Comparative Leaching Study on Conichalcite and Chalcopyrite Under Different Leaching Systems

Jiajia Wu,Junmo Ahn,Jaeheon Lee 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.4

Copper leaching from low-grade copper ore samples obtained from two active mines in the US, named conichalcite (sample A) and chalcopyrite (sample B), were studied under different leaching conditions using sulfuric acid and methane sulfonic acid (MSA). The conichalcite, sample A, is calcium-copper arsenite hydroxide [CaCu(AsO4)(OH)] with small amount of gold and other metals. The copper grade is 0.41% with 0.48% arsenic and 2.04% sulfur. The chalcopyrite, sample B, was the main mineral with 0.60% copper grade with 0.73% sulfur and 0.032% molybdenum. Leaching systems utilized two oxidants (ferric ion and hydrogen peroxide) to investigate the kinetics of copper extractions. All leaching tests were performed by bottle roll leaching tests with 6.25% pulp density for 24 hours. Results showed that the leaching kinetics were relatively fast for oxidized sample A. Overall copper recovery was slightly affected by the oxidants and higher than 60% copper extraction was observed. Screen fractioned materials and the leached residue analysis showed that the copper grade in the residues are relatively consistent with 0.14-0.16% copper. This results showed that the ore samples contains readily leachable copper and refractory elements in all size fractions. The refractory portion seems to be relative uniform with wide range of easily leachable copper with 0.30 to 0.54%. Copper extraction from sample B using acids with ferric ion as an oxidant showed around 35% but it significantly increased over 80% using hydrogen peroxide as an oxidant. The copper extraction gradually increased up to 3.0 mol/L hydrogen peroxide content.

Enhanced Triboelectric Nanogenerators Based on MoS₂ Monolayer Nanocomposites Acting as Electron-Acceptor Layers

Wu, Chaoxing,Kim, Tae Whan,Park, Jae Hyeon,An, Haoqun,Shao, Jiajia,Chen, Xiangyu,Wang, Zhong Lin American Chemical Society 2017 ACS NANO Vol.11 No.8

<P>As one of their major goals, researchers attempting to harvest mechanical energy efficiently have continuously sought ways to integrate mature technologies with cutting-edge designs to enhance the performances of triboelectric nanogenerators (TENGs). In this research, we introduced monolayer molybdenum-disulfide (MoS2) into the friction layer of a TENG as the triboelectric electron-acceptor layer in an attempt to dramatically enhance its output performance. As a proof of the concept, we fabricated a vertical contact-separation mode TENG containing monolayer MoS2 as an electron-acceptor layer and found that the TENG exhibited a peak power density as large as 25.7 W/m(2), which is 120 times larger than that of the device without monolayer MoS2. The mechanisms behind the performance enhancement, which are related to the highly efficient capture of triboelectric electrons in monolayer MoS2, are discussed in detail. This study indicates that monolayer MoS2 can be used as a functional material for efficient energy harvesting.</P>

Resource Allocation for Relay-Aided Cooperative Systems Based on Multi-Objective Optimization

( Runze Wu ),( Jiajia Zhu ),( Hailin Hu ),( Yanhua He ),( Liangrui Tang ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.5

This paper studies resource allocation schemes for the relay-aided cooperative system consisting of multiple source-destination pairs and decode-forward (DF) relays. Specially, relaying selection, multisubcarrier pairing and assignment, and power allocation are investigated jointly. We consider a combinatorial optimization problem on quality of experience (QoE) and energy consumption based on relay-aided cooperative system. For providing better QoE and lower energy consumption we formulate a multi-objective optimization problem to maximize the total mean opinion score (MOS) value and minimize the total power consumption. To this end, we employ the nondominated sorting genetic algorithm version II (NSGA-II) and obtain sets of Pareto optimal solutions. Specially, two formulas are devised for the optimal solutions of the multi-objective optimization problems with and without a service priority constraint. Moreover, simulation results show that the proposed schemes are superior to the existing ones.

