A ReRAM Memory Compiler for Monolithic 3D Integrated Circuits in a Carbon Nanotube Process

We present a ReRAM memory compiler for monolithic 3D (M3D) integrated circuits (IC). We develop ReRAM architectures for M3D ICs using 1T-1R bit cells and single and multiple tiers of transistors for access and peripheral circuits. The compiler includes an automated flow for generation of subarrays of different dimensions and larger arrays of a target capacity by integrating multiple subarrays. The compiler is demonstrated using an M3D process design kit (PDK) based on a Carbon Nanotube Transistor technology. The PDK includes multiple layers of transistors and back-end-of-the-line integrated ReRAM. Simulations show the compiled ReRAM macros with multiple tiers of transistors reduces footprint and improves performance over the macros with single-tier transistors. The compiler creates layout views that are exported into library exchange format or graphic data system for full-array assembly and schematic/symbol views to extract per-bit read/write energy and read latency. Comparison of the proposed M3D subarray architectures with baseline 2D subarrays, generated with a custom-designed set of bit cells and peripherals, demonstrate up to 48% area reduction and 13% latency improvement.

A Systematic Characterization Approach for Vacuum Bag Only Prepregs towards an Accurate Process Design

Aerospace-grade composite parts can be manufactured using Vacuum Bag Only prepregs through an accurate process design. Quality in the desired part can be realized by following process modeling, process optimization, and validation, which strongly depend on a primary and systematic material characterization methodology of the prepreg system and material constitutive behavior. The present study introduces a systematic characterization approach of a Vacuum Bag Only prepreg by covering the relevant material properties in an integrated manner with the process mechanisms of fluid flow, consolidation, and heat transfer. The characterization recipe is practiced under the categories of (i) resin system, (ii) fiber architecture, and (iii) thermal behavior. First, empirical models are successively developed for the cure-kinetics, glass transition temperature, and viscosity for the resin system. Then, the fiber architecture of the uncured prepreg system is identified with X-ray tomography to obtain the air permeability. Finally, the thermal characteristics of the prepreg and its constituents are experimentally characterized by adopting a novel specimen preparation technique for the specific heat capacity and thermal conductivity. Thus, this systematic approach is designed to provide the material data to process modeling with the motivation of a robust and integrated Vacuum Bag Only process design.

Process Design for Biohydrogen Production from Waste Materials and Its Application

Biohydrogen is regarded as an attractive future clean energy carrier due to its high energy content and environmentally friendly conversion. Biohydrogen reactor is widely used in studies concerning the anaerobic co-digestion of food waste, sewage sludge, wastewater and other organic solids. Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material (biomass or waste feedstock) in the absence of oxygen to produce biogas, which may generate electricity and heat, or can be processed into renewable natural gas and transportation fuels. This review article explains the scientific processes of anaerobic digestion process such as hydrolysis, acidogenesis, acetogenesis and hydrogenesis as well as methods to produce biohydrogen gas such as fermentation and biophotolysis for the waste management technology and sources of renewable energy and concludes with solutions that may allow anaerobic digestion to become more widely adopted throughout the developing countries to control the waste management system.