Numerical investigation of heat transfer and friction factor in ribbed triangular duct solar air heater using Computational fluid dynamics (CFD)

Rajneesh Kumar,Varun Goel,Anoop Kumar,Sourabh Khurana,Paramvir Singh,Santosh B. Bopche 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

The Computational fluid dynamics (CFD) based analysis is carried out to investigate the thermal and hydraulic performance of circular rib roughened triangular passage Solar air heater (SAH). The circular ribs were provided over the absorber plate. The roughness parameter such as relative roughness pitch (P/e) and relative roughness height (e/D) varies from 4 to 20 and 0.015 to 0.06 (in four sets), respectively, the Reynolds number (Re) varies from 4000 to 18000. The flow governing equations were solved using commercial ANSYS (Fluent) software. The predicted Nusselt number (Nu) and friction factor (f) are validated with the available experimental results. The thermal and hydraulic performance of roughened duct is estimated in the form of Nusselt number and friction factor, respectively. The Thermohydraulic performance parameter (TPP) is also evaluated depending on the friction factor (f) and Nusselt number (Nu) values for SAH. The maximum Thermohydraulic performance parameter (TPP) is observed at Reynolds number of 15000 in case of relative roughness pitch (P/e) and relative roughness height (e/D) value of 12 and 0.06, respectively.

Mirizzi’s syndrome

Ashok Kumar,Ganesan Senthil,Anand Prakash,Anu Behari,Rajneesh Kumar Singh,Vinay Kumar Kapoor,Rajan Saxena 한국간담췌외과학회 2016 한국간담췌외과학회지 Vol.20 No.1

Backgrounds/Aims: Mirizzi’s syndrome (MS) poses great diagnostic and management challenge to the treating physician. We presented our experience of MS cases with respect to clinical presentation, diagnostic difficulties, surgical procedures and outcome. Methods: Prospectively maintained data of all surgically treated MS patients were analyzed. Results: A total of 169 MS patients were surgically managed between 1989 and 2011. Presenting symptoms were jaundice (84%), pain (75%) and cholangitis (56%). Median symptom duration s was 8 months (range, <1 to 240 months). Preoperative diagnosis was possible only in 32% (54/169) of patients based on imaging study. Csendes Type II was the most common diagnosis (57%). Fistulization to the surrounding organs (bilio-enteric fistulization) were found in 14% of patients (24/169) during surgery. Gall bladder histopathology revealed xanthogranulomatous cholecystitis in 33% of patients (55/169). No significant difference in perioperative morbidity was found between choledochoplasty (use of gallbladder patch) (15/89, 17%) and bilio-enteric anastomosis (4/28, 14%) (p=0.748). Bile leak was more common with choledochoplasty (5/89, 5.6%) than bilio-enteric anastomosis (1/28, 3.5%), without statistical significance (p=0.669). Conclusions: Preoperative diagnosis of MS was possible in only one-third of patients in our series. Significant number of patients had associated fistulae to the surrounding organs, making the surgical procedure more complicated. Awareness of this entity is important for intraoperative diagnosis and consequently, for optimal surgical strategy and good outcome.

Management of residual gall bladder

Ashish Singh,Abhimanyu Kapoor,Rajneesh Kumar Singh,Anand Prakash,Anu Behari,Ashok Kumar,Vinay Kumar Kapoor,Rajan Saxena 한국간담췌외과학회 2018 Annals of hepato-biliary-pancreatic surgery Vol.22 No.1

Backgrounds/Aims: A residual gallbladder (RGB) following a partial/subtotal cholecystectomy may cause symptoms that require its removal. We present our large study regarding the problem of a RGB over a 15 year period. Methods: This study involved a retrospective analysis of patients managed for symptomatic RGB from January 2000 to December 2015. Results: A RGB was observed in 93 patients, who had a median age of 45 (25-70) years, and were comprised of 69 (74.2%) females. The most common presentation was recurrence pain (n=64, 68.8%). Associated choledocholithiasis was present in 23 patients (24.7%). An ultrasonography (USG) failed to diagnose RGB calculi in 10 (11%) patients; whereas, magnetic resonance cholangio-pancreatography (MRCP) accurately diagnosed RGB calculi in all the cases except for 2 (4%) and, additionally, detected common bile duct (CBD) stones in 12 patients. Completion cholecystectomy was performed in all patients (open 45 [48.4%]; laparoscopic 48 [51.6%] and 19 [20.4%] patients required a conversion to open). The RGB pathology included stones in 90 (96.8%), Mirizzi’s syndrome in 10 (10.8%) and an internal fistula in 9 (9.7%) patients. Additional procedures included CBD exploration (n=6); Choledocho-duodenostomy (n=4) and Roux-en-Y hepatico-jejunostomy (n=3). The mortality and morbidity were nil and 11% (all wound infection), respectively. Two patients developed incisional hernia during follow up. The mean follow up duration was 23.1 months (3-108) in 65 patients and the outcome was excellent and good in 97% of the patients. Conclusions: Post-cholecystectomy recurrent biliary colic should raise suspicion of RGB. MRCP is a useful investigation for the diagnosis and assessment of any associated problems and provides a roadmap for surgery. Laparoscopic completion cholecystectomy is feasible, but is technically difficult and has a high conversion rate.

