A Two-Stage 2D Channel Extrapolation Scheme for TDD 5G NR Systems

Recently, channel extrapolation has been widely investigated in frequency division duplex (FDD) massive MIMO systems. However, in time division duplex (TDD) fifth generation (5G) new radio (NR) systems, the channel extrapolation problem also arises due to the hopping uplink pilot pattern, which has not been fully researched yet. This paper addresses this gap by formulating a channel extrapolation problem in TDD massive MIMO-OFDM systems for 5G NR, incorporating imperfection factors. A novel two-stage two-dimensional (2D) channel extrapolation scheme in both frequency and time domain is proposed, designed to mitigate the negative effects of imperfection factors and ensure high-accuracy channel estimation. Specifically, in the channel estimation stage, we propose a novel multi-band and multi-timeslot based high-resolution parameter estimation algorithm to achieve 2D channel extrapolation in the presence of imperfection factors. Then, to avoid repeated multi-timeslot based channel estimation, a channel tracking stage is designed during the subsequent time instants, in which a sparse Markov channel model is formulated to capture the dynamic sparsity of massive MIMO-OFDM channels under the influence of imperfection factors. Next, an expectation-maximization (EM) based compressive channel tracking algorithm is designed to jointly estimate unknown imperfection and channel parameters by exploiting the high-resolution prior information of the delay/angle parameters from the previous timeslots. Simulation results underscore the superior performance of our proposed channel extrapolation scheme over baselines

Organometallic complexes featuring oligo-phenylene ethnylene ligands

This thesis describes the synthesis and analysis of organometallic complexes that feature oligo-phenylene ethynylene based ligands. Chapter 1 introduces the general topic of molecular electronics and provides a general overview of the interest in phenylene ethynylene systems as foundation architectures for molecular wires. The role of metal complexes in molecular electronics and the application of the cluster - surface analogy to the study of model systems is also described. Chapter 2 describes the synthesis of oligo-phenylene ethynylene pro-ligands of the general form Мe(_3)SіС≡СС(_6)H(_4)C≡СС(_6)H(_4) (1-5), in which R is either an electron donor (Me, OMe) or acceptor (СО(_2)Ме, NO(_2), CN). The compounds were synthesised either via Sonogashira Pd/Cu cross-coupling reactions or via the nucleophilic attack of benzoquinones by lithiated acetylide anions and subsequent reduction. The desilylation of these compounds afforded the terminal alkynes НС≡СС(_6)Н(_4)С≡СС(_6)Н(_4)R (6-10). Furthermore, the extended "three-ring" 1,4- bis(phenyl ethynylbenzene) derivatives Мe(_3)SіС≡СС(_6)Н(_4)С≡СС(_6)Н(_4) ≡C(_6)H(_4)С≡СSiMe(_3), 11 and Мe(_3)SіС≡СС(_6)Н(_4)С≡СС(ОМе)(_2)(Н)(_2)С≡С(_6)Н(_4)С≡CSiMe(_3), 13 and the terminal alkyne НС≡СС(_6)Н(_4)С≡СС(OMe)(_2)(H)(_2)C≡ C(_6)(h)(_4)C≡CH (14) have also been prepared. These compounds were fully spectroscopically characterised and in the case of 14 the molecular structure analysis is discussed. Chapter 3 discusses the synthesis of the gold(I) oligo-phenylene ethynylene complexes The complexes were prepared by treating the ligands precursors 1-5 with АuСl(Рl(_3)) (L = Ph or Су) in the presence of NaOMe to afford complexes Аu(С≡СС(_6)Н(_4)С≡СС(_6)Н(_4)R)PPh(_3) [R = Me (15), OMe (16), СО(_2)Me (17), NO(_2) (18) and CN (19) and Аu(С≡СС(_6)Н(_4)С≡СС(_6)Н(_4)R)PCy(_3) [R = Me (20), OMe (21) and NO(_2) (22)]. The "three-ring" complexes {Аu(РРh(_3))}2(μ-С≡СС(_6)H(_4)С≡СС(_6)Н(_4)С=С(_6)Н(_4)С≡С), 23 and {Аu(РРh(_3)}(_2)( μ-C≡CC(_6)H(_4)C≡CC(_6)(OMe)(_2)H(_2)C≡C(_6)H(_4)C≡C 24 were also prepared. These complexes were spectroscopically characterised and molecular structural analyses reveal intermolecular interactions between the phenylene ethynylene portion of the molecules in the solid state, but not aurophilic interactions. Chapter 4 examines the synthesis of half-sandwich Ru(L(_2))Cp' [L = РРh(_3), Cp' = Cp ; L(_2) = dppe, Cp' = Cp*) acetylide complexes derived from simple phenyl, tolan and oligo(phenylene ethynylene) based acetylenes. The electrochemical properties of these complexes have been explored, as have some of the molecular structural details. Chapter 5 describes the synthesis of some cluster complexes. The gold acetylide complexes Аu(С≡СС(_6)Н(_4)С≡СС(_6)Н(_4)R)(РРh(_3)) react readily with Ru(_3)(CO)(_10)(μ-dppm) to afford phenylene ethynylene derivatives Ru(_3)(μ-АuРРh(_3))(μ-С(_2)С(_6)Н(_4)С≡СС(_6)Н(_4)-R)(μ-dppm)(C0)(_7) (38-42) in which the conjugated organic moiety is "end-capped" by the cluster and an R group that is either electron donating or withdrawing (R = Me, OMe, СО(_2) Мe, NO(_2), CN). The clusters 38-42 are linked to the hydrido clusters Ru(_3)(μ-Н)(μ-С(_2)С(_6)Н(_4)С≡СС(_6)Н(_4)R)(СО)(_7) (36 and 37) through the well-known isolobal relationship between H and Аu(РR(_3)). In addition, the bis-cluster {Ru(_3)(μ-dppm)(CO)(_7)}(_2){(μ-ΑuΡΡh(_3))}(_2)(μ-C(_2)C(_6)H(_4)C≡CC(_6)H(_4)C≡CC(_6)H(_4)C(_2)) (43) has also been prepared. All the clusters reported in this chapter were crystallographically determined. Structural, spectroscopic, photophysical and electrochemical studies were conducted and have revealed little electronic interaction between the remote substituent and the organometallic end-caps. Chapter 6 explores the novel, preparative scale stoichiometric transmetallation reactions involving the simple Аu(С≡СR)(РРh(_3)) (R = Ph or С(_6)Н(_4)Мe) complexes. These gold(I) complexes have been treated with several inorganic and organometallic compounds MXL(_n) [M = metal, L(_n) = supporting ligands, X = halide], to afforded the corresponding metal-acetylide complexes M(C≡CR)L(_n), with representative examples featuring metals from Groups 8-11. The acetylide products were fully characterised by usual spectroscopic methods including the molecular structural analysis. Chapter 7 concludes the general summary of the thesis and discusses briefly the findings achieved in each chapter and the vital role of oligo-phenyelene ethynylenes ligands in the construction of numerous organometallic complexes which show interesting and promising properties for the molecular wires development. In addition, further future work is also proposed on other systems that feature this ligands

