Reduction In Active Area Research Articles

Compact SRAM-Based PUF Chip Employing Body Voltage Control Technique

This paper presents an ultra-small physical unclonable function (PUF) chip structure to protect data in compact IoT sensor devices. The proposed PUF has far fewer transistors and a reduced active area compared to the conventional strong PUF with multiple challenge response pairs (CRPs). According to the manufacturing process variations, the conventional SRAM-based PUF uses a switching transistor and a main transistor to implement multiple CRPs, whereas the proposed structure adds the function of a switching transistor to a single main transistor, controlling the body voltage to switch the transistor. This unified and simple PUF structure results in significant silicon area reduction. For a PUF with a 32-bit challenge, the number of transistors is significantly reduced by 40&#x0025;; the active area of the conventional structure is <inline-formula> <tex-math notation="LaTeX">$57.78~\mu m^{2}$ </tex-math></inline-formula> while the area of the proposed structure is <inline-formula> <tex-math notation="LaTeX">$36.4~\mu m^{2}$ </tex-math></inline-formula>. Overall, an active area reduction of 38&#x0025; is realized with the same number of CRPs. Here, we implemented an SRAM-based PUF system with a 32-bit challenge, a 1024-bit response, and 160 million CRPs. PUF core cell shows energy efficiency of 0.09 pJ/bit. The inter-Hamming distance is 48.89&#x0025;, while the intra-Hamming distance is 1.2&#x0025; after data post-processing, i.e., discarding unstable bits. A prototype chip is implemented in the 65nm CMOS process with a supply voltage of 1.2V. Compared to the prior arts, the proposed prototype is shown effective silicon area reduction while maintaining remarkable energy efficiency.

Voltage differencing buffered amplifier based low power, high frequency and universal filters using 32 nm CNTFET technology

This work presents filter applications of carbon nanotube field effect transistors (CNTFET) voltage differencing buffered amplifier (VDBA) based high frequency universal filters using 32 nm CNTFET technology of Stanford University model. CNTFETs are potential candidates to replace conventional silicon-based transistors due to their exceptional material properties. In addition, by changing chirality of carbon nanotube (CNT), the material property can be easily changed from semiconducting material to metallic. The VDBA is an active element of circuit which has high input impedance and low output impedance. These types of blocks provide an advantage for voltage mode circuits allowing cascadability and no critical component matching. The proposed CNTFET VDBA shows much higher frequency response with about 67 GHz at first stage which is well known OTA block and around 30 GHz at second stage, power consumption around 135 times less than 0.35 μm TSMC technology and 2476 times reduction in active area of chip. HSPICE and MATLAB simulation tools are used to perform all simulations.

CFD Simulation of an Industrial PEM Fuel Cell with Local Degradation Effects

AbstractThe polymer electrolyte membrane (PEM) fuel cell model of a commercial software package is presented. The basic performance model is extended by two chemical degradation effects: ionomer degradation and carbon corrosion including platinum oxidation. The ionomer degradation model describes the ionomer mass loss due to hydrogen peroxide formation and subsequent attack of the ionomer by radicals. The carbon corrosion model calculates the carbon mass loss caused by carbon oxidation and the active area reduction due to platinum oxidation. The degradation models are coupled with an agglomerate model of the catalyst layer. The model is validated against measurements on an industrial cell. For these measurements, the cell is equipped with a segmented measuring board, which is used to measure the current density distribution and high frequency resistance of every segment. In order to test the predictability of the model under different operating conditions, measurements for stoichiometry and pressure variations are carried out. Calculated and measured current density distributions of the cell, aged by an accelerated stress test, are compared for the validation of the degradation model. Moreover, 3D simulation results of the fresh and aged cells are analyzed in detail and the influence of operating conditions on fuel cell aging is pointed out.

Novel closed anode pressure-swing system for proton exchange membrane fuel cells

To overcome the low system efficiency and fuel efficiency in conventional recirculation systems and purging systems, a new anode closed pressure-swing system for proton exchange membrane fuel cells (PEMFCs) is proposed in this paper. Only two pressure regulators set at different pressures and a buffer tank are applied to produce pressure-swing inside the anode through the process of hydrogen feed and reaction, thereby achieving the anode-dead-end (ADE) operation (no purging). This system was successfully tested on a 20-cell open-cathode stack. The results indicate that the performance of the stack with the developed system is stable and efficient over 13,000 s, while its performance in ADE mode without purging deteriorates rapidly because of active area reduction. It can be concluded that the pressure swing system provides the following advantages: close to 100% hydrogen utilization; improved stack performance of around 12.5% for the power compare to the ADE mode with intermittent purging at 12 V load; improved humidification of the anode and membrane; and ease of implementation as there are no extra pumps.

