Phase Angle Measurements Research Articles

Comparative Effects of Sleeve Gastrectomy vs. Roux-en-Y Gastric Bypass on Phase Angle and Bioelectrical Impedance Analysis Measures: A Systematic Review and Meta-Analysis

Background/Objectives: The objective of this meta-analysis was to determine the impact of bariatric surgery on phase angle (PhA) and other bioimpedance measures among adults with obesity, comparing the effects of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG). Methods: A systematic review and meta-analysis were conducted following PRISMA guidelines, including studies up to May 2024 from MEDLINE, Scopus, Cochrane Library, and Web of Science. Eligible studies assessed PhA changes pre- and post-bariatric surgery in adults with BMI ≥ 30 kg/m2. Data on PhA, fat mass (FM), fat-free mass (FFM), body cell mass (BCM), weight, and BMI were extracted and analyzed. Results: Thirteen studies with a total of 1124 patients were included. Significant PhA reductions were observed at 6 months post-surgery (effect size: −1.00; 95% CI: −1.11 to −0.89; p < 0.001), with a more substantial reduction in RYGB patients compared to SG. FM and FFM decreased significantly at 12 months (FM: −27.58; 95% CI: −32.58 to −22.57; p < 0.001; FFM: −10.51; 95% CI: −12.81 to −8.94; p < 0.001). Weight and BMI showed marked reductions at 6 months (Weight: −31.42 kg; 95% CI: −37.28 to −25.26; p < 0.001; BMI: −11.39; 95% CI: −12.60 to −10.18; p < 0.001), with sustained decreases at 12 and 24 months. Conclusions: Bariatric surgery significantly reduces PhA, FM, FFM, weight, and BMI, with initial greater impacts observed in RYGB compared to SG. PhA shows potential as a marker for monitoring post-surgical recovery and nutritional status. Further long-term studies and standardized measurement protocols are recommended to optimize patient management.

Dynamic Unbalance Identification in Steady-State Rotating Machinery: A Hybrid Methodology Integrating Physical and Data-Driven Techniques

Rotating machinery plays a strategic role in key industrial sectors, making its analysis a subject of great interest for both academia and industry. Effective maintenance planning for this equipment is essential for asset management and for meeting current industrial requirements. To address this demand, this work presents a novel unbalance identification approach based on a digital representation of a rotating machine's dynamic behavior in relation to the development of specific faults. A hybrid methodology is proposed, integrating Finite Element Modeling, a Kalman Filter for parameter estimation, and Referenced Moving Window Principal Component Analysis. This Principal Component Analysis extension enhances vibration pattern recognition, enabling accurate fault quantification directly from slight changes in the system's steady-state behavior. The methodology uniquely eliminates the need for phase angle measurements, facilitating continuous monitoring of unbalance progression in steady-state conditions. Two case studies demonstrate the methodology's potential: one utilizing synthetic data from a Floating Production Storage and Offloading centrifugal compressor unit, and the other based on real data from a hydroelectric turbine-generator. These studies illustrate the integration of computational modeling, data-driven analysis, and monitored vibration data, achieving robust and accurate unbalance identification. This approach provides valuable insights into current capabilities and opens promising pathways for future applications, particularly in the digital twin domain for rotating machinery.

A Joint Estimation Method of Distribution Network Topology and Line Parameters Based on Power Flow Graph Convolutional Networks

