| 1. |
- Zhang, Ye, et al.
(författare)
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A regularization method for the reconstruction of adsorption isotherms in liquid chromatography
- 2016
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Ingår i: Inverse Problems. - : IOP PUBLISHING LTD. - 0266-5611 .- 1361-6420. ; 32:10
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Tidskriftsartikel (refereegranskat)abstract
- Determining competitive adsorption isotherms is an open problem in liquid chromatography. Since traditional experimental trial-and-error approaches are too complex and expensive, a modern technique of obtaining adsorption isotherms is to solve the inverse problem so that the simulated batch separation coincides with actual experimental results. This is a typical ill-posed problem. Moreover, in almost all cases the observed concentration at the outlet is the total response of all components, which makes the problem more difficult. In this work, we tackle the ill-posedness with a new regularization method, which is based on the fact that the adsorption isotherms do not depend on the injection profile. The proposed method transfers the original problem to an optimization problem with a time-dependent convection-diffusion equation constraint. Iterative algorithms for solving constraint optimization problems for both the equilibrium-dispersive and the transport-dispersive models are developed. The mass transfer resistance is also estimated by the proposed inverse method. A regularization parameter selection method and the convergence property of the proposed algorithm are discussed. Finally, numerical tests for both synthetic problems and real-world problems are given to show the efficiency and feasibility of the proposed regularization method.
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| 2. |
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| 3. |
- Ye, Yin, et al.
(författare)
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Removal and recovery of aqueous U(VI) by heterogeneous photocatalysis: Progress and challenges
- 2022
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 450
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Forskningsöversikt (refereegranskat)abstract
- With the rapidly expanding implementations of nuclear power technology, the contamination of the aquatic environment by uranium is a rising environmental problem. Photocatalytic reduction of hexavalent uranium (U(VI)) is a plausible solution to the aqueous uranium contamination, which has generated increasing research interest in the recent decade. Therefore, a systematic assessment highlighting the important direction for future studies is in need. We herein present a critical review to address the following two aspects: (1) the progress and current understandings of photocatalytic U(VI) removal technology, including various applied catalysts, current understanding of the kinetics and mechanisms, the effects of key operation parameters, and the effects of co-existing water constituents; (2) key knowledge gaps that need future research efforts in this field.
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| 4. |
- Ye, Yin, et al.
(författare)
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Efficient and durable uranium extraction from uranium mine tailings seepage water via a photoelectrochemical method
- 2021
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Ingår i: iScience. - : Elsevier BV. - 2589-0042. ; 24:11
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Tidskriftsartikel (refereegranskat)abstract
- Current photocatalytic uranium (U) extraction methods have intrinsic obstacles, such as the recombination of charge carriers, and the deactivation of catalysts by extracted U. Here we show that, by applying a bias potential on the photocatalyst, the photoelectrochemical (PEC) method can address these limitations. We demonstrate that, owing to efficient spatial charge-carriers separation driven by the applied bias, the PEC method enables efficient and durable U extraction. The effects of multiple operation conditions are investigated. The U extraction proceeds via single-step one-electron reduction, resulting in the formation of pentavalent U, which can facilitate future studies on this often-overlooked U species. In real seepage water the PEC method achieves an extraction capacity of 0.67 gU m(-3).h(-1) without deactivation for 156 h continuous operation, which is 17 times faster than the photocatalytic method. This work provides an alternative tool for U resource recovery and facilitates future studies on U(V) chemistry.
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| 7. |
- Wang, Guilei, et al.
(författare)
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Integration of Highly Strained SiGe in Source and Drain with HK and MG for 22 nm Bulk PMOS Transistors
- 2017
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Ingår i: Nanoscale Research Letters. - : Springer. - 1931-7573 .- 1556-276X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the integration of SiGe selective epitaxy on source/drain regions and high-k and metal gate for 22 nm node bulk pMOS transistors has been presented. Selective Si1-xGex growth (0.35 <= x <= 0.40) with boron concentration of 1-3 x 10(20) cm(-3) was used to elevate the source/drain. The main focus was optimization of the growth parameters to improve the epitaxial quality where the high-resolution x-ray diffraction (HRXRD) and energy dispersive spectrometer (EDS) measurement data provided the key information about Ge profile in the transistor structure. The induced strain by SiGe layers was directly measured by x-ray on the array of transistors. In these measurements, the boron concentration was determined from the strain compensation of intrinsic and boron-doped SiGe layers. Finally, the characteristic of transistors were measured and discussed showing good device performance.