Fully Integrated High Voltage Pulse Driver Using Switched-Capacitor Voltage Multiplier and Synchronous Charge Compensation in 65-nm CMOS

This brief presents a high efficiency fully integrated high-voltage (HV) pulse driver in standard CMOS. Powered by a standard I/O DC voltage of 2.5 V, the proposed system employs an optimized 4-stage cross-coupled switched-capacitor voltage multiplier (SCVM) together with an on-chip HV output driver to generate HV pulses of >10 V. We propose an area-efficient HV output driver stage to reach up to 12% total active area reduction when compared with the conventional implementation while maintaining the low static power characteristics. We also present a synchronous charge compensation (SQC) technique to alleviate the loading-dependent signal distortion through reducing the HV rail voltage droop and improving the HV pulse settling time during the driver output transitions. Fabricated in 65-nm bulk CMOS, the chip prototype can successfully generate HV pulses from 250 kHz to 1 MHz with a 15 pF load while ensuring no device breakdown. Measurement results demonstrate a peak SCVM power conversion efficiency (PCE) of 50% and an overall driving efficiency of 12.25%. The chip prototype attains a $\sim 2\times $ faster output pulse transition speed compared with the state-of-the-art.

Pressure-Induced Control of Core-Shell Nanoparticles for Oxygen Reduction Reaction

Precious metal-based active metals are mainly used as electrocatalysts for ORR (Oxygen Reduction Reaction), and cost and durability are major research and development issues in fuel cell applications. In order to obtain high performance in electrocatalysts, composition, dispersion, structure and particle size have been studied as key parameters. A number of researchers have been reporting enhanced ORR performance by alloying approaches. Platinum-based alloy nanoparticles are typically prepared through a heat treatment process, which can result in significant levels of specific activity and mass activity improvements. However, the high temperature of the alloying process leads to size growth of the nanoparticles, resulting in a reduction in active area. In order to prevent growth of nanoparticle size during heat treatment, various approaches have been reported such as forming a protective layer by using physical barriers using inorganic and organic materials [1-3]. However, in this case, post-treatment or additional process is required to remove the protective layer, which limits the mass production. In this work, we propose a method to easily control the size of the core-shell nanoparticles by controlling the pressure of the inert gas during the heat treatment process. As synthesized M@Pt/C (M = Co, Fe, etc.) catalysts were conducted heat treatment with varied pressure control (1, 40, 80 bar) under inert atmosphere. The average size of the metal nanoparticles was distributed in the range of about 3 to 5 nm, and the particle size was clearly reduced in inverse proportion to the pressure. By scanning transmission electron microscopy (STEM) analysis, we also confirmed that the catalysts show clear M core-Pt shell structure. Theoretical calculations show the correlation between the size of metal nanoparticles and external pressure. Herein, we introduce a novel particle size control method (Pressure-induced particle size control). Furthermore, we believe that our unique synthetic approach can be a promising way to obtain intermetallic structure NPs with controlled particle size.

Synthesis and characterization of electrodeposited Ni-B-Tl2O3 composite coatings

Ni-B coatings are promising materials for several applications in electronics, nuclear, automotive, aerospace, petrochemical and food industries owing to their exceptional mechanical and chemical properties such as, high hardness, high wear resistance and good corrosion resistance. However, the literature indicates that there is still significant scope for further improvement in properties of these coatings in order to improve their in-service performance and/or total service life. Considering this fact, a novel Ni-B-Tl2O3 composite coatings has been developed via electrodeposition technique by reinforcing Tl2O3 particles into the Ni-B matrix. The effect of addition of Tl2O3 particles on the morphology, structure and electrochemical properties of Ni-B-Tl2O3 coatings was investigated and compared with that of the Ni-B coatings. A substantial change on surface roughness, thermal properties, crystal structure, mechanical properties and corrosion resistance was observed due to the addition of Tl2O3 particles to the Ni-B coatings. The as-deposited Ni-B coatings were found to be amorphous in nature, however the crystallinity of the composite coatings was significantly improved by the addition of the Tl2O3 particles. Surface analyses showed an increase in surface roughness due to the addition of Tl2O3 particles, which confirms the formation of fine and dense structures in both Ni-B and Ni-B- Tl2O3 coatings. There is significant improvement in microhardness (by 80%) and elastic modulus (by 60%) of Ni-B-Tl2O3 composite coatings as compared to Ni-B coatings mainly due to the addition of Tl2O3 particles. Corrosion resistance was found to be improved significantly after the incorporation of Tl2O3 into the Ni-B matrix which may be attributed to reduction in active area of Ni-B matrix.

