Ion acoustic solitary wave in electron-positron-ion plasma: effect of Landau damping

A Korteweg-de Vries (KdV) equation with a linear Landau damping term describing weakly nonlinear and weakly dispersive ion-acoustic waves in an electron-positron-ion plasma is derived. It is found that the Landau damping causes the solitary wave amplitude to decay with time. It is also found that in absence of Landau damping, both linear wave phase velocity and solitary wave amplitude decrease with the increase of positron density, whereas, both increase with the increase of positron temperature. On the other hand, the Landau damping rate decreases with the increase of both positron density and temperature.     

Quantitative approach for damage detection of reinforced concrete frames

The objective of this paper is to provide an analytical basis for the quantitative evaluation of damage to a reinforced concrete structure based on the vibration data obtained by using the damage detection technique. A partial reinforced concrete system of a weak beam/strong column moment frame is chosen as an example. A pushover analysis is carried out in order to numerically examine both the story shear-relative displacement characteristics and the associated damage level. In the analysis, a two dimensional nonlinear finite element analysis is employed considering several constitutive models. As a result, the degradation of the stiffness at the damaged story is characterized in association with the story relative displacement. It is also pointed out that the rotation angle of the column-base is highly correlated with the story relative displacement. Based on the analytical findings, quantitative approaches for a structural health monitoring system are suggested considering both the current sensor technologies and those available in the future. Supported by: Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (Base Research (c) (1), Research No. 14550555)     

Far infrared mapping of three Galactic star forming regions: W3(OH), S209 & S187

Three Galactic star forming regions associated with W3(OH), S209 and S187 have been simultaneously mapped in two trans-IRAS far infrared (FIR) bands centered at ≈140 and 200μm using the TIFR 100 cm balloon borne FIR telescope. These maps show extended FIR emission with structures. The HIRES processed IRAS maps of these regions at 12, 25, 60 & 100 ìm have also been presented for comparison. Point-like sources have been extracted from the longest waveband TIFR maps and searched for associations in the other five bands. The diffuse emission from these regions have been quantified, which turns out to be a significant fraction of the total emission. The spatial distribution of cold dust (T < 30 K) for two of these sources (W3(OH) & S209), has been determined reliably from the maps in TIFR bands. The dust temperature and optical depth maps show complex morphology. In general the dust around S209 has been found to be warmer than that in W3(OH) region.     

Prospects of Measuring the Angular Power Spectrum of the Diffuse Galactic Synchrotron Emission with SKA1 Low

The Diffuse Galactic Syncrotron Emission (DGSE) is the most important diffuse foreground component for future cosmological 21-cm observations. The DGSE is also an important probe of the cosmic ray electron and magnetic field distributions in the turbulent interstellar medium (ISM) of our galaxy. In this paper we briefly review the Tapered Gridded Estimator (TGE) which can be used to quantify the angular power spectrum C _? of the sky signal directly from the visibilities measured in radio-interferometric observations. The salient features of the TGE are: (1) it deals with the gridded data which makes it computationally very fast, (2) it avoids a positive noise bias which normally arises from the system noise inherent to the visibility data, and (3) it allows us to taper the sky response and thereby suppresses the contribution from unsubtracted point sources in the outer parts and the side lobes of the antenna beam pattern. We also summarize earlier work where the TGE was used to measure the C _? of the DGSE using 150 MHz GMRT data. Earlier measurements of C _? are restricted to \(\ell \le \ell _{\max } \sim 10^{3}\) for the DGSE, the signal at the larger ? values is dominated by the residual point sources after source subtraction. The higher sensitivity of the upcoming SKA1 Low will allow the point sources to be subtracted to a fainter level than possible with existing telescopes. We predict that it will be possible to measure the C _? of the DGSE to larger values of \(\ell _{\max }\) with SKA1 Low. Our results show that it should be possible to achieve \(\ell _{\max }\sim 10^{4}\) and ～10⁵ with 2 minutes and 10 hours of observations respectively.     

Arsenate sorption by reduced and reoxidised rice soils under the influence of organic matter amendments

Arsenic (As) sorptivity and acetate (pH 4.8) and oxalate (pH 3.0) extractable iron levels were monitored for 180 d, during and after flooding of two As contaminated soils. The effects of three different organic matter supplements/amendments, for example farm yard manure (FYM), municipal solid waste compost (MSWC) and sewage-sludge (SS) on the above parameter were also examined. In nonflooded soils, As sorptivity was mainly influenced by clay content. On flooding, there were large increases in acetate, oxalate extractable iron and As sorptivity. Organic matter addition increased the same parameters. Among the organic matters, SS showed greater effect on As sorption followed by MSWC and FYM. During flooding, As sorption is mainly dependent upon poorly crystalline iron oxide. During oxidation of previously flooded soils, levels of As sorptivity, acetate and oxalate extractable iron decreased rapidly, but did not return to the levels occurring before reduction. SS and MSWC served as binding agents for native and irrigation water As, thereby moderating the rapid As mobilization to the crop rizosphere.     

The effect of q-distributed ions during the head-on collision of dust acoustic solitary waves

The head-on collision of dust acoustic solitary waves are studied in a dusty plasma composed of dust and nonextensive distributed ions by using the extended version of Poincaré-Lighthill-Kuo (PLK) method. The effect of the nonextensivity on the phase shift is studied. It is found that the presence of nonextensive distributed ions plays a significant role on the collision of dust acoustic solitary waves.