Showing papers by "Vikram Sarabhai Space Centre published in 2004"

Radiative forcing by aerosols over the Bay of Bengal region derived from shipborne, island‐based, and satellite (Moderate‐Resolution Imaging Spectroradiometer) observations

Abstract: Measurements of spectral aerosol optical depths (AODs) were made over the Bay of Bengal region (adjacent to the Indian landmass) on board the oceanographic research vessel Sagar Kanya during February 2003 Simultaneous measurements of spectral AODs and mass concentrations of the composite aerosols and aerosol black carbon (BC) were made at an island location, Port Blair (1163degreesN, 9271degreesE), also in the Bay of Bengal At the cruise locations the AODs were in the range of similar to03-06 at 500 nm (with a mean value of 041 +/- 014) and Angstrom wavelength exponent of similar to11 +/- 01; while at Port Blair the AODs were in the range of 011-048 at 500 nm and Angstrom wavelength exponent of 098 +/- 007 Aerosol BC constituted 58 +/- 06% of the composite aerosol mass concentration with a single-scattering albedo of similar to088, indicating the presence of a significant amount of submicron absorbing aerosols Comparisons of AODs measured at Port Blair during cruise 188 and an earlier cruise (cruise 161B) during March 2001 (over the Bay of Bengal, Arabian Sea, and Indian Ocean) with those derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) (on board the TERRA platform) showed excellent agreement with a mean difference of similar to001 and a root-mean-square difference of similar to003 Regionally averaged aerosol (net) forcing over the Bay of Bengal was in the range -15 to -24 W m(-2) at the surface and -2 to -4 W m(-2) at the top of the atmosphere in February 2003; these values were smaller in magnitude than those observed over this region during March 2001 and larger than that observed over the Arabian Sea and the Indian Ocean The resulting atmospheric heating due to aerosol absorption was similar to05degreesK/d

Altitude profiles of aerosol BC, derived from aircraft measurements over an inland urban location in India

Abstract: [1] Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer and above it were measured for the first time in India, over the urban location Hyderabad, onboard an aircraft during two consecutive days of February 2004. The profiles on both the days were consistent, and showed a rapid decrease in BC concentration within the boundary up to ∼550 m AGL (where convective activity prevailed). Sodar measurements from the nearby location revealed the mean boundary layer height to be ∼600 m during the flight period. The decrease in BC above the boundary layer was quite weak up to ∼2.2 km AGL.

Characteristics of aerosol spectral optical depths over Manora Peak: A high‐altitude station in the central Himalayas

Abstract: [1] We present, for the first time, spectral behavior of aerosol optical depths (AODs) over Manora Peak, Nainital, located at an altitude of ∼2 km in the Shivalik ranges of the central Himalayas. The observations were carried out using a multiwavelength solar radiometer during January to December 2002. The main results of the study are extremely low AODs during winter, a remarkable increase to high values in summer, and a distinct change in the spectral dependencies of AODs from relatively steeper spectra during winter to shallower ones in summer. A comparison of the total optical depths of the nighttime measurements taken during the 1970s with the daytime values from the current study underlines the fact that loading of larger size particles during summer also occurred at that time, though less severely than it does today. During transparent days the AOD values usually lie below 0.08, while during dusty (turbid) days they lie between 0.08 and 0.69. The average AOD value during the winter, particularly in January and February, is ∼0.03 ± 0.01 at 0.5 μm. The mean aerosol extinction law at Manora Peak during 2002 is best represented by 0.10λ−0.61. However, during transparent days, which covers almost 40% of the time, it is represented by 0.02λ−0.97. This value of wavelength exponent, representing reduced coarse concentration and the presence of fine aerosols, indicates that the station measures aerosol in the free troposphere at least during part of the year.

Aerosol black carbon over Arabian Sea during intermonsoon and summer monsoon seasons

Abstract: Extensive, collocated measurements of the mass concentrations of composite and black carbon (BC) aerosols were made over coastal Arabian Sea, adjoining Indian Peninsula, for the first time during the inter-monsoon and summer monsoon periods, of 2003, as part of Arabian Sea Monsoon Experiment (ARMEX). Results showed that the diurnal variations are weak in March, and vanish completely by May/June, associated with the change in the synoptic circulations. The concentration of BC (and its share to total aerosol mass) decreases continuously, from similar to700 ng m(-3) (2.5%) in March to similar to104 ng m(-3) (0.5%) by June. Consequently, the net atmospheric forcing (heating) efficiency decreases from similar to70 W m(-2) (for reported winter conditions) to similar to30 W m(-2) for inter-monsoon and to similar to15 W m(-2) for summer monsoon seasons. These will have implications on regional climate forcing.

