Natural surface design for sliding mode control with multiple discontinuous inputs

It is well known that sliding mode control is based on the definition of an invariant manifold, where the system dynamics are forced to in a finite time. Such a manifold is somewhat arbitrarily defined, as long as the system dynamics are stable on it. Computational and control effort may vary depending on selected manifold. Obviously, if a system has naturally acceptable stable dynamics around a desired equilibrium point, no control is needed unless uncertainties or disturbances are present. It would be desirable that if such a system had uncertainties or disturbances, the control effort be designed only to overcome the effect of such factors. For a system with first order dynamics and affine control input, designing a sliding mode control overcoming only such uncertainties or disturbances is a trivial task. When a higher order dynamics system is involved, unit control may be used, where the input control signals are not discontinuous, but when only discontinuous control inputs are available, a design approach is not readily available. In this paper, taking advantage of the natural stable dynamics of a system, a sliding mode control approach is introduced for designing multiple discontinuous control inputs, where the control effort overcomes only uncertainties, disturbances or unstable dynamics. Two illustrative examples are given in order to show the feasibility of the method.     

四川省地震灾区婴幼儿营养监测状况分析

作者通过对四川省青川县和彭州市两个地震灾区6-24个月龄婴幼儿健康状况的统计分析,发现该地区生长发育状况不佳,存在营养不良现象,其中贫血率较高。经过对比进行营养包6个月干预后的人群统计分析,发现营养状况稍得到改善,其中彭州市目标人群贫血改善明显,由此提出面对四川其它或其它类似贫困地震地区,由于贫困,天灾必然加剧受灾人群的营养状况,特别是贫血率状况,针对这些地区的求援,必须紧迫加强营养包的干预,而且需要持续性的干预,比较可靠的预算应该在灾难期6个月以上方有一定的作用,同时必要的管理措施有利于保证营养干预对象的稳定性,提高营养干预的有效性的。     

通信基站通风节能研究

首先简要阐述了通信基站通风节能的现状及意义,然后对通信基站通风能耗情况进行了分析,最后研究了常见的措施对通信基站通风节能的效应。实践证明,该方案对基础运营商在节能减排、降本增效方面具有良好的效果。     

不同强度健身跑对女大学生身体成分和肺通气功能的影响

为提高大学生阳光体育冬季长跑的实效性,探讨不同强度有氧健身跑对女大学生身体成分和肺通气功能的影响,选择北京林业大学60名大二健康女大学生为研究对象,运用文献资料法、教学实验法和数理统计法,进行了16周不同强度组别健身跑实验。结果发现:中、小强度健身跑锻炼对学生身体成分的影响显著,在脂肪百分比、身体质量指数、腰臀比指标均值改变的幅度最大,差异最显著(p0.01);高强度健身跑锻炼对身体成分的影响较小;通过对不同强度组学生两项肺功能指标测试,三种强度的健身跑使学生的肺功能指标均有一定幅度的提高,但中等强度健身跑对学生肺功能影响最大,提高幅度最明显,两项指标均呈现显著性差异(p0.01)。     

Unveiling the colour palette of Arraiolos carpets: Material study of carpets from the 17th to 19th century period by HPLC-DAD-MS and ICP-MS

Wool samples collected from thirteen Arraiolos carpets from the 17th–19th century belonging to the National Museum of Ancient Art (NMAA, Lisboa, Portugal) collection were analysed to identify the natural dyes and mordants employed in the traditional dyeing process, in a way to complement and improve actual knowledge on this rugs. Natural dyes were extracted from Arraiolos historical wool fibres using a mild extraction method, followed by high-performance liquid chromatography with diode array and mass spectrometry detection (HPLC-DAD-MS) for compound identification. Colourimetry was used to measure colour parameters in all historical samples. Quantification of mordants in the historical fibres was carried out by inductively coupled plasma-mass spectrometry (ICP-MS). Weld, indigo, spurge flax, brazilwood, madder and cochineal were identified as dye sources in the fibres. Alum was the most commonly used mordant, but the presence of iron and zinc was also detected in some darker samples. The use of madder and cochineal is not referred in the available historical dyeing recipes. This study also proved that the actual visual perception of these carpets is strongly affected by the natural dyes photodegradation, which was mostly unaccounted for before.     

