Effect of swirl and number of swirler vanes on combustion characteristics of methane inverse diffusion flame

Vipul Patel,Rupesh Shah 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

An experimental study is performed to explore the effect of swirl and number of swirler vanes on combustion characteristics of methane inverse diffusion flame (IDF) using 30 0 swirler. Influence of varying the number of vanes (4, 6 and 8) on structure and appearance of IDFs is studied. Swirling IDFs are observed with dual flame structure. Length of both IDFs depends on Reynolds number (Re air ) and equivalence ratio (Φ). Temperature measured along the centerline in swirling IDF is greater than non-swirling IDF. Radial temperature distribution shows that the swirling effect intensify combustion process. Effect of Φ on CO emission revels that non-swirling IDFs emit more CO compared to swirling IDFs. The lowest NO x emission is observed in swirling IDFs with 6 vanes. Study indicates that the IDFs with swirl results in low emission of CO and NO x .

Diversity characteristics of four-element ring slot-based MIMO antenna for sub-6-GHz applications

Vipul Kaushal,Amit Birwal,Kamlesh Patel Electronics and Telecommunications Research Instit 2023 ETRI Journal Vol.45 No.4

This paper proposes four-ring slot resonator-based MIMO antennas of 75×150 mm² without and with CSRR structures in the sub-6-GHz range. These orthogonal-fed antennas have shown diverse characteristics with dual polarization. L-shaped parasitic structures have increased the isolation (i.e., >40 dB) in the single-element antenna over the band of 3.4 GHz-3.8 GHz. A set of three CSRR structures in the MIMO antenna reduced the coupling between antenna ports placed in an inline arrangement and enhanced the isolation from 12 dB to 20 dB and the diversity characteristics. The S-parameters of both MIMO antennas are measured and used to evaluate MIMO parameters like ECC, TARC, MEG, and channel capacity loss. The simulation results show the variations in the gain and directivity on exciting linear and dual polarizations. The diversity performance of the reported MIMO antennas is suitable for 5G applications.

Analysis and design of demountable embedded steel column base connections

Dongxu Li,Brian Uy,Vipul Patel,Farhad Aslani 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.3

This paper describes the finite element model for predicting the fundamental performance of embedded steel column base connections under monotonic and cyclic loading. Geometric and material nonlinearities were included in the proposed finite element model. Bauschinger and pinching effects were considered in the simulation of embedded column base connections under cyclic loading. The degradation of steel yield strength and accumulation of plastic damage can be well simulated. The accuracy of the finite element model is examined by comparing the predicted results with independent experimental dataset. It is demonstrated that the finite element model accurately predicts the behaviour and failure models of the embedded steel column base connections. The finite element model is extended to carry out evaluations and parametric studies. The investigated parameters include column embedded length, concrete strength, axial load and base plate thickness. Moreover, analytical models for predicting the initial stiffness and bending moment strength of the embedded column base connection were developed. The comparison between results from analytical models and those from experiments and finite element analysis proved the developed analytical model was accurate and conservative for design purposes.

Behaviour and design of demountable steel column-column connections

Dongxu Li,Brian Uy,Vipul Patel,Farhad Aslani 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.2

This paper presents a finite element (FE) model for predicting the behaviour of steel column-column connections under axial compression and tension. A robustness approach is utilised for the design of steel columncolumn connections. The FE models take into account for the effects of initial geometric imperfections, material nonlinearities and geometric nonlinearities. The accuracy of the FE models is examined by comparing the predicted results with independent experimental results. It is demonstrated that the FE models accurately predict the ultimate axial strengths and load-deflection curves for steel column-column connections. A parametric study is carried out to investigate the effects of slenderness ratio, contact surface imperfection, thickness of cover-plates, end-plate thickness and bolt position. The buckling strengths of steel column-column connections with contact surface imperfections are compared with design strengths obtained from Australian Standards AS4100 (1998) and Eurocode 3 (2005). It is found that the column connections with maximum allowable imperfections satisfy the design requirements. Furthermore, the steel column-column connections analysed in this paper can be dismantled and reused safely under typical service loads which are usually less than 40% of ultimate axial strengths. The results indicate that steel column-column connections can be demounted at 50% of the ultimate axial load which is greater than typical service load.

