温度梯度对Ti-45Al合金定向凝固组织演化影响的数值模拟

采用基于溶质扩散控制模型结合CA方法对Ti-45Al合金定向凝固过程中温度梯度对显微组织演化影响进行了数值模拟.模拟结果表明,随着温度梯度增加,凝固形态经历了树枝晶→胞/枝混合结构→粗胞晶→细胞晶→超细胞晶的转变,而一次胞/枝晶臂间距随着凝固组织变化不断减小.此外,温度梯度很高时,固液界面处溶质富集程度很小,界面处出现溶质截流.     

硬质合金基体对涂层刀具高速切削镍基高温合金切削性能的影响

采用热常数仪和高温维氏硬度计对Co含量(质量分数)分别为6%和10%的硬质合金进行热学性能与高温力学性能检测,然后用以这2种硬质合金为基体的涂层刀片对镍基高温合金GH4133进行高速车削,采用扫描电镜(SEM)和能谱(EDS)对车削后刀片的磨损区域进行观察和成分分析,研究刀片基体的Co含量对刀具切削性能的影响。研究结果表明,硬质合金中的Co含量由10%降低到6%时,热导率由62.78(W.m)/K升高到84.57(W.m)/K,与此同时同一温度下的高温维氏硬度提高10%左右;YBG202刀片(基体中Co含量为10%)的切削刃与后刀面的磨损均较迅速,而YBG102(基体中的Co含量为6%)刀片后刀面的磨损相对均匀,磨损速率低;基体中的Co含量由10%降低到6%时,刀片的切削寿命提高约3倍。故高速连续切削镍基高温合金时应当尽量选用低Co硬质合金作为刀片的基体。     

阅尽人生五十年——从《太阁立志传》到网页“太阁”

《太阁立志传》有了网页版？这么多年,日本把咱们中国的“三国”翻来覆去地出游戏,现在终于有中国人把日本的历史做成游戏了!这让我们在惊喜之余,也不禁有几分怀疑：这个网页版的《太阁立志》．还有原来的味道吗？是重现日本战国时代的辉煌,还是挂羊头卖狗肉的山寨游戏？     

Cu－Zn－Al合金预贝氏体相变与贝氏体形核研究

本文考察了Ｃｕ－Ｚｎ－Ａｌ合金的预贝氏体相变与贝氏体形核。内耗实验表明预贝氏体相变的主要过程为溶质原子扩散、偏聚；能谱分析揭示预贝氏体相变时存在溶质偏聚引起的溶质原子贫化区与富化区；原位观察证实贝氏体于溶质原子贫化区切变形核。     

“真人版街头霸王”诞生记

7天,168小时……国庆长假怎么度过?选择出门旅行——哪儿都人满为患;选择在家睡觉——宅男宅女无聊地消耗来之不易的假期。或许往常你在做出满意的选择前假期已经结束了,但这次,你有机会利用7天的时间做出属于你的格斗游戏大作!     

Correlates of the shift in heart rate variability with postures and walking by time-frequency analysis

Heart rate (HR) variability derived from electrocardiogram (ECG) can be used to assess the function of the autonomic nervous system. HR exhibits various characteristics during different physical activities attributed to the altered autonomic mediation, where it is also beneficial to reveal the autonomic shift in response to physical-activity change. In this paper, the physical-activity-related HR behaviors were delineated using a portable ECG and body acceleration recorder based on a personal digital assistant and the smoothed pseudo Wigner-Ville distribution. The results based upon eighteen subjects performing four sequential 5-min physical activities (supine, sitting, standing and spontaneous walking) showed that the high-frequency heartbeat fluctuations during supine and sitting were significantly larger than during standing, and that the ratio of low- to high-frequency fluctuation during standing was significantly higher than during supine and sitting. This could be linked with the parasympathetic predominance during supine and sitting, and a shift to sympathetic dominance while standing. During spontaneous walking, the high-frequency fluctuation was significant lower than during supine. The low- to high-frequency ratio decreased significantly from standing to spontaneous walking, which may imply an increased vagal predominance (autonomic effect) or an increased respiratory activity (mechanical effect).     

The effect of head-related transfer function measurement methodology on localization performance in spatial audio interfaces

OBJECTIVE: Four head-related transfer function (HRTF) data sets were compared to determine the effect of HRTF measurement methodology on the localization of spatialized auditory stimuli. BACKGROUND: Spatial audio interfaces typically require HRTF data sets to generate the spatialized auditory stimuli. HRTF measurement is accomplished using a variety of techniques that can require several nearly arbitrary decisions about methodology. The effects of these choices upon the resulting spatial audio interface are unclear. METHOD: Sixteen participants completed a sound localization task that included real-world, broadband stimuli spatialized at eight locations on the horizontal plane. Four different HRTF data sets were utilized to spatialize the stimuli: two publicly available HRTF data sets and two data sets obtained using different in-house measurement systems. All HRTFs were obtained from the Knowles Electronics Mannequin for Acoustics Research. RESULTS: Unsigned localization error and proportion of front/back reversals did not differ significantly across HRTF data sets. Poorest accuracy was observed in locations near the medial (front/back) axis of the listener, mainly because of the relatively large proportions of reversals at these locations. CONCLUSION: This study suggests that the particular generalized HRTF data set chosen for spatialization is of minimal importance to the localizability of the resulting stimuli. APPLICATION: This result will inform the design of many spatial audio interfaces that are based upon generalized HRTFs, including wayfaring devices, communication systems, and virtual reality systems.     

让手游更流畅Android手机提速记

俗话说得好,工欲善其事,必先利其器,这玩游戏也是一样。试想一下,如果你在玩《天天爱跑酷》的时候,看到前面出现了一个大坑,即将破记录的你赶紧点了一下“跳跃键”,但就在这时,屏幕卡了一下……卡了……,卡……,请问这时的你是什么心情？     

ZA27合金的淬火时效特性

利用本试验设计的热效应装置研究了ＺＡ２７合金淬火时效过程,结果发现,ＺＡ２７合金时效曲线早期阶段出现了大小不等的温度峰。与对应条件下硬度曲线比较表明,淬火后时效温度不同,脱溶机理亦不尽相同。