Adaptive Extended State Observer for the Dual Active Bridge Converters.

The DC-DC dual active bridge (DAB) converter has become one of the essential units for bidirectional energy distribution and connecting various renewable energy sources. When it comes to regulating the converter's output voltage, integrating an extended state observer (ESO) offers the advantage of eliminating the need for a current sensor, thereby reducing system costs. The ESO with a high observer bandwidth tends to acquire a faster system convergence and greater tracking accuracy. However, its disturbance suppression performance will become poor compared to the ESO with a low observer bandwidth. Based on this, the adaptive ESO (AESO) is proposed in this study to make a compromise between tracking performance and disturbance suppression. When the system is subjected to a high voltage error, the observer bandwidth will increase to improve the tracking performance and decrease to enhance the disturbance suppression. In order to demonstrate that the proposed method is effective, it is compared to the ESO with a fixed observer bandwidth and the improved model-based phase-shift control (MPSC). These comparisons are made through simulation and experimental results in various operation scenarios.

Simulation of a randomly percolated CNT network for an improved analog physical unclonable function.

Carbon nanotube networks (CNTs)-based devices are well suited for the physically unclonable function (PUF) due to the inherent randomness of the CNT network, but CNT networks can vary significantly during manufacturing due to various controllable process conditions, which have a significant impact on PUF performance. Therefore, optimization of process conditions is essential to have a PUF with excellent performance. However, because it is time-consuming and costly to fabricate directly under various conditions, we implement randomly formed CNT network using simulation and confirm the variable correlation of the CNT network optimized for PUF performance. At the same time, by implementing an analog PUF through simulation, we present a 2D patterned PUF that has excellent security and can compensate for error occurrence problems. To evaluate the performance of analog PUF, a new evaluation method different from the existing digital PUF is proposed, and the PUF performance is compared according to two process variables, CNT density and metallic CNT ratio, and the correlation with PUF performance is confirmed. This study can serve as a basis for research to produce optimized CNT PUF by applying simulation according to the needs of the process of forming a CNT network.

DRAC 2022: A public benchmark for diabetic retinopathy analysis on ultra-wide optical coherence tomography angiography images.

We described a challenge named "DRAC - Diabetic Retinopathy Analysis Challenge" in conjunction with the 25th International Conference on Medical Image Computing and Computer Assisted Intervention (MICCAI 2022). Within this challenge, we provided the DRAC datset, an ultra-wide optical coherence tomography angiography (UW-OCTA) dataset (1,103 images), addressing three primary clinical tasks: diabetic retinopathy (DR) lesion segmentation, image quality assessment, and DR grading. The scientific community responded positively to the challenge, with 11, 12, and 13 teams submitting different solutions for these three tasks, respectively. This paper presents a concise summary and analysis of the top-performing solutions and results across all challenge tasks. These solutions could provide practical guidance for developing accurate classification and segmentation models for image quality assessment and DR diagnosis using UW-OCTA images, potentially improving the diagnostic capabilities of healthcare professionals. The dataset has been released to support the development of computer-aided diagnostic systems for DR evaluation.

Gate Capacitance Coupling of Double-Gate Carbon Nanotube Network Transistors.

Carbon nanotube (CNT) network channels constructed using a high-purity CNT solution for use in CNT thin-film transistors have the advantages of the possibility of requiring a low-temperature process and needing no special equipment. However, there are empty spaces between individual CNTs, resulting in unexpected effects. In this study, double-gate (DG) CNT network transistors were fabricated and measured in four different configurations to observe the capacitive coupling effects between the top gate (TG) and bottom gate (BG) in the DG structure. As a result, the electrical characteristics measured with the BG with a thicker gate oxide while floating the TG were similar to those measured with the TG with a thinner gate oxide. A comparison of the measured transfer curves showed that TG and BG were strongly coupled through the empty spaces in the channels. In addition, we evaluated the capacitance coupling effect due to changes in the CNT density, which is closely related to the empty space of the network channel. Finally, we proposed a method to determine the effective gate capacitance by considering the empty spaces between CNTs, which enabled the accurate evaluation of mobility. The effects of these materials were demonstrated by fabricating transistors using Al2O3, HfO2, and ZrO2 as TG oxide materials. By focusing on considerations based on the properties of CNT materials, our study provides valuable insights into accurate electrical modeling and potential advancements in CNT-based devices.

