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1. 3D Model of Terahertz Photoconductive Antenna using COMSOL Multiphysics

   Batista, J.S.; El-Shenawee, M. (December 2021, Antennas and Propagation Society International Symposium)

   This paper presents a 3D model of a photoconductive antenna (PCA) on semiconductor substrate. The simulations were conducted using the COMSOL Multiphysics package. The model considers the laser excitation and the carrier generation acceleration in the semiconductor layer. The computational work was achieved using the frequency-domain RF module and the semiconductor module. The results demonstrate that simulating the active area alone produces sufficient accuracy ~ 0.01% in the RF module solution (solution of the electric and magnetic fields) and ~ 0.23% in the semiconductor solution (photocurrent solution). The reduction in the simulated area helps minimizing the required CPU time and memory requirement in the 3D model at THz frequencies. The largest case in this study was simulated at the National XSEDE Supercomputing with ~ 0.3 billion unknowns and memory requirement of ~ 3.2TB in the RF module. 

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2. Challenges to the Reforestation Pipeline in the United States

   https://doi.org/10.3389/ffgc.2021.629198  

   Fargione, Joseph; Haase, Diane L.; Burney, Owen T.; Kildisheva, Olga A.; Edge, Greg; Cook-Patton, Susan C.; Chapman, Teresa; Rempel, Austin; Hurteau, Matthew D.; Davis, Kimberley T.; et al (February 2021, Frontiers in Forests and Global Change)

   null (Ed.)

   Large-scale global reforestation goals have been proposed to help mitigate climate change and provide other ecosystem services. To explore reforestation potential in the United States, we used GIS analyses, surveys of nursery managers and foresters, and literature synthesis to assess the opportunities and challenges associated with meeting proposed reforestation goals. We considered a scenario where 26 million hectares (64 million acres) of natural and agricultural lands are reforested by 2040 with 30 billion trees at an estimated cost of $33 ($24–$53) billion USD. Cost per hectare will vary by region, site conditions, and other factors. This scenario would require increasing the number of tree seedlings produced each year by 1.7 billion, a 2.3-fold increase over current nursery production levels. Additional investment (not included in the reforestation cost estimate) will be needed to expand capacity for seed collection, seedling production, workforce development, and improvements in pre- and post-planting practices. Achieving this scenario will require public support for investing in these activities and incentives for landowners. 

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3. WIP: Introducing Semiconductors in a High School Calculus Class: A Pilot Implementation

   https://doi.org/10.1109/FIE61694.2024.10893203  

   Mehraban, Haniye; Ash, Andrew; Dyke, Erin; Hu, John (October 2024, IEEE)

   This work-in-progress research-to-practice paper presents the development and pilot implementation of curriculum that introduces semiconductor contents in a high school calculus class. The demand for chips soared through the COVID-19 pandemic, exposing our country's semiconductor manufacturing and supply chain risks. The need to reassert US semiconductor leadership will require training a well-educated workforce, starting at the K-12 level. Meanwhile, K-12 STEM teachers often juggle the conflicting requirements of standardized tests and the need to cultivate 21st-century skills, deeper learning, and transferable knowledge, among others. This paper presents a pilot implementation that could address both problems. Selected teachers attended an NSF-funded Research Experience for Teachers (RET) summer program to learn about chip design basics. They also received curriculum development support to design new modules on semiconductor topics that would attract their students' interests. 

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4. Reconfigurable mixed-kernel heterojunction transistors for personalized support vector machine classification

   https://doi.org/10.1038/s41928-023-01042-7  

   Yan, Xiaodong; Qian, Justin H; Ma, Jiahui; Zhang, Aoyang; Liu, Stephanie E; Bland, Matthew P; Liu, Kevin J; Wang, Xuechun; Sangwan, Vinod K; Wang, Han; et al (November 2023, Nature Electronics)

   Advances in algorithms and low-power computing hardware imply that machine learning is of potential use in off-grid medical data classification and diagnosis applications such as electrocardiogram interpretation. However, although support vector machine algorithms for electrocardiogram classification show high classification accuracy, hardware implementations for edge applications are impractical due to the complexity and substantial power consumption needed for kernel optimization when using conventional complementary metal–oxide–semiconductor circuits. Here we report reconfigurable mixed-kernel transistors based on dual-gated van der Waals heterojunctions that can generate fully tunable individual and mixed Gaussian and sigmoid functions for analogue support vector machine kernel applications. We show that the heterojunction-generated kernels can be used for arrhythmia detection from electrocardiogram signals with high classification accuracy compared with standard radial basis function kernels. The reconfigurable nature of mixed-kernel heterojunction transistors also allows for personalized detection using Bayesian optimization. A single mixed-kernel heterojunction device can generate the equivalent transfer function of a complementary metal–oxide–semiconductor circuit comprising dozens of transistors and thus provides a low-power approach for support vector machine classification applications. 

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5. Kinetic analysis of the growth behavior of perovskite CsPbBr ₃ nanocrystals in a microfluidic system

   https://doi.org/10.1039/D2LC00331G  

   Tang, Xiaobing; Yang, Fuqian (July 2022, Lab on a Chip)

   Understanding the growth behavior of nanoparticles and semiconductor nanocrystals under dynamic environments is of profound importance in controlling the sizes and uniformity of the prepared nanoparticles and semiconductor nanocrystals. In this work, we develop a relation between the bandgap (the photoluminescence peak wavelength) of semiconductor nanocrystals and the total flow rate for the synthesis of semiconductor nanocrystals in microfluidic systems under the framework of the quantum confinement effect without the contribution of Coulomb interaction. Using this relation, we analyze the growth behavior of CsPbBr 3 nanocrystals synthesized in a microfluidic system by an antisolvent method in the temperature range of 303 to 363 K. The results demonstrate that the square of the average size of the CsPbBr 3 nanocrystals is inversely proportional to the total flow rate and support the developed relation. The activation energy for the rate process controlling the growth of the CsPbBr 3 nanocrystals in the microfluidic system is 2.05 kJ mol −1 . Increasing the synthesis temperature widens the size distribution of the CsPbBr 3 NCs prepared in the microfluidic system. The method developed in this work provides a simple approach to use photoluminescent characteristics to in situ monitor and analyze the growth of semiconductor nanocrystals under dynamic environments. 

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