Bipolar Systems Research Articles

Comparative Assessment of Thermal Damage Induced by Bipolar Forceps in a Bovine Liver.

Bipolar electrocautery systems in neurosurgical procedures may induce thermal damage to adjacent tissues, especially neural tissues. Therefore, it is crucial to control thermal spread from the tips of bipolar forceps into adjacent tissues. The goal of this study was to compare the thermal damage induced in unintended adjacent tissues during coagulation with 6 different bipolar forceps. Fresh ex vivo bovine liver tissues were coagulated with 6 different bipolar forceps: Aesculap® nonstick, Atlas Choice™, ISOCOOL®, SilverGlide®, Spetzler™-Malis®, and VersaTru® (45 trials per bipolar forceps). For all forceps, coagulation was performed with a power setting of 35 Malis units, 1-mm tip spacing, and 3-second activation time. Tissue samples were evaluated for the extent of thermal damage (30 trials per bipolar forceps). Tissue temperatures were measured with thermocouples placed in the tissues (15 trials per bipolar forceps). The area and maximum depth of thermal damage were measured manually with image analysis software. The injury area induced by ISOCOOL® and Atlas Choice™ bipolar forceps was significantly less than that of the Aesculap® nonstick (P < .001), SilverGlide® (P < .001), Spetzler™-Malis® (P < .001), and VersaTru® (P < .001). The areas of thermal injury caused by the ISOCOOL® and Atlas Choice™ forceps were not statistically significantly different from each other (P = .08). Lesions from the ISOCOOL® and Atlas Choice™ forceps showed significantly less depth of injury than the Aesculap® nonstick (P = .001), SilverGlide® (P < .001), Spetzler™-Malis® (P < .001), and VersaTru® (P < .001). There was no statistically significant difference in the depth of thermal injury between the ISOCOOL® and Atlas Choice™ forceps (P = 1.0). Bipolar forceps that effectively limit excessive thermal dissipation reduce the risk of unintended injury to adjacent or peripheral tissues. In an ex vivo bovine liver model, coagulation tests with ISOCOOL® and Atlas Choice™ bipolar forceps resulted in less depth and lower mean injury areas compared with other forceps.

Signal Acquisition and Algorithm Design for Bioimpedance-Based Heart Rate Estimation from the Wrist

Background: Heart rate (HR) is a critical biomarker that provides insights into overall health, stress levels, and the autonomic nervous system. Pulse wave signals contain valuable information about the cardiovascular system and heart status. However, signal acquisition in wearables poses challenges, particularly when using electrical sensors, due to factors like the distance from the heart, body movement, and suboptimal electrode placement. Methods: Electrical bioimpedance (EBI) measurements using bipolar and tetrapolar electrode systems were employed for pulse wave signal acquisition from the wrist in both perpendicular and distal configurations. Signal preprocessing techniques, including baseline removal via Hankel matrix methods, normalization, cross-correlation, and peak detection, were applied to improve signal quality. This study describes the combination of sensor-level signal acquisition and processing for accurate wearable HR estimation. Results: The bipolar system was shown to produce larger ΔZ(t), while the tetrapolar system demonstrated higher sensitivity. Distal placement of the electrodes yielded greater ΔZ(t) (up to 0.231 Ω) when targeting both wrist arteries. Bandpass filtering resulted in a better signal-to-noise ratio (SNR), achieving 3.6 dB for the best bipolar setup and 4.8 dB for the tetrapolar setup, compared to 2.6 and 3.3 dB SNR, respectively, with the Savitzky–Golay filter. The custom HR estimation algorithm presented in this paper demonstrated improved accuracy over a reference method, achieving an average error of 1.8 beats per minute for the best bipolar setup, with a mean absolute percentage error (MAPE) of 8%. Conclusions: The analysis supports the feasibility of using bipolar electrode setups on the wrist and highlights the importance of electrode positioning relative to the arteries. The proposed signal processing method, featuring a preprocessing pipeline and HR estimation algorithm, provides a proof-of-concept demonstration for HR estimation from EBI signals acquired at the wrist.

