Density Measurements in the Base Flow Region of HRV Afterbody-Nozzle Configuration

A preliminary study to document the mean density field using Background Oriented Schlieren (BOS) has been carried out on a 1:10 scaled model of HSTDV afterbodynozzle configuration system at a freestream Mach number of 3.5 with unit Reynolds number of 38x106 per meter. The results show that the mean density field is quite adequately captured with the BOS technique with the derived Schlieren results matching well with conventional Schlieren images and with density data derived from pressure measurements on the ramp. While the data at nozzle exit is not reliable due to strong asymmetric 3D effects, presumably due to the flow expansion on the cowl lip influencing the flow field in the vicinity, the results show that flow field variable like density shows local effects better (e.g. local effect of the cowl extension) and this has been captured by the BOS whereas the wall static pressures do not show this effect. Streamwise variation of the density along the jet centerline and parallel to the ramp are presented showing that useful quantitative information can be extracted through this technique. The results would be useful for CFD code

Acoustic characterization of jet interaction with launch structures during lift-off

The structures that constitute the environment surrounding the launchvehicle affectthe noise levels experiencedbyit during liftoff. Earlier studies modeled the launch scenario by incorporating a jet impinging on plate geometries,either flat or curved, ignoring contributions from the components of the launch structures such as the launchplatform. Very little is knownaboutthe effect of the structures on the propagationof noise from the jet exhaust towardthe vehicle. This renders any effort to modify them for noise reduction quite challenging. The present study attemptsto address this concern by investigating the contribution of a principal launch structure component, namely, thelaunch platform, toward the acoustic and flowfield around a generic launch vehicle exhausting on a generic jet blastdeflector. The measurements include flowfield visualizations and aeroacoustic measurements using microphones inthe near and far field. The results indicate that the presence of the launch platform increased the noise levelsexperienced by the vehicle beyond certainL∕De. It is also observed that replacing the solid launch platform with aperforated one leads to lower levels of noise compared to the solid one but still higher than the case where launchplatform is absent

Colorectal polyps and heterotrophic esophageal polyp of colon in a paediatric cohort in South India

Background: Clinical profile of polyps in paediatric cases are less in South India. Juvenile Polyps were the most common polyps in paediatric cases described in literature, presenting as LGI bleed. The aim of the study is to describe the clinical profile of colorectal polyps in paediatric population in a single tertiary care centre in South India.Methods: Paediatric cases between 0 and 16 years of age who underwent colonoscopy in our department from January 2002 to July 2018 were included from database. These cases were retrospectively analysed for presence of polyps, clinical presentation, indication for colonoscopy, histopathology of the resected polyps and other demographic details.  Incomplete procedures were excluded.Results: About 166 paediatric cases underwent colonoscopy in the study period. 21 cases (12.65%) had colorectal Polyps. 85.7% of the polyps were in recto sigmoid region. Most common histological type was Juvenile Polyp (51.6%). One infant had sessile polyp in descending colon which was reported as heterotrophic esophageal mucosa in histopathology. LGI bleed was the most common presentation in children with polyps (66.6%).Conclusions: The prevalence of polyps in our cohort was 12.65%. Solitary Juvenile Polyp was the most common polyp in children, with lower GI bleed as the most common presenting feature. Rare case of heterotrophic esophageal polyp was seen in descending colon

Unveiling mediastinal pathology: role of EUS guided fine needle aspiration in diagnosing mediastinal lesions

Background: Mediastinal lesion is the focus of investigation in diagnosis of infective, granulomatous or neoplastic pathology of respiratory system. Metastatic mediastinal node assessment is an integral part of oncological management. EUS provides access to sampling of mediastinal mass, sub-carinal and aorto-pulmonary nodes. This study aims to assess the clinical impact, diagnostic yield and safety of EUS guided FNA for mediastinal lesions.Methods: Retrospective analysis of prospectively collected data of 72 cases of mediastinal lesions between January 2014 and December 2017 was done. EUS-FNA was performed with a linear echoendoscope using a 22- or 25-gauge needle. Adequacy of cellularity was assessed by on site pathologist. Patient data (demographics, intervention and follow-up) were prospectively collected and introduced in a predefined computer database for later review.Results: EUS-FNA was performed from 57 lymph nodes and 15 mediastinal masses. Adequate samples were obtained in 67 of 72 patients (93.05%). All mediastinal masses were malignant and were identified in the 3rd, 5th and 6th decade of life. Of the 57 lymph nodes, 15 were malignant, 28 had granulomatous lymphadenitis of which 16 individuals became asymptomatic after anti tubercular therapy. Sample was inadequate in 5 circumstances. No major complications were encountered with the procedure in any of the individuals.Conclusions: EUS guided tissue diagnosis is a safe technique and our data supports the use of EUS-FNA in work-up of mediastinal lesions. It is minimally invasive, accurate and has easy access to mediastinum. It has significant impact on patient diagnosis, management and should be considered over other invasive techniques

Clinicopathological profile of colorectal polyps: retrospective analysis from tertiary care center in Southern India

