Characteristic Hump Research Articles

Physicochemical characterization and possible applications of the waste biomass ash from oleoresin industries of India

The oleoresin industries in India make use of the spice residue as boiler fuel and the combustion of this waste biomass generates tons of ash everyday. Herein the study we have carried out the characterization of this industrial waste ash in order to have a broad awareness of its properties in terms of toxicity, composition and possible utility. Techniques like XRF, ICP-AES, SEM–EDS, surface area, pore volume analysis, powder XRD, TG–DTA, FTIR and elemental analyses were used for the purpose. Ash collected from the grate fired furnace (bottom ash) as well the flyash deposited on the boiler walls and pipes were analyzed. Elemental analysis of the ashes indicates its potential as a crude fertilizer or cement replacement material. PXRD indicates the presence of several crystalline phases such as harrisonite (Ca(Fe3+,Mg)6(PO4)2(SiO4)2), aphthitalite ((K,Na)3Na(SO4)2, cryptomelane (KMn4+6Mn2+2O16), varulite (NaCaMn2+2.25Fe2+0.5Fe3+0.25(PO4)3), marokite (CaMn2O4), fersilicite (FeSi) in the flyash fraction and the phases magnetite (Fe3+2Fe2+O4), kalsilite (KAlSiO4), cryptomelane (KMn4+6Mn2+2O16), fukuchilite (Cu3Fe2+S8), walthierite (Ba0.5Al3(SO4)2(OH)6), and magnesite (Mg(CO3) in furnace ash. The amorphous nature of silica in the ashes is evident from the characteristic broad hump around 2θ=30. The iron rich fraction of the ash consists primarily of magnetite which leads to a greenish blue color on heating the ash above 650°C. This magnetite fraction if separated could find use as catalysts in organic reactions. SEM images indicate the ashes to be highly agglomerated and EDX data shows the surface of the ash particles covered with potassium oxide and carbon. The percentage of K seems to be higher in the flyash due to the volatility of the potassium compounds which is carried up by the air current. Even though the surface area of the as received ashes is negligible an acid treatment removes the surface adsorbed species and increases the surface area to 368m2/g making it an effective adsorbent.

Investigation of Pre-Stall Behavior in an Axial Compressor Rotor—Part I: Unsteadiness of Tip Clearance Flow

To investigate the pre-stall behavior of an axial flow compressor rotor, which was experimentally observed with spike-type stall inception, systematic experimental and whole-passage simulations were laid out to analyze the internal flow fields in the test rotor. In this part, emphases were put on the analyses of experimental results and the predicted results from steady simulations and unsteady simulations, which converged to equilibrium solutions with nearly periodic fluctuations of efficiency. The objective was to uncover the unsteady behavior of tip clearance flow and its associated flow mechanism at near-stall conditions. To validate the steady simulation results, the predicted total characteristics and spanwise distributions of aerodynamic parameters were first compared with the measured steady data, and a good agreement was achieved. Then, the numerically obtained unsteady flow fields during one period of efficiency fluctuations were analyzed in detail. The instantaneous flow structure near casing showed that tip secondary vortex (TSV), which appeared in the previous unsteady single-passage simulations, did exist in tip flow fields of whole-passage simulations. The cyclical motion of this vortex was the main source of the nearly periodic variation of efficiency. The simulated active period of TSV increased when the mass flow rate decreased. The simulated frequency of TSV at flow condition very close to the measured stall point equaled the frequency of the characteristic hump identified from the instantaneous casing pressure measurements. This coincidence implied that the occurrence of this hump was most probably a result of the movement of TSV. Further flow field analyses indicated that the interaction of the low-energy leakage fluid from adjacent passages with the broken-down tip leakage vortex (TLV) was the flow mechanism for the formation of TSV. Once TSV appeared in tip flow fields, its rearward movement would lead to a periodic variation in near-tip blade loading, which in turn altered the strength of TLV and TSV, accordingly, the low-energy regions associated with the breakdown of TLV and the motion of TSV, thus establishing a self-sustained unsteady flow oscillation in tip flow fields.

