Absolute Criterion Research Articles

Neurocysticercosis: unwinding the radiological conundrum

PurposeTo study the distinct imaging characteristics of parenchymal neurocysticercosis (NCC) that aid in distinguishing it from other diseases.Material and methodsTwo hundred fifty patients with NCC were selected based on identification of the scolex. T2 weighted, T1 fluid attenuated inversion recovery (FLAIR), T2 FLAIR, susceptibility weighted imaging, constructive interference in steady state, diffusion weighted imaging, and T1 weighted contrast sequences were performed. The imaging characteristics of the cysts at various stages were analyzed.ResultsThis study presents previously undocumented imaging findings of NCC, establishing absolute, major, and minor criteria for its diagnosis based on magnetic resonance imaging features.ConclusionsUtilizing imaging criteria for diagnosing NCC, as per the study’s sequences, can effectively narrow down differential diagnoses and lead to accurate identification.

Multi-objective decoupling control of thermal management system for PEM fuel cell

Operating temperature is an important factor that affects the efficiency, durability, and safety of proton exchange membrane fuel cells (PEMFC). Thus, a thermal management system is necessary for controlling the appropriate temperature. In this paper, a novel thermal management system based on two-stage utilization of cooling air is first established, whose core characteristic is utilizing the temperature difference between the cooling air leaving the main radiator and the auxiliary radiator. The novel thermal management system can reduce the parasitic power of the fan by 59.27 % and improve the temperature control effect to a certain extent. The traditional feedforward decoupling control based on system identification is first adopted to control the temperature and surpasses dual-PID on all the 5 indexes, which are Integral Absolute Error Criterion (IAE) of temperature difference, IAE of inlet coolant temperature, parasitic power of fan, average overshoot of temperature difference and average overshoot of inlet coolant temperature. The multi-objective decoupling control based on multi-objective optimization is then proposed to further improve the temperature control effect on the basis of traditional feedforward decoupling control. The above 5 indexes are chosen as the optimization objectives, the decoupling coefficients are chosen as the decision variables, and the Pareto set is obtained by NSGAⅡ and NSGAⅢ. The results show that the proposed multi-objective decoupling control has the main advantages as follows: (1) It can provide comprehensive optimization options for different design preferences; (2) It can significantly optimize a certain objective while other objectives are not too extreme; (3) It has the ability to surpass traditional feedforward decoupling control on all the 5 indexes; (4) It does not rely on the system identification.

Nonlinear integral backstepping control based on particle swarm optimization for a grid-connected variable wind energy conversion system during voltage dips

Double-fed induction generator (DFIG) wind turbines connected to the grid are particularly subject to grid problems such as voltage dips. Because of this, it might be challenging to maintain system stability and prevent system disconnections when using a Proportional-Integral (PI) Controller to operate this system. This paper applies the Integral Backstepping Control for the wind power plant system connected to the power grid. The Integral Backstepping is a nonlinear and recursive method that employs the Lyapunov theory to ensure the system's stability. The best selection of gain values for the Lyapunov function guarantees improved system control. These gains are frequently adjusted using the trial-and-error strategy, which is time-consuming and inefficient. This technique becomes more complex when many parameters need to be determined. It also limits the system's performance and restricts this nonlinear approach's advantages. The objective is to apply the particle swarm optimization for computing several constant values of the nonlinear approach by minimizing an integral absolute error criterion index. The weighted sum of errors is employed to solve the multiple objective problems. The proposed controller tracks the maximum power point, maintains the voltage of the DC-Link constant, and controls active and reactive power. The robustness of this method is verified in critical conditions, including system parameter variation and asymmetrical and symmetrical grid faults. The simulation findings highlight the effectiveness and robustness of the combination of Integral Backstepping with Particle Swarm Optimization in terms of reducing response time from 10.6 (ms) to 2 (ms), canceling static error, and improving overshoot compared to the vector control based on PI regulator. Besides, the DC-Link voltage ripples during the asymmetrical grid faults are reduced to ±1 (V) using the suggested controller. The latter can be implemented thanks to advancements in Central Processor Unit technology.

