This paper outlines the RC-filtered stress-decoupled (RCSD) 4T2R nonvolatile TCAM (nvTCAM) with the following benefits: 1) reduced NVM-stress; 2) reduced ML parasitic load; and 3) suppression of ...match-line (ML) leakage current from match cells. The RCSD-4T2R cell achieves a 6× reduction in NVM-stress, a 2× increase in maximum wordlength, and a 2× reduction in search delay. In this paper, we also outline two search schemes, referred to as dynamic source-line pulse controlled (DSL-PC) search and dataline-pulse controlled (DL-PC) search, which were developed specifically for the RCSD-4T2R nvTCAM. We fabricated a 128 × 32 b RCSD-4T2R nvTCAM macro with HfO ReRAM using a 180 nm CMOS process. Using the DSL-PC and DL-PC schemes, the measured search delay of the RCSD-4T2R nvTCAM macro was 1.2 ns under typical VDD.
As 2.5D/3D die stacking technology emerges, stacked dynamic random access memory (DRAM) has been proposed as a cache due to its large capacity in order to bridge the latency gap between off-chip ...memory and SRAM caches. The main problems in utilizing a DRAM cache are the high tag storage overhead and the high lookup latency. To address these, we propose tags-in-eDRAM (embedded DRAM) due to its higher density and lower latency. This paper presents an eTag DRAM cache architecture that is composed of a novel tag-comparison-in-memory scheme to achieve direct data access. It eliminates access latency and comparison power by pushing tag-comparison into the sense amplifier. Furthermore, we propose a Merged Tag to enhance the eTag DRAM cache by comparing last-level cache tags and DRAM cache tags in parallel. Simulation results show that the eTag DRAM cache improves energy efficiency by 15.4% and 33.9% in 4-core and 8-core workloads, respectively. Additionally, the Merged Tag achieves 32.1% and 48.7% energy efficiency improvements in 4-core and 8-core workloads, respectively.
Ternary content-addressable memory (TCAM)-based search engines generally need a priority encoder (PE) to select the highest priority match entry for resolving the multiple match problem due to the ...don't care (X) features of TCAM. In contemporary network security, TCAM-based search engines are widely used in regular expression matching across multiple packets to protect against attacks, such as by viruses and spam. However, the use of PE results in increased energy consumption for pattern updates and search operations. Instead of using PEs to determine the match, our solution is a three-phase search operation that utilizes the length information of the matched patterns to decide the longest pattern match data. This paper proposes a promising memory technology called priority-decision in memory (PDM), which eliminates the need for PEs and removes restrictions on ordering, implying that patterns can be stored in an arbitrary order without sorting their lengths. Moreover, we present a sequential input-state (SIS) scheme to disable the mass of redundant search operations in state segments on the basis of an analysis distribution of hex signatures in a virus database. Experimental results demonstrate that the PDM-based technology can improve update energy consumption of nonvolatile TCAM (nvTCAM) search engines by 36%-67%, because most of the energy in these search engines is used to reorder. By adopting the SIS-based method to avoid unnecessary search operations in a TCAM array, the search energy reduction is around 64% of nvTCAM search engines.
The adsorption and activation of both CO2 and methanol are mainly affected by the distance of the Lewis acid site, Zr4+, and Lewis base, Zr4+/O2−, of the Zr-based catalysts. In this paper, ...Zr-incorporated SBA-15 (Zr-SBA-15) and Zr-grafted SBA-15 (Zr/SBA-15) catalysts were prepared with different Zr environments, and were analyzed with N2 adsorption–desorption isotherms, X-ray diffraction, UV-vis spectra, and XPS. It was proposed that Zr-SBA-15 catalyst with Si-O-Zr-OH and Zr-O-Si-OH structure exhibited non-adjacent sites between Zr4+ and Zr4+/O2−, while Zr/SBA-15 catalyst with Zr-O-Zr-OH structure showed neighboring sites between Zr4+ and Zr4+/O2−. Furthermore, the Zr/SBA-15 catalyst exhibited good catalytic activity, while no DMC was detected over the Zr-SBA-15 catalyst at the same reaction conditions. For combined in situ infrared and catalytic performance, it was indicated that the methanol and CO2 could be activated to form DMC, only when the Zr4+ and Zr4+/O2− sites existed and were adjacent to each other in the Zr-O-Zr-OH of Zr/SBA-15 catalyst.
In a modern system-on-chip design, hundreds of cores and intellectual properties can be integrated into a single chip. To be suitable for high-performance interconnects, designers increasingly adopt ...advanced interconnect protocols that support novel mechanisms of parallel accessing, including outstanding transactions and out-of-order completion of transactions. To implement those novel mechanisms, a master tags an ID to each transaction to decide in-order or out-of-order properties. However, these advanced protocols may lead to transaction deadlocks that do not occur in traditional protocols. To prevent the deadlock problem, current solutions stall suspicious transactions and in certain cases, many such stalls can incur serious performance penalty. In this brief, we propose a novel ID assignment mechanism that guarantees the issued transactions to be deadlock-free and results in significant reduction in the number of transaction stalls issued by masters. Our experimental results show encouraging performance improvements compared with previous works with little hardware and power overheads.
