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Alexis Johnney Mertens,Selvaraj Senthilvelan 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.2
In the recent years, utilization of non-standard gears have increased due to the improved load carrying capacity and improved durability. However, these non standard gears are manufactured by non-conventional manufacturing process including wire cut electric discharging machining (WEDM). Standard gears are manufactured by conventional machining process, hobbing. This work reported the performance of injection molded polymer gear paired with a steel gear manufactured by conventional hobbing and wire cut electric discharge machining process. WEDM steel gear surface exhibited poor surface topology and higher hardness when compared to that of conventional machined steel gear. Measured net surface temperature of polymer gear at various loads (2-3 Nm) confirmed a temperature rise of 10-15°C when paired with WEDM gear compared to that of hobbed and ground gear. Polymer gear paired with WEDM exhibited inferior fatigue performance when compared to the polymer gear paired with hobbed and ground gear.
Kim, Hyoungsoo,Belmiloud, Naser,Mertens, Paul W. The Korean Society of Visualization 2016 한국가시화정보학회지 Vol.14 No.2
We investigate an internal flow pattern of an evaporating droplet where the contact line non-uniformly recedes. By using tomographic Particle Image Velocimetry, we observe a three-dimensional azimuthal vortex pair that is maintained until the droplet is completely dried. The non-uniformly receding contact line motion breaks the flow symmetry. Finally, a simplified scaling model presents that the mechanical stress along the contact line is proportional to the vorticity magnitude, which is validated by the experimental results.
김송학,Susanne U. Mertens-Talcott,Bipin Vaidya,Vinicius Paula Venancio,조세영,송종암,Boon P. Chew,권조셉,김두운 한국식품과학회 2020 Food Science and Biotechnology Vol.29 No.12
Quantitative reverse transcription PCR (qRTPCR)is a sensitive method for the detection of foodborneviruses in fecal samples. However, the performance ofqRT-PCR depends on the efficiency of virus concentrationmethods. In this study, the effect of Concanavalin A (ConA)-immobilized on polyacrylate beads (Con A-PAB) onthe qRT-PCR performance, in terms of sensitivity andspecificity to detect foodborne viruses in human fecalspecimens was compared with commercial viral RNAextraction kit (VRNA). The detection of foodborne virusesby qRT-PCR was validated by viral genome sequencing. Both Con A-PAB and VRNA methods were equally sensitiveand specific for detecting hepatitis A virus in fecalspecimens. Even though both methods showed highspecificity (100% vs. 100%) for detecting human norovirus(HuNoV), Con A-PAB method exhibited higher sensitivity(100% vs. 42.9%) and accuracy (100% vs. 73.3%) comparedto VRNA method. In conclusion, the application ofCon A-PAB would improve the performance of qRT-PCRfor the detection of HuNoV in fecal samples.
Analysis of pile-up/sink-in during spherical indentation for various strain hardening levels
Shankar, S.,Loganathan, P.,Mertens, A. Johnney Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.3
The measurement from the indentation process depends on the amount of pile-up or sink-in around the contact impressions. In this paper, finite element concept is utilized to study the pile-up and sink-in behaviour for the wide range of materials with different young's modulus, yield stresses, strain-hardening exponents and coefficient of friction values. The exact indentation model is created by using the two dimensional axisymmetrical model for simulating the spherical indentation process on the lines of Taljat and Pharr (2004) work. The result shows that during spherical indentation process the amount of pile-up is greatly influenced by the strain hardening exponents in addition to other material properties and depth of penetration. The numerical results from the finite element analysis are also validated using the exact multilinear material properties obtained from the tensile testing for the materials like mild steel, brass and aluminium.
New Current Controller for Inverter Fed Medium Voltage Drives with LC Filter
Tomasz Laczynski,Axel Mertens 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
In high power medium voltage drives, the switching frequency of power semiconductor devices is restricted because of high switching losses. Such drives often include an LC output filter, introducing a resonant circuit that may be excited for instance by fast control transients. One way to avoid such oscillations is using damping control schemes, which in turn usually require switching frequencies well above the filter resonance. This paper proposes a new predictive stator current controller that avoids the excitation of the filter resonance, performs active damping and allows fast current control while maintaining low switching frequency. Simulation results of a 2.4 ㎸ induction motor drive and experimental results obtained from a 55 ㎾ prototype a.c. drive demonstrate feasibility and good dynamic performance of the proposed control approach.
Collapse behavior and forces of multistack nanolines
Kim, Tae-Gon,Wostyn, Kurt,Mertens, Paul W,Busnaina, Ahmed A,Park, Jin-Goo IOP Pub 2010 Nanotechnology Vol.21 No.1
<P>Two types of multistack nanolines (MNLs), Si-substrate (Si)/siliconoxynitride (SiON)/amorphous Si (a-Si)/ SiO<SUB>2</SUB> and Si/ SiO<SUB>2</SUB> /polycrystalline Si (poly-Si)/ SiO<SUB>2</SUB> were used to measure the collapse force and to investigate their collapse behavior by an atomic force microscope (AFM). The Si/SiON/a-Si/ SiO<SUB>2</SUB> MNL showed a larger length of fragment in the collapse patterns at a smaller collapse force. The Si/ SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB> MNL, however, demonstrated a smaller length of fragment at a higher applied collapse force. The collapse forces increased by the square of the linewidth in both Si/SiON/a-Si/ SiO<SUB>2</SUB> and Si<I>/</I>SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB> MNLs. Once an AFM tip touches an Si/SiON/a-Si/ SiO<SUB>2</SUB> line, which is a softer MNL, it was delaminated first at the Si/SiON interface. One end of the delaminated line was first broken and then the other end was bent until it was broken. A harder MNL, Si/ SiO<SUB>2</SUB> /poly-Si/ SiO<SUB>2</SUB>, however, was broken at two ends simultaneously after the delamination occurred at the Si/ SiO<SUB>2</SUB> /poly-Si interface. The different collapse behaviors were attributed to the magnitude of adhesion forces at the stack material interfaces and the mechanical strength of MNLs. </P>
Hyoungsoo Kim,Naser Belmiloud,Paul W. Mertens 한국가시화정보학회 2016 한국가시화정보학회지 Vol.14 No.2
We investigate an internal flow pattern of an evaporating droplet where the contact line non-uniformly recedes. By using tomographic Particle Image Velocimetry, we observe a three-dimensional azimuthal vortex pair that is maintained until the droplet is completely dried. The non-uniformly receding contact line motion breaks the flow symmetry. Finally, a simplified scaling model presents that the mechanical stress along the contact line is proportional to the vorticity magnitude, which is validated by the experimental results.