Investigation on the Effect of Stirring Process Parameters on the Dispersion of SiC Particles Inside Melting Crucible

Vishal R. Mehta,Mayur P. Sutaria 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

Stirring based liquid metal processing is the widely explored process by researchers for the production of metal matrixcomposites (MMCs). The dispersion of reinforcement particles is the major challenge in the process. The stirring processparameters govern the dispersion of reinforcement particles in MMCs. The important stirring process parameters are stirringspeed, stirrer geometry, stirrer position, and stirring time. In the literature, research works are reported, where the effect ofsuch parameters on the dispersion of particles was investigated either by analyzing flow field using computational methods(assuming constant fluid properties) or by sectioning the casted samples. In cast condition, the dispersion of particles is alsoinfluenced by the solidification phenomena. The aim of the present work is to investigate the significance and the effect ofstirrer geometry, stirrer position and stirring speed on the dispersion of reinforcement particles inside melting crucible, duringthe stirring. Aluminium alloy LM25 was used as the matrix material and silicon carbide (SiC) particles having mean size37.58 microns (d50 value) were used as the reinforcement phases. Samples of the composite slurry during the stirring processwere dragged using a quartz tube at three levels inside crucible and microstructure analysis was carried out. Number density(ND) and inter particle distance were evaluated for parameter combinations. The uniform dispersion of SiC particles wasobserved at 45° stirrer blade angle, 400 rpm stirring speed and 40 mm stirrer position. And, significance order of individualparameter was observed as stirring speed < stirrer position < stirrer blade angle.

Single Shot White Light Interference Microscopy for 3D Surface Profilometry Using Single Chip Color Camera

Vishal Srivastava,Mohammad Inam,Ranjeet Kumar,Dalip Singh Mehta 한국광학회 2016 Current Optics and Photonics Vol.20 No.6

We present a single shot low coherence white light Hilbert phase microscopy (WL-HPM) for quantitativephase imaging of Si opto-electronic devices, i.e., Si integrated circuits (Si-ICs) and Si solar cells. Whitelight interferograms were recorded by a color CCD camera and the interferogram is decomposed into thethree colors red, green and blue. Spatial carrier frequency of the WL interferogram was increasedsufficiently by means of introducing a tilt in the interferometer. Hilbert transform fringe analysis was usedto reconstruct the phase map for red, green and blue colors from the single interferogram. 3D step heightmap of Si-ICs and Si solar cells was reconstructed at multiple wavelengths from a single interferogram. Experimental results were compared with Atomic Force Microscopy and they were found to be close toeach other. The present technique is non-contact, full-field and fast for the determination of surfaceroughness variation and morphological features of the objects at multiple wavelengths.

Minimally Invasive Microscope-Assisted Stand-Alone Transarticular Screw Fixation without Gallie Supplementation in the Management of Mobile Atlantoaxial Instability

Tarun Dusad,Vishal Kundnani,Shumayou Dutta,Ankit Patel,Gaurav Mehta,Mahendra Singh 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.4

Study Design: Retrospective study. Purpose: To evaluate the clinico-radiological efficacy of stand-alone minimally invasive transarticular screw (MIS-TAS) fixation without supplemental Gallie fixation in the management of mobile C1–C2 instability. Overview of Literature: Data evaluating the efficacy and feasibility of MIS-TAS in the literature is scanty. Methods: Patients with mobile atlantoaxial instability and >2 years follow-up were included and managed by stand-alone TAS fixation using the Magerl technique and morselized allograft without additional fixation. Patient demographics and intra-operative parameters were noted. Clinical parameters (Visual Analog Scale [VAS] and Oswestry Disability Index [ODI]), neurology (modified Japanese Orthopaedic Association [mJOA]), and radiological factors (anterior atlanto-dens interval and space available for cord) were evaluated pre and postoperatively. Computed tomography (CT) was performed in patients who did not show interspinous fusion on X-ray at 1 year, to verify intra-articular fusion. Statistical analysis was performed using IBM SPSS ver. 20.0 (IBM Corp., Armonk, NY, USA); the Student t-test and analysis of variance were used to assess statistical significance (p<0.05). Results: A total of 82 consecutive cases (three males, one female; mean age, 36.26±5.78 years) were evaluated. In total, 163 TASs were placed. Significant improvement was noticed in clinical (mean preoperative VAS=7.2±2.19, postoperative VAS=3.3±1.12; mean preoperative ODI=78.3±4.83, postoperative ODI=34.05±3.26) and neurological features (mean preoperative mJOA=14.73±2.68, postoperative mJOA=17.5±2.21). Radiological evidence of fusion was noted in 97.5% cases at final follow-up. Seventeen patients were found to have no interspinous fusions upon X-rays, but CT revealed facet fusion in all patients except in two. Inadvertent vertebral artery injury was noted in three cases. Conclusions: Stand-alone TAS fixation with morselized allograft provides excellent radiological and clinical outcomes. The addition of a supplementary tension band and structural graft are not essential. This provides the opportunity to avoid the complications associated with graft harvesting and wiring.