Design Rule of Electron- and Hole-Selective Contacts for Polycrystalline Silicon-Based Passivating Contact Solar Cells.

A crystalline silicon (c-Si) solar cell with a polycrystalline silicon/SiOx (poly-Si/SiOx) structure, incorporating both electron and hole contacts, is an attractive choice for achieving ideal carrier selectivity and serving as a fundamental component in high-efficiency perovskite/Si tandem and interdigitated back-contact solar cells. However, our understanding of the carrier transport mechanism of hole contacts remains limited owing to insufficient studies dedicated to its investigation. There is also a lack of comparative studies on the poly-Si/SiOx electron and hole contacts for ideal carrier-selective solar cells. Therefore, this study aims to address these knowledge gaps by exploring the relationship among microstructural evolution, dopant in-diffusion, and the resulting carrier transport mechanism in both the electron and hole contacts of poly-Si/SiOx solar cells. Electron (n+ poly-Si/SiOx/substrate)- and hole (p+ poly-Si/SiOx/substrate)-selective passivating contacts are subjected to thermal annealing. Changes in the passivation properties and carrier transport mechanisms of these contacts are investigated during thermal annealing at various temperatures. Notably, the results demonstrate that the passivation properties and carrier transport mechanisms are strongly influenced by the microstructural evolution of the poly-Si/SiOx layer stack and dopant in-diffusion. Furthermore, electron and hole contacts exhibit common behaviors regarding microstructural evolution and dopant in-diffusion. However, the hole contacts exhibit relatively inferior electrical properties overall, mainly because both the SiOx interface and the p+ poly-Si are found to be highly defective. Moreover, boron in the hole contacts diffuses deeper than phosphorus in the electron contacts, resulting in deteriorated carrier collection. The experimental results are also supported by device simulation. Based on these findings, design rules are suggested for both electron and hole contacts, such as using thicker SiOx and/or annealing the solar cell at a temperature not exceeding the critical annealing temperature of the hole contacts.

Wafer-scale striped network transistors based on purified semiconducting carbon nanotubes for commercialization.

Highly purified and solution-processed semiconducting carbon nanotubes (s-CNTs) have developed rapidly over the past several decades and are near-commercially available materials that can replace silicon due to its large-area substrate deposition and room-temperature processing compatibility. However, the more s-CNTs are purified, the better their electrical performance, but considerable effort and long centrifugation time are required, which can limit commercialization due to high manufacturing costs. In this work, we therefore fabricated 'striped' CNT network transistor across industry-standard 8 inch wafers. The stripe-structured channel is effective in lowering the manufacturing cost because it can maintain good device performance without requiring high-purity s-CNTs. We evaluated the electrical performances and their uniformity by demonstrating striped CNT network transistors fabricating from various s-CNT solutions (e.g. 99%, 95%, and 90%) in 8 inch wafers. From our results, we concluded that by optimizing the CNT network configurations, CNTs can be sufficiently utilized for commercialization technology even at low semiconducting purity. Our approach can serve as a critical foundation for future low-cost commercial CNT electronics.

Robust Adaptive Control Strategy for a Bidirectional DC-DC Converter Based on Extremum Seeking and Sliding Mode Control.

This paper presents a new control strategy that combines classical control and an optimization scheme to regulate the output voltage of the bidirectional converter under the presence of matched and mismatched disturbances. In detail, a control-oriented modeling method is presented first to capture the system dynamics in a common canonical form, allowing different disturbances to be considered. To estimate and compensate for unknown disturbances, an extended state observer (ESO)-based continuous sliding mode control is then proposed, which can guarantee high tracking precision, fast disturbance rejection, and chattering reduction. Next, an extremum seeking (ES)-based adaptive scheme is introduced to ensure system robustness as well as optimal control effort under different working scenarios. Finally, comparative simulations with classical proportional-integral-derivative (PID) control and constant switching gains are conducted to verify the effectiveness of the proposed adaptive control methodology through three case studies of load resistance variations, buck/boost mode switching, and input voltage variation.

Tunable image quality control of 3-D ultrasound using switchable CycleGAN.

