Manufacturing of 3D Microlens Array Mold on Bulk Metallic Glass by Self-Aligned Multi-Ball Hot Embossing

Xiaohua Liu,Ruodong Mo,Kangsen Li,Jun She,Jiang Ma,Feng Gong 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.4

Bulk metallic glasses (amorphous alloys) exhibiting both high hardness and extraordinary thermoplastic forming ability, are perfect mold material for 3D optical microlens array. However, conventional 3D micro fabrication for metallic glass requires Si templates which are extremely costly and eco-unfriendly to machine and demold. In this study, we report a green and lowcost self-aligned multi-ball hot embossing process to create 3D micro dimple array on metallic glass by replicating spherical crowns of self-aligned precision balls. A 3D metallic glass micro dimple array with aperture of 867.2 μm and surface roughness of 8.2 nm was fabricated in 30 s. Different from conventional hot embossing that material full-filled into mold, the new process enables micro dimple fabrication with different specifications by freely controlling the down displacement of balls. Therefore, the relationship between down displacement and depth of micro dimple was revealed through exploring the material flow behavior by a verified FE model. In addition, to test the feasibility of the fabricated metallic glass mold, a PMMA compound eye structure was embossed and its focusing and imaging performance were subsequently evaluated. This research demonstrates a new manufacturing process for rapid fabrication of 3D microlens arrays metallic glass mold in a neat and economic way.

Anti-inflammatory and Anti-nociceptive Activities of Compounds from Tinospora sagittata (Oliv.) Gagnep.

Xiaohua Liu,Zhenlin Hu,Qirong Shi,Huawu Zeng,Yunheng Shen,Huizi Jin,Wei-Dong Zhang 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.7

Radix Tinosporae is a herb widely used in traditional Chinese medicine for the treatment of various inflammatory diseases. In the present study, its anti-inflammatory and antinociceptive activities were investigated. The ethanol extract of Radix Tinosporae exhibited significant inhibitory effects on xylene-induced ear edema and acetic acid-induced writhing in mice. Using bioassay-guided fractionation, the n-butanol fraction was determined as the active fraction. Further purification of the most active n-butanol fraction led to the isolation of three compounds, palmatine, columbamine and columbinyl glucoside. All three compounds showed inhibitory activities on xylene-induced ear edema, but only palmatine and columbamine exhibited significant inhibitory effects on acetic acid-induced writhing. In addition, palmatine and columbamine markedly inhibited in vitro production of nitric oxide and nuclear factor-κB activation in RAW264.7 macrophage cells in response to lipopolysaccharide or tumor necrosis factor α stimulation. These results provide justification for the utilization of Radix Tinosporae in Chinese folk medicine for the treatment of inflammatory diseases.

The ROP mechanism study in hard formation drilling using local impact method

Liu, Weiji,Zhu, Xiaohua,Zhou, Yunlai,Mei, Liu,Meng, Xiannan,Jiang, Cheng Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.1

The low rate of penetration and short lifetime of drilling bit served as the most common problems encountered in hard formation drilling, thus leading to severe restriction of drilling efficiency in oil and gas reservoir. This study developed a new local impact drilling method to enhance hard formation drilling efficiency. The limitation length formulas of radial/lateral cracks under static indentation and dynamic impact are derived based on the experimental research of Marshall D.B considering the mud column pressure and confining pressure. The local impact rock breaking simulation model is conducted to investigate its ROP raising effect. The results demonstrate that the length of radial/lateral cracks will increase as the decrease of mud pressure and confining pressure, and the local impact can result in a damage zone round the impact crater which helps the rock cutting, thus leading to the ROP increase. The numerical results also demonstrate the advantages of local impact method for raising ROP and the vibration reduction of bit in hard formation drilling. This study has shown that the local impact method can help raising the ROP and vibration reduction of bit, and it may be applied in drilling engineering.

