一种新的解锁螺栓分离时间测试方法

基于激光位移传感器测试解锁螺栓分离时间的思想,设计一种新的解锁螺栓分离时间测试方法,并设计了相应的测试系统,其测试不确定度为0.184%.通过试验得到新方法测得解锁螺栓分离时间平均值14.74ms,传统的通-断靶线法测得分离时间平均值14.60ms,三次试验均值相差0.14ms.结果表明,新方法不仅能直接有效地测试解锁螺栓分离时间,还能间接地表征解锁螺栓的分离速度、冲击加速度以及分离冲量等分离特性参数.     

Response of the northwestern Pacific upper water δ~(13)C to the last deglacial ventilation of the deep Southern Ocean

The deglacial δ~13C minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad δ~13C minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of in- fluence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054 from the KSR are well positioned to identify signals from the southern hemisphere in the northwestern Pacific. Planktonic foraminiferal tests from the upper 1030 cm of the core were subject to AMS14C, carbon and oxygen isotopic measurements. A negative excursion was found to occur from about 20.0-6.0 ka BP in δ~13C records of both surface (Globigerinoides ruber) and subsurface (Pulleni- atina obliquiloculata) dwellers, but the overall trends of the two curves have reversed since 26.5 ka BP. Moreover, the δ~13C rec- ord of G. ruber (the surface dweller) shows a robust link to the record of atmospheric CO2, and its changes precede the records of P. obliquiloculata (the subsurface dweller). According to the hydrologic conditions, the broad δ~13C minimum event recorded in the KSR is also a response to the increasing ventilation of the deep Southern Ocean around Antarctica during the last deglaciation. The inconsistency between the records of the surface and subsurface dwellers was possibly caused by the ways that the low δ~13C signal was transmitted. Subsurface water primarily received the low δ~13C signal from the Antarctic Intermediate Water (AAIW), whereas the surface water was probably mainly impacted by atmospheric CO2 in the KSR. The records from the KSR confirm the deduction that the broad δ~13C minimum event in the Okinawa Trough was due to the impact of tropical Pacific surface water dur- ing the last deglaciation, and suggest that signals from the southern high latitudes also can be delivered to the northern middle latitudes.     

Habitat-induced reciprocal transformation in the root phenotype of Oriental ginseng is associated with alteration in DNA methylation

Oriental ginseng is an important medicinal plant that grows in 2 major forms or ecotypes, wild and domesticated. Each form differs conspicuously in root phenotype, but can be converted from one type to another by habitat. Here we show that the habitat-induced transformation of ginseng root phenotype was accompanied by alteration in cytosine methylation at a large number of 5′-CCGG-3′ sites detected by the methylation-sensitive polymorphism (MSAP) marker. The collective CG and CHG methylation levels of all 4 landraces of the domesticated form were significantly lower than those of the wild form. Interestingly, artificially transplanted ginseng plants recreated in both directions the methylation levels (at least in CHG) of their natural counterparts. The methylation differences between the 2 ginseng ecotypes were validated at 2 isolated MSAP loci bearing homology to a 5S rRNA gene or a copia retrotransposon. Our results implicate a link between epigenetic variation and habitat-induced phenotypic flexibility in Oriental ginseng.     

Evaluation of humic acid removal by a flat submerged membrane photoreactor

A flat submerged membrane combined with a TiO 2 /UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV 254 absorbance, UV-vis spectra, dissolved organic carbon (DOC) concentration, specific UV absorbance (SUVA), and trihalomethane formation potential (THMFP). The FSMPR process was effective in removing more than 86% of DOC and nearly 100% of UV 254 absorbance, while the THMFPs of samples were reduced to < 19 μ g/L after 150 min of treatment. In addition, changes in transmembrane pressure (TMP) with and without UV were evaluated; TiO 2 /UV was effective at controlling membrane fouling by HA. Analysis of the molecular weight (MW) distributions and three-dimensional excitation-emission matrix (EEM) fluorescence spectra of HAs revealed that the effectiveness in membrane fouling control is a result of changes in HA molecular characteristics. The TiO 2 /UV photocatalytic reactor caused the degradation of high MW, hydrophobic humic-like molecules to low MW, hydrophilic protein-like molecules, although this fraction was not completely removed during 150 min of treatment and was less responsible for membrane fouling.     

基于邻域粗糙集的不完整决策系统特征选择算法

针对不完整决策系统属性约简算法时间复杂度较高问题,基于正域不变条件下,决策系统分类能力保持不变原则,提出不完整决策系统前向顺序特征选择算法.该算法从约简集为空集开始,根据在约简集合中加入各属性后对正域影响程度大小将属性降序排列,采用顺序前向搜索,选择当前最佳特征加入特征约简集合,确定最佳特征子集.将该算法扩展到基于邻域...     

宽带认知无线电网络分布式协作压缩频谱感知算法

针对宽带认知无线电网络中压缩频谱感知算法在低信噪比环境下频谱检测性能下降的问题,提出了一种基于高斯过程的分布式压缩频谱感知(PBCS)算法.首先应用层次化的正态分布概率模型来表示压缩频谱的重构,然后各个认知无线电用户交换模型参数并结合本地的压缩采样数据进行压缩频谱感知.有别于其他直接融合频谱感知结果或检测数据的协作式算法,PBCS算法通过模型参数融合来进行协作,能有效减小信噪比低的协作用户的影响,从而提高算法的抗噪性.仿真结果表明,PBCS算法可以在-5dB的信噪比条件下达到检测概率大于0.9、误检概率为0.1的频谱检测性能.     

深基坑出碴方案比选

深基坑出碴在一些情况下会成为制约工期的关键因素,尤其是复杂地形条件下,在首先满足工期的前提下,还要综合考虑现有机械情况、技术条件和经济效益以及其他作业干扰,这使得深基坑出碴变得更加复杂。文章通过准朔铁路黄河特大桥工程特点,对几种深基坑出碴方案进行了分析对比,综合考虑后选择了履带吊出碴方案。     

淋巴囊肿病病毒主要衣壳蛋白1.3 kb基因片段的原核表达

取淋巴囊肿病病毒感染牙鲆组织,蛋白酶K裂解,PCR法成功获得了淋巴囊肿病病毒主要衣壳蛋白1.3 kb基因片段.构建其原核表达载体,IPTG诱导表达.结果表明,该融合蛋白分子量约70 kD,可与抗LCDV多克隆血清特异反应.为LCDV基因工程疫苗的研制奠定了实验基础.     

宁夏彭阳县退耕还林还草研究

运用了生态学、经济学的办法,在彭阳县退耕还林还草的大前提下,对于彭阳县的各种状况进行了分析,探讨了以农林牧复合体系为指导的生了一条果园复合经营脱贫致富的新路子。态农业,并论证了其可行性,分析了三种模式综合所能带来的生态经济效益,开创     

浅谈文脉——城市记忆的延续

随着城市建设的高速发展,城市出现了日新月异的变化,但同时也失去了历史文脉.一些有意义的传统生活场景被破坏,城市也因此失去了自己的特色,历史形成的街道、胡同、牌坊、宗教圣地等城市形态作为完整表达建筑和城市意象的文脉,被成片、成街、成坊地拆除,威胁到城市形态的相容性和延续性."立新"不必"破旧",尊重历史传统并不等于拘泥于传统.有意识地保留传统文脉,将使得城市更富有地方风味.