Understanding the mechanisms of efficient and robust energy transfer in light-harvesting systems provides new insights for the optimal design of artificial systems. In this paper, we use the Fenna-Matthews-Olson (FMO) protein complex and phycocyanin 645 (PC 645) to explore the general dependence on physical parameters that help maximize the efficiency and maintain its stability. With the Haken-Strobl model, the maximal energy transfer efficiency (ETE) is achieved under an intermediate optimal value of dephasing rate. To avoid the infinite temperature assumption in the Haken-Strobl model and the failure of the Redfield equation in predicting the Forster rate behavior, we use the generalized Bloch-Redfield (GBR) equation approach to correctly describe dissipative exciton dynamics and find that maximal ETE can be achieved under various physical conditions, including temperature, reorganization energy, and spatial-temporal correlations in noise. We also identify regimes of reorganization energy where the ETE changes monotonically with temperature or spatial correlation and therefore cannot be optimized with respect to these two variables.Photosynthetic processes in plants, bacteria and marine algae provide key insights into designing artificial light harvesting systems that operate efficiently and robustly [1, 2]. The initial stages in the conversion of solar energy into chemical and other useful forms of energy for human consumption can be described by exciton dynamics with trapping and dissipation [3,4]. Recent experimental and computational studies suggest that environmental noise can assist exciton transport and can be optimized for maximal energy transfer efficiency (ETE) [5]- [20]. Quantum entanglement in photosynthetic light-harvesting complexes has also been studied with the consideration of environmental noise [21]. In this paper, using two light-harvesting systems, FMO and PC 645, we examine the optimization of the ETE, with respect to reorganization energy, temperature, and spatial-temporal correlations.This paper closely follows the theoretical formulation presented in a recent review [17] and further examines issues relevant for realistic light-harvesting systems. The review article addresses two questions: basic mechanisms of optimal energy transfer and systematic mapping to kinetic networks. Since environmental noise helps maximize energy transfer efficiency, it stands to reason that light-harvesting systems can be optimized to achieve best performance under a given environment, which leads to the proposal of optimal design. Previous work on simple models [10,17] and FMO [13]-[16] use the Haken-Strobl model, an infinite temperature model, and therefore report optimization a function of single parameter, the pure dephasing rate.It remains an open question if the ETE can be optimized as a function of temperature, reorganization energy, bath correlation time, and spatial correlation. In this paper, we will further examine the idea of noise-enhanced optimal energy transfer with explicit considerations of d...

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In this paper, we propose a beamforming design for dualfunctional radar-communication (DFRC) systems at the millimeter wave (mmWave) band, where hybrid beamforming and sub-arrayed MIMO radar techniques are jointly exploited. We assume that a base station (BS) is serving a user equipment (UE) located in a Non-Line-of-Sight (NLoS) channel, which in the meantime actively detects multiple targets located in a Line-of-Sight (LoS) channel. Given the optimal communication beamformer and the desired radar beampattern, we propose to design the analog and digital beamformers under non-convex constant-modulus (CM) and power constraints, such that the weighted summation of the communication and radar beamforming errors is minimized. The formulated optimization problem can be decomposed into three subproblems, and is solved by the alternating minimization approach. Numerical simulations verify the feasibility of the proposed beamforming design, and show that our approach offers a favorable performance tradeoff between sensing and communication.

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SUMMARYTo verify the importance of the non-stationary frequency characteristic of seismic ground motion, a joint time-frequency analysis technique of time signals, called chirplet-based signal approximation, is developed to extract the non-stationary frequency information from the recorded data. The chirplet-based signal approximation is clear in concept, similar to Fourier Transform in mathematical expressions but with di erent base functions. Case studies show that the chirplet-based signal approximation can represent the joint time-frequency variation of seismic ground motion quite well. Both the random models of uniform modulating process and evolutionary process are employed to generate artiÿcial seismic waves. The joint time-frequency modulating function in the random model of evolutionary process is determined by chirplet-based signal approximation. Finally, non-linear response analysis of a SODF system and a frame structure is performed based on the generated artiÿcial seismic waves. The results show that the non-stationary frequency characteristic of seismic ground motion can signiÿcantly change the non-linear response characteristics of structures, particularly when a structure goes into collapse phase under seismic action. It is concluded that non-stationary frequency characteristic of seismic ground motion should be considered for the assessment of seismic capacity of structures.