Hybrid power management in real time embedded systems: an interplay of DVFS and DPM techniques

Energy-aware scheduling of real time applications over multiprocessor systems is considered in this paper. Early research reports that while various energy-saving policies, for instance Dynamic Power Management (DPM) and Dynamic Voltage & Frequency scaling (DVFS) policies, perform well individually for a specific set of operating conditions, they often outperform each other under different workload and/or architecture configuration. Thus, no single policy fits perfectly all operating conditions. Instead of designing new policies for specific operating conditions, this paper proposes a generic power/energy management scheme that takes a set of well-known existing (DPM and DVFS) policies, each of which performs well for a set of conditions, and adapts at runtime to the best-performing policy for any given workload. Experiments are performed using state-of the-art DPM and DVFS policies and the results show that our proposed scheme adapts well to the changing workload and always achieves overall energy savings comparable to that of best-performing policy at any point in time.     

BDD Based Procedures for a Theory of Equality with Uninterpreted Functions

The logic of equality with uninterpreted functions has been proposed for verifying abstract hardware designs. The ability to perform fast satisfiability checking over this logic is imperative for such verification paradigms to be successful. We present symbolic methods for satisfiability checking for this logic. The first procedure is based on restricting analysis to finite instantiations of the variables. The second procedure directly reasons about equality by introducing Boolean-valued indicator variables for equality. Theoretical and experimental evidence shows the superiority of the second approach.     

On the Security of A Secure Anonymous Identity-Based Scheme in New Authentication Architecture for Mobile Edge Computing

With the rapidly growing user experience and traffic growth requirements in the Mobile Edge Computing (MEC) environment, the conventional security protocols are no longer capable of meeting the modern demand. In order to cope with this demand, novel security solution such as identity-based cryptography, which does not require complex calculations, has attracted great attention from the research community. Recently, Li et al. (IEEE Syst J 1937–9234, 2021, https://doi.org/10.1109/JSYST.2020.2979006) devised an identity-based protocol for the MEC environment. They claimed that their protocol offers efficient and secure communication among the involved entities. Nevertheless, after performing a careful analysis of their protocol, we discovered that their protocol is vulnerable to MEC server and mobile user impersonation attacks. Similarly, their protocol has no provision of mobile user anonymity and untraceability. Furthermore, it has incorrectness in the authentication phase. Given these limitations, we have suggested a suitable remedy, which counters all the said vulnerabilities and limitations.

     

Bat algorithm–based beamforming for mmWave massive MIMO systems

In this paper, an optimized analog beamforming scheme for millimeter‐wave (mmWave) massive MIMO system is presented. This scheme aims to achieve the near‐optimal performance.by searching for the optimized combination of analog precoder and combiner. In order to compensate for the occurrence of attenuation in the magnitude of mmWave signals, the codebook‐dependent analog beamforming in conjunction with precoding at transmitting end and combining signals at the receiving end is utilized. Nonetheless, the existing and traditional beamforming schemes involve a more difficult and complicated search for the optimal combination of analog precoder/combiner matrices from predefined codebooks. To solve this problem, we have referred to a modified bat algorithm to find the optimal combination value. This algorithm will explore the possible pairs of analog precoder/combiner as a way to come up with the best match in order to attain near‐optimal performance. The analysis shows that the optimized beamforming scheme presented in this paper can improve the performance that is very close to the beam steering benchmark that we have considered.     

Novel analysis and optimization of gm-boosted common-gate UWB LNA

This paper focuses on the design optimization of g_m-boosted common gate (CG) CMOS low-noise amplifier (LNA) for ultra-wideband (UWB) wireless technology. In this regard, a detailed novel analysis of the UWB g_m-boosted CG amplifier topology is presented, which includes the finite g_ds (=1/r_eds) effects. For UWB systems, signal-to-noise ratio (SNR) can be defined as the matched filter bound (MFB). Using this definition, the noise performance of the UWB CG LNA in the presence of the g_m-boosting gain and the input noise-matching network are analyzed. It is found that the optimal noise factor of the UWB LNA collapses to the published narrowband g_m-boosted CG LNA noise factor when an assumption of narrowband is applied. It is also proved that the noise performance of the g_m-boosted UWB CG LNA is independent of the bandwidth of the input UWB signal. A new technique is presented for the design of optimal noise-matching network using passive components at the input of the UWB CG LNA. In this regard, role of the g_m-boosting stage and its effect on the SNR and the gain of the overall system are analyzed, and, in addition, its non-idealities are simulated in detail.     