Simulation of Chain Organization in Encapsulated Polymers

AbstractSummary: The dimensional and structural properties of polymers confined into a cavity are computed by the Monte Carlo method as a function of the chain stiffness. The reduction of the size ratio <R2 > / < R> close to 2, distinctive of compact spheres, is observed at squeezing of chains into a capsule. The plots of the static structure factor S(q) computed for stiff chains show characteristic humps attributed to the toroidal structure. The orientation correlation function is found to be a very sensitive indicator of the globule – toroid transition in encapsulated chains. Evidence is presented that the toroidal morphology is formed in stiff polymers when the capsule radius approaches the chain persistence length (D ∼ P).

Evaluating MTBSTFA derivatization reagents for measuring naphthenic acids by gas chromatography-mass spectrometry

Naphthenic acids (general formula CnH2n+ZO2) are found in petroleum and oil sands deposits. Release of these acids to aquatic environments is a concern because of their potential toxicity. Naphthenic acids consist of a complex mixture of carboxylic acids, and estimating their concentrations in environmental samples is a challenge. Two recent reports have described gas chromatography-mass spectrometry (GC-MS) methods to selectively detect these acids in fish flesh and water samples. The methods use N-methyl-N-(t-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) with 1% t-butyldimethylchlorosilane (t-BDMCS) to derivatize naphthenic acids to their t-butyldimethylsilyl derivatives. Single ion monitoring (SIM) was used to detect the fragment m/z 267, which corresponds to the derivatives of one isomer class (n = 13 and Z = −4) of naphthenic acids. The SIM chromatograms give a characteristic naphthenic acids hump between retention times 15 and 20 min and a sharp peak for the t-butyldimethylsilyl derivatized surrogate standard, 9-fluorenecarboxylic acid. Integration of this hump and the peak from the surrogate standard allows quantification of the naphthenic acids. Using newly purchased MTBSTFA containing 1% t-BDMCS (from three different suppliers) yielded SIM chromatograms with one or two large contaminating peaks (eluting at 16.7 and 18.8 min) that interfered with integration of the hump, rendering the method unreliable. The contaminants were traced to the presence of t-BDMCS. Each of the three suppliers sells MTBSTFA devoid of t-BDMCS, and using MTBSTFA without 1% t-BDMCS was found to be suitable for the GC-MS method.

A low-temperature study to examine the role of ε-martensite during strain-induced transformations in metastable austenitic stainless steels

A low-temperature study of the mechanical behaviour of a metastable semi-austenitic stainless steel was carried out. This class of stainless steels is found to show a characteristic hump followed by softening in their stress–strain curves, especially at low temperatures, much like dynamically recrystallizing steels. Experiments are carried out at sub-zero temperatures to examine this phenomenon. Samples are subjected to various metallographic, X-ray and transmission electron microscopy techniques to identify the evolution of the different phases. The presence of an intermediate phase ε-martensite is detected which might cause a softening in the stress–strain behaviour, comparable with the formation in other low stacking fault energy stainless steels.

TlFe4Sb12: Weak itinerant ferromagnetic analogue to alkali-metal iron-antimony skutterudites

Structural, thermal, electronic, and electrical transport properties as well as high-field $^{57}\mathrm{Fe}$ M\"ossbauer investigations are reported for thallium iron antimonide $\mathrm{Tl}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$, in which thallium attains the formal charge of $+1$. Similar to the isostructural $\mathrm{Na}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ and $\mathrm{K}{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}$ homologues, the Tl-filled skutterudite is an itinerant ferromagnet with small ordered moment below ${T}_{C}=80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The electronic structure calculated by density functional methods exhibits a band-ferromagnetic ground state and nearly half-metallic properties. The specific heat is dominated by a low-lying mode due to vibrations of the Tl cation in the cavity of the $[{\mathrm{Fe}}_{4}{\mathrm{Sb}}_{12}]$ polyanionic host. Electrical resistivity displays a characteristic hump and a sharp anomaly at ${T}_{C}$. These features and the large magnetoresistance at low temperatures can be explained by a strong compensation of hole and electron carriers in the band structure. Temperature-dependent $^{57}\mathrm{Fe}$ M\"ossbauer spectroscopy confirms the magnetic character.

