多孔氧化铝陶瓷气孔率对强度的影响

加入不同量的碳粉作造孔剂,挤压成型、烧结,获得气孔率20%~55%的多孔氧化铝陶瓷。研究了气孔率及烧结程度对强度的影响。对试样的强度与气孔率按不同方程拟合.结果表明:当烧结程度较低时,强度(σ)与气孔率(ρ)的关系对经验方程σ=σ₀(1-ρ)^m的拟合结果最好;当烧结程度较高时,强度与气孔率的关系更符合经验方程σ=σ₀exp(-bρ)。经验常数m,b,σ₀与烧结程度有关。随着烧结程度的提高,这些值下降。     

立体深度运动引发的立体视觉疲劳的脑电评估

3D技术的发展受到其引发的不舒适感的限制,长时间观看立体显示影像将会引起立体视觉疲劳,一种客观评价立体视觉疲劳的有效指标亟待提出.本文利用EEG (electroencephalography)三个频带θ(4~8 Hz)、α(8~13 Hz)、β(13~22Hz)的相对能量及其能量比值E_{(α+θ)/β、Eα/β}、E_{(α+θ)/(α+β)}在八个不同脑区及整个脑区的54个指标作为备选,借助配对t检验、灰色关联度分析(GRA)、支持向量机(SVM),最后得出指示由立体深度运动引发的视觉疲劳的最佳脑电指标为:顶区E_α/β.并比较了三个频带相对能量在不同疲劳状态的变化:疲劳状态下,α频带明显上升(p < 0.01),β频带明显下降(p < 0.01),θ频带保持稳定.     

缺口小裂纹的疲劳扩展速率

将复型技术应用于疲劳小裂纹扩展试验中的裂纹长度测量。在等载荷比R=0.1、不同平均载荷水平影响的疲劳条件下,板试样V型缺口小裂纹疲劳扩展速率做了试验测试;通过结果分析,提出了缺口小裂纹疲劳扩展速率表达式,并以ε_P为控制参数,求出45^*钢的计算式。     

干涉型Al-N-O选择性吸收表面的研究

利用Al-N-O选择性吸收层之间产生的干涉效应,改善吸收表面的光学性能(吸收率α和发射率ε).通过工艺实验确定了2种不同金属填充因子的双吸收层结构.与多层渐变吸收表面相比双吸收层结构吸收表面具有膜系结构简单、高温下性能稳定、发射率较低等优点.吸收表面的吸收率α为0.93~0.95,发射率ε(353K)为0.04~0.06.     

GH132合金疲劳蠕变交互作用下裂纹扩展速率研究

通过对650℃、不同应力条件下GH132合金的裂纹扩展速率的测定结果表明:
（1）由于GH132合金的蠕变与疲劳裂纹的扩展机构不同,使得前者有更大的环境敏感性。
（2）在疲劳蠕变交互作用条件下,裂纹的扩展过程受K_max及ΔK共同控制(K_eq=K_max+αΔK)。通常的ΔK描述法已不能全面解释裂纹扩展速率与寿命之间的对应关系。     

FeNiCrAl合金的显微组织和力学性能

对FeNiCrAl合金显微组织和力学性能的研究表明：[Ni]/[Cr]0.9（摩尔比）的合金以γ相为基体,[Ni]/[Cr]（摩尔比）＝0.6～0.8和0.6的合金分别以γ十α双相和α相为基体,合金在不同温度热处理后,由于相的析出或溶解,显示出不同的力学性能.     

炼钢交流电弧炉工作电抗模型

研究了炼钢交流电弧炉在冶炼期间电弧的电气特性,建立了交流电弧炉工作电抗模型,分析了电炉控制参数β、设备线路特征γ、废钢条件及冶炼不同阶段α等对操作电抗的影响.     

凝固条件对AlSi7Mg合金半固态加热时组织的影响

利用电阻炉研究了凝固条件对AlSi₇Mg 合金半固态加热时组织的影响.研究表明:电磁搅拌的AlSi₇Mg 合金在589或597℃下保温,在较短的时间内(5~10 min),共晶体即可重熔,α相可转变为球状,而且保温温度越高,试样共晶体重熔和α相球化的过程越快;相比较,未电磁搅拌的细小枝晶的AlSi₇Mg 合金在同样的加热温度下,即使保温60min,也无法获得完全球状α相的半固态组织.     

单压下类岩材料有序多裂纹体的宏观力学性能

用高强度白水泥及石膏等类岩材料有序多裂纹模型进行了大量单向加压实验,得出了单压时宏观等效强度σ_e,等效弹性模量E_e及泊松比μ_e随裂纹群倾角α的变化规律.在一定程度上考虑了裂纹密度对宏观力学性能的影响.综合实验结果与理论分析,给出了多裂纹体强度特征曲线σ_e-α.     

