圆波导界面电磁场的传播特性

从麦克斯韦方程及边界条件出发对含有两种不同介质的金属波导管进行了研究 ,得到特征方程 (γ1ε2 -γ2 ε1) 2 (μ1γ2 -μ2 γ1) 2 =0 ,指出当γ1ε2 =γ2 ε1,μ1γ2 ≠μ2 γ1时两区域波导模为横磁模 ,γ1ε2 ≠γ1ε2 ,μ1γ2 =μ2 γ1为横电模 ,γ1ε2 =γ2 ε1,μ1γ2 =μ2 γ1为杂交模 .并讨论了截止条件和传播特性 .     

镍铝青铜BAl7-7-2-2合金摩擦磨损性能分析

分析了镍铝青铜BAl7-7-2-2合金及其热处理后的金相组织、硬度、拉伸性能、冲击韧性和摩擦磨损性能。结果表明,镍铝青铜BAl7-7-2-2合金经热处理后,组织发生再结晶细化,κ相析出减少,强度、硬度降低,冲击性能显著提高;BAl7-7-2-2合金摩擦系数低于QAl9-4合金的,热处理后摩擦系数继续减小,减摩性能优异;BAl7-7-2-2合金的磨损率高于QAl9-4合金的,热处理后磨损率降低,磨痕宽度和深度减小,耐磨性得到提高,接近QAl9-4合金的水平。     

Cavitation Erosion Corrosion Behaviour of Manganese-nickel-aluminum Bronze in Comparison with Manganese-brass

The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55-3-1 manganese-brass was investigated by mass loss, electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) and the cavitation damaged surfaces were observed by scanning electron microscopy (SEM). The results showed that ZQMn12-8-3-2 had better cavitation erosion resistance than ZHMn55-3-1. After the cavitation erosion for 6 h, the cumulative mass loss of ZQMn12-8-3-2 w...     

Sorption potential of Moringa oleifera pods for the removal of organic pollutants from aqueous solutions

Moringa oleifera pods Lamarck (Drumstick or Horseradish) is a multipurpose medium or small size tree from sub-Himalayan regions of north-west India and indigenous to many parts of Asia, Africa, South America, and in the Pacific and Caribbean Islands. Its pods (MOP) have been employed as an inexpensive and effective sorbent for the removal of organics, i.e., benzene, toluene, ethylbenzene and cumene (BTEC) from aqueous solutions using HPLC method. Effect of different parameters, i.e., sorbent dose 0.05-0.8g, 25cm(-3) agitation time 5-120min, pH 1-10, temperature 283-308K and concentration of sorbate (1.3-13)x10(-3), (1.1-11)x10(-3), (0.9-9)x10(-3), (0.8-8)x10(-3)moldm(-3), on the sorption potential of MOP for BTEC have been investigated. The pore area and average pore diameter of the MOP by BET method using nitrogen as a standard are calculated to be 28.06+/-0.8m(2)g(-1) and 86.2+/-1.3nm respectively. Freundlich, Langumir and Dubinin-Radushkevich (D-R) sorption isotherms were employed to evaluate the sorption capacity of MOP. Sorption capacities of BTEC onto MOP have been found to be 46+/-10, 84+/-9, 101+/-4, 106+/-32mmolg(-1) by Freundlich, 8+/-0.1, 9+/-0.1, 10+/-0.3, 9+/-0.1mmolg(-1) by Langumir and 15+/-1, 21+/-1, 23+/-2, 22+/-3mmolg(-1) by D-R isotherms respectively, from BTEC solutions at 303K. While the mean energy of sorption process 9.6+/-0.3, 9.2+/-0.2, 9.3+/-0.3, 9.5+/-0.4kJmol(-1) for BTEC is calculated by D-R isotherm only. Rate constant of BTEC onto MOP 0.033+/-0.003, 0.030+/-0.002, 0.029+/-0.002, 0.027+/-0.002min(-1) at solution concentration of 1.3x10(-3), 1.1x10(-3), 0.9x10(-3) and 0.8x10(-3)moldm(-3) and at 303K have been calculated by employing Lagergren equation. Thermodynamic parameters DeltaH -8+/-0.4, -10+/-0.6, -11+/-0.7, -11+/-0.7kJmol(-1), DeltaS -22+/-2, -26+/-2, -27+/-2, -29+/-3Jmol(-1)K(-1) and DeltaG(303K) -0.9+/-0.2, -1.9+/-0.2, -2.3+/-0.1 and -2.6+/-0.2kJmol(-1) were also estimated for BTEC respectively at temperatures 283-308K. The negative values of DeltaH, DeltaS and DeltaG suggest exothermic, stable (with no structural changes at solid-liquid interface) and spontaneous nature of sorption process under optimized conditions. MOP has been used extensively to accrue and then to preconcentrate benzene, toluene and ethylbenzene in wastewater sample.     

