Dissolution behaviors of PuO2(cr) in natural waters

PuO2(cr) dissolution in natural water was investigated at 25°C and 60°C under atmospheric conditions. The concentration of Pu in solutions [Pu], was monitored for 1 year of reaction time. PuO2(cr) dissolution in natural water reached a steady state within 2 months at 25°C. The [Pu] in groundwater and seawater at pH 8 were in the range of [Pu] = 0.9–34 and 3.4–27 nM, respectively. The [Pu] in concrete porewater (rainwater equilibrated with concrete) at pH 8.1–10.9 was in the range of 0.1–3.2 nM. The [Pu] and pH values of groundwater were similar to those of seawater samples having a high ionic strength. The measured [Pu] at equilibrium in all samples was higher than the calculated solubility curves for PuO2(am, hyd). Experimental evidence is insufficient to confirm the oxidation state of Pu in solution and solid phases. However, the results of geochemical modeling indicate that PuO2(am, hyd) and aqueous Pu(IV) species are dominant in natural water samples of this work. The dissolution behavior of PuO2(cr) in natural waters is comparable to the oxidative dissolution of PuO2(am, hyd) in the presence of PuO2(coll, hyd). The dissolution of PuO2 in groundwater decreased at higher temperatures, whereas the influence of temperature in seawater and porewater was not significant under these experimental conditions

Analyzing Various Structural and Temperature Characteristics of Floating Gate Field Effect Transistors Applicable to Fine-Grain Logic-in-Memory Devices

Although the von Neumann architecture-based computing system has been used for a long time, its limitations in data processing, energy consumption, etc. have led to research on various devices and circuit systems suitable for logic-in-memory (LiM) computing applications. In this paper, we analyze the temperature-dependent device and circuit characteristics of the floating gate field effect transistor (FGFET) source drain barrier (SDB) and FGFET central shallow barrier (CSB) identified in previous papers, and their applicability to LiM applications is specifically confirmed. These FGFETs have the advantage of being much more compatible with existing silicon-based complementary metal oxide semiconductor (CMOS) processes compared to devices using new materials such as ferroelectrics for LiM computing. Utilizing the 32 nm technology node, the leading-edge node where the planar metal oxide semiconductor field effect transistor structure is applied, FGFET devices were analyzed in TCAD, and an environment for analyzing circuits in HSPICE was established. To seamlessly connect FGFET-based devices and circuit analyses, compact models of FGFET-SDB and -CSBs were developed and applied to the design of ternary content-addressable memory (TCAM) and full adder (FA) circuits for LiM. In addition, depression and potential for application of FGFET devices to neural networks were analyzed. The temperature-dependent characteristics of the TCAM and FA circuits with FGFETs were analyzed as an indicator of energy and delay time, and the appropriate number of CSBs should be applied

Fault-Coping Algorithm for Improving Leader–Follower Swarm-Control Algorithm of Unmanned Surface Vehicles

This study presents a swarm-control algorithm to overcome the limitations inherent to single-object systems. The leader–follower swarm-control method was selected for its ease of mathematical interpretation and theoretical potential for the unlimited expansion of followers. However, a known drawback of this method is the risk of swarm collapse when the leader breaks down. To address this, a fault-coping algorithm was developed and supplemented to the leader–follower swarm-control method, which enabled the detection and responsive handling of failures, thereby ensuring mission continuity. Comprehensive data, including voltage, current, thruster speed, position, and heading angle were acquired and analyzed using sensors on unmanned surface vehicles (USVs) to monitor potential failures. In the case of a failure, such as thruster malfunction, the nearest USV seamlessly takes charge of the mission under the guidance of the fault-coping algorithm. The leader–follower swarm-control and fault-coping algorithms were successfully validated through actual sea area tests, which confirmed their operational efficacy. This study affirms the well-formed nature of the USV swarm formation and demonstrates the effectiveness of the fault-coping algorithm in ensuring normal mission performance under the virtual failure scenarios applied to the leader USV