Experimental study of vibration characteristics of FRP cables based on Long-Gauge strain

Qi Xia,JiaJia Wu,XueWu Zhu,Jian Zhang 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.6

Steel cables as the most important components are widely used in the certain types of structures such as cablesupported bridges, but the long-span structures may result in an increase in fatigue under high stress and corrosion of steel cables. The traditional steel cable is becoming a more evident hindrance. Fiber Reinforced Polymer (FRP) cables with lightweight, high-strength are widely used in civil engineering, but there is little research in vibrational characteristics of FRP cables, especially on the damping characteristic. This article studied the two methods to evaluate dynamical damping characteristic of basalt FRP(BFRP) and glass FRP(GFRP) cables. First, the vibration tests of the B/G FRP cables with different diameter and different cable force were executed. Second, the cables forces were calculated using dynamic strain, static strain and dynamic acceleration respectively, which were further compared with the measured force. Third, experimental modal damping of each cables was calculated by the half power point method, and was compared with the calculation by Rayleigh damping theory and energy dissipation damping theory. The results indicate that (1) The experimental damping of FRP cables decreases with the increase of cable force, and the trend of experimental damping changes is roughly similar with the theoretical damping. (2) The distribution of modal damping calculated by Rayleigh damping theory is closer to the experimental results, and the damping performance of GFRP cables is better than BFRP cables.

Comparative studies of novel biooxidation process to low-grade sulphide gold ores

Ahn Junmo,Wu Jiajia,Lee Jaeheon 한국자원공학회 2022 Geosystem engineering Vol.25 No.4

The Sand Farming is one of novel biooxidation processes suitable for sulphide oxidation of lowgrade refractory gold ores. It has been previously proven to be feasible and more efficient compared to other conventional sulphide oxidation processes. In this study, the Sand Farming was compared with conventional tank biooxidation to investigate biooxidation behaviors on ores with different mineralogy and compare the ultimate gold recovery. Ore samples were tested for Sand Farming biooxidation. Conventional tank biooxidation was also compared as the baseline. After each biooxidation was completed, cyanidation was conducted for gold extraction. The Sand Farming achieved the gold recovery of 75% from high grade with higher sulphur content sample (Sample A) and 68% from low grade with lower sulphur content sample (Sample B), slightly lower than tank biooxidation of 83% and 85%, respectively. Sand Farming can be an alternative to several sulphide oxidation processes with better overall economics.

Effects of Sintering Process on Microstructure and Microwave Dielectric Properties of Ba(Co1/3Nb2/3)O3 Ceramics

Zhefei Wang,Jiajia Wu,Lixi Wang,Zhenxiao Fu,Qitu Zhang 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.6

Ba(Co1/3Nb2/3)O3 (BCN) ceramics were prepared using a conventional solid-state route. Effects of sintering on microstructure and microwave dielectric properties of Ba(Co1/3Nb2/3)O3 ceramics were systematically investigated. Appropriate sintering temperature could restrain the evaporation of CoO and the formation of Nb-rich phase. The dielectric constants and temperature coefficients of resonant frequency changed slightly with the variation in sintering temperatures. The high Q× f value with prolonged sintering time was related to the improvement of 1 : 2 ordered arrangement in the B site, rather than the compactness of ceramics. Excellent microwave dielectric properties (εr=32.6, Q×f =86857 GHz, τf=−14 ppm/°C) were obtained in the Ba(Co1/3Nb2/3)O3 ceramics sintered at 1380°C for 12 h.

Optimizing the chlorine evolution reaction performance of Co(OH)2 catalyst for enhanced antifouling ability

Yating Peng,Peng Wang,Jiawei Li,Jiajia Wu,Feng Lin,Dun Zhang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.118 No.-

Underwater optical instruments are commonly plagued by biofouling. As one of the most useful antifoulingstrategies, electrochemical chlorination is able to prevent biofouling efficiently, but the limited activityand selectivity in chlorine evolution reaction (CER) restrict its practical applications. To address thisproblem, we focus on the optimization of CER performance of cobalt-based catalysts. In this work, weprepared Co(OH)2 with different forms, morphologies, and intercalations. By adopting linear sweepvoltammetry and electrochemical active surface area analysis, it is demonstrated that the a-Co(OH)2exhibits better CER performance than b-Co(OH)2 does, and the manipulation of a-Co(OH)2 morphologycan help to further enhance CER performance. Meanwhile, the intercalation of a-Co(OH)2 plays a minorrole in the CER. Furthermore, based on the screened synthetic condition, the optimized a-Co(OH)2 wasapplied for practical antifouling examination, and its excellent antifouling ability was verified by theinvestigation on bacteria attachment and glass transmittance. The findings in this work not only enrichour understanding on the effects of synthetic conditions on CER performance of cobalt-based catalysts,but also provide useful insights into the development of electrochemical antifouling strategies.