In contrast to 2-D ultrasound (US) for uniaxial plane imaging, a 3-D US imaging system can visualize a volume along three axial planes. This allows for a full view of the anatomy, which is useful for gynecological (GYN) and obstetrical (OB) applications. Unfortunately, the 3-D US has an inherent limitation in resolution compared to the 2-D US. In the case of 3-D US with a 3-D mechanical probe, for example, the image quality is comparable along the beam direction, but significant deterioration in image quality is often observed in the other two axial image planes. To address this, here we propose a novel unsupervised deep learning approach to improve 3-D US image quality. In particular, using unmatched high-quality 2-D US images as a reference, we trained a recently proposed switchable CycleGAN architecture so that every mapping plane in 3-D US can learn the image quality of 2-D US images. Thanks to the switchable architecture, our network can also provide real-time control of image enhancement level based on user preference, which is ideal for a user-centric scanner setup. Extensive experiments with clinical evaluation confirm that our method offers significantly improved image quality as well user-friendly flexibility.

Reprogramming of T cell-derived small extracellular vesicles using IL2 surface engineering induces potent anti-cancer effects through miRNA delivery.

T cell-derived small extracellular vesicles (sEVs) exhibit anti-cancer effects. However, their anti-cancer potential should be reinforced to enhance clinical applicability. Herein, we generated interleukin-2-tethered sEVs (IL2-sEVs) from engineered Jurkat T cells expressing IL2 at the plasma membrane via a flexible linker to induce an autocrine effect. IL2-sEVs increased the anti-cancer ability of CD8+ T cells without affecting regulatory T (Treg ) cells and down-regulated cellular and exosomal PD-L1 expression in melanoma cells, causing their increased sensitivity to CD8+ T cell-mediated cytotoxicity. Its effect on CD8+ T and melanoma cells was mediated by several IL2-sEV-resident microRNAs (miRNAs), whose expressions were upregulated by the autocrine effects of IL2. Among the miRNAs, miR-181a-3p and miR-223-3p notably reduced the PD-L1 protein levels in melanoma cells. Interestingly, miR-181a-3p increased the activity of CD8+ T cells while suppressing Treg cell activity. IL2-sEVs inhibited tumour progression in melanoma-bearing immunocompetent mice, but not in immunodeficient mice. The combination of IL2-sEVs and existing anti-cancer drugs significantly improved anti-cancer efficacy by decreasing PD-L1 expression in vivo. Thus, IL2-sEVs are potential cancer immunotherapeutic agents that regulate both immune and cancer cells by reprogramming miRNA levels.

Compact SPICE Model of Memristor with Barrier Modulated Considering Short- and Long-Term Memory Characteristics by IGZO Oxygen Content.

This paper introduces a compact SPICE model of a two-terminal memory with a Pd/Ti/IGZO/p+-Si structure. In this paper, short- and long-term components are systematically separated and applied in each model. Such separations are conducted by the applied bias and oxygen flow rate (OFR) during indium gallium zinc oxide (IGZO) deposition. The short- and long-term components in the potentiation and depression curves are modeled by considering the process (OFR of IGZO) and bias conditions. The compact SPICE model with the physical mechanism of SiO2 modulation is introduced, which can be useful for optimizing the specification of memristor devices.

Effect of Post-Annealing on Barrier Modulations in Pd/IGZO/SiO2/p+-Si Memristors.

In this article, we study the post-annealing effect on the synaptic characteristics in Pd/IGZO/SiO2/p+-Si memristor devices. The O-H bond in IGZO films affects the switching characteristics that can be controlled by the annealing process. We propose a switching model based on using a native oxide as the Schottky barrier. The barrier height is extracted by the conduction mechanism of thermionic emission in samples with different annealing temperatures. Additionally, the change in conductance is explained by an energy band diagram including trap models. The activation energy is obtained by the depression curve of the samples with different annealing temperatures to better understand the switching mechanism. Moreover, our results reveal that the annealing temperature and retention can affect the linearity of potentiation and depression. Finally, we investigate the effect of the annealing temperature on the recognition rate of MNIST in the proposed neural network.

Thermal annealing effects on tunnel oxide passivated hole contacts for high-efficiency crystalline silicon solar cells.