Valve-Side Single-Phase-to-Ground Fault Analysis in Bipolar MMC-HVDC Systems With Hybrid SMs

Valve-Side Single-Phase-to-Ground Fault Analysis in Bipolar MMC-HVDC Systems With Hybrid SMs

Electrocatalytic Bipolar Synthesis of Valuable Chemicals

AbstractElectrocatalysis can synthesize kinds of valuable chemicals and plays vital role in developing clean and renewable energy storage and conversion devices. In the traditional electrocatalytic systems, researchers try to synthesize one type of valuable chemical at cathode or anode independently. Recently, electrocatalytic bipolar synthesis of valuable chemicals at both cathode and anode simultaneously becomes popular and attracts much attention. In this minireview, we summarize the latest processes on innovative strategies for electrocatalytic bipolar synthesis of various chemicals. We will discuss the findings according to the categories of the products, including bipolar hydrogen production, bipolar formate production and bipolar hydrogenation. And the associated catalysts optimization, reaction mechanism, and design principles are well introduced. Moreover, the challenges and prospects are highlighted for future developments. This review is timely and will guide others pay more attention to this novel electrocatalytic bipolar synthesis systems.

A novel phaselet-based approach for fault detection and location in HVDC lines

Recently, the popularity of direct current (DC) transmission has surged due to a 30 % reduction in power electronics equipment costs over the last decade. High-Voltage Direct Current (HVDC) transmission lines experience fluctuations in both nominal and faulty states, posing challenges for fault location methods, particularly those based on traveling waves, resulting in imprecise outcomes with an average error margin of ±2 %. This paper investigates a novel fault detection and location approach utilizing wavelet and phaselet transforms. The proposed method focuses on traveling waves in HVDC transmission lines, where the phaselet transform effectively eliminates undesired fluctuations in line currents, improving fault detection accuracy by up to 15 %. By leveraging the traveling time in the faulty line, the exact fault location is calculated with an accuracy of 98.5 %, independent of transmission line parameters, making it applicable to any DC line. Additionally, the method's precision is minimally affected by fault resistance, with <0.5 % deviation even in nonlinear scenarios. Sensitivity analysis conducted on various parameters, including mother wavelet patterns, suggests the optimal solution for each fault type, enhancing detection speed by 20 %. The proposed method is validated using the Cigre HVDC benchmark, confirming its accuracy, speed, and robustness in fault detection and location in HVDC lines. The main contribution of this paper is an accurate, fast, and robust phaselet-based algorithm that reduces fault location errors to <1 % and is applicable to all types of bipolar and monopolar HVDC systems, delivering reliable results for both ground and line faults.

Experimental determination of stray currents in parallel operated cells exemplified on alkaline water electrolysis

Avoiding undesired electric field-driven cell-to-cell ion conduction is a common issue in electrochemical bipolar stacks affecting many processes such as alkaline water electrolysis, chlor-alkali electrolysis, and redox flow batteries. In bipolar stack systems, they are known as ionic shunt or stray currents and flow alongside a cell stack through the electrolyte manifolds bypassing the bipolar plates. A similar phenomenon occurs if multiple single cells are operated in parallel with a common electrolyte supply, even though each individual cell is galvanically isolated. If the parallel cells are operated at different voltages, an electrochemical potential gradient is formed across the electrolyte tube manifold, causing stray currents to flow from one cell to the other. It is important to determine and reduce stray currents and its implications to ensure high system efficiency and maximum system lifetime. This work presents a new approach with which stray currents between parallel operated, galvanically isolated electrochemical cells has been determined for the first time. For this purpose, an ionic 4-point measurement was implemented into an experimental setup with two electrolyzer flow cells with a common electrolyte supply using reference electrodes. This approach was used to measure the potential differences ΔE between both electrolyzers exemplarily for alkaline water electrolysis. Combined with the measured ionic resistances of the electrolyte within the polymeric tube manifold, stray currents were accurately determined. The presented results show that the ionic 4-point measurement could be successfully implemented and validated to experimentally determine stray currents between parallelly operated cells. The method presented enabled stray current measurements with high precision in the mA range. Due to the high cell currents and high ionic tube resistance, the stray current is less than 1 % in the introduced electrochemical setup. The demonstrated systematic measurement approach can be easily transferred to other electrochemical systems or processes.

