Understanding the Increasing Hot Extremes over the Northern Extratropics Using Community Atmosphere Model

Siyu Zhao,Jiaying Zhang,Yi Deng,Na Wang 한국기상학회 2022 Asia-Pacific Journal of Atmospheric Sciences Vol.58 No.3

The past four decades have seen an increase of terrestrial hot extremes during summer in the northern extratropics, accompanied by the Northern Hemisphere (NH) sea surface temperature (SST) warming (mainly over 10°–70°N, 0°–360°) and CO2 concentration rising. This study aims to understand possible causes for the increasing hot extremes, which are defined on a daily basis. We conduct a series of numerical experiments using the Community Atmosphere Model version 5 model for two periods, 1979–1995 and 2002–2018. The experiment by changing the CO2 concentration only with the climatological SST shows less increase of hot extremes days than that observed, whereas that by changing the NH SST (over 10°–70°N, 0°–360°) with constant CO2 concentration strengthens the hot extremes change over mid-latitudes. The experiment with both SST and CO2 concentration changes shows hot extremes change closer to the observation compared to the single-change experiments, as well as more similar simulations of atmospheric circulations and feedbacks from cloud and radiative processes. Also discussed are roles of natural variability (e.g., Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation) and other factors (e.g., Arctic sea ice and tropical SST).

Transient Stability Simulation Analysis of Multi Node Power Network with Variable Speed Pumped Storage Units

Zhao Chong,Wang Longze,Ma Yiyi,Xiang Pengfei,Jiang Siyu,Chen Weidong,Zhang Yan,Li Meicheng 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

The output characteristics of variable speed pumped storage are different from conventional hydropower and constant speed pumped storage units. The continuous increase of installed capacity of variable speed pumped storage, poses a severe challenge to the safe and stable operation of the local power grid. Proposed in this paper is a kind suitable for multi-node containing variable speed pump machine storage unit electric power network transient stability method, considering the variable speed pumped storage units by the end of the instantaneous failure prone to sudden drop transient power, the power network with more nodes each busbar voltage stable operation as the goal, according to the regional power grid data under typical operation modes, Based on the power system analysis software package, an electromechanical simulation model of the 7-node power grid with variable speed pumped storage unit was established. The influence on the transient stability of a 7-node power grid is analyzed by removing variable speed pumped-storage units and three-phase short-circuit faults. The transient stability of the power grid can be maintained under the conditions of removing variable speed pumped-storage units and three-phase short-circuit faults, but some bus voltages are higher than the specified voltage upper limit. The reactive power compensation device is installed to improve the voltage stability of the power grid system, which can prevent the overvoltage accident caused by the fault of the communication system, achieve the purpose of multi-node power network stability, and improve the safety and stability of the regional power system when the fault occurs.

Antibacterial Graphene Oxide/Chitosan Composite Compression Garment Fabric

Lihuan Zhao,Siyu Zhang,Yuwen Wang,Jun Li,Yanyan Li,Yujie Yang,Silu Liu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.7

To solve issues related to hypertrophic scars, such as the risk of bacterial infections, due to the wearing ofcompression garments for extended periods of time, we prepared an antibacterial compression garment fabric (CGF) with agraphene oxide (GO)/chitosan (CS) composite. First, the GO/CS composite was prepared and used as an antibacterial agentfor antibacterial finishing of the CGF. Then, silane coupling agent γ-(methacryloxy) propyl trimethoxysilane (KH570) wasused to modify the GO/CS-finished CGF to improve the washing fastness properties of the antibacterial fabric. Finally, thedurability, physical properties, and biological safety of the antibacterial finished fabrics were studied. We found that the GO/CS composite was successfully synthesized, and the antibacterial finished fabrics were endowed with antibacterial activityagainst both gram-negative bacteria Esherichia coli (E. coli, AATCC 6538) and gram-positive bacteria Staphylococcusaureus (S. aureus, AATCC 25922), with bacteriostatic rates of 92.09 % and 99.33 %, respectively. Moreover, the durability ofthe finished fabric was effectively improved by KH570 treatment. One disadvantage was that the comfort of the antibacterialfinished fabric was affected to a certain extent; however, biological experiments showed that the CGF finished by GO/CS/KH570 showed no potential cytotoxicity on the human body and did not cause skin irritation. The prepared antibacterialfinished CGF based on the GO/CS/KH570 composite could effectively reduce the bacterial infection rates of patients wearingcompression garments, which could significantly alleviate patient suffering.

