Regime analysis of the rheology of spherical and non-spherical particles

In the early stages of granular rheology, the majority of analytical studies were based on granular assembly consisting of spherical particles. This was due to geometric simplicity and feasibility when calculating dynamic variables. Furthermore system limitation emerged as a problem when investigating more complex and realistic considerations. However, in the contemporary research field, with the steadily increasing ability to perform more complex computations and with available resources, attention has focused on non-spherical particles because of their deeper relevance to practical applications. In this work, a 3D shear cell model is developed based on the Discrete Element Method using the commercial software platform “PFC” to study non-spherical particles’ flow characteristics. A comparison is made with those of spherical assemblies. Firstly, the simulation model of annular shear cell consisting of spherical particles is tested with PFC and this agreed well with previous results, thus justifying the use of this tool to analyse the nonspherical level. Then the effect of platen roughness is investigated on spherical particle assembly from the microdynamic perspective, in order to establish a correlation between platen roughness and granular flow dynamics. This is undertaken in terms of particle size that is used to construct the platens. It is found that linearity and non-linearity of gradient profile across several important parameters are distinguishing features affected by variations in platen texture. The externally applied load is the most important aspect that bridges studies where gravity is considered and yet often overlooked. This point is established through in-depth investigation of granular flow in presence and absence of gravity where comparison of an number of flow characteristics is presented. Following this, the effects of particle shape are microdynamically investigated with reference to aspect ratio of non-spherical (ellipsoidal) particles and compared with spherical particles. The following key properties - particle linear velocity, angular velocity, contact normal force, contact shear force, total contact force, total contact moment and porosity - are 4 analysed to explain the effect of variation of the above-mentioned geometric properties on each of these parameters. Then, macrodynamic analysis is performed in a comparative study between spherical particles and ellipsoidal particles of varying aspect ratios with focus on the variables that are important in general constitutive model such as velocity, density and stress tensors. Physics underlying the observation is discussed to highlight effect of particle aspect ratio. Finally and most importantly, regime transition of ellipsoidal particle assembly is contrasted with the findings for spherical particles. In this study, the techniques that are generally used to identify regime transition for granular rheology of spherical particles are tested on flow of non-spherical (ellipsoidal) particles of varying shapes (aspect ratios). This includes correlation between elastically scaled force, kinetically scaled force, coordination number, apparent coefficient of friction and porosity. Some observations are found to be similar and useful for non-spherical particles while others found not suitable for nonspherical particles

Molecular hydrogen from z = 0.0963 DLA towards the QSO J1619+3342

We report the detection of H2 in a zabs= 0.0963 Damped Lyman-{\alpha} (DLA) system towards zem = 0.4716 QSO J1619+3342. This DLA has log N(H I) = 20.55 (0.10), 18.13 < log N(H2) < 18.40, [S/H] = -0.62 (0.13), [Fe/S] = -1.00 (0.17) and the molecular fraction -2.11 < log f(H2) < -1.85. The inferred gas kinetic temperature using the rotational level population is in the range 95 - 132 K. We do not detect C I or C II* absorption from this system. Using R- and V-band deep images we identify a sub-L* galaxy at an impact parameter of 14 kpc from the line of sight, having consistent photometric redshift, as a possible host for the absorber. We use the photoionization code CLOUDY to get the physical conditions in the H2 component using the observational constrains from H2, C I, C II* and Mg I. All the observations can be consistently explained if one or more of the following is true: (i) Carbon is underabundant by more than 0.6 dex as seen in halo stars with Z ~ 0.1 Z_sun, (ii) H I associated with H2 component is less than 50% of the H I measured along the line of sight and (iii) the H2 formation rate on the dust grains is at least a factor two higher than what is typically used in analytic calculations for Milky Way interstellar medium. Even when these are satisfied, the gas kinetic temperature in the models are much lower than what is inferred from the ortho-to-para ratio of the molecular hydrogen. Alternatively the high kinetic temperature could be a consequence of contribution to the gas heating from non-radiative heating processes seen in hydrodynamical simulations.Comment: 10 pages, 4 figues, resubmitted to the MNRAS after minor revision suggested by the refere

