颗粒冲蚀对注射法制备C/C-ZrC-SiC复合材料 抗烧蚀性能的影响研究

目的采用ZrC和SiC复相陶瓷对C/C复合材料进行改性,研究改性后的复合材料受到颗粒冲蚀破坏的烧蚀行为。方法采用注射法将ZrC和SiC复相陶瓷前驱体引入到等温化学气相渗透法(ICVI)制备的低密度C/C复合材料中,再通过高温热处理、ICVI的方法制备出ZrC和SiC复相陶瓷改性的C/C(C/C-ZrC-SiC)复合材料,随后对制备的复合材料进行高速颗粒冲击实验破坏,并对破坏后的试样进行氧乙炔火焰烧蚀,研究其烧蚀行为。结果改性后的复合材料线冲蚀率和质量冲蚀率分别为253.1μm/s和79.8 mg/s,相较于同孔隙率的C/C复合材料分别降低了49.2%和61%。颗粒冲蚀破坏后C/C-ZrC-SiC复合材料的线烧蚀率和质量烧蚀率分别为4.26μm/s和1.44 mg/s,相比于同孔隙率的C/C复合材料,分别降低了37%和39%。结论由于引入的ZrC和SiC陶瓷相的硬度大于碳基体,C/C-ZrC-SiC复合材料在受到高速颗粒的冲击时,能通过硬质陶瓷相起到抗冲击作用,使得改性后的复合材料抗冲蚀性能大幅度提高。受到颗粒冲蚀破坏后的C/C-ZrC-SiC复合材料内部仍存在超高温陶瓷相,烧蚀过程中能够形成ZrO2骨架结构和SiO2球形颗粒,进而有效保护碳纤维和热解碳基体。     

The behavioral component in the meaning of places

How do people think about the physical setting in the world around them? Part of the answer to this question may be in terms of the behaviors that occur there. To explore people's knowledge of behavior—place associations, twenty places (shown via color photographs) were assessed in five ways: (a) ratings of the place's suitability for each of eleven behaviors, (b) ratings of the expected frequency of occurrence of the eleven behaviors, (c) free listings of reasons for going to each place, (d) free listings of activities-while-there and (e) free listings of activities associated with the place. Results showed that people can distinguish places on the basis of behaviors, that the behavioral component of place meaning is composed of distinct aspects, and that knowledge of behavior is related to a global, overall representation of a place.     

空调压缩机冷媒爆炸反应特征分析

冷媒与空气的反应特征对空调压缩机安全性有重要影响.本文采用最小自由能原理,分别对两种冷媒R407C和R410A与空气的混合气体的爆炸反应参数进行了数值计算,得到了不同初始压力和不同冷媒含量条件下,混合气体爆炸反应温度和压力,分析了混合气体反应压力条件和爆炸极限范围.结果表明:初始压力低于0.2 MPa时,R407C-空气混合气体和R410A-空气混合气体均不会发生爆炸;初始压力超过0.3 MPa时,混合气体能够发生爆炸,爆炸反应温度和压力随着初始压力的升高而升高;R407C和R410A质量分数分别在34%、35%左右,混合气体反应温度和压力达到最大值.R407C和R410A易燃易爆特征相近;但爆炸范围都比氟利昂(R22)气体宽,即同样的条件下更容易发生爆炸.该计算结果能够为新型冷媒R407C和R410A的安全使用提供一定的依据.     

全新世青藏高原东部西南季风的演变

本研究报道一组新的西南季风代用指标,即泥炭中单一种属植物———木里苔草残体纤维素和泥炭混合植物残体纤维素的δ13C时间序列,所记录的青藏高原东部全新世气候变化。两记录表明,该区全新世的下限年龄约11200aBP(14C年龄约9900aBP);从约11200aBP起该区迅速进入湿暖的全新世阶段,季风活动迅速增强;在约10800～5500aBP期间,季风总体保持在强盛状态,但其间有4次突然减弱,气候变干冷;约从5500aBP起季风活动在波动中逐渐减弱,其中有4次减弱最明显。所有这8次气候的突然变化都与北大西洋浮冰事件一一对应。这种密切的相关关系表明,西南季风强度的波动可能是对全球变化,特别是对海洋热盐环流引起的地球南北方气候波动的所谓"跷跷板效应"的响应。     

