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半导体技术 2025年第1期50卷 95-100页

作者：陈澄尹红波王成倪大海谢璐曾超林扬州海科电子科技有限公司江苏扬州225001

纳米银胶的烧结温度一般为250℃及以上,而在功率模块装配过程中,多温度梯度装配工艺要求纳米银胶的烧结温度不得超过217℃。使用800HT2V纳米银胶烧结钼铜载体与铝合金外壳,观察了不同烧结温度下纳米银胶装配后的微观形貌,测试了其装配... 详细信息

纳米银胶的烧结温度一般为250℃及以上,而在功率模块装配过程中,多温度梯度装配工艺要求纳米银胶的烧结温度不得超过217℃。使用800HT2V纳米银胶烧结钼铜载体与铝合金外壳,观察了不同烧结温度下纳米银胶装配后的微观形貌,测试了其装配后剪切强度、热导率的变化,并进行了温度冲击试验。测试结果表明,烧结样品剪切强度均符合标准要求,随着烧结温度的升高,纳米银胶热导率及剪切强度明显提升,且在最高温度200℃下烧结充分,并形成致密的烧结体。在温度冲击试验后烧结样品的剪切强度均有一定程度的下降,最高温度150℃和175℃烧结的纳米银胶烧结样品剪切强度下降超过40%,而最高温度200℃烧结的样品剪切强度只下降21.2%。考虑到功率模块的长期可靠性,纳米银胶推荐使用最高温度200℃烧结。

关键词：无压纳米银胶烧结钼铜载体铝合金外壳剪切强度热导率可靠性

Heading rate controller for unmanned helicopters based on modified ADRC

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Science China(Technological Sciences) 2023年第5期66卷 1255-1262页

作者： chen cheng YANG HuiXin College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China

A modified heading rate active disturbance rejection controller(ADRC)for miniature unmanned helicopters is presented to improve the transient performance and adaptability of working ***,a tail-locking mathematical model is introduced,and the amplification factor is ***,a standard ADRC controller is *** the amplification factor plays an important role in both parts of the content and is primarily influenced by the main rotor speed,an online forgetting factor recursive least square algorithm is used to identify it,and the identification result is condensed into a function of the main rotor speed,adapting to various working *** function is also included in the proposed ADRC controller to supplement the standard ***,experiments were conducted on a small electric helicopter.A reduction of approximately 40%in the transient time(compared with an off-the-shelf PID controller)was achieved in the *** comparative results show that the proposed ADRC scheme outperforms the classic PID and standard ADRC schemes in terms of transient performance and adaptability to working conditions.

关键词： heading rate controller ADRC model identification forgetting factor

Non-tensorial gravitational wave background in NANOGrav 12.5-year data set

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Science China(Physics,Mechanics & Astronomy) 2021年第12期64卷 84-89页

作者： Zu-cheng chen chen Yuan Qing-Guo Huang CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUCASHangzhou 310024China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We perform the first search for an isotropic non-tensorial gravitational-wave background(GWB) allowed in general metric theories of gravity in the North American Nanohertz Observatory for Gravitational Waves(NANOGrav) 12.5-year data set. By modeling the GWB as a power-law spectrum, we find strong Bayesian indication for a spatially correlated process with scalar transverse(ST) correlations whose Bayes factor versus the spatially uncorrelated common-spectrum process is 107 ± 7, but no statistically significant evidence for the tensor transverse, vector longitudinal, and scalar longitudinal polarization modes. The median and the 90% equal-tail amplitudes of ST mode are ■ , or equivalently the energy density parameter per logarithm frequency is ■, at frequency of 1/year.

关键词： gravitational wave scalar transverse polarization pulsar timing array

The evolutionary trajectory of the rural settlements in Southern Jiangsu in the past 20 years:From the perspective of urbanization and land use

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Journal of Geographical Sciences 2024年第8期34卷 1615-1635页

作者： chen Feiyu chen cheng Key Laboratory of Watershed Geographic Sciences Nanjing Institute of Geography and LimnologyCASNanjing 210008China Nanjing College University of Chinese Academy of SciencesNanjing 211135China

For a long time,due to lack of accurate data covering large areas,it is difficult to capture the continuous spatial evolutionary trajectory of rural settlements shaped by rapid urbanization and rural land use *** fill this gap,based on theoretical analysis this paper systemically detected the changing characteristics of scale,spatial morphology,distribution,and land use pattern of rural settlements in Southern Jiangsu in the past 20 years depending on the data of land resource survey in 2009 and *** study suggests that the total area and per capita size of rural settlements declined by 30%and 2%respectively as a result of rural land consolidation and the influx of enormous immigrants from underdeveloped *** spatial density and average shape index dropped by 14%and 44%respectively in the recent decade,indicating an evident trend of decentralization in spatial distribution,and regularization in the spatial ***,residential land within rural settlements decreased by 33%over the past decade while the land for industry and commercial service steadily increased,demonstrating that the function for manufacturing and diversified services had been *** the emerging issue of the aging population and new business opportunities in rural Southern Jiangsu,rural settlements regeneration might be the focus offutureresearch.

