The second order nonlinear conductance of a two-dimensional mesoscopic conductor

We have investigated the weakly non-linear quantum transport properties of a two-dimensional quantum conductor. We have developed a numerical scheme which is very general for this purpose. The nonlinear conductance is computed by explicitly evaluating the various partial density of states, the sensitivity and the characteristic potential. Interesting spatial structure of these quantities are revealed. We present detailed results concerning the crossover behavior of the second order nonlinear conductance when the conductor changes from geometrically symmetrical to asymmetrical. Other issues of interests such as the gauge invariance are also discussed.Comment: LaTe

A multi-sensor based online tool condition monitoring system for milling process

Tool condition monitoring has been considered as one of the key enabling technologies for manufacturing optimization. Due to the high cost and limited system openness, the relevant developed systems have not been widely adopted by industries, especially Small and Medium-sized Enterprises. In this research, a cost-effective, wireless communication enabled, multi-sensor based tool condition monitoring system has been developed. Various sensor data, such as vibration, cutting force and power data, as well as actual machining parameters, have been collected to support efficient tool condition monitoring and life estimation. The effectiveness of the developed system has been validated via machining cases. The system can be extended to wide manufacturing applications

Weak Decays of Doubly Heavy Baryons: the 1/2→1/21/2\to 1/2 case

Very recently, the LHCb collaboration has observed in the final state $\Lambda_c^+ K^-\pi^+\pi^+$ a resonant structure that is identified as the doubly-charmed baryon $\Xi_{cc}^{++}$. Inspired by this observation, we investigate the weak decays of doubly heavy baryons $\Xi_{cc}^{++}$, $\Xi_{cc}^{+}$, $\Omega_{cc}^{+}$, $\Xi_{bc}^{(\prime)+}$, $\Xi_{bc}^{(\prime)0}$, $\Omega_{bc}^{(\prime)0}$, $\Xi_{bb}^{0}$, $\Xi_{bb}^{-}$ and $\Omega_{bb}^{-}$ and focus on the decays into spin $1/2$ baryons in this paper. At the quark level these decay processes are induced by the $c\to d/s$ or $b\to u/c$ transitions, and the two spectator quarks can be viewed as a scalar or axial vector diquark. We first derive the hadronic form factors for these transitions in the light-front approach and then apply them to predict the partial widths for the semi-leptonic and non-leptonic decays of doubly heavy baryons. We find that a number of decay channels are sizable and can be examined in future measurements at experimental facilities like LHC, Belle II and CEPC.Comment: 40 pages, 4 figures, to appear in EPJ

Concentration of PAHs on different soot particle sizes generated by pyrolysis of a wide range of fuel molecules

Particulates and polycyclic aromatic hydrocarbons (PAH) are products of incomplete combustion from various human activities. The PAHs are carcinogenic to humans and are attached to particulates of different sizes. It is these volatile organic compounds (VOC) that are responsible for the adverse health impacts on humans. The fine particulates are capable of penetrating deep into the lungs while possessing great deposition efficiency, especially those in the ultrafine region (<100nm). The greater the attachment of these toxic PAHs to ultrafine particles, the more dangerous the health impact becomes, as they can be delivered deeper into the lungs, causing more severe health issues. This indicates that the health effects of particulate PAHs are strongly size-dependent. As there is a transition away from fossil fuels to future renewable fuels, there is a need to understand potential correlations between fuel molecular effects on the particulate PAH size distribution. This thesis therefore investigates the effect of fuel molecular structure on the particulate size distribution and the associated PAH distribution across particles of different sizes, specifically, looking at a series of C6 hydrocarbons each containing a different functional group. T t st u ls w r suppl to n oxy n r l m n low r tor t n t onst nt r on low rate of 10000ppm on a C1 basis. Soot particles from the pyrolysis of all the fuels were sampled and segregated using a nano-MOUDI cascade impactor, capable of separating particles into 15 size segments from 10 nm to 18 µm. Condensed PAH were subsequently extracted from the size segregated particles and quantified by gas chromatography mass spectrometry (GC-MS). 16 priority PAHs listed by the US EPA were investigated, paying specific attention to the 7 PAHs highlighted by the EPA as the B2 group, which are categorised as possibly carcinogenic to human. The results indicated that oxygenated fuels tend to promote the formation of smaller particles. Consequently, a higher degree of PAH condensation on the finer particles was observed during oxygenated fuel pyrolysis compared to other fuel structures. Aromatic structures were observed to exhibit the highest degree of soot formation; however, this resulted in a limited abundance of PAH formation. As a result, a lower amount of total PAHs was found attached to the aromatic fuel-induced particles. Nevertheless, the attached PAH species from the aromatic and cyclic fuel structures were more carcinogenic, with a higher degree of toxic PAHs attached to various particle sizes. Regarding the influence of fuel on PAH particle size distribution, ester structures exhibited the lowest median mass aerodynamic diameter (MMAD), indicating that PAHs tend to be attached to smaller particles compared to other structures, while alkane structures exhibited the opposite trend, with PAH distribution tending to be on larger particles with the highest MMAD