高强Q690钢柱高温下轴心受压局部稳定设计方法

局部屈曲是钢结构构件的一种破坏模式,钢结构发生局部屈曲破坏时,屈曲应力小于钢材的屈服强度。为了研究高温下高强Q690钢柱的局部稳定性能,采用有限元软件ABAQUS建立有限元模型,模型采用其他学者完成的Q460钢柱轴心受压局部屈曲试验进行验证,考虑宽厚比、温度、初始缺陷、残余应力和翼缘与腹板之间相互作用的影响,对高强Q690钢柱进行参数分析。研究结果表明：宽厚比对局部屈曲有显著影响,宽厚比的增大导致试件极限承载力的降低;初始缺陷和残余应力对局部屈曲应力有较大影响,且试件的极限承载力随着温度的升高而明显下降。基于有限元分析结果提出了适用于高强Q690钢柱高温下的局部稳定设计方法和宽厚比限值,并与GB 50017-2017、Eurocode 3和ANSI/AISC 360-10中的设计方法进行了比较。     

Thermodynamic and transport property models for carbon capture and sequestration (CCS) processes with emphasis on CO2 transport

Carbon capture and sequestration (CCS) is one of the most promising technologies for the reduction of carbon dioxide (CO₂) concentration in the atmosphere, so that global warming can be controlled and eventually eliminated. A crucial part in the CCS process design is the model that is used to calculate the physical properties (thermodynamic, transport etc.) of pure CO₂ and CO₂ mixtures with other components.     

Lower confidence limits for process capability indices Cp and Cpk when data are autocorrelated

Many organizations use a single estimate of C_p and/or C_pk for process benchmarking, without considering the sampling variability of the estimators and how that impacts the probability of meeting minimum index requirements. Lower confidence limits have previously been determined for the C_p and C_pk indices under the standard assumption of independent data, which are based on the sampling distributions of the index estimators. In this paper, lower 100(1‐α)% confidence limits for C_p and C_pk were developed for autocorrelated processes. Simulation was used to generate the empirical sampling distribution of each estimator for various combinations of sample size (n), autoregressive parameter (?), true index value (C_p or C_pk), and confidence level. In addition, the minimum values of the estimators required in order to meet quality requirements with 100(1‐α)% certainty were also determined from these empirical sampling distributions. These tables may be used by practitioners to set minimum capability requirements for index estimators, rather than true values, for the autocorrelated case. The implications of these results for practitioners will be discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Defect localization induced by hot carrier injection in short-channel MOSFETs: Concept, modeling and characterization

Key aspects related to the localization of the hot-carrier induced damage in short channel MOSFET's are reviewed. Emphasis is put on the analysis, modeling and characterization of the degradation of device parameters caused by defects created locally beside the drain junction. Numerical simulations as well as analytical models predicting the post-stress performance are presented, compared and their limits of validity highlighted. Relevant experimental results, concerning the evolution of the static characteristics I_D(V_G, V_D) during transistor aging, are thoroughly discussed and efficient methods for the extraction of the defective region parameters are proposed. More specific techniques (charge pumping, noise spectroscopy, floating gate current, gated diode leakage), used for the characterization of aging induced defects, are evaluated from the point of view of their capability to cope with the localized nature of the defects. The merits of silicon on insulator structures and other technological solutions proposed for the attenuation of hot carrier effects are briefly commented.     

The effect of endoscopic sinus surgery on mucociliary clearance in patients with chronic sinusitis

In a prospective study 20 patients suffering from recurrent, therapy-refractory menorrhagias were pre-treated for endometrial ablation after exclusion of intrauterine abnormalities and histological pathology. Two injections of GnRH-analogues (3.75 mg leuprorelinacetate depot, Enantone Gyn, Takeda Pharma GmbH Aachen, Germany). Two weeks after the last injection a hysteroscopic surgery by roller-ball-techniques was performed in 10 patients and a balloon-thermocoagulation by Cavaterm-technique (Wallsten Medical, Morges, Schweiz) was performed in 10 patients. Both patients groups were comparable according to age and anamnesis. In a follow-up of 9 to 15 months we found about identical results. All 20 patients were satisfied with the treatment. The Cavaterm-coagulation is in comparison to the operative hysteroscopy a simple method for endometrial coagulation, and can also be used by an hysteroscopically inexperienced gynaecologists with simple technical equipment. In strict indication the Cavaterm-coagulation is a simple method of endometrial ablation in many patients.     