Cryptographic implications of Hess' generalized GHS attack

A finite field K is said to be weak for elliptic curve cryptography if all instances of the discrete logarithm problem for all elliptic curves over K can be solved in significantly less time than it takes Pollard's rho method to solve the hardest instances. By considering the GHS Weil descent attack, it was previously shown that characteristic two finite fields are weak. In this paper, we examine characteristic two finite fields for weakness under Hess' generalization of the GHS attack. We show that the fields are potentially partially weak in the sense that any instance of the discrete logarithm problem for half of all elliptic curves over , namely those curves E for which is divisible by 4, can likely be solved in significantly less time than it takes Pollard's rho method to solve the hardest instances. We also show that the fields are partially weak, that the fields are potentially weak, and that the fields are potentially partially weak. Finally, we argue that the other fields where N is not divisible by 3, 5, 6, 7 or 8, are not weak under Hess' generalized GHS attack.     

Sorption potential of rice husk for the removal of 2,4-dichlorophenol from aqueous solutions: kinetic and thermodynamic investigations

The sorption potential of chemically and thermally treated rice husk (RHT) for the removal of 2,4-dichlorophenol (DCP) from aqueous solutions has been investigated. Sorption of DCP by rice husk was observed over a wide pH range of 1-10. The effect of contact time between liquid and solid phases, sorbent dose, pH, concentration of sorbate and temperature on the sorption of DCP onto rice husk has been studied. The pore area and average pore diameter of RHT by BET method are calculated to be 17+/-0.6 m2g-1 and 51.3+/-1.5 nm, respectively. Maximum sorption (98+/-1.2%) was achieved for RHT from 6.1x10(-5) moldm(-3) of sorbate solution using 0.1g of rice husk for 10 min agitation time at pH 6 and 303K, which is comparable to activated carbon commercial (ACC) 96.6+/-1.2%, but significantly higher than chemically treated rice husk (RHCT) 65+/-1.6% and rice husk untreated (RHUT) 41+/-2.3%. The sorption data obtained at optimized conditions was subjected to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. Sorption intensity 1/n (0.31+/-0.01) and sorption capacity multilayer C(m) (12.0+/-1.6 mmolg(-1)) have been evaluated using Freundlich sorption isotherm, whereas the values of sorption capacity monolayer Q (0.96+/-0.03 mmolg(-1)) and binding energy, b, (4.5+/-1.0)x10(4)dm(3)mol(-1) have been estimated by Langmuir isotherm. The Langmuir constant, b, was also used to calculate the dimensionless factor, R(L), in the concentration range (0.6-6.1)x10(-4) moldm(-3), suggesting greater sorption at low concentration. D-R sorption isotherm was employed to calculate sorption capacity X(m) (2.5+/-0.07 mmolg(-1)) and sorption energy E (14.7+/-0.13 kJmol(-1)). Lagergren and Morris-Weber equations were employed to study kinetics of sorption process using 0.2g of RHT, 25 cm(3) of 0.61x10(-4)moldm(-3) sorbate concentration at pH 6, giving values of first-order rate constant, k, and rate constant of intraparticle transport, R(id), (0.48+/-0.04 min(-1) and 6.8+/-0.8 nmolg(-1)min(-1/2), respectively) at 0.61x10(-4)moldm(-3) solution concentration of DCP, 0.1g RHT, pH 6 and 2-10min of agitation time. For thermodynamic studies, sorption potential was examined over temperature range 283-323 K by employing 6.1x10(-4)moldm(-3) solution concentration of DCP, 0.1g RHT at pH 6 and 10 min of agitation time and values of DeltaH (-25+/-1 kJmol(-1)), DeltaS (-61+/-4 Jmol(-1)K(-1)) and DeltaG(303K) (-7.1+/-0.09 kJmol(-1)) were computed. The negative values of enthalpy, entropy, and free energy suggest that the sorption is exothermic, stable, and spontaneous in nature.     

