自柱撑型纳米分子筛的制备及其在正庚烷裂解反应中的应用

以四丁基氢氧化铵为模板剂、正硅酸乙酯为硅源,采用变温晶化法制备了自柱撑型纳米分子筛。利用XRD、SEM、TEM、N2物理吸附-脱附、NH3-TPD等表征手段对模板剂添加量、分子筛的生长过程、硅铝摩尔比调变范围进行了系统考察。结果表明,80℃低温晶化72 h、170℃高温晶化3 h就可得到结晶度良好的自柱撑型纳米分子筛;低温晶化时间的延长,有利于自柱撑纳米结构的形成;随着模板剂与二氧化硅的摩尔比由0.2增加至0.5,自柱撑型纳米分子筛的分支程度明显变高;通过变温晶化法可制备出硅铝摩尔比为50~300的自柱撑型纳米分子筛。研究了不同硅铝摩尔比自柱撑型纳米分子筛在正庚烷裂解反应中的性能,结果表明,硅铝摩尔比为300的分子筛催化正庚烷裂解具有最高的丙烯与丁烯选择性;随着硅铝摩尔比的降低,催化剂的稳定性逐渐提高。

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.

發刊辭

劉《略》班《志》以爲,諸子之學,始於王官。宗周傾覆,天子失官,九流十家,紛然並作,亦吾國學術之瑰奇者也。然自柱下以還,凡兩千五百餘年,余謂子學或浧而或厄者凡幾。一浧於仲尼殁後:楊朱之貴己,墨翟之尚廉,浸浸然充塞天下,學者靡然從風矣。

The Use of Multiwalled Carbon Nanotubes Mini Column for Preconcentration of Trace Metal Ions in Tap Water of Khartoum City and Their Determination by Flame Atomic Absorption Spectrometry （FAAS）

The adsorption behavior of multiwalled carbon nanotubes （MWNTs） toward heavy elements has been investigated systemically, and a new method has been developed for the determination of trace elements in water samples based on preconcentration with mini-column packed with MWNTs prior to its determination by flame atomic absorption spectrometry （FAAS） The recommended parameters of proposed method influencing the preconcentration of the analytes, such as pH of the sample, sample flow rate and volume, elute solution and interfering ions, have been used. Under the optimized conditions, the calibration graphs were linear with the correlation coefficient range 0.9981-0.9995. According to the results, the metals were found 0.019-0.051, 0.011-0.031, 0.00-0.081, 0.00-0.0002, 0.007-0.0925, 0.00-0.0104 μg/L in water samples for Pb, Mn, Zn, Cd, Fe, Cu respectively. The percentage relative standard deviation （%RSD） for five replicate samples were 〈 5% in all cases. The method has been successfully applied to the determination of trace elements in some environmental samples with satisfactory results.

A simplified model to predict blast response of CFST columns

In order to study the dynamic response of concrete-filled steel tube(CFST) columns against blast loads,a simplified model is established utilizing the equivalent single-degree-of-freedom(SDOF) method,which considers the non-uniform distribution of blast loads on real column and the axial load-bending moment(P-M) interaction of CFST columns.Results of the SDOF analysis compare well with the experimental data reported in open literature and the values from finite element modeling(FEM) using the program LS-DYNA.Further comparisons between the results of SDOF and FEM analysis show that the proposed model is effective to predict the dynamic response of CFST columns with different blast conditions and column details.Also,it is found that the maximum responses of the columns are overestimated when ignoring the non-uniformity of blast loads,and that neglecting the effect of P-M interaction underestimates the maximum response of the columns with large axial load ratio against close range blast.The proposed SDOF model can be used in the design of the blast-loaded CFST columns.

Study on applicability of modal analysis of thin finite length cylindrical shells using wave propagation approach

Donnell’s thin shell theory and basic equations based on the wave propagation method discussed in detail here, is used to investigate the natural frequencies of thin finite length circular cylindrical shells under various boundary conditions. Mode shapes are drawn to explain the circumferential mode number n and axial mode number m, and the natural frequencies are cal-culated numerically and compared with those of FEM (finite element method) to confirm the reliability of the analytical solution. The effects of relevant parameters on natural frequencies are discussed thoroughly. It is shown that for long thin shells the method is simple, accurate and effective.