Modulation of Wide Voltage Range Interface DC-DC Converter in DC Distribution System

Bipolar DC distribution systems rely on various power sources like photovoltaics and distributed energy storage, each with its unique voltage characteristics. To accommodate these fluctuations, interface converters must adjust over a wide voltage range. The bipolar non-isolated DC-DC converter emerges as a promising solution due to its versatile modulation capabilities, reduced switch voltage stress, and cost-effectiveness. This article explores how wide voltage range regulation is achieved in bipolar DC-DC converters interfacing with bipolar DC power grids. It delves into the operational strategies and modulation techniques employed, ensuring stable output despite varying input voltages. Design considerations and challenges associated with implementing such converters are also discussed. An experimental platform was constructed to validate the proposed methodology. Through rigorous testing and analysis, the effectiveness of the topology&amp;apos;s operation mode was confirmed. Real-world data from the experimental setup provided insights into the converter&amp;apos;s performance under different operating conditions, supporting its applicability for bipolar DC distribution systems. In summary, this article provides a comprehensive examination of wide voltage range regulation in bipolar DC-DC converters, highlighting their potential to enhance efficiency and reliability in bipolar DC power grids. Through theoretical discussions and practical validation, it contributes to the advancement and adoption of these converters in modern energy systems.

Bipolar Semiactive Bridge Converter With Cross-Cycle Modulation for Resilience Enhancement in Bipolar DC Distribution Systems

Bipolar Semiactive Bridge Converter With Cross-Cycle Modulation for Resilience Enhancement in Bipolar DC Distribution Systems

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.

Grounded Thyristor Loop-Based Hybrid MMCs for Valve-Side Single-Phase-to-Ground Faults in Bipolar HVdc Systems

Grounded Thyristor Loop-Based Hybrid MMCs for Valve-Side Single-Phase-to-Ground Faults in Bipolar HVdc Systems

Optimizing alkaline solvent regeneration through bipolar membrane electrodialysis for carbon capture

This work demonstrates and characterizes the use of a bipolar membrane electrodialysis for pH-driven CO2 capture and solvent regeneration using potassium hydroxide solutions. The impact of potassium concentration, current density and load ratio on the CO2 desorption efficiency was analyzed and substantiated with an equilibrium model. The system was tested with partially saturated solutions that mimic the expected carbon content of alkaline solvents that have been in contact with flue gas (carbon loading of 0.6 and K+ concentration from 0.5 M to 2 M). Among the tested current densities, 1000 A/m2 demonstrated the highest CO2 desorption efficiency but also the highest energy consumption, whereas 250 A/m2 exhibited the lowest energy consumption (8.8 GJ/ton CO2) but lower CO2 desorption. Efficiency losses were associated with H+ transport across the membranes at high load ratios and decrease of the bipolar membranes water dissociation efficiency at low current densities. This work establishes key performance indicators and describes fundamental characteristics of continuous bipolar membrane electrodialysis systems for regeneration of alkaline solvents used in post-combustion CO2 capture.

Bipolar Clark-Type Oxygen Electrode Arrays for Imaging and Multiplexed Measurements of the Respiratory Activity of Cells.

Various miniature Clark-type oxygen electrodes (COEs), which are typically used to measure dissolved oxygen (DO) concentration in cellular respiration, have been developed since the 1980s. Arrays with individually addressable electrodes that constitute the sensor were used for various applications. However, the large number of leads and contact pads required for connecting the electrodes and the external instrument complicate the electrode layout and make the operation of integrated COE arrays challenging. Here, we fabricated closed bipolar electrochemical systems comprising 6 × 8 and 4 × 4 arrays of COEs for imaging and multiplexed detection. The cathodic compartment was sealed with a hydrophobic oxygen-permeable membrane to separate the internal electrolyte solution from the sample solutions. Using the bipolar Clark-type oxygen electrode (BCOE) arrays and electrochemiluminescence (ECL), we measured the DO concentration at each cathode. The results revealed that the ECL intensity changed linearly with the DO concentration. In addition, we used ECL imaging to investigate the respiratory activity of Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) in suspensions with different cell densities. The ECL images showed that the ECL intensity changed noticeably with the bacterial density. The bacterial respiratory activity was then qualitatively analyzed based on the ECL images acquired successively over a time duration. Further, we measured the antibiotic efficacy of piperacillin, oxacillin, gentamicin, and cefmetazole against E. coli and P. aeruginosa using the BCOE. We found that the ECL intensity increased with the antibiotic concentration, thus indicating the suppression of the bacterial respiratory activity.

