Risks and benefits of two different entry techniques for laparoscopic gynecological surgeries

Background: Primary abdominal access still remains a challenge for laparoscopic surgery despite rapid advances. This study was conducted to prospectively analyse and compare risks and benefits of two different entry techniques namely, veress needle and direct trocar in laparoscopic gynaecological surgeries so as to obtain consensus on the optimal method to be followed to create pneumoperitoneum.Methods: This was a prospective randomized study conducted at Deen Dayal Upadhyay hospital, under Delhi government. During the period January 2014 to June 2016, 800 patients (20-65 years) operated laparoscopically by the same team of surgeons for various gynaecological conditions, were randomized in two groups: Veress needle group (VN) and Direct trocar group (DT). Each group comprised of 400 patients. Comparison of various parameters was done between the two groups.Results: Incidence of major complications in terms of visceral injuries was 0.75% (3/400) in DT group and nil in VN group. Open conversion rate (2/400 i. e. 0.5%) and number of attempts required to create pneumoperitoneum were also more in DT group. Failed access in previous surgery cases was 1.2% (1/38) in VN and 14.8% (4/27) in DT group. Incidence of port site bleeding (n=3) was also more in DT group. Although the incidence of minor complications such as extraperitoneal insufflations (n=5) and no. of failed access (n=6) were more in VN group, there was no incidence of any life-threatening complication.Conclusions: In our experience, there is clear evidence of advantage of using veress needle in preventing major complications. Veress needle is therefore safer, convenient and effective technique of creating pneumoperitoneum

An Efficient Deep Convolutional Neural Network Model For Yoga Pose Recognition Using Single Images

Pose recognition deals with designing algorithms to locate human body joints in a 2D/3D space and run inference on the estimated joint locations for predicting the poses. Yoga poses consist of some very complex postures. It imposes various challenges on the computer vision algorithms like occlusion, inter-class similarity, intra-class variability, viewpoint complexity, etc. This paper presents YPose, an efficient deep convolutional neural network (CNN) model to recognize yoga asanas from RGB images. The proposed model consists of four steps as follows: (a) first, the region of interest (ROI) is segmented using segmentation based approaches to extract the ROI from the original images; (b) second, these refined images are passed to a CNN architecture based on the backbone of EfficientNets for feature extraction; (c) third, dense refinement blocks, adapted from the architecture of densely connected networks are added to learn more diversified features; and (d) fourth, global average pooling and fully connected layers are applied for the classification of the multi-level hierarchy of the yoga poses. The proposed model has been tested on the Yoga-82 dataset. It is a publicly available benchmark dataset for yoga pose recognition. Experimental results show that the proposed model achieves the state-of-the-art on this dataset. The proposed model obtained an accuracy of 93.28%, which is an improvement over the earlier state-of-the-art (79.35%) with a margin of approximately 13.9%. The code will be made publicly available

Atom probe analysis of the gettering phenomena in passivating films for silicon photovoltaics.

Crystalline silicon photovoltaics (c-Si PVs) play a major role in today’s renewable energy market. An ever-increasing solar energy demand combined with cost constraints has created a drive for lower purity Si. Impurities in Si, cause a decrease in energy conversion efficiency, so their removal via gettering is crucial. In this study, the gettering phenomena in three passivating films, namely, intrinsic and heavily doped (boron: B, or phosphorus: P) polycrystalline silicon with silicon oxide interlayer (poly-Si/SiOx), silicon nitride (SiNx) and aluminium oxide (Al2O3) is studied. In the case of poly-Si/SiOx, the role of dopants in gettering mechanics is investigated. In SiNx, the question of density/stoichiometric changes affecting gettering is explored. In Al2O3, the effect of microstructural variations at the Al2O3/c-Si interface is examined. The study used atom probe tomography and transmission electron microscopy for analysis. The poly-Si/SiOx system revealed the first experimental validation for the existence of (metal) M-P4V (vacancy) clusters as predicted by ab-initio simulation studies. Gettering via O in P-doped contacts as proposed by simulations was also validated. For the P-doped films, O and P were determined to be the predominant getterers, and B-O clusters for the B-doped films. A new microstructural depleted of solutes was also observed. In the SiNx system, density variations in (Si+N) coincided with gettered Fe. A link between gettering mechanism and stoichiometric/density variations of SiNx film was established. Dense O regions were observed at the interface, which have been predicted by kinetics simulation studies to retard Fe diffusion. In the Al2O3 system revealed a discrete chemical transition at the Al2O3/c-Si interface. The experimental results point to the interface being the main gettering sink. The Fe distribution is linked to the diffusion dynamics arising from differences in density between adjacent regions in the film

EXPERIMENTALINVESTIGATIONOFDIRECTPLASMAPECVDCOATINGONTHEABSORPTIVITYOFMONO-CRYSTALLINE&SOLARGRADECRYSTALLINESILICONWAFERS

