Search

Objectives Yttrium-90 transarterial radioembolization (TARE) is a safe, effective modality of locoregional therapy for intermediate and advanced-stage hepatocellular carcinoma (HCC). We aim to identify novel predictors of important outcomes of TARE therapy. Methods A single-center retrospective study of 166 patients treated with TARE for HCC at Mayo Clinic Rochester between 2005-2015 and followed until December 2017. Multivariate logistic and stepwise regression analysis models were used to identify variables associated with overall survival (OS) and progression-free survival (PFS). Results The median OS and the median PFS were12.9 (95% CI: 11.0-17.3), and 8 months (95% CI: 6-11), respectively. Macrovascular invasion (HR: 1.9 [1.3-2.8]), Child-Pugh score (CPS) B or C vs. A (HR: 1.8 [1.2-2.7]), Eastern Cooperative Oncology Group Performance status (ECOG-PS) 2 or 1 vs. 0 (HR: 1.6 [1.1-2.4]) and activity (A) of administered radiation dose (HR: 1.005[1.00-1.010), independently correlated with poorer OS. Infiltrative HCC (HR: 2.4 [1.3-4.5), macrovascular invasion (HR: 1.6 [1.1-2.7]), and high activity of administered radiation dose (HR: 1.005 [1.00-1.010) were associated with worse PFS. Conclusion In HCC patients treated with TARE; macrovascular invasion, the activity of radiation dose, CPS, ECOG-PS, and infiltrative HCC predict OS and PFS.

Chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are known risk factors for liver disease, cirrhosis and hepatocellular carcinoma (HCC). There is substantial global variation in HBV and HCV prevalence resulting in variations in cirrhosis and HCC. We previously reported high prevalence of HBV and HCV infections in Somali immigrants seen at an academic medical center in Minnesota.To determine the prevalence of chronic viral hepatitis in Somali immigrants in Minnesota through a community-based screening program.We conducted a prospective community-based participatory research study in the Somali community in Minnesota in partnership with community advisory boards, community clinics and local mosques between November 2010 and December 2015 (data was analyzed in 2020). Serum was tested for hepatitis B surface antigen, hepatitis B core antibody, hepatitis B surface antibody and anti-HCV antibody.Of 779 participants, 15.4% tested positive for chronic HBV infection, 50.2% for prior exposure to HBV and 7.6% for chronic HCV infection. Calculated age-adjusted frequencies in males and females for chronic HBV were 12.5% and 11.6%; for prior exposure to HBV were 44.8% and 41.3%; and for chronic HCV were 6.7% and 5.7%, respectively. Seven participants developed incident HCC during follow up.Chronic HBV and HCV are major risk factors for liver disease and HCC among Somali immigrants, with prevalence of both infections substantially higher than in the general United States population. Community-based screening is essential for identifying and providing health education and linkage to care for diagnosed patients.

In this paper, a virtual-flux finite control set model predictive control (MPC) strategy for dual three-phase interior permanent magnet synchronous motors (DTP-IPMSM) is proposed. The technique is based on the conventional predictive current control, but it maps the measured variables into a virtual- flux domain, thus simplifying the prediction stage. The technique uses a flux-based cost function to track the estimated reference flux. The flux tracking cancels out to guarantee an improved current tracking, and thus, a better torque ripple. The proposed technique is validated through simulation of a 100 kW DTP- IPMSM in Matlab/Simulink. Results evidenced a reduced current control error, thus improving the torque tracking up to 38.9 % when compared to the conventional inductance based model predictive control.

This paper presents an efficiency evaluation of two six-phase inverter topologies for automotive applications: voltage source inverter (VSI) and nine-switch inverter (NSI). Their efficiency is studied for electric powertrains rated at 400 V and 800 V, and using silicon carbide (SiC) MOSFETs rated at 650 V and 1200 V operating at a switching frequency of 30 kHz. Prior to efficiency evaluation, a thorough analysis on the total device count required for 100 kW design is investigated for both topologies. It is found that NSI enjoys a superior efficiency when compared to six-phase VSI, at the expense of increased total device count.

This paper proposes an adaptive voltage regulation (VR) flux-weakening (FW) control technique for dual three-phase (DTP) permanent magnet synchronous machine (PMSM) drives. Firstly, a small-signal model is developed to demonstrate the need of gain adaptation in order to maintain the controller bandwidth. Moreover, the small-signal model serves as a tuning tool for the FW proportional-integral (PI) controller. Then, the proposed adaptive controller is implemented and tested on a 100 kW DTP-PMSM drive. Simulation results demonstrate an improved drive performance at high speeds when benchmarked against non-adaptive controllers. Furthermore, the adaptive controller offers an extended speed range.

