Making the best voltage/current regulation against disturbances and uncertainties and, most importantly, to minimize chattering effect in power electronics circuits, the hysteresis modulation based ...(HM) sliding mode control (SMC) is widely used. There are various research on this subject in the literature. However, the variable switching frequency that HM-SMC brought about has regrettably overlooked in the majority of these research. This problem is addressed in depth in this paper by demonstrating how the switching frequency is affected by various factors. Next, the fuzzy logic control (FLC) is proposed for the first time as a solution for switching frequency regulation in a power electronics circuit. The proposed FLC for switching frequency regulation fortifies the system described in this study and sets it apart from many other HM-SMC studies in the literature with its advantages against the difficulties caused by variable switching frequency such as excessive switching and driver power losses. On the other hand, the fast terminal SMC (FTSMC) which has significantly superior convergence performance than its counterparts, has been recommended for voltage regulation. The proposed FTSMC technique employs only one voltage sensor different from the past literature. This simplifies the proposed control mechanism in practical implementation and also makes the system economical. The two proposed controllers’ compatibility with one another has been tested through experimental tests, including the steady-state condition, variations in switching frequency reference value, step change of load resistance, output voltage reference value variation, and finally step change of input voltage. The outcomes of the experiments demonstrate that the switching frequency and output voltage are successfully regulated with good dynamic and steady state performance. Finally, the proposed techniques have been compared with six recent approaches from the existing literature to highlight their performance.
•FLC is employed for the first time in power electronics to regulate switching frequency.•Digital design has been made for the measurement of the switching frequency.•FTSMC is employed to deliver significantly superior convergence performance.•Proposed FTSMC provides better dynamic reaction due to its strong dynamic surface.
In this paper, a modified fast terminal sliding mode control (FTSMC) with a fixed switching frequency is proposed for regulating the output voltage of the DC-DC buck converters. The design steps of ...the proposed FTSMC such as the selection of sliding surface, switching control strategy, existence, robustness, and stability analysis are presented in detail. To overcome the variable switching frequency in FTSMC, a frequency control loop is designed. Moreover, the proposed FTSMC with fixed switching frequency can be implemented by using only one voltage sensor. Hence, the proposed control method not only offers a fast dynamic response and fixed switching frequency but also simplifies the controller design in practical implementation. The effectiveness of the proposed control methods has been investigated by experimental studies. The results reveal that the proposed methods exhibit a good performance under both steady-state and dynamic transients caused by the variations in load resistance, input voltage, and reference voltage. Moreover, the proposed method is compared with four existing methods.
The inherent unlimited high switching frequency of the sliding mode controller (SMC) is limited by practical constraints of the hysteresis modulation (HM) technique. The inductor current and output ...voltage of a converter can be regulated using a combination of HM-SMC. However, HM-SMC results in a variable switching frequency operation, which is not preferred due to Electromagnetic Interference (EMI) issues. In this paper, an interval fuzzy controller is designed and developed as a solution to enable HM-SMC. In addition, a robust sliding surface is proposed, which provides an improved dynamic response. The two proposed controllers’ compatibility with one another has been tested via experiments such as a step change in input voltage, load resistance variation, and finally, a step change in output voltage reference value. The test results validate that while the interval type-2 fuzzy maintains a constant switching frequency with acceptable dynamic responses, it successfully regulates the state variables of the system. A comparison of the performance of the proposed control method with existing techniques in the literature is presented.
In this study, a global fast terminal sliding-mode control (GFTSMC), which offers a faster convergence performance than its counterparts is constructed for managing the state variables of the DC-DC ...buck converters. For the first time in this study, the GFTSMC was designed for power electronics circuits based on hysteresis modulation (HM). The HM technique's variable switching frequency problem is overcome by reusing the GFTSMC structure, which enables the hysteresis band to be changed adaptively, and a fixed switching frequency is obtained. The proposed control scheme uses only one sensor for regulating the output voltage and controlling the switching frequency. Thus, an extremely economical and robust system, which is minimally affected by the negative aspects originating from the sensors, is obtained. Effectiveness of the proposed controller is validated with experimental studies. The experimental results shows that the output voltage and switching frequency are successfully controlled with good dynamic and steady state response. Finally, to validate the experimental feasibility of this paper, a comparison of the proposed method and four existing studies with different control schemes is presented.
In this study, an improved fast terminal sliding-mode control (FTSMC) is presented to control the output voltage of the DC-DC step-down converter. It has been compared to other techniques in the ...literature, including traditional sliding mode control (SMC) and terminal sliding mode control TMSC to demonstrate its performance. The proposed method and all other mentioned methods have been tested in simulation environment. The obtained simulation results are compared in terms of performance of converging error to zero for various conditions such as input voltage variations, step load change and tracking process. The obtained results show that the proposed improved FTSMC method provides the fastest convergence, the smallest rising time, and the smallest steady-state error than the SMC and TSMC method. In addition, no capacitor current was used in the simulations. The backward-euler method was integrated into the sliding surface used and thus only one sensor was used to control the state variables of the respective converter.
Previous research has shown that more information can be stored in visual working memory (VWM) when multiple items belong to the same object. Here, in four experiments, we investigated the object ...effect on memory for spatially equidistant features by manipulating simple, task-irrelevant contours that combined these features. In Experiments 1, 3, and, 4, three grating orientations, and in Experiment 2, one color and two orientations, were presented simultaneously to be memorized. Mixture modeling was applied to estimate both the precision and the guess rates of recall errors. Overall results showed that two target features were remembered more accurately when both were part of the same object. Further analysis showed that the probability of recall increased in particular when both features were extracted from the same object. In Experiment 2, we found that the object effect was greater for features from orthogonal dimensions, but this came at the cost of lower memory precision. In Experiment 3, when we kept the locations of the features perfectly consistent over trials so that the participants could attend to these locations rather than the contour, we still found object benefits. Finally, in Experiment 4 when we manipulated the temporal order of the object and the memory features presentations, it was confirmed that the object benefit is unlikely to stem from the strategical usage of object information. These results suggested that the object benefit arises automatically, likely at an early perceptual level.
