Highly ordered microstructures of poly(styrene-b-isoprene) block copolymers induced by solution meniscus

Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3 nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where [111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1 mm². Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation.     

映射半解析边界元法解瞬态弹性动力问题的有关问题

提出了映射半解析边界元法解百轴对称瞬态弹性动力问题时存在解析方向不能正确反映波的传播现象的问题，产生该问题的原因和如何解决该问题的建议。     

Episodic Logic: A comprehensive,natural representation for language understanding

A new comprehensive framework for narrative understanding has been developed. Its centerpiece is a new situational logic calledEpisodic Logic (EL), a knowledge and semantic representation well-adapted to the interpretive and inferential needs of general NLU. The most distinctive features of EL is its natural language-like expressiveness. It allows for generalized quantifiers, lambda abstraction, sentence and predicate modifiers, sentence and predicate reification, intensional predicates (corresponding to wanting, believing, making, etc.), unreliable generalizations, and perhaps most importantly, explicit situational variables (denoting episodes, events, states of affairs, etc.) linked to arbitrary formulas that describe them. These allow episodes to be explicitly related in terms of part-whole, temporal and causal relations. Episodic logical form is easily computed from surface syntax and lends itself to effective inference.     

Role of hepatic resection in surgery for bilateral intrahepatic stones

The effect of phenylephrine-induced reflex parasympathetic stimulation on QT interval and its dispersion was studied in 16 healthy subjects with a history of paroxysmal supraventricular tachycardia, both during sinus rhythm and during atrial pacing. Results demonstrate that rapid reflex parasympathetic stimulation does not influence QT interval duration or QT dispersion, and also emphasize the inappropriateness of Bazett's formula, the need for comparison of QT intervals during identical heart rates, and the importance of analyzing all 12 leads of a standard electrocardiogram when assessing the effects of various interventions on the QT interval.     

InxGa1−xAs (x=0.25–0.35) grown at low temperature

In_xGa_1−xAs (x=0.25–0.35) grown at low temperature on GaAs by molecular beam epitaxy is characterized by Hall effect, transmission electron microscopy, and ultrafast optical testing. As with low temperature (LT) GaAs, the resistivity is generally higher after a brief anneal at 600°C. High-resolution transmission electron microscopy shows all the as-grown epilayers to be heavily dislocated due to the large lattice mismatch (2–3%). When the layers are annealed, in addition to the dislocations, precipitates are also generally observed. As with LT-GaAs, the lifetime shortens as growth temperature is reduced through the range 300–120°C; also, the lifetime in LT-In_xGa_1−xAs is generally shorter in as-grown samples relative to annealed samples. Metal-semiconductor-metal photodetectors fabricated on the material exhibit response times of 1–2 picoseconds, comparable to results reported on GaAs grown at low temperature, and the fastest ever reported in the wavelength range of 1.0–1.3 μm.     

Characterization of the cavity nucleation factor for life prediction under creep-fatigue interaction

It is understood that grain boundary cavitation is one of the detrimental processes for the degradation of materials that reduces the creep-fatigue life at high temperatures. In a previous investigation, a model for life prediction under creep-fatigue conditions was proposed in terms of cavity nucleation and growth. In that model, the cavity nucleation factor (P) was introduced to correlate between the number of cavities and the plastic strain range from which athermal vacancies are generated. It was considered to be a material specific constant which was independent of the experimental conditions. However, in this study, it is found that the cavity nucleation factor is a function of the plastic strain range but is independent of the testing temperature at near 0.5 T _m. In the light of this dependency, a new cavity nucleation factor (P'), is introduced. Using this new cavity nucleation factor (P'), a modified equation for life prediction is proposed, and it is shown that there is good agreement between predicted and experimental lives. Additionally, an interesting approach has been made to find the physical meaning of the new cavity nucleation factor (P'). According to this study, it is suggested that the new cavity nucleation factor, which is regarded as a material specific constant, is found to be strongly related to the density of the grain boundary precipitates with a linear relationship existing between them.     

弹性杆与水下壳体接触冲击的冲击力计算研究

对弹性杆与水下壳体接触冲击问题进行了研究，用有限元法模拟壳体，边界无法模拟无限域流体，通过温面上的耦合条件进行联立求解，文中给出了典型算例，并进行了有关讨论。     

Enhanced direct stiffness method for finite element analysis of textile composites

Traditional homogenization techniques are not useful when the microstructural scale of a material is of the same order of magnitude as the structural scale of a component. Such is the case for many textile composites. Since discrete modeling of the microstructure throughout a component is prohibitively expensive, continuum finite elements are needed which account for the microstructure within a single element. This paper describes a simple substructuring technique for formulating these special elements.     

Serum amyloid P component scintigraphy and turnover studies for diagnosis and quantitative monitoring of AA amyloidosis in juvenile rheumatoid arthritis

OBJECTIVE: To evaluate aspects of the natural history of AA amyloidosis complicating juvenile rheumatoid arthritis (JRA), and its response to therapy with chlorambucil. METHODS: Scintigraphy and 7-day turnover studies were performed in JRA patients with histologically proven (n = 35) or clinically suspected (n = 30) AA amyloidosis, following intravenous injection of 123I and 125I-labeled serum amyloid P component (SAP). Prospective monitoring studies were performed over 2-3 years in 20 patients with amyloidosis. All but 2 amyloidosis patients were treated with chlorambucil. RESULTS: Positive scanning results were obtained in all patients in whom imaging was performed within 12 years of positive biopsy findings of amyloid and in 5 patients with clinically suspected amyloidosis. Negative scanning results with normal SAP metabolism, indicating regression of amyloid, were obtained in 4 patients whose amyloidosis had been in full clinical remission for more than 12 years. Prospective monitoring studies in patients whose JRA-associated inflammatory activity was in remission demonstrated regression of amyloid in 8 patients and no substantial changes in 8 others; however, in 4 further patients with active inflammation, there was accumulation of amyloid. There was a very poor correlation between the amount of amyloid present at a particular site and the resultant organ dysfunction. CONCLUSION: Radiolabeled SAP scintigraphy and turnover studies are useful complementary tools in the diagnosis, screening, and quantitative monitoring of type AA amyloidosis in JRA. The amyloid deposits may progress and/or regress at different rates in different anatomic sites over short periods.