Accurate identification of network topology and line parameters is essential for effective management of distribution systems. An innovative joint estimation method for distribution network topology and line parameters is presented, utilizing a power flow graph convolutional network (PFGCN). This approach addresses the limitations of traditional methods that rely on costly voltage phase angle measurements. The node correlation principle is applied to construct a node correlation matrix, and a minimum distance iteration algorithm is proposed to generate candidate topologies, which serve as graph inputs for the parameter estimation model. Based on the topological dependencies and convolutional properties of AC power flow equations, a PFGCN model is designed for line parameter estimation. Parameter refinement is achieved through an alternating iterative process of pseudo-trend calculation and neural network training. Training convergence and loss function values are used as feedback to filter and validate candidate topologies, enabling precise joint estimation of both topologies and parameters. The proposed method’s accuracy, transferability, and robustness are demonstrated through experiments on the IEEE-33 and modified IEEE-69 distribution systems. Multiple metrics, including MAPE, IAE, MAE, and R2, highlight the proposed method’s advantages over Adaptive Ridge Regression (ARR). In the C33 scenario, the proposed method achieves MAPEs of 4.6% for g and 5.7% for b, outperforming the ARR method with MAPEs of 7.1% and 7.9%, respectively. Similarly, in the IC69 scenario, the proposed method records MAPEs of 3.0% for g and 5.9% for b, surpassing the ARR method’s 5.1% and 8.3%.

Design, development and multi-scenario application of portable multifunctional test master based on μM-PMU: The case study of Lingang new City Grid, Shanghai

With the large-scale access of new energy generation and electric vehicle charging piles to the grids, power generation and loads are characterized by random fluctuations and intermittency, which affect the stable operation of the distribution network. μM-PMU is capable of realizing the dynamic process monitoring of the grids. In order to solve the function and performance testing problems of multiple application scenarios of μM-PMU, this thesis develops a portable master station based on synchronous phasor measurement system to realize zero drift, voltage amplitude measurement accuracy, voltage phase angle accuracy, current amplitude measurement accuracy, current phase angle measurement accuracy, frequency measurement accuracy, voltage amplitude change with frequency accuracy, and voltage phase angle change with frequency accuracy, Accuracy of current amplitude with frequency change, accuracy of current phase angle with frequency change, active power accuracy, reactive power accuracy, amplitude step response, phase angle step response, frequency step response, a total of 15 test items. It can automatically calculate test results and generate test reports according to different equipment models, reducing the mistakes and calculation errors that may be caused by manually recording test data and improving the accuracy of test results and calculation precision.

Research on Parameter Correction of Distribution Network Model Based on CIM Model and Measurement Data

The construction of an energy distribution network can improve the system’s ability to absorb new energy, and its stable and efficient operation has become more and more important. The security and stability analysis of a distribution network needs accurate distribution network model parameters as support. At present, the installation of PMU equipment in China’s distribution network synchronous phase angle measurement unit is limited, which brings challenges to the parameter correction of the distribution network. In this paper, an automatic correction algorithm of distribution network parameters based on the CIM model and measurement data is proposed for the distribution network system without PMU. Firstly, the distribution network topology construction technology based on XML files and key fields of the distribution network is proposed, and the non/small impedance devices (such as switches) are merged and reduced. The breadth-first traversal algorithm is used to verify the connectivity of the constructed topology. Then, based on the topology construction and the least squares method, an iterative parameter correction technique is constructed. Finally, the accuracy and effectiveness of the proposed algorithm are verified in a standard IEEE 33-bus system distribution network and an example of the China Southern Power Grid. The topology connections constructed based on the CIM model have significantly enhanced the efficiency of parameter correction.

Portable bioimpedance analyzer for remote body composition monitoring: A clinical investigation under controlled conditions

ObjectivesIn an era when telemedicine is becoming increasingly essential, the development and validation of miniaturized Bioelectrical Impedance Analysis (BIA) devices for accurate and reliable body composition assessment is crucial. This study investigates the BIA Metadieta, a novel miniaturized BIA device, by comparing its performance with that of standard hospital BIA equipment across a diverse demographic. The aim is to enhance remote health monitoring by integrating compact and efficient technology into routine healthcare practices. MethodsA cross-sectional observational study was conducted with 154 participants from the Clinical Nutrition Unit. The study compared resistance (R), reactance (Xc), and phase angle (PhA) measurements obtained from the BIA Metadieta device and a traditional hospital-based BIA device. ResultsAnalysis revealed strong positive correlations between the BIA Metadieta and the hospital-based device for R (r = 0.988, P < 0.001), Xc (r = 0.946, P < 0.001), and PhA (r = 0.929, P < 0.001), indicating the miniaturized device's high accuracy and reliability. These correlations were consistent across different genders and BMI categories, demonstrating the device's versatility. ConclusionsThe BIA Metadieta device, with its miniaturized form factor, represents a significant step forward in the field of remote health monitoring, providing a reliable, accurate, and accessible means for assessing body composition.

