Bipolar System Research Articles

An analysis of parameters affecting ampacity in aircraft bipolar MVDC power cables via coupled electrical, thermal, and computational fluid dynamic modelling

AbstractThe next generation of aircraft, including more electric aircraft and all‐electric aircraft, require electric power systems with high power density and low system mass specifications. Increasing the voltage of the system to the range of a few kV, medium voltage (MV), is a reasonable approach to achieving high‐power‐density and low‐system‐mass EPSs for aircraft applications. Higher voltages, however, pose many challenges for aviation MV power cables such as arcs and arc tracking, partial discharges (PDs), and thermal management. In this regard, thermal management is more challenging since heat transfer by convection is greatly reduced at wide‐body aircraft's cruising altitudes due to the reduced air pressure. In this paper, a finite element method (FEM) model is developed in COMSOL Multiphysics for an aircraft bipolar MVDC (±5 kV) power cable. Using the model, the maximum permissible cable current at a low pressure of 18.8 kPa (at an altitude of 12.2 km from sea level, the usual cruising altitude for wide‐body aircraft) is calculated. Also, an analytical model is developed based on analytical and proven empirical correlations governing conductive, radiative, and convective heat transfers at the steady state to estimate the ampacity of the bipolar cable system at reduced pressure. It was shown that the proposed analytical model can be used for atmospheric pressure and systems with a larger number of poles, expanding its range of applications. The results of the FEM and analytical models correlate at wide ranges of parameters such as ambient temperature, duct size, distance between the positive and negative pole cables, and the overall diameter of the cables. The influence of horizontal and vertical arrangement of poles is included in the analytical model. The results of this study can be used to design bipolar MVDC power cable systems for the envisaged wide‐body AEA.

From regional autonomy towards horizontal and vertical congruence coalition politics in Polish regions in the period 1998–2018

ABSTRACT In 1999 regional self-government was established in Poland and, subsequently, politics began to operate in a new multilevel setting. The question raised in this article is, how did Polish parties adapt to functioning in a multilevel system focusing on coalition politics? The analysis of documents – regional assemblies’ resolutions were used to track regional coalition formation in the period 1998–2018 – was supplemented by data gathered from the author’s interviews with regional politicians. The tendency to avoid cross-cutting coalitions was evident from the first two elections when regional politics was rather autonomous. Vertically and horizontally congruent coalitions gradually became standard when advantageous conditions occurred after 2006. The particular features of the party system leading to the avoidance of cross-cutting coalitions were the role of socio-political cleavage, that is a ‘post-communist divide’ and, later, rising polarization within a bipolar party system. Cross-cutting coalitions were occasionally acceptable but never those requiring cooperation between a majority party forming the government and the main opposition party at the central level. Recent studies indicate the rise of divergent coalitions in Europe, but in Polish regions, the contrary tendency has been observed.

Firefly-inspired bipolar information indication system actuated by white light

The indication of information in materials is widely used in our daily life, and optical encoding materials are ideal for information loading due to their easily readable nature and adjustable optical properties. However, most of them could only indicate one type of information, either changing or unchanging due to the mutual interference. Inspired by firefly, we present a non-interfering bipolar information indication system capable of indicating both changing and unchanging information. A photochemical afterglow material is incorporated into the photonic crystal matrix through a high-throughput technique called shear-induced ordering technique, which can efficiently produce large-area photonic crystal films. The indication of changing and unchanging information is enabled by two different utilizations of white light by the afterglow material and photonic crystals, respectively, which overcome the limitations of mutual interference. As a proof of concept, this system is used to indicate the changing photodegradation level of mecobalamin (a photosensitive medicine) and unchanging intrinsic drug information with anti-counterfeiting functionality, which is a promising alternative to instantly ascertain the efficacy of medicine at home where conventional assays are impractical.

Nuclear powers’ reaction to the US development and testing of thermonuclear weapons in the early 1950s.