Non-isothermal Decomposition Kinetics of a New High-energy Organic Potassium Salt: K(DNDZ)

Xu, Kangzhen,Zhao, Fengqi,Song, Jirong,Ren, Xiaolei,Gao, Hongxu,Xu, Siyu,Hu, Rongzu Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

A new high-energy organic potassium salt, 2-(dinitromethylene)-1,3-diazepentane potassium salt K(DNDZ), was synthesized by reacting of 2-(dinitromethylene)-1,3-diazepentane (DNDZ) and potassium hydroxide. The thermal behavior and non-isothermal decomposition kinetics of K(DNDZ) were studied with DSC, TG/DTG methods. The kinetic equation is $\frac{d{\alpha}}{dT}$ = $\frac{10^{13.92}}{\beta}$3(1 - $\alpha$[-ln(1 - $\alpha$)]$^{\frac{2}{3}}$ exp(-1.52 ${\times}\;10^5$ / RT). The critical temperature of thermal explosion of K(DNDZ) is $208.63\;{^{\circ}C}$. The specific heat capacity of K(DNDZ) was determined with a micro-DSC method, and the molar heat capacity is 224.63 J $mol^{-1}\;K^{-1}$ at 298.15 K. Adiabatic time-to-explosion of K(DNDZ) obtained is 157.96 s.

HVOF Spray Performance Optimization Analysis and Experimental Research of WC–12Co Coating on Ti Alloy

Xinxue Chen,Chang Li,Siyu Li,Xing Han,Haisheng Jiang,Xiaoyu Zhao 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.12

TC18 titanium alloy, with low density, high strength and corrosion resistance, is a significant material for the main loadbearingcomponents of aircraft landing gear and other aviation structures. However, its corrosion resistance and wear resistanceare insufficient when it is serviced in the extreme corrosion environments such as sea salt spray and hygrothermal,which greatly affects its wide application. It is significant to design and develop high-quality anti-corrosion and wear resistantcoatings for TC18 titanium alloy. High Velocity Oxygen Fuel (HVOF) spraying WC–12Co is an ideal strengthening methodto replace surface chromium plating. Quantitatively evaluating the influence of spraying process parameters on the coatingquality is the key to prepare high-quality coatings. In this study, a numerical model of HVOF spraying WC–12Co wasestablished with JP5000 spray gun. The spray combustion reaction model and discrete phase model were solved to reveal theevolution characteristics of combustion flame flow and particle flight behavior in the spraying process. Based on the responsesurface method, the optimum spraying process parameters were determined, and the WC–12Co coatings were prepared. Onthis basis, the coating was tested by the SEM, XRD, hardness, friction and wear, salt spray corrosion and seawater corrosion. The corrosion resistance and wear resistance of the WC–12Co coating were comprehensively evaluated. The experimentshows that the WC–12Co coating prepared by HVOF spraying has great performance, which can effectively improve theprotective performance of TC18 substrate.

Sensitive Colorimetric Sensor for Lead Ions and VOCs Based on Histidine-Functionalized Polydiacetylene

Guang Yang,Ziwei Nie,Siyu Zhang,Zhaoliang Ge,Jiayin Zhao,Jiuru Zhang,Bin Li 한국고분자학회 2020 Macromolecular Research Vol.28 No.13

Due to the high toxicity of lead ions (Pb2+) and volatile organic compounds (VOCs) to human health and the environment, increasing attention has been paid by scientists to the development of simple, flexible and sensitive sensors or methods that are capable of tracing Pb2+ ions or VOCs with colorimetric visualization. In this study, the fabrication of colorimetric sensors based on histidine-functionalized diacetylene (His-DA), chromatic π-conjugated liposomes, for tracing Pb2+ ions was described. With a suitable molar ratio (4:1) between the10,12-pentacosadiynoic acid (PCDA) and His-DA monomers, the histidine units of the hybrid liposomes could rationally interrupt the efficient backbone length of polydiacetylene (PDA) chains, which causes the probe to be highly sensitive and selective for colorimetric visualization of tracing Pb2+ ions. Moreover, the His-PDA films also displayed sensitivity to volatile organic solvents or vapors, which could promote vivid color changes from blue to purple or pink. These interesting findings indicate that histidine-functionalized diacetylene may offer a promising way to design smart devices for real applications of sensing or tracing hazardous substances in the future.

