A local structure analysis method based on convergent‐beam electron diffraction (CBED) has been used for refining isotropic atomic displacement parameters and five low‐order structure factors with ...sin gθ/λ ≤ 0.28 Å−1 of potassium tantalate (KTaO3). Comparison between structure factors determined from CBED patterns taken at the zone‐axis (ZA) and Bragg‐excited conditions is made in order to discuss their precision and sensitivities. Bragg‐excited CBED patterns showed higher precision in the refinement of structure factors than ZA patterns. Consistency between higher precision and sensitivity of the Bragg‐excited CBED patterns has been found only for structure factors of the outer zeroth‐order Laue‐zone reflections with larger reciprocal‐lattice vectors. Correlation coefficients among the refined structure factors in the refinement of Bragg‐excited patterns are smaller than those of the ZA ones. Such smaller correlation coefficients lead to higher precision in the refinement of structure factors.
A new strategy for improving precision and sensitivity in the refinement of crystal structure factors is proposed. This technique will help to precisely determine the chemical bonding states of crystalline materials, which are closely related to their physical properties.
This paper presents the effects of ballistic impact damage on the mechanical behaviour of composite honeycomb sandwich panels. The panels are composed of facesheets made of carbon fibre reinforced ...laminates and the Nomex honeycomb core. Ballistic tests were conducted in a shooting range using live projectiles of three different calibres. The specimens were subjected to both normal and oblique impacts to simulate the damage to composite sandwich structures that can be inflicted by the use of small weapons or by fragments of anti-aircraft ammunition. The modes and extent of the damage induced have been analysed using optical microscopy, X-ray inspections and computer tomography methods. Structural performance of the intact and ballistically damaged panels has been investigated experimentally using in-plane compression tests, and numerically, based on the finite element modelling and analysis. The reduction in the load-carrying ability caused by the ballistic damage has been assessed for the panels under consideration and compared with that predicted by numerical simulations.
By systematically searching the region of far infrared loops, we found a number of huge cavity-like dust structures at
60
μ
m
and
100
μ
m
IRIS maps. By checking these with AKARI maps (
90
μ
m
and
140
...μ
m
), two new cavity-like structures (sizes
∼
2.7
pc
×
0.8
pc
and
∼
1.8
pc
×
1
pc
) located at R.A. (
J
2000
)
=
14
h
41
m
23
s
and Dec.
(
J
2000
)
=
-
64
∘
04
′
17
′
′
and R.A.
(
J
2000
)
=
05
h
05
m
35
s
and Dec.
(
J
2000
)
=
-
69
∘
35
′
25
′
′
were selected for the study. The difference in the average dust color temperatures calculated using IRIS and AKARI maps of the cavity candidates were found to be
3.2
±
0.9
K
and
4.1
±
1.2
K
, respectively. Interestingly, the longer wavelength AKARI map gives larger values of dust color temperature than that of the shorter wavelength IRIS maps. Possible explanation of the results will be presented.
The dust-grain structure in the far infrared region under IRAS (Infrared Astronomical Satellite) Survey was studied using sky view virtual observatory. In order to find the possible far infrared ...cavity, we used SIMBAD database. In this paper, we discuss about the dusty environment of a far infrared cavity around the AGB star located at R.A. (J2000) =01h 41m 01s and Dec (J2000) = 71o 04’ 00” lying within far infrared loop G125+09 in the far infrared IRAS maps. A cavity like structure (major diameter ∼ 2.55 pc & minor diameter ∼ 0.77 pc) is found to lie at R.A. (J2000)= 01h 46m 57.2s and DEC (J2000)= 71o 24’ 57.1”, located at a distance ∼ 220 pc from the star. We studied the distribution of flux density, dust color temperature, dust mass, inclination angle, visual extinction and FIR spectral distribution of the cavity. We further studied the distribution of Planck function along extension and compression. The dust color temperature is found to lie in the range (19.7±0.65) K to 21.1±0.35) K which shows the cavity is isolated and stable. Product of visual extinction and dust color temperature is found to be less than one. A possible explanation of the results will be discussed.
