Towards achieving nanofinish on silicon (Si) wafer by μ-wire electro-discharge machining

This study investigates the use of nanopowder-mixed dielectric oil and temporary metallic coating on highly doped Si sample to achieve nanometric surface roughness using μ-WEDM operation. To achieve this, two different nanopowders were used in dielectric medium with two different temporary metallic coating in the workpiece. This is with Al and C with metallic coating of (gold) thickness 160 nm and 320 nm. Further, the discharge energy level was varied into two proximate stages (80 V/13 pF and 85 V/0.1 nF). The results show that nanopowder-assisted μ-WEDM process has improved the material removal rate (MRR) by ~ 44.5% (maximum). However, the spark gap (SG) has also been increased to a maximum of 60% than without nanopowder assisted the μ-WEDM process. Further, it was found in our study that graphite (C) nanopowder usually generates lower spark gap as compared to aluminum (Al) nanopowder. It has also been observed that at specific μ-WEDM condition, coating thickness, and powder concentration C, Al can easily produce nanometric average surface roughness (ASR) (for C lowest ASR was 76 nm and for Al lowest ASR was 83 nm). From the findings, it can be understood that ASR can be improved maximum ~ 65% for C nanopowder and ~ 51% for Al nanopowder-assisted μ-wire electro-discharge machining as compared to conventional μ-WEDM of Si wafer. Machining stability and evenness of the machined slots were also improved by a significant margin when nanopowder-assisted μ-wire electro-discharge machining method was applied

Breast cancer management pathways during the COVID-19 pandemic: outcomes from the UK ‘Alert Level 4’ phase of the B-MaP-C study

Abstract: Background: The B-MaP-C study aimed to determine alterations to breast cancer (BC) management during the peak transmission period of the UK COVID-19 pandemic and the potential impact of these treatment decisions. Methods: This was a national cohort study of patients with early BC undergoing multidisciplinary team (MDT)-guided treatment recommendations during the pandemic, designated ‘standard’ or ‘COVID-altered’, in the preoperative, operative and post-operative setting. Findings: Of 3776 patients (from 64 UK units) in the study, 2246 (59%) had ‘COVID-altered’ management. ‘Bridging’ endocrine therapy was used (n = 951) where theatre capacity was reduced. There was increasing access to COVID-19 low-risk theatres during the study period (59%). In line with national guidance, immediate breast reconstruction was avoided (n = 299). Where adjuvant chemotherapy was omitted (n = 81), the median benefit was only 3% (IQR 2–9%) using ‘NHS Predict’. There was the rapid adoption of new evidence-based hypofractionated radiotherapy (n = 781, from 46 units). Only 14 patients (1%) tested positive for SARS-CoV-2 during their treatment journey. Conclusions: The majority of ‘COVID-altered’ management decisions were largely in line with pre-COVID evidence-based guidelines, implying that breast cancer survival outcomes are unlikely to be negatively impacted by the pandemic. However, in this study, the potential impact of delays to BC presentation or diagnosis remains unknown

Autonomous Inspection of a Containment Vessel using a Micro Aerial Vehicle

In this work, we address the design, estimation, planning, control, and mapping problems to allow a small scale quadrotor to autonomously inspect the interior of a Containment Vessel (CV) test fixture, using on-board lighting, computation and sensing. We demonstrate a fully autonomous, 160 cm tip-to-tip, 236 gram Micro Aerial Vehicle (MAV) performing a complex flight mission inside of a dark test fixture that was built from a scale model of a CV. The proposed solution opens up new ways to inspect nuclear power plants and has the potential to support nuclear decommissioning, which is well known to be a dangerous, long, and tedious process. Experimental results show the ability to navigate under dripping water conditions and inside a completely dark, full-scale CV test fixture while concurrently avoiding known and unknown obstacles

Content-based image retrieval from whole slide histolgy scans

This paper presents results that were obtained during solving problem of searching stained regions of tissue. The object of research is whole slide histology scans of tissue sections, that were damaged by cancer. The main idea is transformation of colored image to a gray-scale one, then splitting it to tiles for which different descriptors (intensity histogram, co-occurence matrix) are calculated. The similarity map is obtained by applying comparing of precalculated descriptors of tiles with descriptor of tile that represents damaged region of tissue using metrics (L1, L2, Chi-metric) and visualization using existing color maps. The conclusion was that this methodology can be effectively used to perform query searching fast even on non-specialized computers

Design and fabrication of compact fluorescent lamp igniter using TRIAC-assisted high-voltage DC source

A potential approach for designing and fabricating igniter for compact fluorescent lamp is introduced using high-voltage DC (HVDC) source which is controlled by gate pulse obtained from TRIAC-based firing circuit. The Cockroft-Walton voltage multiplier circuit is used to design HVDC (2 kV) sourc e where i ni ti al ly opti ma l rati ng of c apac it anc e f or each stage was considered based on experimental analysis. This design was further simulated by Multisim 11 and characterised experimentally. The response obtained by this method reveals that the HVDC source is able to ignite the fluorescence lamp potentially than the conventional available ignition processes. The major advantages of using HVDC are lower power to ignite fluore sc enc e l amp, longer li fe and cost ef fe ct ive

An improved machining process of polished silicon using nano powder mixed micro-wire electro discharge machining

Micro Wire Electro Discharge Machining (μ-WEDM) is a non-conventional promising machining process which is used mainly to machine complex shaped parts for research and industrial applications. However, for machining semiconductor material with high resistivity like silicon (Si) requires some special techniques to produce better machining stability during the μ-WEDM operation process. One of such ways is to coat Si temporarily with a conductive coating (such as gold or copper) that enhances the discharge current flow through Si workpiece. In this study, temporarily gold coated silicon wafer has been machined by μ-WEDM where workpieces were submerged into the nano powder mixed dielectric medium. This causes the dielectric strength of the medium to be lowered and machining can be carried out more smoothly. The main aim of this work is to identify the effects of nano powder assisted μ-WEDM operation on gold coated silicon wafer. The machining efficiency of the gold (Au) coated Si wafer were determined by the average surface roughness (ASR), material removal rate (MRR) and spark gap (SG). Based on the experimental observation, it has been found that for most of the experiments, the MRR of Si were higher for nanopowder assisted WEDM operation (almost 39% improved). The SG was however, increased (from 2% to159% range) when nanopowder was used in the dielectric medium. Finally, the ASR of the WEDMed surface were observed to be significantly lower (from 4% to 121% maximum) for the nano powder mixed dielectric medium than pure dielectric medium