纳米复合（NdDy）2（FeNb）14B/α-Fe永磁合金

采用单辊急冷法并晶化退火制备了高剩磁、高矫顽力和高磁能积的(NdDy)₂(FeNb)₁₄B/α-Fe纳米复合永磁合金,其最佳磁性能分别为B_r=1.02 T,H_ci=702 KA/m,(BH)_max=134 KJ/m³.合金的组织结构由硬磁相(NdDy)₂(FeNb)₁₄B和软磁相α-Fe在纳米级范围内复合而成.两相的平均晶粒尺寸为30nm.该种合金优异的磁性能起源于纳米晶硬磁相和软磁相之间的磁交换耦合作用.     

基于光电容积脉搏波的有限空间生理疲劳测量

通过有限空间100 min极限载人实验,提出了基于光电容积脉搏波(PPG)的客观疲劳测量方法并开发了光电容积脉搏波信号特征参数提取算法用来掌握生理疲劳的血液动力学与循环系统变化特征.研究结果表明,人体出现生理疲劳时,光电容积脉搏波信号平均周期显著大于未疲劳状态(p<0.001),血管阻力增大,每搏射血量明显下降;计算了未疲劳与疲劳状态下光电容积脉搏波信号的两种复杂度(KC复杂度和高阶KC复杂度)发现,两种复杂度计算结果一致,均为未疲劳时波形比疲劳时波形更平稳.因此表明光电容积脉搏波信号能够捕捉到疲劳状态的生理变化,解决了生理疲劳的客观测量与快速判断问题.     

Neuroticism's importance in understanding the daily life correlates of heart rate variability.

Individual differences in high-frequency heart rate variability (HRV) have been conceptualized in terms of a greater capacity to self-regulate problematic outcomes, but have also been conceptualized in terms of greater moment-to-moment flexibility. From a self-regulation perspective, higher HRV should be inversely correlated with trait neuroticism and problematic daily outcomes. From a flexibility perspective, high HRV should result in more state-like functioning—that is, functioning that is more contextual and less trait-like in nature. In the latter case, HRV and trait neuroticism may interact to predict problematic outcomes such that neuroticism should be a less consequential predictor at higher levels of HRV. The flexibility perspective was systematically supported in a daily experience-sampling protocol. Implications focus on theories of neuroticism and HRV. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heart rate variability, the autonomic nervous system, and neuroeconomic experiments.

Measuring the activity of the autonomic nervous system may yield insights into individual stress levels. One small, nonintrusive instrument for collecting such data is a high-resolution heart rate monitor that allows measurement of heart rate variability (HRV). This complements brain-scanning methods and increases the number of participants that can be studied simultaneously. Combining HRV data with recorded data on the decisions made in experimental games throws light on how different individuals react in (economic) decision-making situations. This article therefore introduces the HRV measurement method and, using data from an ultimatum bargaining experiment in a laboratory environment, illustrates its application in experimental economic research. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

不同应力上限和加载速率下的黄砂岩疲劳特性研究

为研究黄砂岩单轴疲劳加载的特性,开展了不同应力上限和加载速率下的单轴疲劳荷载试验。试验结果表明：黄砂岩的疲劳试验曲线受到单轴压缩应力—应变曲线的控制,疲劳极限变形与峰后对应变形一致;砂岩疲劳过程的不可逆变形和耗散能密度均具有三阶段演化规律,依据倒“S”型损伤模型,验证了黄砂岩疲劳损伤三阶段演化规律;分析认为三阶段规律的本质是砂岩的塑性变形和内部孔隙微裂纹生成以及扩展速度的不同所呈现的结果。研究表明应力上限和加载速率对疲劳寿命有显著影响,根据所得应力—寿命公式,可以估计砂岩在一定条件下的疲劳寿命。     

Effects of increased heart rate on intellectual performance.

A significant correlation found in a pilot study between heart rate and digit Symbol performance was utilized to investigate effects of type of arousal induction on performance. 60 Ss were arranged in a 3 X 2 factorial design, divided into high and low drive via heart rate. Ss first performed on a Digit Symbol task; followed by a frustrating experience, physical exertion, or nonfrustrating task; followed by readministration of an alternate form of the 1st Digit Symbol problem. The results showed that the relation between activation and performance, in most instances followed the hypothetical inverted U function. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social interaction moderates the relationship between depressive mood and heart rate variability: Evidence from an ambulatory monitoring study.