Biopsy Related Prostate Status Does Not Affect on the Clinicopathological Outcome of Robotic Assisted Laparoscopic Radical Prostatectomy

최훈,고영휘,강성구,강석호,박홍석,천준,Vipul R. Patel 대한암학회 2009 Cancer Research and Treatment Vol.41 No.4

Purpose To determine whether the biopsy core number and time interval between prostate biopsy and radical prostatectomy affect the operative and oncologic outcome of robot assisted laparoscopic radical prostatectomy (RALP). Materials and Methods From January 2008 to April 2009, a single surgeon performed 72 RALPs after an initial learning period of 30 cases. The relationship between time from biopsy to prostatectomy and biopsy core number with operative time and estimated blood loss (EBL) were initially evaluated with a linear regression model. These patients were classified into groups according to whether the interval from biopsy to RALP was within four weeks or not, and whether there were less than or greater than 10 core specimens removed. Results RALP was performed in 34 patients within four weeks of biopsy, and in 38 patients more than 4 weeks after biopsy. According to the number of core specimens removed, less than 10 cores were performed in 10 patients, and more than 10 cores were performed in 62 patients. Using an interval of 4 weeks as the cutoff point, early surgery was associated with longer operating time (232.6 vs 208.8 min) and increased estimated blood loss (305.1 vs 276.9 mL). For cases with more than 10 biopsy cores, there was a slight increase in operative time (229.2 vs 210.3 min). None of these differences were statistically significant by multivariate analysis. Conclusion Our data suggests that there is no reason to delay RALP to more than 4 weeks after prostate biopsy. It also revealed that the number of biopsy cores (up to 14) did not influence operative outcome. Thus, RALP is a feasible procedure regardless of the biopsy related prostate state.

Modified apical dissection improves early continence in robot-assisted laparoscopic radical prostatectomy: Comparative study between modified apical dissection and anterior suspension stitch

강하은,김승빈,노태일,심지성,강석호,천준,태종현,Vipul R. Patel,강성구 대한비뇨의학회 2022 Investigative and Clinical Urology Vol.63 No.6

Purpose: Recently, the modified apical dissection (MAD) technique in robot-assisted laparoscopic radical prostatectomy (RARP) has shown excellent functional outcomes but has never been rigorously validated at various institutions. This study aimed to evaluate the effect of MAD on early continence and potency compared with the anterior suspension stitch (SS) technique. Materials and Methods: A total of 100 patients who underwent RARP with SS and 100 who underwent RARP with MAD by a single surgeon were propensity score matched and retrospectively compared for continence and potency recovery at 1 week and 1, 3, 6, 9, and 12 months. Results: Continence was reached in 20.6%, 33.3%, 67.2%, 74.1%, 81.1%, and 83.0% of patients in the SS group, compared with 49.2%, 73.3%, 86.8%, 96.6%, 100.0%, and 100.0% in the MAD group at postoperative 1 week and 1, 3, 6, 9, and 12 months, respectively. In the SS group, potency rates were 0.0%, 20.0%, 50.0%, 66.7%, 75.0%, and 83.3%; in the MAD group, the rates were 50.0%, 90.0%, 88.9%, 100.0%, 100.0%, and 100.0%. Recovery of continence was higher in the MAD group within the first 6 months (p=0.005, <0.010, 0.041, 0.016 at 1 week, 1, 3, and 6 months). There were no significant differences in potency recovery rates between the two groups (all p≥0.05). Conclusions: The MAD technique results in earlier recovery of continence compared with the SS technique.