Comparative Analysis between Multi-grid MEMS Structure and Inter-digital Electrodes for Moisture Measurement

Prakriti Kapoor,Vishal Mehta,Rahul Bansal,Satinder Rana,Jatinderpal Singh,Ajit Singh 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.7

This paper describe design of novel sensor for moisture measurement that can be used in agriculture, automotive industries. In the present scenario moisture is measured by calculating change in relative permittivity which in turn depends upon change in capacitance of polymer layer sandwiched between electrodes. In this paper a new design is presented in which IDC sensor is used instead of Grid electrodes to calculate change in capacitance. Further, Comparative analysis has been done between these two topologies; device modeling has been carried out using COMSOL Multi-physics suite with MEMS approach.

Role of Arbitrary Intensity Profile Laser Beam in Trapping of RBC for Phase-imaging

Ranjeet Kumar,Vishal Srivastava,Dalip Singh Mehta,Chandra Shakher 한국광학회 2016 Current Optics and Photonics Vol.20 No.1

Red blood cells (RBCs) are customarily adhered to a bio-functionalised substrate to make them stationaryin interferometric phase-imaging modalities. This can make them susceptible to receive alterations in innatemorphology due to their own weight. Optical tweezers (OTs) often driven by Gaussian profile of a laserbeam is an alternative modality to overcome contact-induced perturbation but at the same time a steeplyfocused laser beam might cause photo-damage. In order to address both the photo-damage and substrateadherence induced perturbations, we were motivated to stabilize the RBC in OTs by utilizing a laser beamof ‘arbitrary intensity profile’ generated by a source having cavity imperfections per se. Thus the immobilizedRBC was investigated for phase-imaging with sinusoidal interferograms generated by a compact and robustMichelson interferometer which was designed from a cubic beam splitter having one surface coated withreflective material and another adjacent coplanar surface aligned against a mirror. Reflected interferogramsfrom bilayers membrane of a trapped RBC were recorded and analyzed. Our phase-imaging set-up is limitedto work in reflection configuration only because of the availability of an upright microscope. Due to RBC’smembrane being poorly reflective for visible wavelengths, quantitative information in the signal is weakand therefore, the quality of experimental results is limited in comparison to results obtained in transmissionmode by various holographic techniques reported elsewhere.

Spine Surgery, Ganga Hospital, Coimbatore, India

Tarun Dusad,Vishal Kundnani,Shumayou Dutta,Ankit Patel,Gaurav Mehta,Mahendra Singh 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.2

Study Design: Prospective cohort study. Purpose: To compare intraoperative parameters, radiation exposure, and pedicle screw perforation rate in navigation-guided versus non-navigated fluoroscopy-assisted minimal invasive transforaminal lumbar interbody fusion (MIS TLIF). Overview of Literature: The poor reliability of fluoroscopy-guided instrumentation and growing concerns about radiation exposure have led to the development of navigation-guided instrumentation techniques in MIS TLIF. The literature evaluating the efficacy of navigation-guided MIS TLIF is scant. Methods: Eighty-seven patients underwent navigation- or fluoroscopy-guided MIS TLIF for symptomatic lumbar/lumbosacral spondylolisthesis. Demographics, intraoperative parameters (surgical time, blood loss), and radiation exposure (sec/mGy/Gy.cm2 noted from C-arm for comparison only) were recorded. Computed tomography was performed in patients in the navigation and non-navigation groups at postoperative 12 months and reviewed by an independent observer to assess the accuracy of screw placement, perforation incidence, location, grade (Mirza), and critical versus non-critical neurological implications. Results: Twenty-seven patients (male/female, 11/16; L4–L5/L5–S1, 9/18) were operated with navigation-guided MIS TLIF, whereas 60 (male/female, 25/35; L4–L5/L5–S1, 26/34) with conventional fluoroscopy-guided MIS TILF. The use of navigation resulted in reduced fluoroscopy usage (dose area product, 0.47 Gy.cm2 versus 2.93 Gy.cm2), radiation exposure (1.68 mGy versus 10.97 mGy), and fluoroscopy time (46.5 seconds versus 119.08 seconds), with p -values of <0.001. Furthermore, 96.29% (104/108) of pedicle screws in the navigation group were accurately placed (grade 0) (4 breaches, all grade I) compared with 91.67% (220/240) in the non-navigation group (20 breaches, 16 grade I+4 grade II; p =0.114). None of the breaches resulted in a corresponding neurological deficit or required revision. Conclusions: Navigation guidance in MIS TLIF reduced radiation exposure, but the perforation status was not statistically different than that for the fluoroscopy-based technique. Thus, navigation in nondeformity cases is useful for significantly reducing the radiation exposure, but its ability to reduce pedicle screw perforation in nondeformity cases remains to be proven.