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A novel suspended GeSn microstructure is demonstrated by selective etching of GeSn thin film on Ge. XRD and μ-Raman measurements show that the compressive strain in the GeSn thin film is effectively relaxed, and furthermore, unexpected tensile strain was introduced in the suspended GeSn.
We present our recent researches on novel group IV nano- and micro-structures for potential light sources on Si, including the tensile strained Ge quantum dots (QDs), GeSn thin films and microstructures, and Ge(Sn) nanowires. Tensile-strained Ge QDs were grown by SS-MBE, and photoluminescence was achieved. The GeSn thin films were demonstrated with Sn concentration above the bandgap transition critical...
This paper first summarizes the research and development of microstrip grid array antennas for millimeterwave radio and radar applications over the recent years. Then the paper describes multiport microstrip grid array antennas to explore their use in multi-input and multi-output (MIMO) systems. Particular emphasis is given to the multiport excitation and isolation performances.
A dual-wavelength fiber laser based on thinned FBG for sensing refractive index is demonstrated by interrogating the separation of the two lasing wavelengths. The refractive index resolution of ∼10−5 is achieved.
Large cold storage capacity is very important to maintain the stable working condition of a superconducting magnet. Solid nitrogen is frequently used for cold storage at cryogenic temperatures. In this paper, we report the experimental investigation of the cold storage and cold release characteristics of a thermal battery unit using solid nitrogen, as well as the combination of solid nitrogen and...
Experiments are underway to study the stabilizing effects of an axial magnetic field on the magneto Rayleigh-Taylor (MRT), sausage, and kink instabilities in imploding liner-plasmas at the Michigan Accelerator for Inductive Z-pinch Experiments (MAIZE) facility at the University of Michigan (UM). The liners were fabricated from ultrathin aluminum foils and had thicknesses of 400 nm and 6.55 mm diameters,...
In this paper, failure modes of hybrid sandwich structures (HSS) with V-type corrugated cores subjected to water impact are discussed. The dynamic responses and failure mechanism investigated using the LS_Dyna lagrange-Euler coupling techniques reveal that the face sheets undergo large stretching and bending deformation, while the core webs experience plastic bucking failure. The numerical simulation...
This paper firstly summarises the main aims and delivery plans of an innovation project which is being implemented by National Grid (NG) and the University of Birmingham to co-develop an independent facility and methodology for protection and control (P&C) coordination studies using the Real Time Digital Simulation (RTDS). The technical considerations are discussed for achieving the technical...
This paper conducts an in-depth study on the damping characteristics of the damping controller added on the UPFC when two different control strategies are applied (vector control strategy and phase angle control strategy). Firstly, the structure of the UPFC and the principle of the vector and phase angle control strategy are presented in this paper. Then the linearized model of the system with a UPFC...
Exploring simultaneous transmission and reception at the same carrier frequency, in-band full duplex (IBFD) has great potential to double the spectral efficiency of wireless communications. However, IBFD also creates a major problem, that is, strong self-interference, which must be suppressed to the receiver noise floor to make it work. Thus, this paper first gives estimates of self-interference strength,...
During geomagnetic storms, the geoelectric field drives currents in transmission grids, railway system and pipelines. These geomagnetically induced currents (GIC) threaten the safe operation of equipment. The GIC recordings show that geological structure has significant implications for GIC in power gird (Liu Chunming et al. 2009). In the region with complex geological structure, the horizontal change...
The energy harvester using magnetostrictive materials (e.g., Metglas, Terfenol-D and Galfenol) is receiving increased attention [1]-[5]. However, prediction of performance for the magnetostrictive harvester is complicated because the device exhibits nonlinear magnetomechanical coupling characteristics and the stress-induced eddy current loss, which is the leading limiting factor of the device.
This paper studies fault detection problem of linear continuous-time periodic systems. At first, an optimal periodic observer-based residual generator is derived for the case of no model uncertainty, which achieves the best compromise between the sensitivity to faults and the robustness to unknown disturbances. Then, in order to deal with model uncertainty, a post-filter is introduced which provides...
In this paper, problems related to the design of fault detection filters (FDF) for dynamic systems with unknown inputs are studied. Core of our study is to consider the design problems under two different residual evaluation functions, the i?2-norm and the peak amplitude of the residual signals. The background of this study is the fault detection strategy of using multi-residual evaluation functions,...
We use the Briggs-Bers criterion to examine the absolute instability at the lower and upper band edges of a coupled cavity TWT. We find that the lower band-edge is not subjected to absolute instability. At the upper band-edge, we find a threshold beam current beyond which absolute instability is excited. In general, an absolute instability would occur in a linear beam tube if the cold-tube circuit...
The fault detection problems of multirate-output sampled-data (MROSD) systems and MROSD systems with time delays are investigated. The main advantage of the approaches presented in this paper is that they can take into consideration the intersample behavior of such systems. The basic idea is to observe the dynamics of the system at fast sampling instants and then downsample the discrete-time outputs...
This paper deals with the development of an observer based fault tolerant scheme for distributed networked control systems (NCS). The NCS under consideration consists of a number of nodes and is hierarchically structured with a central station at the higher level and subsystems distributed at the process level. The system nodes are connected by a communication network like Ethernet. The core of the...
This paper considers the problem of fast rate fault detection for multirate sampled-data systems. As a residual signal can only be generated at those time instants with sampled outputs, a new system description is obtained for the purpose of residual generation. Based on it, time-varying residual generators are designed, which take into account the intersample behaviour. Another important feature...
In this paper, multiple flexible AC transmission systems (FACTS) supplementary damping controllers are designed for the enhancement of system small-signal stability under different system operating points. A static var compensator (SVC) and a thyristor-controlled series compensator (TCSC) damping controller are designed sequentially with minimized decoupling effort. This approach is carried out with...
Traditionally, candidate lines for the transmission expansion planning are manually selected, which faces great challenges in terms of multi-regional planning and large penetration of renewable energy sources (RES). In this paper, an approach is proposed to select candidate set of transmission lines automatically. The utilization level of RES can be ensured by the created candidate set. Through the...
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