Mechanical Properties of Styrene-Butadiene Rubber Reinforced with Silica by in situ Tetraethoxysilane Hydrolysis over Acid Catalyst

( Qingyuan Li ),( Xiangxu Li ),( Ur Ryong Cho ) 한국고무학회 2018 엘라스토머 및 콤포지트 Vol.53 No.2

Styrene-butadiene rubber (SBR), reinforced with different contents of silica (with or without modification using silane coupling agents), was prepared by a modified sol-gel method involving hydrolyzation of tetraethoxysilane over an acid catalyst. The structures of the as-prepared samples were characterized using various techniques, such as scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The mechanical properties of the as-prepared samples were discussed in detail. The results revealed an increasing of the storage modulus (G’) with increase in the silica content without modification. In contrast, G’ decreased after modification using silane coupling agents, indicating a reduction in the silica-silica interaction and improved dispersion of silica in the SBR matrix. Both tensile stress and hardness increased with increase in the silica content (with modification) in the SBR matrix, albeit with low values compared to the samples with un-modified silica, except for the case of silica modified using (3-glycidyloxypropyl) trimethoxysilane (GPTS). The latter observation can be attributed to the special structure of GPTS and the effort of oxygen atom lone-pair.

Silica-Starch Reinforced Styrene-Butadiene Rubber Composites

Qingyuan Li,Xiangxu Li,Sun-Ho Jang(장선호),Dam-Hee Lee(이담희),Yuan Fan,Ur Ryong Cho(조을룡) 한국고분자학회 2017 폴리머 Vol.41 No.6

Silica-starch-reinforced styrene-butadiene rubber (SBR) was prepared by a modified sol-gel method of mixing the silica sol, the starch paste, and then in situ blending the SBR latex. The fracture surface of the samples after the tensile test was characterized by FE-SEM. The tensile strength, the storage modulus, the hardness and the swelling test of the vulcanized samples were systematically discussed. The results showed the elongation at break, the hardness and the storage modulus increased with the increasing of silica in the as-prepared samples. The swelling ratio decreased with increase in the content of silica, indicative of the excellent crosslink density in the silica-starch-reinforced SBR.

Anatomical Study of the Accessory Tendon of the Extensor Hallucis Longus Muscle and Its Clinical Application

Yue Li,Jing-Ying Zhang,Xin-Yue Zhao,Li-Ya Pan,De-Hao Jin,He-Xing Xu,Hu-Zhe Cui,Yan-Qun Liu,Xiang-Zheng Qin,Qingyuan Li 대한정형외과학회 2021 Clinics in Orthopedic Surgery Vol.13 No.2

Background: The accessory tendon of the extensor hallucis longus (ATEHL) muscle is a common abnormal structure, and its clinical significance remains debatable. In this study, we provide the incidence of the ATEHL and characterize its morphological types in Asian cadavers and investigate its clinical applications. Methods: The tendons from 50 adult cadaveric feet, fixed in 10% formalin, were analyzed. We measured the length and width of both the ATEHL and the extensor hallucis brevis (EHB). Results: All dissected specimens had an ATEHL. The first metatarsophalangeal joint was surrounded by an accessory tendon that inserted onto the joint capsule and the dorsal base of the proximal phalanx. We classified the ATEHL into 3 types based on their directions. Differences in ATEHL type based on sex were not statistically significant. Conclusions: We found an ATEHL in all cadaveric specimens in this study. We surmise that the ATEHL acts as an antagonist with the EHB when the toe is extending, which might help prevent the occurrence of hallux valgus deformity.