Miniaturized UWB multi-resonance patch antenna loaded with novel modified H-shape SRR metamaterial for microspacecraft applications

We present the design and analysis of a novel modified H-shaped split ring resonator (SRR) metamaterial. It has negative permeability and permittivity characteristics with multi-band resonance for the X, Ku, and Ka frequency bands. Different configurations of the patch antenna have been analyzed with different orientations and positions of the metamaterial. Optimized performance was achieved with the new shape of the metamaterial antenna with an appreciable 9 dB gain, 77 GHz bandwidth, 100% radiation efficiency, and 65% reduction in active area. The second-order fractal metamaterial antenna achieves high miniaturization on the order of 1/21. This is truly a boon in the communications world, as a sharp beam with smaller physical dimensions is urgently required.

Wide operating frequency resonant clock and data circuits for switching power reductions

Driver circuits that save switching power by 25 % or more using LC resonance energy recovery are shown for use in clock and data networks. Resonant and other energy savings circuits are shown from global to local leaf cell clocking. A 10× operating frequency range with power reductions allows dynamic voltage and frequency scaling for power management. The resonance used only for the brief transition periods rather than the entire clock cycle and thus small on-chip inductors around 2 nH range are sufficient to support this timing. A new resonant driver that generates tracking pulses at each transition of clock for dual edge operation across scaled frequencies is proposed. The design is readily scaled from 90 to 45 nm in standard CMOS processes and beyond. It is robust with 50 % variation in component values for functionality and skew performance. The resulting power savings add up to 10's of watts in high performance processors. Skew reductions are achieved without needing to increase the interconnect widths. A 40 % driver active area reduction is also achieved. The scheme is naturally compatible with dynamic logic allowing their increased use at lower power.

Properties of electrodeposited Ni–B–Al2O3 composite coatings

Ni–B coatings have gained a great deal of attraction due to their promising mechanical properties. Owing to tempting properties, Ni–B coatings have succeeded to find their applications in automotive, aerospace, petrochemical, plastic, optics, nuclear, electronics, computer, textile, paper, food and printing industries. Despite having promising properties, further improvement in their properties is essential so that more challenging requirements and new developments can be successfully addressed. In the present study, novel Ni–B–Al2O3 composite coatings have been synthesized through electrodeposition process by reinforcing Ni–B matrix with Al2O3 particles. A comparison of properties of Ni–B and Ni–B–Al2O3 coatings in their as deposited states is presented to elucidate the beneficial role of Al2O3 addition. The structural analyses indicate that Ni–B coatings exhibit a single broad peak indicative of an amorphous structure. However, the addition of Al2O3 into Ni–B matrix considerably improves the crystallinity of the deposit. The surface morphology study reveals the formation of uniform, dense and fine-grained deposit in both Ni–B and Ni–B–Al2O3 composite coatings. However, addition of Al2O3 particles into Ni–B coatings results in high surface roughness. The nanoindentation results demonstrates that the addition of Al2O3 into Ni–B matrix results in significant improvement in mechanical properties (hardness and modulus of elasticity) which may be attributed to dispersion hardening of Ni–B matrix by hard Al2O3 particles. The linear polarization tests confirm that the addition of Al2O3 improves the corrosion resistance of Ni–B coatings. This improvement in corrosion behavior may be attributed to the reduction in active area of Ni–B matrix by the presence of inactive Al2O3 particles.