Ni,Fe对Al90TM5Ce5非晶合金稳定性的影响

本文研究了Al90 Fe5Ce5和A190 Ni5Ce5非晶合金及预峰在晶化过程和时效过程中的稳定性。Al90Fe5Ce5非晶合金的晶化开始温度TX 和时效稳定性比Al90 Ni5Ce5非晶合金高。Al90 Fe5Ce5非晶合金预峰所对应的化学短程序结构的稳定性较高 ,而Al90 Ni5Ce5非晶合金预峰所对应的化学短程序结构的稳定性差 ,甚至通过常温时效消失。非晶合金的稳定性与预峰所对应的化学短程序结构的稳定性有密切关系     

Effect of caged fluorescent dye on the electroosmotic mobility in microchannels

We report on measurements of electroosmotic mobility in polymer microchannels and silica capillaries with and without the addition of a caged fluorescein dye to the buffer. For PMMA microchannels, the mobility was found to increase from (2.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) to (4.6 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of 1.2 mmol/L of caged dye. For PC microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (5.4 +/- 0.1) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For PDMS microchannels, the mobility increased from (4.3 +/- 0.2) x 10(-4) cm2 V(-1) s(-1) to (6.4 +/- 0.5) x 10(-4) cm2 V(-1) s(-1) upon addition of caged dye. For fused-silica capillaries, the mobility ((5.5 +/- 0.2) x 10(-4) cm2 V(-1) s(-1)) was unaffected by the addition of the caged dye.     

C6A4MS与C11A7.CaF2的共存与转化关系研究

本文详细研究了C6 A4 MS与C11 A7.CaF2的共存与转化条件。结果表明：C11 A7.CaF2含量较高时能够抑制C6 A4 MS的形成，含量较低时则能与C6 A4 MS共存；升高温度能够消除C11 A7.CaF2对C6 A4 MS的形成的影响；C11 A7.CaF2能与合成矿物C6 A4 MS共存。，The coexistence and transformation condition between C6 A4 MS and C11 A7 . CaF2 is studied in detail in this paper. The results shows that C11 A7 . CaF2 can restrain the formation of C6 A4 MS when in higher content, but It can coexist with C6 A4 MS when its concentration is lower. Increasing temperature can avoid the effect of C11 A7 . CaF2 on the formation of C6 A4 MS. C11 A7 . CaF2 can coexist with syntheitical mineral C6 A4 MS.     

Co-Mn-Ni-O热敏纳米粉体的制备及其特性

采用液相共沉淀法用草酸作为沉淀剂制备了Co—Mn—Ni—O陶瓷热敏电阻纳米粉体，并采用综合热分析(TG、DTA)、X射线衍射(XRD)和扫描电子显微技术(SEM)对该法制备的粉体和对照粉体进行了综合表征，结果显示用该方法可以制备品粒平均粒径在9nm左右、粉体颗粒形貌呈球形、颗粒粒径在50～100nm范围内、粒度分布范围较窄约Co—Mn—Ni—O三元系NTC热敏纳米粉体粉体，能够满足Co—Mn—Ni—O陶瓷热敏电阻对粉体的要求。     

Natural radioactivity and external gamma radiation exposure at the coastal Red Sea in Egypt

Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. In this work, superficial samples of beach sand were collected from the Red Sea coastline (Ras Gharib, Hurghada, Safaga, Qusier and Marsa Alam areas) and at 20 km on Qena-Safaga road. The distribution of natural radionuclides in sand beach samples was studied by gamma spectrometry. The activity concentrations of primordial and artificial radionuclides in samples that are collected from the coastal environment of the Red Sea were 19.2 +/- 3 Bq kg(-1) for (210)Pb, 21.1 +/- 1 Bq kg(-1) for (226)Ra, 22.7 +/- 2 Bq kg(-1) for (238)U, 1.0 +/- 0.1 Bq kg(-1) for (235)U, 11.6 +/- 1 Bq kg(-1) for (228)Ra, 13.0 +/- 1 Bq kg(-1) for (228)Th, 12.4 +/- 1 Bq kg(-1) for (232)Th, 930 +/- 32 Bq kg(-1) for (40)K and 1.2 +/- 0.3 Bq kg(-1) for (137)Cs. The mean external gamma-dose rate was 62.5 +/- 3.2 nSv h(-1), 54.4 +/- 2.8 nGy h(-1) Ra equivalent activity (Ra(eq)) was 107 +/- 5.8 Bq kg(-1), 0.86 +/- 0.04 Bq kg(-1) for representative level index (I(gamma)) and effective dose rate was 0.067 +/- 0.003 mSv y(-1) in beach sand red sea, in air due to naturally occurring radionuclides.     

