Superconvergent Cluster Recovery Method for the Crouzeix-Raviart Element

In this paper, we propose and numerically investigate a superconvergent cluster recovery (SCR) method for the Crouzeix-Raviart (CR) element. The proposed recovery method reconstructs a $C^0$ linear gradient. A linear polynomial approximation is obtained by a least square fitting to the CR element approximation at certain sample points, and then taken derivatives to obtain the recovered gradient. The SCR recovery operator is superconvergent on uniform mesh of four patterns. Numerical examples show that SCR can produce a superconvergent gradient approximation for the CR element, and provide an asymptotically exact error estimator in the adaptive CR finite element method.     

电商平台主导的E-闭环供应链定价、服务决策与回收模式

E-闭环供应链(E-CLSC)管理须有科学的定价与服务决策支撑。针对集中和分散回收模式,构建电商平台主导的Stackelberg博弈模型,研究E-CLSC定价与平台服务决策。通过对产品销售价格、平台服务水平等均衡策略分析,揭示回收主体投资有效性、回收转移价格等对E-CLSC均衡策略影响。研究表明:集中回收模式优于分散回收模式;在分散回收模式下,若回收主体投资有效性相同,制造商、平台均偏好制造商回收模式;平台回收与第三方回收模式相比,产品销售价格、平台服务水平相同,前者回收渠道效率较高;平台回收模式下,单位佣金与回收转移价格负相关,产品销售价格、平台服务水平、废旧产品回收率均与回收转移价格无关;若回收主体投资有效性差异程度较大,制造商回收模式并非总是最优的,回收主体投资有效性差异显著影响产品销售价格、回收渠道效率、平台服务水平和E-CLSC各成员利润。上述结论通过数值仿真进行了验证。     

多次放电的激光诱导击穿光谱信号增强

激光诱导击穿光谱技术(LIBS)是一种广泛应用于科学和工程方面的元素分析技术。LIBS测量一些微量元素时存在探测极限高的不足,因此增强LIBS信号强度,降低元素探测极限,对扩展其应用范围有着重要的意义。为了实现LIBS光谱信号的增强,提出多次放电增强激光诱导击穿光谱方法,并以固体铝合金材料为例进行了光谱信号强度增强的研究。实验发现,激光作用在铝合金材料上烧蚀样品产生等离子体并溅射到样品上方高压放电电极所在区域,该区域在等离子体产生之后50 μs之内均可以诱导高压电极放电。因此采用高频脉冲电源可以实现一次LIBS产生的等离子体诱导电极多次放电。多次放电会对等离子体进行多次激发,同时多次放电对等离子的加热作用会延缓等离子体冷却速率从而延长等离子体的持续时间,两者共同作用可以增强LIBS光谱信号强度,进而降低LIBS对微量元素的探测极限。使用频率为100 kHz的高频直流脉冲电源,利用数字延迟脉冲发生器同步激光与高压电源,在激光过后3.6 μs触发高压放电,一次LIBS产生的等离子体可以诱导电极5次放电,即对等离子体进行5次激发和加热。利用光谱仪对5次放电等离子体光谱进行积分测量。实验结果表明：使用多次放电增强之后,等离子体持续时间得到大幅延长,光谱信号强度得到大幅增强,其中,Mg Ⅱ (~279 nm)的信号强度可以增强约48倍,Al Ⅱ (~358 nm)的信号强度可以增强约72倍,微量元素Mn Ⅰ (~403 nm)的信号强度增强约6.3倍,微量元素Cu Ⅰ (~403 nm) 的信号强度增强约8.3倍。Mn Ⅰ (~403 nm)和Cu Ⅰ (~403 nm) 的探测极限分别降低为LIBS单次放电的1/6和1/8。多次放电增强激光诱导击穿光谱方法很好地增强了LIBS的光谱信号强度,降低了对微量元素的探测极限,扩展了LIBS技术的应用范围。该方法有潜力应用到贵重物品、稀有材料及文物的鉴定之中。     

A novel image tamper localization and recovery algorithm based on watermarking technology

In this paper, an effective self-embedding fragile watermarking scheme is presented. The watermark is generated by encoding the DCT coefficients of each 2 × 2 block and embedded into another block according to the block mapping. A non-linear chaotic sequence is used for generating the block mapping which can enhance the security of the algorithm. An improved tamper localization and recovery algorithm are performed. The experiment results show that the watermarked image has a high average peak signal-to-noise ratio. Furthermore, the tamper region can be successfully localized and exactly recovered, even if for the content-only tampering.     

