Transmission Modes of Closed Elliptic-Groove Waveguides for Millimeter Waves

In this paper, a new type of horizontal-flat and vertical-flat closed elliptic-groove guides is firstly presented. The field components and characteristic equations for some main transmission modes of the closed elliptic-groove guides are derived by with the help of the mode-matching method and Mathieu function. The variations of the cut-off wavelengths along with eccentricities, widths and lengths of the parallel plates for a number of lower order transmission modes of the closed elliptic-groove guides are also analysed in detail. The calculated results in good agreement with ones in the relevant references are of very important values in theoretical researches and actual applications of closed elliptic-groove guides for millimeter and submillimeter waves.     

Upgrading the lubricity of bio-oil via homogeneous catalytic esterification under vacuum distillation conditions

In order to accelerate the application of bio-oil in the internal combustion engines, homogeneous catalytic esterification technology under vacuum distillation conditions was used to upgrade the crude bio-oil. The lubricities of the crude bio-oil (BO) and refined bio-oil with homogeneous catalytic esterification (RBO_hce) or refined bio-oil without catalyst but with distillation operation (RBO_wc) were evaluated by a high frequency reciprocating test rig according to the ASTM D 6079 standard. The basic physiochemical properties and components of the bio-oils were analyzed. The surface morphology, contents and chemical valence of active elements on the worn surfaces were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy, respectively. The results show that RBO_hce has better lubricities than those of BO, but RBO_wc has worse lubricities than those of BO. The tribological mechanisms of the bio-oils are attributed to the combined actions of lubricating films and factors that will break the film. Compared with BO, plenty of phenols in RBO_wc results in corrosion of the substrate and destroys the integrity of the lubricating films, which is responsible for its corrosive wear. However, more esters and alkanes in RBO_hce contribute to forming a complete boundary lubricating film on the rubbed surfaces which result in its excellent antifriction and antiwear properties.     

Market,welfare and land-use implications of lignocellulosic bioethanol in Hawai'i

This article examines land-use, market and welfare implications of lignocellulosic bioethanol production in Hawai'i to satisfy 10% and 20% of the State's gasoline demand in line with the State's ethanol blending mandate and Alternative Fuels Standard (AFS). A static computable general equilibrium (CGE) model is used to evaluate four alternative support mechanisms for bioethanol. Namely: i) a federal blending tax credit, ii) a long-term purchase contract, iii) a state production subsidy financed by a lump-sum tax and iv) a state production subsidy financed by an ad valorem gasoline tax. We find that because Hawaii-produced bioethanol is relatively costly, all scenarios are welfare reducing for Hawaii residents: estimated between −0.14% and −0.32%. Unsurprisingly, Hawaii's economy and its residents fair best under the federal blending tax credit scenario, with a positive impact to gross state product of $49 million. Otherwise, impacts to gross state product are negative (up to −$63 million). We additionally find that Hawaii-based bioethanol is not likely to offer substantial greenhouse gas emissions savings in comparison to imported biofuel, and as such the policy cost per tonne of emissions displaced ranges between $130 and $2100/tonne of CO₂e. The policies serve to increase the value of agricultural lands, where we estimate that the value of pasture land could as well.     

冻土断裂力学在挡墙基础稳定性分析中的应用

讨论了冻土断裂力学在挡墙基础强度及稳定性分析中的应用 ,讨论了实际工程问题的简化方法 ,给出了冻土断裂力学判据 ;给出了应用实例 ,并与传统的强度设计及稳定性问题进行了计算比较 ;指出冻土断裂力学是对传统设计和计算方法的完善和补充 ;讨论了冻土断裂力学在未来工程设计计算中的应用前景及其作用     

柴达木盆地红柳泉地区下干柴沟组E13Ⅰ和E13Ⅱ砂层组沉积微相及沉积演化研究

柴达木盆地红柳泉地区下干柴沟组E¹₃可划分出4个砂层组,在对下干柴沟组E¹₃Ⅰ和E¹₃Ⅱ砂层组岩心的观察描述和沉积相的电性特征分析基础上,研究了这2个砂层组的沉积微相,并根据微相模式识别和单井相分析,建立了沉积序列和沉积演化模式,并结合剖面沉积微相和砂岩含量和分布,绘制了E¹₃Ⅰ和E¹₃Ⅱ砂层组的沉积微相平面图,结果表明,红柳泉地区下干柴沟组E¹₃Ⅰ和E¹₃Ⅱ砂层组发育有三角洲前缘水下河道砂体,前缘席状砂体也有较好的好育,二者均是储集砂体发育的有利相带。     