An Overview on the Synthetic Routes and Properties of Ammonium Dinitramide (ADN) and other Dinitramide Salts

Abstract: In recent years, there has been a considerable interest in the development of novel type of high performance propellants for use in solid rocket motors. Ammonium salt of dinitramidic acid NH4N(NO2)2 (ADN) has attracted wide interest as a potentially useful energetic oxidizer for rocket propellants because of its clean and environment-friendly exhaust products during burning. ADN contains one N(NO2)2 group and its synthesis requires new type of N-nitration. The present paper reviews the general synthetic methods used for the synthesis of inorganic, organic and metal dinitramide salts and their properties, with a special emphasis on ammonium dinitramide. The salient features with reference to the extent of conversion and ease of separation of the products of the various synthetic methodologies are also addressed.

Preparation, characterization and microwave dielectric properties of Ba(B1/2′Nb1/2)O3 [B′ = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb and In] ceramics

Abstract: Microwave dielectric resonators (DRs) based on Ba(B 1/2 ′Nb 1/2 )O 3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Yb, and In] complex perovskites have been prepared by conventional solid state ceramic route. The dielectric properties (relative permittivity, e r ; quality factor, Q ; and resonant frequency, τ f ) of the ceramics have been measured in the frequency range 4–6 GHz using resonance methods. The resonators have relatively high dielectric constant in the range 36–45, high quality factor and small temperature variation of resonant frequency. The dielectric properties are found to depend on the tolerance factor ( t ), ionic radius ( r ), and lattice parameter ( a p ).

Kinetic energy distributions and line profile measurements of dissociation products of water upon electron impact

Abstract: [1] The Doppler line profiles of H Ly-α (1216 A) and O I (1302 A and 1152 A) resulting from electron impact dissociative excitation of H2O have been measured with a high-resolution (λ/Δλ = 50,000) ultraviolet spectrometer. The line profiles are used to calculate the kinetic energy distribution of the hydrogen atoms produced in dissociative excitation and ionization of H2O at electron impact energies 25, 35, and 100 eV. Three distinct populations of H(2p) atoms were found. The kinetic energy of hydrogen atoms is found to have contributions from a low-energy component, with a mean energy of ∼0.2 eV at all the three electron impact energies. In addition, a medium-energy component appears with a mean energy of ∼2.0 eV for 35 eV electrons, and a high-energy component, ∼7 eV, for 100 eV electrons. The measurement of O I (1302 A) and O I (1152 A) line profiles indicate that the kinetic energy of excited O I atoms is very small (∼1 eV or less) at all electron impact energies. Most of the energy released in dissociation is found in the translational energy of the hydrogen atoms. The excitation functions of H Ly-α, O I (1302 A) feature of oxygen, and A(0) − X(0) molecular band of hydroxyl near 3050 A from threshold to 600 V were also measured. The spectrum (1.0 A FWHM) of the rotational structure of OH (A − X) from electron impact dissociation indicates a high degree of rotational excitation, which is almost identical to the rotational structure from dissociative recombination of H2O+. The results presented in this paper have important applications to planetary bodies, like comets, icy satellites of outer planets, Saturn's magnetosphere, and rings, all of which have H2O and its daughter products in large amount.