Advancementsoftechnologiesintoday’sworldcreatesaneedforresourcesalternativeenergy. Researchersareworkingcontinuouslytotapvarioussourcesofrenewableenergybut stillupgradingtheefficiencyoftheseresourcesisstillachallenge. Byvaryingthecolorsofcoating,theeffectofabsorptivityofsiliconwaferswasstudied. Siliconsolarcells’efficiencyisconsiderablyaffectedbytheabsorptionoflightandchargecollectionarea. Increaseinabsorptionincreasesphotocurrentandefficiency. Tocreatevariouscolors,siliconwaferwerecoatedwithdifferentcompositionofsiliconnitride. CoatingsweredonebyPlasmaEnhancedChemicalVapourDeposition(PECVD) stageontheequipmentmanufacturedbySchmidGmbh,Germany

Minimization of Switched Capacitor Voltage Ripple in a Multilevel Dodecagonal Voltage Space Vector Structure for Drives

A multilevel dodecagonal voltage space vector generation scheme for variable-speed drive applications with single-dc-link operation requires a large value of capacitance for cascaded H-bridge (CHB) filters, when operated at lower speeds. In existing schemes, the multilevel dodecagonal structure is obtained by cascading a flying capacitor inverter with a CHB. In this paper, a new scheme has been proposed to minimize the capacitance requirement for full speed operation by creating vector redundancies using modular and equal voltage CHBs. Also, an algorithm has been developed to optimize the selection of vector redundancies among the CHBs in order to minimize the voltage ripple of the floating capacitors. The proposed algorithm considers instantaneous capacitor voltages and phase currents for optimal selection of vector redundancies. A mathematical model for capacitor voltage deviation is presented, and the effectiveness of the proposed algorithm is verified in both the simulation and the experiment

Multilevel Dodecagonal Space Vector Generation Using Stacked Inverter Cells for IM drives

This paper proposes a new induction motor drive scheme to generate a dense multilevel dodecagonal space vector structure, by stacking two 3-level flying capacitors and cascading two H-bridges. The proposed scheme combines the benefits of both multilevel as well as dodecagonal voltage space vector structure. All the capacitors in the stacked inverters are balanced using switching state redundancies within a sampling period. The H-bridges act as a harmonics filter and provide only reactive power, irrespective of load power factor and the capacitors are naturally balanced. The stacked inverter operates in quasi square wave mode throughout the modulation range and results in less switching losses. Both the simulation and experimental results are included in the paper to support the effectiveness of the proposed scheme

A Hybrid 7-Level Inverter Using Low-Voltage Devices and Operation With Single DC-Link

This paper proposes a new 7-level inverter topology for induction motor drives. It is a hybrid topology formed by cascading a 5-level active neutral-point-clamped inverter with a 3-level T-type converter. It is obtained using low-voltage semiconductor devices with voltage blocking capability of Vdc/3 and Vdc/6. The topology uses three floating capacitors per phase, which are balanced within a pulsewidth modulation (PWM) switching duration using switching-state redundancies for each pole-voltage level. Topology forms two stacks at the front-end, which requires individual symmetrical de source. The analysis of switching loss and conduction loss is performed and compared with some of the existing 7-level multi-level inverters reported in various literatures to show the advantages of the proposed topology. Furthermore, the single dc source operation with two stacked capacitors and closed-loop control of neutral-point voltage using symmetrical six-phase induction motor is proposed. The voltage-control algorithms fin. floating capacitors and dc-link stacked capacitors are proposed, which are independent of load power factor and modulation index. Open-loop V/f and closed-loop rotor field oriented control are performed, and various results at steady and transient states are presented to validate the aforementioned claims

Instantaneous Balancing of Neutral-Point Voltages for Stacked DC-Link Capacitors of a Multilevel Inverter for Dual-Inverter-Fed Induction Motor Drives

This paper proposes a novel method for instantaneous balancing of neutral-point (NP) voltages with stacked multilevel inverters (MLIs) for variable-speed drives. The stacked MLI uses series-connected dc sources and NPs (connecting points of dc sources) to obtain the desired levels. The balancing of NP voltages are obtained by using a low-voltage-capacitor-fed cascaded H-bridge (CHB) per phase of a symmetrical six-phase induction machine (IM), which ensures zero current drawn from NPs (at any given instant). Since no current is drawn from NPs, the single dc-link operation with stacked capacitors is also possible. The scheme is suitable for applications, where low-voltage dc sources and batteries are stacked to form a dc link. A variable-speed operation is done using a seven-level inverter scheme for a symmetrical six-phase IM, which is formed by three dc-link stacked capacitors cascaded with two low-voltage-capacitor-fed CHBs per phase. Furthermore, the method is extended for an open-end IM to obtain a seven-level common-mode eliminated space vector structure using a single dc link. The generalization of this method for any stacked n-level inverter without NP voltage deviation is also presented in this paper. The experimental results and analysis are included to validate the proposed method