Microwave hyperthermia applicators used for thermal therapy of cancer employ a water bolus for tissue surface cooling and power coupling. The temperature-dependent dielectric property of the water bolus causes impedance mismatch and thermally driven instability during an hour-long treatment. This paper presents an optimized water-cooled folded metal patch microwave antenna with integrated fins to maintain thermal stability thereby enabling stable power coupling during treatment delivery. The applicator was designed using coupled electromagnetic–thermal–fluid–structural simulation framework and validated experimentally on tissue-equivalent phantoms. The optimized applicator with aperture size of 48 mm × 55 mm has return loss > 20 dB at 434 MHz, −10 dB power coupling bandwidth of 42 MHz, and maintains > 90% tangential electric field coupling to the tissue layers. The coupled EM-thermal and fluid analysis of the fin assisted applicator reduced internal water bolus temperature gradient from 5.13 to 0.38 K, which significantly improved power coupling coefficient to 96%. Experimental results of the optimized applicator designed with convective and radiative cooling showed stable power coupling >96% for 60-min heating in tissue mimicking phantoms. The coupled multiphysics approach provided the design framework for realizing clinically robust hyperthermia applicator with thermal stability and mechanical strength essential for clinical deployment, and development of site-specific hyperthermia applicators.
We study the n-dimensional Lotka–Volterra systemsxi˙=xi(∑j=1naijxj+bi),i=1,…,n,in Rn, where aij,bi∈R. A necessary and sufficient condition is obtained for the existence of a Darboux invariant of the form e−st∏i=1nxiℓi with s ≠ 0 for such systems. Based on this condition, the Lotka–Volterra systems are divided into three classes. For each class, we establish results on the existence of equilibrium points, bounded orbits, periodic orbits, and first integrals.
A vertex v of a 2-connected cubic graph G is λ-matchable if G has a spanning subgraph in which v has degree three whereas every other vertex has degree one, and we let λ(G) denote the number of such vertices. Clearly, λ=0 for bipartite graphs; ergo, we define λ-matchable pairs analogously, and we let ρ(G) denote the number of such pairs.We improve the constant lower bounds on both λ and ρ established recently by Chen, Lu and Zhang [Discrete Math., 2025] using matching-theoretic invariants arising from the seminal work of Lovász [J. Combin. Theory Ser. B, 1987], and we characterize all of the tight examples. We also solve the problem posed by Chen, Lu and Zhang: characterize 2-connected cubic graphs each of whose vertices is λ-matchable.
The construction of higher order uniformly convergent methods for the numerical resolution of any type of singularly perturbed problems, is an interesting task in applied mathematics. The main reason is that those methods permit obtaining good and efficient numerical approximations without increasing the computational cost of the numerical algorithm. Here, we study 2D elliptic weakly coupled systems of convection diffusion type, for which small positive parameters appear in both the diffusion and the convection terms. Moreover, we assume that the diffusion parameters at each equation of the system are different and the convection term has only a non zero component in one of the two spatial directions. Then, the exact solution has parabolic and regular layers in the boundary of the domain, which depend on the value and the ratio between the three small parameters. To solve the continuous problem, an hybrid finite difference scheme is used, which is constructed on an adequate Bakhvalov-Shishkin mesh; then, the scheme is a second order uniformly convergent method; this result is better than the obtained by previous methods existing in the literature to solve the same type of systems. We show the numerical results that the computational algorithm gives for a test problem; from them, we clearly observe the order of uniform convergence of the method and also its efficiency due the low computational cost needed to achieve the numerical results.
Abstract Lean construction techniques are being discussed for their benefits in dispute avoidance, along with waste reduction, productivity improvement, and minimizing time and cost overruns. However, implementing lean presents challenges, with stakeholder resistance to change being a primary obstacle. To address this resistance, current literature recommends adding new contract clauses to the traditional standard form contracts (SFCs) to make lean adoption contractually binding. However, since traditional SFC in construction often contains restrictive and one-sided clauses, integrating lean-friendly, collaborative clauses may conflict with existing ones, potentially creating new conflicts. This study, therefore, aims to assess the adaptability of Indian public sector undertakings (PSUs) SFCs to lean, i.e., the leanness of the contract. Built on a base framework developed from lean construction and contract drafting principles recommended in the literature, an automatic leanness assessment application is developed using a multilayer perceptron (MLP) model augmented with synthetic data augmentation and the synthetic minority oversampling technique (SMOTE), achieving an F1 score of 93%. After the assessment, the restrictive clause segments are neutralized using a lean-neutral template via a retrieval-augmented generation (RAG)- assisted large language model (LLM). This makes the traditional contract conducive to adding clauses that actively support lean implementation without conflicting with existing clauses.
