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Xia Lu

Publications and source records attributed to Xia Lu.

4 recordsLinked to original sources
PubMed2006

A domain evolution model for hysteresis in piezoceramic materials.

In this paper, we use a circular distribution to quantify certain domain properties and model the hysteresis behavior of piezoceramic materials. The model is constructed by bridging the characteristics of microscopic domain distribution into the macroscopic (or bulk) behavior. Contributions, other than those associated with the polarization of domains, to bulk quantities are also counted. A domain orientation distribution function is first selected and the corresponding distribution function parameters are chosen as the internal state variables. For the two-dimensional model, a von Mises-Fisher circular distribution is used. Instead of micromechanical analysis of domain motions that would involve large computation efforts, the delineation of domain evolution is simplified by considering the evolution of the domain orientation distribution, which is determined by the dynamic variations of the internal state variables. We also develop a procedure to identify the material constants introduced in the constitutive equations. The models are used to quantitatively characterize various hysteresis loops observed in piezoceramic materials.

Journal Article↗
PubMed2005

[A randomized controlled trail of taxol-based combination regimens for advanced gastric cancer].

BACKGROUND & OBJECTIVE: Standard chemotherapy for advanced gastric cancer remains undefined. Phase II trials show that taxol is effective in treating advanced gastric cancer. This multi-center prospective open randomized controlled study was to compare the efficacy of Taxol plus calcium folinate (CF)/5-fluorouracil (5-FU), Taxol plus oxaliplatin (OXA), and CF/5-FU plus cisplatin (DDP) on advanced gastric cancer, and analyze their toxicities. METHODS: Patients with measurable unresectable and/or metastatic gastric carcinoma were randomized into CF/5-FU+DDP (control), CF/5-FU + Taxol, and Taxol + OXA groups, and received up to 8 cycles of chemotherapy. Treatment efficacy and adverse events were evaluated according to WHO criteria. RESULTS: A total of 180 patients were enrolled from May 2002 to May 2004, and randomized into the 3 groups; each group contained 60 patients. Of the 180 patients, 14 received 2 cycles of chemotherapy, 49 received 4 cycles, and 103 received 8 cycles. Treatment outcomes of 166 cases were evaluable. The response rate (RR) of naive patients or the patients with retroperitoneal lymph node metastasis was significantly higher in CF/5-FU+Taxol and Taxol+OXA groups than in control group (50.00% and 80.00% vs. 20.75%, P<0.05; 65.96% and 85.71% vs. 36.36%, P<0.05). But the RR of the patients with liver metastasis was similar among the 3 groups (28.57% and 39.13% vs. 34.62%, P>0.05). The occurrence rates of nausea/vomiting, anepithymia, stomatitis, and kidney damage were lower in study groups than in control group, but the occurrence rates of myelosuppression and peripheral nerve damage were higher in study groups than in control group. Allergic response occurred in 7 (5.88%) patients in study group, and 3 (2.52%) of them were serious. There was no treatment-related death. CONCLUSIONS: Despite its hematotoxicity, the treatment efficacy of Taxol-based combination regimens on advanced gastric cancer is better than that of CF/5-FU + DDP regimen with tolerable toxicities. We recommend Taxol-based combination regimens as first-line regimens for advanced gastric cancer.

Adult↗
PubMed2004

Extended irreversible thermodynamics modeling for self-heating and dissipation in piezoelectric ceramics.

Self-heating or dissipation of piezoelectric ceramic elements is observed to be severe under dynamic operations even in the linear range. In this paper, a nonequilibrium thermodynamic model is developed to delineate the coupled irreversible mechanical, electric, and thermal processes, which jointly contribute to dissipation. Specifically, additional nonequilibrium state variables, also known as thermodynamic fluxes, are brought in to describe each of these processes. The characteristic relaxation of these processes is modeled. The nonnegative rate of entropy production is found to be in quadratic form of thermodynamics fluxes. The energy balance equation, which governs the transformation between different energy forms, is obtained in the framework of extended irreversible thermodynamics. Using this model, the dissipation of a piezoceramic stack actuator under harmonic electric or mechanical loadings in linear operation range is studied. The harmonic-balance methods are utilized as solution techniques. In contrast to the existing piezoelectric dissipation models, the dissipation by the developed model is verified to nonlinearly depend on operating frequency, with a peak dissipation occurring at some operating frequency that is related to characteristic relaxation of irreversible processes. The measurements of newly introduced parameters are also discussed.

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