Efficacy of Inspiratory Muscle Training in Patients With Acute Decompensated Heart Failure.

Inspiratory muscle training (IMT) is supported for outpatients with stable chronic heart failure, but its efficacy in hospitalized patients with acute decompensated heart failure (ADHF) remains unclear. The aim of the present study was to clarify IMT efficacy and safety in hospitalized ADHF patients. Patients with inspiratory muscle weakness who underwent cardiac rehabilitation (CR) were analyzed. The control group was historical control data of patients admitted to the same facility. IMT was performed at 30% maximal inspiratory mouth pressure (15 reps/set, 2 sets/day, 5 times/week) with usual CR. Associations between IMT and changes in the 2-min walking distance (2MWD) were assessed using a linear mixed model. In total, 31 and 29 patients in the IMT and control groups (median age 83 [71-88] vs. 86 [77-88] years), respectively, were analyzed. After adjustment for covariates and propensity scores, calculated on the basis of heart-failure severity, frailty, physical function, nutritional status, and inspiratory muscle strength, the 2MWD was significantly higher in the IMT group than in the control group (F=4.697; P=0.035; ∆2MWD; +31.9 vs. +16.3 m). Among 348 IMT sessions, no adverse cardiovascular events or absolute termination criteria were identified. Eleven (3.2%) IMT sessions met relative termination criteria. Adding IMT to usual CR improves the 2MWD, can be safely performed in hospitalized patients with ADHF, and may represent a novel CR approach in patients with ADHF.

Evolution of the doctrine of Zollinger-Ellison syndrome. Literature review

Zollinger–Ellison syndrome (ZES) is a rare pathology that does not have specific clinical manifestations and is not always diagnosed in time. This is attributed to doctors’ insufficient awareness of this pathology and the limited availability of the necessary examination methods. Foreign literary sources on this problem are analysed. Historical data regarding the discovery of this pathology and the origin of the syndrome’s name are provided. The epidemiology of the disease is highlighted. The most characteristic clinical manifestations and possible complications of ZES are described in detail. The characteristic changes in gastric acid production associated with this pathology and their diagnostic value (sensitivity and specificity) are presented. At the same time, indicators of both basal and maximal stimulated gastric acid production are significantly increased. The most important stage in the examination of patients with suspected ZES is the determination of blood gastrin levels. At the same time, it is shown that it is not always possible to make definitive judgements in support of ZES based on gastrin indicators. An absolute criterion in favor of ZES is fasting gastrin values of 1000 pg/ml or more. When gastrin levels are less than this indicator, tests using secretin or calcium gluconate have significant diagnostic value. In these circumstances, tests with secretin or calcium gluconate are mandatory. The information on the possible localization of gastrin, the incidence of malignant transformation, and the mechanism of metastasis is given. Methods of determining gastrin localization, sensitivity, and specificity are described in detail. Based on the findings, a differentiated treatment strategy for patients with ZES is provided. Indications and contraindications for surgical and medical treatment of patients with ZES are given. The prospects of a new treatment direction ‑ the use of targeted radiotherapy ‑ are shown. These patients require constant monitoring by a gastroenterologist and a surgeon and periodically undergo the necessary examinations.

