277 research outputs found
Internet of Things-Enabled Overlay Satellite-Terrestrial Networks in the Presence of Interference
In this paper, we consider an overlay satellite-terrestrial network (OSTN)
where an opportunistically selected terrestrial IoT network assist primary
satellite communications as well as access the spectrum for its own
communications in the presence of combined interference from extra-terrestrial
and terrestrial sources. Hereby, a power domain multiplexing is adopted by the
IoT network by splitting its power appropriately among the satellite and IoT
signals. Relying upon an amplify-and-forward (AF)-based opportunistic IoT
network selection strategy that minimizes the outage probability (OP) of
satellite network, we derive the closed-form lower bound OP expressions for
both the satellite and IoT networks. We further derive the corresponding
asymptotic OP expressions to examine the achievable diversity order of two
networks. We show that the proposed OSTN with adaptive power splitting factor
benefits IoT network while guaranteeing the quality of service (QoS) of
satellite network. We verify the numerical results by simulations.Comment: 7 pages, 3 figures, Submitted to National Conference on
Communications 202
A Si-micromachined 48-stage Knudsen pump for on-chip vacuum
This paper describes a thermal transpiration-driven multistage Knudsen pump for vacuum pumping applications. This type of pump relies upon the motion of gas molecules from the cold end to the hot end of a channel in which the flow is restricted to the free molecular or transitional regimes. To achieve a high compression ratio, 48 stages are cascaded in series in a single chip. A five-mask, single silicon wafer process is used for monolithic integration of the designed Knudsen pump. The pump has several monolithically integrated Pirani gauges to experimentally measure the vacuum pumping characteristics of the pump. It has a footprint of 10.35 × 11.45 mm 2 . For an input power of 1350 mW, the fabricated pump self-evacuates the encapsulated cavities from 760 to ≈ 50 Torr, resulting in a compression ratio of 15. It also pumps down from 250 to ≈ 5 Torr, resulting in a compression ratio of 50. Each integrated Pirani gauge requires ≈ 3.9 mW of power consumption, and its response is sufficiently sensitive in the operating pressure range of 760–1 Torr.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98610/1/0960-1317_22_10_105026.pd
Structural and compositional properties of 2D CH3NH3PbI3 hybrid halide perovskite: a DFT study
Two-dimensional (2D) hybrid halide perovskites have been scrutinized as candidate materials for solar cells because of their tunable structural and compositional properties. Results based on density functional theory demonstrate its thickness-dependent stability. We have observed that the bandgap decreases from the mono- to quad-layer because of the transformation from 2D towards 3D. Due to the transformation, the carrier mobility is lowered with the corresponding smaller effective mass. On the other hand, the multilayer structures have good optical properties with an absorption coefficient of about 105 cm−1. The calculated absorption spectra lie between 248 nm and 496 nm, leading to optical activity of the 2D multilayer CH3NH3PbI3 systems in the visible and ultraviolet regions. The strength of the optical absorption increases with an increase in thickness. Overall results from this theoretical study suggest that this 2D multilayer CH3NH3PbI3 is a good candidate for photovoltaic and optoelectronic device applications
Raman Signatures of Strong Kitaev Exchange Correlations in (NaLi)IrO : Experiments and Theory
Inelastic light scattering studies on single crystals of
(NaLi)IrO ( and ) show a polarization
independent broad band at ~2750 cm with a large band-width ~cm. For NaIrO the broad band is seen for temperatures ~K and persists inside the magnetically ordered state. For Li doped
samples, the intensity of this mode increases, shifts to lower wave-numbers and
persists to higher temperatures. Such a mode has recently been predicted
(Knolle et.al.) as a signature of the Kitaev spin liquid. We assign the
observation of the broad band to be a signature of strong Kitaev-exchange
correlations. The fact that the broad band persists even inside the
magnetically ordered state suggests that dynamically fluctuating moments
survive even below . This is further supported by our mean field
calculations. The Raman response calculated in mean field theory shows that the
broad band predicted for the spin liquid state survives in the magnetically
ordered state near the zigzag-spin liquid phase boundary. A comparison with the
theoretical model gives an estimate of the Kitaev exchange interaction
parameter to be ~meV.Comment: 14pages 4 figure
De novo assembly and characterization of transcriptomes of early-stage fruit from two genotypes of Annona squamosa L. with contrast in seed number
Non-alcoholic fatty liver disease may not be a severe disease at presentation among Asian Indians
Aim: To evaluate the clinical and biochemical profile of patients with non alcoholic fatty liver disease (NAFLD) and to assess their histological severity at presentation. Methods: Consecutive patients presenting to the liver clinic of All India Institute of Medical Sciences (AIIMS) with raised transaminases to at least 1.5 times upper limit of normal, and histologically confi rmed non-alcoholic fatty liver disease were included. Patients who had significant alcohol intake or positive markers of other liver diseases or who were taking drugs known to produce fatty liver were excluded. The clinical, biochemical and histological profi le of this group was studied. Results: Fifty-one patients with NAFLD formed the study population. Their median age and BMI were 34(17-58) years and 26.7(21.3-32.5) kg/m2 respectively and 46 (90.1%) were males. The majority of the patients had mild inflammation, either grade 1 [32 (63%)] or grade 2 [16 (31%)] and only 3 (6%) patients had severe (grade 3) infl ammation. Twenty-three (45%), 19 (37%), 8(16%) and 1(2%) patient had stage 0, 1, 2 and 3 fi brosis respectively on index biopsy and none had cirrhosis. On univariate analysis, triglyceride levels more than 150 mg % (OR = 7.1; 95% CI: 1.6-31.5, P = 0.002) and AST/ALT ratio > 1 (OR = 14.3; 95% CI: 1.4-678.5, P = 0.008) were associated with high grades of inflammation and none was associated with advanced fibrosis. On multivariate logistic regression analysis, hypertriglyceridemia >150 mg% was the only factor independently associated with presence of high grade of infl ammation (OR = 1.6; 95% CI: 1.3-22.7, P = 0.02), while none was associated with advanced fi brosis. Triglyceride levels correlated positively with infl ammatory grade (r = 0.412; P = 0.003). Conclusion: NAFLD in North Indian patients is a disease of young over-weight males, most of whom are insulin resistant and they tend to have a mild histological disease at presentation
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