RELATIONSHIP COMMITMENT OF PREPAID AND POST-PAID SUBSCRIBERS OF A PRIVATE TELECOMMUNICATION COMPANY IN BANGLADESH By

This study intends to investigate the relationships of communication effectiveness, trust, technical quality, functional quality, and relationship commitment in the context of the prepaid and post-post subscribers of a major private telecommunication company of Bangladesh. It presents a critical appraisal of some important antecedents of subscribers ’ relationship commitment to the respective mobile service provider. Data were collected from 103 prepaid subscribers and 107 post-paid by using self-administered questionnaires. For prepaid subscribers, stepwise regression has showed that technical quality, communication effectiveness, and functional quality have statistically significant relationship with relationship commitment. However, stepwise regression for post-paid subscribers has showed that trust and technical quality have statistically significant relationship with relationship commitment. A clear understanding of important precursors of subscribers &apos; relationship commitment might induce the service provider(s) to germinate and strengthen subscribers &apos; relationship commitment to create a loyal customer bas

Discovery of an HI-rich Gas Reservoir in the Outskirts of SZ-effect Selected Clusters

We report on the detection of three strong HI absorbers originating in the outskirts (i.e., impact parameter, $\rho_{\rm cl} \approx (1.6-4.7) r_{500}$) of three massive ($M_{500}\sim3\times10^{14} M_{\odot}$) clusters of galaxies at redshift $z_{\rm cl} \approx 0.46$, in the $Hubble Space Telescope$ Cosmic Origins Spectrograph ($HST$/COS) spectra of 3 background UV-bright quasars. These clusters were discovered by the 2500 deg$^2$ South Pole Telescope Sunyaev$-$Zel'dovich (SZ) effect survey. All three COS spectra show partial Lyman limit absorber with $N(HI) > 10^{16.5} \ \rm cm^{-2}$ near the photometric redshifts ($|\Delta z/(1+z)| \approx 0.03$) of the clusters. The compound probability of random occurrence of all three absorbers is $<0.02$%, indicating that the absorbers are most likely related to the targeted clusters. We find that the outskirts of these SZ-selected clusters are remarkably rich in cool gas compared to existing observations of other clusters in the literature. The effective Doppler parameters of the Lyman series lines, obtained using single cloud curve-of-growth (COG) analysis, suggest a non-thermal/turbulent velocity of a few $\times10 \ \rm km s^{-1}$ in the absorbing gas. We emphasize the need for uniform galaxy surveys around these fields and for more UV observations of QSO-cluster pairs in general in order to improve the statistics and gain further insights into the unexplored territory of the largest collapsed cosmic structures.Comment: Accepted for publication in ApJ Letters (6 pages

21-cm absorption from galaxies at z ~ 0.3

We report the detection of 21-cm absorption from foreground galaxies towards quasars, specifically z_gal = 0.3120 towards SDSS J084957.97+510829.0 (z_qso = 0.584; Pair-I) and z_gal = 0.3714 towards SDSS J144304.53+021419.3 (z_qso = 1.82; Pair-II). In both the cases, the integrated 21-cm optical depth is consistent with the absorbing gas being a damped Lyman-\alpha (DLA) system. In the case of Pair-I, strong Na I and Ca II absorption are also detected at z_gal in the QSO spectrum. We identify an early-type galaxy at an impact parameter of b ~ 14 kpc whose photometric redshift is consistent with that of the detected metal and 21-cm absorption lines. This would be the first example of an early-type galaxy associated with an intervening 21-cm absorber. The gas detected in 21-cm and metal absorption lines in the outskirts of this luminous red galaxy could be associated with the reservoir of cold H I gas with a low level of star formation activity in the outer regions of the galaxy as reported in the literature for z ~ 0.1 early-type galaxies. In the case of Pair-II, the absorption is associated with a low surface brightness galaxy that, unlike most other known quasar-galaxy pairs (QGPs) i.e. QSO sight lines passing through disks/halos of foreground galaxies, is identified only via narrow optical emission lines detected on top of the QSO spectra. Using SDSS spectra we infer that the emission lines originate within ~ 5 kpc of the QSO sight line, and the gas has metallicity [12+O/H] ~ 8.4 and star formation rate ~ 0.7-0.8 M_sun per yr. The measured 21-cm optical depth can be reconciled with the N(H I) we derive from the measured extinction (A_V=0.6) if either the H I gas is warm or the extinction per hydrogen atom in this galaxy is much higher than the mean value of the Small Magellanic Cloud. (Abridged)Comment: 8 pages, 7 figures, 3 tables (A&A in press