Stress analysis of clamped-free grid composite cylindrical shell under various end loadings

Stress analysis of cylindrical grid-stiffened composite shells was conducted under transverse loading,pure bending,torsion and axial compression under clamped-free boundary condition.Electrical strain gauges were employed to measure the strains in transverse loading case to validate the finite element analysis which was conducted using ANSYS software.Good agreement was obtained between the two methods.It was observed that stiffening the composite shell with helical ribs decreased the average equivalent Von Mises stress on the shell.The reduction of the stress seemed to be higher in the intersection of two ribs.It was also seen that the stress reduction ratio was higher when the structure was under bending compared to torsion and axial compression.The reduction ratio was approximately 75% in pure bending in the intersection point of the ribs,while it was approximately 25% in torsion.Therefore,it is concluded that the presence of the ribs is more effective under bending.Failure analysis was done using Tsai-Wu criterion.The ribs were observed to result in maximum and minimum increase in the failure load of the structure under transverse bending and torsional loading,respectively.

Natural frequency characteristics of thin-walled homogeneous and manifold layered cylindrical shells under pressure using energy method

Energy method for the vibration of two types of cylindrical shells,namely thin-walled homogeneous isotropic and manifold layered isotropic cylindrical shells under uniform external lateral pressure is presented.The study is carried out based on strain-displacement relationship from Love's shell theory with beam functions as axial modal function.A manifold layered cylindrical shell configuration is formed by three layers of isotropic material where the inner and outer layers are stainless steel and the middle layer is aluminum.The homogeneous cylindrical shell is made-up of isotropic one layer with stainless steel.The governing equations with uniform external lateral pressure for homogeneous isotropic and manifold layered isotropic cylindrical shells are obtained using energy functional by the Lagrangian function with Rayleigh-Ritz method.The boundary conditions that are presented at the end conditions of the cylindrical shell are simply supported-simply supported,clamped-clamped and free-free.The influences of uniform external lateral pressure and symmetrical boundary conditions on the natural frequency characteristics for both homogeneous and manifold layered isotropic cylindrical shells are examined.For all boundary conditions considered,the natural frequency of both cylindrical shells with symmetric uniform lateral pressure increases as h/R ratio increases and those considering natural frequency of the both cylindrical shells with symmetric uniform lateral pressure decrease as L/R ratio increases.

Viability of Stigmas of Pistils in Winter Rape： Peculiarity of Samples with Different Origins

The researches have been carried out in 2011-2012, in the experimental fields of Yuryev Plant Production Institute Kharkiv, Ukraine. The forms of ＂00＂ type （a low content of erucic acid and glucosinolates） and self-pollinated lines--110M-10, 127M-10, 132M-10 were studied; the forms of＂0＋＂ type--selfed lines 124-10, 221-10, 305-10; the forms of＂＋0＂ type--cultivars Victor, Janus, Emerald; forms of ＂＋＋＂ type--cultivars Fyedorovskiy, Marens, Uspikh, as well as, self-incompatible forms 5C, 15C-10, 32C-10 and the original sterile form of mutant origin were used. Viability in stigmas of the pistil lasted 3-7 days, in the forms of ＂＋0＂, ＂＋＋＂ type, 7-15 days in the cultivars and forms of ＂0＋＂, ＂00＂ type, 14-21 days in the self-incompatible and sterile forms. A fast loss of sensitivity to pollen by pistil＇s stigma was observed in the forms of＂＋0＂ and ＂＋＋＂ types. On the contrary, in self-incompatible and sterile forms was observed a gradual increase of sensitivity of pistil＇s stigma to pollination and then its gradual fall. A maximum of sensitivity of a pistil＇s stigma to pollen in ＂00＂ and ＂0＋＂ forms was on the 3rd-6th day after castration.