Objective: There is considerable evidence that depressive mood is related to lower parasympathetic control of the heart, thus increasing cardiovascular risk. However, little is known about social factors (e.g., social affiliation) that might moderate this relationship. Design: The authors examined whether cardiac autonomic control in healthy individuals with depressive symptoms could be altered by social interaction. Therefore, the authors conducted a 22-hr ambulatory monitoring study with a sample of 63 adults. Main Outcome Measures: Depression was assessed by questionnaire. Heart rate, heart rate variability (HRV), physical activity, and negative affect were recorded throughout one day via portable monitoring devices. Results and Conclusion: Multilevel analyses revealed that depression was related to elevated negative affect and higher heart rate throughout the day. Moreover, there was a tendency toward lower HRV in individuals with higher depression scores. This association, however, was moderated by social context. When depressive participants were alone they evidenced lower HRV and higher negative affect, but not when they were engaged in social interactions with a partner, family members, or friends. These findings suggest that the relation between depression and cardiac autonomic control could be altered by social interaction, thus possibly buffering adverse health effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors influencing mental workload indexes

Several findings of the author's own mental workload research are reviewed. Especially, factors, except task demand, influencing mental workload indexes are discussed. First, an experiment using the National Aeronautics and Space Administration Task Load Index (NASA TLX) is reviewed and the effects of a prior task load on a subsequent subjective workload are described. In a physiological measures section, the low reliability of the heart rate variability (HRV) parameters when the subjects' respiration pattern are highly irregular, and the existence of low sweat respondent, although perspiration seems to be sensitive to the workload, are indicated. Furthermore, results of the task specific physiological responses and of a HRV parameter affected by the individual characteristics, like type A behavior pattern, are shown. Discrepancy between autonomic nervous system activity measures may be solvable by introducing a new concept of autonomic space (synergism of sympathetic and parasympathetic nervous system). Finally, the need for strategies of data management concerning the individual differences is emphasized.     

Heart rate variability in coronary artery disease

Heart rate variability (HRV) reflects the modulation of cardiac function by autonomic and other physiological systems, and its measurement from ambulatory electrocardiograph (ECG) recordings is a useful method for both clinical and scientific purposes. Heart rate variability can be measured by several linear and non-linear methods, and various methods can give different information on neural and other physiological influences on the heart. Heart rate variability is abnormal in various settings of ischaemic heart disease, and the most important current application of HRV analysis in clinical cardiology is its measurement in postinfarction patients, in whom abnormal HRV indicates an increased risk of cardiac mortality. Future research may expand the clinical utility of HRV measurement to other clinical situations.     

Finding groups using model-based cluster analysis: Heterogeneous emotional self-regulatory processes and heavy alcohol use risk.

Model-based cluster analysis is a new clustering procedure to investigate population heterogeneity utilizing finite mixture multivariate normal densities. It is an inferentially based, statistically principled procedure that allows comparison of nonnested models using the Bayesian information criterion to compare multiple models and identify the optimum number of clusters. The current study clustered 36 young men and women on the basis of their baseline heart rate and heart rate variability (HRV), chronic alcohol use, and reasons for drinking. Two cluster groups were identified and labeled the high alcohol risk and normative groups. Compared to the normative group, individuals in the high alcohol risk group had higher levels of alcohol use and more strongly endorsed disinhibition and suppression reasons for use. The high alcohol risk group showed significant HRV changes in response to positive and negative emotional and appetitive picture cues, compared to neutral cues. In contrast, the normative group showed a significant HRV change only to negative cues. Findings suggest that individuals with autonomic self-regulatory difficulties may be more susceptible to heavy alcohol use and use of alcohol for emotional regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemodynamic and autonomic effects of intravenous saterinone in patients with chronic heart failure

In this study, the hemodynamic and neurohumoral/autonomic effects of intravenous saterinone (a selective phosphodiesterase type III inhibitor, with additional alpha 1-blocking properties) were evaluated. In a double-blind, placebo-controlled design, 36 patients with moderate to severe heart failure were studied (saterinone, n = 24; placebo, n = 12). Invasive hemodynamic measurements, by using right-heart catheterization, were performed, as well as measurement of plasma neurohormones and analysis of heart rate variability (HRV), to study drug influences on neurohumoral activation and autonomic tone. Systemic vascular resistance significantly decreased during saterinone infusion, accompanied by a decrease in systemic blood pressure (both p values < 0.05) and an increase in heart rate (p = 0.05). Filling pressures also decreased during saterinone, but this was statistically significant only for pulmonary capillary wedge pressure, whereas the cardiac index remained unaffected. Plasma neurohormones (norepinephrine, epinephrine, and renin activity) were not significantly influenced by saterinone. HRV analysis revealed no significant effect of saterinone on autonomic tone. These results suggest that intravenous saterinone has a significant vasodilating effect in patients with moderate to severe chronic heart failure (CHF), without exerting an adverse effect on the autonomic nervous system, as demonstrated by assessment of plasma neurohormones and HRV analysis.