The method for calculating phase angle between exciter force of vibration exciter and roller displacement

Introduction. In the process of soil compaction it is important to have information about the current density of the layer, as it enables to quickly adjust the load on the compacted material. The field methods of compaction quality assessment do not cope with this task, as they make point estimation within the pavement area. Therefore, continuous compaction monitoring systems installed on vibratory road rollers are becoming increasingly common. The systems developed by BOMAG and AMMANN require, among other things, the phase angle between the exciter force and the roller movement to calculate the compaction quality index. The phase angle is determined by the unbalance position sensor, which is very labor-intensive. In addition, continuous compaction monitoring systems include an accelerometer. The purpose of this paper is to develop an indirect method for calculating the phase angle from accelerometer readings.The method of research. In order to achieve the purpose of the work, a roller-soil single-mass model in a typical mode for vibratory rollers (periodic loss of contact) has been studied. As a result of modeling it has been found that the reaction of the compacted material has the main influence on the vertical component of a roller acceleration and practically does not affect the horizontal component. This is confirmed by the experimental data.Results. The phase angle can be determined by mutual correlation of the horizontal and vertical acceleration signals of the roller obtained with the accelerometer.Conclusion. The study proposes a new method of calculating the phase angle between the exciter force and the roller displacement, which eliminates the direct measurement of this angle. The calculation of the angle is based on the readings of a two-axis accelerometer installed on the road roller. The proposed method enables to simplify the system of continuous compaction control and reduce the labor intensity of phase angle measurement.

Study on the Application of Kramers-Kronig Relation for Polyurethane Mixture.

Polyurethane (PU) mixture, which is a new pavement mixture, exhibits different dynamic properties compared to a hot-mixed asphalt mixture (HMA). This paper analyzed whether the Kramers-Kronig (K-K) relation and thermorheologically simple properties applied to the PU mixture. Based on the results, the PU mixture exhibited thermorheologically simple properties within the test conditions. The time-temperature superposition principle (TTSP) was applicable for the PU mixture to construct a dynamic modulus master curve using the standard logistic sigmoidal (SLS) model, the generalized logistic sigmoidal (GLS) model, and the Havriliak-Negami (HN) model. The Hilbert integral transformed SLS and GLS models for the phase angle can accurately fit the measured phase angle data with newly fitted shift factors and predict the phase angle within the viscoelastic range. The core-core and black space diagrams both displayed single continuous smooth curves, which can be utilized to characterize the viscoelastic property of the PU mixture. The K-K relation is applicable for the PU mixture to obtain the phase angle master curve model, storage modulus, and loss modulus from the complex modulus test results with the test temperatures and loading frequencies. The phase angle of the PU mixture at extremely high or low test temperatures cannot be derived from the dynamic modulus data.

#258 Does muscle quality affect the accuracy of eGFR?