Non-volatile logic-in-memory ternary content addressable memory circuit with floating gate field effect transistor

Due to the limitations of the currently widely used von Neumann architecture-based computing system, research on various devices and circuit systems suitable for logic-in-memory computing applications has been conducted. In this work, the silicon-based floating gate memory cell transistor structure, which has been attracting attention as a memory to replace the dynamic random access memory or NAND Flash technology, was newly recalled, and its applicability to logic-in-memory application was confirmed. This floating gate field effect transistor (FGFET) has the advantage that the compatibility of the existing silicon-based complementary metal–oxide–semiconductor (CMOS) process is far superior to that of logic-in-memory application devices to which materials with new memory characteristics are applied. At the 32 nm technology node, which is the front node to which the planar MOSFET structure is applied, an analysis environment that can simultaneously analyze the device and circuit of the FGFET was established. For a seamless connection between FGFET-based devices and circuit analysis, the compact model of the FGFET was developed, which is applied to logic-in-memory ternary content addressable memory (TCAM) circuit design. It was verified that the two types of logic-in-memory TCAM circuits to which FGFETs are applied are superior to a conventional CMOS FET-based TCAM circuit in the number of devices used (=circuit area) and power/energy efficiency

Analysis of Logic-in-Memory Full Adder Circuit With Floating Gate Field Effect Transistor (FGFET)

The high data throughput and high energy efficiency required recently are increasingly difficult to implement due to the von Neumann bottleneck. As a way to overcome this, Logic-in-Memory (LiM) technology has recently been receiving a lot of attention. In particular, since the addition function is important to solve high data throughput in applications such as artificial intelligence, the results of applying various fine-grain LiM application devices to full adder circuit design are being announced. In this paper, a Floating Gate Field Effect Transistor (FGFET), which has a structure similar to a floating gate memory cell transistor that has been widely used in the past and is highly applicable to mass production, was applied to the LiM application circuit design. Prior to application to circuit design, the FGFET characteristics were confirmed using a well-calibrated technology computer-aided design (TCAD) simulation at the 32nm technology node, and a compact model was developed to describe them. Afterwards, the delay and power consumption were evaluated with three different types of FGFET-based full adder circuits, and benchmarked with conventional CMOS (complementary metal-oxide-semiconductor)-based conventional full adder circuits

Sequential Production of Lignin, Fatty Acid Methyl Esters and Biogas from Spent Coffee Grounds via an Integrated Physicochemical and Biological Process

Spent coffee grounds (SCG) are one of the lignocellulosic biomasses that have gained much attention due to their high potential both in valorization and biomethane production. Previous studies have reported single processes that extract either fatty acids/lignin or biogas. In this study, an integrated physicochemical and biological process was investigated, which sequentially recovers lignin, fatty acid methyl esters (FAME) and biogas from the residue of SCG. The determination of optimal conditions for sequential separation was based on central composite design (CCD) and response surface methodology (RSM). Independent variables adopted in this study were reaction temperature (86.1–203.9 °C), concentration of sulfuric acid (0.0–6.4%v/v) and methanol to SCG ratio (1.3–4.7 mL/g). Under determined optimal conditions of 161.0 °C, 3.6% and 4.7 mL/g, lignin and FAME yields were estimated to be 55.5% and 62.4%, respectively. FAME extracted from SCG consisted of 41.7% C16 and 48.16% C18, which makes the extractives appropriate materials to convert into biodiesel. Results from Fourier transform infrared spectroscopy (FT-IR) further support that lignin and FAME extracted from SCG have structures similar to previously reported extractives from other lignocellulosic biomasses. The solid residue remaining after lignin and FAME extraction was anaerobically digested under mesophilic conditions, resulting in a methane yield of 36.0 mL-CH4/g-VSadded. This study is the first to introduce an integrated resource recovery platform capable of valorization of a municipal solid waste stream