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| 8. |
- Wang, Xiaolong, et al.
(författare)
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Carrier Frequency Offset Estimation in the Presence of I/Q Mismatch for Wideband OFDM Systems
- 2012
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Ingår i: IEEE 55th International Midwest Symposium on Circuits and Systems (MWSCAS), 2012. - 9781467325264 ; , s. 924-927
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Konferensbidrag (refereegranskat)abstract
- This paper presents a data-aided Carrier Frequency Offset (CFO) estimation algorithm targeting the Wideband OFDM systems. Utilizing 3 consecutive preambles and processing them at frequency domain, the algorithm is robust to both Frequency Independent (F-I) and Frequency Dependent (F-D) I/Q Mismatch (I/Q-M). To evaluate the effectiveness of the proposed CFO estimation technique, we conduct extensive simulations based on Multi-Band OFDM Ultra-Wide Band wireless transmission. Compared to the ideal case when the CFO has been perfectly estimated, the performance loss at 8% Packet Error Rate (PER) is less than 0.5 dB.
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| 9. |
- Yu, Liang, et al.
(författare)
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Concentrating of vanadium oxide in vanadium rich phase(s) by addition of SiO2 in converter slag
- 2007
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 34:2, s. 131-137
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the present work was to examine whether vanadium rich phase(s) could be obtained in converter slags having high V2O5 contents. Slags from SSAB Oxelosund, Sweden and Ma Steel, China were studied. Despite of the composition difference, slags from both industries were found to contain essentially the same phases after heat treatment. No vanadium rich phase could be obtained by only heat treatment of the slag. The addition of 12 mass%SiO2 changed substantially the phase relationships in the slags. Two vanadium rich phases were detected in the slag samples with SiO2 addition. One of the phases was expected to be a solid solution of 3CaO.V2O5 and 3CaO.P2O5 with < 3 mass%SiO2 dissolved. The other vanadium rich phase had high SiO2 content. About 67-68 mass% vanadium was captured by the vanadium rich phase(s) after the treatment. The present finding would open up new opportunities for recovery of vanadium from converter slags.
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| 10. |
- Yu, Liang, et al.
(författare)
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Ultra-thin MFI membranes for olefin/nitrogen separation
- 2017
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 524, s. 428-435
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Tidskriftsartikel (refereegranskat)abstract
- The recovery of light hydrocarbons such as propylene and ethylene from vent streams in polymer plants is desirable since it opens up for more efficient conversion of the monomers with high economic value. Consequently, polymer membrane vapour-gas separation systems have been used for this purpose for decades [1,2]. However, an alternative is zeolite membranes. In this work, ultra-thin MFI zeolite membranes (0.5 µm) were used to separate propylene or ethylene from binary 20/80 olefin/nitrogen mixtures at different temperatures. The membranes were olefin selective with high permeance at all investigated temperatures. At room temperature, the permeance of propylene was 22×10-7 mol m-2 s-1 Pa-1 and the separation factor was 43, which corresponds to a separation selectivity of around 80. For a mixture of 20 mol.% ethylene in nitrogen, the maximum separation factor was 6 (corresponds to a separation selectivity of 8.4) at 277 K with an ethylene permeance of 57×10-7 mol m-2 s-1 Pa-1. The membrane selectivity was governed by more extensive adsorption of olefin, especially propylene, as compared to nitrogen. Comparing with ethylene, propylene has higher heat of adsorption, which probably caused the higher propylene/nitrogen selectivity compared to ethylene/nitrogen selectivity. The permeance and the selectivity for propylene were much higher than for commercial polymeric membranes. For ethylene, the permeance was much higher, and the selectivity was comparable to commercial polymeric membranes. Modelling showed that the pressure drop over the support limited the flux through the membranes especially at higher temperatures and in particular for the ethylene/nitrogen system with high flux. Further, modelling indicated that the result obtained at high temperatures, where the flux was high, was also affected by concentration polarization. However, for the propylene/nitrogen system at the optimum separation temperature, the pressure drop over the support and the concentration polarisation were small. The results show that ultra-thin MFI zeolite membranes are promising candidates for light olefins/nitrogen separation in polymer plants.
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