Cascading on extragalactic background light

High-energy gamma-rays propagating in the intergalactic medium can interact with background infrared photons to produce e+e- pairs, resulting in the absorption of the intrinsic gamma-ray spectrum. TeV observations of the distant blazar 1ES 1101-232 were thus recently used to put an upper limit on the infrared extragalactic background light density. The created pairs can upscatter background photons to high energies, which in turn may pair produce, thereby initiating a cascade. The pairs diffuse on the extragalactic magnetic field (EMF) and cascade emission has been suggested as a means for measuring its intensity. Limits on the IR background and EMF are reconsidered taking into account cascade emissions. The cascade equations are solved numerically. Assuming a power-law intrinsic spectrum, the observed 100 MeV - 100 TeV spectrum is found as a function of the intrinsic spectral index and the intensity of the EMF. Cascades emit mainly at or below 100 GeV. The observed TeV spectrum appears softer than for pure absorption when cascade emission is taken into account. The upper limit on the IR photon background is found to be robust. Inversely, the intrinsic spectra needed to fit the TeV data are uncomfortably hard when cascade emission makes a significant contribution to the observed spectrum. An EMF intensity around 1e-8 nG leads to a characteristic spectral hump in the GLAST band. Higher EMF intensities divert the pairs away from the line-of-sight and the cascade contribution to the spectrum becomes negligible.

The influence of foot progression angle on the knee adduction moment during walking and stair climbing in pain free individuals with knee osteoarthritis

The external knee adduction moment during walking and stair climbing has a characteristic double hump pattern. The magnitude of the adduction moment is associated with the development and progression of medial compartment knee osteoarthritis (OA). There is an inverse relationship between the magnitude of the second peak adduction moment and foot progression angle (FPA). Increasing FPA beyond a self-selected degree of toe-out may further reduce the magnitude of this moment for persons with knee OA. In this study, subjects with medial compartment knee OA walked and climbed stairs using their natural (i.e. self-selected) and an increased FPA (i.e. self-selected + 15° of additional toe-out). Increasing FPA did not change the magnitude of the first peak adduction moment but it did significantly decrease the second peak during walking. The first peak moment during stair ascent was significantly greater for the increased FPA condition, and a significant reduction was noted for the second peak. No significant differences were noted during stair descent. These results suggest that walking with a toe-out strategy may benefit persons with early stages of medial knee OA.

Models of large-scale viscous flow in the Earth's mantle with constraints from mineral physics and surface observations

SUMMARY Modelling the geoid has been a widely used and successful approach in constraining flow and viscosity in the Earth’s mantle. However, details of the viscosity structure cannot be tightly constrained with this approach. Here, radial viscosity variations in four to five mantle layers (lithosphere, upper mantle, one to two transition zone layers, lower mantle) are computed with the aid of independent mineral physics results. A density model is obtained by converting s-wave anomalies from seismic tomography to density anomalies. Assuming both are of thermal origin, conversion factors are computed based on mineral physics results. From the density and viscosity model, a model of mantle flow, and the resulting geoid and radial heat flux profile are computed. Absolute viscosity values in the mantle layers are treated as free parameters and determined by minimizing a misfit function, which considers fit to geoid, ‘Haskell average’ determined from post-glacial rebound and the radial heat flux profile and penalizes if at some depth computed heat flux exceeds the estimated mantle heat flux 33 TW. Typically, optimized models do not exceed this value by more than about 20 per cent and fit the Haskell average well. Viscosity profiles obtained show a characteristic hump in the lower mantle, with maximum viscosities of about 10 23 Pa s just above the D �� layer— several hundred to about 1000 times the lowest viscosities in the upper mantle. This viscosity contrast is several times higher than what is inferred when a constant lower mantle viscosity is assumed. The geoid variance reduction obtained is up to about 80 per cent—similar to previous results. However, because of the use of mineral physics constraints, a rather small number of free model parameters is required, and at the same time, a reasonable heat flux profile is obtained. Results are best when the lowest viscosities occur in the transition zone. When viscosity is lowest in the asthenosphere, variance reduction is about 70‐75 per cent. Best results were obtained with a viscous lithosphere with a few times 10 22 Pa s. The optimized models yield a core-mantle boundary excess ellipticity several times higher than observed, possibly indicating that radial stresses are partly compensated due to non-thermal lateral variations within the lowermost mantle.

