Measurement and Theoretical Calculation Confirm the Improvement of T7651 Aging State Influenced Precipitation Characteristics on Fatigue Crack Propagation Resistance in an Al–Zn–Mg–Cu Alloy

Kai Wen,Baiqing Xiong,Yongan Zhang,Zhihui Li,Xiwu Li,Lizhen Yan,Hongwei Yan,Hongwei Liu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

Precipitation characteristics influencing fatigue crack propagation contained matrix precipitate, grain boundary precipitateand precipitate free zone for Al–Zn–Mg–Cu alloys. Over-aging treatment could effectively regulate precipitation and then tobe able to change fatigue crack propagation behavior compared with the peak aging state. In the current work, typical T651and T7651 aging tempers of the alloy were extracted via hardness, electrical conductivity and mechanical properties underone-step and two-step aging treatments. Fatigue crack propagation (FCP) rate under them was tested and correspondingprecipitation characteristics and fracture morphology were observed. The results indicated that fatigue crack propagationresistance for the T7651 temper possessed an obvious improvement on the side of that for the T651 temper, which was alsosupported by fracture appearance, including tearing ridge, tearing dimple and fatigue striation. The precipitation observationshowed that the T651 alloy contained GPI zone, GPII zone and ηʹ phase while the T7651 alloy possessed ηʹ phase and η phase.Compared with the T651 temper, matrix precipitate for the T7651 temper distinctly owed an expanding of size distributionand an enlargement of average size while cuttable phase still remained the dominance for both tempers. Grain boundaryprecipitate and precipitate free zone manifested no obvious difference between the two aging tempers. Cut and bypass mechanismsof dislocation–precipitate interactions were used for explanation and it revealed the reinforced cuttable phase was infavor of enhancing fatigue crack propagation resistance. A theoretical model which directly correlated FCP rate with matrixprecipitate characteristics was employed to calculate FCP rate by substituting quantitative precipitate characteristics and thecalculation results were vaguely consistent with the experimental measurement, which proved its reliability and feasibility.

Effect of Various Retrogression Regimes on Aging Behavior and Precipitates Characterization of a High Zn-Containing Al–Zn–Mg–Cu Alloy

Kai Wen,Baiqing Xiong,Yongan Zhang,Zhihui Li,Xiwu Li,Shuhui Huang,Lizhen Yan,Hongwei Yan,Hongwei Liu 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.3

In the present work, the infl uence of various retrogression treatments on hardness, electrical conductivity and mechanicalproperties of a high Zn-containing Al–Zn–Mg–Cu alloy is investigated and several retrogression regimes subjected to a samestrength level are proposed. The precipitates are qualitatively investigated by means of transmission electron microscopy(TEM) and high-resolution transmission electron microscopy techniques. Based on the matrix precipitate observations, thedistributions of precipitate size and nearest inter-precipitate distance are extracted from bright-fi eld TEM images projectedalong ⟨110⟩ Al orientation with the aid of an imaging analysis and an arithmetic method. The results show that GP zonesand η′ precipitates are the major precipitates and the precipitate size and its distribution range continuously enlarge with theretrogression regime expands to an extent of high temperature. The nearest inter-precipitate distance ranges obtained arequite the same and the average distance of nearest inter-precipitates show a slight increase. The infl uence of precipitates onmechanical properties is discussed through the interaction relationship between precipitates and dislocations.

Renewable biomass derived hierarchically porous carbonaceous sponges and their magnetic nanocomposites for removal of organic molecules from water

Hongwei Zhou,Bo Yan,Jialiang Lai,Hanbin Liu,Aijie Ma,Weixing Chen,Xilang Jin,Weifeng Zhao,Gai Zhanga 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.58 No.-

This work describes the preparation, characterization and removal capability of a novel biomass derived carbonaceous sponges (CS) and their nanocomposites. The CS has hierarchically porous structure which is composed of lamellar structures and secondary porous structures. The pore size is on a scale from 1 nm to 200 μm. Utilizing the CS as adsorbents, rapid removal of model organic molecules, including methylene blue (MB), methyl orange (MO) and crystal violet (CV), from their aqueous solutions can be completed within 1 min with the assistance of pressure and the removal efficiency reaches up to 100%, 81% and 98%, respectively. The removal capabilities for CS towards MB, MO and CV are 0.0769 g/g, 0.2218 g/g and 1.0384 g/g, respectively and 0.0635 g/g, 0.0977 g/g and 0.8634 g/g, respectively for CS nanocomposites.