A 4 mW 3–5 GHz current reuse g<Subscript>m</Subscript>-boosted short channel common-gate CMOS UWB LNA

A novel architecture is presented to optimize the noise performance and the power consumption of the transconductance ‘g_m’ boosted common-gate (CG) ultrawideband (UWB) low-noise amplifier (LNA), operating in the 3–5 GHz range, by employing current reuse technique. This proposed CG LNA utilizes a common source (CS) amplifier as the g_m-boosting stage and the bias current is shared between the g_m-boosting stage and the CG amplifying stage. The LNA circuit also utilizes the short channel conductance g_ds in conjunction with an LC T-network to further reduce the noise figure (NF). The proposed LNA architecture has been fabricated using the 130 nm IBM CMOS process. The LNA achieved input return loss (S₁₁) of −8 to −10 dB, and, output return loss (S₂₂) of −12 to −14 dB, respectively. The LNA exhibits almost flat forward voltage gain (S₂₁) of 13 dB, and reverse isolation (S₁₂) of −62 to −49 dB, with a NF ranging between 3.8 and 4.6 dB. The measurements indicate an input-referred third order intercept point (IIP3) of −6.1 dBm and an input-referred 1-dB compression point (ICP_1dB) of −15.4 dBm. The complete chip draws 4 mW of DC power from a 1.2 V supply.     

Sulfonated poly(sulfone‐pyridine‐amide)/sulfonated polystyrene/multiwalled carbon nanotube‐based fuel cell membranes

In this study, aromatic sulfonated poly(sulfone‐pyridine‐amide) (S‐PSPA) has been prepared via polycondensation of sulfonated monomer 1‐(4‐thiocarbamoylaminophenyl‐sulfonylphenyl)thiourea and 2,6‐pyridinedicarboxylic acid at high temperature. Mechanically robust and thermally stable hybrid membranes were prepared using non‐functional and functional multiwalled carbon nanotube (MWCNT) i.e., S‐PS/S‐PSPA/MWCNT‐NF and S‐PS/S‐PSPA/MWCNT via solution blending. Field emission scanning electron microscopy exhibited porous membrane structure for 0.1–0.5 wt% nanotube loading, whereas well‐aligned functional MWCNT were observed in 1 wt% loaded sample. Increasing the functional nanotube content from 0.1 to 1 wt% increased tensile strength of functional S‐PS/S‐PSPA/MWCNT hybrids from 62.19 to 65.29 MPa compared with non‐functional hybrid (53.34 MPa) and neat S‐PS/S‐PSPA. 10% decomposition temperature of S‐PS/S‐PSPA/MWCNT 0.1–1 was in the range 491–502°C, while S‐PS/S‐PSPA/MWCNT‐NF showed relatively lower thermal stability (T₁₀ 489°C). Glass transition temperature of functional S‐PS/S‐PSPA/MWCNT was also higher (201–243°C) relative to S‐PS/S‐PSPA/MWCNT‐NF (194°C). Furthermore, functional MWCNT‐based membranes had higher ion exchange capacity (IEC) 3.2–3.6 mmol/g and lower activation energies (95–36 kJ/mol). Novel functional membranes also revealed high proton conductivity 1.68–2.55 S/cm in a wide range of humidity at 80°C higher than that of perfluorinated Nafion® membrane (1.1 ×10^?1 S/cm) at 80°C (94% RH). POLYM. ENG. SCI., 55:1776–1786, 2015. © 2014 Society of Plastics Engineers     

Electrochemical evaluation of mixed ionic electronic perovskite cathode LaNi1-xCoxO3-δ for IT-SOFC synthesized by high temperature decomposition

The cobalt doped perovskite cathode material LaNi_1-xCo_xO_3-δ (x = 0.4, 0.6, 0.8) synthesized by cost effective high temperature decomposition is investigated as mixed ionic electronic conductor (MIEC) for intermediate temperature solid oxide fuel cell (IT-SOFC). LaNiO₃ is known for its high electronic conductivity and to introduce more oxygen vacancies for enhancing its ionic conductivity, Ni at B site is substituted by Co. XRD analysis showed perovskite structure for all samples with no additional phases, which was also confirmed by FTIR results. Microstructure analysis revealed well connected and porous structure for LaNi_1-xCo_xO_3-δ (x = 0.6) compared to other compositions. The elemental analysis using EDX confirmed presence of lanthanum, nickel, and cobalt within all samples. No prominent weight loss was observed during TGA analysis. The highest value of conductivity was obtained for LaNi_1-xCo_xO_3-δ (x = 0.6) due to its porous and networked structure of sub micrometric grains. The superior performance is attained for the cell based on LaNi_1-xCo_xO_3-δ (x = 0.6) cathode with maximum power density of 0.45 Wcm^?2 compared to other composition which can be attributed to its well connected and porous structure that caused enhanced electrochemical reaction at triple phase boundary (TPB). It was therefore deduced that LaNi_1-xCo_xO_3-δ (x = 0.6) is promising composition to be used as MIEC cathode for IT-SOFC.     

Restabilization in structures susceptible to localized buckling: an approximate method for the extended post-buckling regime

Localized buckling in structures has been extensively studied in the context of simple nonlinear models which capture the essence of the phenomenon near the lowest critical load. In this study we apply a non-periodic Rayleigh–Ritz procedure to track localizations into the far post-buckling regime where the structure regains stability after the initial destabilization. The results are compared against independent numerical solutions and good agreement is found.