Abstract Background and Aims Appropriate assessment of glomerular filtration rate (GFR) is the key to manage chronic kidney disease (CKD). The clearance of exogenous tracers, such as inulin and iothalamate, is the best way to measure GFR. However, because this approach is time-consuming and expensive, it is only applied in a specific condition. Several equations to estimate GFR, including Cockcroft-Gault, MDRD, and CKD-EPI, can be applied with easily obtained information about patient's age, sex, and serum creatinine as an endogenous marker, and are used in clinical practice. Because serum creatinine is considerably influenced by muscle mass, these equations still have limitations. Therefore, estimated GFR (eGFR) should be carefully interpreted in patients with sarcopenia; renal function in patients with sarcopenia are prone to be overestimated. Recently, the importance of muscle quality as well as muscle mass has been emphasized in assessing sarcopenia. Muscle quality can be assessed by measuring phase angle (PhA) using bioelectrical impedance analysis (BIA) and is associated with poor prognosis in patients with heart failure. Although muscle quality potentially has an impact on creatinine generation, the association between muscle quality and GFR is unknown. The aim of this study was to evaluate the influence of muscle quality assessed by PhA on the accuracy of eGFR. Method In this single-center and cross-sectional study, 112 patients with CKD were enrolled between April 2021 and October 2022. Among these, four patients diagnosed as acute kidney injury were excluded from the analysis. Renal functions were evaluated in two approaches by calculating eGFR using an equation for Japanese and more precisely by CCr × 0.715 mL/min using 24-h urine. PhA was measured using MC-780A-N (TANITA), where the smaller value indicates worsened muscle quality. The renal function overestimation index (ROI) was defined as eGFR / CCr × 0.715 and the subjects were classified as i) underestimated group (group U); ROI ≦ 1, ii) overestimated group (group O); ROI &amp;gt; 1. The correlations of ROI to age, body mass index (BMI), skeletal muscle mass (SMM), eGFR and PhA were analyzed using Spearman's rank correlation coefficient. To determine the influencing factor for ROI, a multiple linear regression analysis including age, gender, BMI, SMM, and PhA as explanatory variables were performed. Furthermore, the cut-off value of PhA for overestimation of renal function was determined. Results The patient's characteristics were 56% male, 69.5 (26-89) years old, and eGFR 38.1 (3.8-114.3) mL/min/1.73 m2. PhA was significantly lower in the group O compared to the group U (Fig. 1). ROI correlated with age, BMI, SMM and PhA (age; r = 0.502 and p = 0.007, BMI; r = −0.558 and p = 0.002, SMM; r = −0.773 and p &amp;lt; 0.001, eGFR; r = −0.205 and p = 0.295, PhA: r = −0.812 and p &amp;lt; 0.001). Furthermore, multiple regression analysis showed that PhA independently affected ROI (Age; Stdβ = 0.108 and p = 0.464, Sex; Stdβ = 0.045 and p = 0.773, BMI; Stdβ = −0.109 and p = 0.491, SMM; Stdβ = −0.281 and p = 0.307, PhA; Stdβ = −0.49 and p = 0.032). The receiver operating characteristic (ROC) curve of PhA for differentiating overestimate and underestimate showed an area under the curve of 0.960. The cut-off value of PhA was determined at 5.00 with a sensitivity of 94.1% and a specificity of 90.9% (Fig. 2). Conclusion This study demonstrated that PhA independently influences the assessment of renal function by eGFR and that GFR may be overestimated in patient with low muscle quality.

#1848 Body composition and multimorbidity in patients with chronic kidney disease

Abstract Background and Aims Frailty and multimorbidity are increasingly prevalent, particularly in the chronic kidney disease (CKD) population, and they seem to be more pronounced and accelerated in people receiving haemodialysis. We aimed to study the relationship between body composition, frailty and multimorbidity in people with CKD and end stage renal disease (ESRD) on haemodialysis (HD). Method This was a single centre study, involving 42 patients with CKD stage 3 to 5 (pre-dialysis) and 29 patients receiving in-centre haemodialysis. InBody 770 was used to measure body composition using bioelectrical impedance analysis. Multimorbidity of participants were assessed using the simplified Cambridge multimorbidity score. Frailty assessment was performed using the Clinical Frailty Scale. Results Phase angle was lower in later stages of CKD—mean phase angle in CKD stage 3 was 5.28°, stage 4 was 4.44 and stage 5 was 4.13 (p = 0.008). Visceral adiposity correlated with multimorbidity scores but in a multivariate regression analysis (including albumin and visceral fat area) only whole body phase angle independently predicted multimorbidity in CKD stage 4-5 (adjusted R2 for the whole model = 0.47, p = 0.007). In haemodialysis patients, there was no correlation between multimorbidity and phase angle (r = −0.149, p = 0.441). However, there was a significant correlation between frailty score and whole body phase angle in this group (r = −0.559, p = 0.002). In a univariate analysis, age (R2 = 0.2, Beta = 0.045, p = 0.015), albumin (R2 = 0.217, Beta = −0.214, p = 0.009) and skeletal muscle mass (R2 = 0.282, Beta = −0.101, p = 0.003) predicted frailty score in haemodialysis patients. In multivariate regression analysis age, albumin level and skeletal muscle mass continued to independently predict frailty scores in HD patients (adjusted R2 for the whole model = 0.503). Conclusion Phase angle measurement refers to cell membrane integrity and fat-free mass, with higher values suggesting improved cell health. Using body composition measures, in particular phase angle, is a useful measure to predict multimorbidity and frailty in CKD patients. They are quick, accessible and easy to use tools that can be incorporated in clinical practice routinely. The relationship between visceral adiposity and multimorbidity merits further investigation. Preservation of skeletal muscle mass through nutritional and exercise interventions could be a clinical target to reduce frailty in this population.

