低湿度下质子交换膜燃料电池的交流阻抗分析

采用Nafion(112膜制备膜电极(MEA)并对质子交换膜燃料电池(PEMFC)进行了无外增湿条件下E-I极化曲线和电化学交流阻抗谱(EIS)的测试。对比分析了20和55℃时的交流阻抗谱图,结果表明不同温度下EIS中代表质子传导电阻的Rhf值和电荷转移电阻的Rct值有明显不同,低电流密度下的Rhf值和E-I极化曲线上的欧姆极化区具有更好的一致性。电池在15 mA.cm-2的恒电流密度下放电时,随着温度升高Rhf值和Rct值都相继增大,其中Rhf值随温度升高有显著变化,是导致PEMFC在操作温度超过45℃时性能降低的主要因素。     

Ca2+对质子交换膜燃料电池性能的影响

质子交换膜燃料电池(PEMFC)长期运行过程中,其部件因损伤产生的杂质金属离子对燃料电池的电化学性能有重要影响。模拟PEMFC中Ca2+污染燃料电池工况,研究了Ca2+对PEMFC电化学性能的影响。实验结果表明:随着污染时间的增加,燃料电池性能逐渐衰减,当污染时间超过9 h,电池电压急剧降低;在高电流密度区(电流密度>400 mA/cm2),电压衰减最明显。在500 mA/cm2电流密度下恒电流放电2 h后,电压降低了41%。Ca2+的存在及其积累对质子交换膜燃料电池有明显的毒化作用。     

二次吹扫条件下的PEMFC冷启动实验

通过使用干空气二次吹扫的方式对稳定工作后的质子交换膜燃料电池(PEMFC)单电池进行除水处理,考察了单电池经过吹扫除水操作后的除水量以及内阻变化过程,并研究了单电池经过吹扫除水处理后的常温启动性能以及-10℃下的冷启动性能.实验研究发现:单电池经过干空气二次吹扫处理后,可以在较短时间内经济有效地移除电池内的水,同时单电池的内阻升高.单电池经过干空气二次吹扫后常温启动性能下降,且随二次吹扫流量的增加而加剧,但未造成不可恢复的性能损失.适当的二次吹扫流量可以使电池成功冷启动.吹扫除水策略是优化PEMFC冷启动性能的关键因素之一.     

燃料电池电堆停机吹扫及低温冷启动性能的试验研究

搭建了燃料电池电堆吹扫及低温冷启动测试系统,研究燃料电池停机吹扫电堆初始温度、吹扫时间、吹扫气体等因素对电堆欧姆阻值的影响,研究不同初始含水量对低温冷启动性能的影响.试验结果表明,初始温度越高,电堆欧姆阻值升高越快;相比于单侧气体吹扫,氢气和空气同时吹扫是燃料电池最优的气体吹扫方式;适当降低质子交换膜燃料电池初始含水量有利于减少启动时间,改善启动性能.     

熔盐法处理废旧聚丙烯腈纤维制备超级电容器碳材料及性能表征

以废旧纺织品聚丙烯腈为碳源,在氯化锌-氯化钾熔盐体系一步碳化活化制备超级电容器碳材料.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面分析仪等物理测试方法对材料进行结构、形貌和孔隙表征.并利用电化学工作站在三电极体系下对制备的碳材料进行循环伏安(CV)、恒流充放电(GCD)和交流阻抗(EIS)测试.结果表明,通过在空气中200℃稳定化10 h、氯化锌-氯化钾熔盐体系中800℃下炭化2 h制备的活性炭具有较大的比表面积和发达的孔结构,作为超级电容器电极材料展现出优异的电化学性能.在0. 25 A/g电流密度下最大比电容达319 F/g;在电流密度高达10 A/g下,比电容仍保留62. 7%.经过5 000次充放电循环性能测试,容量保持率可达82. 6%.     

开路电压工况下燃料电池膜电极耐久性研究

采用开路电压(OCV)工况研究了质子交换膜燃料电池(PEMFC)膜电极的耐久性,在OCV工况运行过程中,定期地通过极化曲线、电化学交流阻抗谱(EIS)、线性扫描伏安法(LSV)、短路电阻测试等在线测试方法对膜电极性能进行分析。当OCV工况运行结束后,采用扫描电镜(SEM)、离子色谱对质子交换膜(PEM)厚度和阴、阳极废水进行分析。结果表明,在OCV工况下运行115h后,PEMFC的开路电压由1.013V下降到0.794V,最大功率密度由538.8mW/cm~2下降到196mW/cm~2;在线电化学测试结果表明,欧姆电阻先减小后增大,氢气渗透通量逐渐增大,短路电阻逐渐减小;离子色谱测试结果表明,阴极和阳极废水中都存在氟离子;SEM表征发现,PEM厚度减小;在OCV工况下,PEM发生了衰减,从而导致PEMFC开路电压下降和性能衰减。研究结果表明PEM是影响膜电极耐久性的重要因素。     

