all compositions. Fracture toughness, tensile, flexural and compressive properties of the foam were evaluated with respect to clay and PEEKMOH concentrations. Morphology by X-ray diffraction revealed that the clay particles within the epoxy resin were intercalated for all the compositions of the syntactic foam. Fracture toughness and mechanical properties of the syntactic foam were significantly improved by the addition of nanoclay. A further enhancement in fracture toughness and mechanical properties was observed by the addition of PEEKMOH. The hybrid epoxy syntactic foam thus prepared exhibited 58%, 77% and 38% improvement in compressive strength, percentage elongation and fracture toughness, respectively, compared to the neat epoxy syntactic foam. The specific mechanical properties were found to be higher for the epoxy hybrid syntactic foam containing 3 wt% nanoclay and 3 wt% of PEEKMOH combination. The storage and loss modulus of the syntactic foam were also increased by the addition of nanoclay and PEEKMOH. A marginal improvement in Tg was observed with clay incorporated syntactic foam. SEM analysis revealed that increased microcracking, crack path deflection, matrix deformation, plastic deformation, rupture of microballoons and debonded microspheres influencing on fracture toughness and mechanical properties of epoxy hybrid syntactic foam.

First observations of turbulence parameters in the troposphere over the Bay of Bengal and the Arabian Sea using radiosonde

Abstract: [1] This paper discusses the turbulence characteristics of the free atmosphere over the Bay of Bengal and the Arabian Sea during the premonsoon season of 2006. The turbulence scaling concepts, developed over the past decades for application to oceanic mixing, are used for retrieving turbulence properties in the free atmosphere from high-resolution soundings, as described by Clayson and Kantha (2008). The variability in the vertical turbulence structure over a large spatial region is studied using this novel method for the first time. Investigations revealed the presence of a highly turbulent band at upper troposphere below the cold point tropopause (CPT) with significant enhancements in Thorpe length and eddy diffusion coefficient. This increased turbulence is studied in conjunction with the observations of the tropical tropopause layer (TTL). It is seen that the lower and upper boundaries of this turbulence band nearly coincide with the height where the potential temperature lapse rate begins to show a decrease (LRHmin) and cold point tropopause, respectively. The TTL is the transition regime from convectively dominated troposphere to radiatively dominated stratosphere, and is characterized by a decrease in the static stability. The enhanced zonal and meridional wind shear observed in this region shows that the stability in this region is further weakened because of the breaking of Kelvin–Helmholtz waves, which results in the enhancement of turbulence. The study reveals the potential of high-resolution soundings to be used in the investigations of turbulence in the free atmosphere.

Surface morphology, thermomechanical and barrier properties of poly(ether sulfone)-toughened epoxy clay ternary nanocomposites

Abstract: Poly(ether sulfone) (PES)-toughened epoxy clay ternary nanocomposites were prepared by melt blending of PES with diglycidyl ether of bisphenol A epoxy resin along with Cloisite 30B followed by curing with 4,4′-diaminodiphenylsulfone. The effect of organoclay and thermoplastic on the fracture toughness, permeability, viscoelasticity and thermomechanical properties of the epoxy system was investigated. A significant improvement in fracture toughness and modulus with reduced coefficient of thermal expansion (CTE) and gas permeability were observed with the addition of thermoplastic and clay to the epoxy system. Scanning electron microscopy of fracture-failed specimens revealed crack path deflection and ductile fracture without phase separation. Oxygen gas permeability was reduced by 57% and fracture toughness was increased by 66% with the incorporation of 5 phr clay and 5 phr thermoplastic into the epoxy system. Optical transparency was retained even with high clay content. The addition of thermoplastic and organoclay to the epoxy system had a synergic effect on fracture toughness, modulus, CTE and barrier properties. Planetary ball-milled samples gave exfoliated morphology with better thermomechanical properties compared to ultrasonicated samples with intercalated morphology. Copyright © 2010 Society of Chemical Industry

Comparative analysis and variability of the Jovian X‐ray spectra detected by the Chandra and XMM‐Newton observatories

Abstract: Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X-ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. In conjunction with the Xspec spectral fitting software, the model is applied to analyze observations from both Chandra and XMM-Newton by systematically varying the initial precipitating ion parameters to obtain the best fit model for the observed spectra. In addition to the oxygen and sulfur ions considered previously, carbon is included to discriminate between solar wind and Jovian magnetospheric ion origins, enabled by the use of extensive databases of both atomic collision cross sections and radiative transitions. On the basis of fits to all the Chandra observations, we find that carbon contributes negligibly to the observed polar X-ray emission suggesting that the highly accelerated precipitating ions are of magnetospheric origin. Most of the XMM-Newton fits also favor this conclusion with one exception that implies a possible carbon contribution. Comparison among all the spectra from these two observatories in light of the inferred initial energies and relative abundances of precipitating ions from the modeling show that they are significantly variable in time (observation date) and space (north and south polar X-ray auroras).

Temporal modulations of the longitudinal structure in F2 peak height in the equatorial ionosphere as observed by COSMIC

Abstract: [1] This study investigates the temporal variability of longitudinal structure in F2 layer peak height (hmF2) in the equatorial ionosphere. For this study, electron density profiles retrieved from the radio occultation measurements by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) are fitted with a two-layer Chapman function to determine hmF2. The hmF2 values in the magnetic equatorial region display a four-peaked longitudinal structure that has been identified in other ionospheric observations. The four-peaked structure is likely the signature of the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 (DE3). Further analysis for the period of prominent four-peaked structure over August-September 2008 finds that this structure exhibits a 5 day periodicity. Coincidentally, the all-sky interferometric meteor radar's wind measurements at Thumba (8.5°N, 77°E) in India for the mesosphere and lower thermosphere indicate strong 5 day planetary waves within that time period. The observed temporal periodicity of the four-peaked longitudinal structure in hmF2 could thus be attributed to the interaction of DE3 with a 5 day planetary wave.