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Vignesh Lakshmanan,PUSHPAK DOIPHODE,Indraneel Samanta 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.1
Invertier air conditioners are being widely used in the air conditioning sector for energy saving pirposes. These air conditioners use an inverter of a variable frequency dirive(VFD) to control the compressor operating speed based on cooling or heating load fluctuations. If the heat generated by the electronic components of the VFD is not dissipated properly, it can lead to failure of the VFD. In general, a heat sink is used for dissipating the heat gererated by the electronic components of the VFD. The heat sink can be either air cooled of liquid cooled. Using computational fluid dynamics(CFD), the present paper deals with optimization of the thermal performance of an air cooled plate fin heat sink with rectangular fins used in a residential split inverter air conditioner. Commercially availavle CFD tool has been used for simulations. It has been observed that enhancing fluid flow around heat sink and inproving heat transfer area of the fins significantly improce the thermal performance of the heat sink. By using heat sink with rectagular fins having a stepped profile, it has been possible to improve the heat transfer from the baseline case by 27%. Whereas, by using hollow fins, heat transfer improvement of 20% has been achieved.
Control of Shock Train in the Isolator of Hypersonic Engine
Vignesh Ram PS,Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.11
The Isolator plays a critical role in scramjet engine situated between the inlet and the combustion chamber. The supersonic flow decelerated to subsonic speed achieved by compression waves. The flow filed is more complex with shock–shock interaction and shock boundary layer interaction. The series of shock wave occurs inside the isolator is called as shock train. In the present work the characteristic of shock train flow field in a constant area isolator and its control using suction is studied numerically. The results shows that the suction of boundary layer can influence the shock train length and with the optimum pressure ratio the shock train can become a single normal shock. The total pressure loss also improved by boundary layer suction.
Vignesh Vudatha,Yahya Alwatari,George Ibrahim,Tayler Jacobs,Kyle Alexander,Carlos Puig-Gilbert,Walker Julliard,Rachit Dilip Shah 대한심장혈관흉부외과학회 2023 Journal of Chest Surgery (J Chest Surg) Vol.56 No.5
Background: A significant proportion of cardiac surgery intensive care unit (CSICU) patients require long-term ventilation, necessitating tracheostomy placement. The goal of this study was to evaluate the long-term postoperative outcomes and complications associated with percutaneous dilatational tracheostomy (PDT) in CSICU patients. Methods: All patients undergoing PDT after cardiac, thoracic, or vascular operations in the CSICU between January 1, 2013 and January 1, 2021 were identified. They were evaluated for mortality, decannulation time, and complications including bleeding, infection, and need for surgical intervention. Multivariable regression models were used to identify predictors of early decannulation and the complication rate. Results: Ninety-three patients were identified for this study (70 [75.3%] male and 23 [24.7%] female). Furthermore, 18.3% of patients had chronic obstructive pulmonary disease (COPD), 21.5% had history of stroke, 7.5% had end-stage renal disease, 33.3% had diabetes, and 59.1% were current smokers. The mean time from PDT to decannulation was 39 days. Roughly one-fifth (20.4%) of patients were on dual antiplatelet therapy and 81.7% had anticoagulation restarted 8 hours post-tracheostomy. Eight complications were noted, including 5 instances of bleeding requiring packing and 1 case of mediastinitis. There were no significant predictors of decannulation prior to discharge. Only COPD was identified as a negative predictor of decannulation at any point in time (hazard ratio, 0.28; 95% confidence interval, 0.08–0.95; p=0.04). Conclusion: Percutaneous tracheostomy is a safe and viable alternative to surgical tracheostomy in cardiac surgery ICU patients. Patients who undergo PDT have a relatively short duration of tracheostomy and do not have major post-procedural complications.
