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排序方式: 共有839条查询结果,搜索用时 15 毫秒
41.
Isa MH Ibrahim N Aziz HA Adlan MN Sabiani NH Zinatizadeh AA Kutty SR 《Journal of hazardous materials》2008,152(2):662-668
This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution. 相似文献
42.
Pooneh Bagheri Zadeh Akbar Sheikh Akbari Tom Buggy John Soraghan 《Multimedia Tools and Applications》2010,49(2):347-370
In this paper a novel multiresolution human visual system and statistically based image coding scheme is presented. It decorrelates
the input image into a number of subbands using a lifting based wavelet transform. The codec employs a novel statistical encoding
algorithm to code the coefficients in the detail subbands. Perceptual weights are applied to regulate the threshold value
of each detail subband that is required in the statistical encoding process. The baseband coefficients are losslessly coded.
An extension of the codec to the progressive transmission of images is also developed. To evaluate the performance of the
coding scheme, it was applied to a number of test images and its performance with and without perceptual weights is evaluated.
The results indicate significant improvement in both subjective and objective quality of the reconstructed images when perceptual
weights are employed. The performance of the proposed technique was also compared to JPEG and JPEG2000. The results show that
the proposed coding scheme outperforms both coding standards at low compression ratios, while offering satisfactory performance
at higher compression ratios. 相似文献
43.
Sarrafan Atabak Zareh Seiyed Hamid Khayyat Amir Ali Akbar Zabihollah Abolghassem 《Journal of Mechanical Science and Technology》2012,26(4):1179-1196
Magnetorheological (MR) damper is a prominent semi-active control device to vibrate mitigation of structures. Due to the inherent
non-linear nature of MR damper, an intelligent non-linear neuro-fuzzy control strategy is designed to control wave-induced
vibration of an offshore steel jacket platform equipped with MR dampers. In the proposed control system, a dynamic-feedback
neural network is adapted to model non-linear dynamic system, and the fuzzy logic controller is used to determine the control
forces of MR dampers. By use of two feedforward neural networks required voltages and actual MR damper forces are obtained,
in which the first neural network and the second one acts as the inverse dynamics model, and the forward dynamics model of
the MR dampers, respectively. The most important characteristic of the proposed intelligent control strategy is its inherent
robustness and its ability to handle the non-linear behavior of the system. Besides, no mathematical model needed to calculate
forces produced by MR dampers. According to linearized Morison equation, wave-induced forces are determined. The performance
of the proposed neuro-fuzzy control system is compared with that of a traditional semi-active control strategy, i.e., clipped
optimal control system with LQG-target controller, through computer simulations, while the uncontrolled system response is
used as the baseline. It is demonstrated that the design of proposed control system framework is more effective than that
of the clipped optimal control scheme with LQG-target controller to reduce the vibration of offshore structure. Furthermore,
the control strategy is very important for semi-active control. 相似文献
44.
Kazem Dindar Safa Akbar Hassanpour Shahin Tofangdarzadeh 《Journal of Polymer Research》2010,17(5):719-724
Various bis(silyl)ethenyl groups were attached to the aromatic ring of poly(α-methylstyrene) via Peterson olefination reaction of (RMe2Si)3CLi (R = H, Me and Ph) with formylated poly(α-methylstyrene) (Pα-MS-CHO) to give poly(α-methylstyrene)-co-[2,2-bis(silyl)ethenyl(α-methylstyrene)] as functionalized poly(α-methylstyrene) (Pα-MS-SiMe2H, Pα-MS-SiMe3 and Pα-MS-SiMe2Ph). The trimethylsilyl groups of Pα-MS-SiMe3 have been converted to 2,2-dibromoethenyl and epoxybis(silanes) groups via NBS-based bromodesilylation and MCPBA-based epoxidation respectively. The thermal degradation behaviors of the polymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 相似文献
45.
Maryam Saeidifar A. Khanlarkhani M. Eslami-Moghaddam Hassan Mansouri-Torshizi Ali Akbar Saboury 《Polycyclic Aromatic Compounds》2016,36(1):40-57
The interaction of 1, 10-phenanthroline octhyldithiocarbamato palladium(II) nitrate ([Pd(Oct-dtc)(phen)]NO3) with human serum albumin (HSA) has been investigated by various spectroscopic techniques under physiological conditions. Here, HSA was titrated with the Pd(II) complex, followed by UV–Vis absorption spectroscopy to estimate a binding constant (Kb) and other thermodynamic parameters. The results indicate that the Pd (II) complex has a high affinity for bind HSA. Thermodynamic analysis showed that the enthalpy (ΔH°) and entropy changes (ΔS°) are positive and Gibbs free energy change (ΔG°) is negative which indicated that hydrophobic interactions played the predominant role in the binding process. Fluorescence spectroscopy were used to show the mechanism and binding parameters of this interaction. Utilizing the Stern–Volmer equation, the Pd(II) complex quenched the intrinsic fluorescence of HSA via a static quenching procedure. The specific binding distances between the tryptophan (donor) proteins and Pd(II) complex (acceptor) were estimated by Forster resonance energy transfer. The CD results also showed the conformational changes on serum albumin upon binding with the Pd(II) complex. 相似文献
46.
47.
