DEVELOPMENT OF AN ADVANCED HEAT EXCHANGER MODEL FOR STEADY STATE AND FROSTING CONDITIONS

Air-to-refrigerant fin-and-tube heat exchangers are a key component in the heating, air conditioning and refrigeration industry. Considering their dominance, the industry has focused immensely on employing computer modeling in their design and development. Recently, advances in manufacturing capabilities, heat exchanger technology coupled with the move towards new environment-friendly refrigerants provide unprecedented challenges for designers and opportunities for researchers. In addition, the field of Computational Fluid Dynamics (CFD) has assumed a greater role in the design of heat exchangers. This research presents the development of an advanced heat exchanger model and design tool which aims to provide greater accuracy, design flexibility and unparalleled capabilities compared to existing heat exchanger models. The heat exchanger model developed here achieves the following. * Account for tube-to-tube conduction along fins, which is known to degrade the performance of heat exchangers, especially in carbon dioxide gas coolers * Study and develop heat exchangers with arbitrary fin sheets, which meet performance as well as packaging goals with minimal consumption of resources * Allow engineers to integrate CFD results for air flow through a heat exchanger, which the modeling tool employs to develop its air propagation sequence leading to improved accuracy over existing models which assume normal air flow propagation * Function in a quasi-steady state mode for the purpose of simulating frost accumulation and growth on heat exchangers, and completely simulate local heat transfer degradation, as well as blockage of flow passage on air side Additionally, the heat exchanger model was used to investigate gains that are enabled due to the presence of cut fins in carbon dioxide gas coolers and develop design guidelines for engineers. Finally, this dissertation analyzes the implications of minimum entropy generation on heat exchanger performance criteria of heat capacity and pressure drop, as well as evaluates the ability of entropy generation minimization as a design objective. This also serves as the first step toward an expert knowledge-based system for guiding engineers towards better designs, during the process of heat exchanger design

Congestion Control using FEC for Conversational Multimedia Communication

In this paper, we propose a new rate control algorithm for conversational multimedia flows. In our approach, along with Real-time Transport Protocol (RTP) media packets, we propose sending redundant packets to probe for available bandwidth. These redundant packets are Forward Error Correction (FEC) encoded RTP packets. A straightforward interpretation is that if no losses occur, the sender can increase the sending rate to include the FEC bit rate, and in the case of losses due to congestion the redundant packets help in recovering the lost packets. We also show that by varying the FEC bit rate, the sender is able to conservatively or aggressively probe for available bandwidth. We evaluate our FEC-based Rate Adaptation (FBRA) algorithm in a network simulator and in the real-world and compare it to other congestion control algorithms

Surround-View Vision-based 3D Detection for Autonomous Driving: A Survey

Vision-based 3D Detection task is fundamental task for the perception of an autonomous driving system, which has peaked interest amongst many researchers and autonomous driving engineers. However achieving a rather good 3D BEV (Bird's Eye View) performance is not an easy task using 2D sensor input-data with cameras. In this paper we provide a literature survey for the existing Vision Based 3D detection methods, focused on autonomous driving. We have made detailed analysis of over $60$ papers leveraging Vision BEV detections approaches and highlighted different sub-groups for detailed understanding of common trends. Moreover, we have highlighted how the literature and industry trend have moved towards surround-view image based methods and note down thoughts on what special cases this method addresses. In conclusion, we provoke thoughts of 3D Vision techniques for future research based on shortcomings of the current techniques including the direction of collaborative perception

The Bethesda system for reporting of thyroid cytopathology and its category wise management

Background: Fine-needle aspiration cytology (FNAC) of thyroid is a rapid diagnostic test for thyroid nodules. The Bethesda system classifies thyroid FNAC into six categories. Each category is linked to a malignancy risk and has recommended clinical management. The aim of this study was to analyze the thyroid cytology smears by Bethesda system and to assess the frequency of various categories and to correlate it previous published studies. Category wise management is also discussed in detail.Methods: A total of 388 thyroid FNAC samples were examined from January 2017 to June 2018 in the Department of Pathology, in Medanta- The Medicity Gurugram.Results: A total of 388 cases were reported according to Bethesda system of reporting. Categories were as follows: I (14.69%), II (61.85%), III (11.34%), IV (2.57%), V (2.660%), VI (4.91%) nodules.Conclusions: The Bethesda System for reporting thyroid cytopathology proved to be an excellent reporting system and it puts clinician and the cytopathologist on the same page and easier to communicate regarding diagnosis

Fuzzy pre-compensated PI control of active filters

This paper deals with a new and improved control technique for shunt active filters (AF) used for compensating unwanted harmonic currents injected in the mains due to nonlinear varying loads. This work is motivated by the need to find a permanent solution to the rigorous hit and trial method for evaluating system parameters in an indirect control of AF. A fuzzy pre-compensated PI (Proportional-Integral) controller is used to fuzzify the reference DC voltage of AF to the controller input so that the overshoots and undershoots in its DC link voltage are minimized and the settling time is improved. A three-phase diode rectifier with R-L (Resistive-Inductive) load is used as a non-linear load to study the effectiveness of the proposed controller of the AF. Robustness to filter parameter variations, insensitivity to controller parameter variations, and transient response has been taken as performance evaluation parameters. The results are shown through simulations in Matlab using power system block sets to demonstrate the capability of the proposed controller of the AF

