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81.
We describe a system of coupled bosonic wells by means of the Bose-Hubbard model. Its dynamics is investigated via the time-dependent variational principle and coherent states. Some exact solutions of the dynamics, which have a vortex-like structure, are explicitly found, and used together with semiclassical requantization to describe the dynamics in the Mott insulator regime.  相似文献   
82.
The effective friction coefficient of rock avalanches diminishes gradually as a function of the avalanche volume. Large rock avalanches can reach run-out distances as long as ten times the fall height, despite the fact that the physics of friction would indicate a run-out only a little greater than the fall height. Numerous suggestions have been put forward to explain this remarkable departure from the predictions of both small-scale experiments and basic theory. It is shown here that accounting for rock fragmentation within the avalanche in combination with the presence of water, leads to results in line with the data.  相似文献   
83.
Vittorio Ghergia 《Sadhana》1992,17(3-4):411-430
Starting from the present state-of-the-art of discrete devices up to the realization of monolithic semiconductor integrated prototypes, an overview of optoelectronic devices for telecommunications is given. Among discrete devices single frequency lasers, tunable and multi-sectionDFB lasers andPIN andAPD photodiode detectors are analysed, including the use of new technologies in progress for a second generation of devices. On the future perspective ofIBCN distribution networks, some economics of the hybrid and monolithic form of integration are attempted. Finally a short outline of the most recent achievements in monolithic integration is presented, taking into particular consideration the activities in this field byEEC ESPRIT andRACE programmes.  相似文献   
84.
High-yield production of graphene by liquid-phase exfoliation of graphite   总被引:11,自引:0,他引:11  
Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.  相似文献   
85.
86.
The coherent beam instabilities in circular accelerators are explained in terms of simple concepts of feedback devices. The notion of coupling impedance is introduced and interpreted by means of engineering circuit analysis. The condition of stability for the coherent motion is given in terms of the coupling impedance and accelerator and beam parameters.  相似文献   
87.
Rapid sequestration and prolonged retention of intravenously injected nanoparticles by the liver and spleen (reticuloendothelial system (RES)) presents a major barrier to effective delivery to the target site and hampers clinical translation of nanomedicine. Inspired by biological macromolecular drugs, synthesis of ultrasmall (diameter ≈12–15 nm) porous silica nanoparticles (UPSNs), capable of prolonged plasma half‐life, attenuated RES sequestration, and accelerated hepatobiliary clearance, is reported. The study further investigates the effect of tumor vascularization on uptake and retention of UPSNs in two mouse models of triple negative breast cancer with distinctly different microenvironments. A semimechanistic mathematical model is developed to gain mechanistic insights into the interactions between the UPSNs and the biological entities of interest, specifically the RES. Despite similar systemic pharmacokinetic profiles, UPSNs demonstrate strikingly different tumor responses in the two models. Histopathology confirms the differences in vasculature and stromal status of the two models, and corresponding differences in the microscopic distribution of UPSNs within the tumors. The studies demonstrate the successful application of multidisciplinary and complementary approaches, based on laboratory experimentation and mathematical modeling, to concurrently design optimized nanomaterials, and investigate their complex biological interactions, in order to drive innovation and translation.  相似文献   
88.
The present study examined the developmental course of perceived efficacy for self-regulated learning and its contribution to academic achievement and likelihood of remaining in school in a sample of 412 Italian students (48% males and 52% females ranging in age from 12 to 22 years). Latent growth curve analysis revealed a progressive decline in self-regulatory efficacy from junior to senior high school, with males experiencing the greater reduction. The lower the decline in self-regulatory efficacy, the higher the high school grades and the greater the likelihood of remaining in high school controlling for socioeconomic status. Reciprocal cross-lagged models revealed that high perceived efficacy for self-regulated learning in junior high school contributed to junior high school grades and self-regulatory efficacy in high school, which partially mediated the relation of junior high grades on high school grades and the likelihood of remaining in school. Socioeconomic status contributed to high school grades only mediationally through junior high grades and to school drop out both directly and mediationally through junior high grades. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
89.
Quality function deployment (QFD) is a process that has been used for managing the development of new manufactured products. In this process, both spoken and unspoken needs of the customers are determined, prioritized, and translated to design parameters. Such design parameters are assigned specific target values and are frequently checked against customers’ needs throughout the development cycle to ensure customers’ satisfaction with the end product. This paper describes a pilot study in which QFD was implemented in a design-construction project. The project scope involved the preparation of a conceptual design for a modern large-size classroom for college students. The design was intended to become a model for the university’s future classrooms. The study proved that QFD could be successfully adopted in engineering-construction projects. However, the study identified a number of implementation challenges. In addition, more applications are necessary to take the process throughout the full project delivery cycle, as the pilot study involved only the preliminary engineering and conceptual design phase.  相似文献   
90.
Since the beginning of the last century, when Freud introduced the couch in the psychoanalytic room, a number of “objects” have been removed or renovated, yet the couch has almost always remained in place, at least officially. This article has two distinct aims. The first is to offer a reconstruction of the psychoanalytic history of this element of the setting. The second is to rethink the couch, saving it from being reduced to a mere icon. Recent contributions coming from affective neurosciences, infant research, and psychotherapy research seem to question the utility of this element and the nature of the very mechanisms of its therapeutic action. The authors wonder whether the use of the couch is primarily protective for the therapist rather than necessarily helpful for all patients. Taking into account these observations implies bringing the couch out from a silent dimension and reflecting on its role in the conception of therapeutic action and mental functioning. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
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