Ali Akbar Amooey Shahram Ghasemi Seyed Mohammad Mirsoleimani-azizi Zohreh Gholaminezhad Mohammad Javad Chaichi 《Korean Journal of Chemical Engineering》2014,31(6):1016-1020
Electrocoagulation (EC) is an electrochemical method to treat polluted wastewaters and aqueous solutions. In this paper, the removal of Diazinon was studied by EC on aluminum electrode. The effect of several parameters such as initial concentration of Diazinon, current density, solution conductivity, effect of pH, and electrolysis time were investigated on EC performance. The obtained results showed that the removal efficiency of EC depends on the current density, initial concentration of Diazinon and electrolysis time. The optimum pH is 3 and also the solution conductivity has no significant effect on removal efficiency. 相似文献
48.
Abu Zafar M. Shahriar M. Mostofa Akbar M. Sohel Rahman Muhammad Abdul Hakim Newton 《The Journal of supercomputing》2008,43(3):257-280
This paper presents a multiprocessor based heuristic algorithm for the Multi-dimensional Multiple Choice Knapsack Problem
(MMKP). MMKP is a variant of the classical 0–1 knapsack problem, where items having a value and a number of resource requirements
are divided into groups. Exactly one item has to be picked up from each group to achieve a maximum total value without exceeding
the resource constraint of each type. MMKP has many real world applications including admission control in adaptive multimedia
server system. Exact solution to this problem is NP-Hard, and hence is not feasible for real time applications like admission
control. Therefore, heuristic solutions have been developed to solve the MMKP. M-HEU is one such heuristic, which solves the
MMKP achieving a reasonable percentage of optimality. In this paper, we present a multiprocessor algorithm based on M-HEU,
which runs in O(T/p+s(p)) time, where T is the time required by the algorithm using single processor, p is the number of processors and s(p), a function of p, is the synchronization overhead. We also present the worst-case analysis of our algorithm, the computation of the optimal
number of processors as well as the lower bound of the total value that can be achieved by the heuristic. 相似文献
49.
The transport of particles with diameters in the range of 50 nm to 1 μm in laminar free convection of air in square enclosures was numerically investigated by an Eulerian–Lagrangian method. Two-dimensional square enclosures with widths from 2.5 mm to 5 cm, with two adiabatic surfaces and 100 and 200 °C temperature difference between the other two surfaces, were considered. The Rayleigh numbers varied from 100 to 8×105. The air flow was simulated in Eulerian frame using a commercial CFD software, whose predictions were compared with published benchmark results. Lagrangian particle transport calculations were carried out by tracking 1000 particles that were initially randomly distributed in the flow field, and assuming one-way coupling between the particles and the carrier gas. Particle motion mechanisms considered included gravity, drag, lift force, thermophoresis and Brownian dispersion.The results showed that at Rayleigh numbers lower than about 10 000 the entire flow field was dominated by a single recirculation pattern. For these low Rayleigh number cases most of the particles disperse towards the walls, while a fraction of particles were trapped in a quasi-steady recirculation zone. Inside this recirculation zone the particles were at quasi-equilibrium with respect to the hydrodynamic and dispersive forces that acted on them, and left the zone due to Brownian dispersion only at a very low rate. This quasi-equilibrium zone was not observed at the higher Rayleigh numbers where a single recirculation pattern no longer governed the entire flow field. The results also confirmed the important role of thermophoresis and Brownian dispersion, in particular for submicron size particles. 相似文献
50.
Arezoo Khosravi Hadi Baharifar Mohamad Hasan Darvishi Ali Akbar Karimi Zarchi 《IET nanobiotechnology / IET》2020,14(9):899
Tissue plasminogen activator (tPA) a thrombolytic agent is commonly used for digesting the blood clot. tPA half‐life is low (4–6 min) and its administration needs a prolonged continuous infusion. Improving tPA half‐life could reduce enzyme dosage and enhance patient compliance. Nano‐carries could be used as delivery systems for the protection of enzymes physically, enhancing half‐life and increasing the stability of them. In this study, chitosan (CS) and polyethylene glycol (PEG) were used for the preparation of CS‐g‐PEG/tPA nanoparticles (NPs) via the ion gelation method. Particles’ size and loading capacity were optimised by central composite design. Then, NPs cytotoxicity, release profile, enzyme activity and in vivo half‐life and coagulation time were investigated. The results showed that NPs does not have significant cytotoxicity. Release study revealed that a burst effect happened in the first 5 min and resulted in releasing 30% of tPA. Loading tPA in NPs could decrease 25% of its activity but the half‐life of it increases in comparison to free tPA in vivo. Also, blood coagulation time has significantly affected (p ‐value = 0.041) by encapsulated tPA in comparison to free tPA. So, CS‐g‐PEG/tPA could increase enzyme half‐life during the time and could be used as a non‐toxic candidate delivery system for tPA.Inspec keywords: drug delivery systems, nanofabrication, drugs, nanomedicine, coagulation, biomedical materials, cellular biophysics, enzymes, biochemistry, toxicology, molecular biophysics, biological tissues, blood, nanoparticles, polymersOther keywords: chitosan‐g‐PEG grafted nanoparticles, half‐life enhancer carrier, tissue plasminogen activator delivery, tPA half‐life, prolonged continuous infusion, enzyme dosage, polyethylene glycol, cytotoxicity, enzyme activity, encapsulated tPA, enzyme half‐life, blood coagulation, time 5.0 min 相似文献