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Broadband and asymmetrical Doherty based on circuit parameter solution space

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Frontiers of Information Technology & Electronic Engineering 2024年第11期25卷 1552-1564页

作者： Cheng BI Haotian LI Shuai WANG Zhijiang DAI jingzhou pang Ruibin GAO Kang ZHONG Jingsong WANG School of Microelectronics and Communication Engineering Chongqing UniversityChongqing 400044China The 54th Research Institute of China Electronics Technology Group Corporation Shijiazhuang 050081China

The input impedance of the post-matching network(PMN)is configured as a complex *** parameter solution space is determined based on the fundamental principles of the Doherty power amplifier(DPA),enabling the DPA to achieve high efficiency at the output power back-off(OBO).The parameter solution space comprises three variables:the phase parameter of the output matching network for the carrier power amplifier(carrier PA),the phase parameter of the output matching network for the peaking power amplifier(peaking PA),and the input impedance of *** parameters are optimized to enable the DPA to achieve high efficiency at the *** this paper,a one-to-one mapping relationship is established between the frequency and the parameter solution space,allowing for a precise optimization of the DPA across a broad frequency *** this mapping relationship,an asymmetric DPA designed to operate over the 1.8–2.6 GHz frequency band is designed and fabricated,demonstrating the feasibility and effectiveness of the proposed *** continuous wave excitation,the test results show that the drain efficiency(DE)is 42.7%–56.4%at 9.5 dB OBO and the saturated DE is 45.8%–71.1%.The saturated output power of this DPA is 46.9–48.8 dBm with a gain of 5.5–8.0 dB at saturation.A 20-MHz long-term-evolution modulated signal with a peak-to-average power ratio of 8 dB is also applied to the fabricated DPA at 1.8,2.1,and 2.6 *** these conditions,at 8 dB OBO,the DPA shows an adjacent channel power ratio always lower than 48 dBc after digital pre-distortion linearization.

关键词： Doherty power amplifier Output matching network Parameter solution space

Broadband Sequential Load-Modulated Balanced Amplifier Using Coupler-PA Co-Design Approach

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ZTE Communications 2022年第4期20卷 62-68页

作者： RAN Xiongbo DAI Zhijiang ZHONG Kang pang jingzhou LI Mingyu School of Microelectronics and Communication Engineering Chongq-ing UniversityChongqing 400044China

The basic theory of the sequential load-modulated balanced amplifier(SLMBA)is introduced and the working principle of its active load modulation is analyzed in this *** order to further improve the performance of the SLMBA,a codesigned method of the coupler and power amplifier(PA)is proposed,which is different from the traditional design of *** to the back-off point and saturation point of the SLMBA,this coupler-PA codesign approach can make the working state of the coupler and three-way PA closer to the actual situation,which improves the overall performance of the *** maximum output power ratio of the control PA and the balance PA is then determined by the preset output power back-off(OBO)of 10 dB,and the phase compensation line is determined by the trace of the load modulation impedance of the balanced *** order to verify the proposed method,an SLMBA operating at 1.5–2.7 GHz(57%relative bandwidth)is *** layout simulation results show that its saturated output powers achieve 40.7–43.7 dBm and the small signal gains are 9.7–12.4 ***,the drain efficiencies at the saturated point and 10 dB OBO point are 52.7%–73.7%and 44.9%–59.2%respectively.

关键词： SLMBA broadband coupler co-design

Dynamic portfolio choice with uncertain rare‑events risk in stock and cryptocurrency markets

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Financial Innovation 2023年第1期9卷 1967-1994页

作者： Wujun Lv Tao pang Xiaobao Xia jingzhou Yan Department of Statistics College of ScienceDonghua UniversityNo.2999 Renmin North RoadSongjiang DistrictShanghai 201620China Department of Mathematics North Carolina State University2311 Stinson DriveRaleighNC 27695‑8205USA School of Economics Fudan University600 Guoquan RoadShanghai 200433China School of Economics Sichuan University24 South Section 1Yihuan RoadChengdu 610065SichuanChina

In response to the unprecedented uncertain rare events of the last decade,we derive an optimal portfolio choice problem in a semi-closed form by integrating price diffusion ambiguity,volatility diffusion ambiguity,and jump ambiguity occurring in the traditional stock market and the cryptocurrency market into a single *** reach the following conclusions in both markets:first,price diffusion and jump ambiguity mainly determine detection-error probability;second,optimal choice is more significantly affected by price diffusion ambiguity than by jump ambiguity,and trivially affected by volatility diffusion *** addition,investors tend to be more aggressive in a stable market than in a volatile ***,given a larger volatility jump size,investors tend to increase their portfolio during downward price jumps and decrease it during upward price ***,the welfare loss caused by price diffusion ambiguity is more pronounced than that caused by jump ambiguity in an incomplete *** findings enrich the extant literature on effects of ambiguity on the traditional stock market and the evolving cryptocurrency *** results have implications for both investors and regulators.