A rare case report on neurocysticercosis – A parasitic disease

Neurocysticercosis is commonly known as cysticercosis, which is the most common parasitic disease of the human nervous system caused by the parasitic tapeworm The development of lesions in the brain and leptomeninges and the consequent onset of symptoms associated with NCC is mainly due to the host immune-inflammatory response. The absolute diagnostic criteria include histological conformation of parasites, evidence of subretinal cysts, and demonstration of the scolex within a cyst. It is treated by a course of steroids or immunosuppressants; for intravascular cysts, endoscopic surgery is the procedure of choice as it is minimally invasive.We present a case of 8-year-old female patient who was admitted to the Neurology ward with the chief complaints of loss of consciousness, involuntary movements, headache, fever, and onset of seizures associated with vomiting. She had a seizure episode at the age of 2 years associated with fever, but no treatment was done. She was not on any past medication and was hemodynamically stable. Her lab investigations of magnetic resonance imaging show infective granuloma in the left parietal lobe with mass effect as described above, suggesting neurocysticercosiswhich should be carefully observed at an early stage. We summarized the case report of neurocysticercosis, its diagnosis, and treatment plan.

Evolving trends in liver transplantation eligibility: A shift toward inclusivity for older adults at a Canadian Transplant Center

Background: The surge of end-stage liver disease among older individuals challenges traditional age-based criteria for liver transplantation (LT), historically capped at 65 years. Our Canadian center shifted away from using chronologic age as an absolute refusal criterion since 2019, enabling those aged 65 years and older to seek LT. This study aimed to investigate temporal trends in the transplant care cascade for patients aged 65 and older at our center, pre- and post-clinical shift. Methods: A retrospective study in a single Canadian transplant center reviewed LT referrals between 2015 and 2023, analyzing proportions of patients aged 65 and above at each stage. Specific intervals, 2015–2018 and 2019–2023, were defined for pre- and post-comparisons. Results: Among the 1,007 LT referrals, 11% (n = 110) were patients aged ≥65 years, with 74% ( n = 81) of them being referred after 2019. From 2015 to 2023, older patient proportions increased at all stages of the transplant care cascade: referrals (7.4% to 12.6%), evaluations (7.6% to 11.4%), waitlisting (5.6% to 15.4%), and transplantations (5.8% to 17.5%). Post-clinical shift, the proportion of older patients referred nearly doubled (7.5% vs 13.7%; p < 0.05), with a similar increase in transplants (5.7% vs. 11.5%; p < 0.05). Conclusions: Removing the age cap increased older patient engagement in the LT care cascade. This emphasizes the crucial role of actively promoting awareness of evolving LT eligibility criteria. Concerted efforts should focus on improving transplantation accessibility in older patients, ensuring age alone does not impede the process.

ThermalTrend: a tool for organising and analysing thermal images

Infrared thermography (IRT), as a non-contact condition monitoring (CM) technique, measures the temperature distribution of machines and components to detect anomalous thermal behaviour. It is usually considered as a complementary technique and nowadays is used in a wide variety of industrial applications. In this paper, two commonly used criteria to assess the condition of machines based on the infrared thermography technique, ie absolute and relative temperature criteria, are represented. Then, the importance of the temperature trend in condition monitoring and fault diagnosis of machines and components is described. The ThermalTrend software, which was developed in the Condition Monitoring Unit, Smelting Department, Sarcheshmeh Copper Complex in Rafsanjan, Iran, is introduced and its most important and unique features are discussed. This software package helps thermographers to organise thermal images and provides the temperature trends of machines and components that are under regular monitoring. Finally, some industrial case studies on the usefulness and applicability of the infrared thermography technique and the ThermalTrend software are reported.

Efficacy and safety of radical cystectomy with ileal conduit for muscle-invasive bladder cancer in the elderly: a multicenter retrospective study.