Objective: Neurofibromatosis type 1 (NF1, #162200) is a common neurological disorder with de novo or inherited germline mutations of the Neurofibromin (NF1, ·613113). The purpose of this study is to ...increase the limited knowledge of NF1 in a small population-based dataset. Materials and Methods: This study enrolled patients with clinically suspected NF1 referred to the Kayseri Training and Research Hospital, Medical Genetics Department, between 2015 and 2017. The local ethics committee approved this study. Next-generation sequencing was performed for the genetic analysis. The genetic, demographic, and clinical features of the participants were characterized. Results: A total of 79 cases of NF1 were included. Of these cases, 40 were male, and 39 were female. The mean age was 11.9 years, and most were younger than 18 years. The most common complaint was café au lait macules. The 61 (77.3%) patients had pathogenic variants, and 16 (26.2%) were novel. Mostly affected mutation sites were exonic regions (n=54, 88.5%). The most common mutated exon was exon 38 (n=7, 11.5%), and most of the detected mutations were nonsense mutations (31%). Conclusion: It is one of Türkiye's largest NF1 study groups, where all exons of the NF1 gene were analyzed. This study contributes novel variants to the literature. There was no mutational hotspot region, and no significant relationship between genotype and phenotype was observed. Further studies and large sample sizes are required to better understand the relationship between NF and genetic changes.
Background
Iron deficiency and iron-deficiency anemia are the most common nutritional deficiencies in children, especially in developing countries. Iron-deficiency anemia in infancy is associated ...with impaired neurodevelopment. Studies have shown an association between iron deficiency without anemia and adverse effects on psychomotor development.
Objective
To determine the effects of iron deficiency and iron-deficiency anemia on psychomotor development in childhood.
Methods
We evaluated psychomotor development in healthy children with iron deficiency and iron-deficiency anemia with the use of the Denver II Developmental Screening Test (DDST-II). If the child score was more than 90th percentile compared to children in the same age group, the test was scored as “delay”; it was scored as a “caution” if the child score was between the 75th and 90th percentiles. The test result was interpreted as “normal,” if there was no delay and only one “caution” for any item. If the child had one or more “delays” or more than two “cautions,” the result was classified as “abnormal.”
Results
DDST-II scores were abnormal in 67.3% of subjects with iron-deficiency anemia, 21.6% of those with iron deficiency, and 15.0% of control subjects. The difference from the control group in the percentage of abnormal scores was significant for subjects with iron-deficiency anemia (p < .01) but not for those with iron deficiency (p = 0.203); p > .05. (p-value, post-hoc comparison of 2 groups.)
Conclusions
Iron-deficiency anemia impaired psychomotor development during childhood. However, the evidence on the adverse effects of iron deficiency remains controversial. The Denver II Developmental Screening Test is a valuable test to detect early developmental delays, especially in infants with risk factors.
In the treatment of pilonidal sinus disease different approaches are used such as conservative treatment and fasciocutaneous rotation flap. The aim of this study was to evaluate the efficacy of ..."de-epithelialization technique" as a new approach in pilonidal sinus disease treatment.
Forty pilonidal sinus disease patients treated with de-epithelialization method were evaluated retrospectively. Patient age, gender, body mass index, wound healing time, visual analog scale scores, operation times, hospital stay duration, drain removal time, cosmetic satisfaction rates, complications, and recurrence rates were evaluated.
The numbers of male and female patients in this study were 39 and 1, respectively. The median age of the patients was 25 years and the mean BMI was 26.6. The mean operating time was 43 min, and all patients were discharged 5 h after the operation. Wound healing time varied from 10 to 20 days. Median follow-up period was 9 months (4-17 months). One patient with high body mass index suffered from partial wound separation. No other complications such as infections and fluid collections (hematoma and seromas) were observed. Maximum cosmetic satisfaction rate was 90% (n=36), and no patient had a recurrence during the follow-up period.
"De-epithelialization" may be considered as a complementary and/or alternative approach to other surgical techniques such as primary closure, rhomboid excision, and Limberg flap in the treatment of pilonidal sinus disease, with acceptable cosmesis and recurrence rates.
Introduction
The EyeCOPE study characterized noninfectious intermediate posterior, or panuveitis (NIIPPU) before biologic agents were widely available.
Methods
This retrospective, observational study ...included adults with NIIPPU attending a routine ophthalmological visit. Data were collected from the study visit and medical records.
Results
Of 565 patients, 58.8% were female, and the mean age was 41.3 years; 33.8% had idiopathic uveitis and 45.8% had panuveitis. The median time from symptom onset to diagnosis and treatment was 27.0 and 30.5 days, respectively. Patients received immunosuppressants and systemic/local corticosteroids. Most patients experienced substantial decline in ocular function (mean best corrected visual acuity, 0.4 logMAR). Mean total work productivity impairment among employed patients was 31.0%. Most patients reported ocular complications (70.8%) such as vision loss and cataracts.
Conclusions
Despite treatment, most patients with NIIPPU experienced a decline in ocular function and ocular complications. There is an unmet need for additional NIIPPU treatment, such as targeted monoclonal antibodies.
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