Recovery of mortar-aggregate interface of fire-damaged concrete after post-fire curing

Lang Li,Hong Zhang,Jiangfeng Dong,Hongen Zhang,Pu Jia,Qingyuan Wang,Yongjie Liu 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.3

In order to investigate the strength recovery of fire-damaged concrete after post-fire curing, concrete specimens were heating at 2°C/min or 5°C/min to 400, 600 and 800°C, and these exposed specimens were soaked in the water for 24 hours and following by 29-day post-fire curing. The compressive strength and split tensile strength of the high-temperature-exposed specimens before and after post-fire curing were tested. The proportion of split aggregate in the split surfaces was analyzed to evaluate the mortar-aggregate interfacial strength. After the post-fire curing process, the split tensile strength of specimens exposed to all temperatures was recovered significantly, while the recovery of compressive strength was only obvious within the specimens exposed to 600°C. The tensile strength is more sensitive to the mortar-aggregate interfacial cracks, which caused that the split tensile strength decreased more after high-temperature exposure and recovery more after post-fire curing than the compressive strength. The mortar-aggregate interfacial strength also showed remarkable recovery after post-fire curing, and it contributed to the recovery of split tensile strength.

Synthesis and Photocatalytic Properties of SnSe2/Se Heterojunction Films

Jing Li,Hongxiao Zhao,Yan Lei,Qingyuan Yang,Zhi Zheng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.4

SnSe2/Se heterojunction films were successfully grown on fluorine-doped tin oxide (FTO) glass for the first time via a one-step solvothermal route using magnetron sputtered Sn metallic precursors, Se powders as selenium source, cyclohexanol as solvent and cyclohexanol as auxiliary solvent, respectively. The SnSe2/Se heterojunction films consisted of Se nanoparticles or nanorods cluster and SnSe2 network surface layers. The crystalline phase and morphology of SnSe2/Se films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), respectively. The photocatalysis measurements of the products for rhodamine Blue (RhB) demonstrated that SnSe2/Se heterojunction films revealed better dye degradation properties than SnSe2 nanosheet films due to the higher separation rates of photogenerated electron–hole pairs of SnSe2/Se heterojunction films, which can be confirmed by surface transient photovoltage (TPV) analyzer.

Correlation between in vitro fertilization and artificial insemination in Holstein bulls

Sun Wei,Li Yunxia,Su Jie,Bao Xiangnan,Ding Rui,Zhao Gaoping,Cao Guifang,Hu Shuxiang,Wang Jianguo,Sun Qingyuan,Yu Haiquan,Li Xihe 아세아·태평양축산학회 2021 Animal Bioscience Vol.34 No.12

Objective: Owing to the lack of a breeding index for efficient and quick fertility evaluations of Holstein bulls when using traditional or genome-wide detection methods, this study aimed to determine whether in vitro fertilization (IVF) could be used as an indicator of conception rate of artificial insemination (AI).Methods: Conventional and sexed frozen semen from nine bulls were used for IVF and AI.Results: The IVF and AI conception rates of each bull were confirmed to be positively correlated between the conventional frozen and sexed frozen semen. The correlation coefficient R values of nine bulls between IVF and AI methods were 0.73 and 0.97 for the conventional frozen and sexed frozen semen, respectively. The average conception rate of three bulls undergoing AI was 69.5% and 64.2%, 61.8% and 58.8%, and 48.2% and 46.2% in first-, second-, and third-born cows when conventional frozen and sexed frozen semen were used, respectively, which showed a positive correlation with the fertilization rate in the same parity. We propose an evaluation standard to assess the fertilization ability of bulls based on their IVF test results, which is categorized into three grades: grade one, normal fertility bull with an AI conception rate of 40%±5% and IVF rate of 45% to 60%; grade two, higher fertility bull with an AI conception rate of 50%±5% and IVF rate of 61% to 80%; and grade three, highest fertility bull with an AI conception rate of 60%±5% and IVF rate of >80%.Conclusion: These findings reveal that IVF results can be used as a breeding index for bulls to evaluate their AI conception ability, which may shorten the time required to select bulls for breeding. Objective: Owing to the lack of a breeding index for efficient and quick fertility evaluations of Holstein bulls when using traditional or genome-wide detection methods, this study aimed to determine whether in vitro fertilization (IVF) could be used as an indicator of conception rate of artificial insemination (AI). Methods: Conventional and sexed frozen semen from nine bulls were used for IVF and AI. Results: The IVF and AI conception rates of each bull were confirmed to be positively correlated between the conventional frozen and sexed frozen semen. The correlation coefficient R values of nine bulls between IVF and AI methods were 0.73 and 0.97 for the conventional frozen and sexed frozen semen, respectively. The average conception rate of three bulls undergoing AI was 69.5% and 64.2%, 61.8% and 58.8%, and 48.2% and 46.2% in first-, second-, and third-born cows when conventional frozen and sexed frozen semen were used, respectively, which showed a positive correlation with the fertilization rate in the same parity. We propose an evaluation standard to assess the fertilization ability of bulls based on their IVF test results, which is categorized into three grades: grade one, normal fertility bull with an AI conception rate of 40%±5% and IVF rate of 45% to 60%; grade two, higher fertility bull with an AI conception rate of 50%±5% and IVF rate of 61% to 80%; and grade three, highest fertility bull with an AI conception rate of 60%±5% and IVF rate of >80%. Conclusion: These findings reveal that IVF results can be used as a breeding index for bulls to evaluate their AI conception ability, which may shorten the time required to select bulls for breeding.