PU(U)A/SiO2杂化水分散液及成膜性能研究

用异佛尔酮二异氰酸酯(IPDI)、聚酯二元醇、二羟甲基丙酸(DMPA)、乙二胺、二乙醇胺、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、甲基丙烯酸羟乙酯(HEMA)通过原位聚合方法合成了聚氨酯(脲)/聚丙烯酸酯水分散液,并且通过溶胶-凝胶方法合成了聚氨酯(脲)/聚丙烯酸酯/硅溶胶(PU(U)A/SiO2)杂化水分散液.杂化水分散液在pH值为7～11时的贮存稳定性大于1年;经高温、冻融试验后,无絮凝或沉淀出现,与PU(U)A水分散液相同.杂化膜的摆杆硬度、粘附力、耐吸水性、耐溶剂性比无硅溶胶的膜性能好.PU(U)A/SiO2杂化水分散稀溶液成膜后的透射电镜(TEM)结果表明,粒径为8～10nm的硅溶胶(SiO2)包覆在粒径 为50～200nm的PU(U)A粒子外围.ART-FTIR分析结果表明,杂化膜表面富含Si-O-Si官能团.AFM结果表明,与PU(U)A膜相比,杂化膜的硬区相畴尺寸变小.     

Preparation and characterization of grafted polyethylene based azo-polymer films

A series of grafted azo-polymers was prepared from commercial low density polyethylene thin plates (PE). Polyethylene was reacted in the presence of acryloyl chloride using gamma irradiation to give precursor grafted polymers. These materials were esterified in the presence of six different commercial azo-dyes: (E)-2-(ethyl(4-((4-nitrophenyl)diazenyl)phenyl)amino)ethanol (Disperse Red-1, DR-1), (E)-2-((4-((2-chloro-4-nitrophenyl)diazenyl)phenyl)(ethyl)amino)ethanol (Disperse Red-13, DR-13), (E)-2,2′-(4-((4-nitrophenyl)diazenyl)phenylazanediyl)diethanol (Disperse Red-19, DR-19), (E)-4-((4-nitrophenyl)diazenyl)aniline (Disperse Orange-3, DO-3), 4-((E)-(4-((E)-phenyldiazenyl)naphthalen-1-yl)diazenyl)phenol (Disperse Orange-13, DO-13) and 2-methyl-4-((E)-(4-((E)-phenyldiazenyl)phenyl)diazenyl)phenol (Disperse Yellow-7, DY-7) to give the expected grafted azo-polymer films. The obtained polymers were fully characterized; their thermal, optical properties and morphology were studied. In particular, the influence of the irradiation conditions and the incorporated azo-dye on the polymer properties is discussed.     

包覆型纳米SiC-Al2O3水悬浮液流变特性研究

本文通过在纳米SiC颗粒表面包覆一层Al2O3,使包覆型SiC与Al2O3具有相似的表面化学性质,从而包覆型SiC-Al2O3混合粉悬浮液具有相似于单相Al2O3悬浮液的流变性质。研究了分散剂、颗粒匹配及温度对包覆型SiC-Al2O3混合粉悬浮液流变性质的影响。结果表明,对于亚微米粉,尤其纳米粉,高聚物电解质分散剂不能改善其流变性;合适的颗粒匹配及温度可以改善悬浮液的流动性。,The surface chemical property of SiC was similar to that of Al2O3 by coating SiC with Al2O3,so that the rheological behavior of coated SiC-Al2O3 suspension was like to that of single phase Al2O3 suspension.The effect of dispersant,size distribution and temperature on rheological behavior of coated SiC-Al2O3 suspension were studied.Results indicated that polyelectrolyte did not improve rheological behavior for fine powder suspension,especially for nanosized powder suspension,but proper size distribution and temperature could.     

Thermohydraulic stability of helium flow at supercritical pressure under conditions of forced and mixed convection in a vertical heated channel

The excitation of thermally induced oscillations in low-temperature helium flow in channels with different orientation are studied and the boundaries of stability are constructed.Notation c heat capacity - D diameter - F area of the transverse cross section - G flow rate - Gr_A Grashof number - g acceleration of gravity - h enthalpy - p pressure - perimeter - Re Reynolds number - s complex Laplace transform variable - T temperature - t time - x distance along the channel - thermal conductivity - circular frequency of the pulsations - p specific density - in at the inlet to the channel - out at the outlet from the channel - liq the flow - O in front of the throttle at the channel input - m the pseudocritical temperature - N in front of the throttle at the channel output - w and c the pipe wall Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 4, pp. 538–545, October, 1988.     