For multilevel cell (MLC) phase change memory (PCM), resistance drift (R-drift) phenomenon causes cell resistance to increase with time, even at room temperature. As a result, the ...fixed-threshold-retention (FTR) raw-bit-error-rate (RBER) surpasses practical ECC correction ability within hours after being programmed. This study proposes a resistance drift compensation (RDC) scheme to mitigate R-drift issue. The proposed RDC scheme realizes PCM drift compensation and features RDC pulse to suppress ECC decoding failure. The proposed approach was validated using a 90-nm 128M cells PCM chip and an FPGA-based memory controller verification system. The MLC PCM FTR RBER has been suppressed by over 100×, thereby bringing it within ECC capability. The effectiveness of the RDC scheme was verified up to 10 6 cycles.
Soft error has become an important reliability issue in advanced technologies. To tolerate soft errors, solutions suggested in previous works incur significant performance and power penalties, ...especially when a design with fault-tolerant structures is overprotected. In this paper, we present a soft-error-tolerant design methodology to tradeoff performance, power, and reliability for different applications. First, four novel detection and correction flip-flop (FF) structures are proposed to provide different levels of tolerance capability against soft errors. Second, architecture-level vulnerability and logic-level susceptibility analyses are employed to identify weak FFs that can easily cause program execution errors. Third, an optimization framework is developed to synthesize the proposed four novel FF structures into weak and highly observable storage bits with the flexibility of trading off performance, power, and reliability. A five-stage pipeline RISC core (UniRISC) is adopted to demonstrate the usefulness of our methodology. Experimental results show that the proposed method can accomplish design goals by balancing performance, power, and reliability. For example, we can not only satisfy the reliability requirement that no more than five errors occur per one billion hours in a design but also reduce up to 87% performance overhead and 91% power overhead when compared with previous works.
The study evaluated a proper strategy for recovering hydrogen production in a pilot plant from methanogen invasion. The pilot biohydrgoen reactor with a working volume of 1 m
3 was constructed and a ...stream of gluten manufacturing wastewater was used as the major substrate. When the gluten wastewater was introduced into the reactor, methane appeared in the biogas and hydrogen decreased to zero accumulation. By increasing the organic loading rate from 6.7 to 13.4 kg-COD/m
3/d and reducing the hydraulic retention time from 1.5 to 1 day spontaneously, methanogens can be suppressed in 7 days. Besides, the total volatile fatty acids increase after the adjustment. However, high ethanol concentration in the influent revealed that only limited carbohydrate was available for biohydrogenation. The sugar content in the gluten wastewater can be degraded drastically in 5 days under both acidifying and alkalizing preservation conditions. 5 g/L ethanol and 3 g/L lactate was accumulated in the substrate storage tank resulting in limit carbohydrate for biohydrogenation under acidifying preservation condition. On the other hand, alkalizing preservation condition is a better approach and can preserve 80% of the carbohydrate within 2 days but various volatile fatty acids also accumulated without ethanol production. It is suggested that the gluten wastewater should be fed into the biohydrogen reactor as soon as possible and supplement such as solid organic wastes can also be introduced to maintain a proper organic loading rate and sustain bioactivity of biohydrogenation.
A laboratory study was undertaken to explore the capability of one-stage ANAMMOX in a hybrid biofilm-carrier reactor (HBCR) fed with petrochemical wastewater. Under favorable operating conditions in ...continuous-flow operations (at the dissolved oxygen level of 0.5-1.0 mg L(-1)), the average total nitrogen (TN) removal efficiency reached 62-67% and approximately 90% of TN can be removed by ANAMMOX. In batch operations of the hybrid biofilm-carrier reactor (without adding carbon substrate), the specific TN removal rate of the reactor in which both Kaldnes and nonwoven carriers were kept was two-fold higher than that of the reactor in which only nonwoven carriers were kept. This indicated that the microbial activity of thinner biofilms (Kaldnes carriers) was remarkably higher than that of thicker biofilms (nonwoven carriers). Finally, based on the 16S rRNA clone library, a cluster of ANAMMOX Candidatus Kuenenia stuttgartiensis was identified.
The disadvantage of Ce/Zr metal oxide as catalyst for direct synthesis dimethyl carbonate (DMC) from CO2 and methanol is low DMC formation rate because of its low specific surface area and active ...sites. In this work, it can be improved by highly uniform dispersion cerium doped Zr-based metal-organic frameworks (UiO-66 MOFs), which were synthesized via a modified hydrothermal method. The as-prepared catalysts have been extensively characterized using XRD, BET, FT-IR, SEM, TEM, TGA, NH3-TPD, CO2-TPD, XPS techniques. Experimental evaluation results indicated that the highly uniform dispersed Ce-doped UiO-66 MOFs exhibited markedly improved catalytic performance than traditional Ce/Zr metal oxide catalyst. The highest yield of DMC catalyzed by Ce-UiO-66–2 was 0.295% (reaction time was 12 h; reaction temperature was 140 °C; reaction pressure was 11 MPa). Then, it was found that doping of Ce atoms into the zirconium lattice to produce UiO-66 MOFs could effectively increase the number of acidic and medium basic sites than UiO-66 (none Ce), thus could greatly enhance the catalytic performance. Moreover, using 2-cyanopyridine as dehydrating agent, the DMC yield could be further raised greatly. Last, based on reported literature and our results, a possible reaction mechanism over Ce-UiO-66-X was proposed.
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•Ce-doped UiO-66 material (Ce-UiO-66-X) was prepared by one-step synthesis.•Ce modification increased the number of acid-base active sites and specific surface area.•Both acid-medium base sites and specific surface area promoted DMC formation.•DMC yield can be increased by about ten times in presence of 2-cyanopyridine.
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