| 1. |
- Cao, Jianyin, et al.
(författare)
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W-band high-gain low profile circularly polarized magneto-electric dipole antenna array with gap waveguide feeding technology
- 2018
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Ingår i: IET Conference Publications. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- In this paper, a high gain circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna array excited by the air cavity in gap waveguide (GWG) feeding technology in W-band is proposed. This antenna array is composed of two layers, upper CP ME-dipole antenna subarrays and lower metallic GWG feeding networks. The planar antenna array structure is realized by the high mode air cavity feeding network, which is realized by extending the 1×2 cavity to 3×2 cavity using more shorted pins to split the electromagnetic field. The whole single-layer GWG feeding network is composed of a ridge gap waveguide (RGWG) transmission structure and short-ended vertical polarized groove gap waveguide (VP-GGWG) high mode air cavities. The transmission loss caused by the coupling and the fabrication tolerance can be reduced by combining the RGWG and GGWG in the same layer. In addition, the feeding network is fabricated all in metal with no substrate loss. Transverse slots are etched at the right position of the printed circuit board (PCB) backside to excite the CP ME-dipoles. The antenna element has stable radiation patterns and wide axial-ratio (AR) bandwidth. The proposed 3×8 planner antenna array has a maximum boresight gain of 22 dBi and an AR bandwidth of 10.8% for AR < 3 dB. In the frequency band from 87.7 to 97.7 GHz, a boresight gain above 20 dBi is achieved.
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| 2. |
- Liu, Jian, et al.
(författare)
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Investigation of heat transfer and fluid flow over pocket cavity in the rear part of gas turbine
- 2016
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Ingår i: Heat Transfer and Thermal Engineering. - 9780791850626 ; 8
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Konferensbidrag (refereegranskat)abstract
- The pocket cavity is generated at the transition part between the low pressure turbine (LPT) and outlet guide vane (OGV) in a gas turbine engine. Because the important connection with OGV, the heat transfer and fluid flow need to be investigated and analyzed. In the present work, a simplified triangular pocket cavity is built and heat transfer and fluid flow are investigated experimentally and numerically. Liquid Crystal Thermography (LCT) is employed to measure the heat transfer over the pocket surface with Reynolds number ranging from 54,054 to 135,135. In addition, two fillets with different radii are designed to investigate the flow structures over the pocket surface. The turbulent flow details are provided by numerically calculations based on the commercial software Fluent 15.0 with a validated turbulence model. Based on the results, the highest heat transfer value is located in the downstream boundary of the pocket cavity where the strongest flow impingement happens. The smaller fillet radius presents a higher heat transfer peak value and also induces stronger recirculating flow inside the pocket cavity. Considering the design requirement in the rear part of a gas turbine, i.e., to decrease the heat transfer peak value, a larger fillet radius is recommended for practical design. The heat transfer and flow details also provide a reliable reference for gas turbine engine design.
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| 3. |
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| 4. |
- He, Dandan, et al.
(författare)
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Design of a Low Sidelobe Monopulse Array Antenna with Hybrid Feeding Structure
- 2019
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Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- A low sidelobe monopulse array antenna with hybrid feeding structure is proposed. The array consists of four subarrays which employ 6 × 8 microstrip patch elements on the top layer. The feed network, which is hybrid feeding structure, is composed of 1-to-48 microstrip power dividers on the top layer, microstrip to groove gap waveguide transitions and a gap waveguide-based monopulse comparator. The microstrip unequal power dividers are compact to achieve unequal amplitude distribution. And the monopulse comparator based on groove gap waveguide has low insertion loss. Hence, the array antenna achieves low sidelobe and high efficiency. The array antenna is designed with size of 400 × 320 mm2. The simulated VSWR is less than 1.5 from 10.52 - 10.68 GHz, the simulated gain is 28.7 dBi at 10.6 GHz and the sidelobe level is less than -19 dB. The null depth in the difference pattern is less than -35 dB.
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| 5. |
- Hussain, Safeer, et al.