关键词： Robust portfolio choice Detection error probability Rare events Ambiguity Cryptocurrency Welfare loss

Influence of Multi-hole Arrangement on Cooling Film Development

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Chinese Journal of Aeronautics 2012年第2期25卷 182-188页

作者： YANG Chengfeng ZHANG jingzhou AVIC The First Aircraft Institute Xi＇ an 710089 China College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

A series of computations is conducted for many multi-hole arrangements at several blowing ratios to further investigate the evolution of the film from multi-holes. The influence of multi-hole arrangement on effusion film cooling is analyzed and a preliminary relationship evaluating the film development from developing state to developed state is brought forward. Results show that the coolant jets from front rows of multi-holes merge rapidly and the strength of the kidney vortices due to mainstream-coolant jet interaction in the downstream region are mitigated under super-long-diamond arrangement where the streamwise hole-to-hole pitch is bigger than spanwise hole-to-hole pitch. The holes array arranged in super-long-diamond mode is not only in favor of obtaining developed film layer, but also improving averaged adiabatic film cooling effectiveness.

关键词： effusion cooling multi-hole arrangement cooling effectiveness film development numerical simulation

Improvement on shaped-hole film cooling effectiveness by integrating upstream sand-dune-shaped ramps

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Chinese Journal of Aeronautics 2021年第4期34卷 42-55页

作者： Shengchang ZHANG jingzhou ZHANG Xiaoming TAN College of Energy and Power Engineering Key Laboratory of Thermal Management and Energy Utilization of AircraftNanjing University of Aeronautics and AstronauticsNanjing 210016China

A numerical investigation and experimental validation is performed to address deeper insights into the combined effect of shaped holes and Sand-Dune-shaped upstream Ramp(SDR)on enhancing the film cooling effectiveness,under a wide blowing ratio range(M=0.25–1.5).Three kinds of holes(Cylindrical Hole(CH),Fan-Shaped Hole(FSH),and Crater-Shaped Hole(CSH))are taken into *** SDR shows an inherent affecting mechanism on the mutual interaction of *** aggravates the lateral spreading of cooling jet and thus improves the film cooling uniformity significantly,regardless of film-hole shape and blowing *** the blowing ratio is beyond 1.0,the combined effect of shaped holes and SDR on improving film cooling effectiveness behaves more *** is suggested that FSH-SDR is a most favorable film cooling *** FSH-SDR case,the spatially-averaged film cooling effectiveness is increased monotonously with the increase of blowing ratio,among the present bowing ratio range.

关键词： Adiabatic film cooling effectiveness Film cooling Numerical simulation Sand-dune-shaped ramp Shaped hole

Investigation on film cooling characteristics from a row of converging slot-holes on flat plate

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Science China(Technological Sciences) 2011年第7期54卷 1793-1800页

作者： YAO Yu ZHANG jingzhou College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Experimental and numerical researches were conducted to investigate the cooling performance of a single row of consoles （converging slot-hole） on a large-scale flat-plate model. The results show that the coolant flow from a row of consoles shows good lateral uniformity of adiabatic effectiveness, with regions of slightly enhanced cooling occurring between the consoles. For the console cooling geometry, the interaction between coolant jet from inclined console and the mainstream flow results in reasonable vortices configuration. A pair of counter rotating vortices originate from the edge of slot, not from the centerline of film holes and the rotating direction is contrary to conventional cylindrical hole. The heat transfer coefficient ratio is a tittle bigger for the console case than conventional cylindrical hole, and the discharge coefficient for a console is larger than that for cylindrical film cooling hole.

关键词： film cooling converging slot-hole cooling effectiveness heat transfer coefficient discharge coefficient

Experimental study on flow and heat transfer characteristics of synthetic jet driven by piezoelectric actuator

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Science China(Technological Sciences) 2007年第2期50卷 221-229页

作者： ZHANG jingzhou TAN XiaoMing College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