Radical cystectomy with ileal conduit is the current mainstay of treatment for muscle-invasive bladder cancer and is also a high-risk procedure. Existing studies have limited targeted assessment of the efficacy and safety of this procedure, and the patient population appropriate for this procedure is still poorly defined. We sought to longitudinally analyze differences in the efficacy and safety of radical cystectomy with ileal conduit by age subgroups to assess whether the age factor should be used as an exclusion criterion when selecting this procedure. We retrospectively examined the clinicopathological data of patients with MIBC treated with RC with IC at the Cancer Hospital of Harbin Medical University between February 2014 and October 2023. Additionally, we utilized clinical and pathological data from the SEER database (2000-2020) for external validation of our findings. Patients were categorized into elderly (≥70 years at diagnosis) and non-elderly (<70 years) groups. Statistical analyses included t-tests, non-parametric tests for continuous data, chi-square tests for categorical data, and Kaplan-Meier survival analysis. In this study, 152 patients were included: 119 were categorized as non-elderly and 33 as elderly. For external validation, data from 416 patients in the SEER database were analyzed, with 172 classified as non-elderly and 244 as elderly. The results indicated that elderly patients were more likely to require ICU transfer postoperatively but exhibited a lower incidence of stoma inflammation. Additionally, both the data from our center and the external validation from the SEER database showed a concordance in cancer-specific survival (CSS) between the elderly and non-elderly groups. The efficacy of RC with IC was comparable in both elderly and non-elderly patients. For longitudinal age subgroups, RC with IC for both elderly and non-elderly MIBC had good efficacy and safety, and good quality of life after surgery. Although there are surgical and perioperative risks in elderly patients, there is no significant difference compared with non-elderly patients. In elderly patients requiring RC for bladder cancer, IC should remain the preferred mode of urinary diversion, and old age should not be used as an absolute exclusion criterion for IC.

A comparison of techniques to determine active motor threshold for transcranial magnetic stimulation research

The determination of active motor threshold (AMT) is a critical step in transcranial magnetic stimulation (TMS) research. As AMT is frequently determined using an absolute electromyographic (EMG) threshold (e.g., 200 µV peak-to-peak amplitude), wide variation in EMG recordings across participants has given reason to consider relative thresholds (e.g., = 2 × background sEMG) for AMT determination. However, these approaches have not been systemically compared. Our purpose was to compare AMT estimations derived from absolute and relative criteria commonly used in the quadriceps, and assess the test–retest reliability of each approach. We used a repeated measures design to assess AMT estimations in the vastus lateralis (VL) from eighteen young adults (9 males and 9 females; mean ± SD age = 23 ± 2 years) across two laboratory visits. AMT was determined for each criterion, at each lab visit. A paired samples t-test was used to compare mean differences in AMT estimations during the second laboratory visit. Paired samples t-tests and intraclass correlation coefficients (ICC2,1) were calculated to assess test–retest reliability of each criterion. Differences between the criteria were small and not statistically significant (p = 0.309). The absolute criterion demonstrated moderate to excellent reliability (ICC2,1 = 0.866 [0.648–0.950]), but higher AMTs were observed in the second visit (p = 0.043). The relative criteria demonstrated good-to-excellent test–retest reliability (ICC2,1 = 0.894 [0.746–0.959]) and AMTs were not different between visits (p = 0.420). TMS researchers aiming to track corticospinal characteristics across visits should consider implementing relative criterion approaches during their AMT determination protocol.

Prediction of nonresectability using the updated Predictive Index value model assessed by imaging and surgery in tubo-ovarian cancer: a prospective multicenter ISAAC study