The article examines US, Soviet and British reaction to the development and testing of American thermonuclear weapons. Based on the analysis of published documents and the press of the three countries, archival materials, debates in the British Parliament and the American Congress, the authors assess the perception of how the emergence of new super-powerful weapons influenced the state of international relations, Soviet-American confrontation, and the position of Great Britain. The development of thermonuclear weapons, which became a new factor in the emerging bipolar system of international relations, was largely the result of an irreconcilable conflict between the superpowers. The risk of universal destruction associated with the advent of "superbomb" did not stop the arms race, but the emerging trend to achieve relative parity in the nuclear sphere gradually turned into a guarantee of stability, based on the fear of retaliation. However, at the dawn of the nuclear era, thermonuclear tests seemed to increase the degree of unpredictability on the world stage, raising questions not only about how new developments would affect the balance of power and strategies of the leading powers, but also whether thermonuclear explosions could be properly controlled, what their consequences would be and how serious the dangers of radiation contamination could be. That is why the hydrogen bomb tests prompted both statesmen and the public to address the issue of nuclear arms control. However, the high degree of conflict and uncertainty, and most importantly, the perception of power as the basis of the position held by a state in the system of international relations led to the fact that issues of arms control receded into the background before the imperatives of the arms race.

Protection Coordination Strategy for the Distributed Electric Aircraft Propulsion Systems

The current trend in distributed electric aircraft propulsion systems is to utilize the DC bus system at higher voltage levels than conventional aircraft systems. With Boeing and Airbus utilizing the +/−270 V bipolar DC bus system, the research on high-voltage systems is increasing gradually, with voltage levels ranging from 1 to 10 kV systems or +/−0.5 to +/−5 kV DC bus systems. These voltage levels present considerable challenges to the distributed electric aircraft propulsion systems. In addition to partial discharge effects, there are other challenges, particularly the challenge associated with effectively limiting short-circuit fault currents due to the low cable impedance of the distribution system. The cable impedance is a significant factor that determines the fault current during fault conditions. Due to the low impedance, there is a sharp increase in fault current, necessitating an enhanced protection strategy, which ensures that the system is adequately protected. This paper introduces a coordinated protection strategy specifically designed for distributed electric aircraft propulsion systems to mitigate or prevent short-circuit faults. The proposed algorithm utilizes an I2t-based strategy and the current-limiting-based strategy to protect the system from short-circuit faults and overload conditions. Redundant backup protection is also included in the algorithm in case the circuit breaker fails to operate.

Recognition of Hijaiyah Letter Patterns Using The Bidirectional Associative Memory Method

Artificial Intelligence has a very broad scope so it can solve very complex problems. Hijaiyah letter pattern recognition using the Bidirectional Associative Memory (BAM) method has the ability to detect maximum results for the blind who are learning to recognize hijaiyah letters in producing information using a bipolar system. The problem in this research is the difficulty for blind people in recognizing hijaiyah letters and patterns, so this research was designed to help blind people learn hijaiyah letters so that they can easily understand the patterns and types of letters using the 3x3 order matrix concept. In the BAM has the advantage of layers that are interconnected between one layer and another layer so that they can be connected from the input layer to the output layer. This research will produce a Hijaiyah letter recognition pattern using the 3x3 Matrix system to design a system for identifying Hijaiyah letter patterns. From the results of the tests that have been carried out, there are 5 Hijaiyah letter patterns, namely ا, ث, ج, ذ and ش which are processed by pattern recognition with a value of 1. [1.1] [1,-13],[-1,1][3,-11 ],[1,-1] [-9,-17],] [-1,1][ [13,9], [-1,1][-13,13]. Of the 5 Hijaiyah letter patterns, only 2 letter patterns were able to be recognized by the system, namely the letters ذ and ش, and 3 patterns were not able to be recognized by the system. Thus it can be concluded that not all patterns using the BAM method are able to recognize patterns precisely and correctly.