Improved mechanical properties, barrier properties and degradation behavior of poly(butylenes adipate-co-terephthalate)/poly(propylene carbonate) films

Hongwei Pan,Yanping Hao,Yan Zhao,Xianzhong Lang,Ye Zhang,Zhe Wang,Huiliang Zhang,Lisong Dong 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.5

Poly(butylene adipate-co-terephthalate) (PBAT) was blended with poly(propylene carbonate) (PPC) by a twin screw extruder and then the blends were made onto films via the blown film technique. PPC dispersed uniformly in the PBAT matrix, and the glass transition temperature (Tg) of PBAT were decreased with the increasing content of PPC. Wide angle X-ray diffraction confirmed that the crystallite dimension of PBAT was decreased after blending PBAT with the amorphous PPC. The results of mechanical tests indicated that the PBAT/PPC films showed high tensile strength and tear strength. In addition, the PBAT/PPC films showed high carbon dioxide permeability and moderate oxygen and nitrogen permeability. After embedding in soil, the weight loss and mechanical properties analysis demonstrated that the films were remarkably biodegraded. These findings contributed to application of the biodegradable materials, such as design and manufacture polymer packaging.

Activated carbon modified by Mo-doped CQDs: An efficient method to reduce the thermal hazard in toluene adsorption

Hongwei Ren,Hongyu Dong,Tengda Zhao,Zhongqing Yan,Benzhen Jia,Liang Han,Jinfeng Zhang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-

Activated carbon (AC) is one of the typical adsorbents for industrial treatment of VOCs, but AC itself has ahigh calorific value. When the heat generated by low-temperature oxidation cannot be released, it is easyto store heat and oxidize spontaneously, resulting in immeasurable harm. Therefore, it is important tostudy and improve the thermal stability of AC. In this study, Mo-doped carbon quantum dots (CQDs)was synthesized to enhance the safety of AC usage. The structure of AC before and after modificationwas characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy(FT-IR) and X-ray diffractometer (XRD). On the modified Mo-doped CQDs/AC, there are more crystallinestructures formed by Mo oxides on the surface, which makes the intermolecular force on the surface ofAC increase. At the same time, Mo oxide has strong oxidation resistance, which can inhibit the thermaldecomposition process of AC, and has stronger stability. The spontaneous combustion tendency and thermalhazard of AC before and after modification were greatly improved. The heat released in the tolueneadsorption by the modified AC at different temperatures was significantly lower than the heat released bythe unmodified AC. According to the Langmuir adsorption isotherm, the adsorption performance of ModopedCQDs (2.5 wt%) was 1.6 times higher than that of AC when the system was 25 C. The resultsshowed that Na2MoO4 CQDs modified AC could effectively improve the thermal stability and greatlyreduce the spontaneous combustion tendency. A relative fire safety performance evaluation model wasalso established to comprehensively evaluate the fire risk of VOCs treatment by AC.

IOMMU Para-Virtualization for Efficient and Secure DMA in Virtual Machines

( Hongwei Tang ),( Qiang Li ),( Shengzhong Feng ),( Xiaofang Zhao ),( Yan Jin ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

VirtAV: an Agentless Runtime Antivirus System for Virtual Machines

( Hongwei Tang ),( Shengzhong Feng ),( Xiaofang Zhao ),( Yan Jin ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.11