Low k thin films based on rf plasma-polymerized aniline

Abstract: Thermally stable materials with low dielectric constant (k<3.9) are being hotly pursued. They are essential as interlayer dielectrics/intermetal dielectrics in integrated circuit technology, which reduces parasitic capacitance and decreases the RC time constant. Most of the currently employed materials are based on silicon. Low k films based on organic polymers are supposed to be a viable alternative as they are easily processable and can be synthesized with simpler techniques. It is known that the employment of ac/rf plasma polymerization yields good quality organic thin films, which are homogenous, pinhole free and thermally stable. These polymer thin films are potential candidates for fabricating Schottky devices, storage batteries, LEDs, sensors, super capacitors and for EMI shielding. Recently, great efforts have been made in finding alternative methods to prepare low dielectric constant thin films in place of silicon-based materials. Polyaniline thin films were prepared by employing an rf plasma polymerization technique. Capacitance, dielectric loss, dielectric constant and ac conductivity were evaluated in the frequency range 100 Hz–1 MHz. Capacitance and dielectric loss decrease with increase of frequency and increase with increase of temperature. This type of behaviour was found to be in good agreement with an existing model. The ac conductivity was calculated from the observed dielectric constant and is explained based on the Austin–Mott model for hopping conduction. These films exhibit low dielectric constant values, which are stable over a wide range of frequencies and are probable candidates for low k applications.

DSC study on the effect of isocyanates and catalysts on the HTPB cure reaction

Abstract: The urethane forming cure reactions of hydroxyl terminated polybutadiene (HTPB) binder with three different isocyanate curatives, viz., toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) and 4,4'-methylene bis(cyclohexyl isocyanate) (MCHI), were investigated by differential scanning calorimetry (DSC). The effect of two cure catalysts, viz., dibutyl tin dilaurate (DBTDL) and ferrric tris-acetylacetonate (FeAA) on the cure reactions was also studied. Cure kinetics was evaluated using the multiple heating rate Ozawa method. The reactivities of the three isocyanates and catalytic efficiencies were compared based on the DSC reaction temperatures, activation energies and rate constants. Viscosity build-up in these systems at isothermal temperature was also studied and compared with the results from DSC.

Threshold height (h′F)c for the meridional wind to play a deterministic role in the bottom side equatorial spread F and its dependence on solar activity

Abstract: [1] Detailed investigations have been carried out on the occurrence of bottom side Equatorial Spread F (ESF) and the thermospheric meridional wind characteristics just before the former's initiation using ground based ionospheric data corresponding to the equinoctial periods of 1993–1998, from Trivandrum (8.5°N, 76.5°E, dip = 0.5°N) and Sriharikota (13.7°N, 80.2°E, dip ∼ 10°N) in the Indian longitudes. Critical analysis of the base height of the F-region h′F at the time of triggering of ESF and the polarity of the meridional winds revealed that, if the h′F is above a certain level ESF occurred under both equatorward and poleward wind conditions. Below that level, ESF occurred only when equatorward winds were present implying that the equatorward winds must somehow be able to offset the reduced growth rate of the plasma instability responsible for ESF. A plausible explanation linking Equatorial Ionization Anomaly (EIA) and the consequent Equatorial Temperature and Wind Anomaly (ETWA) and the consequent neutral dynamics effectively enabling the instability even at lower height has been offered. The threshold height (h′F)c gleaned out on the basis of the polarity of the meridional winds has been shown to bear a linear relation to the solar activity and sheds light on the enigmatic short and long term variability of ESF.

Impact of Precipitation on Aerosol Spectral Optical Depth and Retrieved Size Distributions: A Case Study

Abstract: A case study is presented on the impact of two isolated, strong thundershowers during a prevailing dry, sunny season on the spectral optical depths and inferred columnar size characteristics of atmospheric aerosols at a tropical station. Results show a remarkable decrease in the aerosol optical depth and change in the spectral slope after the rain. The scavenging was found to be dependent on the particle size distribution; the larger, supermicron particles were found to be removed faster during the first shower itself, even though it was of only moderate intensity, resulting in about a 64% decrease in the columnar mass loading. In the second shower, which was stronger and more widespread than the former, more of the submicron particles in the optically active submicron size range were removed, but the reduction in mass loading was very small. The effective radius decreased continuously and so too did the columnar mass loading (total aerosol volume). The data are used to estimate the apparent colu...