A sustainable bioprocessing system leveraging gas fermentation and bipolar membrane electrodialysis system for direct recovery of acetic acid

This study examined the integration of gas fermentation with bipolar membrane electrodialysis (BPMED) for sustainable production of acetic acid and bases, focusing on medium recycling and ion-exchange membrane optimisation. Gas fermentation was performed using an acetogenic microbe, Eubacterium callanderi KIST612, in a custom-designed gas bioreactor. The BPMED system was operated under specific voltage conditions to evaluate the proton and hydroxyl ion generation, ion concentration, and residual ratios. Gas fermentation consistently generated acetate with a stable CO2 consumption rate (0.167 mmol gcell−1) and an increased rate of conversion of carbon into biochemicals via methanol. The BPMED system efficiently produced acetic acid (acetate extraction rate of 99.72 %–99.82 %) and hydroxide ions (from 8 to 18 V), with operational challenges identified at higher voltage levels (≥20 V). The BPMED process, which includes additional membranes and exhibits a lower acetate flux than the ED process, had remarkable cost-effectiveness, surpassing the ED integration process by 17.6 %. This economic advantage was paralleled by a significant environmental benefit, where the BPMED process reduced carbon dioxide emissions by 7.4 % compared with the ED process. These results suggest that integrating gas fermentation with BPMED is a viable and sustainable approach for acetic acid production.

Russian diplomacy and the security policy of the European Union

European security policy has evolved over a number of historical stages. The fi rst developments appeared in the 50s — 90s of the last century within the framework of the Yalta- Potsdam bipolar system. After 1991, a number of projects for the development of the militarypolitical integration of the European Union, strategically linked to NATO, followed. At the present stage, Europe has embarked on an aggressive policy towards Russia, threatening its sovereignty and security. In this situation, Russia is determined to defend its national interests in order to neutralize emerging threats, create conditions for the cessation of unfriendly actions and form a new model of co-existence with European states.

Bipolar Current-Fed DC–DC Converter With Automatic Voltage Balance and Full Range ZVS for Bipolar DC System

Bipolar Current-Fed DC–DC Converter With Automatic Voltage Balance and Full Range ZVS for Bipolar DC System

Transurethral bipolar enucleation using a TUEB loop for large benign prostatic hyperplasia: a retrospective cohort study.

We aimed to assess the efficacy and safety of transurethral enucleation with bipolar system (TUEB) regardless of the prostate size using a specially developed TUEB loop. A total of 251 patients who underwent TUEB were categorized into two groups depending on the prostate volume (PV): small-PV (≤ 80mL) group, 133 patients; large-PV (> 80mL) group, 118 patients. Comparisons of background information and treatment outcomes were performed between the groups. Operation (113.5 vs 166.4min), enucleation (49.4 vs 68.1min), and morcellation (11.4 vs 26.4min) times were longer and hemoglobin decreased significantly (0.84 vs 1.30g/dL) in the large PV group. However, the enucleation efficiency (enucleated weight per enucleation time; 0.71 vs 0.97g/min) and prostate-specific antigen reduction rate (24.6% vs 16.1%) were significantly better in the large-PV group, with similar enucleation rates (enucleated weight per transitional zone volume; 82% vs 81%). The International Prostate Symptom Score, uroflowmetry maximum flow rate, and post-void residual urine in both groups improved at 3, 6, and 12months compared with baseline. No patient underwent blood transfusion. There were no differences in the frequency of postoperative clot retention, urethral stricture, or stress incontinence at 3, 6, and 12months. TUEB using a TUEB loop resulted in high levels of satisfaction regarding the enucleation efficiency, efficacy, and safety for BPH surgery regardless of the prostate size. TUEB should be considered one of the best treatment options for large BPH that is uncontrollable with medication.