Synthesis and properties of electrodeposited Ni–B–CeO2 composite coatings

Ni–B coatings are extremely hard and wear resistant with decent anticorrosion properties which make them suitable for automotive, aerospace, petrochemical, plastic, optics, nuclear, electronics, computer, textile, paper, food and printing industries. However, further improvement in properties is essential to address more challenging requirements and new developments. In the present study, Ni–B and novel Ni–B–CeO2 composite coatings were electrodeposited (ED) on mild steel substrates using dimethylamine borane (DMAB) as a reducing agent. A comparison of properties of Ni–B and Ni–B–CeO2 coatings is presented to elucidate the useful role of CeO2 addition. The structural analyses indicate that Ni–B coatings are amorphous in their as deposited state. However, addition of CeO2 into Ni–B matrix considerably improves the crystallinity of the deposit. The surface morphology study reveals the formation of uniform, dense and fine-grained deposit in both Ni–B and Ni–B–CeO2 composite coatings. However, Ni–B–CeO2 composite coatings exhibit high surface roughness. The nano mechanical properties show that the addition of CeO2 particles into Ni–B matrix results in remarkable improvement in mechanical properties (hardness and modulus of elasticity) which may be attributed to dispersion hardening of Ni–B matrix by CeO2 particles. The electrochemical polarization tests confirm that the addition of CeO2 improves the corrosion resistance of Ni–B coatings. This improvement in corrosion behavior may be ascribed to the reduction in active area of Ni–B coatings by the presence of inactive CeO2 particles into Ni–B matrix.

Pristine and graphitized-MWCNTs as durable cathode-catalyst supports for PEFCs

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. Multi-walled carbon-nanotubes (MWCNTs) as cathode-catalyst support are found to enhance long-term stability of platinum catalyst (Pt) in relation to non-graphitic carbon. In addition, highly graphitic MWCNTs (G-MWCNTs) are found to be electrochemically more stable than pristine MWCNTs. This is because graphitic-carbon-supported-Pt (Pt/MWCNTs) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported-Pt (Pt/C) cathodes in PEFCs during accelerated stress-test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance, and charge-transfer resistance are monitored through cyclic voltammetry, cell polarization, and impedance measurements, respectively. The extent of crystallinity, namely amorphous or graphitic nature of the three supports, is examined by Raman spectroscopy. X-ray diffraction and transmission electron microscopy studies both prior and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/G-MWCNTs and Pt/MWCNTs cathodes in relation to Pt/C cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt particles. It is also found that with increasing degree of graphitization, the electrochemical stability for MWCNTs increases due to the lesser surface defects.

Graphitic Carbon as Durable Cathode‐Catalyst Support for PEFCs

AbstractLong‐term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon‐support corrosion. It is found that the use of graphitic carbon as cathode‐catalyst support enhances its long‐term stability in relation to non‐graphitic carbon. This is because graphitic‐carbon‐supported‐Pt (Pt/GrC) cathodes exhibit higher resistance to carbon corrosion in‐relation to non‐graphitic‐carbon‐supported‐Pt (Pt/Non‐GrC) cathodes in PEFCs during accelerated stress test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance and charge‐transfer resistance are monitored through cyclic voltammetry (CV), cell polarisation and impedance measurements, respectively. The degradation in performance of PEFC with Pt/GrC cathode is found to be around 10% after 70 h of AST as against 77% for Pt/Non‐GrC cathode. It is noteworthy that Pt/GrC cathodes can withstand even up to 100 h of AST with nominal effect on their performance. X‐ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy and cross‐sectional field‐emission scanning electron microscopy (FE‐SEM) studies before and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/GrC cathodes in relation to Pt/Non‐GrC cathodes, reflecting that graphitic carbon‐support resists carbon corrosion and helps mitigating aggregation of Pt‐particles.

Effect of serialized routing resources on the implementation area of datapath circuits on FPGAS

In this work, we investigate the effect of serialization on the implementation area of datapath circuits on FPGAs. With ever-increasing logic capacity, FPGAs are being increasingly used to implement large datapath circuits. Since datapath circuits are designed to process multiple-bit wide data, FPGA routing resources, which typically consist of a significant amount of FPGA area, are routinely being used to transport multiple-bit wide signals. Consequently, it is important to design efficient routing architectures for transporting multiple-bit wide signals on FPGAs. Serialization, where several bits of a signal are first time-multiplexed and then transported over a single wire, has been effectively used to increase the I/O bandwidth of FPGAs. Recent work has proposed to use serialization to increase the area efficiency of FPGA routing resources for transporting multiple-bit wide signals. Most of the work, however, has focused on circuit-level design issues. Little work has been done on the overall effect of serialization on the area efficiency of FPGAs. In this work, we investigate the overall effect of serialization on the area efficiency of FPGAs. We propose a detailed FPGA routing architecture, which contains a set of serialization routing resources, and its associated routing tool. Using the architecture and the tool, we measure the effect of serialization on active area and track count. We found that, for benchmarks that contain four-bit wide datapath circuits, serialization can achieve a maximum active area reduction of 6.4% and a routing track reduction of 29%.

