摘要：新冠病毒肺炎疫情期间,口罩成为不可或缺的防控利器和战略物资。如何科学、安全、有效地重复使用口罩,让每一只口罩发挥最大效能,数倍甚至十倍以上地提高防护口罩的有效使用时间,是疫情防控所急需解决的关键科技问题。我们提出了“口罩荷电再生重复使用”的技术方法,并开展了再生口罩性能评价。首先将使用后的口罩浸泡在56℃以上热水中30min进行消毒处理,随后采用普通家用电吹风机等对“失效”的口罩进行吹干荷电处理,使口罩可重新荷电而再生静电效应。对市售的三类典型口罩(一次性医用口罩、医用外科口罩、KN95级防护口罩)进行“热水泡灭毒+荷电再生”处理,实验证明其过滤层微观结构和口罩抗渗水性均无明显变化,再生口罩对非油性颗粒物的过滤效率满足相关口罩指标要求。相关研究结果为新冠病毒肺炎疫情期间的口罩荷电再生重复使用提供了参考。进一步研究了真人佩戴过程对不同初始性能的口罩的性能演变。浙江闰土股份有限公司在2月20日至3月30日期间应用“口罩荷电再生重复使用技术”,将原先每个员工每日发放一个一次性医用口罩,改为每个员工每三日发放一个一次性医用口罩,节约口罩12.25万只,降低了公司的口罩使用量,也确保了防疫工作的正常开展。本文基于真实佩戴口罩的研究,建立了基于荧光纳米颗粒渗透探伤的口罩检测新方法,为可重复使用口罩材料设计、结构优化和性能综合评价提供参考。

摘要：Haze episodes become very frequent in Beijing over the past decade,and such trend is related to favorable weather ***,we project the changes of weather conditions conducive to winter haze episodes in Beijing by 1.5℃ and 2.0℃ global warming using Haze Weather Index(HWI)and data of ensemble simulations from the Community Earth System Model(CESM)low-warming *** to present day(2006–2015),the frequency in winter season is projected to increase by 14% for regular haze episodes(HWI>0)and 21% for severe haze episodes(HWI>1)at the 1.5℃ global *** shows larger increases of 27% for regular and 18%for severe haze events at the 2℃ global *** additional warming of 0.5℃ largely enhances the persistence of weather conditions conducive to haze *** increased temperature contrast between near-surface and mid-troposphere in eastern Asia accounts for 57% and 81% of the change in HWI by 1.5℃ and 2℃ warming,*** increased haze weather potential caused by climate warming,we suggest that additional efforts in emission reductions of carbon dioxide and air pollution are necessary to mitigate haze episodes in Beijing.

摘要：为有效降低雷达回波数据中的冗余,优化雷达回波的传输性能,提出了单周期雷达回波的奇异值分解压缩算法。通过研究雷达回波周期间和周期内的线性相关性,发现回波信号周期内的相关性远大于周期间的相关性,可以通过对单个周期回波数据构造二维矩阵,然后利用奇异值分解来压缩二维冗余性。同时在分析矩阵的行数和列数对压缩性能影响的基础上,建立了以压缩比最大为优化目标、以重构信号的保真度为约束条件的单个周期回波数据的二维矩阵优化构造模型。利用实测的雷达回波数据对算法进行仿真,结果表明算法有效可行,能够有效提高数据的压缩比和重构精度,并且兼顾了实时性,优化了雷达回波信号传输性能。

摘要：库尔特·冯内格特在大学理工科接受教育并在高科技公司从业的经历赋予他独具一格的敏锐洞察力,使他能够意识到并揭示出机械对人类生存条件的威胁。在他的第一部小说《自动钢琴》中,他借鉴了电气自动化领域的分层控制结构设计。一方面,冯内格特运用以来访的国宾布拉德普尔国王为中心的系统表层配置,揭示了机器主导的社会对劳动人民的奴役。另一方面,他采用围绕小说主人公保罗·普罗透斯博士的底层设置,揭示了该社会对精英的监禁及其为了把这种奴役和监禁强加给公众而施行的诡谲手法。小说对工业文明的否定对于新型生态文明意识的形成起到了启蒙作用。

摘要：很多情况下,需要用红外耳温计迅速测量体温。文中介绍了红外耳温计的设计方法,在介绍其工作原理和软硬件设计的基础上,重点介绍了产品设计中关键技术问题的解决方法。按此方法设计出来的红外耳温计基本达到国外同类产品的水平。

