科创中国

为了实现辐射监测γ相机成像的目的,采用电路理论分析和Matlab仿真方法,设计了一种峰值保持电路.做了辐射监测实验,获得了电路可准确、实时捕捉脉冲信号峰值的结果,得到设计方案可行的结论.该电路具有结构简单、调试方便、性能优良等特点,可广泛应用于各种脉冲分析系统.

经典的BayesShrink通过软阈值函数对小波系数进行修正,使得原小波系数和修正小波系数存在恒定偏差,降低了去噪图像质量。文章利用噪声系数幅值随小波系数幅值的增大而相对减小的特点,构造了具有伸缩性的自适应阈值函数,该方法克服了软阈值函数产生的恒定偏差,依赖小波系数幅值对原始系数和修正系数间的恒定偏差自适应调节。伸缩因子m根据不同图像特点采用二分法自适应寻得最优值。实验结果表明改进后的阈值函数相比经典软阈值函数去噪效果较优。

本文提出了一种应用于WiMAX的小型化差分微带天线,并通过在辐射贴片刻蚀U型缝隙的方法实现天线的小型化.与传统的半波长天线相比,该天线的尺寸为15 mm*15 mm(0.38λg*0.38λg).为了改善天线的带宽性能,设计了一种新型的哑铃型开口环金属线复合周期结构的左手材料,并将左手材料作为天线的覆层.仿真和测量结果表明:覆层左手材料的小型化差分微带天线的带宽为8.5%(3.4 GHz~3.7 GHz),峰值增益为3.8 dBi.

We?examine?the?conservation?status?of?Africa's?"Big?Five":?lion,?leopard,?buffalo,?black?and?white?rhinoceros?and?elephant,?and?the?role?of?behavioral?knowledge?in?their?conservation.?Efforts?to?conserve?these?flagship?species?consist?of?in?situ?conservation,?captive?breeding?and?reintroductions.?With?a?few?exceptions,?we?find?limited?evidence?that?knowledge?of?behavior?informs?conservation?programs?targeted?at?these?species.?For?management?in?the?wild,?knowledge?of?infanticide?and?ranging?can?provide?guidelines?for?realistic?hunting?quotas?and?corridors?between?protected?areas,?respectively.?For?ex?situ?and?reintroduction?programs,?behavioral?knowledge?is?chiefly?focused?on?improved?animal?husbandry.?Despite?a?formidable?understanding?of?these?species'?behavior,?the?practicalities?of?using?such?knowledge?may?be?diminished?because?exploitation?of?these?species?is?so?forceful?and?the?bulk?of?efforts?aimed?at?conserving?these?species?(and?indeed?most?other?African?species)?are?primarily?in?situ?where?behaviorally?driven?interventions?are?limited.?Our?comparative?findings?suggest?that?behavior?has?been?of?rather?narrow?use?in?the?conservation?of?these?flagship?species?[Current?Zoology?60?(4):?486--499,?2014].

为解决高瓦斯工作面双U型巷道布置中煤柱损失大、相邻工作面复用回采巷道维护困难的难题,综合采用理论分析、数值计算和现场试验的方法,研究得到煤柱宽度对相邻两工作面之间煤柱内复用巷道围岩应力分布和变形特征的影响规律:随着巷道一侧煤柱宽度的增加,巷道围岩垂直应力峰值向一侧移动,并逐渐远离巷道;当巷道一侧煤柱较小时,巷道以窄煤柱帮变形和顶板下沉为主,随着煤柱宽度增加,底鼓增大并成为巷道主要变形.以煤柱内应力峰值比值为指标,分析煤柱宽度与巷道稳定性的关系,并将不同宽度煤柱进行了稳定性分区.研究成果成功应用于工程实践,为类似条件下巷道布置提供依据.

Acoustic?interference?can?impede?effective?communication?that?is?important?for?survival?and?reproduction?of?animals.?In?response?to?acoustic?interference,?some?animals?can?improve?signalling?efficacy?by?altering?the?structure?of?their?signals.?In?this?study,?we?played?artificial?noise?to?46?male?spring?peepers?Pseudacris?crucifer,?on?their?breeding?grounds,?and?tested?whether?the?noise?affected?the?duration,?call?rate,?and?peak?frequency?of?their?advertisement?calls.?We?used?two?experimental?noise?treatments?that?masked?either?the?high-?or?low-frequency?components?of?an?average?advertisement?call;?this?allowed?us?to?evaluate?whether?frogs?adaptively?shift?the?peak?frequency?of?their?calls?away?from?both?types?of?interference.?Our?playback?treatments?caused?spring?peepers?to?produce?shorter?calls,?and?the?high-frequency?noise?treatment?caused?them?to?lower?the?frequency?of?their?calls?immediately?after?the?noise?ceased.?Call?rate?did?not?change?in?response?to?playback.?Consistent?with?previous?studies,?ambient?temperature?was?inversely?related?to?call?duration?and?positively?related?to?call?rate.?We?conclude?that?noise?affects?the?structure?of?spring?peeper?advertisement?calls,?and?that?spring?peepers?therefore?have?a?mechanism?for?altering?signal?structure?in?response?to?noise.?Future?studies?should?test?if?other?types?of?noise,?such?as?biotic?or?anthropogenic?noise,?have?similar?effects?on?call?structure,?and?if?the?observed?changes?to?call?structure?enhance?or?impair?communication?in?noisy?environments?[Current?Zoology?60?(4):?438-448,?2014].

继电保护技术的发展,迫切需要运用技术监督这一科学的管理方法,提高继电保护工作的有效性,减少盲目性.继电保护应通过技术监督手段,利用科学的方法,对设备内部微观变化过程进行监督检查和量化分析,判断其安全程度,采取预防性措施,有效地控制变化速度,使设备在预期的时间内保持良好的状态和安全运行.

本文分析了压敏电阻、瞬态抑制二极管、静电保护元件、陶瓷气体放电管、玻璃放电管、半导体放电管等电路浪涌保护器件的特性、特点和选用方法,并汇总作了性能比较.

通过宏达煤矿保护层选择、本层与邻近层瓦斯预抽和卸压拦截抽、采空区抽采等防突与防灾研究,实现了强突出煤层群安全生产,解决了强突出煤层群不能采取上保护层或下保护层时首采工作面瓦斯治理这一世界性难题,提供了瓦斯灾害严重的突出矿井实现安全生产的又一有效方法.

11月5日,中国联通携手终端产业链合作伙伴在四川成都举行"创新合作、共赢4G"-中国联通双4G领先计划产业链高端峰会.中国联通常小兵董事长、姜正新副总经理、熊昱副总经理出席大会.国内外知名芯片商、终端厂商、国代商、操作系统商、渠道合作伙伴与互联网合作伙伴等产业链各领域负责人逾千人参加了盛会.常小兵表示,自2013年12月获得TD-LTE 4G牌照、特别是今年6月获批开展LTE混合组网试验以来,中国联通着力打造峰值速率100Mbps和150Mbps的"双百兆"网络.这次发布"双4G领先计划",就是让产业链各方共同分享中