Electromagnetic Property Sensing: A New Paradigm of Integrated Sensing and Communication

Integrated sensing and communication (ISAC) has opened up numerous game-changing opportunities for future wireless systems. In this paper, we develop a novel scheme that utilizes orthogonal frequency division multiplexing (OFDM) pilot signals in ISAC systems to sense the electromagnetic (EM) property of the target and thus also identify the material of the target. Specifically, we first establish an end-to-end EM propagation model by means of Maxwell equations, where the EM property of the target is captured by a closed-form expression of the ISAC channel, incorporating the Lippmann-Schwinger equation and the method of moments (MOM) for discretization. We then model the relative permittivity and conductivity distribution (RPCD) within a specified detection region. Based on the sensing model, we introduce a multi-frequency-based EM property sensing method by which the RPCD can be reconstructed from compressive sensing techniques that exploits the joint sparsity structure of the EM property vector. To improve the sensing accuracy, we design a beamforming strategy from the communications transmitter based on the Born approximation that can minimize the mutual coherence of the sensing matrix. The optimization problem is cast in terms of the Gram matrix and is solved iteratively to obtain the optimal beamforming matrix. Simulation results demonstrate the efficacy of the proposed method in achieving high-quality RPCD reconstruction and accurate material classification. Furthermore, improvements in RPCD reconstruction quality and material classification accuracy are observed with increased signal-to-noise ratio (SNR) or reduced target-transmitter distance

Electrochemically driven phase transformation in energy storage compounds

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 124-132).Nanoscale lithium transition metal phosphate olivines have become commercially important as positive electrode materials in a new generation of lithium-ion batteries. Not surprisingly, many energy storage compounds undergo phase transitions in-situ, including the production of metastable phases. Unique to this environment is the frequent application of electrical over- and underpotentials, which are the electrical analogs to undercooling and superheating. So far, overpotential effects on phase stability and transformation mechanisms have not been studied in detail. Here we use synchrotron X-ray diffraction performed in-situ during potentiostatic and galvanostatic cycling, combined with phase-field modeling, to reveal a remarkable dependence of phase transition pathways on overpotential in the model olivine Lii. ,FePO 4. For a sample of particle size -113 nm, at both low (e.g., 75 mV) overpotentials, a crystal-to-crystal olivine transformation is preferred, whereas at intermediate overpotentials a crystalline-to-amorphous phase transition dominates. As particle sizes decrease to the nanoscale, amorphization is further emphasized. Moreover, in the LiipxFei. yMnyPO 4 (y=0. 1, 0.4) system, the phase transition behavior is ovepotential dependent, and the crystallization of the amorphous phase is overpotential driven. An extensive nonequilibrium solid solution has been observed upon galvanostatic discharge. The misfit strain between two end members determines the reaction type as well as the phase transformation rate. High rate capability is expected in Lii.xFe1.yMnyPO 4 when the misfit is adequately tuned by Mn content. In addition, the discrepancy in phase compositions between dynamic and equilibrium states can be resolved by inter-crystallite ion diffusion among phases, e.g. ion diffusion between amorphous and crystalline phases.by Yu-Hua Kao.Ph.D

miR-212/132-Enriched Extracellular Vesicles Promote Differentiation of Induced Pluripotent Stem Cells Into Pancreatic Beta Cells

Pancreatic beta cell transplantation is the ideal method for treatment of type 1 diabetes mellitus (T1DM), and the generation of beta cells from induced pluripotent stem cells (iPSCs) of patients is a promising strategy. In this study, we improved a previous strategy to produce beta cells using extracellular vesicles (EVs) derived from mature beta cells and differentiated beta cells from iPSCs (i-Beta cells), which secreted insulin under glucose stimulation in vitro and ameliorated hyperglycemia in vivo. Mechanistic analyses revealed that EV-carried microRNA (miR)-212/132 (EV-miR-212/132) directly bound to the 3′ UTR of FBW7 to prevent its translation and FBW7 combined with NGN3 to accelerate its proteasomal degradation. EV-miR-212/132 stabilized NGN3 expression to promote differentiation of endocrine cells from induced iPSCs. Moreover, NGN3 bound to PDX1 to enhance transcription of endogenous miR-212/132 and formed a positive regulatory circuit that maintained the functions of mature pancreatic beta cells.ConclusionThis study describes a novel approach for beta cell production and supports the use of iPSCs for cell replacement therapy of T1DM

Application of integrated formation evaluation and three-dimensional modeling in shale gas prospect identification

Identifying the shale gas prospect is crucial for gas extraction from suchreservoirs. Junggar Basin (in Northwest China) is widely considered tohave high potential as a shale gas resource, and the Jurassic, the mostsignificant gas source strata, is considered as prospective for shale gasexploration and development. This study evaluated the Lower JurassicBadaowan Formation shale gas potential combined with geochemical,geological, and well logging data, and built a three-dimensional (3D)model to exhibit favorable shale gas prospects. In addition, methane sorption capacity was tested for verifying the prospects. The Badaowan shalehad an average total organic carbon (TOC) content of 1.30 wt. % andvitrinite reflectance (Ro) ranging from 0.47% to 0.81% with dominatedtype III organic matter (OM). X-ray diffraction (XRD) analyses showedthat mineral composition of Badaowan shale was fairly homogeneous anddominated by clay and brittle minerals. 67 wells were used to identifyprospective shale intervals and to delineate the area of prospects. Consequently, three Badaowan shale gas prospects in the Junggar Basin wereidentified: the northwestern margin prospect, eastern Central Depressionprospect and Wulungu Depression prospect. The middle interval of thenorthwestern margin prospect was considered to be the most favorableexploration target benefitted by wide distribution and high lateral continuity. Generally, methane sorption capacity of the Badaowan shale wascomparable to that of the typical gas shales with similar TOC content,showing a feasible gas potential

Two-stage Sampling on Additive Model for Quantitative Sensitive Question Survey and Its Application

Objective To explore scientific sampling methods and corresponding formulas for quantitative sensitive question survey on two-stage random sampling. To provide scientific data for the prevention and control of high risk AIDS population in Beijing. Methods Additive model for quantitative sensitive question survey, two-stage random sampling, properties of variance and mean were used. Results Formulas for the esti¬mation of the population proportions and its variance on additive model for quantitative sensitive question survey were deduced. The survey methods and formulas were employed successfully in the survey of the age of the first time when MSM having sex with men and the result was 21.9747. Conclusion The methods and corresponding formulas for two-stage sampling on additive model for quantitative sensitive question survey are feasible. Key words: Sensitive questions; Additive model for randomized response technique; Two-stage sampling; MS