MC尼龙和MC尼龙/纳米ZnO复合材料晶面间距的膨胀系数和收缩系数

采用原位聚合反应制备铸型(MC)尼龙6/纳米ZnO复合材料,并用动态高温X射线衍射(XRD)法对合成的MC尼龙/纳米ZnO复合材料进行研究,考察其在升温和降温过程中α<,1>和α<,2>晶面间距的变化、结晶结构的热稳定性.结果表明,随着温度的升高,MC尼龙的α<,1>(200)和α<,2>(002+202)晶面分别发生...     

Influence of surrounding media refractive index on the thermal and strain sensitivities of long-period gratings

A detailed study of the thermal and strain sensitivities of a long-period grating when the device is immersed in different external media is presented. The range of refractive indices analyzed are within 1.000 to 1.447, corresponding to samples of air, water, ethanol, naphtha, thinner, turpentine, and kerosene. Within the same range of refractive indices, the strain sensitivity is between (-0.24 +/- 0.03) and (-0.94 +/- 0.11) pm/microepsilon. For the grating immersed in these fluids, the refractive index sensitivity ranges from -3 to -1035.6 nm per refractive index units. The coupling thermo-optic coefficients and the strain-optic coefficients are also measured, resulting in the range from (2.45 +/- 0.04)x10(-5) to (15.89 +/- 0.82)x10(-5) deg C(-1) and (-1.15 +/- 0.04) to (-1.61 +/- 0.04) microepsilon(-1), respectively. A noticeable nonlinear behavior of the thermal sensitivity is found for external media with refractive indices higher than 1.430.     

HMn62-3-3合金的热变形行为及热加工图

通过Gleeble-1500热模拟机在500~600℃、应变速率0.01~10s~(-1)条件下的近等温热模拟压缩试验,建立合金本构方程和热加工图。结果表明:HMn62-3-3合金在热变形过程中发生动态再结晶行为,其峰值应力随变形温度的升高或应变速率的降低而降低;采用Arrhenius方程能够较好地拟合HMn62-3-3合金的流变行为,其热变形激活能为201.525kJ·mol~(-1);根据DMM模型,计算并建立了HMn62-3-3材料的热加工图,由此确定热变形过程中的最佳工艺参数为变形温度610~640℃,应变速率为2~10s~(-1)。     

Comparison of adsorption equilibrium models for the study of CL-, NO3- and SO4(2-) removal from aqueous solutions by an anion exchange resin

The removal of chloride, nitrate and sulfate ions from aqueous solutions by a macroporous resin is studied through the ion exchange systems OH(-)/Cl(-), OH(-)/NO(3)(-), OH(-)/SO(4)(2-), and HCO(3)(-)/Cl(-), Cl(-)/NO(3)(-), Cl(-)/SO(4)(2-). They are investigated by means of Langmuir, Freundlich, Dubinin-Radushkevitch (D-R) and Dubinin-Astakhov (D-A) single-component adsorption isotherms. The sorption parameters and the fitting of the models are determined by nonlinear regression and discussed. The Langmuir model provides a fair estimation of the sorption capacity whatever the system under study, on the contrary to Freundlich and D-R models. The adsorption energies deduced from Dubinin and Langmuir isotherms are in good agreement, and the surface parameter of the D-A isotherm appears consistent. All models agree on the order of affinity OH(-)相似文献   

The Characteristics of Standard Cells with a Low Temperature Coefficient

Through a series of precise measurements of electromotive force (EMF) of standard cells with a temperature range of 0-40°C, this paper proposes the following quartic equations for the cells with Cd-Pb, Cd-Sn, and Cd-Sn-Pb amalgam electrodes, respectively: Et = E20 - [17.36(t - 20) + 0.728(t - 20)2 - 0.0089(t - 20)3 + 0.000 03(t - 20)4] × 10-6(V) Et = E20 - [15.57(t - 20) + 0.624(t - 20)2 - 0.0107(t - 20)3 + 0.000 04(t - 20)4] × 10-6(V) Et = E20 + [23.57(t - 20) - 0.130(t - 20)2 + 0.0104(t - 20)3 - 0.000 08(t - 20)4] × 10-6(V) At the same time it has been found that the characteristics of these cells are almost similar to those of the normal Weston cells. The "criteria of hysteresis voltage" and the "criteria of standard cells of high quality" cannot be used as criteria for our cells. The quality of cells with Hg2SO4 prepared by the electrolytic method is better than that by the chemical method. The compositions of multimetal amalgams and the homogeneity of metal phases have a significant effect on the characteristics of these cells.