| 1. |
- Le, Ha Vu, et al.
(author)
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Bacterial Cellulose Aerogels Derived from Pineapple Peel Waste for the Adsorption of Dyes
- 2023
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In: ACS Omega. - 2470-1343. ; 8:37, s. 33098-34195
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Journal article (peer-reviewed)abstract
- Valorization of pineapple peel waste is an attractive research topic because of the huge quantities of this byproduct generated from pineapple processing industries. In this study, the extract from pineapple waste was collected to produce a hydrogel-like form containing bacterial cellulose fibers with a three-dimensional structure and nanoscale diameter by the Acetobacter xylinum fermentation process. The bacterial cellulose suspension was subsequently activated by freeze-drying, affording lightweight aerogels as potential adsorbents in wastewater treatment, in particular the adsorptive removal of organic dyes. Intensive tests were carried out with the adsorption of methylene blue, a typical cationic dye, to investigate the influence of adsorption conditions (temperature, pH, initial dye concentration, time, and experiment scale) and aerogel-preparation parameters (grinding time and bacterial cellulose concentration). The bacterial cellulose-based aerogels exhibited high adsorption capacity not only for methylene blue but also for other cationic dyes, including malachite green, rhodamine B, and crystal violet (28-49 mg/g). However, its activity was limited for most of the anionic dyes, such as methyl orange, sunset yellow, and quinoline yellow, due to the repulsion of these anionic dyes with the aerogel surface, except for the case of congo red. It is also an anionic dye but has two amine groups providing a strong interaction with the hydroxyl group of the aerogel via hydrogen bonding. Indeed, the aerogel has a substantially large congo red-trapping capacity of 101 mg/g. Notably, the adsorption process exhibited similar performances, upscaling the solution volume to 50 times. The utilization of abundant agricultural waste in the simple aerogel preparation to produce a highly efficient and biodegradable adsorbent is the highlight of this work.
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| 2. |
- Do, Thanh Toan, et al.
(author)
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Simultaneous feature aggregating and hashing for compact binary code learning
- 2019
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In: IEEE Transactions on Image Processing. - 1941-0042 .- 1057-7149. ; 28:10, s. 4954-4969
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Journal article (peer-reviewed)abstract
- Representing images by compact hash codes is an attractive approach for large-scale content-based image retrieval. In most state-of-the-art hashing-based image retrieval systems, for each image, local descriptors are first aggregated as a global representation vector. This global vector is then subjected to a hashing function to generate a binary hash code. In previous works, the aggregating and the hashing processes are designed independently. Hence, these frameworks may generate suboptimal hash codes. In this paper, we first propose a novel unsupervised hashing framework in which feature aggregating and hashing are designed simultaneously and optimized jointly. Specifically, our joint optimization generates aggregated representations that can be better reconstructed by some binary codes. This leads to more discriminative binary hash codes and improved retrieval accuracy. In addition, the proposed method is flexible. It can be extended for supervised hashing. When the data label is available, the framework can be adapted to learn binary codes which minimize the reconstruction loss with respect to label vectors. Furthermore, we also propose a fast version of the state-of-the-art hashing method Binary Autoencoder to be used in our proposed frameworks. Extensive experiments on benchmark datasets under various settings show that the proposed methods outperform the state-of-the-art unsupervised and supervised hashing methods.
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| 3. |
- Hoang, Tuan, et al.
(author)
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Simultaneous compression and quantization: A joint approach for efficient unsupervised hashing
- 2020
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In: Computer Vision and Image Understanding. - : Elsevier BV. - 1077-3142 .- 1090-235X. ; 191
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Journal article (peer-reviewed)abstract
- For unsupervised data-dependent hashing, the two most important requirements are to preserve similarity in the low-dimensional feature space and to minimize the binary quantization loss. A well-established hashing approach is Iterative Quantization (ITQ), which addresses these two requirements in separate steps. In this paper, we revisit the ITQ approach and propose novel formulations and algorithms to the problem. Specifically, we propose a novel approach, named Simultaneous Compression and Quantization (SCQ), to jointly learn to compress (reduce dimensionality) and binarize input data in a single formulation under strict orthogonal constraint. With this approach, we introduce a loss function and its relaxed version, termed Orthonormal Encoder (OnE) and Orthogonal Encoder (OgE) respectively, which involve challenging binary and orthogonal constraints. We propose to attack the optimization using novel algorithms based on recent advance in cyclic coordinate descent approach. Comprehensive experiments on unsupervised image retrieval demonstrate that our proposed methods consistently outperform other state-of-the-art hashing methods. Notably, our proposed methods outperform recent deep neural networks and GAN based hashing in accuracy, while being very computationally-efficient.