Measurements of aerosol optical depths and black carbon over Bay of Bengal during post‐monsoon season

Abstract: Extensive and collocated measurements of aerosol optical depths (AODs), mass concentration of composite aerosols and aerosol black carbon (BC) were made over the Bay of Bengal(onboard R/V Sagar Kanya during its cruise #197) region during post-Indian summer monsoon period. These data along with MODIS (onboard TERRA satellite) data shows that aerosol visible AODs were in the range of 0.2 to 0.7 (with mean value of 0.43 ± 0.12) and Angstrom wavelength exponent of _0.93 ± 0.21 which in conjunction with a single scattering albedo (w) of _0.94 indicates the presence of weakly absorbing aerosols. The BC mass fraction was _2.9 ± 1.1% during post-monsoon season compared to 5.8 ± 0.6% (with w of _0.88) during premonsoon season. The presence of aerosols over Bay of Bengal during post-monsoon season decreases the short wave radiation reaching the surface by as much as $25 W m^{\mathrm{2}}$ and increases top of the atmosphere reflected radiation by $14 W m^{{2}}$. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 1610 Global Change: Atmosphere(0315, 0325); 1704 History of Geophysics: Atmospheric sciences; 1803 Hydrology: Anthropogenic effects.

Surface Boundary-Layer Characteristics Over a Tropical Inland Station: Seasonal Features

Abstract: Some characteristic features of the atmospheric surfacelayer over an inland tropical station, Lucknow (27°N, 81°E)in India, are investigated for different seasons using micrometeorological data collected at the 10-m levelof an instrumented tower. Seasonal monsoonal variations in wind circulation (north-easterliesand south-westerlies) dominate the flow over this part of the region. This study utilizesthe wind, temperature and humidity data obtained for a period of one year from February 1996 to January 1997. The diurnal variation of mean parameterssuch as temperature, relative humidity, and wind speed are studied for different seasonsnamely pre-, south-west, post- and north-east monsoon periods. Turbulent statistics are computedusing the eddy correlation technique, and are studied under the framework of Monin–Obukhov similarity theory with results compared with otherexperimental studies reported in the literature. It is found that the turbulence statistics arenearly independent of season and the near-neutral values of the normalized standard deviations ofthe three wind components, temperature and specific humidityare found to be 1.00 ± 0.04 (vertical), 2.63 ± 0.36(longitudinal), 2.19 ± 0.06 (lateral), 6.56 ± 0.33and 6.45 ± 0.33 respectively.

Observations of the atmospheric surface layer parameters over a semi arid region during the solar eclipse of August 11th, 1999

Abstract: This paper discusses the observations of the Atmospheric Surface Layer (ASL) parameters during the solar eclipse of August 11th, 1999. Intensive surface layer experiments were conducted at Ahmedabad (23‡21′N, 72‡36′E), the western part of India, which was close to the totality path. This rare event provided by nature is utilised to document the surface layer effects during the eclipse period using measurements of high frequency fluctuations of temperature, tri-axial wind components as well as mean parameters such as temperature, humidity, wind speed and subsoil temperature. Analysis showed that during the eclipse period, the turbulence parameters were affected leading to the suppression of the turbulence process, the main dynamic process in the atmospheric boundary layer, while the mean parameters showed variations within the natural variability of the observational period. The spectra of the wind components and temperature indicated decrease in spectral power by one order in magnitude during the eclipse period. The rate of dissipation of turbulent kinetic energy is found to decrease by more than one order during the eclipse period. The stability parameter showed a change from unstable to stable condition during the period of eclipse and back to unstable condition by the end of eclipse

Large aerosol optical depths observed at an urban location in southern India associated with rain-deficit summer monsoon season

Abstract: Aerosol spectral optical depth (AOD) measurements were made covering three years (2001, 2002 and 2003) at an urban continental location,Bangalore (13degrees N, 77.6degrees E) in India. These ground-based observations have shown that AODs reach a maximum during April (similarto0.5 at 500 nm) and minimum during the November to January period(similar to0.2). The Angstrom wavelength exponent (ce) was - LI during the dry season (December to April), which, in conjunction with the highoptical depth indicates significant anthropogenic influence. Seasonal variations in AODs appear to have an association with monsoon rainfall.Large AODs (a-1.4) were observed during the rain-deficit summer monsoon season (SMS) of 2002, which persisted for more than six months.Enhancement in AODs during SMS 2002 was similar to0.15 (at 500 nm),compared to 2001 and 2003.