Antivirus is an important issue to the security of virtual machine (VM). According to where the antivirus system resides, the existing approaches can be categorized into three classes: internal approach, external approach and hybrid approach. However, for the internal approach, it is susceptible to attacks and may cause antivirus storm and rollback vulnerability problems. On the other hand, for the external approach, the antivirus systems built upon virtual machine introspection (VMI) technology cannot find and prohibit viruses promptly. Although the hybrid approach performs virus scanning out of the virtual machine, it is still vulnerable to attacks since it completely depends on the agent and hooks to deliver events in the guest operating system. To solve the aforementioned problems, based on in-memory signature scanning, we propose an agentless runtime antivirus system VirtAV, which scans each piece of binary codes to execute in guest VMs on the VMM side to detect and prevent viruses. As an external approach, VirtAV does not rely on any hooks or agents in the guest OS, and exposes no attack surface to the outside world, so it guarantees the security of itself to the greatest extent. In addition, it solves the antivirus storm problem and the rollback vulnerability problem in virtualization environment. We implemented a prototype based on Qemu/KVM hypervisor and ClamAV antivirus engine. Experimental results demonstrate that VirtAV is able to detect both user-level and kernel-level virus programs inside Windows and Linux guest, no matter whether they are packed or not. From the performance aspect, the overhead of VirtAV on guest performance is acceptable. Especially, VirtAV has little impact on the performance of common desktop applications, such as video playing, web browsing and Microsoft Office series.

IOMMU Para-Virtualization for Efficient and Secure DMA in Virtual Machines

Tang, Hongwei,Li, Qiang,Feng, Shengzhong,Zhao, Xiaofang,Jin, Yan Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

Transcriptomic analyses reveal novel genes with sexually dimorphic expression in Takifugu rubripes brain during gonadal sex differentiation

Xufang Shen,Hongwei Yan,Lei Zhang,Zhen Yuan,Wenlei Liu,Yumeng Wu,Qi Liu,Xiaoyi Luo,Ying Liu 한국유전학회 2020 Genes & Genomics Vol.42 No.4

Background Quantification of mRNAs in gonads and other tissues at the early critical development stage of sex differentiation may help to provide a global view of regulatory mechanisms underlying sex differentiation. We have recently reported the transcriptomic profiling of fugu gonad associated with sex differentiation. Objectives This study attempted to identify the genes in the brain that are involved in gonadal differentiation and development. Methods In this study, a transcriptomic scan of potential candidate genes involved in sex differentiation was conducted in the brains of fugu larvae at 30 and 40 dah (morphological gonadal sex differentiation had not yet occurred). The dimorphic expression patterns of several candidate genes were verified using quantitative PCR. Results A total of 28.24 Gb of clean reads were obtained and 22,337 genes were identified in the brains of fugu larvae. These included 1008 novel genes that provide abundant data for functional analysis of sex differentiation. 229 genes were identified in the 30 dah larvae that were abundant in the XY brain and 21 that were abundant in the XX brain. In the 40 dah larvae, 325 genes were identified abundant in the XY brain and 174 were identified abundant in the XX brain. Conclusion This is the first investigation into the transcriptome of the fugu larvae brain at the early sex differentiation stage. The results obtained here will enhance the understanding of molecular mechanisms that underly fugu sex differentiation.

The Influence of Epoxy Functionalized Acrylate Particles on the Properties of Plasticized PLA Blown Films

Ye Zhang,Yan Zhao,Hongwei Pan,Xianzhong Lang,Huili Yang,Huiliang Zhang,Huixuan Zhang,Lisong Dong 한국고분자학회 2016 폴리머 Vol.40 No.3

Polylactide (PLA) was plasticized with poly(diethylene glycol adipate) (PDEGA). The plasticized PLA was further blended with core-shell structured particles of glycidyl methacrylate-functionalized methyl methacrylate-butyl acrylate copolymer (GACR) using a twin-screw extruder, and the extruded samples were blown using the blown thin film technique. Both PDEGA and GACR significantly influenced the physical properties of the films. Compared to neat PLA, the elongation at break and tear strength of the films were significantly improved. The shear yielding induced by cavitation of GACR particles was the major tearing mechanism. GACR could act as a tear resistance modifier for PLA blown films. The spherulite size of the PLA/PDEGA/GACR films decreased with the addition of GACR. The biodegradability of the PLA/PDEGA/GACR films decreased slightly. These findings contributed new knowledge to the additive area and gave important implications for designing and manufacturing polymer packaging materials.