The effect of goal-setting prompts in a blended learning environment—evidence from a field experiment

Previous literature has shown that task-based goal-setting and distributed learning is beneficial to university-level course performance. We investigate the effects of making these insights salient to students by sending out goal-setting prompts in a blended learning environment with bi-weekly quizzes. The randomized field experiment in a large mandatory economics course shows promising results: the treated students outperform the control group. They are 18.8% (0.20 SD) more likely to pass the exam and earn 6.7% (0.19 SD) more points on the exam. While we cannot causally disentangle the effects of goal-setting from the prompt sent, we observe that treated students use the online learning platform earlier in the semester and attempt more online exercises compared to the control group. The heterogeneity analysis suggests that higher treatment effects are associated with low performance at the beginning of the course.     

金属矿山利用采空区通风的研究实践

本文针对寿王坟铜矿回风井断面小、线路长、阻力大以及矿井漏风、短路风流严重的问题,对矿井通风系统进行了详细的调查,提出了利用采空区和回风井并联通风的方案,并对利用采空区通风的稳定性和安全性进行了深入的研究,最后应用了利用采空区和回风井并联回风的通风系统,取得了良好的应用效果。将采空区作为回风通道的通风系统对于具有稳定采空区,且采空区透气性良好的中小型金属矿山有实际借鉴意义。     

论自然科学、社会科学、人文科学的三位一体关系

自然科学、社会科学和人文科学是人类科学体系中的三大主干门类,这三大科学门类之间相互差异和相对独立、呈三足鼎立之势,又相互依存和相互关联,共同组成了一个共生共荣、三位一体的整体科学系统。科学的这种三位一体关系要求我们在发展科学的过程中必须注意保持科学系统的整体优化和综合平衡,也即必须坚持和贯彻促使三大科学协调发展的基本原则。     

六盘水市野钟自然保护区黑叶猴生态及种群数量的春季调查研究

2004年4月3日至5月5日,笔者对黑叶猴进行了野外生态及种群数量调查研究,结果表明:(1)原野钟保护区内的黑叶猴仅有8群50只,其中包括1只当月生黄毛婴猴。猴群与1987年调查结果一样,但猴群个体数减少23只,主要是家庭成员减少;(2)保护区外围新发现7群59只,其中包括新增当月生4只黄毛婴猴;(3)黑叶猴的春季食物主要是被子植物的幼芽、叶和花;(4)野钟黑叶猴自然保护区应以黑叶猴分布及取食范围为依据,重新调整规划,建议下游从花嘎乡的底母村左侧河谷两侧到上游叉河北盘江两岸重新规划为黑叶猴自然保护区。     

两种方式的健步走对边缘性血脂升高的中年男性血脂及肺通气功能的研究

摘要：目的：探讨2种方式的健步走对边缘性血脂升高中年男性脑力劳动者血脂及肺功能的影响。方法：选取西安市3所高校从事脑力劳动的科研工作者,筛选出符合（血脂水平分层标准）边缘性血脂升高标准的受试者48人,随机分成匀速组和变速组各24人,实施为期12周的健步走。2组采用的运动强度为,匀速组在第二和第三个10～15 min以60﹪～70﹪HRmax为主,变速组以60﹪～70﹪HRmax和70﹪～80﹪HRmax为主,每周4次,每次40～60 min。重点监测受试者运动前、运动4周、运动12周的血脂六项（TC、TG、HDL-C、LDL-C、Apoa1/Apob）和肺通气功能指标（VC、FVC、FEV1/FVC﹪、MVV、VC/Kg）。结果：1）与运动前比较,运动6周,匀速组血脂及肺通气功能各指标无显著性变化（p>0.05）;变速组TC显著降低（p＜0.05）,FEV1/FVC﹪、MVV、VC/Kg显著升高（p＜0.05）。运动12周,匀速组TC、TG显著降低（p＜0.05）,FEV1/FVC﹪、MVV、VC/Kg显著增高（p＜0.05）;变速组血脂各指标（除Apoa1/Apob外）和肺功能指标（除FVC外）均有显著差异（p＜0.01或p＜0.05）。2）组间比较：运动6周,两组血脂与肺功能各指标无显著性差异（p>0.05）。运动12周,具有显著性差异（p＜0.05）的指标为HDL-C、LDL-C、MVV。3)在不同的运动周期,血脂和肺功能指标的变化幅度均有显著性变化,运动12周明显优于运动6周,变速组变化幅度优于匀速组。结论：1)匀速健步走运动12周,具有明显的调脂效果和提高肺通气功能;变速健步走运动6周,对血脂异常和肺通气功能有显著的改善。运动12周,调脂效果非常显著基本回归正常范围,肺功能显著提高。2)2种方式的健步走,强度较高的变速运动对血脂异常的调脂效果和肺通气功能的提高显著优于匀速运动。