Comparative study on carboxylated styrene butadiene rubber composites reinforced by hybrid fillers of rice bran carbon and graphite carbon

Yuan Fan,Qingyuan Li,Xiangxu Li,Dam hee Lee,Ur Ryong Cho 한국탄소학회 2018 Carbon Letters Vol.27 No.-

In the present work, a comparative study of the mechanical behavior of two series of elastomeric composites, based on carboxylated styrene butadiene rubber (X-SBR) and reinforced with rice bran carbon (RBC) and graphite, is reported. Hybrid composites of X-SBR filled with RBC-graphite were also investigated in terms of the cure characteristics, hardness, tensile properties, abrasion resistance, and swelling. It was observed that the cure times decreased with the incorporation of a carbon filler whereas the torque difference, tensile strength, tensile modulus, hardness, and swelling resistance increased compared to the neat X-SBR revealing a favorable characteristic of crosslinking. Dynamic rheological analysis showed that the G values of the composites, upon the addition of RBC-graphite, were changed to some extent. This demonstrates that the presence of a strongly developed network of fillers will ensure a reinforcing characteristic in a polymer matrix.

The Risk Factors and Outcomes for Radiological Abnormalities in Early Convalescence of COVID-19 Patients Caused by the SARS-CoV-2 Omicron Variant: A Retrospective, Multicenter Follow-up Study

Wang Hong,Yang Qingyuan,Li Fangfei,Wang Huiying,Yu Jing,Ge Xihong,Gao Guangfeng,Xia Shuang,Xing Zhiheng,Shen Wen 대한의학회 2023 Journal of Korean medical science Vol.38 No.8

Background: The emergence of the severe acute respiratory syndrome coronavirus 2 omicron variant has been triggering the new wave of coronavirus disease 2019 (COVID-19) globally. However, the risk factors and outcomes for radiological abnormalities in the early convalescent stage (1 month after diagnosis) of omicron infected patients are still unknown. Methods: Patients were retrospectively enrolled if they were admitted to the hospital due to COVID-19. The chest computed tomography (CT) images and clinical data obtained at baseline (at the time of the first CT image that showed abnormalities after diagnosis) and 1 month after diagnosis were longitudinally analyzed. Uni-/multi-variable logistic regression tests were performed to explore independent risk factors for radiological abnormalities at baseline and residual pulmonary abnormalities after 1 month. Results: We assessed 316 COVID-19 patients, including 47% with radiological abnormalities at baseline and 23% with residual pulmonary abnormalities at 1-month follow-up. In a multivariate regression analysis, age ≥ 50 years, body mass index ≥ 23.87, days after vaccination ≥ 81 days, lymphocyte count ≤ 1.21 × 10-9/L, interleukin-6 (IL-6) ≥ 10.05 pg/mL and IgG ≤ 14.140 S/CO were independent risk factors for CT abnormalities at baseline. The age ≥ 47 years, presence of interlobular septal thickening and IL-6 ≥ 5.85 pg/mL were the independent risk factors for residual pulmonary abnormalities at 1-month follow-up. For residual abnormalities group, the patients with less consolidations and more parenchymal bands at baseline could progress on CT score after 1 month. There were no significant changes in the number of involved lung lobes and total CT score during the early convalescent stage. Conclusion: The higher IL-6 level was a common independent risk factor for CT abnormalities at baseline and residual pulmonary abnormalities at 1-month follow-up. There were no obvious radiographic changes during the early convalescent stage in patients with residual pulmonary abnormalities.