This paper proposes a non-parametric auto-tuning methodology for flux weakening (FW) controller tuning, with specifications on phase margin of the voltage regulation (VR) FW control loop, using the modified relay feedback test (MRFT). Unlike proposed small-signal models in the literature that utilize linearized plant models, the MRFT can be carried out online on the drive system to deduce PI parameters without a prior knowledge of machine parameters. This is particularly important since machine parameters, such as stator resistance and inductances, can deviate when operated at higher temperatures. Furthermore, the VR-FW loop exhibit a varying static gain that must be accounted for when operating the machine in deep FW region. Simulation results demonstrates a superior and robust drive performance in deep FW region when compared to adaptive FW control based on machine parameters.

This paper presents an efficiency evaluation of three silicon carbide (SiC) inverter topologies: two-level (2L) voltage source inverter (VSI), 3L neutral-point clamped (NPC), and 3L T-type inverter. Their efficiency is evaluated for powertrains rated at 400 V and 800 V, and using SiC MOSFET devices rated at 650 V and 1200 V operating at a switching frequency of 30 kHz. Firstly, the efficiency is evaluated at different operating load currents, on a per-unit scale. Secondly, the efficiency curves are mapped into torque-speed 2D maps of 120 kW interior permanent magnet (IPM) motors. Thirdly, the resulting efficiency maps are employed in an electric vehicle (EV) model, in order to study the performance of the three inverters on standard drive cycles. At the vehicle level, the energy consumption of the vehicle using the studied inverters is analyzed. It is found that 3L SiC-based inverters are most competitive in the 800 V powertrain. When compared to VSI, NPC and T-type offer 0.6% and 1.2% energy consumption savings. In 400 V, only T-type enjoys 0.9% energy savings over VSI.

This paper proposes a modified current source inverter (CSI) fed drive for electric vehicle (EV) applications. This topology utilizes an additional seventh switch, called CSI7, to significantly reduce commutation glitches of the traditional CSI. More importantly, with a proper pulsewidth modulation (PWM) scheme, the CSI7 topology yields reduced conduction losses, and thus improves the inverter efficiency. In this paper, the CSI7 topology is employed in an interior permanent magnet synchronous machine (IPMSM) drive. The drive includes a prestage dc-dc converter that acts as a controlled current source for the CSI7. Accordingly, a simple field-oriented control (FOC), utilizing a single current sensor, is proposed herein. Simulation results demonstrate a significant reduction in commutation glitches in output phase voltages and improved inverter efficiency. Both motoring and regenerating braking modes of the CSI7-fed drive are presented at various operating conditions. The proposed CSI7-fed IPMSM drive can be very attractive for EVs owing to its small battery requirement, thanks to its voltage boosting capability.

Patients with chronic pancreatitis (CP) are at a higher risk of developing pancreatic adenocarcinoma compared the general population with an estimated 5% risk of developing pancreatic cancer in 20 years. Endoscopic ultrasound fine needle aspiration (EUS-FNA) of solid pancreatic lesions (SPL) has an excellent sensitivity (85-90%) and specificity (98-100%) for diagnosing pancreatic malignancy. However, data on the performance characteristics of EUS-FNA in CP are mixed.In this systematic review and meta-analysis, we aim to examine data from published studies on the diagnostic performance of EUS-FNA in detecting pancreatic malignancy in CP.We conducted a comprehensive search of MEDLINE, Cochrane, EMBASE, Scopus databases for studies published in English language that reported performance characteristics of EUS-FNA for SPL up to November 2020. Two reviewers independently conducted screening, full text review and data extraction according to the PRISMA guidelines. Quality of included studies was assessed using the risk of bias in non-randomized studies of interventions (ROBINS-I) tool. The parameters of interest were sensitivity, specificity, negative, and positive likelihood ratios. Cochran Q test and I statistics were used to determine the between-study heterogeneity. Funnel plots were used to describe publication bias.A total of 6753 studies were identified on initial search. Studies that reported EUS-FNA of cystic pancreas lesions were excluded. Eight studies met the inclusion criteria. Seven studies were retrospective, and one was prospective. A total of 593 patients with CP underwent EUS-FNA for SPL. The pooled sensitivity of EUS-FNA was 65% (95% CI 52.6-75.6%, IThis pooled meta-analysis shows a low sensitivity of EUS-FNA in diagnosing malignancy in CP patients with SPL in comparison to patients without CP. Modalities such as EUS-fine needle biopsy have high sensitivity and specificity for diagnosing pancreatic cancer and should be considered in patients with CP and suspected pancreatic malignancy.