Development of closed bipolar electrode based L-lactate sensor employing quasi-direct electron transfer type enzyme with cyclic voltammetry

Herein, we present a proof-of-concept of an enzyme sensor combining closed bipolar electrode system with quasi-direct electron transfer (DET) type enzyme. The closed bipolar electrode system was tested using cyclic voltammetry, with L-lactate as a model substrate. L-Lactate was detected through measurement of the change in junction potential across the bipolar electrode. This change in junction potential was caused by reduction of amino reactive phenazine ethosulfate conjugated to Aerococcus vilidans derived engineered L-lactate oxidase (AvLOx) which shows a quasi-DET signal. Using the closed bipolar electrode system allowed simultaneous measuring using cyclic voltammetry and open circuit potential (OCP) and achieved a limit of detection of 400 μM and 76.2 μM lactate respectively. The sensor was then demonstrated to perform with equivalent sensitivity using OCP across varying surface areas. To the best of our knowledge this is the first time a closed bipolar electrode system has been used with an enzyme which is capable of quasi-direct or direct electron transfer. This work can be expanded further to other enzymes capable of directly altering the junction potential of an electrode surface.

Intelligent decision support system for pulmonary tuberculosis detection using bipolar fuzzy utility matrix and bipolar Mamdani fuzzy inference system

Tuberculosis (TB) stands as the second leading global infectious cause of death, following closely behind the impact of COVID-19. The standard approach to diagnose TB involves skin tests, but these tests can yield inaccurate results due to limited access to healthcare and insufficient diagnostic resources. To enhance diagnostic accuracy, this study introduces a novel approach employing a Bipolar Fuzzy Utility Matrix Inference System (BFUMIS) and a Bipolar Mamdani Fuzzy Inference System (BMFIS) to assess TB disease levels. By considering factors associated with the causation of TB, the study devises suitable membership functions for bipolar fuzzy sets (BFS) using both triangular and trapezoidal fuzzy numbers. Using a point factor scale, the study clusters the rules systematically and assesses the level of uncertainty within these grouped rules by utilizing bipolar triangular fuzzy numbers (BTFN). To handle the BTFN, this study proposes converting bipolar triangular fuzzy into bipolar crisp score (CBTFBCS) algorithm as a defuzzification method. The optimal bipolar fuzzy utility sets (BFUS) are determined from the bipolar fuzzy utility matrix to identify patients’ TB disease levels. These sets play a pivotal role in characterizing the severity of TB disease levels in patients. Additionally, rigorous validation of the utility framework is accomplished through measures of bipolar fuzzy satisfactory factors and sensitivity analyses. Furthermore, the study introduces the BMFIS, which presents a novel perspective on the conventional fuzzy inference system. This innovative system integrates the Mamdani fuzzy inference system (MFIS) into a bipolar fuzzy context, enriching the diagnostic process with enhanced insights. To demonstrate the efficacy of the proposed methods, extensive validation is carried out using actual clinical data. The performance metrics used in this validation effectively demonstrate the superiority of the proposed approach.

Transition from parliamentarism to presidentialism and the restructuring of the Turkish party system

ABSTRACT The role of institutional factors on party system change has received increasing scholarly attention. This article analyses the emergence of new trends in the structure of party competition in Turkey following the transition from parliamentarism to presidentialism in 2017. The newly-adopted presidential system endowed the president with extraordinary powers and reduced the role of the parliament. Presidential elections assumed central importance in electoral politics; competition was structured by pre-electoral coalitions and party alliances; more than two-thirds of the voters cast their ballots for one of the two main electoral alliances; and there was a trend towards the emergence of a bipolar party system. The analysis presented in this study emphasizes the role of institutional engineering, especially the introduction of presidentialism and changes in electoral laws, as major factors in the restructuring of the Turkish party system.

A New Bipolar High-Voltage Pulsed Charging System

A New Bipolar High-Voltage Pulsed Charging System

The Outflow of The Protostar in B335. I.

