Learning based cross-coupled control for multi-axis high precision positioning systems

In this paper, a controller featuring cross-coupled control and iterative learning control schemes is designed and implemented on a modular two-axis positioning system in order to improve both contour and tracking accuracy. Instead of using the standard contour estimation technique proposed with the variable gain cross-coupled control, a computationally efficient contour estimation technique is incorporated with the presented control design. Moreover, implemented contour estimation technique makes the presented control scheme more suitable for arbitrary nonlinear contours. Effectiveness of the control design is verified with simulations and experiments on a two-axis positioning system. Also, simulations demonstrating the performance of the control method on a three-axis positioning system are provided. The resulting controller is shown to achieve nanometer level contouring and tracking performance. Simulation results also show its applicability to three-axis nano-positioning systems. Copyright © 2012 by ASME

Adaptive correction and look-up table based interpolation of quadrature encoder signals

This paper presents a new method to increase the available measurement resolution of quadrature encoder signals. The proposed method features an adaptive signal correction phase and an interpolation phase. Typical imperfections in the encoder signals including amplitude difference, mean offsets and quadrature phase shift errors are corrected using recursive least squares with exponential forgetting and resetting. Interpolation of the corrected signals are accomplished by a quick access look-up table formed offline to satisfy a linear mapping from available sinusoidal signals to higher order sinusoids. The position information can be derived from the conversion of the high-order sinusoids to binary pulses. With the presented method, 10nm resolution is achieved with an encoder having 1μm of original resolution. Further increase in resolution can also be satisfied with minimizing electrical noises. Experiment results demonstrating the effectiveness of the proposed method for a single axis and two axis slider systems are given. Copyright © 2012 by ASME

Development and validation of an adaptive method to generate high-resolution quadrature encoder signals

This paper presents a new method to increase the measurement resolution of quadrature encoders. The method contains an adaptive signal correction step and a signal interpolation step. Measured encoder signals contain imperfections including amplitude differences, mean offsets, and quadrature phase shift errors. With the proposed method, these errors are first corrected by using recursive least squares (RLS) estimation with exponential forgetting and resetting. Then, the corrected signals are interpolated to higher order sinusoids using a quick access look-up table generated offline. The position information can be obtained with the conversion of these high-order sinusoids to binary pulses and counting the zero crossings. Using the method presented here, a 10 nm measurement resolution is obtained using an encoder with 1 μm off-the-shelf resolution. Validation of the method and the practical limitations are also presented. Further increase in the resolution can be achieved by minimizing the effects of the electrical noise.Copyright © 2014 by ASME

Design and analysis of a modular learning based cross-coupled control algorithm for multi-axis precision positioning systems

Increasing demand for micro/nano-technology related equipment resulted in growing interest for precision positioning systems. In this paper a modular controller combining cross-coupled control and iterative learning control approaches to improve contour and tracking accuracy at the same time is presented. Instead of using the standard error estimation technique, a computationally efficient and modular contour error estimation technique is used. The new controller is more suitable for tracking arbitrary nonlinear contours and easier to implement to multi-axis systems. Stability and convergence analysis for the proposed controller is presented with the necessary conditions. Effectiveness of the control design is verified with simulations and experiments on a two-axis positioning system. The resulting positioning system achieves nanometer level contouring and tracking performance. © 2016, Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg

The Relationship of Amelogenesis Imperfecta and Nephrocalcinosis Syndrome

Aim: To analyze the prevalence and associated oral findings of nephrocalcinosis in a group of patients affected with amelogenesis imperfecta (AI). The relationship between types of AI and nephrocalcinosis were also evaluated. Design: This study examines patients who were referred to Pediatric Dentistry Department of SDU between the years of 2002-2007 and who, upon clinical and radiological examination, were diagnosed with AI and treated. Patients were offered information about the possibility of nephrocalcinosis syndrome. Patients who agreed to have tests carried out on their renal system were advised to visit the department of nephrology at the clinic. Results: Suspicious radiopacity was observed during renal ultrasonography of a controlled number of patients with hypoplastic type AI. Laboratory results revealed low Ca values (100-300 mg/days) and normal P values (0.4-1.3 g/days). Delayed eruption, gingival hyperplasia, pulp stones and orthodontic problems were also observed in the same patient groups. Conclusion: Although renal findings were observed in a few patients, pediatric dentists are the doctors who are the first to have early contact with this patient group. Because of the potential risk of nephrocalcinosis, early diagnosis may offer good prognosis

High-Speed High Effiency Large Area Resonant Cavity Enhanced p-I-n Photodiodes for Multimode Fiber Communications

Cataloged from PDF version of article.In this letter, we report AlGaAs–GaAs p-i-n photodiodes with a 3-dB bandwidth in excess of 10 GHz for devices as large as 60- m diameter. Resonant cavity enhanced photodetection is employed to improve quantum efficiency, resulting in more than 90% peak quantum efficiency at 850 nm

Rumput Laut (Ulva lactuca) sebagai Pakan Substitusi Sapi Bali Sapihan di Musim Kemarau dengan Level Energi yang Berbeda