Silicon Carbide (SiC) devices have been increasingly adopted in many applications owing to their many advantages when compared their silicon (Si) counterparts. On a material level, the crystal structure, commonly known as polytype, dictates many features of the SiC device at the device level. Hence, in-depth understanding of the different polytypes of SiC is imperative for the proper selection of the SiC polytype, depending on the desired operational envelope of the device. In this paper, the crystallography of the major polytypes as well as their electrical properties are reviewed. A material physical model is also presented. Based on the available literature, a comparison of the different polytypes is made at the device level, using Schottky barrier diodes (SBDs) and MOSFETs. Based on the surveyed studies, it can be generalized that the hexagonal polytypes (i.e. 4H and 6H) are the polytype of choice for SiC devices with breakdown voltages above 2.5 kV, owing to their high electron mobility and low conduction losses. On the other hand, the cubic (3C) polytype can yield lower conduction losses for SiC devices with lower breakdown voltages.

Controller tuning of voltage source converter (VSC), using voltage oriented control (VOC), has a significant impact on the system stability against disturbances. To this end, optimization algorithms are sought in order to achieve optimum dynamic performance. Such algorithms are normally applied to numerical simulators that are time-intensive, which hinders the design process. This paper proposes, for the first time, space mapping (SM) optimization algorithm for controller tuning in a grid-connected VSC system. SM is a surrogate-based optimizer that utilizes a ‘coarse’ model that is less accurate, yet extremely fast, to guide the optimization of the numerical, time-intensive ‘fine’ model. The development and employment of both models are presented in this study. Subsequently, the accuracy and efficiency of the SM algorithm are assessed by simulations. It is found that SM optimization algorithm can return a quasi-optimum solution in less than half the time taken by optimizing the fine model with adequate accuracy.

Controller tuning is deemed to be critical when dealing with the voltage oriented control (VOC) as it ultimately defines the system performance. This paper contributes to the tuning issue associated with VOC in three key points. Firstly, an algebraic solution (i.e. PI-parameters) based on the first-order-plus-time-delay (FOPTD) approximations of the plant dynamics is developed, along with approximating relationships and methodology. Secondly, a non-linear multi-criteria optimization algorithm, with PI-controller parameters being the decision variables, is developed in order to achieve the optimum disturbance rejection. The cost function employs a weighted-sum criterion to account for two sources of disturbances: grid voltage sag/dip and load current disturbances, which affect the regulated dc voltage. Simulation results suggest a quasi-optimum system performance, in terms of minimum integral time absolute of the error (ITAE) performance index of the dc-bus voltage, using the FOPTD tuning parameters. Hence, the developed FOPTD approximations demonstrate an accurate linear approximation. Thirdly and consequently, analytic tuning rules for the PI-controllers are proposed. The proposed rules provide quasi-optimum PI-parameters by direct substitution of system parameters in the tuning formulae, rather than solving complex algebraic equations as in the FOPTD tuning approach. The obtained results are verified experimentally.

The presence of undesirable solid contaminants can have adverse effects on the integrity of gas pipelines. One of the most common contaminants in such pipelines is black powder. Developing predictive maintenance protocols, including online quality monitoring, is imperative to ensure the on-spec supply of gas to customers and to avoid severe consequences such as pipeline blockage. In this paper, a microwave sensing system that utilizes resonant probes for the detection and monitoring of solid contaminants, is presented. The proposed probe is essentially a conventional circular waveguide with a resonant iris structure attached to the aperture. The concentration of solid contaminants in gas flows is assessed by analyzing the scattering parameters of transmitting/receiving probes at a resonant frequency, which are coupled non-intrusively to the pipeline. 3D electromagnetic simulations are performed for sensitivity analysis of the proposed sensing system. Furthermore, the detection and evaluation of solid contaminants are experimentally validated using air/sand flow in a 51 mm inner diameter pipeline. The efficacy of the proposed system is demonstrated following the successful detection of solid contaminants in the dual-phase flow. Additionally, it is also illustrated that inclusion of a resonating iris structure in the aperture of the circular waveguide results in enhanced sensitivity when compared to a non-resonant counterpart.