Go Beyond Black-box Policies: Rethinking the Design of Learning Agent for Interpretable and Verifiable HVAC Control

Recent research has shown the potential of Model-based Reinforcement Learning (MBRL) to enhance energy efficiency of Heating, Ventilation, and Air Conditioning (HVAC) systems. However, existing methods rely on black-box thermal dynamics models and stochastic optimizers, lacking reliability guarantees and posing risks to occupant health. In this work, we overcome the reliability bottleneck by redesigning HVAC controllers using decision trees extracted from existing thermal dynamics models and historical data. Our decision tree-based policies are deterministic, verifiable, interpretable, and more energy-efficient than current MBRL methods. First, we introduce a novel verification criterion for RL agents in HVAC control based on domain knowledge. Second, we develop a policy extraction procedure that produces a verifiable decision tree policy. We found that the high dimensionality of the thermal dynamics model input hinders the efficiency of policy extraction. To tackle the dimensionality challenge, we leverage importance sampling conditioned on historical data distributions, significantly improving policy extraction efficiency. Lastly, we present an offline verification algorithm that guarantees the reliability of a control policy. Extensive experiments show that our method saves 68.4% more energy and increases human comfort gain by 14.8% compared to the state-of-the-art method, in addition to an 1127x reduction in computation overhead. Our code and data are available at https://github.com/ryeii/Veri_HVACComment: Accepted for the 61st Design Automation Conference (DAC

Nutrient deprivation induces the Warburg effect through ROS/AMPK-dependent activation of pyruvate dehydrogenase kinase

AbstractThe Warburg effect is known to be crucial for cancer cells to acquire energy. Nutrient deficiencies are an important phenomenon in solid tumors, but the effect on cancer cell metabolism is not yet clear. In this study, we demonstrate that starvation of HeLa cells by incubation with Hank's buffered salt solution (HBSS) induced cell apoptosis, which was accompanied by the induction of reactive oxygen species (ROS) production and AMP-activated protein kinase (AMPK) phosphorylation. Notably, HBSS starvation increased lactate production, cytoplasmic pyruvate content and decreased oxygen consumption, but failed to change the lactate dehydrogenase (LDH) activity or the glucose uptake. We found that HBSS starvation rapidly induced pyruvate dehydrogenase kinase (PDK) activation and pyruvate dehydrogenase (PDH) phosphorylation, both of which were inhibited by compound C (an AMPK inhibitor), NAC (a ROS scavenger), and the dominant negative mutant of AMPK. Our data further revealed the involvement of ROS production in AMPK activation. Moreover, DCA (a PDK inhibitor), NAC, and compound C all significantly decreased HBSS starvation-induced lactate production accompanied by enhancement of HBSS starvation-induced cell apoptosis. Not only in HeLa cells, HBSS-induced lactate production and PDH phosphorylation were also observed in CL1.5, A431 and human umbilical vein endothelial cells. Taken together, we for the first time demonstrated that a low-nutrient condition drives cancer cells to utilize glycolysis to produce ATP, and this increases the Warburg effect through a novel mechanism involving ROS/AMPK-dependent activation of PDK. Such an event contributes to protecting cells from apoptosis upon nutrient deprivation