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| 4. |
- Nguyen, Hanh N. H., et al.
(author)
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Bacterial Cellulose-Based Material from Coconut Water as Efficient Green Adsorbent for Heavy Metal Cations
- 2023
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In: Chemical Engineering and Technology. - 0930-7516 .- 1521-4125. ; 46:12, s. 2547-2559
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Journal article (peer-reviewed)abstract
- Nata de coco produced via coconut water fermentation using Acetobacter xylinum was directly applied to remove metal cations in aqueous solutions without any further chemical modification. Bacterial cellulose, contributing just 0.8 wt % to nata de coco, were randomly distributed and interconnected, yielding a three-dimensional framework with high crystallinity and porosity. Due to these characteristics and the abundant presence of electron-rich hydroxyl groups, unmodified bacterial cellulose in nata de coco exhibited a strong affinity to metal cations in water. The adsorption efficiency of nata de coco can be significantly improved to & SIM;30 and & SIM;45 mg g(-1) for Pb2+ and Fe3+, respectively, by decreasing its size by grinding to decrease its size. Notably, nata de coco can adsorb multiple cations and the uptakes were almost similar for a 100-fold scaled-up adsorption volume.
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| 5. |
- Nguyen, Khoa D., et al.
(author)
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Defect-engineered metal-organic frameworks (MOF-808) towards the improved adsorptive removal of organic dyes and chromium (vi) species from water
- 2023
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In: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1369-9261 .- 1144-0546. ; 47:13, s. 6433-6447
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Journal article (peer-reviewed)abstract
- In this work, two defective zirconium-based metal-organic frameworks (Zr-MOFs), MOF-808-OH and MOF-808-NH2, were synthesized by partially replacing the 1,3,5-benzenetricarboxylate building block with 5-hydroxyisophthalate and 5-aminoisophthalate, respectively. The structural features of the defective materials were analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at 77 K, and thermogravimetric analysis (TGA). Importantly, the number of defect sites determined via proton nuclear magnetic resonance (1H-NMR) analysis of the digested materials was approximately 7 mol% for MOF-808-OH and 3 mol% for MOF-808-NH2. The presence of the defect sites increased the number of acidic centers on Zr-clusters originating from missing-linker nodes which accounted for a remarkable adsorption capacity towards various anionic organic dyes and chromium (vi) species. Compared to standard MOF-808, the defect-engineered ones showed significant increments by 30-60% in trapping capacity for anionic contaminants including sunset yellow, quinoline yellow, methyl orange, and potassium dichromate, while they exhibited modest improvements by 5-15% in the removal of cationic dyes, namely malachite green and methylene blue.
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| 6. |
- Le, Ha V., et al.
(author)
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A sulfonate ligand-defected Zr-based metal-organic framework for the enhanced selective removal of anionic dyes
- 2024
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In: RSC Advances. - 2046-2069. ; 14:23, s. 16389-16399
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Journal article (peer-reviewed)abstract
- In this work, we introduce a novel defective analogue of the representative 6-connected zirconium-based metal-organic framework (MOF-808), by employing 5-sulfoisophthalic acid monosodium salt (H2BTC-SO3Na) as a defect inducer via a mixed-linker approach. The structural integrity and different physicochemical properties were investigated by various characterization techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen physisorption at 77 K. Additionally, proton nuclear magnetic resonance (1H-NMR), energy-dispersive X-ray (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES) were employed to confirm the presence of 6.9 mol% of the 5-sulfoisophthalate ligand within the highly crystalline MOF-808 structure. The defective material exhibited significant enhancements in the removal efficiency of various organic dyes, including approximately 64% and 77% for quinoline yellow and sunset yellow, and 56% and 13% for rhodamine B and malachite green, compared to its pristine counterpart. Importantly, the defective MOF-808 showed a remarkable selectivity toward anionic species in binary-component dyes comprising both anionic and cationic dyes.