Moving the Goalpost： ＂Come-We-Stay＂ Practice in Menchum Division （MD）, Cameroon

This paper seeks to understand people＇s perception of ＂come-we-stay＂ （CWS） cohabitation in Menchum Division （MD）, Cameroon. As in most of Africa, marriage is a valued institution that ensures the continuation of the family tree. The emergence of CWS is gathering momentum fast in many communities in the country much to the dislike,of the church and custodians of tradition who perceive CWS to be a cheap union form that breaches marriage norms. This paper seeks to address whether the emergence of CWS has affected marriage perceptions in MD. Initially, quantitative data were collected via online survey disseminated via Facebook. The time-efficiency, economic viability, convenience and anonymity of this method made it a viable method for this study. Later, however, due to a low response to the Facebook link, the online survey was constructed into a questionnaire and administered to the same target population. Questionnaires were relevant to this study because they could be self-administered. However, the questionnaires were limited as they did not allow for attention to details. The data were analysed using content analysis.

Three－Dimensional Numerical Simulation of Natural Convection Heat Transfer in an Inclined Cylindrical Annulus

A numerical study of natural convection heat transfer in an inclined cylindrical annulus has been conducted. The inner cylinder of the annulus is maintained at uniform heat flux and the outer cylinder at constant temperature. The two end walls are assumed to be insulated. A numerical code has been developed to calculate the steady state three-dimensional natural convection in an inclined cylindrical annulus, and the research emphasis is placed on the influences of inclination angle or and modified Rayleigh number Ra on the natural convection heat transfer in the annulus. Computations were carried out in the ranges of 0°α 90*, 2.5×105 Ra* and Pr=0.7 with fixed aspect ratio of H=28.97 and radius ratio of K= 3.33. The numerical results are compared with the experimental correlations from the literature and the inclination angle effect on heat transfer is found to be insignificant. Detailed results of heat transfer rate, temperature, and velocity fields are presented for the case of or α=45° and discussion is also made concerning the comparison between the numerical and experimental results for the specific case of α=90°.

Effect of Cervical Manipulation on Autonomic Nervous Function in Healthy Volunteers

Objective： According to the theory of traditional Chinese medicine, the effect of cervical stimulation on autonomic nervous system activity in humans was investigated. Methods： Healthy young male volunteers were selected as subjects of the trial. The upper cervical spine （C2-5） was stimulated bilaterally with spinal manipulation, and changes in heart rate and heart rate variability were calculated as measures of effects on autonomic nervous system tone. Results： Thirty healthy young male volunteers were tested. It was found that heart rate decreased （R-R interval prolonged） significantly. SDNN and total power spectrum increased significantly, indicating an increase in sympathetic tone. Conclusion： Cervical manipulation can regulate the autonomic nervous system tone in healthy young men, and it suggests a possibility of treating cardiovascular diseases such as arrhythmia with cervical manipulation.

Schwarz lemma at the boundary of the unit polydisk in C^n

We establish a new type of the classical boundary Schwarz lemma for holomorphic self-mappings of the unit polydisk Dnin Cn. By using the Carath′eodory metric and Kobayashi metric of Dn, we obtain some properties of the complex Jacobian matrix Jf(p) at a boundary point p of Dnfor a holomorphic self-mapping f of Dn. Our results extend the classical Schwarz lemma at the boundary to high dimensions.

Exact free vibration analysis of open circular cylindrical shells by the method of reverberation-ray matrix

This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions. Based on the Donnell-Mushtari-Vlasov thin shell theory, an analytical solution of the traveling wave form along the simply supported edges and the modal wave form along the remaining two edges is obtained. With such a unidirectional traveling wave form solution, the method of the reverberation-ray matrix is introduced to derive the equation of natural frequencies of the shell with different classical boundary conditions. The exact solutions for natural frequencies of the open circular cylindrical shell are obtained with the employment of a golden section search algorithm. The calculation results are compared with those obtained by the finite element method and the methods in the available literature. The influence of length, thickness, radius, included angle, and the boundary conditions of the open circular cylindrical shell on the natural frequencies is investigated. The exact calculation results can be used as benchmark values for researchers to check their numerical methods and for engineers to design structures with thin shell components.