Effect of Calcination Condition on Thermal Activation of Ibere Clay and Dissolution of Alumina

Bauxite deposits for production of alumina are lacking in Nigeria and there is an aluminium smelter plant in the country which requires alumina for its operation. Development of alternative alumina resource using clays that are abundant in the country is the focus of this paper. The thermal activation of Ibere clay from southeastern Nigeria for optimal leaching of alumina was investigated. The clay assayed 28.52% Al2O3 and 51.6% SiO2, comprising mainly kaolinite mineral and quartz or free silica. The alumina locked up in the clay structure was rendered acid-soluble by thermal activation which transformed the clay from its crystalline nature to an amorphous, anhydrous phase or metakaolinite. The clay samples were heated at calcination temperatures of 500°C, 600°C, 700°C, 800°C, and 900°C at holding times of 30, 60, and 90 minutes. Uncalcined clay samples and samples calcined at 1000°C (holding for 60 minutes) were used in the control experiments. The result of leaching the clay calcines in 1 M hydrochloric acid solution at room temperature, showed that the clay calcines produced at 600°C (holding for 60 minutes) responded most to leaching. Samples calcined for 60 minutes also responded better than those held for 30 or 90 minutes. Based on activation energy studies, it was observed that calcines produced at 600°C (for 60 minutes) had both the highest leaching response (50.27% after 1 hour at leaching temperature of 100°C) and the lowest activation energy of 24.26 kJ/mol. It is concluded therefore that Ibere kaolinite clay should be best calcined for alumina dissolution by heating up to 600°C and holding for 60 minutes at that temperature. The clay deposit has potential for use as alternative resource for alumina production in Nigeria where bauxite is scarce.

基于Iber模型的公路路堤排水系统设计方法

现有大量研究考察了路堤排水管间距、高度、坡度和降雨特征等因素之间的复杂关系,以寻求路堤排水管的最佳间距。确定道路排水要素之间的正确间距对于最大限度减少道路上的水流量至关重要。提出了一种基于数值分析的道路排水系统Iber(一种用于模拟自由表面流动的二维数值工具)设计方法,用于分析公路径流的水力行为,确定适当的排水行为,并将该方法应用于案例研究。基于坡度高达5%的直线高速公路路段,考虑不同尺寸类型的喷嘴、排水管间距,进行了测试分析以评估排水管间距、纵向坡度和喷嘴尺寸。结果表明:除了提供每个排水管的吸收能力外,该模型的水力性能也很合适。分析了喷嘴尺寸、坡度和路堤宽度对吃水和流速的影响,确定了排水管间距和喷头类型对道路排水设计的影响。结果有助于理解不同变量对道路径流水力行为的影响,并为适当的排水设计提供相关信息。

Preparation and Characterization of Organic/Inorganic Hybrid Nanofibers

A new class of nanocomposites based on organic and inorganic species integrated at a nanoscale has obtained more attention these years. Organic-inorganic hybrids have both the advantages of organic materials, such as light weight, flexibility and good moldability, and inorganic materials, such as high strength, heat stability and chemical resistance. In this work, PVAc/TiO2 organicinorganic hybrid was prepared by sol-gel process. Eiectrospinning technique was used to fabricate PVAc/TiO2 hybrid nanofibers. The structures and properties of the hybrid nanofibers were characterized by Scanning Electron Microscopy （SEM）, Atomic Force Microscope （AFM）, Differential Scanning Calorimeter （DSC） and Fouriertransform infrared （FTIR） spectra. SEM and AFM were employed to study the topography of the hybrid nanofibers. The chemical structure of the hybrid nanofibers were examined by FTIR. The DSC scans revealed the second order transition temperature of the hybrid materials were higher than PVAc.

Polarization multiplexing QPSK signal transmission in optical wireless-over f iber integration system at W-band

We propose and experimentally demonstrate a novel scheme to realize polarization-division-multiplexing quadrature-phase-shift-keying （PDM-QPSK） signal transmission over fiber, wireless and fiber at Wband （75-110 GHz）. The generation of polarization multiplexing millimeter-wave （mm-wave） wireless signal is based on the photonic technique. After 20-km fiber transmission, polarization diversity and heterodyne beating are implemented to convert the polarization components of the polarization-multiplexing signals from the optical baseband to W-band so that up to 16 Gb/s mm-wave signals can be delivered over 2-m 2~2 multiple-input multiple-output （MIMO） wireless link. At the receiver base station （BS）, polarization combination reconstructs the PDM-QPSK signal which is then launched into another 20-km fiber. In the experiment, coherent detection is introduced to improve receiver sensitivity and constant modulus algorithm （CMA） is applied for polarization de-multiplexing. The bit-error-ratio （BER） for 16-Gb/s PDM- QPSK signal delivery is below the forward-error-correction （FEC） threshold of 3.8× 10-3 with the optical signal-to-noise ratio （OSNR） above 11.8 dB.