Heat transfer in a viscoelastic boundary layer flow through a porous medium

Abstract: This paper examines the viscoelastic fluid flow and heat transfer characteristics in a saturated porous medium over an impermeable stretching surface with frictional heating and internal heat generation or absorption. The heat transfer analysis has been carried out for two different heating processes, namely (i) with prescribed surface temperature (PST-case) and (ii) prescribed surface heat flux (PHF-case). The governing equations for the boundary layer flow problem result similar solutions. For the specified five boundary conditions, it is not possible to solve directly the resulting sixth-order nonlinear ordinary differential equation. For the present incompressible boundary layer flow problem with constant physical parameters, the momentum equation is decoupled from the energy equation. Two closed–form solutions for the momentum equation are obtained and identified the realistic solution of the physical problem. Exact solution for the velocity field and the skin-friction are obtained. Also, the solution for the temperature and the heat transfer characteristics are obtained in terms of Kummer’s function. Asymptotic results for the temperature function for large Prandtl numbers are presented. The work due to deformation in the energy equation, which is essential and escaped from the attention of researchers while formulating the visco-elastic boundary layer flow problems, is considered. Drastic variation in the values of heat transfer coefficient is observed when the work due to deformation is ignored.

Thermodynamic structure of the Atmospheric Boundary Layer over the Arabian Sea and the Indian Ocean during pre-INDOEX and INDOEX-FFP campaigns

Abstract: . Spatial and temporal variability of the Marine Atmospheric Boundary Layer (MABL) height for the Indian Ocean Experiment (INDOEX) study period are examined using the data collected through Cross-chained LORAN (Long-Range Aid to Navigation) Atmospheric Sounding System (CLASS) launchings during the Northern Hemispheric winter monsoon period. This paper reports the results of the analyses of the data collected during the pre-INDOEX (1997) and the INDOEX-First Field Phase (FFP; 1998) in the latitude range 14°N to 20°S over the Arabian Sea and the Indian Ocean. Mixed layer heights are derived from thermodynamic profiles and they indicated the variability of heights ranging from 400m to 1100m during daytime depending upon the location. Mixed layer heights over the Indian Ocean are slightly higher during the INDOEX-FFP than the pre-INDOEX due to anomalous conditions prevailing during the INDOEX-FFP. The trade wind inversion height varied from 2.3km to 4.5km during the pre-INDOEX and from 0.4km to 2.5km during the INDOEX-FFP. Elevated plumes of polluted air (lofted aerosol plumes) above the marine boundary layer are observed from thermodynamic profiles of the lower troposphere during the INDOEX-FFP. These elevated plumes are examined using 5-day back trajectory analysis and show that one group of air mass travelled a long way from Saudi Arabia and Iran/Iraq through India before reaching the location of measurement, while the other air mass originates from India and the Bay of Bengal.

Dielectric and conductivity studies on cobalt phthalocyanine tetramers

Abstract: Electrically conductive organic and metal- loorganic polymers are of great interest and they have ap- plications in electronic, optical, photonic, photoelectric, elec- trochemical, and dielectric devices. Tetrameric cobalt phtha- locyanine was prepared by conventional chemical method. The dielectric permittivity of the tetrameric cobalt phthalo- cyanine sample was evaluated from the observed capaci- tance values in the frequency range 100 KHz to 5 MHz and in the temperature range of 300 to 383°K. It is found that the system obeys the Maxwell Wagner relaxation of space charge phenomenon. Further, from the permittivity studies AC conductivity was evaluated. The values of AC conduc- tivity and DC conductivity were compared. Activation en- ergy was calculated. To understand the conduction mecha- nism Mott's variable range hopping model was applied to the system. The T 1/4 behavior of the DC conductivity along with the values of Mott's Temperature (T0), density of states at the Fermi energy N (EF), and range of hopping R and hopping energy W indicate that the transport of charge carriers are by three-dimensional variable range hopping. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2529 -2535, 2004

Coupling effect of the equatorial F region irregularities on the low latitude E region instability processes

Abstract: [1] Simultaneous observations of E and F region irregularities made using the Gadanki MST radar are presented. The observations show that the E region echoes weaken or disappear during the growth phase of the topside F region irregularities. Unlike Jicamarca observations, no valley region echoes are observed during this phase. It is shown that the weakening or disappearance of E region signals are not directly coupled with the F region irregularities just overhead, but linked with the instability processes over the magnetic equator through the magnetic field lines. It is proposed that the fringe fields present in the valley region in association with the equatorial F region plasma bubbles, in the presence of appropriate background electric field conditions, are responsible candidates. It is shown that these fringe fields and the electric fields associated with the irregularities in the valley region can map to the low latitude E region and thereby inhibit the growth of the E region instability processes as revealed by the Gadanki radar observations.

