Study on energy dynamic change law in the process of water-contained coal caused by liquid nitrogen freezing

To study the energy dynamic change law of moisture-contained coal in the process of liquid nitrogen freezing, a self-developed acoustic emission (AE) experimental system for the whole process of liquid nitrogen frozen coal was utilized to analyze the characteristics and the change laws of AE energy dissipation in the whole process of liquid nitrogen freezing in coal with different moisture contents. The results shown that AE energy during liquid nitrogen freezing of coal was divided into steep, fluctuating and calm periods in the time domain. The primary and secondary peaks of energy were both positively linearly related to moisture content, and the primary and secondary energy peak of 5.96% moisture content were 1.66 and 2.26 times higher than those of dry coal. The cumulative energy of liquid nitrogen frozen coal, divided into three stages of steep increase, slow growth and stabilization versus time, was positively linearly related to moisture content, which of 5.96% moisture contained coal was 2.88 times higher than that of dry coal. The energy amplitude of different moisture content coals was mostly concentrated in the range of 40-50 dB, accounting for 94.39%-99.11% of the total, and decreased linearly with the increasing moisture content of coal. The time series of acoustic emission ringing counts in liquid nitrogen frozen coals had chaotic fractal characteristics, and the correlation dimensions of the steep increase, slow growth and stable stages were positively exponentially, linearly and linearly correlated with the moisture content, respectively. Furthermore, the correlation dimension in the steep increase stage of 5.96% moisture contained coal was 2.00 and 5.78 times higher than that of the slow growth and stable stage, respectively. The type of coal cracks produced by the liquid nitrogen freezing was mainly tensile, its proportion with the increasing moisture content was a negative exponential decrease, and the proportion of shear cracks positively linearly increased with the increasing moisture content. The increase of moisture in coal strengthened the freezing and expansion force generated by the water-ice phase transition during the liquid nitrogen freezing process, and the increase of energy dissipation contributed to the rapid development of pore-crack and the structural damage and plastic deformation of coal. However, the structural damage was difficult to detect in real time and can be inverted by AE energy

In vivo evaluation of additively manufactured multi-layered scaffold for the repair of large osteochondral defects

The repair of osteochondral defects is one of the major clinical challenges in orthopaedics. Well-established osteochondral tissue engineering methods have shown promising results for the early treatment of small defects. However, less success has been achieved for the regeneration of large defects, which is mainly due to the mechanical environment of the joint and the heterogeneous nature of the tissue. In this study, we developed a multi-layered osteochondral scaffold to match the heterogeneous nature of osteochondral tissue by harnessing additive manufacturing technologies and combining the established art laser sintering and material extrusion techniques. The developed scaffold is based on a titanium and polylactic acid matrix-reinforced collagen “sandwich” composite system. The microstructure and mechanical properties of the scaffold were examined, and its safety and efficacy in the repair of large osteochondral defects were tested in an ovine condyle model. The 12-week in vivo evaluation period revealed extensive and significantly higher bone in-growth in the multi-layered scaffold compared with the collagen–HAp scaffold, and the achieved stable mechanical fixation provided strong support to the healing of the overlying cartilage, as demonstrated by hyaline-like cartilage formation. The histological examination showed that the regenerated cartilage in the multi-layer scaffold group was superior to that formed in the control group. Chondrogenic genes such as aggrecan and collagen-II were upregulated in the scaffold and were higher than those in the control group. The findings showed the safety and efficacy of the cell-free “translation-ready” osteochondral scaffold, which has the potential to be used in a one-step surgical procedure for the treatment of large osteochondral defects

Multiferroicity in doped hexagonal LuFeO3

The hexagonal phase of LuFeO3 is a rare example of a multiferroic material possessing a weak ferromagnetic moment, which is predicted to be switchable by an electric field. We stabilize this structure in bulk form though Mn and Sc doping, and determine the complete magnetic and crystallographic structures using neutron-scattering and magnetometry techniques. The ferroelectric P6(3)cm space group is found to be stable over a wide concentration range, ordering antiferromagnetically with Neel temperatures that smoothly increase following the ratio of c to a (c/a) lattice parameters up to 172 K, the highest found in this class of materials to date. The magnetic structure for a range of temperatures and dopings is consistent with recent studies of high quality epitaxial films of pure hexagonal LuFeO3 including a ferromagnetic moment parallel to the ferroelectric axis. We propose a mechanism by which room-temperature multiferroicity could be achieved in this class of materialsopen

Enhanced Multiferroicity in LuFeO3 Through Sc Doping

Hexagonal manganites of the type \textit{R}MnO3 are well known examples of single-phase multiferroic materials, but suffer from low magnetic ordering temperatures and weak magnetoelectric coupling making them unsuitable for implementation in devices. Recently, the isostructural ferrites \textit{R}FeO3 have been proposed as promising materials to exhibit greatly enhanced magnetic properties, including a much stronger coupling mechanism between ferromagnetic moment and ferroelectic polarization. Here we present a magnetometry and neutron scattering investigation of LuFeO3 forced into the ferroelectric structure through Sc-doping. We find the magnetic ordering temperature dramatically increases relative to pure hexagonal LuFeO3 and LuMnO3, as well as an unusual spin-reorientation at low temperatures. We will discuss possible mechanisms for this reorientation and how it provides insight into the enhanced magnetic properties Limit of the \textit{R}FeO3 series

Fabrication of SiGe/Si Multi-Quantum Wells Resonant-Cavity-Enhanced Detector

A SiGe/Si multi-quantum wells resonant-cavity-enhanced(RCE) detector with high reflectivity bottom mirror is fabricated by a new method.The bottom mirror is deposited in the hole,which is etched from the backside of the sample by ethylenediamine-pyrocatechol-water(EPW) solution with the buried SiO2 layer in SOI substrate as the etching-stop layer.Reflectivity spectrum indicates that the mirror deposited in the hole has a reflectivity as high as 99% in the range of 1.2～1.5μm.The peak responsivity of the RCE detector at 1.344μm is 1.2mA/W and the full width at half maximum is 12nm.Compared with the conventional p-i-n photodetector,the responsivity of RCE detector is enhanced 8 times

Fabrication of 1.55μm Si-Based Resonant Cavity Enhanced Photodetectors

A novel bonding method using silicate gel as bonding medium is developed.High reflective SiO2/Si mirrors deposited on silicon substrates by e-beam deposition are bonded to the active layers at a low temperature of 350℃ without any special treatment on bonding surfaces.The reflectivities of the mirrors can be as high as 99.9%.A Si-based narrow band response InGaAs photodetector is successfully fabricated,with a quantum efficiency of 22.6% at the peak wavelength of 1.54μm,and a full width at half maximum of about 27nm.This method has a great potential for industry processes