Performance and mechanisms of NaOH and ball-milling co-modified biochar for enhanced the removal of Cd2+ in synthetic water: A combined experimental and DFT study

A multifunction magnetic carbonaceous adsorbent (MBM/OH/BC) was synthesized by facile NaOH and ball-milling co-modified biochar, and applied for removing Cd²⁺ in water. The results showed MBM/OH/BC exhibited excellent adsorption capacity (183.59 mg/g for Cd²⁺), short equilibrium time (60 min) and good reusability (the declining efficiency <20% after four adsorption and desorption cycles) compared with pristine biochar. Meanwhile, the modification mechanisms of NaOH and ball-milling to biochar were explored by a series of characterizations (XRD, SEM-EDS, BET, XPS and FTIR, et al). The results indicated the remarkable adsorption performance of MBM/OH/BC was mainly attributed to the co-modification significantly increased the specific surface area, mineral content and cation exchange capacity of biochar, thereby further improving the precipitation, cation exchange and complexation with Cd²⁺. In addition, the results of adsorption mechanisms showed that the joint contribution proportion to the total adsorption capacity of precipitation, cation exchange and complexation was up to 90%, indicating the three mechanisms were the primary adsorption mechanism. To sum up, NaOH and ball-milling co-modification was an effective strategy to increase the adsorption capacity of the pristine biochar for heavy metals from water.     

Design and application of an S-box using complete Latin square

Since a substitution box (S-box) is the nonlinearity part of a symmetric key encryption scheme, it directly determines the performance and security level of the encryption scheme. Thus, generating S-box with high performance and efficiency is attracting. This paper proposes a novel method to construct S-box using the complete Latin square and chaotic system. First, a complete Latin square is generated using the chaotic sequences produced by a chaotic system. Then an S-box is constructed using the complete Latin square. Performance analyses show that the S-box generated by our proposed method has a high performance and can achieve strong ability to resist many security attacks such as the linear attack, differential attack and so on. To show the efficiency of the constructed S-box, this paper further applies the S-box to image encryption application. Security analyses show that the developed image encryption algorithm is able to encrypt different kinds of images into cipher images with uniformly distributed histograms. Performance evaluations demonstrate that it has a high security level and can outperform several state-of-the-art encryption algorithms.

     

电感耦合等离子体原子发射光谱法测定防锈铝合金中痕量钠

提出了电感耦合等离子体原子发射光谱法测定防锈铝合金中痕量钠的方法。以盐酸(1+1)溶液和过氧化氢溶解样品,选择波长588.995 nm为钠的分析线。方法的检出限(3S/N)为0.028 mg.L-1。方法用于测定防锈铝合金中痕量钠(wNa=0.000 14%～0.000 73%),加标回收率在91.4%～113.3%之间,相对标准偏差(n=6)在2.6%～5.5%之间。     

针对水质监测的紫外-可见光谱双光程融合优化算法

紫外-可见光谱法多参数水质在线监测系统面对复杂水体时,常需要频繁改变探头光程以保持光谱较高的信噪比。然而,适合的光程往往需要大量实验才可确定,难以满足在线监测系统对实时性、精度、灵敏度、稳定性等的实际需求。研究了一种紫外-可见光谱双光程融合优化算法,将同时采集的长短两种光程光谱使用了滑窗法估计它们光谱噪声方差分布,确定光谱强噪声区间;由于长短光程光谱的信号强度不同,使用了遗传算法计算得到双光谱融合的最佳增益匹配倍率;最后,按噪声方差分布使用分段加权方式得到较高信噪比的双光程融合光谱。实验结果表明,利用该法对重庆长寿湖水样、嘉陵江某排污口及邻苯二甲酸氢钾标准溶液三种样本进行测试,其融合光谱在200～250 nm区域的强噪声得到抑制,零值干扰左推至220 nm之前,样本的峰值信噪比均有显著提高,证明了算法的有效性和普适性。该算法无需大量实验以获得最佳光程,对于拓宽紫外-可见光谱水质在线监测系统的应用范围具有较为重要的现实意义。     

矩形封闭声腔壁板轻量化对声固耦合特性的影响

基于模态耦合法建立了考虑对侧柔性壁板的矩形封闭腔体声固耦合模型,导出了耦合系统声振响应随柔性板材料属性及厚度变化的近似关系.通过数值仿真计算,详细分析了单柔性板-单侧激励、双柔性板-双侧激励及双柔性板-单侧激励三种情况下板的轻量化设计对系统声固耦合特性及腔内声压响应的影响.结果表明:对于单柔性板-单侧激励及双柔性板-双侧激励情况,低频段腔内声压主要取决于板厚,其次是杨氏模量,而与板密度关系较弱.因此使用适当增厚的轻质板可以同时达到减重和低频区降噪的目标.对于双柔性板-单侧激励情况,适当的轻量化设计可以显著增强两板间低频段振动的耦合,从而降低该频段的声腔模态响应及腔内噪音.在中高频段,增加板厚和材料密度对降低三种情况的腔内声压均有利。      

Experimental determination of the micro- and macrostructural parameters influencing the acoustical performance of fibrous media

Measurements of the two characteristic lengths of 6 glass wool samples (with flow resistivities between 11,900 and 69,900 Pa s m⁻²) and 6 polyester fibre samples (with flow resistivities between 4100 and 51,000 Pa s m⁻²) have been made. These data have been used to determine the cross-sectional shape factors which are related to the characteristic lengths introduced by Allard. By using the formulas due to Bies and Allard, it has been found that the two characteristic lengths of the glass wool samples can be independently predicted from the glass fibre diameter. In respect to polyester fibre samples, a new relation between the flow resistivity, the fibre diameter and the bulk density has been proposed and examined. The accuracy of the predictions of the non-acoustical parameters has been confirmed by the measurements and predictions of the absorption coefficient using the Delany and Bazley and Allard models.     

Thermal behaviors of lithium in and on the two layers of C150H30 graphite plane: MD simulation

In order to investigate the thermal behaviors of lithium (Li) atom intercalated in and adsorbed on the graphite intercalated compound, the molecular dynamics procedure at molecular mechanics 2 level was applied to the hydrogen terminated cluster model composed of two layers of C₁₅₀H₃₀ plane. On the basis of the optimized structure, one intercalated Li atom was stabilized at the mass center and adsorbed Li was done above the center of upper plane. Both Li atoms initiate to migrate at 50 K parallel to the plane with almost the same migration rate in the temperature range from 50 to 200 K. However, their migration processes are clearly different. The former gets out of the cluster model, drawing the increasing curves accompanied by the induction period in the coordinate axes of the migration distance vs. the simulation time at every temperature. The latter, however, cannot be released from the cluster model below 150 K where it remains on the side face of the cluster model. At 50 and 100 K, it migrates from the center to the circumference periodically cannot escape from the surface of cluster model. Thus, the potential well is considered to be deeper on the surface than in the layers.     

Comment on ‘Resonant electric field enhancement in the vicinity of a bare metallic grating exposed to s-polarized light by A.A. Maradudin and A. Wirgin’: Anomalous light absorption by lamellar metallic gratings

Anomalously high light absorption by deep lamellar metallic gratings in TE polarization (electric field vector parallel to the grooves) is found numerically. When the grating period is small enough to support only the specular reflected order, almost the entire amount of incident light can be absorbed, provided that the grooves are deep and the lamellae are thin.