Tell the truth or not? The montero mechanism for emissions control at work

We experimentally test the truth-telling mechanism proposed by Montero (2008) for eliciting firms' abatement costs. We compare this mechanism with two well-known alternative allocation mechanisms, free and costly allocation of permits at the Pigouvian price. Controlling for the number of firms and the firms' maximal emissions, we find that, in line with the theoretical predictions, firms over-report their maximal emissions under free allocation of permits and under-report these under costly allocation of permits. Under Montero's mechanism, by contrast, firms almost always report their maximal emissions truthfully. However, in terms of efficiency, the difference between Montero's mechanism and costly allocation disappears with industries including more than one firm.     

Cost pass-through to higher ethanol blends at the pump: Evidence from Minnesota gas station data

We examine the pass-through of wholesale prices to retail prices in the market for E85, which contains 51%–83% ethanol, and in the much larger market for E10, which contains 10% ethanol. We use a panel dataset consisting of monthly observations from 2007 to March 2015 on wholesale and retail prices for 274 Minnesota gas stations that sell both E10 and E85. Consistent with prior research, the cumulative pass-through coefficient for E10 is 1.00 after one month. In contrast, the E85 market is sparse, and although pass-through increased over time, we estimate it to be only 0.53 statewide from 2012 to 2015. Pass-through is higher at stations with more local E85 competitors. In the Twin Cities, which has a high density of E85 stations, pass-through is nearly complete, but outside the Twin Cities slightly less than half the wholesale discount of E85, relative to E10, is passed on to the consumer.     

A new baseline model for estimating willingness to pay from discrete choice models

We show a substantive problem exists with the widely-used ratio of coefficients approach to calculating willingness to pay (WTP) from discrete choice models. The correctly calculated standard error for WTP using this approach is shown to be undefined. This occurs because the cost parameter's standard error implies some possibility the true parameter value is arbitrarily close to zero. We propose a simple yet elegant way to overcome this problem by reparameterizing the (negative) cost variable's coefficient using an exponential transformation to enforce the theoretically correct positive coefficient. With it the confidence interval for WTP is now finite and well behaved.     

长江口柱状沉积物中有机质C/N比的研究

对长江口四个站位沉积物中有机质的C／N比在垂向上的分布进行了研究，在影响沉积物中有机质C／N比的环境因素中，上覆水体的水深、盐度、密度以及浊度对其有一定的影响．在研究沉积物中有机质C／N比的分布及其影响因素的基础上，进一步估算了陆源输入和海洋自生有机碳在这四个站位沉积物有机碳中所占的比例，结果表明，海洋自生组分占沉积物总有机碳的比例分别为：53．57％(8号站位)、20．34％(11号站位)，12．28％(17号站位)和32．73％(26号站位)．     

前驱物结晶体升华成膜法制备TiO2薄膜及其光催化性研究

采用“前驱物结晶体升华成膜法”工艺，使含钛前驱物结晶体草酸氧钛酸以升华的方式，均匀地在玻璃表面形成前驱物薄膜；经过热处理，制备出外观平整透明的玻璃基TiO2薄膜，其薄膜厚度为80-100nm，粒度≤50nm。初步研究了制备条件、薄膜性能和本工艺制备的玻璃基TiO2纳米薄膜对甲基对硫磷的光催化降解性能。     

普通小球藻和铜绿微囊藻与粘土颗粒凝聚沉降行为研究

本研究结果表明,不同的藻类和不同的粘土颗粒均使藻类与粘土颗粒的凝聚沉降发生变化。结果还表明,溶液中[Cu~(2+)]浓度超过10~(-5)mol后,加快了小球藻与高龄土的凝聚沉降。使80％以上的小球藻和高岭土在不到10min内即凝聚沉降。在最后结合实验结果讨论了利用藻类与粘土的凝聚沉降治理水体污染。