Future of the BRICS and the Role of Russia and China

The rise of the BRICS (Brazil, Russia, India, China, and South Africa) and the severity of the 2008 global financial crisis have sparked a new round of debate about the long-term viability of transatlantic norms, ideas , and institutions that have dominated global governance since its commencement. Many of the bodies and organizations that contribute towards global governance were formed between 1945 and 1980 , and have been dominated by Western actors and an agenda centered on the West. To support the main argument of the author there are various chapters in the book Future of the BRICS and the Role of Russia and China that focus on The Evolution of Brics and the international system, Russia and BRICS, China and BRICS and Russia and China in BRICS: Convergences and Divergences. The strength of this book is that it is based on empirical evidence and it address pertinent questions on BRICS , contemporary international relations and monetary institutions. Most importantly, the book sheds light on the future of BRICS and the international financial system by providing a clear overview of BRICS and Unipolar and Bipolar world order systems.

Potential Modulation and Control of Redox Reactions at Bipolar Electrodes Using an Ion-Selective Membrane

Potential difference at a bipolar electrode (BPE)/solution interface was controlled by forming a polymeric Na ion-selective membrane (ISM) on one part of the BPE. Using the difference between the potentials at the solution/cathodic pole and solution/anodic pole interfaces along with a predetermined driving voltage, the potential differences at the cathodic/anodic pole interface were independently regulated. For open bipolar systems, distinct changes in the intensity of electrochemiluminescence (ECL) were observed by varying the location of the ISM and/or the concentrations of the primary ions determining the potential of the ISM. Folded BPE structures with ISMs at one or both ends of the BPEs were more effective in changing the potential differences at the cathodic/anodic pole interface over a wider range. Furthermore, the potential control was efficient and changes in the ECL intensity were more significant in closed bipolar systems. The device was used for measuring analyte concentration by optimizing the size of the cathodic pole employed for detection and adjusting the driving voltage. We believe that the technique can be a starting point to achieve bipolar electrochemical devices with better controllabilities than those of previous bipolar electrochemical systems and similar reliabilities as those of three-electrode systems.

Intelligence as an instrument of state power and its use in international politics

The article makes an attempt to theoretically substantiate why intelligence is an independent instrument of state power, its common and distinctive features with other instruments of power. The paper also provides historical examples of the use of intelligence by various states to influence the behaviour of other states, as well as various approaches used therein.Some features of the use of the intelligence instrument of power by states in the conditions of the existence of bipolar and multipolar political systems are also highlighted in the article. It also draws attention to the incentives for the choice of intelligence as an alternative to other instruments of power in the context of the limiting impact of global collective security systems, in particular the United Nations.

A multichannel closed bipolar platform to visual electrochemiluminescence sensing of caffeic acid as a model: Potential for multiplex detection

In this study, a fully-featured electrochemiluminescence (ECL) sensing platform based on a multichannel closed bipolar system (closed-BP, C-BP) for the determination of caffeic acid (CA) was successfully developed. The system comprises three individual reservoirs connected to each other by two pairs of gold rods as bipolar electrodes. Moreover, a single pair of gold rods functions as the driving electrodes. Due to configuration consisting of three channels and double-bipolar electrodes, the detection of CA was accomplished in two oxidation and reduction pathways within a single device. Firstly, through close observation of the reactions occurring within the device and utilizing a universal pH indicator and bipolar electrodes, a precise mechanism for the current bipolar systems was initially proposed. Then, the concentration of CA was monitored in the reporting chamber through the following ECL intensities resulting from luminol oxidation and H2O2. The monitoring process was performed using both a photomultiplier tube (PMT) and a digital camera. In the process of analyte oxidation, the PMT and visual (camera)-based detection exhibited a linear response from 5 μmol L−1 to 700 μmol L−1 (limit of detection (LOD) 1.2 μmol L−1) and 50 μmol L−1 to 600 μmol L−1 (LOD 14.8 μmol L−1), respectively. In the analyte reduction pathway, the respective values were 30 μmol L−1 to 450 μmol L−1 (LOD 8.6 μmol L−1) and 55 μmol L−1 to 400 μmol L−1 (LOD 21.2 μmol L−1), for the PMT and visual-based detection, respectively. Our experiments have demonstrated the practical application of the sensor array for efficient and high-performance analysis. This innovative design holds significant potential for diverse fields and paves the way for the development of a user-friendly device.