Effects of Surface Irregularities and Interfacial Cracks on Polymer Electrolyte Fuel Cell Performance

The present study seeks to investigate the impact of surface irregularities and cracks at the catalyst layer (CL) and micro-porous layer (MPL) interface on the mass and electronic transport of polymer electrolyte fuel cells (PEFCs). Two different CLs were compared, i.e. one with negligible cracking and the other with high cracking (~6% active area reduction), under a combination of various operating conditions, including high/low relative humidity, and the presence of nitrogen/helium inert gases in the cathode inlet stream. A limiting current density analysis indicated that the cracked CL demonstrated a small increase in the Fickian diffusion of the reactants across the cathode electrode compared to the negligible-cracked CL case. Furthermore, the results from a relative humidity analysis showed that the protonic resistance in the CL might dominate the moderate current density region (0.15 A/cm2<current density<0.45 A/cm2). Finally, comparison of the cell performance for cracked and negligible-cracked CL cases suggests that the cracks may act as water pooling sites, which in turn, may enhance the performance in the high current density region (current density>0.45 A/cm2) due to the decreased water surface coverage and/or enhanced water removal.

Gully systems under undisturbed indigenous forest, East Coast Region, New Zealand

Gully erosion is commonly associated with agricultural landscapes where vegetation clearance and farming practices increase runoff, leading to fluvial incision. However, gully erosion can also occur in forests that have undergone some form of disturbance, either natural or resulting from human impacts. This paper reports on recent gully development within areas of undisturbed indigenous forest as a result of a high magnitude rainfall event on the East Coast of New Zealand's North Island. This region, through a combination of crushed and sheared rock types, steep topography, and tectonic and climatic setting, has high natural rates of erosion, exacerbated by European deforestation in the late 19th and early 20th centuries. Sequential air photographs, spanning a 58 year period between 1939 and 1997 were used to classify and document the growth and recovery of gully systems in the 14.1 km 2 headwaters of the Mangaoporo catchment. Following a severe cyclone in 1988, with a rainfall of 535 mm, there were 21 active gully systems within the indigenous forest. On photography prior to 1988 only four gully systems were present. During this period there were 8 major rainfall events (150–250 mm). Despite further 5 rainfall events of 150–250 mm between 1988 and 1997 all gully systems showed signs of recovery, with a combined reduction in active area of 37%. The nature and location of these features is strongly influenced by lithology (orientation of jointing and bedding), and to a topographic threshold defined by catchment slope and catchment area.

A sub-130-nm conditional keeper technique

Increasing leakage currents combined with reduced noise margins significantly degrade the robustness of wide dynamic circuits. In this paper, we describe two conditional keeper topologies for improving the robustness of sub-130-nm wide dynamic circuits. They are applicable in normal mode of operation as well as during burn-in test. A large fraction of the keepers is activated conditionally, allowing the use of strong keepers with leaky precharged circuits without significant impact on performance of the circuits. Compared to conventional techniques, up to 28% higher performance has been observed for wide dynamic gates in a 130-nm technology. In addition, the proposed burn-in keeper results in 64% active area reduction.

Double positive beveling: A better edge contour for high-voltage devices

A theoretical analysis is made of the field distribution near the surface of p-n-p structures with double positive edge geometry. This geometry offers in principle the possibility of avoiding the limitations and disadvantages inherent in the use of negative bevel angles. The results show that the reduction of the maximum field at the surface is not as easy as for the case of a simple positive bevel angle and that consequently the passivation of the surface may present more problems. Nevertheless, it is demonstrated that this geometry offers a number of great advantages and presents a real alternative for use in future high-voltage devices. A number of devices, dimensioned for a breakdown voltage of 6 kV, were made with this edge geometry. The measurements show that the reverse current corresponds to the thermally generated current in the space-charge layer and that no significant current flows at the surface. The breakdown voltage corresponds to the theoretical breakdown voltage in the bulk, unlike in the case of double negative beveling. The advantages of this geometry with respect to the conventional negative bevel angle are no significant reduction of active area, no dependence on the doping profile, and no limitation in voltage. A disadvantage, however, is the presence of higher fields at the surface.