Numerical modelling of bottom-hole rock in underbalanced drilling using thermo-poroelastoplasticity model

Weiji Liu,Yun-Lai Zhou,Xiaohua Zhu,Xiannan Meng,Mei Liu,Magd Abdel Wahab 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.5

Stress analysis of bottom-hole rock has to be considered with much care to further understand rock fragmentation mechanism and high penetration rate. This original study establishes a fully coupled simulation model and explores the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on the stress distribution in bottom-hole rock. The research finds that in air drilling, as the well depth increases, the more easily the bottom-hole rock is to be broken. Moreover, the mud pressure has a great effect on the bottom-hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock is. Furthermore, the maximum principal stress of the bottom-hole increases as the mud pressure, well depth and temperature difference increase. The bottom-hole rock can be divided into three main regions according to the stress state, namely a) three directions tensile area, b) two directions compression areas and c) three directions compression area, which are classified as a) easy, b) normal and c) hard, respectively, for the corresponding fragmentation degree of difficulty. The main contribution of this paper is that it presents for the first time a thorough study of the effect of related factors, including stress distribution and temperature, on the bottom-hole rock fracture rather than the well wall, using a thermo-poroelastoplasticity model.

The ROP mechanism study in hard formation drilling using local impact method

Weiji Liu,Xiaohua Zhu,Yun-Lai Zhou,Liu Mei,Xiannan Meng,Cheng Jiang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.1

The low rate of penetration and short lifetime of drilling bit served as the most common problems encountered in hard formation drilling, thus leading to severe restriction of drilling efficiency in oil and gas reservoir. This study developed a new local impact drilling method to enhance hard formation drilling efficiency. The limitation length formulas of radial/lateral cracks under static indentation and dynamic impact are derived based on the experimental research of Marshall D.B considering the mud column pressure and confining pressure. The local impact rock breaking simulation model is conducted to investigate its ROP raising effect. The results demonstrate that the length of radial/lateral cracks will increase as the decrease of mud pressure and confining pressure, and the local impact can result in a damage zone round the impact crater which helps the rock cutting, thus leading to the ROP increase. The numerical results also demonstrate the advantages of local impact method for raising ROP and the vibration reduction of bit in hard formation drilling. This study has shown that the local impact method can help raising the ROP and vibration reduction of bit, and it may be applied in drilling engineering.

Determining a Key Service Area of Feeder Buses for Rail Transit Station Based on Potential Railway Demand

Xiaohua Yu,Yaru Bi,Peng Chen,Xinping Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

As the size of the city expands, longer journeys often involve the use of two or more modes of transportation. Feeder buses perform as a feeder mode of rail transit, its feeder areas are the key factor to improve this bus-rail transit mode service quality. Feeder areas that are either too small or too large can hinder the effectiveness of feeder buses. This paper presents a method to determine a suitable range as the key service of feeder buses for rail transit stations. The modal of accessibility consistency threshold interface of bus and bus-rail transit mode features is established, and the competition area of adjacent stations is considered to calculate the reasonable bus feeder range of rail transit stations. Based on the analysis of the demand characteristics of the feeder passengers, the potential passengers of the bus-rail transit travel mode are defined as the travel where only one endpoint of the starting and ending is within the walking range of the rail transit station, and a method for identifying the points of interest of potential passengers of the bus-rail transit mode is proposed. The potential passenger flow within the reasonable feeder range of rail transit stations is visualized, and the key service areas of feeder buses are determined based on the maximum potential passengers. Taking Jinan Metro Line NO.2 Stations as an example, combined with the station type, the key service area of feeder buses for railway stations is explained.

The Potentials in Solar Cells for MEH-PPV Derivatives: Molecular Design and Performance Prediction

Xiaohua Xie,Xu Liu,Dan Zeng,Longfeng Zhao 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.7

In this contribution, the polymer poly(2-methoxy-5(2?-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) is researched at the aspect of electronic and structural properties to locate the relationships between structures and the experimental properties by employing DFT and TD-DFT method. The studied properties refer to the geometry features, absorption spectra, frontier molecular orbital properties, hole transport properties, and exciton dissociation ability at polymer/PC61BM interface. In addition, four MEH-PPV derivatives, MEH-PPV substituted with F atoms, are designed and studied through comparing with the properties of MEH-PPV. The results indicate that MEH-PPV has low HOMO levels and large hole transport property, which result in its preferable performance. Besides, the designed polymers are promising candidates as PSC donors due to better exciton dissociation ability and larger theoretical VOC owing to lower highest occupied molecule levels, in special, MEH-PPV-Fc has better hole transport properties than MEH-PPV due to smaller m*.