BackgroundA laparoscopy-based scoring system was developed by Fagotti et al (Fagotti or Predictive Index Value (PIV)score) based on the intraoperative presence or absence of carcinomatosis on predefined sites. Later, the authors updated the PIV score calculated only in the absence of one or both absolute criteria of non-resectability (mesenteric retraction and miliary carcinomatosis of the small bowel) (updated PIV model). ObjectiveThe aim was to demonstrate the non-inferiority of ultrasound to other imaging methods (contrast enhanced computed tomography (CT) and whole-body diffusion-weighted (WB DWI)/MRI) in predicting non-resectable tumor (defined as residual disease>1 cm) using the updated PIV model in patients with tubo-ovarian cancer. The agreement between imaging and intraoperative findings as a reference was also calculated. Study designThis was a European prospective multicenter observational study. We included patients with suspected tubo-ovarian carcinoma who underwent preoperative staging and prediction of non-resectability at ultrasound, CT, WB-DWI/MRI and surgical exploration. The predictors of non-resectability were suspicious mesenteric retraction and/or miliary carcinomatosis of the small bowel or if absent, a PIV>8 (updated PIV model). The PIV score ranges from 0 to 12 according to the presence of disease in six predefined intra-abdominal sites (great omentum, liver surface, lesser omentum/stomach/spleen, parietal peritoneum, diaphragms, bowel serosa/mesentery). The reference standard was surgical outcome, in terms of residual disease>1 cm, assessed by laparoscopy and/or laparotomy. The area under the receiver operating characteristic curve (AUC) to assess the performance of the methods in predicting non-resectability was reported. Concordance between index tests at detection of disease at six predefined sites and intraoperative exploration as reference standard was also calculated using Cohen’s kappa. ResultsThe study was between 2018 and 2022 in five European gynecological oncology centers. Data from 242 patients having both mandatory index tests (ultrasound and CT) were analyzed. 145/242 (59.9%) patients had no macroscopic residual tumor after surgery (R0) (5/145 laparoscopy and 140/145 laparotomy) and 17/242 (7.0%) had residual tumor ≤1cm (R1) (laparotomy). In 80/242 patients (33.1%), the residual tumor was >1 cm (R2), 30 of them underwent laparotomy and maximum surgery was carried out and 50/80 underwent laparoscopy and cytoreduction was not feasible in all of them.After excluding 18/242 (7.4%) patients operated on but not eligible for extensive surgery, the predictive performance of three imaging methods was analyzed in 167 women. The AUCs of all methods in discriminating between resectable and non-resectable tumor was 0.80 for ultrasound, 0.76 for CT, 0.71 for WB-DWI/MRI and 0.90 for surgical exploration. Ultrasound had the highest agreement (Cohen’s kappa ranging from 0.59 to 0.79) compared to CT and WB-DWI/MRI to assess all parameters included in the updated PIV model. ConclusionsUltrasound showed non-inferiority to CT and to WB-DWI/MRI in discriminating between resectable and non-resectable tumor using the updated PIV model. Ultrasound had the best agreement between imaging and intraoperative findings in the assessment of parameters included in the updated PIV model. Ultrasound is an acceptable method to assess abdominal disease and predict non-resectability in patients with tubo-ovarian cancer in the hands of specially trained ultrasound examiners.

Comparative accuracy of four guidelines to predict high-grade dysplasia or malignancy in surgically resected pancreatic intraductal papillary mucinous neoplasms: Small nuances between guidelines lead to vastly different results.

The guidelines regarding the management of intraductal papillary mucinous neoplasms (IPMNs) all have slightly different surgical indications for high-risk lesions. We aim to retrospectively compare the accuracy of four guidelines in recommending surgery for high-risk IPMNs, and assess the accuracy of elevated CA-19-9 levels and imaging characteristics of IPMNs considered high-risk in predicting malignancy or high-grade dysplasia (HGD). The final histopathological diagnosis of surgically resected high-risk IPMNs during 2013-2020 were compared to preoperative surgical indications, as enumerated in four guidelines: the 2015 American Gastroenterological Association (AGA), 2017 International Consensus, 2018 European Study Group, and 2018 American College of Gastroenterology (ACG). Surgery was considered "justified" if histopathology of the surgical specimen showed HGD/malignancy, or there was postoperative symptomatic improvement. Surgery was postoperatively justified in 26/65 (40.0%) cases. All IPMNs with HGD/malignancy were detected by the 2018 ACG and the combined (absolute and relative criteria) 2018 European guidelines. The combined ("high-risk stigmata" and "worrisome features") 2017 International guideline missed 1/19 (5.3%) IPMNs with HGD/malignancy. The 2015 AGA guideline missed the most cases (11/19, 57.9%) of IPMNs with HGD/malignancy. We found the features most-associated with HGD/malignancy were pancreatic ductal dilation, and elevated CA-19-9 levels. Following the 2015 AGA guideline results in the highest rate of missed HGD/malignancy, but the lowest rate of operating on IPMNs without these features; meanwhile, the 2018 ACG and the combined (absolute and relative criteria) 2018 European guidelines result in more operations for IPMNs without HGD/malignancy, but the lowest rates of missed HGD/malignancy in IPMNs.