High efficiency fuel cell based uninterruptible power supply for digital equipment

Eliminating the ac–dc converter (such as a computer's power supply), in a dc system when using a fuel cell based uninterruptible power supply (UPS), serves several primary functions. Firstly, it eliminates the need for a dc–ac inverter, and secondly, it eliminates a usually highly inefficient component—the power supply. Multiple conversions result in multiple inefficiencies. By replacing the computer's ac power supply with a high efficiency dc power supply capable of operating directly from a fuel cell – and thereby eliminating the inverter – the overall efficiency of the UPS can be increased by 50% or more. This is essential considering that the primary function of a fuel cell based UPS is long-term operation of the system, and poor efficiency equates to higher fuel consumption. Furthermore, inefficient systems have greater power demands, and therefore a larger fuel cell stack is needed to power them. At the present cost of fuel cell systems, this is a considerable problem. The easiest way to accomplish a direct dc UPS is to replace the computer's ac–dc power supply with a dc–dc power supply.     

Investigation of the porous structure of battery separators using various porometric methods

The aim of the investigation is to determine and compare the basic characteristics of the pores in battery separators using mercury porosimetry, which measures the volume of mercury penetrating into the pores, capillary flow porometry, which measures the flow rate passing through the pores, and scanning electron microscopy. Two groups of separators are investigated: PVC and glass mat.Two types of each group are analysed: PVC-R and PVC-E supplied by different manufacturers; and AGM and MAGM (modified AGM—new product developed by LABD at IEES).It has been established that: the PVC-R and PVC-E separators have similar porous structures; the AGM separator and MAGM separator have different pore size distribution, as clearly evidenced by the flow porometry data; though the glass mat separators have greater total pore volume (respective porosity), the PVC separators are characterized by greater permeability, because the pores in their narrowest part have greater diameters than those for the glass mat separators. The two methods used, mercury porosimetry and capillary flow porometry, give information about different characteristics of the porous structure. A combination of both methods will provide a more detailed information about the porous structure of the separators and a clearer idea about the dynamics of the processes that take place in the lead-acid batteries, than the data supplied by each of the techniques used alone.     

Evolution of hydrothermal explosions at Rehai geothermal field, Tengchong volcanic region, China

During the period 1993–2003 over 20 hydrothermal eruptions occurred at Rehai geothermal field, in Tengchong volcanic region, Yunnan Province, southwestern China. Initially, the explosions occurred on the bed of the Zaotang River, and later along a NW–SE striking fault cross-cutting the river. The explosion activity intensified with time. The free gas samples collected from springs created by the explosions show ³He/⁴He ratios of 1.17, 2.22 and 4.05 Ra (Ra = 1.4 × 10⁻⁶) for the three distinguishable stages of ever-increasing magnitude of the explosions, respectively. Data on helium isotopes and gas chemistry indicate that the source of the gases feeding the explosions has progressively shifted from shallower to greater depth. Following this trend, larger hydrothermal explosions will probably occur in the future, so that this hazard must be taken into serious consideration.     

冻土Ⅰ-Ⅱ型复合断裂准则的试验研究

采用四点弯曲试件,参照有关的测试方法,测定了几种不同含水量及不同温度下的冻土Ⅰ-Ⅱ型复合断裂的ＫⅠ和ＫⅡ,并绘制了相应的ＫⅠ／ＫⅠＣＫⅡ／ＫⅠＣ曲线,给出了曲线的表达式,对冻土的Ⅰ-Ⅱ型复合断裂准则进行了讨论,并给出了建议。     

星载微波辐射计热定标源热设计与应用

设计开发了一种星载微波辐射计热定标源,运用有限元分析(Finite Element Analysis,FEA)软件对其 进行热特性仿真分析,并通过热真空环境模拟试验对其进行验证。仿真表明,热定标源温度随着传递距离的增大 (从源体底部向尖劈顶部、从中心向四周)而线性减小;尖劈高度方向的温度梯度dT / dh 大于半径方向的温度梯度 dT / dr,两者随着空间环境温度的增加(2.7 K→293 K)而逐渐减小。通过试验考核,热定标源温度精度在±0. 15 K/16 s 范围内,温度均匀性≤0. 15 K,具有良好的温度稳定性和均匀性,验证了热定标源热设计的合理性与可行性。