Investigating Various Factors Affecting the Long-Term Compressive Strength of Heat-Cured Fly Ash Geopolymer Concrete and the Use of Orthogonal Experimental Design Method

Hongen Zhang,Lang Li,Prabir Kumar Sarker,Tao Long,Xiaoshuang Shi,Qingyuan Wang,Gaochuang Cai 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.1

This work quantified the hierarchy of the influence of three common mixture design parameters on the compressive strength and the rate of strength increase over the long term of low-calcium fly ash geopolymer concrete (FAGC) through designing 16 mixtures by the orthogonal experimental design (OED) method. The parameters used in the study were liquid to fly ash (L/FA) ratio, sodium hydroxide concentration (SHC) and sodium silicate solution to sodium hydroxide solution (SS/SH) ratio. The L/FA ratio showed little effect on compressive strength when it was varied from 0.40 to 0.52. SHC showed the greatest influence on compressive strength with little impact on the rate of strength increase after the initial heat curing. Even though the SS/SH ratio showed a small effect on the initial compressive strength, it had a considerable influence on the rate of strength increase over the long term. It was found that the compressive strength at 480 days was positively related to the Na₂O/SiO₂ molar ratio when it was varied from 0.49 to 0.80 and the Si/Al molar ratio was increased up to 1.87. Analysis of the failure types of specimens demonstrated that compressive strength of FAGC was associated with the strength of the mortar–aggregate interface zone (MAIZ).

The Natural History of Kienböck’s Disease Diagnosed at More than 50 Years of Age

Ji Sup Hwang,Bum Jin Shim,Qingyuan Li,Jihyeung Kim,Goo Hyun Baek 대한정형외과학회 2022 Clinics in Orthopedic Surgery Vol.14 No.3

Background: Previous literatures suggest that the prognosis of Kienböck’s disease might be favorable despite no surgery if it is diagnosed in late age, but the evidence is not clear. The aim of this study was to determine the radiographic and clinical progression of Kienböck’s disease diagnosed at more than 50 years of age. Methods: Data of 27 patients diagnosed with Kienböck’s disease at more than 50 years of age between 2000 and 2016 were investigated. During the study period, no treatment, either surgical or nonsurgical, was applied. We explained to the patients that the affected lunate was not expected to collapse further if found late in age. Annual visits were recommended, through which radiographic and clinical observation was made. We assessed changes in Stahl index and radioscaphoid angle between the initial assessment and the final follow-up, and clinical assessment was made using pain in visual analog scale (VAS) and Dornan’s criteria. Results: Initially, 2 patients were in Lichtman stage 1, 6 in stage 2, 5 in stage 3A, 11 in stage 3B, and 3 in stage 4. Radiographic follow-up of at least 5 years (mean, 7.8 years) was made in 14 patients, whose Stahl index and radioscaphoid angle did not differ significantly from their initial measurements. Arthritic appearance was not found, and progression in the Lichtman stage was detected in 1 lunate, from 3A to 3B. Despite no surgical treatment for an average of 7.5 years (range, 5.0–15.7 years) of observation period in the 27 patients, average pain in VAS improved from 3.5 (range, 1–7) to 0.8 (range, 0–2), with excellent or good clinical status by Dornan’s criteria. Conclusions: Our study suggests that Kienböck’s disease diagnosed at more than 50 years of age can follow a benign natural course in radiographic and clinical aspects. Therefore, surgical interventions should be considered carefully in this age group.