Background: Colorectal Cancer is the fourth most commonly diagnosed and chronological changes in colorectal polyps and cancer is important in efficacy of screening strategies. In this study, we aimed to compare clinicopathological features of colorectal polyps and also aimed to characterise the distribution and the pathological features of polyps during an 18-year period divided in to two groups.Methods: This is retrospective analysis of cases that underwent colonoscopy and found to have colorectal polyps were re-viewed retrospectively for 18 year period are retrieved. 18 year period was divided in to 2001 to 2010 and 2011 to 2018.Results: Among 4230 patients underwent colonoscopy between January 2001 and September 2018, 1356 were excluded; of the remaining 2874, 986 were found to have 1,272 polyps. 306 patients had 412 polyps in 2001 to 2010 group and 680 patients had 860 polyps in 2011 to 2018 group. Adenomas on the left sided colon were significantly higher in the first time period (40.2% vs 30%, p <0.0003). Polyps on the right sided colon were significantly higher in the second time period (37.3% vs 36.9%, p <0.0005). The most common histology in the both periods is tubular adenoma. Histology of adenomas with high grade dysplasia were significantly more in first period (12.4% vs 7.6%, p <0.005).Conclusions: Our data shows shift in polyps from left side to right side colon in recent years. There was no significant change in shift in advanced adenomas from left side to right side of colon

Challenges in Clock Synchronization for On-Site Coding Digital Beamformer

Typical radio frequency (RF) digital beamformers can be highly complex. In addition to a suitable antenna array, they require numerous receiver chains, demodulators, data converter arrays, and digital signal processors. To recover and reconstruct the received signal, synchronization is required since the analog-to-digital converters (ADCs), digital-to-analog converters (DACs), field programmable gate arrays (FPGAS), and local oscillators are all clocked at different frequencies. In this article, we present a clock synchronization topology for a multichannel on-site coding receiver (OSCR) using the FPGA as a master clock to drive all RF blocks. This approach reduces synchronization errors by a factor of 8, when compared to conventional digital beamformer

Packable and Readily Deployable Tightly Coupled Dipole Array (TCDA) With Integrated Planar Balun

To overcome the limited payload dedicated to onboard antennas for CubeSat/SmallSat applications, this paper presents a novel, foldable, dual-polarized Tightly Coupled Dipole Array (TCDA). In comparison to previous vertical feeds used for TCDAs, this array integrates a planar microstrip balun feed to enable foldability. The proposed array attains 5.4:1 (0.6-3.20 GHz) impedance bandwidth with VSWR \u3c 3 at broadside and scans down to 45° at all azimuth planes. Notably, a substrate-integrated in-plane folding mechanism based on Lamina Emergent Torsion (LET) joints is employed to achieve foldability coupled with a simple fabrication process. The average simulated radiation efficiency was 95% across the band. A 5×8 prototype array was fabricated and tested to verify the finite array\u27s foldability, bandwidth, and gain performance. This prototype achieves 80% one-dimensional size reduction, yielding 60% overall volume reduction. Consequently, the array prototype can be folded and stowed in a compact volume of 1.4U (25 cm ×7.2 cm ×9 cm)

Optimized differential TCDA (D-TCDA) with novel differential feed structure

Modern phased arrays require large instantaneous bandwidths, wide fields of view, and low profiles to conduct multiple functions. Many of these phased arrays rely on emerging high speed ADCs and advanced balanced transceivers. The benefits of balanced front-ends include improved linearity, dynamic range, isolation, and noise resilience. The application of a differential phased array in such a system removes extraneous losses caused by baluns, though the issue of feed-borne E-plane scan resonances must be considered. We address the E-plane scan resonance issue through an improved Balanced Wideband Impedance Transformer (BWIT) feed for the ultra-wideband (UWB) Tightly Coupled Dipole Array (TCDA). This BWIT feed has already demonstrated mitigated common-modes over a 3:1 bandwidth ratio while scanning to low angles. Here, our differential TCDA (D-TCDA) is developed for the L-C band (viz. 1.0 GHz to 6.1 GHz) with emphasis on resonance-free wide-angle scanning. Rigorous EM model and circuit analysis is included to verify the BWIT performance. Under a VSWR \u3c 3 definition, the improved array achieves a 6:1 impedance bandwidth ratio (BWR) with resonance-free scanning in all planes. An exception is the H-plane scanning at 60◦ where the VSWR \u3c 4. Array simulations are verified with measurements for an 8×8 single-polarized prototype

Low-Cost S-Band Reconfigurable Monopole/Patch Antenna for CubeSats

The development of reconfigurable antennas compatible with a CubeSat form factor can aid several space missions. Often, satellite missions require multiple wireless links with the same radio, but the design of such antennas is challenging due to the mechanical constraints and the limited power aboard a CubeSat. In this article, we present a unique reconfigurable antenna concept enabled by adhesive polyimide tapes. The presented antenna can switch from a conventional patch to a monopole-like antenna with minimal actuation complexity. This reconfiguration provides choices for polarization, pattern, and gain without use of active components for size, cost and power consumption reductions. The frequency of operation is S-band (2.4 GHz), and the antenna achieves S_{11} \u3c -10 dB for both reconfiguration states. Measurements compare well with simulations in both states

Techniques for Achieving High Isolation in RF Domain for Simultaneous Transmit and Receive

With the growth of wireless data traffic, additional spectrum is required to meet consumer demands. Consequently, innovative approaches are needed for efficient management of the available limited spectrum. To double the achievable spectral efficiency, a transceiver can be designed to receive and transmit signals simultaneously (STAR) across the same frequency band. However, due to the coupling of the high power transmitted signal into the collocated receiver, the receiver\u27s performance is degraded. For successful STAR realization, the coupled high-power transmit (Tx) signal should be suppressed by 100-120 dB over the entire operational bandwidth. So far, most STAR implementations are narrowband, and not useful for ultra wideband (UWB) communications. In this paper, we present a review of novel approaches employed to achieve improved cancellation across wide bandwidths in RF and propagation domains. Both single and multi-antenna systems are considered. Measurements show an average cancellation of 50 dB using two stages of RF signal cancellation