First-return integrals

Properties of first-return integrals of real functions defined on the unit interval are explored. In particular, first-return integrals are shown to be continuous but not absolutely continuous.     

Optimizing thermography depth probing with a dynamic thermal point spread function

Derivation of two point spread functions PSFs suitable for infrared thermograms analysis is illustrated, based on two unique approaches, one based on depth decaying limit and one on diffusion limit. Experimental work using PMMA sample with back drilled holes and pulsed thermographic routine is utilized to show the effectiveness of deconvoluting pixel temperature transient history with suggested PSF’s. Synthetic second time derivative thermograms are utilized for comparison and the signal to noise ratio is used as a figure of merit for quantification.     

Modelling and optimization of carbon-in-pulp gole recovery processs

The paper presents a mixed-integer nonlinear programming (MINLP)approach to construction and operational optimization of carbon-in-pulp(CIP) processes related to hydrometallurgical gold recoveryplants. In this plant section, gold in the form of aurocyanidecomplex ions is adsorbed on the active sites of carbon particles.This takes place in a series of agitated tanks where carbonis countercurrently transferred with respect to the pulp. Threebasic process operating modes are reported and analysed: namelycarousel, continuous, and sequential. The mathematical modelof the CIP process is developed for each one of the operatingmodes examined. Economic evaluation is carried out proposingthe sum of annual gold loss to the tailings plus the total annualcost as a minimization object subject to constraints dictatedby the process model. The original problem is suitably decomposedinto a series of nonlinear programming problems and solved withsuccessive quadratic programming techniques. A characteristiccase study is presented to demonstrate the effectiveness ofthe proposed method.     

Crosslinked Copolyimide Membranes for Phenol Recovery from Process Water by Pervaporation

The effectiveness of different copolyimide membranes in the process of recovering phenol from water by pervaporation has been investigated. The polyimides were obtained by the polycondensation of 6FDA (4,4′-hexafluoro-isopropylidene diphthalic anhydride) with different diamines. The diamines 4MPD (2,3,5,6-tetramethyl-1,4-phenylene diamine), 6FpDA (4,4′-hexafluoro-isopropylidene dianiline), 6FpODA (4,4′-bis-(4′-aminophenoxyphenyl)hexafluoropropane), and DABA (3,5-diaminobenzoic acid) as a monomer providing a crosslinkable group, were used. In order to reach chemical stability at high phenol concentrations, the polymer structures were crosslinked with 1,10-decanediol and OFHD (2,2,3,3,4,4,5,5-octafluorohexanediol). Pervaporation experiments were performed at 60 °C, covering a concentration range of phenol between 2 and 11 wt. %. The best separation characteristics were obtained with a 6FDA-6FpDA/DABA 2:1 membrane crosslinked with 1,10-decanediol. Using a 7.8 wt. % phenol feed mixture, a total flux of 14 kg μm m⁻² h⁻¹ was reached with an enrichment of 40 wt. % phenol in the permeate. It was found that conditioning the membrane using high phenol concentrations (between 8 and 11 wt. %) is a necessary pretreatment in order to enhance the flux and improve enrichment, especially if process water with low phenol concentrations is to be treated. In addition to the experimental results, a comparison with rubbery membrane materials is presented in the discussion.     

Recovery of organic acids from fermentation broths

Rising concerns over the use of fossil resources have generated renewed interest in the production of commodity chemicals via fermentation. Organic acids are a particularly attractive target because their functionality enables downstream catalytic upgrading to a variety of compounds. In this article, we survey how common technical issues are addressed in the recovery schemes for several organic acids. We present results for the recovery of acetate using a new method based on amine complexation. Our reactive separation scheme produces a high-purity product, is energy efficient, and avoids the coproduction of a waste salt coproduct, all prerequisites for a large-scale production process.     

On timing Jitter in wavelength-division multiplexed soliton systems

Collision-induced timing shifts in a wavelength-division multiplexed soliton system are computed when damping, amplification, filtering and positive dispersion management following the loss profile are included. A statistical analysis is presented which takes into account the resulting effect of the large number of collisions occurring in the fiber. Analytic expressions are derived for the root mean square timing jitter and the maximum length of error-free transmission with an arbitrary number of channels. An extensive analysis of system performance corresponding to situations with and without filters and/or dispersion management is carried out.