Incidence of contrast-associated acute kidney injury: a prospective cohort.

Contrast-associated acute kidney injury (CA-AKI) is a deterioration of kidney function that occurs after the administration of a iodinated contrast medium (ICM). Most studies that defined this phenomenon used older ICMs that were more prone of causing CA-AKI. In the past decade, several articles questioned the true incidence of CA-AKI. However, there is still a paucity of a data about the safety of newer ICM. To assess the incidence of CA-AKI in hospitalized patients that were exposed to computed tomography (CT) with and without ICM. Prospective cohort study with 1003 patients who underwent CT in a tertiary hospital from December 2020 through March 2021. All inpatients aged > 18 years who had a CT scan during this period were screened for the study. CA-AKI was defined as a relative increase of serum creatinine of ≥ 50% from baseline or an absolute increase of ≥ 0.3 mg/dL within 18 to 48 hours after the CT. Chi-squared test, Kruskal-Wallis test, and linear regression model with restricted cubic splines were used for statistical analyses. The incidence of CA-AKI was 10.1% in the ICM-exposed group and 12.4% in the control group when using the absolute increase criterion. The creatinine variation from baseline was not significantly different between groups. After adjusting for baseline factors, contrast use did not correlate with worse renal function. The rate of CA-AKI is very low, if present at all, with newer ICMs, and excessive caution regarding contrast use is probably unwarranted.

Stability analysis for an ad-hoc model predictive control in DC/DC converters with a constant power load

This paper presents a stability analysis for a horizon-one continuous control set model predictive control (MPC) for DC/DC converters connected to a constant power loads (CPLs). Different MPC approaches have been previously presented, each tailored to a specific type of converter but without a formal stability proof, failing to ensure robust performance across various operating conditions. Unlike previous works in the scientific literature, our approach is general and applicable to any second-order DC/DC converter, including the Buck, Boost, Buck-Boost, and non-inverting Buck-Boost converters. A formal stability analysis was conducted using the proposed approach, initially for the open-loop system and subsequently for the closed-loop system. The trace-determinant or triangle criterion was employed for discrete-time systems in R2. Three analyses were conducted to evaluate the performance of the proposed MPC, showing the stability issues of DC/DC converters with CPLs in open loops. This work proposes solutions using the suggested technique. Numerical simulations utilizing the Boost and Buck-Boost converters demonstrate that, in open-loop operation, even minor perturbations in the CPL value can destabilize the behavior of electrical variables. In addition, simulations show that, for the Boost converter, the settling time was about 1.5ms. Meanwhile, in the Buck-Boost case, it was about 5ms. Standardized control indicators, such as the integral absolute error criterion (IAE), the integral of the time-multiplied absolute error criterion (ITAE), and the integral of the time-multiplied square error criterion (ITSE), confirm the effective performance of the proposed one-step MPC. The values range between 1.521×10−2 and 4.591×10−6 for the Boost converter, and between 6.607×10−3 and 3.366×10−6 for the Buck-Boost topology.

Chronic Use of Antihypertensive Medications and Peak Exercise Blood Pressure in Adult Men and Women from the BALL ST Cohort.