(författare)
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Endwall heat transfer enhancement around cylinders with a wall-mounted vortex generator pair
- 2017
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Ingår i: Heat Transfer and Thermal Engineering. - 9780791858431 ; 8
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Konferensbidrag (refereegranskat)abstract
- Measurement of endwall heat transfer around a circular cylinder with a vortex generator pair has been investigated. Steady state liquid crystal thermography is adopted. Cylinders having two different height to diameter ratios have been employed. In one case, the cylinder has one end free in the flow and in the other case it has both ends attached on the walls. Local Nusselt numbers both upstream and downstream of the cylinder with and without the vortex generator pair are calculated. Nusselt numbers in streamwise and spanwise directions for both cases with vortex generator are compared with each other as well as with corresponding base cases. It is found from the experiments that the vortex generator influences the endwall heat transfer significantly downstream of the cylinder but has a small effect in the upstream region. Moreover, for different height to diameter ratio of the cylinder different heat transfer patterns are observed downstream of the cylinder. The vortex generator pair plays its major role on the endwall heat transfer enhancement in the spanwise direction and it expands as one moves from the upstream to downstream direction. To fully understand the advantage of the vortex generator pair, thermal performance is calculated for each case and it was found that in presence of the vortex generator pair, the cylinder with shorter height to diameter ratio shows higher thermal performance. Reynolds number dependence has also been investigated and it was found that the thermal performance decreases with increasing Reynolds number for both cases having a vortex generator pair.
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| 6. |
- Hussain, Safeer, et al.
(författare)
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Experimental investigation of heat transfer enhancement on the endwall around an obstacle embedded with a vortex generator pair
- 2018
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Ingår i: Proceeding: International Heat Transfer Conference 16. - 2377-424X. ; , s. 4971-4978
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Konferensbidrag (refereegranskat)abstract
- Heat transfer enhancement on the endwall around an obstacle embedded with a pair of vortex generators is investigated. Obstacles with cylindrical and square cross sections are experimentally examined and compared with and without vortex generators. The vortex generators employed is a pair of longitudinal winglet vortex generator. Local Nusselt numbers are calculated for both types of obstacles in presence of vortex generator experimentally whereas, flow features are captured numerically using ANSYS-FLUENT 17.0. A high heat transfer region upstream of the obstacle has increased its width with the installation of vortex generators for both shapes of the obstacle. However, only a small increase in magnitude occurs. Comparison of local Nusselt numbers shows that for the case of the cylindrical obstacle, there is more heat transfer at the center of the obstacle whereas, for the obstacle with square cross section, more heat transfer is observed at the upstream corners of the obstacle both with and without vortex generators. It is also evident from the findings of the results that installation of vortex generators upstream of an obstacle enhances the endwall heat transfer more in the spanwise direction than the streamwise direction. In addition, flow characteristics obtained from the numerical simulations show that presence of a vortex generator pair reinforces the strength of the horseshoe vortex and as a result additional heat transfer enhancement. Thermal performance for both types of obstacles in presence of vortex generators are calculated and compared at various Reynolds number.
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| 7. |
- Hussain, Safeer, et al.
(författare)
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Reduction of heat transfer on the endwall in the upstream junction region of a symmetric airfoil with vortex generator pair
- 2018
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Ingår i: ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition : Heat Transfer - Heat Transfer. - 9780791851098 ; 5B
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Konferensbidrag (refereegranskat)abstract
- Heat transfer on the endwall upstream of the junction of the stator vane/rotor blade with the hub becomes very high due to the vortices generated as a result of an adverse pressure gradient. Control of this high heat transfer is very vital for safe operation of gas turbines. In the present experimental study, a pair of vortex generators is employed to reduce the high heat transfer on the endwall close to the junction region. A pair of winglet vortex generators upstream of a symmetric airfoil have been employed. The steady state liquid crystal thermographic method is used to measure the surface temperature of the endwall. Different cases are studies depending on various lateral gaps of the vortex generator pair while keeping the yaw angle and streamwise position relative to the airfoil constant. It is found from the experiments that all positions of the vortex generators reduce the heat transfer on the junction region of the endwall compared to the base case. The level of reduction and local distribution of heat transfer is dependent on the position of vortex generators. The aerodynamic performance of a stator vane/rotor blade is the main objective in gas turbines, therefore the pressure drop is also measured experimentally and results show that pressure loss is recovered with the installation of vortex generator compared to the airfoil without the vortex generator.