Tunnel oxide passivated contacts (TOPCon) embedding a thin oxide layer between polysilicon and base crystalline silicon have shown great potential in the development of solar cells with high conversion efficiency. In this study, we investigate the formation mechanism of hole-carrier selective contacts with TOPCon structure on n-type crystalline silicon wafers. We explore the thermal annealing effects on the passivation properties in terms of the stability of the thermally-formed silicon oxide layer and the deposition conditions of boron-doped polysilicon. To understand the underlying principle of the passivation properties, the active dopant in-diffusion profiles following the thermal annealing are investigated, combined with an analysis of the microscopic structure. Based on PC1D simulation, we find that shallow in-diffusion of boron across a robust tunnel oxide forms a p-n junction and improves the passivation properties. Our findings can provide a pathway to understanding and designing high-quality hole-selective contacts based on the TOPCon structure for the development of highly efficient crystalline silicon solar cells.

Novel antitumor therapeutic strategy using CD4+ T cell-derived extracellular vesicles.

Extracellular vesicles (EVs) mediate cell-cell crosstalk by carrying bioactive molecules derived from cells. Recently, immune cell-derived EVs have been reported to regulate key biological functions such as tumor progression. CD4+ T cells orchestrate overall immunity; however, the biological role of their EVs is unclear. This study reveals that EVs derived from CD4+ T cells increase the antitumor response of CD8+ T cells by enhancing their proliferation and activity without affecting regulatory T cells (Tregs). Moreover, EVs derived from interleukin-2 (IL2)-stimulated CD4+ T cells induce a more enhanced antitumor response of CD8+ T cells compared with that of IL2-unstimulated CD4+ T cell-derived EVs. Mechanistically, miR-25-3p, miR-155-5p, miR-215-5p, and miR-375 within CD4+ T cell-derived EVs are responsible for the induction of CD8+ T cell-mediated antitumor responses. In a melanoma mouse model, the EVs potently suppress tumor growth through CD8+ T cell activation. This study demonstrates that the EVs, in addition to IL2, are important mediators between CD4+ and CD8+ T cells. Furthermore, unlike IL2, clinically used as an antitumor agent, CD4+ T cell-derived EVs stimulate CD8+ T cells without activating Tregs. Therefore, CD4+ T cell-derived EVs may provide a novel direction for cancer immunotherapy by inducing a CD8+ T cell-mediated antitumor response.

Cost-effective method for fabricating carbon nanotube network transistors by reusing a 99% semiconducting carbon nanotube solution.

Carbon nanotubes (CNTs) are one-dimensional materials that have been proposed to replace silicon semiconductors and have been actively studied due to their high carrier mobility, high current density, and high mechanical flexibility. Specifically, highly purified, pre-separated, and solution-processed semiconducting CNTs are suitable for mass production. These CNTs have advantages, such as room-temperature processing compatibility, while enabling a fast and straightforward manufacturing process. In this paper, CNT network transistors were fabricated on a total of five 8 inch wafers by reusing a highly purified and pre-separated 99% semiconductor-enriched CNT solution. The results confirmed that the density of semiconducting CNTs deposited on the five selected wafers was notably uniform, even though the CNT solution was reused up to four times after the initial CNT deposition. Moreover, there was no significant degradation in the key CNT network transistor metrics. Therefore, we believe that our findings regarding this CNT reuse method may provide additional guidance in the field of wafer-scale CNT electronics and may contribute strongly to the development of practical device applications at an ultralow cost.

Immune cell-derived small extracellular vesicles in cancer treatment.

Small extracellular vesicles (sEVs) secreted by most cells carry bioactive macromolecules including proteins, lipids, and nucleic acids for intercellular communication. Given that some immune cell-derived sEVs exhibit anti-cancer properties, these sEVs have received scientific attention for the development of novel anticancer immunotherapeutic agents. In this paper, we reviewed the latest advances concerning the biological roles of immune cell-derived sEVs for cancer therapy. sEVs derived from immune cells including dendritic cells (DCs), T cells, natural-killer (NK) cells, and macrophages are good candidates for sEV-based cancer therapy. Besides their role of cancer vaccines, DC-shed sEVs activated cytotoxic lymphocytes and killed tumor cells. sEVs isolated from NK cells and chimeric antigen receptor (CAR) T cells exhibited cytotoxicity against cancer cells. sEVs derived from CD8+ T and CD4+ T cells inhibited cancer-associated cells in tumor microenvironment (TME) and activated B cells, respectively. M1-macrophage-derived sEVs induced M2 to M1 repolarization and also created a pro-inflammatory environment. Hence, these sEVs, via mono or combination therapy, could be considered in the treatment of cancer patients in the future. In addition, sEVs derived from cytokine-stimulated immune cells or sEV engineering could improve their anti-tumor potency. [BMB Reports 2022; 55(1): 48-56].