摘要：A systemic investigation was done on the chemistry and crystal structure of boundary phases in sintered Ce9Nd21FebalB1 （wt%） magnets. Ce2Fe14B is believed to be more soluble in the rare-earth （RE）-rich liquid phase during the sintering process. Thus, the grain size and oxygen content were controlled via low-temperature sintering, resulting in high coercivity and maximum energy products. In addition, Ce formed massive agglomerations at the triple-point junctions, as confirmed by elemental mapping results. Transmission electron micros- copy （TEM） images indicated the presence of （Ce,Nd）Ox phases at grain boundaries. By controlling the composition and optimizing the preparation process, we successfully obtained Ce9Nd21FebalBx sintered magnets; the prepared magnets exhibited a residual induction, coerciv- ity, and energy product of 1.353 T, 759 kA/m, and 342 kJ/m3, respectively.

摘要：Background:Renal artery stenosis (RAS) is always associated with abnormalities in renal microvascular perfusion (RMP).However,few imaging methods can simultaneously evaluate the degree of luminal stenosis and ***,this study will aim to evaluate the feasibility of using contrast-enhanced ultrasound (CEUS) for assessing both RAS and RMP to achieve a one-stop assessment of patients with suspected renovascular hypertension. Methods:This will be a single-center diagnostic study with a sample size of *** with chronic kidney disease (CKD) and suspected of having resistant hypertension will be *** with Stages 1–3 CKD will undergo CEUS and computed tomography (CT) angiography (CTA).Values obtained by CEUS and CTA for diagnosing low-grade (lumen reduced by <60%) and high-grade (lumen reduced by ≥60%) RAS will be ***,all patients will also undergo radionuclide *** diagnostic value for RAS will be assessed by the receiver operating characteristic curve,including the accuracy,sensitivity,specificity,positive predictive values,negative predictive values,and area under the *** correlation analysis will be performed to assess the association between CEUS findings for RMP and glomerular filtration rate measured by a radionuclide imaging method. Conclusion:The data gathered from this study will be used to evaluate the feasibility of expanding clinical applications of CEUS for evaluation of patients with suspected renovascular hypertension.

摘要：针对复合叶轮式燃油离心泵在设计中的叶轮型线复杂、难以实现快速迭代的问题,提出一种基于改进Bezier曲线的叶轮参数化设计方法,并进行了试验验证及性能仿真分析研究。引入比例系数来约束五点四次贝塞尔样条曲线的控制点参数,并采用该方法设计叶轮轴面轮廓型线。结合辅助叶片偏置设计方法,完成复合叶轮的参数化设计,并对某型燃油离心泵进行设计及三维建模。最后,通过外特性试验验证设计方法和仿真方法的有效性,并将改进Bezier曲线和未改进Bezier曲线设计的复合叶轮结果进行对比。结果表明:仿真与试验结果预测的扬程和效率误差均在5%以内,所提出的设计方法和采用的仿真方法是有效的。相比未改进的Bezier曲线,采用改进Bezier曲线设计的复合叶轮其内部流动更加平稳且水力损失更少。

摘要：音乐民族志这一书写范式在民族音乐学界由来已久,从马氏的《西太平洋的航海者》发源至今,因其对文化事项整体关照之上的真实描述而备受青睐,经历了质疑、重塑等不同的转向,亦在学者们不断地探索实践中经受着效用性的考量。以民族音乐学课堂实践为基础,结合教研实例,通过"教"与"学"互为主体的教研实践在音乐民族志认知与书写方面凸显的问题为着手点,对音乐民族志表述内容与方式的相关问题进行讨论。

摘要：针对输入受限的多旋翼无人机轨迹跟踪问题设计了鲁棒正定不变集.考虑多旋翼无人机的非线性动力学模型、外部不确定干扰以及输入饱和约束等因素,首先设计带有干扰抵消项的非线性控制律以保证无人机轨迹跟踪的稳定性,进而基于线性矩阵不等式(LMIs)构造了鲁棒正定不变集.在所设计的控制律作用下,无人机轨迹跟踪误差一旦进入所构造的不变集则将始终处于该集合内,并最终趋于零.理论推导过程与仿真实验结果均验证了以上特性.