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| 8. |
- Jian, Wang, et al.
(författare)
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A PSO-Based Layout Method for GNSS Pseudolite System
- 2017
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Ingår i: Proceedings of the 2017 International Conference on Information Technology. - New York, NY, USA : ACM. - 9781450363518 ; , s. 313-317
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Konferensbidrag (refereegranskat)abstract
- In order to improve the user positioning accuracy in GNSS (Global Navigation Satellite System) pseudolite system, we propose a PSO (Particle Swarm Optimization)-based method to optimize the pseudolite layout in this paper. In detail, given the pseudolite layout information, we calculate the system GDOP (Geometric Dilution of Precision) and then minimize it by using a PSO-based algorithm with N particles. Here the first particle indicates the classical layout under the given scenario and the other particles separately represent N-1 randomly generated layouts. In each iteration of our PSO-based algorithm, these particles move to a direction to reduce the GDOP value. After several iterations, the GDOP value can be minimized and the optimal pseudolite layout is found out as well. To evaluate the merits of our method, we perform some experiments. The experimental results show that compared to the classical pseudolite layout, our method can reduce the GDOP by 13.4%. This, with no doubt, improves the user positioning accuracy. For example, when the pseudo-range error is about 1%, the user positioning accuracy in our optimized layout can be improved by 12.4% against the classical layout.
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| 9. |
- Jinzhi, Lu, 1988-, et al.
(författare)
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A Fault Propagation Model for FPGA Netlist with Un-reconvergence Paths
- 2018
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Ingår i: Proceedings - 2018 5th International Conference on Information Science and Control Engineering, ICISCE 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538655009 ; , s. 1015-1015
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose an analysis method of fault propagation based on the FPGA netlist with un-reconvergence path. First of all, we analyze the characteristics of common components in the netlist, calculate the fault propagation probability of these components, and then establish a netlist-level fault propagation model based on the interconnection topological structure of the components in the netlist. When a fault happens at input ports of the netlist, we analyze the fault propagation characteristics in the whole netlist, calculate the probability of the fault propagating from input to output ports, and find out the input port which is most likely to cause the fault. Finally, we verify the model presented in this paper by experiments. The experimental results show that the estimated error of fault propagation probability is negligible. It is less than 0.1% compared to the corresponding testing results.
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| 10. |
- Jinzhi, Lu, 1988-, et al.
(författare)
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A Tool Integration Language to Formalize Co-simulation Tool-chains for Cyber-physical System (CPS)
- 2017
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Konferensbidrag (refereegranskat)abstract
- Co-simulation has grown from point-to-point between simulation tools for specific purposes to complex tool-chains which often require additional functionalities, e.g., process management, data management, and tool integration. With these additional functionalities, the related design activities could be controlled and implemented by uni- ed platforms to improve eciency and effectiveness. Due to increasing complexity and size of co-simulation tool-chains, a systematic approach is needed to formalize their evolution in order to analyze functionalities and evaluate their structures before development. In this paper, we extend a proposed domain specific language, - named Tool Integration Language (TIL) - to describe co-simulation tool-chain architectures on a high abstraction level aiming to promote the eciency and e effectiveness of co-simulation tool-chain development by the use of Model-based System Engineering (MBSE). We introduce how the extended TIL formalizes structures and present two industrial cases of co-simulation tool-chain from previous experiences and describe them using the TIL. Finally, we conclude this paper and introduce future work -a further extension of TIL supporting MBSE tool-chain development.
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