Comprehensive Review on Biomaterials and Their Inherent Behaviors for Hip Repair Applications.

Developing biomaterials for hip prostheses is challenging and requires dedicated attention from researchers. Hip replacement is an inevitable and remarkable orthopedic therapy for enhancing the quality of patient life for those who have arthritis as well as trauma. Generally, five types of hip replacement procedures are successfully performed in the current medical market: total hip replacements, hip resurfacing, hemiarthroplasty, bipolar, and dual mobility systems. The average life span of artificial hip joints is about 15 years, and several studies have been conducted over the last 60 years to improve the performance and thereby increase the lifespan of artificial hip joints. Present-day prosthetic hip joints are linked to the wide availability of biomaterials. Metals, ceramics, and polymers are some of the most promising types of biomaterials; nevertheless, each biomaterial has advantages and disadvantages. Metals and ceramics fail in most applications owing to stress shielding and the emission of wear debris; ongoing research is being carried out to find a remedy to these unfavorable responses. Recent research found that polymers and composites based on polymers are significant alternative materials for artificial joints. With growing research and several biomaterials, recent reviews lag in effectively addressing hip implant materials' individual mechanical, tribological, and physiological behaviors. This Review comprehensively investigates the historical evolution of artificial hip replacement procedures and related biomaterials' mechanical, tribological, and biological characteristics. In addition, the most recent advances are also discussed to stimulate and guide future researchers as they seek more effective methods and synthesis of innovative biomaterials for hip arthroplasty application.

Improved dynamics of DC bus control with a zig-zag transformer for bipolar DC distribution systems

Improved dynamics of DC bus control with a zig-zag transformer for bipolar DC distribution systems

Dynamic Analysis of VSC-HVDC System with Disturbances in the Adjacent AC Networks

VSC-HVDC systems are widely used to integrate wind farms, asynchronous generations and networks operating at different frequencies. The Multi-terminal (MT) and multi-fed (MF) HVDC’s are the system mainly constituted of VSC’s, to integrate renewable sources and transmitting bulk power to conventional AC grids. A sudden change in the steady state even in adjacent networks may create severe disturbances in the operation of such HVDC systems. The disturbances in AC or DC networks directly influence the performance of systems, particularly in MT-HVDC and MF-HVDC systems. However, the HVDC systems are known for their intelligent control in modulating operational states as and when required. This paper presents the dynamic analysis of MF-HVDC system due to load changes, faults and other disturbances in the adjacent AC networks. The result indicates that VSC-HVDC provides decoupled control of active and reactive power with capability in adjusting operational mode during various minor and major disturbances. Based on the results obtained, the paper proposed a novel sensitivity factor indicating percentage coupling among various line parameters during disturbances. Furthermore, the VSC’s injects harmonic signals on both AC and DC sides of HVDC system. These harmonics voltage or currents signals may get amplified to a dangerously high magnitude at resonance frequencies. Thus, the frequency characteristics of different subsystems are also analyzed using FFT. A ±100 kV, 200 MW bipolar MF VSC-HVDC test systems is used to simulated the results in MATLAB/Simulink software.

Fault diagnosis in bipolar HVDC systems based on traveling wave theory by monitoring data from one terminal

This paper proposes a method for detecting, classifying and locating incident faults on transmission line (TL) of a bipolar HVDC system. This method is based on the traveling waves theory and uses the redundant discrete wavelet transform to filter voltage signals monitored at only one system terminal. The model represents the Brazilian HVDC system of the Madeira River, which is simulated in the Alternative Transient Program (ATP). Different fault scenarios are analyzed, being generated by varying type, resistance and fault location. Moreover, in order to make the simulation more realistic, the TL is modeled based on frequency dependent parameters. Thereby, the impacts of line parameter uncertainties and transient attenuation on the proposed method are analyzed. From the obtained results, it is concluded that the method correctly detects all fault types through the use of a self-adaptive detection threshold. Furthermore, it is verified that the self-adaptive threshold detects the fault times instants with an efficiency superior to the fixed threshold. In the classification step, all faults were correctly classified through rules elaborated based on the voltage variation level. Finally, the total average errors of fault location represents only 0.047% of the TL extension. Moreover, it is verified that fault location errors for pole:pole faults were inferior to those obtained for pole:ground faults, being the efficiency of the method inversely proportional to the fault resistance.