Q-switched pulse generation from an all-f iber distributed Bragg reflector laser using graphene as saturable absorber

A Q-switched distributed Bragg reflector fiber laser using a graphene passive saturable absorber is proposed in a cavity consisting of a fiber Bragg grating and Faraday rotator mirror as end mirrors, together with a highly doped erbium-doped fiber as a gain source. The laser has a Q-switched threshold of about 28 mW and a tunable repetition rate of 10.4-18.0 kHz with varying pump power. The shortest pulse width obtained from the system is 3.7 its, with a maximum pulse energy and peak power of 22.2 nJ and 3.4 mW, respectively.

Analysis of the hydrological safety of dams combining two numerical tools:Iber and DualSPHysics

The upgrade of the hydrological safety of dams is a critical issue to avoid failures that can dramatically affect people and assets. This paper shows a numerical methodology to analyse the safety of the Belesar dam（NW, Spain） based on two different numerical codes. First, a mesh-based code named Iber, suited to deal with large 2-D domains, is used to simulate the impoundment. The initial conditions and the inlet provided to Iber correspond to the maximum water elevation and the maximum expected inflow to the impoundment defined in the technical specifications of the dam, which are associated to the more hazardous operation conditions of the dam. Iber provides information about the time needed for water to attain the crest of the dam when floodgates are closed. In addition, it also provides the velocity of discharge when gates are opened. Then, a mesh-free code named DualSPHysics, which is especially suited to deal with complex and violent 3-D flows, is used to reproduce the behaviour of one of the spillways of the dam starting from the results obtained with Iber, which are used as inlet conditions for DualSPHysics. The combined results of both model show that the left spillway can discharge the surplus of water associated to the maximum inflow to the reservoir if the gates of the spillways are opened before the overtopping of the dam was observed. In addition, water depth measured on the spillway is considerably lower than the lateral walls, preventing overtopping. Finally, velocities at different points of the spillway showed to be in good agreement with theoretical values.

Non-uniform strain measurement along a f iber Bragg grating using optical frequency domain reflectometry

A novel method of measuring non-uniform strain along a fiber Bragg grating(FBG) using optical frequency domain reflectometry(OFDR) is proposed and experimentally demonstrated. This method can overcome the problems of traditional non-uniform strain measurement methods for FBGs, i.e., the likelihood of chirping and multiple peaking in the spectrum when FBG is subjected to inhomogeneous strain fields. Wavelength interrogation is realized by OFDR with a narrow-line-width tunable laser as the optical source. When non-uniform strain distributions along areas adjacent to structural damage are measured by this method, good agreement is obtained between measurements and theoretical simulation results.

Self-starting harmonic mode-locked Tm-Bi co-doped germanate f iber laser with carbon nanotube-based saturable absorber

We report a ring cavity passively harmonic mode-locked fiber laser using a newly developed thulium- bismuth co-doped fiber （TBF） as a gain medium in conjunction with a carbon nanotube （CNT）-based saturable absorber. The TBF laser generates a third harmonic mode-locked soliton pulse train with a high repetition rate of 50 MHz and a pulse duration of 1.86 ps. The laser operates at 1 901.6 nm with an average power of 6.6 mW, corresponding to a pulse energy of 0.132 nJ, at a 1 552 nm pump power of 723.3 roW.

The reliability of the“Iberic graft”for covering of the radial forearm free flap donor site

Aim:Traditional donor site closure from radial forearm free flap(RFFF)has been associated with esthetic and functional morbidity.To avoid complications,such as color mismatch and secondary donor site morbidity,a new technique named‘‘Iberic graft’’for covering the RFFF donor site was described previously by our team.Methods:A study of patients who underwent reconstruction of head and neck defects using a RFFF was conducted to assess postoperative complications of the RFFF donor site and also to evaluate the morbidity in terms of aesthetics and function following the use of the“Iberic graft”.The donor site was covered by the use of a combined local triangular full-thickness skin graft.Color match,quality of the scar,presence of necrosis,dehiscence of the suture or tendon exposure were recorded and analyzed.Results:One hundred and twenty-five consecutive patients undergoing RFFF harvesting were included.RFFF donor site defects ranged from 15 cm2 to 70 cm2;9 patients(7%)had small dehiscences of the forearm skin graft,whereas 2 cases(1.6%)presented tendon exposure.Otherwise,partial skin graft loss occurred in a few patients.In all cases,these sites healed secondarily by conservative management,with no final impairment of function.Assessment of the forearm donor site at 1 to 3 months after the primary surgical procedure showed complete defect coverage,good color match,and no scarring along the graft line.Conclusion:The“Iberic graft”is a reliable method for closing most of RFFF donor site defects as it provides excellent color match and pliability,while obviates the need for a second surgical site.