Analysis and design of demountable steel column-baseplate connections

Dongxu Li,Brian Uy,Farhad Aslani,Vipul Patel 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.4

This paper aims to investigate the demountability of steel column-baseplate connections subjected to monotonic and cyclic loading. This paper presents the finite element analysis of steel column-baseplate connections under monotonic and cyclic loading. The finite element model takes into account the effects of material and geometric nonlinearities. Bauschinger and pinching effects were also included in the developed model, through which degradation of steel yield strength in cyclic loading can be well simulated. The results obtained from the finite element model are compared with the existing experimental results. It is demonstrated that the finite element model accurately predicts the initial stiffness, ultimate bending moment strength of steel column-baseplate connections. The finite element model is utilised to examine the effects of axial load, baseplate thickness, anchor bolt diameter and position on the behaviour of steel column-baseplate connections. The effects of various parameters on the demountability of steel column-baseplate connections are investigated. To achieve a demountable and reusable structure, various design parameters need to be considered. Initial stiffness and moment capacity of steel columnbaseplate connections are compared with design strengths from Eurocode 3. The comparison between finite element analysis and Eurocode 3 indicates that predictions of initial stiffness for semi-rigid connections should be developed and improved design of the connections needs to be used in engineering practice.

Confinement models for high strength short square and rectangular concrete-filled steel tubular columns

Farhad Aslani,Brian Uy,Ziwen Wang,Vipul Patel 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.5

While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength (<i>f</i>’<i>_c</i> = 20 - 110 N/mm²), steel yield strength (<i>f_y</i> = 220 - 850 N/mm²), width-to-thickness (<i>B/t</i>) ratios in the range of 15-52, as well as the length-to-width (<i>L/B</i>) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.

Lessons learned from 12,000 robotic radical prostatectomies: Is the journey as important as the outcome?

강성구,심지성,Fikret Onol,K. R. Seetharam Bhat,Vipul R. Patel 대한비뇨의학회 2020 Investigative and Clinical Urology Vol.61 No.1

Robotic radical prostatectomy (RARP) is a standardized treatment for localized prostate cancer, which provides better functional outcomes and similar oncological outcomes compared to open approaches. Here, we share our experience of 12,000 RARPs by describing the outcomes of the procedure in terms of positive surgical margin (PSM), continence, and potency as well as by presenting our detailed surgical technique with recent modifications. On cancer control, the PSM rates were 5.8% and 26.1% in T2 and T3, respectively. On the premise of not compromising oncologic outcomes, a tailored approach to individual patients is essential. Even if an extracapsular extension is suspected, neurovascular bundle (NVB) tailoring can be applied using an anatomical landmark to preserve maximal nerve tissue with a negative margin. We developed a nomogram as a useful tool for deciding the degree of tailoring. For improvements of functional outcomes, we used athermal retrograde early release with a toggling technique, wherein the nerve dissection from the bottom helps with blood loss and allows for smooth NVB releasing. Additionally, we recently performed a new minimal apical dissection/lateral prostatic fascia preservation technique. As a result, our 1-week continence rate was 37% and the 6-week rate was 77.6%. In addition, the potency rates in our study were 69%, 82%, and 92% at 3 months, 6 months, and 1 year, respectively (preoperative Sexual Health Inventory for Men scores >21 & bilateral full nerve spared).

Analysis and design of demountable circular CFST column-base connections

Dongxu Li,Jia Wang,Brian Uy,Farhad Aslani,Vipul Patel 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.5

In current engineering practice, circular concrete-filled steel tubular (CFST) columns have been used as effective structural components due to their significant structural and economic benefits. To apply these structural components into steelconcrete composite moment resisting frames, increasing number of research into the column-base connections of circular CFST columns have been found. However, most of the previous research focused on the strength, rigidity and seismic resisting performance of the circular CFST column-base connections. The present paper attempts to investigate the demountability of bolted circular CFST column-base connections using the finite element method. The developed finite element models take into account the effects of material and geometric nonlinearities; the accuracy of proposed models is validated through comparison against independent experimental results. The mechanical performance of CFST column-base connections with both permanent and demountable design details are compared with the developed finite element models. Parametric studies are further carried out to examine the effects of design parameters on the behaviour of demountable circular CFST column-base connections. Moreover, the initial stiffness and moment capacity of such demountable connections are compared with the existing codes of practice. The comparison results indicate that an improved prediction method of the initial stiffness for these connections should be developed.