关键词： rural settlements spatial morphology land use Southern Jiangsu

Multiscale frictional behaviors of sp^(2) nanocrystallited carbon films with different ion irradiation densities

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Friction 2021年第5期9卷 1025-1037页

作者： Zelong HU Xue FAN cheng chen Institute of Nanosurface Science and Engineering Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics EngineeringCollege of Mechatronics and Control EngineeringShenzhen UniversityShenzhen 518060China

sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil current in an electron cyclotron resonance plasma sputtering *** multiscale frictional behaviors were investigated with macro pin‐on‐disk tribo‐tests and micro nanoscratch *** results revealed that,at an ion irradiation density of 16 mA/cm^(2),sp^(2) nanocrystallited carbon film exhibits the lowest friction coefficient and good wear resistant properties at both the macroscale and *** film sliding against a Si_(3)N_(4) ball under a contact pressure of 0.57 GPa exhibited a low friction coefficient of 0.09 and a long wear life at the ***,the film sliding against a diamond tip under a contact pressure of 4.9 GPa exhibited a stable low friction coefficient of 0.08 with a shallow scratch depth at the *** is suggested that sp^(2) nanocrystallites affect the frictional behaviors in the cases described *** the macroscale,the contact interface via the small real contact area and the sp^(2) nanocrystallited transfer layer dominated the frictional behavior,while the sp^(2) nanocrystallited structure in the film with low shear strength and high plastic resistivity,as well as the smooth surface morphology,decided the steady low nanoscratch properties at the *** findings expand multiscale tribological applications of sp^(2) nanocrystallited carbon films.

关键词： macro‐tribology micro‐tribology sp^(2)nanocrystallite carbon film ion irradiation density

Detecting coherence with respect to general quantum measurements

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Science China(Information Sciences) 2023年第8期66卷 52-60页

作者： Yu-cheng chen Jiong cheng Wen-Zhao ZHANG cheng-Jie ZHANG School of Physical Science and Technology Ningbo University State Key Laboratory of Precision Spectroscopy School of Physics and Electronic Science East China Normal University

Quantum coherence is crucial in quantum resource theory. Previous studies have mainly focused on standard coherence based on a complete orthogonal reference. Standard coherence has recently been extended to general positive-operator-valued measure(POVM)-based coherence, including block coherence as a special case. Therefore, it is necessary to construct block and POVM-based coherence witnesses to detect them. In this study, we present witnesses for block and POVM-based coherence and obtain the necessary and sufficient conditions for constructing these witnesses. We also discuss possible realizations of some block and POVM-based coherence witnesses in experiments and present examples of measuring block coherence witnesses based on real experimental data. Furthermore, we present an application of block coherence witnesses in a quantum-parameter estimation task with a degenerate Hamiltonian and estimate the unknown parameter by measuring the block coherence witnesses when the input state is block ***, we prove that the quantum Fisher information of any block-incoherent state equals zero, which coincides with the result obtained from measuring block coherence witnesses.

关键词： coherence witness general quantum measurements block coherence POVM-based coherence quantum coherence

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Efficient policy evaluation by matrix sketching

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Frontiers of Computer Science 2022年第5期16卷 97-105页

作者： cheng chen Weinan ZHANG Yong YU Department of Computer Science Shanghai Jiao Tong UniversityShanghai 200240China

In the reinforcement learning,policy evaluation aims to predict long-term values of a state under a certain *** high-dimensional representations become more and more common in the reinforcement learning,how to reduce the computational cost becomes a significant problem to the policy *** recent works focus on adopting matrix sketching methods to accelerate least-square temporal difference(TD)algorithms and quasi-Newton temporal difference *** these sketching methods,the truncated incremental SVD shows better performance because it is stable and ***,the convergence properties of the incremental SVD is still *** this paper,we first show that the conventional incremental SVD algorithms could have enormous approximation errors in the worst *** we propose a variant of incremental SVD with better theoretical guarantees by shrinking the singular values ***,we employ our improved incremental SVD to accelerate least-square TD and quasi-Newton TD *** experimental results verify the correctness and effectiveness of our methods.

关键词： temporal difference learning policy evaluation matrix sketching

Analysis of actuator delay and its effect on uncertainty quantification for real-time hybrid simulation

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Earthquake Engineering and Engineering Vibration 2017年第4期16卷 713-725页

作者： cheng chen Weijie Xu Tong Guo Kai chen School of Engineering San Francisco State University Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education Southeast University

Uncertainties in structure properties can result in different responses in hybrid simulations. Quantification of the effect of these tmcertainties would enable researchers to estimate the variances of structural responses observed from experiments. This poses challenges for real-time hybrid simulation （RTHS） due to the existence of actuator delay. Polynomial chaos expansion （PCE） projects the model outputs on a basis of orthogonal stochastic polynomials to account for influences of model uncertainties. In this paper, PCE is utilized to evaluate effect of actuator delay on the maximum displacement from real-time hybrid simulation of a single degree of freedom （SDOF） structure when accounting for uncertainties in structural properties. The PCE is first applied for RTHS without delay to determine the order of PCE, the number of sample points as well as the method for coefficients calculation. The PCE is then applied to RTHS with actuator delay. The mean, variance and Sobol indices are compared and discussed to evaluate the effects of actuator delay on uncertainty quantification for RTHS. Results show that the mean and the variance of the maximum displacement increase linearly and exponentially with respect to actuator delay, respectively. Sensitivity analysis through Sobol indices also indicates the influence of the single random variable decreases while the coupling effect increases with the increase of actuator delay.

关键词： real-time hybrid simulation actuator delay polynomial chaos expansion delay differential equation uncertainty quantification

L^p estimates for Riesz transform and their commutators associated with Schr?dinger type operator

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Applied Mathematics(A Journal of Chinese Universities) 2016年第1期31卷 112-126页

作者： chen Xiao-li chen Jie-cheng Department of Mathematics Jiangxi Normal University Nanchang 330022 China Department of Mathematics Zhejiang Normal University Jinhua 321004 China

. Let H2 = （-△）2 ＋ V2 be the Schr6dinger type operator, where V satisfies reverse HSlder inequality. In this paper, we establish the Lp boundedness for V2 H2- 1, H21 V2, VH2- 1/2 and Hfl/2V, and that of their comm... 详细信息

关键词： Schrodinger type operator Bq class BMOL commutator.