Global asymptotic stability for a periodic delay hematopoiesis model with impulses

In this paper, sufficient conditions for the global asymptotic stability of a broad family of periodic impulsive scalar delay differential equations are obtained. These conditions are applied to a periodic hematopoiesis model with multiple time-dependent delays and linear impulses, in order to establish criteria for the global asymptotic stability of a positive periodic solution. The present results are discussed within the context of recent literature. In conclusion, when compared with previous works, not only sharper stability criteria are obtained here, even for models without impulses, but also the usual constraints imposed on the linear impulses are relaxed.     

Investigation of β-Ga_2O_3 films and β-Ga_2O_3/GaN heterostructures grown by metal organic chemical vapor deposition

In this work,(-201) β-Ga_2O_3 films are grown on GaN substrate by metal organic chemical vapor deposition(MOCVD). It is revealed that the β-Ga_2O_3 film grown on GaN possesses superior crystal quality, material homogeneity and surface morphology than the results of common heteroepitaxial β-Ga_2O_3 film based on sapphire substrate. Further, the relevance between the crystal quality of epitaxial β-Ga_2O_3 film and the β-Ga_2O_3/GaN interface behavior is investigated. Transmission electron microscopy result indicates that the interface atom refactoring phenomenon is beneficial to relieve the mismatch strain and improve the crystal quality of subsequent β-Ga_2O_3 film. Moreover, the energy band structure of β-Ga_2O_3/GaN heterostructure grown by MOCVD is investigated by X-ray photoelectron spectroscopy and a large conduction band offset of 0.89 eV is obtained. The results in this work not only convincingly demonstrate the advantages of β-Ga_2O_3 films grown on GaN substrate, but also show the great application potential of MOCVD β-Ga_2O_3/GaN heterostructures in microelectronic applications.     

An efficient numerical method to solve 2-D interval bi-modular problems via orthogonal polynomial expansion

An interval analysis of uncertain bi-modular problems is presented by addressing the efficiency of deterministic solution and reduction of computational cost on the non-linear FE iteration. Firstly, the singularity of 2-D conventional bi-modular constitutive matrix is pointed out via a concise mathematical illustration, and is removed via a complement of shear modulus consistent with the coaxial condition. A new FE model with a full rank constitutive matrix is developed to solve deterministic bi-modular problems, which is well performed in the numerical tests, particularly in term of convergence. Secondly, an orthogonal polynomial expansion based surrogate is constructed to alleviate the heavy computational burden caused by repeated non-linear FE solution in the optimization process for bounds estimation. Numerical examples are given to illustrate the accuracy and efficiency of proposed approach, and a good accordance can be observed between the results obtained by the proposed approach and reference solutions.     

Continuous and discrete zeroing neural dynamics handling future unknown-transpose matrix inequality as well as scalar inequality of linear class

Numerical Algorithms - In this paper, the future unknown-transpose matrix inequality (FUTMI) as well as scalar inequality is formulated and investigated for the first time. This particular class of...     

The effects of the no-touch gap on the no-touch bipolar radiofrequency ablation treatment of liver cancer: A numerical study using a two compartment model

The no-touch bipolar radiofrequency ablation (RFA) for cancer treatment is advantageous primarily because of its capability to prevent tumour track seeding (TTS). In this technique, the RF probes are placed at a distance (no-touch gap) away from the tumour boundary. Ideally, the RF probes should be placed sufficiently far from the tumour in order to avoid TTS. However, having a gap that is too large can lead to ineffective ablation. This paper investigates how the selection of the no-touch gap can affect the tissue electrical and thermal responses during the no-touch bipolar RFA treatment. Simulations were carried out on a two compartment model using the finite element method. Results obtained indicated that a gap that is too large may lead to incomplete ablation and failure to achieve significant ablation margin. However, keeping the gap to be too small may not be clinically practical. It was suggested that the incomplete ablation and the insufficient ablation margin observed in some of the cases may require the placement of additional probes around the tumour. The present study stresses on the importance of identifying the optimal no-touch gap that can avoid TTS without compromising the treatment outcome.     

Component ordering strategies in assembly systems with uncertain capacity and random yield

Sourcing components in a complex global supplier network may lead to a high degree of supply uncertainty. Events, such as unexpected production defects or insufficient supplier capacity, can cause unexpected shortages of required components and halt the assembly of final products. Accordingly, the assembly enterprises must effectively manage various supply uncertainties in their component ordering decisions to avoid such component shortfalls. These issues have guided this research to investigate the optimal ordering strategies of an assembler facing the following two types of supply uncertainty: the uncertain production capacity of a standard component (component 1) and the random production yield of a core component (component 2). The assembler makes the component ordering decisions before these supply uncertainties are realized. We characterize the optimal ordering decision and find that the assembler should order components 1 and 2 according to a fixed ratio, which only depends on the random yield of component 2 and the production cost of component 1, but not on the uncertain capacity of component 1. A case study is presented to further explore the intertwined effects of these two uncertainties in an assembly system. Finally, the model is extended to consider a secondary option of buying additional component 1 s after observing some or all of the supply uncertainties, and this secondary option endows the firm with different capabilities in counteracting the supply uncertainties.     

Embedded solitons in the $$(2+1)$$(2+1)-dimensional sine-Gordon equation

Nonlinear Dynamics - An effective and simple method to solve nonlinear evolution partial differential equations is the self-similarity transformation, in which one utilizes solutions of the known...