A short term evaluation of effect on serum urea, creatinine and potassium levels with use of angiotensin II receptor blockers (olmesartan or telmisartan) in stage 1 hypertensive patients

Background: Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers (ARBs) are being used as first line agents for the treatment of hypertension in haemodialysis patients as well as in the general population. Serious hyperkalemia is common in patients with end-stage renal disease, and is observed in about 10% of haemodialysis patients. Although many research have been done so far to compare the antihypertensive efficacy of ARBs, but such studies to evaluate the effect on serum urea, creatinine and potassium levels are not so common in North India region.Methods: In this open label, prospective, randomized study, we evaluated the effect on serum urea, creatinine and potassium levels with use of ARB’s (olmesartan or telmisartan) in stage 1 hypertensive patients (JNCVII). 60 patients were randomized in to two groups. The odd numbers will be allotted olmesartan 20 mg (group A) and even numbers to telmisartan 40 mg (group B). Impacts on serum urea, creatinine and potassium levels were evaluated after 12 weeks.Results: Our results indicates that there was no statistically significant alterations in mean serum creatinine, blood urea and in mean serum potassium levels compared to baseline within the two groups as well as when mean of both groups were compared, olmesartan showed a better reduction in blood pressure as compared to telmisartan.Conclusions: Olmesartan showed a better reduction in blood pressure with similar effects in biochemical parameters as telmisartan

Dorsalis Pedis Artery-based Flap to Cover Nonhealing Wounds Over the Tendo Achillis—A Case Series 用足背動脈蒂皮瓣來覆蓋非癒合的跟腱手術傷口—系列病例報告

AbstractBackground/PurposeSoft tissue necrosis after the repair of a ruptured tendo Achillis is a difficult problem commonly encountered by orthopaedic surgeons. Such wounds are difficult to manage because of the tenuous blood supply and the characteristic anatomical features of the area. Flaps such as the reverse sural flap, medial plantar flap, gastrocnemius flap and free flaps cover such wounds with a good success rate. The aim of our study was to investigate the use of a dorsalis pedis artery (DPA)-based flap to cover a wound over the tendo Achillis insertion area.MethodsWe report a series of 11 patients in whom wounds over the tendo Achillis insertion area were covered with a DPA-based flap. Between 1995 and 2012, 11 patients (nine men and two women), who were referred to us with a nonhealing wound over the tendo Achillis because of soft tissue necrosis after the open repair of a ruptured tendon, were selected for soft tissue coverage of the wound by using a DPA-based flap.ResultsThe average follow-up period was 2.4 years (range, 1–6 years). The mean operative time was 1.7 hours (range, 1.5–2.0 hours). At the latest follow-up examination, the flaps had survived in all patients.ConclusionA DPA-based flap is a good and relatively less complex procedure to use to cover defects over the tendo Achillis with minimum donor site morbidity

Supernumerary Teeth in Indian Children: A Survey of 300 Cases

The aim of this investigation was to study children with supernumerary teeth who visited the Department of Pedodontics and Preventive Dentistry, Government Dental College and Hospital, Rohtak, Haryana, India. Only children with supernumerary teeth were included in the study while patients having supernumerary teeth with associated syndromes were excluded. Supernumeraries were detected by clinical and radiographic examination. The results indicated that males were affected more than females with a sex ratio of 2.9 : 1. Single supernumerary tooth was seen in 79% of the patients, 20% had double, and 1% had three or more supernumeraries. Premaxillary supernumeraries accounted for 93.8% of the cases. Conical shaped supernumerary teeth were the most common type (59.7%). Majority of supernumeraries remained unerupted (65%). Fusion of supernumerary tooth with a regular tooth was observed in 4% of the patients. Talon cusp, an associated dental anomaly, was seen in 5% of the cases. Simultaneous hypodontia occurred in 2.3% of patients with supernumeraries

Low Degree Metabolites Explain Essential Reactions and Enhance Modularity in Biological Networks

Recently there has been a lot of interest in identifying modules at the level of genetic and metabolic networks of organisms, as well as in identifying single genes and reactions that are essential for the organism. A goal of computational and systems biology is to go beyond identification towards an explanation of specific modules and essential genes and reactions in terms of specific structural or evolutionary constraints. In the metabolic networks of E. coli, S. cerevisiae and S. aureus, we identified metabolites with a low degree of connectivity, particularly those that are produced and/or consumed in just a single reaction. Using FBA we also determined reactions essential for growth in these metabolic networks. We find that most reactions identified as essential in these networks turn out to be those involving the production or consumption of low degree metabolites. Applying graph theoretic methods to these metabolic networks, we identified connected clusters of these low degree metabolites. The genes involved in several operons in E. coli are correctly predicted as those of enzymes catalyzing the reactions of these clusters. We independently identified clusters of reactions whose fluxes are perfectly correlated. We find that the composition of the latter `functional clusters' is also largely explained in terms of clusters of low degree metabolites in each of these organisms. Our findings mean that most metabolic reactions that are essential can be tagged by one or more low degree metabolites. Those reactions are essential because they are the only ways of producing or consuming their respective tagged metabolites. Furthermore, reactions whose fluxes are strongly correlated can be thought of as `glued together' by these low degree metabolites.Comment: 12 pages main text with 2 figures and 2 tables. 16 pages of Supplementary material. Revised version has title changed and contains study of 3 organisms instead of 1 earlie