Implications of an updated ultraviolet background for the ionization mechanisms of intervening Ne VIII absorbers

Ne VIII absorbers seen in QSO spectra are useful tracers of warm ionized gas, when collisional ionization is the dominant ionization process. While photoionization by the ultraviolet background (UVB) is a viable option, it tends to predict large line-of-sight thickness for the absorbing gas. Here, we study the implications of the recently updated UVB at low-z to understand the ionization mechanisms of intervening Ne VIII absorbers. With the updated UVB, one typically needs higher density and metallicity to reproduce the observed ionic column densities under photoionization. Both reduce the inferred line-of-sight thicknesses of the absorbers. We find a critical density of $\geq5\times10^{-5}$ cm$^{-3}$ above which the observed N(Ne VIII)/N(O VI) can be reproduced by pure collisional processes. If the gas is of near solar metallicity (as measured for the low ions) then the cooling timescales will be small (<$10^{8}$ yrs). Therefore, a continuous injection of heat is required in order to enhance the detectability of the collisionally ionized gas. Using photoionization models we find that in almost all Ne VIII systems the inferred low ion metallicity is near solar or supersolar. If we assume the Ne VIII phase to have similar metallicities then photoionization can reproduce the observed N(Ne VIII)/N(O VI) without the line-of-sight thickness being unreasonably large and avoids cooling issues related to the collisional ionization at these metallicities. However the indication of broad Ly$\alpha$ absorption in a couple of systems, if true, suggests that the Ne VIII phase is distinct from the low ion phase having much lower metallicity.Comment: 11 pages, 5 figures, 2 tables. Accepted for publication in MNRA

A Causal Study on the Antecedents of Retail Shoppers’ Repatronage Intention

This study has investigated the impact of few important antecedents (such as perceived service quality, perceived product quality, store assortment, price perception, trust, and commitment) of shoppers’ satisfaction and how these antecedents as mediated through shoppers’ satisfaction affect shoppers’ repatronage intention. A multi-item structured questionnaire was used to collect data from 210 shoppers of a major retail chain operating in Dhaka, Bangladesh. Validity and reliability of each construct were assessed by employing Confirmatory Factor Analysis (CFA) using AMOS and the results were satisfactory. Structural Equation Modeling (SEM) was performed to assess the data-model fit and examine the causal paths to test the proposed hypotheses. Out of seven hypotheses, five hypotheses were supported empirically as per SEM results. Perceived product quality, price perception, perceived service quality, and product assortment came out to be the strong antecedents of shoppers’ satisfaction with high statistical significance. Furthermore, shoppers’ satisfaction demonstrated the most powerful impact on shoppers’ repatronage intention. Thus, the fifth hypothesis was supported.  This study might encourage the retail operators to identify the needful to make the shoppers to become steady patrons of their stores. Key Words: Perceived Service Quality, Perceived Product Quality, Store Assortment, Price Perception, Trust, Commitment, Customer Satisfaction, and Repatronage Intention

The Sinoman Hadrah Cultural Communication of Banjar Tribe as Islamic Media and Art for Welcoming Sei Teras Honorary Guest

Indonesia is rich in ethnicity and culture. The diversity of cultures in Indonesia is a manifestation of Indonesia's heritage as Bhinneka Tunggal Ika country. Indonesia's diversity of art and culture are explored, develop, and preserve hereditary. The effort has quite an important advantage for the existing art and culture. Art characteristics show where it is from and it is related to communication studies. Traditional cultural art messages not only show as a drama but also as a communication medium that is embedded in cultural values of tribe and region. Sinoman hadrah art grows and thrives at Banjar tribe as medium and art inanimate heritage in important event especially for welcoming honorary guest also as an Islamic medium for inviting young generation to live in harmony and dignity. This research used a qualitative-descriptive approach. The research data were analyzed by used Miles and Huberman's descriptive analysis model based on perception theory. The results show culture communication in sinoman hadrah performance of Banjar tribe being Islamic art and medium for welcoming honorary guests of Sei Teras village at Kapuas Kuala as well as culture hereditary containing moral, harmony, Islamic relationship and will be preserved by future generations as part of tribe honor. Keywords: Culture Communication, Tribe, Sinoman Hadrah, Medium, Art, Heritage DOI: 10.7176/RHSS/11-18-05 Publication date:September 30th 202