Effects of Tympanic Membrane Electrodes on Sound Transmission From the Ear Canal to the Middle and Inner Ears.

The first objective of the study was to compare approaches to eardrum electrode insertion as they relate to the likelihood of introducing an acoustic leak between the ear canal and eartip. A common method for placing a tympanic membrane electrode involves securing the electrode in the canal by routing it underneath a foam eartip. This method is hypothesized to result in a slit leak between the canal and foam tip due to the added bulk of the electrode wire. An alternative approach involves creating a bore in the wall of the foam tip that the electrode can be threaded through. This method is hypothesized to reduce the likelihood of a slit leak before the electrode wire is integrated into the foam tip. The second objective of the study was to investigate how sound transmission in the ear is affected by placing an electrode on the eardrum. It was hypothesized that an electrode in contact with the eardrum increases the eardrum's mass, with the potential to reduce sound transmission at high frequencies. Wideband acoustic immittance and distortion product otoacoustic emissions (DPOAEs) were measured in eight human ears. Measurements were completed for five different conditions: (1) baseline with no electrode in the canal, (2) dry electrode in the canal but not touching the eardrum, secured underneath the eartip, (3) dry electrode in the canal not touching the eardrum, secured through a bore in the eartip (subsequent conditions were completed using this method), (4) hydrated electrode in the canal but not touching the eardrum, and (5) hydrated electrode touching the eardrum. To create the bore, a technique was developed in which a needle is heated and pushed through the foam eartip. The electrode is then thread through the bore and advanced slowly by hand until contacting the eardrum. Analysis included comparing absorbance, admittance phase angle, and DPOAE levels between measurement conditions. Comparison of the absorbance and admittance phase angle measurements between the electrode placement methods revealed significantly higher absorbance and lower admittance phase angle from 0.125 to 1 kHz when the electrode is routed under the eartip. Absorbance and admittance phase angle were minimally affected when the electrode was inserted through a bore in the eartip. DPOAE levels across the different conditions showed changes approximating test-retest variability. Upon contacting the eardrum, the absorbance tended to decrease below 1 kHz and increase above 1 kHz. However, changes were within the range of test-retest variability. There was evidence of reduced levels below 1 kHz and increased levels above 1 kHz upon the electrode contacting the eardrum. However, differences between conditions approximated test-retest variability. Routing the eardrum electrode through the foam tip reduces the likelihood of incurring an acoustic leak between the canal walls and eartip, compared with routing the electrode under the eartip. Changes in absorbance and DPOAE levels resulting from electrode contact with the eardrum implicate potential stiffening of eardrum; however, the magnitude of changes suggests minimal effect of the electrode on sound transmission in the ear.