Vignesh Dhandapani,최수련,Parameswari Paul,김용권,Nirala Ramchiary,허윤강,임용표 한국유전학회 2012 Genes & Genomics Vol.34 No.6
Brassica rapa L. (AA, 2n = 20), an A genome diploid species of Brassica genus is of researchers interest recent days since enormous amount of data is available about the genome. Since EST analysis is a powerful tool in gene discovery we compared different existing methods and developed a new pipeline for EST computational analysis to analyze the available data. A total of 1,438 expressed sequence tags sizing from 83 to 2,023 base pairs were generated and subjected to various types of analysis. Cluster analysis of these ESTs identified 969unique sequences called unigenes, with 162 contigs and 807singlets. Similarity search produced 704 significant hits with E-value ≥ 10-5. The functions of the best hits were annotated by gene ontology (GO) analysis. Additionally, we classified 293 and 541 unigenes based on their functions, using Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways and protein structural domain databases, respectively. We also identified and categorized 171 microsatellites into di-, tri-, tetra-,and penta nucleotide repeats, and designed primers. Possible open reading frames (ORFs) were predicted for 960unigenes, by the comparison with a primary protein sequence database. In silico mapping of partial unigenes were done in bacterial artificial chromosome (BAC) sequences, downloaded from the Brassica genome project website. We determined 149single nucleotide polymorphisms (SNPs) and 3 indels from the coding region of 27 unigenes of B. rapa and similar Brassica napus ESTs clusters. All the generated EST sequences were submitted to the GenBank EST database (dbEST) as accessions from CO749247 to CO750425.
Vignesh Prabhu,Sunil K. Gupta,Sandeep Madhwal,Vijay Shridhar 한국산업안전보건공단 산업안전보건연구원 2019 Safety and health at work Vol.10 No.2
Background: Street vendors spend relatively more time near roadways and are vulnerable to air pollution related health disorders. However, there is limited information on the quality of the air they breathe. The objectives of this present study were to calculate the mass concentration of atmospheric particulate matter (PM) in eight size fractions (PM0.4e0.7, PM0.7e1.1, PM1.1e2.1, PM2.1e3.3, PM3.3e4.7, PM4.7e5.8, PM5.8e9.0, and PM9.0-e0mm) at commercial (CML) and residential site (RSL) in Dehradun city from November 2015 to May 2016. To estimate the corresponding respiratory deposition dose (RDDs) in alveolar (AL), tracheobronchial (TB), and head airway (HD) region on street vendors working at CML and RSL. To find the association of atmospheric PM with RDDs and the incidence of respiratory related disorders among street vendors. Methods: Andersen cascade impactor was employed for calculating the PM mass concentration. Questionnaire based health survey among street vendors were carried out through personal interview. Results: A significant difference (p < 0.05; t-test) between the mean PM0.4-10mm mass concentration at CML and RSL was observed with (mean SD) 84.05 14.5 and 77.23 11.7 mgm3, respectively. RDDs in AL, TB and HD region at CML was observed to be 9.9, 7.8, and 7.3% higher than at RSL, respectively. Health survey revealed 1.62, 0.96, 0.04, and 0.57 times higher incidence of cold, cough, breathlessness, and chest pain, respectively with street vendors at CML compared to RSL. Conclusion: The site characteristics plays a major role in the respiratory health status of street vendors at Dehradun.
Blood Transfusions for Emergency Laparotomies in General Surgery
Vignesh Narasimhan,Robert Spychal,Charles Pilgrim 대한외상중환자외과학회 2017 Journal of Acute Care Surgery Vol.7 No.1
Purpose: Decisions regarding perioperative blood transfusions are subject to clinical and laboratory factors. Blood transfusions are associated with increased risk of infection, sepsis, organ failure, and length of stay. Current guidelines on transfusions are based on elective settings. There is a paucity of data on blood transfusion use in emergency surgery. This study reviews the appropriateness of blood transfusions in patients undergoing emergency general surgical laparotomies.Methods: Patients undergoing emergency general surgical laparotomies at Peninsula Health from January 2013 to May 2015 were reviewed. Hemoglobin (Hb) levels triggering transfusion and overall blood utilization were obtained. Transfusions were classified based on whether they were given pre-, intra- or postoperatively. Transfusions with Hb >80 g/L in the absence of bleeding or preoperative anemia were deemed ‘inappropriate’ as per Australian Blood Authority guidelines.Results: Over the 29-month period, 368 patients underwent 398 emergency laparotomies. Blood transfusions were given to 102 patients (27.7%). These patients required 240 transfusion episodes. Patients were given a median of three units of blood. One hundred and sixty-six transfusions (69.2%) were postoperative. Forty-six transfusions (19.2%) were given with Hb >80 g/L in the absence of other indications, and were deemed inappropriate. Inappropriate trans-fusions occurred more frequently on the ward compared to ICU (p<0.05). Almost two thirds of inappropriate transfusions were given for Hb 80∼85 g/L.Conclusion: Nearly one in five patients received an inappropriate transfusion. More judicious use of blood products in emergency patients is required, especially on surgical wards. (J Acute Care Surg 2017;7:15-22)