The isolated globule B335 contains a single, low-luminosity Class 0 protostar associated with a bipolar nebula and outflow system seen nearly perpendicular to its axis. We observed the innermost regions of this outflow as part of JWST/NIRCam Guaranteed Time Observations program 1187, primarily intended for wide-field slitless spectroscopy of background stars behind the globule. We find a system of expanding shock fronts with kinematic ages of only a few decades emerging symmetrically from the position of the embedded protostar, which is not directly detected at NIRCam wavelengths. The innermost and youngest of the shock fronts studied here shows strong emission from CO. The next older shock front shows less CO and the third shock front shows only H2 emission in our data. This third and most distant of these inner shock fronts shows substantial evolution of its shape since it was last observed with high spatial resolution in 1996 with Keck/NIRC. This may be evidence of a faster internal shock catching up with a slower one and of the two shocks merging.

Cardiac Pulsed Field Ablation Lesion Durability Assessed by Polarization-Sensitive Optical Coherence Reflectometry.

Pulsed field ablation uses electrical fields to cause nonthermal cell death over several hours. Polarization-sensitive optical coherence reflectometry is an optical imaging technique that can detect changes in the tissue ultrastructure in real time, which occurs when muscular tissue is damaged. The objective of this study was to evaluate the ability of a polarization-sensitive optical coherence reflectometry system to predict the development of chronic lesions based on acute changes in tissue birefringence during pulsed field ablation. Superior vena cava isolation was performed in 30 swine using a biphasic, bipolar pulsed field ablation system delivered with a nonirrigated focal tip catheter. Acute changes in tissue birefringence and voltage abatement were analyzed for each individual lesion. A high-resolution electroanatomical map was performed at baseline and 4 to 12 weeks after ablation to locate electrical gaps in the ablated area. A total of 141 lesions were delivered and included in the analysis. Acute electrical isolation based on the electroanatomical map was achieved in 96% of the animals, but chronic isolation was only seen in 14 animals (46%). The mean voltage abatement of lesions that showed recovery was 82.8%±14.6% versus 84.4%±17.4% for those that showed fibrosis (P=0.7). The mean acute reduction in tissue birefringence in points demonstrating fibrosis was 63.8%±11.3% versus 9.1%±0.1% in the points that resulted in electrical gaps. A threshold of acute reduction of birefringence of ≥20% could predict chronic lesion formation with a sensitivity of 96% and a specificity of 83%. Acute tissue birefringence changes assessed with polarization-sensitive optical coherence reflectometry during pulsed field ablation can predict chronic lesion formation and guide the ablation procedure although limited by the tissue thickness.

Outcome of Monopolar versus Bipolar Transurethral Resection of Prostate

Introduction: Transurethral resection of the prostate is the gold standard surgical treatment for benign prostatic hyperplasia with the lower urinary tract symptoms. Bipolar system is a new in technology to lower the adverse effects of monopolar system. This study was designed to find out clinic-demographic data and peri-operative outcomes of the monopolar versus bipolar transurethral resection of prostate. Methods: This prospective comparative study was conducted from June 2022 to March 2023, in the Department of Urology of Bir Hospital, National Academy of Medical Sciences, Nepal. Ethical approval of research was taken from Institutional Review Board, NAMS: Ref No. 735/2079/80. Microsoft Excel was used for descriptive analysis for clinic-demographic and outcome variable data, were presented in frequencies and percentages and their relation were analyzed by chi-square test/fisher’s exact test. A p-value of <0.05 statistically significant. Result: A total 80 patients were compared, bipolar(40 cases) and monopolar(40 cases). There were no differences in the incidence of hyponatremia, clot retention and evacuation rate, re-catheterization rate, mean hemoglobin loss, and mean length of hospital stay. The longer duration of operation time (>60 min) was observed in bipolar transurethral resection ( p=0.001). The transurethral resection syndrome was found only in M-TURP. Conclusion: Both monopolar and bipolar transurethral resection of prostate showed no statistical differences in the amount of resected prostatic tissue, the incidence of hyponatremia, length of hospital stays, blood transfusion rate, re-catheterization rate, clot retention and evacuation rate. The shorter duration of surgery and the trans-urethral resection syndrome was observed in M-TURP.

