Control of the VIV of a cantilevered square cylinder with free-end suction

Li Ying,Li Shiqing,Zeng Lingwei,Wang Hanfeng 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.1

A steady slot suction near the free-end leading edge of a finite-length square cylinder was used to control its aerodynamic forces and vortex-induced vibration (VIV). The freestream oncoming flow velocity (U∞) was from 3.8 m/s to 12.8 m/s. The width of the tested cylinder d = 40 mm and aspect ratio H/d = 5, where H was the height of the cylinder. The corresponding Reynolds number was from 10,400 to 35,000. The tested suction ratio Q, defined as the ratio of suction velocity (Us) at the slot over the oncoming flow velocity at which the strongest VIV occurs (Uv), ranged from 0 to 3. It was found that the free-end slot suction can effectively attenuate the VIV of a cantilevered square cylinder. In the experiments, the RMS value of the VIV amplitude reduced quickly with Q increasing from 0 to 1, then kept approximately constant for Q ≥ 1. The maximum reduction of the VIV occurs at Q = 1, with the vibration amplitude reduced by 92% , relative to the uncontrolled case. Moreover, the overall fluctuation lift of the finite-length square cylinder was also suppressed with the maximum reduction of 87%, which occurred at Q = 1. It was interesting to discover that the free-end shear flow was sensitive to the slot suction near the leading edge. The turbulent kinetic energy (TKE) of the flow over the free end was the highest at Q = 1, which may result in the strongest mixing between the high momentum free-end shear flow and the near wake.

A drug delivery system constructed by a fusion peptide capturing exosomes targets to titanium implants accurately resulting the enhancement of osseointegration peri-implant

Li Xuewen,Liu Zihao,Xu Shendan,Ma Xinying,Zhao Zhezhe,Hu Han,Deng Jiayin,Peng Cheng,Wang Yonglan,Ma Shiqing 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Exosomes derived from bone marrow mesenchymal stem cells (BMSC-exos) have been shown triggering osteogenic differentiation and mineralization of MSCs, but exosomes administered via bolus injections are rapidly sequestered and cleared. Therefore, we considered the implant as a new organ of patient’s body and expected to find a method to treat implant with BMSC-exos in vivo directly.A fusion peptide (PEP), as a drug delivery system (DDS) which contained a titanium-binding peptide (TBP) possessing the ability to selectively bind to the titanium surface and another peptide CP05 being able to capture exosomes expertly, is constructed to modify the titanium surface.Both in vitro and in vivo experiments prove PEP retains the ability to bind titanium and exosome simultaneously, and the DDS gain the ability to target exosomes to titanium implants surface following enhancing osseointegration post-implantation. Moreover, the DDS constructed by exosomes of diverse origins shows the similar combination rate and efficiency of therapy.This drug delivery system demonstrates the concept that EXO-PEP system can offer an accurate and efficient therapy for treating implants with long-term effect.

A study of a new hybrid vibration energy harvester based on broadband-multimode

Bing Chen,Shiqing Li,Xiaolei Tang,Lijie Zhang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.1

To improve the energy conversion efficiency and working frequency bandwidth of a single frequency piezoelectric vibration energy harvester, a new type of hybrid vibration energy harvester is developed which is combined with the mechanism of piezoelectric and electromagnetic energy conversion. The system comprises of a PZT cantilever beam, an elastic suspended magnetic mass, a magnet block attached to the end of the cantilever beam and a resonator. The addition of resonator can not only increase the mode, but also adjust the frequency of harvester flexibly. Nonlinear magnetic force of magnet block not only broadens the frequency band and improves the output performance of the system, but also changes the resonant frequency to make the harvester have better adjustable performance. On this basis, an improved electromechanical coupled analytical model of continuum is proposed which can be solved by the Runge-Kutta algorithm and the influence of different factors (the mass and spring stiffness of the resonator, as well as the electromechanical coupling coefficient, electromagnetic coupling coefficient, magnet mass and magnetic flux) on the output are analyzed. According to the prototype of the vibration energy harvester developed, an experimental system was built. The performance of the independent and hybrid energy harvesters is evaluated by experimental and analytical methods. The peak output voltage of the piezoelectric part was about 4 times that of the electromagnetic part. The peak output current of the electromagnetic part is about 30 times that of the piezoelectric part. The study results show that the proposed new hybrid vibration energy harvester can achieve a wider frequency range and multimodal vibration energy harvesting. In addition, the bandwidth and power of the harvester can be dynamically adjusted by changing the resonator or electromechanical coupling coefficient, and the bandwidth of the harvester can also be adjusted by changing the quality and characteristics of the magnet.

Effect of Heat Treatment on Microstructure and Properties of FGH4096M Superalloy Processed by Selective Laser Melting

Zhibo Hao,Tian Tian,Shiqing Peng,Changchun Ge,Xinggang Li,Chonglin Jia,Chuan Guo,Qiang Zhu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8

A self-designed nickel-based superalloy, designated as FGH4096M, was prepared by selective laser melting (SLM). Differentheat treatments were performed to improve the mechanical properties of the SLM alloy through optimizing the microstructuresand the features of γ′ precipitates. Compared with the as-deposited alloy, the columnar grains with dendritic structuresand equiaxed structures were retained in the alloy after direct aging, but a large amount of tertiary γ′ phase precipitated,especially around the sub-grain boundaries, resulting in the highest tensile strength but the lowest elongation. During solidsolution and aging treatment (SSA), the recovery and recrystallization occurring in the alloy facilitated the grains to beequiaxed with the increase of solution temperature. For lower solution temperature (below 1100 ℃), the secondary γ′ precipitatesdecreased with the increase of solution temperature, while the tertiary γ′ precipitates from the subsequent agingprocess gradually increased; for higher solution temperature over 1100 ℃, exceeding the complete dissolution temperatureof the γ′ phase, only tertiary γ′ precipitates from the subsequent aging process were uniformly distributed in the alloy. Afterdouble solid solution (1170 ℃ + 1050 ℃) + aging heat treatment (DSSA), there were three sizes of γ′ precipitates in thealloy. In general, the SLM + SSA (1130 ℃) alloy obtained the best comprehensive properties, which could be related tothe homogenized microstructures and the uniform and dense distribution of single sized tertiary γ′ precipitates in the alloy.