Méthode expérimentale de détermination de l'énergie de rupture des bétons ordinaires

The aim of this paper is to determine the failure energy of ordinary concretes. This energy is considered as an intrinsic characteristic of the cracked material. RILEM recommendations related to three-point bending tests on notched beams have been studied and applied. This experimental model needs appropriate equipment working in controlled displacement mode. The controlled force test is generally unsteady. The result is that tensile curves (σ-w) are hardly achieved until the end of the test. In numerical modelling of the failure, it is precisely the descending branch of the curve (σ-w) which characterises the crack material because the stress reduces, whereas the crack opening increases (strain-softening). The tests carried out are failure tensile tests in mode I. The results obtained are ultimate loads of failure related to three-point bending notched specimens. A prediction method of failure energy based on intensity factor design of critical stress has been used. The latter is the result of experimental models interpolation in the field of failure mechanics. The results obtained are satisfactory and will allow the researchers who wish to simulate the crack by finite element modelling to use these results. For this purpose, experimental curves (σ-w) could be approximated by using linear, two-linear or exponential straight line providing that this failure energy remains steady.     

Glyceride metabolism in the myopathic hamster

Analysis of plasma lipids of 30- and 185-day-old BIO 82.62 myopathic hamsters and age-matched normal controls revealed a decrease in only the concentration of cholesteryl esters of 185-day-old diseased animals. Measurement of lipoprotein lipase (LPL) activity in heart, muscle, and adipose tissue showed no difference between the activity of the enzyme in the heart and muscle of the cardiomyopathic hamsters and that of the age-matched controls. In adipose tissue, however, LPL activity was depressed in the diseased animals in both age groups. No difference was found in the activity of hormone sensitive lipase. Incorporation of sn[U-¹⁴C] glycerol-3-phosphate into total lipids was found to be depressed in homogenates of heart, muscle, and adipose tissue but unchanged in liver homogenates of diseased animals. It was concluded that the decrease in the capacity to synthesize glycerides, rather than limiting substrate concentrations, could be the cause of the decrease in the lipid content in some tissues of the cardiomyopathic hamster.     

Examining coping methods with stressful interpersonal events experienced by Muslims living in the United States following the 9/11 attacks.

Pargament's (1997) religious coping theory was used to examine the methods of coping with stressful interpersonal events experienced by 138 Muslims living in the United States following the 9/11 attacks. The large majority of participants reported experiencing at least one stressful interpersonal event after the 9/11 attacks related to being Muslim; the most common incidents were hearing anti-Muslim comments, undergoing special security checks in airports, facing discriminatory acts, and being verbally harassed. Participants used both religious (i.e., positive religious coping, negative religious coping) and nonreligious (i.e., reaching out, isolation) methods to deal with these stressful interpersonal events. Positive religious coping and reaching out were related to posttraumatic growth; negative religious coping was associated with depression; and isolation was tied to both depression and angry feelings. The large majority of participants did not view the negative interpersonal events they experienced after the 9/11 attacks as a sacred loss, but a significant percentage did consider these events as a desecration. Further, viewing these incidents as a desecration was tied to posttraumatic growth, but this link was partially mediated by positive coping methods. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Novel Nano Structure for Green Energy Harvesting at 10 μm Thermal Radiation

In recent years, the potential of renewable green energy sources has been extensively studied. The proven technology which is photovoltaic solar cells strictly depends on daylight and produces low-efficiently. To overcome the restrictions, one technology studied is through harvesting the thermal radiation energy which can provide a 24-hour energy source. The continuity of energy sources promises very good energy conversion especially for military applications. This article presents a new structure that can harvest the abundant thermal radiation energy into usable energy at the wavelength of 10 m. A rectangular structure with a perturbation slit was designed to integrate with a rectifier circuit for green energy conversion. The slit tunnel junction guided the electromagnetic field into a junction where the energy could be collected and converted. An enhancement factor of approximately 110.6 can be achieved by a perturbation slit length of 1.0 m. The results extracted from the proposed design promise a better candidate to overcome the disadvantages of photovoltaic solar cells for energy harvesting devices.     

Lognormal switching times for titanium dioxide bipolar memristors: origin and resolution

We measured the switching time statistics for a TiO(2) memristor and found that they followed a lognormal distribution, which is a potentially serious problem for computer memory and data storage applications. We examined the underlying physical phenomena that determine the switching statistics and proposed a simple analytical model for the distribution based on the drift/diffusion equation and previously measured nonlinear drift behavior. We designed a closed-loop switching protocol that dramatically narrows the time distribution, which can significantly improve memory circuit performance and reliability.