SOLVING BIPOLAR FULLY FUZZY SYLVESTER MATRIX EQUATIONS WITH NEGATIVE FUZZY NUMBERS

Sylvester matrix equations play a crucial role in control theory for controller design. Bipolar Fully Fuzzy Sylvester Matrix Equations (FFSME), incorporating both positive and negative components, are employed in controller design to address uncertainties that may affect a system’s performance and stability. However, there is not much existing research on combining bipolar fuzzy numbers and FFSME,and most of them mainly deal with positive coefficients. Thus, this paper presents a method that enables solving the negative coefficient of bipolar FFSME in the form of Left-Right (LR) triangular fuzzynumbers using an Associated Bipolar Linear System (ABLS). To obtain the ABLS, bipolar FFSME is transformed into a bipolar Fully Fuzzy Linear System (FFLS) using the Kronecker product and Vecoperator. Subsequently, the solution is derived through the inverse method, and the equation of the ABLS is rearranged as a bipolar fuzzy matrix. Additionally, this paper provides two numerical examples to illustrate the applicability of the constructed method.

Assessing the Safety and Effectiveness of Bipolar Technology in Transurethral Prostate Resection: A study in a Tertiary Care Private Hospital

Background: Benign enlargement of prostate (BEP) is a common affliction among aging males, predominantly emanating from the transition zone of the prostate, resulting in lower urinary tract symptoms. Despite the availability of diverse treatment modalities, transurethral resection of prostate (TURP) has conventionally served as a benchmark intervention. Recently, there has been a growing interest in bipolar energy techniques, spurred by their potential advantages in mitigating complications such as TUR syndrome and surgical bleeding. Objectives: The main aim of the study to evaluate the safety profile (including serum sodium and hemoglobin reductions, clot retention, TUR syndrome, catheterization duration, and hospital stay) and efficacy (resection rate, maximum flow rate increase, and International Prostate Symptom Score reduction) within the bipolar technique for the TURP. Methods & Materials: A prospective observational study was conducted at the Department of Urology, Square Hospitals Ltd, Dhaka, Bangladesh, spanning December 2020 to November 2021. The study employed comprehensive preoperative assessments, including bipolar transurethral resection of the prostate (B-TURP) using Olympus ESG-400 energy platform. Surgical parameters, postoperative monitoring, and statistical analysis were meticulously executed to evaluate outcomes and complications for symptomatic benign enlargement of prostate. Results: In a sample of 50 individuals undergoing bipolar transurethral resection of the prostate (B-TURP), the distribution of ages revealed 66.97±7.95 years as the bipolar system's average age, ranging from 53-82 years. The majority resided in urban areas (62%), with family income predominantly in the 25000-50000 bracket (42%). Preoperative baseline variables, including IPSS, Qmax, serum hemoglobin, and sodium levels, exhibited similar values between groups. Intraoperatively, the mean resection rate was 0.56±0.16 gm/min. Postoperatively, B-TURP resulted in a slight ......

Improved Dual Active Bridge DC–DC Converter With Symmetric Bipolar Output by Utilizing a Switched-Capacitor Circuit for Bipolar DC Distribution System

The bipolar dc distribution system is a promising solution due to its advantages in efficiency and reliability, but there are also challenges of pole voltage imbalance. By using a simple switched-capacitor circuit, this paper presents a semi-dual active bridge converter with symmetrical bipolar output characteristics. The converter is capable of single-stage power conversion, offering the advantages of low cost and high-power conversion efficiency. Moreover, the symmetrical bipolar output voltage can be achieved without an additional voltage balancer and feedback control under unbalanced load conditions, which reduces system cost and control system complexity. In addition, the proposed converter also has a significant advantage over existing solutions in terms of the number of semiconductor devices and magnetic components. A detailed analysis of the proposed converter is presented, including the operation principle, steady-state performance, soft-switching performance, voltage gain, voltage/current stresses, efficiency and loss analysis, and control method. Finally, a 1-kW prototype is developed and tested to verify the performance of the proposed converter.