The Rate Variability-Distortion (VD) Curve of Encoded Video and Its Impact on Statistical Multiplexing

Encoded video is expected to contribute a significant portion of the load on future communication systems and networks, which often employ statistical multiplexing. In such systems, the number of video streams that can be supported depends both on the mean bit rate as well as bit rate variability of the video streams. At the same time, the utility (revenue) earned from video streaming depends both on the number of supported video streams as well as their quality level. In this paper we examine the interplay between video quality, traffic variability, and utility for open-loop encoded video. We introduce the rate variability-distortion (VD) curve which relates the bit rate variability to the quality level of an encoded video. We find that the VD curve generally exhibits a characteristic hump behavior of first increasing, peaking, and subsequently decreasing variability for increasing quality. We examine the impact of video content characteristics, encoding parameters, and traffic smoothing on the VD behavior. We describe a methodology for assessing (i) the set of the video streams that can be supported with a statistical quality of service requirement, and (ii) the utility earned from video streaming over a link. This methodology is based on the rate-distortion and rate variability-distortion characteristics of the videos. We find that the statistical multiplexing gain and the utility as a function of the video quality level typically exhibit a hump similar to the VD curve.

Unusual case of carpometacarpal dislocation of all the four fingers of ulnar side of hand

Carpometacarpal dislocations of the fingers of ulnar side of the hand are a relatively uncommon injury. They are documented largely by reports of single cases or group of small cases [1] Diagnosis of this unusual form of injury requires high index of suspicion, careful examination and good radiography. Dislocations at the finger carpometacarpal joints are usually high-energy injuries seen commonly in boxers and motorcyclists [2]. Considerable swelling of the back of the hand may mask the characteristic hump at the root of the hand. The diagnosis can be easily missed due to other serious injuries. These injuries account for less than 1% injuries of hand and are frequently overlooked or missed. Disability of the hand is severe in untreated or in those where treatment is delayed.

Magnetic and electrical properties of Gd 7Rh 3 single crystal

Magnetic and electrical properties of hexagonal Gd 7Rh 3 single crystals have been studied by measuring magnetization, magnetic susceptibility, and electrical resistivity. Gd 7Rh 3 shows antiferromagnetic order below T N=141 K as reported by Loebich et al; magnetic anisotropy is small in paramagnetic region. Metamagnetic transitions were observed at 4 K in the external magnetic field up to 130 kOe along the c-axis and in the c-plane. Electrical resistivity shows a characteristic hump just below T N due to the super-zone gap formation along the new Brillouin zone boundaries. High-temperature resistivity indicates that Gd 7Rh 3 has a semi-metallic band structure; the band gap energy 4.9 meV was obtained.