Effect of Indium Doping and Annealing on Photoconducting Property of Wurtzite Type CdS

Vineet Kumar Singh,Pratima Chauhan,Sheo Kumar Mishra,Rajneesh K Srivastava 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.3

In this paper we observed the effect of doping and annealing on the dark current and anomalous photoconducting behavior of hexagonal wurtzite CdS, synthesized by solid state reaction method. Undoped CdS sample shows higher anomalous behavior in photoconductivity as well as contains larger dark current of 19 nA. With the doping of Indium in CdS, dark current decreases from 19 nA to 1 nA but the anomalous behavior is not completely removed. While, after annealing at 150°C for four hour, indium doped CdS sample shows good switching property with rise and decay time of 360 ± 10 & 322 ± 6 seconds respectively. The anomalous photoconducting behavior is completely removed from annealed sample. X-ray diffraction patterns confirm the existence of hexagonal wurtzite phase of indium doped and undoped CdS samples while energy dispersion X-ray spectrum exhibits the elemental presence of cadmium, indium & sulfur in the indium doped sample. UV-Visible absorption spectra show the blue shift in absorption edge on indium doping from 475 nm to 425 nm in comparison to undoped sample. Photoluminescence spectra confirm the indium doping and reveal that annealed CdS sample has lesser defects among other samples due to which annealed sample has best switching performance.

Surgery for symptomatic hepatic hemangioma: Resection vs. enucleation, an experience over two decades

Nalini Kanta Ghosh,Rahul R,Ashish Singh,Somanath Malage,Supriya Sharma,Ashok Kumar,Rajneesh Kumar Singh,Anu Behari,Ashok Kumar,Rajan Saxena 한국간담췌외과학회 2023 Annals of hepato-biliary-pancreatic surgery Vol.27 No.3

Backgrounds/Aims: Hemangiomas are the most common benign liver lesions; however, they are usually asymptomatic and seldom require surgery. Enucleation and resection are the most commonly performed surgical procedures for symptomatic lesions. This study aims to compare the outcomes of these two surgical techniques. Methods: A retrospective analysis of symptomatic hepatic hemangiomas (HH) operated upon between 2000 and 2021. Patients were categorized into the enucleation and resection groups. Demographic profile, intraoperative bleeding, and morbidity (Clavien-Dindo Grade) were compared. Independent t-test and chi-square tests were used for continuous and categorical variables respectively. p-value of < 0.05 was considered significant. Results: Sixteen symptomatic HH patients aged 30 to 66 years underwent surgery (enucleation = 8, resection = 8) and majority were females (n = 10 [62.5%]). Fifteen patients presented with abdominal pain, and one patient had an interval increase in the size of the lesion from 9 to 12 cm. The size of hemangiomas varied from 6 to 23 cm. The median blood loss (enucleation: 350 vs. resection: 600 mL), operative time (enucleation: 5.8 vs. resection: 7.5 hours), and postoperative hospital stay (enucleation: 6.5 vs. resection: 11 days) were greater in the resection group (statistically insignificant). In the resection group, morbidity was significantly higher (62.6% vs. 12.5%, p = 0.05), including one mortality. All patients remained asymptomatic during the follow-up. Conclusions: Enucleation was simpler with less morbidity as compared to resection in our series. However, considering the small number of patients, further studies are needed with comparable groups to confirm the superiority of enucleation over resection.

Shear waves propagation in an initially stressed piezoelectric layer imperfectly bonded over a micropolar elastic half space

Rajneesh Kumar,Kulwinder Singh,D.S. Pathania 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.2

The present study investigates the propagation of shear waves in a composite structure comprised of imperfectly bonded piezoelectric layer with a micropolar half space. Piezoelectric layer is considered to be initially stressed. Micropolar theory of elasticity has been employed which is most suitable to explain the size effects on small length scale. The general dispersion equations for the existence of waves in the coupled structure are obtained analytically in the closed form. Some particular cases have been discussed and in one particular case the dispersion relation is in well agreement to the classical-Love wave equation. The effects of various parameters viz. initial stress, interfacial imperfection and micropolarity on the phase velocity are obtained for electrically open and mechanically free system. Numerical computations are carried out and results are depicted graphically to illustrate the utility of the problem. The phase velocity of the shear waves is found to be influenced by initial stress, interface imperfection and the presence of micropolarity in the elastic half space. The theoretical results obtained are useful for the design of high performance surface acoustic devices.