Effect of Low-Temperature Heat Treatment on PM2.5 Adsorption Properties of GO Films

Weiwu Zou,Baoshan Gu,Shiqing Sun,Shidong Wang,Xin Li,Haoqi Zhao,Peiyan Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01

To explore the mechanism of GO acting on PM 2.5, a graphene oxide (GO) film was prepared via a spraying method for air purification. The effects of different media, temperature and heat treatment times on the adsorption of PM 2.5 on GO film were investigated. The morphology, composition and structure of GO materials were characterized by scanning electron microscopy (SEM), electron spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR) and Raman spectroscopy. When the vacuum heat-treatment temperature is below 80 ℃ and the atmospheric heat-treatment temperature is below 100 ℃, the air purification performance of the film does not change significantly. With the increase in the vacuum heat-treatment temperature, the removal efficiency of PM 2.5 by GO film decreases gradually from 95% to 83%. At different times, the vacuum heat treatment increases with time, and the film removal rate shows a downward trend. As the heat-treatment temperature and time increase, a certain redox reaction occurs in the GO, and the air purification performance decreases. At a temperature of 120 ℃ and a time of 8 h, the removal rate drops to 81.68%. The adsorption of PM 2.5 by GO film mainly relies on the action of oxygen-containing functional groups.

Carbohydrate metabolism genes dominant in a subtropical marine mangrove ecosystem revealed by metagenomics analysis

Huaxian Zhao,Bing Yan,Shuming Mo,Shiqing Nie,Quanwen Li,Qian Ou,Bo Wu,Gonglingxia Jiang,Jinli Tang,Nan Li,Chengjian Jiang 한국미생물학회 2019 The journal of microbiology Vol.57 No.7

Mangrove sediment microorganisms play a vital role in the energy transformation and element cycling in marine wetland ecosystems. Using metagenomics analysis strategy, we compared the taxonomic structure and gene profile of the mangrove and non-mangrove sediment samples at the subtropical estuary in Beibu Gulf, South China Sea. Proteobacteria, Bacteroidetes, and Firmicutes were the most abundant bacterial phyla. Archaeal family Methanosarcinaceae and bacterial genera Vibrio and Dehalococcoides were significantly higher in the mangrove sediments than in the nonmangrove sediments. Functional analysis showed that “Carbohydrate metabolism” was the most abundant metabolic category. The feature of carbohydrate-active enzymes (CZs) was analyzed using the Carbohydrate-Active EnZymes Database. The significant differences of CZs between mangrove and non-mangrove sediments, were attributed to the amounts of polyphenol oxidase (EC 1.10.3.-), hexosyltransferase (EC 2.4.1.-), and β-N-acetylhexosaminidase (EC 3.2.1.52), which were higher in the mangrove sediment samples. Principal component analysis indicated that the microbial community and gene profile between mangrove and non-mangrove sediments were distinct. Redundancy analysis showed that total organic carbon is a significant factor that affects the microbial community and gene distribution. The results indicated that the mangrove ecosystem with massive amounts of organic carbon may promote the richness of carbohydrate metabolism genes and enhance the degradation and utilization of carbohydrates in the mangrove sediments.

Comparison of Intensities and Binary Interactions of Four Basic Tastes between an Electronic Tongue and a Human Tongue

Huaixiang Tian,Tao Feng,Zuobing Xiao,Shiqing Song,Zhiyu Li,Qiang Liu,Deshou Mao,Fenghua Li 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.5

For detection of single taste intensities and binary interactions using an electronic tongue (E-tongue) and the human tongue (H-tongue), the 4 basic flavor substances of sucrose, caffeine, citric acid, and sodium chloride were used. A linear fit was performed using response values of the E-tongue and concentrations of the basic tastes. The taste intensity of the E-tongue was positively correlated with sour and salty substances, but negatively correlated with sweet and bitter substances. All taste intensities were positively correlated with the 4 flavor substances using the H-tongue. A mathematical model of the 4 taste substances on both the E-tongue and H-tongue exhibited a semi-logarithmic form. There were synergistic, dampening, or offset effects on the taste intensity of each flavor substance in binary systems. H-tongue and E-tongue results were consistent for sweet/bitter and salt/sour interactions. H-tongue and E-tongue results were contradictory for salt/sweet and sweet/sour interactions.

Do Foreign Investors Monitor Managers in Merger and Acquisition? Evidence from China

Chao Xu,Xiaofang Zhao,Hao Yang,Shiqing Li 한국증권학회 2022 Asia-Pacific Journal of Financial Studies Vol.51 No.1

Using foreign investors’ shareholding to proxy for foreign investors’ monitoring effect in the Chinese stock market, we find that those acquirers exhibit higher announcement returns with higher shareholding, and this effect is stronger when acquirers are private firms. We provide price efficiency and corporate governance channels through which foreign investors play a monitoring role in mergers and acquisitions. Finally, foreign investors decrease the likelihood that managers will conduct mergers in the future and significantly improve long-run performance. Our study provides new insights into the real effects of foreign investors on acquisition performance and the economy.