Simulation studies on the tomographic reconstruction of the equatorial and low-latitude ionosphere in the context of the Indian tomography experiment: CRABEX

Abstract: . Equatorial ionosphere poses a challenge to any algorithm that is used for tomographic reconstruction because of the phenomena like the Equatorial Ionization Anomaly (EIA) and Equatorial Spread F (ESF). Any tomographic reconstruction of ionospheric density distributions in the equatorial region is not acceptable if it does not image these phenomena, which exhibit large spatial and temporal variability, to a reasonable accuracy. The accuracy of the reconstructed image generally depends on many factors, such as the satellite-receiver configuration, the ray path modelling, grid intersections and finally, the reconstruction algorithm. The present simulation study is performed to examine these in the context of the operational Coherent Radio Beacon Experiment (CRABEX) network just commenced in India. The feasibility of using this network for the studies of the equatorial and low-latitude ionosphere over Indian longitudes has been investigated through simulations. The electron density distributions that are characteristic of EIA and ESF are fed into various simulations and the reconstructed tomograms are investigated in terms of their reproducing capabilities. It is seen that, with the present receiver chain existing from 8.5° N to 34° N, it would be possible to obtain accurate images of EIA and the plasma bubbles. The Singular Value Decomposition (SVD) algorithm has been used for the inversion procedure in this study. As is known, by the very nature of ionospheric tomography experiments, the received data contain various kinds of errors, like the measurement and discretization errors. The sensitivity of the inversion algorithm, SVD in the present case, to these errors has also been investigated and quantified.

Atomic oxygen resistant coating from poly(tetramethyldisilylene-co-styrene)

Abstract: A polydisilahydrocarbon, namely, poly(tetramethyldisilylene-co-styrene), synthesized from dimethyldichlorosilane and styrene in 1 : 0.5 mol ratio under dechlorination conditions was evaluated as an atomic oxygen (AO) resistant coating for polyimide film and C-polyimide composite. Exposure of the polymer coating on a quartz plate to an AO fluence of 2.1 × 1021 atoms/cm2 resulted in practically no mass loss, indicating the AO resistance of the polymer. Ten percent solution of the polymer in toluene was applied on aluminized Kapton® polyimide film (125 μm thick) to obtain a coating thickness of ∼ 5 μm on the unaluminized surface. In a similar way, the coating was applied on a C-polyimide composite. The coated and uncoated samples of Kapton® film and C-polyimide composite were exposed to AO in a plasma barrel system. The uncoated aluminized Kapton® film (125 μm) lost 6.35 mg/cm2 when exposed to AO fluence of 1.6 × 1021 atoms/cm2 whereas the corresponding coated film lost only 0.14 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. In the case of the C-polyimide composite, the uncoated sample lost 63.64 mg/cm2 on exposure to AO fluence of 1.8 × 1021 atoms/cm2 whereas the coated one lost only 0.21 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. SEM studies suggest that the coating offers good protection to the substrates. Formation of cracks on some portions of the coating was noticed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2368–2375, 2004

Comparison of fracture models to assess the notched strength of composite/solid propellant tensile specimens

Abstract: Modifications are made in the well-known inherent flaw model as well as in the stress fracture models for accurate prediction of notched tensile strength of composite laminates containing holes or slits. To examine the adequacy of these modifications, fracture data on different composite materials reported in the literature are considered. The notched strength estimates from the present fracture models are found to be close to the existing test results. An attempt is made to correlate the fracture data of center crack tension specimens made of nitramine and HTPB-based propellant materials. The present analysis results from the above simple models are found to be in good agreement with test results. This study confirms the applicability of the above three fracture models to solid propellant materials having relatively low stiffness and strength. Since the notched strength estimates of composite/solid propellant tensile specimens are close to the test results, any one of them can be utilized while evaluating the notched tensile strength of specimens.

High‐resolution far ultraviolet spectrum of electron‐excited SO2

Abstract: The high resolution UV capabilities (lamda/delta lambda = 10(sup 5)) of the Hubble Space Telscope (HST) equipped with the Space Telescope Imaging Spectrograph (STIS) reflects a need for high resolution laboratory UV spectral data base for comparison with observation.