Combined ns pulsed-RF excitation and impedance matching considerations for the production of moderate E/n atmospheric pressure discharges for gas conversion

Sub-breakdown radiofrequency (RF) discharges enabled by a nanosecond (ns) pulse ignition source are studied at atmospheric pressure in a range of gas mixtures from completely inert (in Ar) to completely reactive (in CO2). An electrical characterisation of the continuous wave (CW) RF discharge (13.56 MHz) is performed to determine plasma impedance and plasma power dissipation. Two different measurement methods to electrically characterize the system are described and compared. One method uses in-situ measurements of discharge parameters (voltage, current and the phase angle), and the other method performs ex-situ measurements of the load circuit using a vector network analyser. It was found that RF plasma power deposition depended on the applied RF power as well as the gas mixture composition. Using the in-situ voltage, current and phase angle measurements, plasma power deposition was calculated to be as much as 85% and 76% of the applied RF power for the pure Ar and pure CO2 cases, respectively. A preliminary qualitative assessment of the plasma composition was performed by optical emission spectroscopy, and CO2 conversion by mass spectrometry. CO2 to CO conversions of 11.2% and 5.5% in a 20:80 (CO2:Ar) mixture and in 100% CO2, respectively, were observed. This study demonstrates a RF plasma source for gas conversion applications at atmospheric pressure in a completely reactive gas.

Edible Electronic Components Made from Recycled Food Waste

AbstractA procedure is developed for producing basic electronic components utilizing materials sourced from discarded orange, grapefruit, lemon, apple, banana, potato, and carrot peels. Initially, these materials undergo dehydration, followed by a meticulous pulverization process to obtain fine powder. Natural adhesives like water, honey, sugar, starch, and gelatin are employed to interconnect the materials. Formed substrates are characterized using Scanning Electron Microscopy, Energy Dispersive X‐ray Spectroscopy, and an optical profilometer. Furthermore, the relative permittivity of the materials is determined. Three distinct types of substrates, derived from the aforementioned peels, are crafted in varying dimensions. Substrates measuring 4 cm × 2.5 cm host interdigital capacitive sensors, whereas larger 6 cm × 3.5 cm substrates accommodate inductor‐capacitor (LC) sensors. Each of the six samples undergoes individual dry testing, while LC sensors are additionally tested with the post‐application of artificial saliva and mouthwash liquids. The sensor's characterization involves measurement of impedance and phase angle for all samples. Capacitance is additionally measured for capacitors, and inductance for LC circuits. These assessments are carried out within the frequency range spanning from 1 MHz to 400 MHz. The objective is the development of fully functional electronic components, derived from discarded edible items, fostering sustainable practices, and finding applications in biomedicine.

Bioelectrical impedance vector analysis as an indicator of malnutrition in children under five years with and without pneumonia in Mchinji District, Malawi: An exploratory mixed-methods analysis

Background Bioelectrical impedance vector analysis (BIVA) is a non-invasive approach to assessing body composition and cellular health, which may improve the assessment of nutritional status in sick children. We explored the reliability, clinical utility, and acceptability of BIVA, as an indicator of nutritional status for children under five years with and without pneumonia, in Malawi. Methods We conducted a parallel convergent mixed-methods exploratory study in Mchinji District Hospital, Malawi, in 2017. We recruited a convenience sample of children aged 0–59 months with clinical pneumonia, and without an acute illness. Children had duplicate anthropometric and BIVA measurements taken. BIVA measurements of phase angle were taken of the whole body, and trunk and arm segments. Reliability was assessed by comparing the variability in the two measures, and clinical utility by estimating the association between anthropometry and phase angle using linear regression. Focus group discussions with healthcare workers who had not previously used BIVA instrumentation were conducted to explore acceptability. Results A total of 52 children (24 with pneumonia and 28 healthy) were analysed. The reliability of sequential phase angle measurements was lower than anthropometric measurements, but trunk and arm segments performed better. The largest associations with phase angle were a negative relationship with weight-for-age z-score (WAZ) in children with pneumonia in the trunk segment, and a positive association with WAZ in the full body measurement in healthy children. Healthcare workers in focus group discussions expressed trust in BIVA technology and that it would enable more accurate diagnosis of malnutrition; however, they raised concerns about the sustainability and necessary resources to implement BIVA. Conclusions While healthcare workers were positive towards BIVA as a novel technology, implementation challenges should be expected. The differential direction of association between anthropometry and phase angle for children with pneumonia warrants further investigation.

Bioelectrical Impedance in Premature Newborns and Its Relationship with Diet Therapy in a Neonatal Intensive Care Unit.