Analysis of Threshold Voltage Shift for Full VGS/VDS/Oxygen-Content Span under Positive Bias Stress in Bottom-Gate Amorphous InGaZnO Thin-Film Transistors.

In this study, we analyzed the threshold voltage shift characteristics of bottom-gate amorphous indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) under a wide range of positive stress voltages. We investigated four mechanisms: electron trapping at the gate insulator layer by a vertical electric field, electron trapping at the drain-side GI layer by hot-carrier injection, hole trapping at the source-side etch-stop layer by impact ionization, and donor-like state creation in the drain-side IGZO layer by a lateral electric field. To accurately analyze each mechanism, the local threshold voltages of the source and drain sides were measured by forward and reverse read-out. By using contour maps of the threshold voltage shift, we investigated which mechanism was dominant in various gate and drain stress voltage pairs. In addition, we investigated the effect of the oxygen content of the IGZO layer on the positive stress-induced threshold voltage shift. For oxygen-rich devices and oxygen-poor devices, the threshold voltage shift as well as the change in the density of states were analyzed.

Characterization of Spatial Distribution of Trap Across the Substrate in Metal-Insulator-Semiconductor Structure with Band Bending Effect.

We report the technique of trap distribution extraction according to the vertical position of the substrate in the p-MOSFET. This study was conducted on a single device. This technique is an experimental method. Ctrap was extracted based on the deep depletion C-V characteristics. In VFB, the trap level is neutral. When bias is applied, the energy band bends, resulting in modulation of the quasi-Fermi level. The area created by the bending of the energy band is equal to the area created by the Fermi level modulation. The trap level existing in this area becomes charged. Considering this, the spatial distribution of Trap was extracted. The trap extracted by the proposed method has a maximum value at the interface, rapidly decreases, and is distributed up to 8 nm in the vertical direction. The study of trap spatial distribution is expected to be applicable to the separation of trap interface state and bulk trap extraction later.

Defect spectroscopy of sidewall interfaces in gate-all-around silicon nanosheet FET.

Through time-dependent defect spectroscopy and low-frequency noise measurements, we investigate and characterize the differences of carrier trapping processes occurred by different interfaces (top/sidewall) of the gate-all-around silicon nanosheet field-effect transistor (GAA SiNS FET). In a GAA SiNS FET fabricated by the top-down process, the traps at the sidewall interface significantly affect the device performance as the width decreases. Compare to expectations, as the width of the device decreases, the subthreshold swing (SS) increases from 120 to 230 mV/dec, resulting in less gate controllability. In narrow-width devices, the effect of traps located at the sidewall interface is significantly dominant, and the 1/f 2 noise, also known as generation-recombination (G-R) noise, is clearly appeared with an increased time constant (τ i ). In addition, the probability density distributions for the normalized current fluctuations (ΔI D) show only one Gaussian in wide-width devices, whereas they are separated into four Gaussians with increased in narrow-width devices. Therefore, fitting is performed through the carrier number fluctuation-correlated with mobility fluctuations model that separately considered the effects of sidewall. In narrow-width GAA SiNS FETs, consequently, the extracted interface trap densities (N T ) distribution becomes more dominant, and the scattering parameter ([Formula: see text]) distribution increases by more than double.

Wafer-scale carbon nanotube network transistors.

Highly purified, preseparated semiconducting carbon nanotubes (CNTs) hold great potential for high-performance CNT network transistors due to their high electrical conductivity, high mechanical strength, and room-temperature processing compatibility. In this paper, we report our recent progress on CNT network transistors integrated on an 8-inch wafer. We observe that the key device performance parameters of CNT network transistors at various locations on an 8-inch wafer are highly uniform and that the device yield is impressive. Therefore, this work validates a promising path toward mass production and will make a significant contribution to the future field of wafer-scale CNT electronics.