Temperature-dependent magnetic susceptibility behaviour of spinelloid and spinel solid solutions in the systems Fe2SiO4?Fe3O4 and (Fe,Mg)2SiO4?Fe3O4

The magnetic behaviour and Curie temperatures (TC) of spinelloids and spinels in the Fe3O4–Fe2SiO4 and Fe3O4–(Mg,Fe)2SiO4 systems have been determined from magnetic susceptibility (k) measurements in the temperature range −192 to 700 °C. Spinelloid II is ferrimagnetic at room temperature and the k measurements display a characteristic asymmetric hump before reaching a TC at 190 °C. Spinelloid V from the Mg-free system is paramagnetic at room temperature and hysteresis loops at various low temperatures indicate a ferri- to superparamagnetic transition before reaching the TC. The TC shows a non-linear variation with composition between −50 and −183 °C with decreasing magnetite component (XFe3O4). The substitution of Mg in spinelloid V further decreases TC. Spinelloid III is paramagnetic over nearly the total temperature range. Ferrimagnetic models for spinelloid II and spinelloid V are proposed. The TC of Fe3O4–Fe2SiO4 spinel solid solutions gradually decrease with increasing Si content. Spinel is ferrimagnetic at least to a composition of XFe3O4=0.20, constraining a ferrimagnetic to antiferromagnetic transition to occur at a composition of XFe3O4<0.20. A contribution of the studied ferrimagnetic phases for crustal anomalies on the Earth can be excluded because they lose their magnetization at relatively low temperatures. However, their relevance for magnetic anomalies on other planets (Mars?), where these high-pressure Fe-rich minerals could survive their exhumation or were formed by impacts, has to be considered.

Exchange coupling in Fe/NiO/Co film studied by soft x-ray resonant magnetic reflectivity

A 10 nm Fe/5 nm NiO/10 nm Co polycrystalline trilayer prepared by magnetron sputtering has been investigated by resonant magnetic reflectivity of linearly polarized soft x rays (transversal magneto-optical Kerr effect geometry) at the L 3 edges of Fe, Ni, and Co. The exchange coupling in the trilayer, introduced during synthesis, has been altered by cooling through the Neel temperature T N of NiO at three different cooling fields H F C . We show that the chemical structure at the interfaces, the grain size and the magnetic properties of the trilayer are governed by factors such as successive heat treatment, magnetic field applied during synthesis and cooling through T N of NiO. Clear evidence for oxidation of Fe and Co states has been obtained, suggestive for the formation of mixed oxides at the Fe/NiO and NiO/Co interfaces. Oxidized Fe and Co are found to carry a net magnetic moment, which couples to the moments of the metallic states. We find that the coupling between oxidized and metallic Co spins is ferromagnetic, whereas the coupling between oxidized and metallic Fe spins is antiferromagnetic. We observe the presence of two types of excess Ni spins. A rigid excess Ni magnetic moment is induced at the interface during synthesis as follows from the strong asymmetry of the x-ray Kerr loops of the oxidized Co spins at H F C = 0 Oe and metallic Co spins at H F C =240 Oe. Heat treatment leads to appearence of a soft excess Ni magnetic moment, which is ferromagnetically coupled to the metallic Fe and Co spins and exhibits a conventional hysteresis loop. Competing interactions lead to frustrated magnetization at the NiO/Fe interface and cause a tilt of the Fe spins away from the direction of applied magnetic field. This manifests itself in the presence of characteristic humps in the Fe Kerr loops.

Thermodynamics of Molecular Chains with a Local Asymmetric Double-Well Potential

The thermodynamics of one dimensional chains with asymmetric double-well on-site potential is investigated. Pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and in terms of semiclassical approximation. This allows exact calculation and qualitative interpretation of the partition function, free energy and the specific heat function. The specific heat exhibits a characteristic hump similar to the one observed in the structures with a symmetric double-well potential. In some systems, another extremely narrow and extremely high, peak might be developed indicating an entropy driven phase transformation. Comparison between this highly simplified model and more practical approaches to the phenomena of photoinduced phase transformations is discussed underlying the possibility of manifestation of quantum effects in some (spin-crossover) systems.

Thermodynamics of the asymmetric double sinh-Gordon theory in 1+1 dimensions.