(1) Background: To estimate resistance, reactance, and phase angle values among moderate preterm infants and their variation according to neonatal and maternal characteristics and nutritional intake. (2) Methods: This was a cohort that evaluated 43 moderate preterm infants using bioelectrical impedance analysis. The study variables included resistance, reactance, and phase angle measurements, in addition to classification of nutritional intake. (3) Results: Mean resistance was 602.0 ± 118.2 Ω, reactance was 57.2 Ω (IQR = 42.6-65.2), and phase angle was 522° (IQR = 4.1-6.6). Lower resistance values were found in the presence of risky pregnancy (532.2 ± 111.9 Ω vs. 650.9 ± 97.9 Ω, p < 0.001) and lower reactance values, in the presence of harmful maternal lifestyle habits at both the first (p = 0.01) and second assessments (p = 0.01). Eight preterm infants were considered to have insufficient nutritional intake (23.5%); 17, sufficient (50.0%) and 9, partially sufficient (26.5%). There was less reactance among preterm infants with insufficient nutritional intake (p < 0.001). (4) Conclusions: The bioelectrical impedance analysis measurements were within the range of values reported in other studies. There was an association between full diet and adequate nutritional intake with higher resistance values, while a lower reactance value was associated with the presence of risky pregnancy and harmful maternal lifestyle.

Power Calculation Algorithm for Single-Phase Droop-Operated Inverters Considering Nonlinear Loads and unsing n-Order SOGI Filtering

The average active and reactive powers, P and Q, are crucial parameters that have to be calculated when sharing common loads between parallelized droop-operated single-phase inverters. However, the droop method algorithm should employ low-pass filters (LPF) with very low cut-off frequency to minimize the distortion impact in the provide droop amplitude and frequency references. This situation forces the droop control to operate at a very low dynamic velocity, degrading the stability of the parallelized system. For this reason, different solutions had been proposed in literature to increase the droop velocity, but the issues derived from the sharing of nonlinear loads had not been properly considered. This work proposes a novel method to calculate P and Q based on the fundamental components of the inverter's output voltage and current and using the measured phase angle between the output voltage and current. The method is used under normal and highly distorting conditions due to the sharing non-linear loads. The fundamental components are obtained by means of the highly filtering capability provided by n order cascaded second order generalized integrators (nSOGI). The proposed method leads to faster and more accurate P and Q calculations that enhances the droop-method dynamic performance. Simulations are provided to validate the proposal.

Phase Angle as a Nutritional Assessment Method in Patients with Hip Fractures: A Cross-Sectional Study.

Phase angle, which is associated with cellular health, has attracted attention as a noninvasive and objective method for nutritional assessment. However, the association between malnutrition and phase angle in older inpatients with hip fractures has not been reported. Therefore, this study investigated this association in older inpatients (aged ≥65 years) with hip fractures and determined the cutoff phase angle for determining malnutrition. This cross-sectional study retrospectively analyzed the data of 96 inpatients with hip fractures who were hospitalized in rehabilitation units after surgery (male, 29.4%; mean age, 82.4±6.2 years). Nutritional status was assessed using the Geriatric Nutritional Risk Index (GNRI), with malnutrition defined as a GNRI ≥98. Bioelectrical impedance analysis was used to measure phase angles. The phase angle was associated with malnutrition (B=-1.173; odds ratio=0.310; 95% confidence interval 0.58-0.83; p=0.015). The area under the receiver operating characteristic curve was 0.71. The cutoff phase angle for malnutrition was 3.96° (sensitivity=0.85, specificity=0.63). Phase angle could be an indicator of malnutrition in older inpatients with hip fractures. Our findings will help formulate rehabilitation strategies for these patients.