To determine if individuals chronically (>1 yr) prescribed antihypertensive medications have a normal BP response to peak exercise compared with unmedicated individuals. Participants included 2555 adults from the Ball State Adult Fitness Longitudinal Lifestyle STudy cohort who performed a peak treadmill exercise test. Participants were divided into groups by sex and antihypertensive medication status. Individuals prescribed antihypertensive medications for >1 yr were included. Exaggerated and blunted SBP within each group was categorized using the Fitness Registry and the Importance of Exercise: A National Database (FRIEND) and absolute criteria as noted by the American Heart Association. The unmedicated group had a greater prevalence ( P < 0.05) of blunted SBP responses, whereas the medicated group had a higher prevalence ( P < 0.05) of exaggerated SBP responses using both the FRIEND and absolute criteria. Peak SBP was higher ( P < 0.01) in medicated compared with unmedicated participants in the overall cohort when controlling for age and sex, but not after controlling for resting SBP ( P = 0.613), risk factors ( P = 0.104), or cardiorespiratory fitness ( P = 0.191). When men and women were assessed independently, peak SBP remained higher in the medicated women after controlling for age and resting SBP ( P = 0.039), but not for men ( P = 0.311). Individuals on beta-blockers had a higher peak SBP even after controlling for age, sex, risk factors, and cardiorespiratory fitness ( P = 0.022). Individuals on antihypertensive medications have a higher peak SBP response to exercise. Given the prognostic value of exaggerated peak SBP, control of exercise BP should be considered in routine BP assessment and in the treatment of hypertension.

Energy consumption optimization model and system for the pellet drying process of straight grate

The drying process is a crucial stage in the thermal treatment of iron ore pellets in a straight grate, as it has a direct impact on pellet quality and energy consumption. Consequently, this paper develops a simulation model for the pellet bed drying process, which is validated through industrial data and enables the visualization of temperature and moisture distribution within the pellet bed. Based on the simulation model, an optimization model for the drying process is developed to minimize the specific energy consumption per tonne of green pellets. The constraints of the drying process are the moisture content requirements and burst temperature. A genetic algorithm is employed to optimize the parameters such as trolley speed, pellet bed thickness, air temperature, and air pressure. The results show that, with an absolute error criterion of 10 °C, the temperature calculation accuracy of the simulation model exceeds 86%, effectively describing the drying process in a straight grate sintering machine. Under yield limitations, the optimal cumulative energy consumption per tonne of green pellet is reduced by 1.50% during the drying process. Finally, a simulation and optimization system for the drying process in the straight grate is implemented in C++. This system not only generates essential data for designing the drying section in a straight grate but also lays a theoretical foundation for system optimization and optimal control.

A Cascade PID Controller Design with Cuckoo Optimization Algorithm (COA) and Input Shaping (IS)

From past to present, Proportional-Integral-Derivative (PID) controllers stand out as the most widely used types of controllers. Due to the high-performance requirements, experimentally determined controller coefficients necessitate the application of modern optimization techniques. In this study, Ziegler-Nichols, Chien-Hrones-Reswick, and Cohen-Coon methods, which allow parameter calculation through the open-loop system's step response method, were compared with the Cuckoo Optimization Algorithm for PID controllers designed for a brush-commutated DC motor with unknown parameters in the Matlab environment. The comparison was based on Integral of Absolute Error (IAE), Integral of Square Error (ISE), Integral of Time-weighted Absolute Error criterion. Similarly, the performance of the Cuckoo Algorithm was discussed in terms of stability margins and stability peaks. In this comparison, it was observed that the PID controller optimized with the Cuckoo Algorithm operated with high proportional and integral coefficients to minimize the cost function, resulting in overshoot in the system response. Input shaping, a commonly used method in open-loop control of both brushed and brushless DC motor systems, was integrated into the system to mitigate this overshoot. The hybrid controller achieved the best performance in terms of IAE, ISE and ITAE in the system response, with less overshoot compared to the other mentioned methods.