To investigate the flow and heat transfer characteristics of a synthetic jet driven by piezoelectric actuator, experimental investigation utilizing particle image veloci- metry, hot-wire anemometer and infrared camera was carried out. The results show that: (1) At the jet orifice exit, pairs of vortexes are generated, broken down and merged together periodically, forming a steady jet within a several slot width from distance near the orifice exit. And during the development, the synthetic jet spreads rapidly along the minor axis direction of the orifice. While along the major axis direction, the synthetic jet contracts firstly and then spreads slowly. (2) Exci- tation frequency forced on the actuator has a great effect on the synthetic jet flow field. There are two resonance frequencies at which the mean velocity and vorticity of the synthetic jet are maximized, especially at the higher resonance frequency. The resonance frequency values obtained by the experiment are lower than the theoretical values. (3) Similarly to the common jet impingement, the convective heat transfer coefficients at the target surface impinged by the synthetic jet also take on up-down tendency varying with the jet-to-surface spacing increment. But the jet-to-surface spacing ratio for optimum cooling achievement is greater and the cooling action region is wider than the former, indicating that the synthetic jet in- troduces a stronger entrainment and more vigorous penetration in the surrounding fluid.

关键词： synthetic jet impinging cooling flow heat transfer

Effects of forward-flight speed on plume flow and infrared radiation of IRS-integrating helicopter

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Chinese Journal of Aeronautics 2022年第3期35卷 155-168页

作者： Zongyao YANG jingzhou ZHANG Yong SHAN Key Laboratory of Thermal Management and Energy Utilization of Aircraft of Ministry of Industry and Information Technology College of Energy and Power EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

To address deeper understandings about the aero-thermal performance of an integrating infrared suppressor under more realistic situations,a numerical investigation is motivated in the current study,concerning the effects of forward-flight speed on exhaust plume flow and infrared radiation of the Infrared Suppressor-integrating(IRS-integrating)helicopter,wherein the forward-flight speed is changed from 0 m/s(hover state)to 100 m/s,while both the engine exhaust parameters and the main-rotor operation parameters remains unchanged during different forward-flight *** results show that the interaction between forward-flight flow and downwash flow alters the exhaust plume development and the internal flow inside the IRS-integrating rear fuselage more complicatedly,tightly dependent on the forward-flight *** particular concern is the situation where the forward-flight flow has nearly the same level as the downwash flow,the hot mixing flow could possibly interacts with the helicopter rear fuselage to play a local heating *** the increase of forward-flight speed,the ejection coefficient is generally increased and the average exhaust temperature of mixing flow is decreased,leading to a reduction of the infrared radiation intensity of exhaust plume in 3–5 lm ***,the influence of forward-flight speed on the overall infrared radiation intensity of IRS-integrating helicopter is conjectured not monotonous due to the complicated interaction between forward-flight flow and downwash *** high-speed forward-flight states,the overall infrared radiation intensity of the IRS-integrating helicopter in 3–5 lm band is reduced with the increase of forward-flight *** respect to 3–5 lm band,the forward-flight speed has little effect on the infrared radiation in 8–14 lm band.

关键词： Exhaust plume Forward-flight speed Helicopter Infrared radiation Integrating infrared suppressor

Thermo-elasto-hydrodynamic analysis of a specific multi-layer gas foil thrust bearing under thermal-fluid–solid coupling

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Chinese Journal of Aeronautics 2023年第12期36卷 231-246页

作者： Qihong GAO Wenjing SUN jingzhou ZHANG College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Thermal Management and Energy Utilization of AircraftNanjing University of Aeronautics and AstronauticsNanjing 210016China

Gas foil bearing faces severe and complex thermal-fluid–solid coupling issues when in ultra-high speed and miniaturized impeller *** this study,a Thermo-Elasto-Hydrodynamic(TEHD)analysis of a specific multi-layer gas foil thrust bearing on the continuous loading process within a steady rotational speed is numerically investigated by a three-dimensional thermal-fluid–solid coupling *** indicate that the multi-layer foil exhibits nonlinear overall stiffness,with the thrust bottom foil serving as the primary elastic deformation structure,while the thrust top foil maintains a well-defined aerodynamic shape during a loading process,which helps reduce frictional damage and achieve an adequate loading *** low loads,the fluctuation of the gas film is extremely sensitive,and it weakens dramatically as the load *** viscous heating and friction torque exhibit a linear relationship with an increasing bearing load after a rapid *** on the exact stacking sequence and contact position of the multi-layer gas foil,the overlapping configuration allows for efficient transfer of viscous-shearing heat accumulated at the smallest air film through thermal conduction while providing elastic *** to the strong inhomogeneity of the viscous heat under varying loads,the temperature distribution on the top foil surface shows pronounced variations,while the difference between the peak and average temperatures of the thrust plate and top foil surfaces widens substantially with an increasing load.

关键词： Gas foil thrust bearing Thermo-elastohydrodynamic analysis Thermal-fluid–solid coupling simulation Adaptive deformation Structural stiffness