适用于质子交换膜燃料电池的H2中H2S浓度阈值控制研究

利用耐受性曲线、极化曲线、循环伏安等电化学测试手段,分别考察了H2中ψ(H2S)分别为0.25×10-6、0.5×10-6、0.75×10-6、1.0×10-6、1.25×10-6、1.5×10-6以及5.0×10-6时对质子交换膜燃料电池(PEMFC)性能的影响.分析PEMFC性能达到相同的下降程度时通入H2S的量与其浓度之间的关系,通过拟合计算,得出H2中ψ(H2S)的合理控制范围为小于等于0.2×10-6.通过比较不同浓度H2S影响下的耐受性曲线,可以看出H2S在Pt表面的吸附具有累积性,即使ψ(H2S)低于0.2×10-6,其长时间的影响也会造成电池性能的下降.因此,如果单从控制H2中H2S浓度的角度来维持电池性能并不理想,还需要定期对电池性能进行恢复.比较了循环伏安法和空气吹扫法对电池性能的影响,这两种方法可分别使电池的性能恢复到初始状态的97%和95%,但是空气吹扫法更易于在车载条件下实现.     

质子交换膜燃料电池带载吹扫实验研究

通过实验对质子交换膜燃料电池单电池的停机吹扫过程开展研究。基于带载吹扫的方式研究带载电流、吹扫流量、单电池温度对吹扫的影响。研究结果表明：带载吹扫能有效地降低单电池吹扫时的电压，带载电流越大单电池初始电压越低，且随着吹扫时间的增加电池电压持续降低，可有效避免单电池长时间处于高电位。此外，增大吹扫气体流量、提高电池温度均可提高吹扫的速率，且两者对吹扫速率影响较明显。在实验条件下，阳极进气流量0.34 L/min，阴极进气流量1.32 L/min，带载电流密度0.04 A/cm²，能够同时满足吹扫时间较短、氢气消耗量较少和吹扫时电池电压较低的吹扫目标。     

锂离子电池用LiPF_6/PC+FEC电解液的低温性能

研究氟代碳酸乙烯酯(fluoroethylene carbonate,FEC)添加剂对锂离子电池用碳酸丙烯酯(PC)基电解液低温放电性能和常温循环性能的影响,并通过电化学阻抗谱(EIS)、X线光电子能谱(XPS)以及气质联用谱(GC-MS)等对FEC在PC基电解液中的作用机理进行探讨。研究结果表明:往PC电解液中添加质量分数为5%的FEC可以在石墨电极表面形成完整且致密的SEI膜,从而有效阻止PC在负极石墨的共嵌入;电池在低温-20℃及-40℃下0.5C放电容量分别可达到室温容量的98%及87%;FEC形成的SEI膜有效降低了锂离子电池的低温电荷转移阻抗,是提高电池低温性能的主要因素之一;FEC在正极钴酸锂材料表面形成了导电性能优异的SEI膜层,改善了锂离子电池的低温性能和常温循环性能。     

超级电容器材料MnO2在有机电解液中的电化学性能

采用固相合成法制备了MnO2超级电容器材料,并用X射线衍射(XRD)、循环伏安、交流阻抗、恒流充放电及循环寿命测试等方法对所制得的MnO2电极材料的结构和电化学特性进行了研究.结果表明所制备的MnO2为无定形结构,该电极材料在有机电解液1.0 mol·L-1 LiClO4/AN中比在1.0 mol·L-1 LiClO4/EC+DMC中有更好的电化学性能,电位窗口为0.1～1.1 V(vs.Ag),比电容达171.2 F/g,并具有良好的准电容特性.在1.0 mol·L-1 LiClO4/AN有机电解液中,该电极以1.0 mA/cm2充放电电流密度循环5 000次衰减仅为1.3%,显示了良好的循环寿命.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

The Analects and the Moment in Peking——The influence of a Confucian education system on the personality formation,the way of thinking and the fate of the main characters

0.Preface China has long been boasting of its colorful and immense culture which comprises of Taoism,Confucianism and Buddhism.The interwoven influence among the religions on Chinese way of thinking,on the nation＇s behavior in their social life throughout the long history is beyond list.