Penelitian dilakukan untuk mengetahui kualitas dan pengaruh rumput laut (Ulva lactuca) sebagai pakan substitusi untuk sapi Bali sapihan di musim kemarau dengan level energi yang berbeda. Penelitian dilakukan dua tahap yaitu perlakuan in vitro untuk mengetahui level ideal pemberian tepung U. lactuca dengan perlakuan RA = hay rumput alam; RAK = RA+konsentrat; RAKU5 =RAK+U. lactuca 5%; RAKU10= RAK+U. lactuca 10%; RAKU15= RAK+U. lactuca 15%; RAKU20= RAK+U. lactuca 20%. Tahap kedua menggunakan rancangan Bujur Sangkar Latin dengan perlakuan R1 = EM 7,3 MJ, R2 = EM 8 MJ dan R3 = EM 8,7 MJ. Hasil penelitian menunjukkan bahwa level ideal pemberian yang dapat digunakan adalah 15% dengan nilai kecernaan bahan kering dan bahan organik tertinggi yaitu 77,79 dan 78,56%.  Tahap kedua yaitu pemberian tepung U. lactuca sebanyak 15% dari total ransum dengan level energy yang berbeda untuk sembilan ekor sapi Bali sapihan dengan tujuan mengetahui tingkat konsumsi dan kecernaan dengan perlakuan EM R1= 7,3 MJ; R= 8 MJ; dan R3= 8,7 MJ. Hasil penelitian menunjukkan bahwa substitusi tepung U. lactuca sebanyak 15% tidak memberikan pengaruh negatif terhadap konsumsi dan kecernaan. Hasil sidik ragam menunjukkan ransum dengan energi 8 MJ memiliki konsumsi dan kecernaan yang sama dengan energi 8,7 MJ namun lebih tinggi dibandingkan dengan ransum  berenergi 7,3 MJ

High-speed >90% quantum-efficiency p–i–n photodiodes with a resonance wavelength adjustable in the 795–835 nm range

Cataloged from PDF version of article.We report GaAs/AlGaAs-based high-speed, high-efficiency, resonant cavity enhanced p–i–nphotodiodes. The devices were fabricated by using a microwave-compatible fabrication process. By using a postprocess recess etch, we tuned the resonance wavelength from 835 to 795 nm while keeping the peak efficiencies above 90%. The maximum quantum efficiency was 92% at a resonance wavelength of 823 nm. The photodiode had an experimental setup-limited temporal response of 12 ps. When the system response is deconvolved, the 3 dB bandwidth corresponds to 50 GHz, which is in good agreement with our theoretical calculations. © 1999 American Institute of Physic

Hypertensive Disorders of Pregnancy are Associated with Differences in Maternal Serum Concentrations of Arachidonic Acid Metabolites

Background: Hypertensive disorders of pregnancy (HDP), including gestational hypertension, chronic hypertension, and preeclampsia, are a significant cause of maternal morbidity and mortality in the United States. Dysregulation of inflammation is thought to play a role in the development of HDP. Maternal diet has the potential to alter the risk of HDP by modulating inflammation. Arachidonic acid (AA) is a dietary polyunsaturated fatty acid which can be metabolized into both pro- and anti-inflammatory bioactive metabolites. Significance of Problem: HDP places women and their infants at risk for potentially severe pregnancy complications including placental abruption, embolism, end-organ failure, or death. Few treatments are currently available for HDP. Question: The objective of this study was to describe how maternal AA metabolites serum concentrations are associated with diagnosis of HDP. Experimental Design: Serum was collected from 121 pregnant women admitted to the labor and delivery unit at Nebraska Medical Center. Women were divided into normotensive or hypertensive groups based on definitions from the American College of Obstetricians and Gynecologists (ACOG). Concentrations of AA metabolites were measured using liquid chromatography-mass spectrometry. Descriptive statistics were generated, and Mann-Whitney U tests were used to compare metabolite concentrations between groups. Results: Women with HDP had significant higher serum concentrations of PGF2α (p=0.02) and 15-HETE (p=0.04), two metabolites with known inflammatory and vasoconstrictive properties. Women with HDP had significantly lower serum concentrations of 8(9)-DiHET (p=0.04), 11(12)-DiHET (p=0.04), and 14(15)-DiHET (p=0.001), which are all associated with vasodilation. Unexpectantly, hypertensive mothers also had lower serum concentrations of 5-HETE (p=0.02), which is associated with vasoconstriction. Conclusion: Overall, our study reveals that mothers diagnosed with HDP had significantly higher serum concentrations of vasoconstrictive AA metabolites and significantly lower serum concentrations of vasodilating AA metabolites compared to normotensive mothers. Future directions include analyzing differences in maternal metabolite profile separately for mothers with chronic hypertension, gestational hypertension, and preeclampsia compared to normotensive mothers. Results from these analyses will guide nutritional recommendations for women at risk of developing HDP.https://digitalcommons.unmc.edu/chri_forum/1062/thumbnail.jp

Omega-3 Fatty Acid-Derived Resolvin D2 Regulates Human Placental Vascular Smooth Muscle and Extravillous Trophoblast Activities

Omega-3 fatty acids are important to pregnancy and neonatal development and health. One mechanism by which omega-3 fatty acids exert their protective effects is through serving as substrates for the generation of specialized pro-resolving lipid mediators (SPM) that potently limit and resolve inflammatory processes. We recently identified that SPM levels are increased in maternal blood at delivery as compared to umbilical cord blood, suggesting the placenta as a potential site of action for maternal SPM. To explore this hypothesis, we obtained human placental samples and stained for the SPM resolvin D2 (RvD2) receptor GPR18 via immunohistochemistry. In so doing, we identified GPR18 expression in placental vascular smooth muscle and extravillous trophoblasts of the placental tissues. Using in vitro culturing, we confirmed expression of GPR18 in these cell types and further identified that stimulation with RvD2 led to significantly altered responsiveness (cytoskeletal changes and pro-inflammatory cytokine production) to lipopolysaccharide inflammatory stimulation in human umbilical artery smooth muscle cells and placental trophoblasts. Taken together, these findings establish a role for SPM actions in human placental tissue