Portal Hypertension and Secondary Biliary Cirrhosis in Post Cholecystectomy Benign Biliary Strictures: Factors Responsible, Surgical Implications and Outcomes

( Saurabh Galodha ),( Rajneesh K Singh ),( Anu Behari ),( Ashok Kumar Gupta ),( V K Kapoor ),( Rajan Saxena ) 대한간학회 2017 춘·추계 학술대회 (KASL) Vol.2017 No.1

Aims: Portal hypertension (PHT) and secondary biliary cirrhosis (SBC) are found in 7-20% patients of postcholecystectomy benign biliary strictures (BBS), which can lead to significant morbidity and mortality. This study was done to look for factors associated with PHT and SBC in BBS and its effect on perioperative morbidity and final outcomes. Methods: A retrospective analysis of 613 patients of BBS managed between January 1989 and December 2012 was done. Preoperative and intraoperative parameters and perioperative morbidity were registered. Outcomes were analyzed with McDonald grading with grades A and B considered as success. Results: A retrospective analysis of 613 patients of BBS managed between January 1989 and December 2012 was done. Preoperative and intraoperative parameters and perioperative morbidity were registered. Outcomes were analyzed with McDonald grading with grades A and B considered as success. Nineteen patients of BBS with PHT were operated. PHT was seen more commonly in BBS grade III and above (n=12,63%). The median time to repair in patients with PHT was more than 4 times that of patients without PHT (826 days vs. 210 days). Two patients with PHT had strictured previous primary repair in the form of Roux-en Y hepaticojejunostomy (RYHJ). In all patients RYHJ with liver biopsy was performed. None of the patients required prior portosystemic shunting. In patients with PHT mean operating time (4.6 ± 2.8 vs. 3.5 ± 2 hours) as well as median blood loss (400 ml vs. 200 ml) was increased but there was no significant increase in perioperative morbidity. Median follow up for these patients was 54 months. Success rate for RYHJ was 89% and only 1 patient required a revision RYHJ due to stricture and recurrent cholangitis. Conclusions: Delayed repair, higher grade of BBS and failed primary repair are factors associated with development of PHT in BBS. RYHJ is feasible without need of portosystemic shunting in all these patients with minimal morbidity and good long-term results.

Effect of NTT on Performance of AODV in a Grid Topology-Based Wireless Ad Hoc Network

Saurabh Sharma,Alok Singh,Rajneesh Kumar Srivastava 한국정보과학회 2022 Journal of Computing Science and Engineering Vol.16 No.3

Routing in wireless ad hoc networks that enable nodes, acting as routers also, to find the best path between source and destination nodes, taking into account cost, is a very challenging task. In the present work, an investigation of performance of AODV routing protocol in a grid topology based ad hoc network by varying the value of node traversal time (NTT) and taking into account absence and presence of Hello messages is reported. A set of metrics, including Average End-to-End Delay, Packet Delivery Ratio, Throughput, Routing Overhead, Route Error Overhead, Normalized Routing Load, Average Hop Count, and Total Number of Received Data Packets, has been used to assess the performance of AODV in the grid network. Performance of AODV routing protocol varies in the value of NTT. Throughput in grid topology, by and large, is observed to decrease with an increase in NTT. However, explicit relations between certain metrics with NTT as well as simulation time could not be traced due to intricacies involved in the combination of states of various links and flows in the grid topology. To have better insights, grid topologies of two, three, and four rows are planned to be investigated in the future.

Determinants of curative resection in incidental gallbladder carcinoma with special reference to timing of referral

Rahul,Kulbhushan Haldeniya,Ashish Singh,Neha Bhatt,Prabhakar Mishra,Rajneesh Kumar Singh,Rajan Saxena 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.4

Backgrounds/Aims: Re-resection of incidental gallbladder carcinoma (IGBC) is possible in a select group of patients. However, the optimal timing for re-intervention lacks consensus. Methods: A retrospective analysis was performed for a prospective database of 91 patients with IGBC managed from 2009 to 2018. Patients were divided into three groups based on the duration between the index cholecystectomy and re-operation or final staging: Early (E), < 4 weeks; Intermediate (I), > 4 weeks and < 12 weeks; and Late (L), > 12 weeks. Demographic data, tumor characteristics, and operative details of patients were analyzed to determine factors affecting the re-resectability of IGBC. Results: Twenty-two patients in ‘E’, 48 in ‘I’, and 21 in ‘L’ groups were evenly matched. Nearly two thirds were asymptomatic. Curative resection was possible in 48 (52.7%) patients. Metastasis was detected during staging laparoscopy (SL)/laparotomy in 26 (28.6%) patients. The yield of SL was more in the ‘L’ group (30.8%) than in the ‘I’ (11.1%) or ‘E’ (nil) group, avoiding unnecessary laparotomy in 13.6%. Only 28.5% of patients in the ‘L’ group could undergo curative resection (R0/R1 resection), significantly less than that in the ‘E’ (50.0%) or ‘I’ group (64.6%) (both p < 0.001). On multivariate analysis, presentation in intermediate period and tumor differentiation increased the chance of curative resection (p < 0.05). Conclusions: Asymptomatic patients in the ‘I’ group with well differentiated IGBC have the best chance of obtaining a curative resection.

Does timing of completion radical cholecystectomy determine the survival outcome in incidental carcinoma gallbladder: A single center retrospective analysis

Rahul,Kulbhushan HALDENIYA,Ashish SINGH,Prabhakar MISHRA,Rajneesh Kumar SINGH,Anu BEHARI,Vinay Kumar KAPOOR,Rajan SAXENA 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.-