Eddy current analysis for predicting deterioration stages in alumina former radiant coils

The alumina former radiant coil is typically used as a high-temperature material. It is inevitable that the material undergoes deterioration after prolonged use. This deterioration is primarily caused by damage from the service environment and initiates carburization, resulting in a loss of its mechanical properties. Currently, the damage to the materials is only discovered when they are already broken and a precise non-destructive testing method to determine the extent of material deterioration before the damage occurs has not successfully been developed. Therefore, this research aims to study and analyze the deterioration and the causes of damage to alumina former radiant coil materials. Additionally, the study was conducted to establish a relationship between the extent of deterioration and the impedance phase angle using the eddy current test method. The experimental analysis included both as-received and in-service materials of alumina former radiant coil, which consisted of 45 % nickel by weight, 30 % chromium by weight and 4 % alumina by weight. The additional testing methods included microstructure and elemental analysis, deterioration distance measurement and impedance phase angle measurement. The results indicated that the deterioration was primarily caused by damage to the oxidation layer, facilitating the diffusion of carbon and initiating a carburization reaction on the surface of the coil. These factors unavoidably reduced the corrosion resistance of alumina former radiant coil materials. Furthermore, the reduction in chromium content as materials entered the deterioration stage led to increased hardness in the carburization zone and reduced hardness in the oxidation zone. This deterioration caused the material to exhibit ferromagnetic behavior. It was observed that as the area of deterioration increased, the size of the ferromagnetic regions also increased. Resulting in, the eddy current testing results show a variation in the impedance phase angle. Therefore, the relationship can be concluded that the impedance phase angle increases in the counterclockwise direction, corresponding to a greater extent of deterioration. The benefit of this paper is to forecast the level of the severity of deterioration quantitatively when using eddy current testing.

Conditions for Estimation of Sensitivities of Voltage Magnitudes to Complex Power Injections

Voltage phase angle measurements are often unavailable from sensors in distribution networks and transmission network boundaries. Therefore, this paper addresses the conditions for estimating sensitivities of voltage magnitudes with respect to complex (active and reactive) electric power injections based on sensor measurements. These sensitivities represent submatrices of the inverse power flow Jacobian. We extend previous results to show that the sensitivities of a bus voltage magnitude with respect to active power injections are unique and different from those with respect to reactive power. The classical Newton-Raphson power flow model is used to derive a novel representation of bus voltage magnitudes as an underdetermined linear operator of the active and reactive power injections—parameterized by the bus power factors. Two conditions that ensure the existence of unique complex power injections given voltage magnitudes are established for this underdetermined linear system, thereby compressing the solution space. The first is a sufficient condition based on the bus power factors. The second is a necessary and sufficient condition based on the system eigenvalues. We use matrix completion theory to develop estimation methods for recovering sensitivity matrices with varying levels of sensor availability. Simulations verify the results and demonstrate engineering use of the proposed methods.

An Investigation of the Role of Phase Angle in Malnutrition Risk Evaluation and Clinical Outcomes in Patients with Head and Neck or Brain Tumors Undergoing Radiotherapy

This cross-sectional study aimed to investigate the role of bioelectrical impedance analysis (BIA) and phase angle measurement in assessing malnutrition in head and neck (n = 37) and brain (n = 63) tumor patients received radiotherapy. Common nutritional screening and assessment tests were used to identify malnutrition in the patients. Each patient underwent these tests once, along with phase angle measurement. Additionally, inflammation parameters, including neutrophil lymphocyte ratio (NLR), platelet lymphocyte ratio (PLR), and systemic inflammatory index (SII), were calculated. All study results were correlated with the phase angle cutoff point of 5.72°. The phase angle demonstrated significant correlations with subjective global assessment (SGA), mini nutritional assessment (MNA) scores, BIA parameters, nutritional index, NLR, and SII (p < 0.05). Moreover, in head and neck tumor patients, those with higher standardized phase angle values exhibited significantly better two-year overall survival (32.1% vs. 87.5%, p = 0.006). The phase angle measurement is a convenient, noninvasive, and reproducible method that can complement existing tools for assessing malnutrition risk in radiotherapy patients. The significant correlations observed between the phase angle and various nutritional, inflammation markers and prognosis highlight its potential utility. Further studies incorporating a larger patient cohort will be beneficial in establishing a standard phase angle reference value for cancer patients.