A Novel Xylanase from Streptomyces sp. FA1: Purification, Characterization, Identification, and Heterologous Expression

Jie He,Lingqia Su,Xiaojun Sun,Jiajia Fu,Jian Chen,Jing Wu 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.1

A xylanase (XynA) was purified from the culturemedium of Streptomyces sp. FA1, which was previouslyisolated from a bamboo retting system. XynA had amolecular mass of 43 kDa, displayed maximal activity atpH 5.5, retained 41% of its maximal activity at pH 11.0,and was stable over a wide pH range (3.0 ~ 11.0). PurifiedXynA was subjected to peptide mass fingerprinting, whichled to the cloning of the xynA gene. The xynA gene, whichencodes a mature protein of 436 amino acids, washeterologously expressed in E. coli BL21(DE3). The activityin the culture medium could reach 213.5 U/mL, which was11.2-fold higher than that produced by Streptomyces sp. FA1. BLAST searching revealed that full-length XynAshares less than 90% identity with most of its homologues,whereas amino acids 48-436 of the enzyme share 97%identity with an open reading frame encoding a putativefull-length mature xylanase from Streptomyces tendae. Thetruncated xynA gene, xynA48-436, was cloned and expressedin E. coli, however, no xylanase activity could be detectedin the culture medium. Based on these results, it is suggestedthat XynA is a new member of glycoside hydrolasesfamily10 with exceptional catalytic efficiency at alkalinepH.

Experimental Investigation on Flexural Behavior of Reinforced Ultra High Performance Concrete Low-Profile T-Beams

Minghong Qiu,Xudong Shao,Kay Wille,Banfu Yan,Jiajia Wu 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.2

The flexural behavioral properties of ultra high performance concrete (UHPC) low-profile T-beams reinforced with a combination of steel fibers and steel reinforcing bars were investigated in this paper. Five large scale T-beams were tested and analyzed regarding their deflection, ductility, strain, curvature, load capacity and crack development. The experimental variables include the reinforcement ratio, the slenderness (length to diameter ratio) of the fiber reinforcements, and the fiber type. The experiments showed that all specimens exhibit flexural failure with the yielding of steel bars and excessive expansion of flexural crack, and the compression zone in the reinforced UHPC low-profile T-beam is not crushed because of the ultra high compressive strength and area of UHPC. In addition, it was concluded that using hooked-end fibers can effectively increase the specimen’s durability-based cracking load in comparison to straight fibers of same slenderness, whereas the reinforcement ratio and the slenderness of the fibers have little influence on this. Increasing the reinforcement ratio and using hooked-end instead of straight fibers increase the load capacity and bending stiffness of the specimen, as well as reduces the crack width at comparable applied load. A model was established to compute the ultimate capacity of UHPC low-profile T-beams and the prediction agrees well with the experimental results in the present and published investigations.

Synthesis, and antioxidant, thrombin-inhibitory, and anticancer activities of hydroxybenzamide derivatives

Jin-Rui Wei,Kun Liu,Faquan Lin,Chunping He,Xuan Luo,Jiajia Zou,Wei He,Wenqian Nong,Cui-Wu Lin 한국응용생명화학회 2016 Applied Biological Chemistry (Appl Biol Chem) Vol.59 No.2

Four hydroxybenzamide derivatives were synthesized from protocatechuic acid. The antioxidant activities of these derivatives were evaluated in vitro using DPPH radical scavenging and reducing power assays. In addition, these compounds were subjected to a chromogenic thrombin-inhibitory assay using Chromozym-TH as the substrate. The anticancer effects of these derivatives were also investigated using the MTT assay in three human cancer cell lines. Four derivatives exhibited excellent DPPH radical scavenging activity and redox potential. Their highly inhibitory effect against thrombin may allow them to be utilized as novel micromolecule thrombin inhibitors. Furthermore, four derivatives demonstrated different inhibitory activities in three human cancer cell lines but showed minimal harmful effects on normal HUVEC cells. Therefore, hydroxybenzamide derivatives indicate the superior antioxidant, thrombin-inhibitory, and anticancer activities along with the excellent biocompatibility, which have the potential application in therapeutic interventions and disease prevention of cancer, thrombotic diseases, and aging.