Errors of linear multistep methods and Runge-Kutta methods for singular perturbation problems with delays

AbstractThis paper is concerned with the error analysis of linear multistep methods and Runge-Kutta methods applied to some classes of one-parameter stiff singularly perturbed problems with delays. We derive the global error estimates of A(α)-stable linear multistep methods and algebraically and diagonally stable Runge-Kutta methods with Lagrange interpolation procedure. Numerical experiments confirm our theoretical analysis

Unexpected formation of hydrides in heavy rare earth containing magnesium alloys

AbstractMg–RE (Dy, Gd, Y) alloys show promising for being developed as biodegradable medical applications. It is found that the hydride REH2 could be formed on the surface of samples during their preparations with water cleaning. The amount of formed hydrides in Mg–RE alloys is affected by the content of RE and heat treatments. It increases with the increment of RE content. On the surface of the alloy with T4 treatment the amount of formed hydride REH2 is higher. In contrast, the amount of REH2 is lower on the surfaces of as-cast and T6-treated alloys. Their formation mechanism is attributed to the surface reaction of Mg–RE alloys with water. The part of RE in solid solution in Mg matrix plays an important role in influencing the formation of hydrides

Broadband Doherty Power Amplifier With Transferable Continuous Mode

In this paper, in-band continuous mode transferring (CMT) method is presented for designing broadband Doherty power amplifier (DPA). Specifically, transferable continuous mode, transferring between class-J continuum to class-F-1 continuum, is introduced into DPA at output back-off (OBO) power level for improving bandwidth and efficiency. For validation, a broadband DPA with operation mode transferring from continuous class-J to continuous class-F-1 is designed, fabricated and measured. Experimental results show the drain efficiencies (DEs) of the fabricated DPA are 46.3%-57.7% and 58.4%-69.1% at 6 dB OBO and peaking power levels over 1.7-2.6 GHz. The saturation power of this DPA is 43.1-45.2 dBm with a gain of 9.1-11.2 dB in the interested band. Furthermore, when the fabricated DPA is stimulated by a 20 MHz wideband signal with a peak-to-average power ratio (PAPR) of 7.05 dB at 2.4 GHz, the measured average power is 36.5 dBm with an average DE of 45.7%, and the measured adjacent channel leakage ratios (ACLRs) are -31.9 dBc and -50.4 dBc before and after DPD technique, respectively

Diffraction-based determination of single-crystal elastic constants of polycrystalline titanium alloys

Single-crystal elastic constants have been derived by lattice strain measurements using neutron diffraction on polycrystalline Ti-6Al-4V, Ti-6Al-2Sn-4Zr-6Mo and Ti-3Al-8V-6Cr-4Zr-4Mo alloy samples. A variety of model approximations for the grain-to-grain interactions, namely approaches by Voigt, Reuss, Hill, Kroener, de Wit and Matthies, including texture weightings, have been applied and compared. A load-transfer approach for multiphase alloys was also implemented and the results are compared with single-phase data. For the materials under investigation, the results for multiphase alloys agree well with the results for single-phase materials in the corresponding phases. In this respect, all eight elastic constants in the dual-phase Ti-6Al-2Sn-4Zr-6Mo alloy have been derived for the first time

A Novel Chemosynthetic Peptide with β-Sheet Motif Efficiently Kills Klebsiella pnuemoniae in a Mouse Model

Klebsiella pneumoniae (Kp) is one of the most common pathogens in nosocomial infections and is increasingly becoming multiple drug resistant. However, the molecular pathogenesis of Kp in causing tissue injury and dysregulated host defense remains elusive, further dampening the development of novel therapeutic measures. We have previously screened a series of synthetic antimicrobial beta-sheet forming peptides and identified a peptide (IRIKIRIK; ie, IK8L) with a broad range of bactericidal activity and low cytotoxicity in vitro. Here, employing an animal model, we investigated the antibacterial effects of IK8L in acute infection and demonstrated that peritoneal injection of IK8L to mice down-regulated inflammatory cytokines, alleviated lung injury, and importantly, decreased mortality compared to sham-injected controls. In addition, a math model was used to evaluate in vivo imaging data and predict infection progression in infected live animals. Mechanistically, IK8L can kill Kp by inhibiting biofilm formation and modulating production of inflammatory cytokines through the STAT3/JAK signaling both in vitro and in vivo. Collectively, these findings reveal that IK8L may have potential for preventing or treating Kp infection

Quantification of Residual Stress Relief by Heat Treatments in Austenitic Cladded Layers

The effect of the heat treatment on the residual stresses of welded cladded steel samples is analyzed in this study. The residual stresses across the plate’s square sections were determined using complementary methods; applying diffraction with neutron radiation and mechanically using the contour method. The analysis of the large coarse grain austenitic cladded layers, at the feasibility limits of diffraction methods, was only made possible by applying both methods. The samples are composed of steel plates, coated on one of the faces with stainless steel filler metals, this coating process, usually known as cladding, was carried out by submerged arc welding. After cladding, the samples were submitted to two different heat treatments with dissimilar parameters: one at a temperature of 620 °C maintained for 1 h and, the second at 540 °C, for ten hours. There was some difference in residual stresses measured by the two techniques along the surface of the coating in the as-welded state, although they are similar at the welding interface and in the heat-affected zone. The results also show that there is a residual stress relaxation for both heat-treated samples. The heat treatment carried out at a higher temperature showed sometimes more than 50% reduction in the initial residual stress values and has the advantage of being less time consuming, giving it an industrial advantage and making it more viable economically