Breakup dynamics and scaling laws of liquid metal droplets formed in a cross junction

Zhaomiao Liu,Chenchen Zhang,Siyu Zhao,Yan Pang,Xiang Wang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-

The formation of liquid metal droplets in a microfluidic cross junction with different viscosities of thecontinuous phase is experimentally and theoretically investigated. The flow pattern is distinguished intosqueezing and dripping by the presence of gaps. The differences in driving forces between the two patternsare analyzed theoretically and confirmed experimentally by Micro-PIV results. Roles of the squeezingforce and the shear force in droplet formation are varying due to the dynamic evolutions of the gapwidth which reduces with time. Therefore, critical values of the initial gap width are obtained which arethe outcome of the competition between neck thinning and tip growing. Compared to water–oil systems,gaps are more difficult to be formed due to the extremely high interfacial tension. Moreover, universalflow pattern maps are constructed using dimensionless parameters of Wed, Cac, and Rec, proving theimportant roles of both the squeezing force and the shear force. A scaling law of the droplet volume consideringthe influence of the viscosity ratio is proposed and a very good agreement between experimentaldata and theoretical predictions is obtained for different liquid systems.

The Preparation, Fluorescence Mechanism and Applications of High Efficiency Polymer Carbon Dots

Bai YANG,Shoujun ZHU,Siyu LU,Yubin SONG,Xiaohuan ZHAO 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Non-isothermal Decomposition Kinetics of a New High-energy Organic Potassium Salt: K(DNDZ)

Kangzhen Xu,Xiaolei Ren,Fengqi Zhao,Hongxu Gao,Siyu Xu,Rongzu Hu,Jirong Song 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10

A new high-energy organic potassium salt, 2-(dinitromethylene)-1,3-diazepentane potassium salt K(DNDZ), was synthesized by reacting of 2-(dinitromethylene)-1,3-diazepentane (DNDZ) and potassium hydroxide. The thermal behavior and non-isothermal decomposition kinetics of K(DNDZ) were studied with DSC, TG/DTG methods. The kinetic equation is d 1013.92 3(1 ) dT ααβ= −2[−ln(1 − α )]3 exp(−1.52 × 105 / RT). The critical temperature of thermal explosion of K(DNDZ) is 208.63 oC. The specific heat capacity of K(DNDZ) was determined with a micro-DSC method, and the molar heat capacity is 224.63 J mol‒1 K‒1 at 298.15 K. Adiabatic time-to-explosion of K(DNDZ) obtained is 157.96 s.

Autoregressive Model-Based Structural Damage Identification and Localization Using Convolutional Neural Networks

Qizhi Tang,Jianting Zhou,Jingzhou Xin,Siyu Zhao,Yingxin Zhou 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.7

Traditional autoregressive (AR) model-based damage identification methods construct structural damage sensitive features by trial and error, which are time-consuming, laborious and may lead to poor recognition effect. This study applies convolutional neural networks (CNNs) to quickly and automatically extract high-dimensional features of autoregressive model coefficients (ARMCs). In this research, AR model was utilized to fit the acceleration time series. The input matrices marked with damage location were produced by ARMCs, and then those matrices were sent to the proposed CNN for training. The trained CNN was employed for damage identification and localization. The effectiveness of the proposed method was verified by the damage identification and localization of a three-storied frame structure. The performance of the proposed CNN was compared with multilayer perception (MLP), random forest, and support vector machine (SVM). Meanwhile, the prediction results from different sample types were also discussed. Furthermore, parametric study in relation to the number of accelerometers and ARMCs used is conducted. These analyses demonstrate that the accuracy of CNN tests results reach 100%, 6.67%, 20%, and 25% higher than that of MLP, random forest, and SVM, respectively. Besides, other metrics calculated in this paper (e.g., precision, recall) further indicate that the proposed CNN performs well. The combination of AR and CNN does show excellent performance in damage identification and localization, which seems to be able to resist external excitation changes and accurately identify the multi-location damage and minor damage using limited accelerometers and ARMCs.