Low conservative stability criteria for discrete-time Lur’e systems with sector and slope constrained nonlinearities

Lur’e system is an important nonlinear system in engineering, which is composed of a feedback connection of a linear dynamic system and a nonlinear system that satisfies the sector constraint. In this paper, for nominal and uncertain discrete Lur’e systems with time-varying delays, the absolute and robustly absolute stability are studied in detail with the nonlinearity satisfying the sector and slope constraints. Firstly, an augmented Lyapunov–Krasovskii functional (LKF) is designed, in which some augmented vectors are selected to increase the coupling information between the delay intervals and other system state variables. At the same time, some effective integral terms of nonlinear state variables are extended in the LKF according to the characteristics of sector constraint and slope constraint. Secondly, a general lemma of summation inequality for free-weighted matrices is given, which adds some coupling information between vectors and extends the search range for solving linear matrix inequalities (LMIs). Thirdly, by synthesizing the general summation inequality and the newly constructed LKF, different absolute stability criteria are derived respectively, and the absolute stability criteria are extended to robustly absolute stability cases with uncertain parameters. The stability criteria reduce the conservatism of some previously proposed results. Finally, some common numerical examples and simulations are used to verify the results of this paper.

Probing the inner Galactic halo with blue horizontal-branch stars

Context. Stars that are found on the blue horizontal-branch (BHB) evolved from low-mass stars that have completed their core hydrogen-burning main sequence (MS) stage and undergone the helium flash at the end of their red giant phase. Hence, they are very old objects that can be used as markers in studying galactic structure and formation history. The fact that their luminosity is virtually constant at all effective temperatures also makes them good standard candles. Aims. We have compiled a catalogue of BHB stars with stellar parameters calculated from spectral energy distributions (SEDs) constructed using data from multiple large-scale photometric surveys. In addition, we update our previous Gaia Early Data Release 3 (EDR3) catalogue of BHB stars with parallax errors less than 20% by using the SED results to define the selection criteria. The purpose of these catalogues is to create a set of BHB star candidates with reliable stellar parameters. In addition, they provide a more complete full-sky catalogue with candidate objects found along the whole BHB from where RR-Lyrae are found on the instability strip to the extreme horizontal-branch (EHB). Methods. We selected a large dataset of Gaia Data Release 3 (DR3) objects based only on their position on the colour-magnitude diagram (CMD), along with the tangential velocity and parallax errors. The SEDs were then used to evaluate contamination levels in the dataset and derive optimised data quality acceptance constraints. This allowed us to extend the Gaia DR3 colour and absolute magnitude criteria further towards the EHB. The level of contamination found using SED analysis was confirmed by acquiring spectra using the Ondrejov Echelle spectrograph, attached to the Perek 2m telescope at the Astronomical Institute of the Czech Academy of Sciences. Results. We present a catalogue of 9172 Galactic halo BHB candidate stars with atmospheric and stellar parameters calculated from synthetic SEDs. We also present an extended Gaia DR3-based catalogue of 22 335 BHB candidate stars with a wider range of effective temperatures and Gaia DR3 parallax errors of less than 20%. This represents an increase of 33% compared to the our 2021 catalogue, with a contamination level of 10%.

Compare Some Shrinkage Bayesian Estimation Method forGumbel-Max Distribution with Simulation

The Gumbel max distribution is one of the most important statistical distributions because it has many applications, especially in the field of water research and the prediction of earthquakes and volcanoes. This work includes a comparison of several Shrinkage Bayesian methods, namely the Shrinkage Bayesian Square Loss Function, Shrinkage Bayesian Lenix Function, and Shrinkage Bayesian Unix Function to estimate the distribution parameter. The research also includes several simulated experiments according to the sample size change and the real value of the distribution parameter. The number of experiments is 15 simulated experiments based on the difference sample size and true distribution parameter values. The results of the simulation experiments are compared depending on each of the absolute least difference criteria ( and the mean squared error (). The comparison results show that the estimation method is affected by the sample size, and the real value of the distribution parameter. The best estimation method is the Shrinkage Bayesian Lenix Function. The Bayesian methods can be applied to other statistical distributions such that the Lindley Weibull distribution and logistics distribution.