BIBECHANA 17 (2020) 42-49
A survey was conducted at Musikot, Western Rukum, Nepal in 2019 to analyze the economic results of vegetable seed production using a well-structured pre-tested questionnaire. The average landholding ...per household was 8.14 ropani (1 ropani = 0.05 ha), as 33.74% of landholding (equal to 50.36% of the cultivated land) was under vegetable seed production. Vegetable seed production generated 46% of on-farm income equal to 23% of total household income. The share of on-farm activities and off-farm activities in household income was almost equal. 64% of the farming households were food self-sufficient. 39% of the farmers were new to the vegetable seed production enterprise whereas 5% of the farmers were involved from 40 years. 49% of the cost in vegetable seed production was incurred in labor. About eight thousand rupee were sufficient to run a vegetable seed production enterprise per ropani that had made a gross margin of NRs 9,614.36 per ropani. Radish occupied 46.5% of the vegetable seed producing land and generated 53.5% of the vegetable seed revenue. BCR of 2.21 suggested that vegetable seed production enterprise brings NRs 2.21 at the investment of NRs 1. Swiss-chard had the highest price spread (90%) whereas radish and turnip had the lowest (57%). Sensitivity analysis showed that vegetable seed production enterprise was a viable business even after a 20% increase in cost and 20% reduction of revenue simultaneously. Disease infestation and insect attack were two major production problems and price fluctuation and inadequate market information were two major marketing problems faced by vegetable seed producers at Musikot, Western-Rukum, Nepal.
A low flux density region nearby white dwarf WD1334-678 in the 140 µm AKARI survey maps has been systematically searched and found a far-infrared cavity centered at R.A. (J2000) = 13h38m14.4s, ...Dec.(J2000) = −68◦40’42”, in which minimum flux is 19.5 MJy/sr at 90 µm wavelength. The physical properties (Size, dust color temperature, dust mass) and thermodynamic property (Planck function distribution) of the cavity using 140 µm and 90 µm AKARI survey data. The size of the cavity is found to be 0.17◦× 0.12◦ has been presented. The dust color temperature is found in the range 17.70 ± 0.01 K to 18.81 ± 0.01 K. The Plank function distribution along major and minor diameters shows a very good agreement with sinusoidal fitting. The period of oscillation of dust particles along major and minor diameters are 3.2 Wm-2Sr-1Hz-1arcmin-1and 1.6 Wm-2Sr-1Hz-1arcmin-1, respectively.
BIBECHANA 18 (2) (2021) 130-137
The spin vector orientation of 1302 SDSS (Sloan Digital Sky Survey) galaxies in Supercluster S173+014+0082 having redshift 0.076 to 0.091 has been analysed. The positions, position angles and ...inclination angles of galaxies are used to convert two-dimensional observed parameters into three-dimensional angular momentum vectors of the galaxy using the `position angle-inclination' method. The expected isotropic distribution curves are determined performing numerical simulation by generating 107 virtual galaxies. The observed distribution is compared with the expected isotropic distribution curves using three statistical tools namely Chi-square test, auto-correlation test and Fourier test. Redshift map is studied and found that the distributions fit with the Gaussian. No preferred alignment of angular momentum vectors is noticed, supporting Hierarchy model of galaxy formation.
BIBECHANA 18 (2021) 26-32
A systematic search of dust structure in the far infrared (100 μm and 60 μm) under Infrared Astronomical Satellite (IRAS) survey was performed using Sky View virtual Observatory. In order to find the ...possible candidate of cavity structure not yet studied, we used SIMBAD database to locate discrete sources in the region. A new relatively symmetric spherical cavity like structure (size: 1.354 pc x 0.971 pc) at R.A.(J2000) =08h 03m 01.65s, Dec.(J2000) = -360 35' 47.9" was found at the distance of about 2800 pc. In this article, we have calculated dust color temperature, dust mass and size. We also studied the flux density variation and then calculated temperature and mass profile of the dust of p-AGB star using data reduction software Aladin2.5 and Aladin8.0. We have studied a cavity like structure centered at R.A.(J2000) = 08h 04m 07.21s, Dec.(J2000) = -370 11' 48.0". The dust color temperature is found to lie in the range 21.6 ± 0.09 K to 22.5 ± 0.05 K with an offset of 0.9 K. Such low off set suggests that the post AGB is in local thermodynamic equilibrium. The total mass of the dust in the cavity structure is found about 5.93 x 1025 Kg (0.00003M⊙)BIBECHANA 1 6 (2019) 23-30
We study the spatial orientations of angular momentum vectors of galaxies in six rotating clusters (A954, A1139, A1399, A2162, A2169 and A2366) that show a single number-density peak around the ...cluster centre with a spatial segregation of high- and low-velocity galaxies. The positions, position angles and inclination angles are used to covert two-dimensional observed parameters into three-dimensional angular momentum vectors of the galaxy. The expected isotropic distribution curves are determined by running numerical simulations. The chi-square, autocorrelation, Fourier, Kolmogorov-Smirnov and Kuiper V tests are carried out in order to examine non-random effects in the expected isotropic distributions. In general a random orientation of angular momentum vectors of galaxies is found in all six rotating clusters supporting hierarchy model of galaxy formation. It is found that the vanishing angular momenta is preferred by the rotating clusters which are in dynamical equilibrium and have larger value of velocity dispersion. Possible explanations of the results will be discussed.
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