Fundamental limits of many-user MAC with finite payloads and fading

Consider a (multiple-access) wireless communication system where users are connected to a unique base station over a shared-spectrum radio links. Each user has a fixed number $k$ of bits to send to the base station, and his signal gets attenuated by a random channel gain (quasi-static fading). In this paper we consider the many-user asymptotics of Chen-Chen-Guo'2017, where the number of users grows linearly with the blocklength. In addition, we adopt a per-user probability of error criterion of Polyanskiy'2017 (as opposed to classical joint-error probability criterion). Under these two settings we derive bounds on the optimal required energy-per-bit for reliable multi-access communication. We confirm the curious behaviour (previously observed for non-fading MAC) of the possibility of perfect multi-user interference cancellation for user densities below a critical threshold. Further we demonstrate the suboptimality of standard solutions such as orthogonalization (i.e., TDMA/FDMA) and treating interference as noise (i.e. pseudo-random CDMA without multi-user detection).Comment: 38 pages, conference version accepted to IEEE ISIT 201

Design and Implementation of Position Estimator Algorithm on Voice Coil Motor

Voice Coil Motors (VCMs) have been an inevitable element in the mechanisms that have been used for precise positioning in the applications like 3D printing., micro-stereolithography., etc. These voice coil motors translate in a linear direction and require a high accuracy position sensor that amounts for a major part in the budget. In this research work., an effort has been made to design and implement an algorithm that would predict the displacement of VCM and eliminate the need of high cost sensors. VCM was integrated with dSPACE DS1104 R&D controller via linear current amplifier (LCAM) which acts as a driver circuit for VCM. Sine input was given to VCM with various amplitude and frequency and the corresponding displacement is measured by using linear variable differential transformer (LVDT). The position estimator algorithm is also implemented at the same time on VCM and its output is compared with that of LVDT. It is observed that there is 97.8 % accuracy in between algorithm output and LVDT output. Further., PID controller is used in integration with the novel algorithm to minimize the error. The estimator algorithm is tested for various amplitudes and frequencies and it is found that it has a very good agreement of 99.2% with the actual displacement measured with the help of LVDT

The Response of Serum Cortisol and Leptin Levels to Academic Stress

Background: Medical students are subjected to various types of stress during the academic course and they react differently. This study is an attempt to establish a relationship between the coping abilities, serum cortisol and leptin levels in response to academic examination stress in first year medical students. Methods: Thirty four 1st year medical students between 18 to 21 yrs of age were randomly selected and their coping abilities were assessed using the State Trait Anxiety Inventory. Two fasting blood samples were drawn, one on the day of examination (Situation I) and the second after the completion of the examination (Situation II). Serum cortisol and leptin levels were estimated using a standardized RIA Kit and the levels obtained were correlated with the psychometric data. Results: The results showed increased levels of cortisol prior to examination in the poor adjusters in comparison to the good adjusters. The levels of cortisol decreased after examination in both good and poor adjusters with the poor adjusters showing higher levels. On the other hand, leptin levels increased in good adjusters in comparison with poor adjusters in Situation I and in Situation II the good adjusters showed a marginal decrease and poor adjusters maintained the same levels of leptin. Conclusion: Cortisol and leptin respond inversely to academic stress. Cortisol levels sharply decline from stressful to post-stressful situation indicating the wane of stress

Unique transcriptomic landscapes identified in idiopathic spontaneous and infection related preterm births compared to normal term births.

Preterm birth (PTB) is leading contributor to infant death in the United States and globally, yet the underlying mechanistic causes are not well understood. Histopathological studies of preterm birth suggest advanced villous maturity may have a role in idiopathic spontaneous preterm birth (isPTB). To better understand pathological and molecular basis of isPTB, we compared placental villous transcriptomes from carefully phenotyped cohorts of PTB due to infection or isPTB between 28-36 weeks gestation and healthy term placentas. Transcriptomic analyses revealed a unique expression signature for isPTB distinct from the age-matched controls that were delivered prematurely due to infection. This signature included the upregulation of three IGF binding proteins (IGFBP1, IGFBP2, and IGFBP6), supporting a role for aberrant IGF signaling in isPTB. However, within the isPTB expression signature, we detected secondary signature of inflammatory markers including TNC, C3, CFH, and C1R, which have been associated with placental maturity. In contrast, the expression signature of the gestational age-matched infected samples included upregulation of proliferative genes along with cell cycling and mitosis pathways. Together, these data suggest an isPTB molecular signature of placental hypermaturity, likely contributing to the premature activation of inflammatory pathways associated with birth and providing a molecular basis for idiopathic spontaneous birth

SHEAR BEHAVIOR OF STEEL FIBER REINFORCED PRECAST PRESTRESSED CONCRETE BEAMS

Precast industries constantly look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers in concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. Shear behavior of concrete members mainly depends on the compressive strength of concrete, shear span to depth ratio (a/d), amount of stirrups, aggregate interlock and dowel action of longitudinal reinforcement. The present study focuses on the shear behavior of steel fiber reinforced PSC beams with different volume fractions i.e., 0.50% and 1.00%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested with a shear span to depth ratio of 2.4 to simulate shear dominant behavior. Strain gauges were attached to the strands at loading point and at the center of shear span (a/2) to measure strain variation at different stages such as prestressing, de-tensioning and testing. During experimentation, load-deflection and strand strain was recorded. Test results indicate that the addition of steel fibers improved the shear resistance and ductility of the prestressed concrete beams

Optimal placement of Femto base stations in enterprise femtocell networks

Femto cells a.k.a. Low Power Nodes (LPNs) are deployed to improve indoor data rates as well as reduce traffic load on macro Base Stations (BSs) in 4G/LTE cellular networks. Indoor UEs getting high SNR (Signal-to-Noise Ratio) can experience good throughput, but SNR decreases at faster rate due to obstacles, present along the communication path. Hence, efficient placement of Femtos in enterprise buildings is crucial to attain desirable SNR for indoor users. We consider obstacles and shadowing effects by walls and include them in the system model. We develop a Linear Programming Problem (LPP) model by converting convex constraints into linear ones and solve it using GAMS tool, to place Femtos optimally inside the building. Our extensive experimentation proves the optimal placement of Femtos achieves 14.41% and 35.95% increase in SNR of indoor UEs over random and center placement strategies, respectively

Laboratory simulations show diabatic heating drives cumulus-cloud evolution and entrainment

Clouds are the largest source of uncertainty in climate science, and remain a weak link in modeling tropical circulation. A major challenge is to establish connections between particulate microphysics and macroscale turbulent dynamics in cumulus clouds. Here we address the issue from the latter standpoint. First we show how to create bench-scale flows that reproduce a variety of cumulus-cloud forms (including two genera and three species), and track complete cloud life cycles—e.g., from a “cauliflower” congestus to a dissipating fractus. The flow model used is a transient plume with volumetric diabatic heating scaled dynamically to simulate latent-heat release from phase changes in clouds. Laser-based diagnostics of steady plumes reveal Riehl–Malkus type protected cores. They also show that, unlike the constancy implied by early self-similar plume models, the diabatic heating raises the Taylor entrainment coefficient just above cloud base, depressing it at higher levels. This behavior is consistent with cloud-dilution rates found in recent numerical simulations of steady deep convection, and with aircraft-based observations of homogeneous mixing in clouds. In-cloud diabatic heating thus emerges as the key driver in cloud development, and could well provide a major link between microphysics and cloud-scale dynamics