Accurate velocity measurement of solid particulates in multi-phase flows is critical for many industrial processes. This paper presents a non-intrusive microwave velocimeter for solid particulates in gas/solid flows. The proposed velocimeter is founded upon the cross-correlation principle while operating at 24 GHz. By having two sensors 5 cm apart, the velocity of the particulates is deduced from the relative delay in the reflected waves received by both sensors. The deployed sensor is a hermetically sealed circular waveguide with a custom-made TEM-to-TE 11 mode transition. The proposed system is tested experimentally on a 1 inch PVC process pipe. The measurements drawn from the proposed system are benchmarked against a high-speed camera measurements acquired downstream of the microwave velocimeter. Experimental results demonstrate a promising performance that can be further enhanced for real-time velocity measurement in industrial processes.

Switched reluctance motor (SRM) has various advantages which makes it an excellent candidate for many applications; nevertheless, its main drawback is torque ripples. This paper aims to enhance the SRM operation by reducing its torque ripples without the need for expensive and sophisticated physical changes in the motor materials or design. The SRM converter firing angles are optimized to produce the lowest possible torque ripples. The response surface method (RSM) is used to obtain the SRM optimization function that relates torque ripples with firing angles, and grey wolf optimizer (GWO) is used to minimize this function. The objective function convergence speed using the proposed GWO is compared with genetic algorithm (GA), and it is found to be faster than GA. Simulation and experimental results show the effectiveness of the proposed approach in enhancing SRM operation by providing the SRM converter firing angles that result the minimum feasible torque ripples.

Screw conveyors find vast application in material/powder feeding systems. This paper presents a technology development by introducing a compact and simple design of a screw conveyor system for material feeding. The herein developed system serves the purpose of attaining controlled material feeding rate of solid particles in a flow loop. The screw conveyor is driven by a stepper motor whose step size is predefined. Calibration tests are carried out in order to obtain an accurate relationship between the step size and material feeding. Then, open-loop feeding control is achieved in terms of accurate step size rate. Experimental results demonstrate reliable system characteristics.

Black Powder (BP) poses a serious threat to the integrity and operation of natural gas transmission networks worldwide. While BP corrective and preventive remedies have been proposed in the past, real-time detection and quantification of BP in natural gas flows using a viable technology is yet to be addressed. Real-time monitoring of BP is imperative not only to ensure on-spec supply of sales gas, but also to facilitate maintenance decisions and assess the efficacy of in-line filters. In this paper, an industrial-grade BP detection device (BPDD) capable of measuring the total suspended solids (TSS) in real-time is demonstrated. The proposed device is based on measurements of microwave signals transmitted through a pipe section as solids traverse in the gas flow using a custom-made transceiver and in-situ probes. The BPDD is extensively tested on sales gas pipelines in field conditions, whereby high sensitivity is verified. Concentration measurements of the BPDD is benchmarked against a TSS analysis conducted as part of isokinetic sampling of the gas flow. The reported measurement error using the BPDD is less than 7%. Hence, the proposed device is deemed a valuable asset to flow assurance in the oil & gas industry.

Voltage source converter (VSC) plays a major role in the AC/DC interconnection. Its control stands as a significant issue as it determines the stability and performance of the system. Therefore, utilization of a control algorithm that can robustly reject disturbances is highly appreciated. This paper proposes a new approach for PI-parameters selection, used in the decoupled dq-vector control scheme, based on first-order-plus-time-delay (FOPTD) models, for which analytical formulas for optimal controller design/tuning can be obtained. Furthermore, a non-linear optimization algorithm is developed in order to achieve the optimum disturbance rejection in terms of minimizing the integral time absolute of the error (ITAE) performance index. The cost function employs a weighted-sum criterion for two sources of disturbances, namely AC input voltage fluctuation and load disturbances, which may affect the regulated voltage. Simulation results demonstrate a very similar system performance using the FOPTD tuning parameters compared to the optimum ones where both yield a robust system against disturbances. The obtained results are also verified experimentally.

This paper reviews two renewable energy systems; wind and photovoltaic (PV) systems. The common debate between the two of them is to conclude which one is better, in terms of cost and efficiency. Therefore, comparative study, in terms of cost and efficiency, is attempted. Regarding total cost of both, wind and PV systems, many parameters must be taken into consideration such as availability of energy (either wind or solar), operation and maintenance, availability of costumers, political influence, and the components used in building the system. The main components and parameters that play major role in determining the overall efficiency of wind systems are the wind turbine generator (WTG), gearbox and control technologies such as power, and speed control. On the other hand, in grid-connected PV systems (GCPVS), converter architecture along with maximum power point tracking (MPPT) algorithm and inverter topologies are the issues that affects the efficiency significantly. Cost and efficiency analyses of both systems have been carried out based on the statistics available till today and would be useful in the progress of renewable energy penetration throughout the world.