Robotertechnik zur diffraktometrischen Charakterisierung von Restspannungs-, Textur-, Phasenentwicklung an technischen Komponenten

Am Materialforschungsdiffraktometer STRESS-SPEC der Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) wurde vor einiger Zeit ein BMBF gefördertes Robotersystem in Betrieb genommen. Damit wurde es erstmals möglich kompakte Proben von technischen Dimensionen bezüglich kristallographischer Textur, Restspannungen und Phasenzusammensetzungen automatisch zu charakterisieren. Der Roboter verfügt über drei Funktionen, die den Messablauf entscheidend vereinfachen und für Neutronenmessungen sehr wichtig teure Messzeit einsparen. Texturmessungen sind häufig Serienuntersuchungen zur Texturentwicklung als Funktion von Umformgrad, Umformtemperatur und Legierungszusammensetzung, so dass der Roboter als automatischer Probenwechsler erhebliche Zeitersparnis bringt. Zweitens fungiert der Roboter nicht nur als Probenwechsler, sondern ersetzt gleichzeitig auch die Eulerwiege zum Abfahren der einzelnen Polfiguren. Die dritte Funktion ist die Scanfunktion des Roboters, um zum Beispiel die Informationen über den Umfang von Rohren oder über Schweißnähten automatisch Messen zu können

Biomechanical study of two-level oblique lumbar interbody fusion with different types of lateral instrumentation: a finite element analysis

ObjectiveThe aim of this study was to verify the biomechanical properties of a newly designed angulated lateral plate (mini-LP) suited for two-level oblique lumbar interbody fusion (OLIF). The mini-LP is placed through the lateral ante-psoas surgical corridor, which reduces the operative time and complications associated with prolonged anesthesia and placement in the prone position.MethodsA three-dimensional nonlinear finite element (FE) model of an intact L1–L5 lumbar spine was constructed and validated. The intact model was modified to generate a two-level OLIF surgery model augmented with three types of lateral fixation (stand-alone, SA; lateral rod screw, LRS; miniature lateral plate, mini-LP); the operative segments were L2–L3 and L3–L4. By applying a 500 N follower load and 7.5 Nm directional moment (flexion-extension, lateral bending, and axial rotation), all models were used to simulate human spine movement. Then, we extracted the range of motion (ROM), peak contact force of the bony endplate (PCFBE), peak equivalent stress of the cage (PESC), peak equivalent stress of fixation (PESF), and stress contour plots.ResultsWhen compared with the intact model, the SA model achieved the least reduction in ROM to surgical segments in all motions. The ROM of the mini-LP model was slightly smaller than that of the LRS model. There were no significant differences in surgical segments (L1–L2, L4–L5) between all surgical models and the intact model. The PCFBE and PESC of the LRS and the mini-LP fixation models were lower than those of the SA model. However, the differences in PCFBE or PESC between the LRS- and mini-LP-based models were not significant. The fixation stress of the LRS- and mini-LP-based models was significantly lower than the yield strength under all loading conditions. In addition, the variances in the PESF in the LRS- and mini-LP-based models were not obvious.ConclusionOur biomechanical FE analysis indicated that LRS or mini-LP fixation can both provide adequate biomechanical stability for two-level OLIF through a single incision. The newly designed mini-LP model seemed to be superior in installation convenience, and equally good outcomes were achieved with both LRS and mini-LP for two-level OLIF

Efficacy and Safety of Glp-1 Analog Ecnoglutide in Adults With Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial

Glucagon-like peptide-1 (GLP-1) analogs are important therapeutics for type 2 diabetes and obesity. Ecnoglutide (XW003) is a novel, long-acting GLP-1 analog. We conducted a Phase 2, randomized, double-blind, placebo-controlled study enrolling 145 adults with T2DM. Participants were randomized to 0.4, 0.8, or 1.2 mg ecnoglutide or placebo as once-weekly injections for 20 weeks. The primary objective was to evaluate the efficacy of ecnoglutide, as measured by HbA1c change from baseline at Week 20. Secondary endpoints included body weight, glucose and lipid parameters, as well as safety. We show that, at end of treatment, the 0.4, 0.8, and 1.2 mg groups had statistically significant HbA1c reductions from baseline of -1.81%, -1.90%, and -2.39%, respectively, compared to -0.55% for placebo (P \u3c 0.0001). At end of treatment, 71.9% of the 1.2 mg group had HbA1c ≤ 6.5% versus 9.1% on placebo, and 33.3% had body weight reductions ≥5% versus 3.0% for placebo. Ecnoglutide was generally safe and well tolerated. China Drug Trials Registry CTR20211014