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Rui Yong,Xi Fu,Man Huang,Qifeng Liang,Shi-Gui Du 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.1
An accurate measurement of the Joint Roughness Coefficient (JRC) of large rock joints is essential for understanding the mechanical behavior and permeability characteristics of rock mass. Determining the surface roughness of rock joints in situ, however, is timeconsuming and depends on sophisticated instruments. This study was carried out to develop a systematic method of measuring the JRC values of large joint roughness profiles. The roughness profiles were accurately recorded by a hand profilograph in the field and then digitized with flexibly adjusted sampling intervals by the grayscale image processing method. The digitized profiles were correlated closely with the original roughness profiles. A computerized approach for JRC quantitative evaluation was proposed based on the roughness amplitude/joint length relationship with JRC. The interval effect analysis showed that this method was effective for estimating the JRC values of different sized rock joints. This JRC measurement method has been successfully used in a case study of killas rock joints in Changshan City, P.R. China.
The Focused Electrode Ring for Electrohydrodynamic Jet and Printing on Insulated Substrate
Zeshan Abbas,Dazhi Wang,Liangkun Lu,Zhaoliang Du,Xiangyu Zhao,Kuipeng Zhao,Meng Si,Penghe Yin,Xi Zhang,Yan Cui,Junsheng Liang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.5
Drop-on-demand electrohydrodynamic jet (DoD E-Jet) printing is considered a well-known type of fabrication method contemporary since it can be used to print high-resolution microstructures (< 1 μm) on various insulating substrates. This paper presents a numerical study of DoD E-Jet printing using a novel combination of needle and focused electrode ring to print stable and consistent microdroplets on a Polyethylene terephthalate substrate. Primarily, a phase field method was used to generate a stable cone-jet morphology that can allow the production of high-resolution micron/nano structures on PET substrates. The numerical simulation of cone-jet morphology was performed by COMSOL multiphysics software. Further, the impact of key parameters such as flow rate and dc positive pulse voltage was studied on cone-jet morphology through numerical simulation. Subsequently, optimized operating parameters i.e., f = 5.3 . 10 –15 m 3 s −1 , V n = 1.9 kV and V r = 0.7 kV were achieved by performing a series of numerical experiments. Then, optimized parameters by simulation were directly used to print arrays of stable droplets on PET substrate using the focused electrode ring in different locations by regulating distance 0.2 mm to 1.3 mm between needles to focused electrode ring. The minimum size of stable microdrop was measured 3 μm on PET substrate (thickness = 0.2 mm) using a 50 μm size quartz capillary maintaining a distance of 0.2 mm between combined needle and focused electrode ring. The experimental results proved that the simulation model is useful for printing different microstructures on insulating substrates and creating a promising production path for micro-electro mechanical system and nano-electro mechanical system (MEMS and NEMS).