Classical thermodynamics of the (1+1)-dimensional asymmetric double sinh-Gordon system is investigated. The pseudo-Schrödinger equation resulting from the transfer integral method is solved numerically and within the semiclassical approximation; the exact results are also given at several temperatures. It is found that the specific heat exhibits a characteristic hump resembling a similar one observed in the systems with a symmetric potential; in some structures, extremely narrow and extremely high peak is developed. The interpretation for this behavior is given.

Quantum conductance of helical nanowires

We have calculated the quantum conductance of N-fold helical metallic nanowires by using recursion-transfer-matrix method. When ${L}_{H}$ (the pitch of the helix) is in a certain range, there appear characteristic humps and dips with steps of ${1G}_{0}$ or ${2G}_{0}$ ${(G}_{0}{=2e}^{2}/h)$ in the conductance. The anomalous conductance originates from the fact that an energy gap opens due to noncircular cross section and shifts toward higher energies with decreasing ${L}_{H}.$

Noninteracting fermions in a one-dimensional harmonic atom trap: Exact one-particle properties at zero temperature

One-particle properties of non-interacting Fermions in a one-dimensional harmonic trap and at zero temperature are studied. Exact expressions and asymptotic results for large Fermion number N are given for the particle density distribution n_0(z,N). For large N and near the classical boundary at the Fermi energy the density displays increasing fluctuations. A simple scaling of these tails of the density distribution with respect to N is established. The Fourier transform of the density distribution is calculated exactly. It displays a small but characteristic hump near 2 k_F with k_F being a properly defined Fermi wave number. This is due to Friedel oscillations which are identified and discussed. These quantum effects are missing in the semi-classical approximation. Momentum distributions are also evaluated and discussed. As an example of a time-dependent one-particle problem we calculate exactly the evolution of the particle density when the trap is suddenly switched off and find a simple scaling behaviour in agreement with recent general results.

Magnetic Susceptibility of Liquid Ag–Ga and Ag–In

The anomalous composition dependence of the magnetic susceptibility in liquid Ag–Ga and Ag–In is investigated within the nearly free electron approximation using simple pseudo-potential theory. The characteristic humps on the silver rich side and the subsequent minima at higher contents (30 at.%) of polyvalent metal are well reproduced by the theory. These features are found to be primarily due to a pronounced modulation of the diamagnetic part of the electronic susceptibility induced by the interactions between the ionic cores and the conduction electrons. The theoretical temperature coefficients of the magnetic susceptibility are in good agreement with the experiment. Unlike to the magnetic susceptibility they pass through a minimum on the silver rich side followed by a maximum at 30 at.% of polyvalent metal, which suggests that the anomalies of the susceptibility vs. composition curve tend to disappear with increasing temperature. Similar to gold based liquid alloys the minima in the electronic suscept...

Energy time dispersion of a new class of magnetospheric ion events observed near the Earth's bow shock

Abstract. We have analyzed high time resolution (\\geq6 s) data during the onset and the decay phase of several energetic (\\geq35 keV) ion events observed near the Earth's bow shock by the CCE/AMPTE and IMP-7/8 spacecraft, during times of intense substorm/geomagnetic activity. We found that forward energy dispersion at the onset of events (earlier increase of middle energy ions) and/or a delayed fall of the middle energy ion fluxes at the end of events are often evident in high time resolution data. The energy spectra at the onset and the decay of this kind of events show a characteristic hump at middle (50-120 keV) energies and the angular distributions display either anisotropic or broad forms. The time scale of energy dispersion in the ion events examined was found to range from several seconds to \\sim1 h depending on the ion energies compared and on the rate of variation of the Interplanetary Magnetic Field (IMF) direction. Several canditate processes are discussed to explain the observations and it is suggested that a rigidity dependent transport process of magnetospheric particles within the magnetosheath is most probably responsible for the detection of this new type of near bow shock magnetospheric ion events. The new class of ion events was observed within both the magnetosheath and the upstream region.Key words. Interplanetary physics (energetic particles; planetary bow shocks)