Synthesis and Properties of High Thermally Stable and Organosoluble Poly(pyridine imide)s with Pendent Diethylaminophenyl Groups

Xiaohua Huang,Hua Li,Chanjuan Liu,Limin Zang,Huanfu Zhou,Chun Wei 한국섬유공학회 2019 Fibers and polymers Vol.20 No.6

A novel diamine monomer 4-(4-diethylaminophenyl)-2,6-bis(4-aminophenyl)pyridine (APAP) was successfullysynthesized, and then a series of poly(pyridine imide)s was prepared from APAP with five commercial dianhydrides:pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride(ODPA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′-(hexafluoroisopropylidene)diphthalicanhydride (6FDA) via a two-step solution polycondensation method. The structure of APAP was characterized by FT-IR,NMR, and MS. The resulting polymers have good solubility in polar solvents, such as NMP, DMF, and DMSO. Furthermore,they exhibited outstanding thermal stability. The glass transition temperature (Tg) of polymers range from 326 to 346 oC, andthe temperature at 5 % and 10 % weight loss in the range of 527 oC to 570 oC and 550 oC to 601 oC, respectively. Moreover,they also presented excellent hydrophobicity with contact angels in the range of 88.4 o to 94.0 o.

The Investigation of Rock Indentation Simulation Based on Discrete Element Method

Xiaohua Zhu,Weiji Liu,Xianqun He 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

Rock indentation is widely encountered in rock engineering, such as oil & gas drilling process. The rock indentation represents the fundamental process for mechanical rock breaking. Therefore, it is necessary to research the failure mechanism during the rock indentation process. For this purpose, the Uniaxial Compressive Strength (UCS) and Brazilian Tensile Strength (BTS) tests are performed to calibrate the relations between micro-properties and macro-properties of the rock specimens. The rock indentation process and crack propagation with the effects of lateral pressure, hydraulic pressure, ledge, wedge angle and joint are researched by PFC2D in this paper. The results show that: with the indenter penetrating into rock, the sub-vertical crack is formed from the damaged zone and it will extend to bottom edge of the rock at last; the initiation and propagation of the sub-vertical crack is mostly driven by the tensile contact force. The development of sub-vertical crack and damaged zone are restrained with increasing lateral pressure, the lateral pressure increases led to an increase in the critical penetration depth and the size of the damaged zone decreases and its shape flattens with the lateral pressure increasing. On the contrary, the development of sub-vertical crack and damaged zone are promoted with increasing hydraulic pressure. With the wedge angle increases the size of crushed zone underneath the indenter increases, it promotes the formation of sub-vertical crack; larger wedge angle causes a larger indentation force. The existence of a ledge leads to crack initiation and propagation towards the free surface and the presence of the joint also promotes crack initiation and propagation towards the joint; when the crack propagates to the joint, the crack will no longer propagate towards the intact rock mass but along the joint.

Simultaneous Electrochemical Determination of Hydroquinone, Catechol and Resorcinol at Nitrogen Doped Porous Carbon Nanopolyhedrons-multiwall Carbon Nanotubes Hybrid Materials Modified Glassy Carbon Electrode

Liu, Wei,Wu, Liang,Zhang, Xiaohua,Chen, Jinhua Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.1

The nitrogen doped porous carbon nanopolyhedrons (N-PCNPs)-multi-walled carbon nanotubes (MWCNTs) hybrid materials were prepared for the first time. Combining the excellent catalytic activities, good electrical conductivities and high surface areas of N-PCNPs and MWCNTs, the simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RE) with good analytical performance was achieved at the N-PCNPs-MWCNTs modified electrode. The linear response ranges for HQ, CC and RE are 0.2-455 ${\mu}M$, 0.7-440 ${\mu}M$ and 3.0-365 ${\mu}M$, respectively, and the detection limits (S/N = 3) are $0.03{\mu}M$, $0.11{\mu}M$ and $0.38{\mu}M$, respectively. These results are much better than that obtained on some graphene or CNTs-based materials modified electrodes. Furthermore, the developed sensor was successfully applied to simultaneously detect HQ, CC and RE in the local river water samples.