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| 7. |
- Pham Van, Quang
(author)
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Soil Degradation of Raised-beds on Orchards in the Mekong Delta Field and Laboratory Methods
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Soil degradation is a complex process which may occur anywhere and at any time. It directly affects the physical, chemical and biological processes within the soil profile. Soil degradation can either be as a result of natural hazards or due to manmade actions, such as mismanagement on cropping patterns, soil preparation and cultivation practices. Regardless of how it is caused, soil degradation has strong negative effects on plant and soil productivity. Soil degradation can accelerate a series of processes such as erosion, compaction, loss of organic matter, loss of whole soil biota, surface sealing and contamination. This thesis presents the assessment of soil properties to improve our understanding of soil degradation on raised-bed orchards in the Vietnamese Mekong delta (MD). Measurements were made on 10 citrus plantations which had been established during a range of years from 1970 to 1998 at Hau Giang province. Soil sampling was made in the dry season of 2010 at two soil depths for each raised-bed to determine soil chemical and physical properties. The soil penetration resistance (PR) was periodically measured once a week together with soil sampling for moisture measurements during a period of 5 months. Analysis indicated the pH value of the soil was tending to decrease, nutrient imbalance and deficiency was developing, and the soil structure was deteriorating during the age since the raised-beds were originally constructed. Preventive and restorative measures need to be considered for restoring and retaining the quality of the soil and the ground water. These measures should consist of (1) neutralizing of excess acidity, (2) balancing of nutrients, (3) maintaining of soil organic matter, and (4) application of appropriate irrigation schedules.
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| 8. |
- Quach, Kha Gia, et al.
(author)
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Dyglip: A dynamic graph model with link prediction for accurate multi-camera multiple object tracking
- 2021
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In: Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition. - 1063-6919. ; , s. 13779-13788
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Conference paper (peer-reviewed)abstract
- Multi-Camera Multiple Object Tracking (MC-MOT) is a significant computer vision problem due to its emerging applicability in several real-world applications. Despite a large number of existing works, solving the data association problem in any MC-MOT pipeline is arguably one of the most challenging tasks. Developing a robust MC-MOT system, however, is still highly challenging due to many practical issues such as inconsistent lighting conditions, varying object movement patterns, or the trajectory occlusions of the objects between the cameras. To address these problems, this work, therefore, proposes a new Dynamic Graph Model with Link Prediction (DyGLIP) approach to solve the data association task. Compared to existing methods, our new model offers several advantages, including better feature representations and the ability to recover from lost tracks during camera transitions. Moreover, our model works gracefully regardless of the overlapping ratios between the cameras. Experimental results show that we outperform existing MC-MOT algorithms by a large margin on several practical datasets. Notably, our model works favorably on online settings but can be extended to an incremental approach for large-scale datasets.
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| 9. |
- Van Quang, Pham, et al.
(author)
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Soil Penetration Resistance and Its Dependence on Soil Moisture and Age of the Raised-Beds in the Mekong Delta, Vietnam
- 2012
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In: International Journal of Engineering Research and Development. - 2278-067X. ; 4:8, s. 87-96
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Journal article (peer-reviewed)abstract
- The research was conducted on 10 citrus plantations at Hau Giang province in the Mekong delta, Vietnam during one year with a portable electronic penetrometerto understand the impact of moisture on the soil compaction. Soil penetration resistance (PR) was measured in the depth of 0-80 cm depth and soil samples also taken at each 10 cm depth from the soil surface to the water level for soil moisture measurement. The results showed that PR increased as a function ofraised-bed’s age and it could be reached to a high degree by soil moisture variability during the season. The sensitivity of PR to soil moisture decreases with the age of raised-beds while the soil moisture represented an increasing tendency with the age of raised-beds. Relationship between PR and soil moisture are explained betterby the volumetric water content than the corresponding soil water potential expressed as pF values. The measurements of soil PR determined by the previous results, which are obtained from soil, core samples with the dry bulk density and water retention curves were calculated and analyzed. Using the PR data will be very useful; it is a complementary and important information for identification the soil structure and soil moisture content. Without such processing of PR measurements, the values of the PR measurements will be limited and not indicated for soil compaction. To minify soil compaction on the raised-beds, all the pressure and mechanical activities should not be done in the soil surface, specially in the wet condition. Organic fertilizers and Biocharcan be considered as soil conditioners and recommended to applied in orchard for improving soil properties.
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