IEEE Trans Research Articles

Direct observation of radio-frequency negative differential resistance in GaN-based single drift region IMPATT diodes

We report the direct observation of radio-frequency negative differential resistance, via on-wafer S-parameter measurements, in GaN-based impact ionization avalanche transit time (IMPATT) diodes. Clear signatures of reflection gain are observed from 18.7 to 30.6 GHz. These observations have been made possible by suppressing the reverse leakage current (and thereby parasitic shunt conductance) by optimization of the fabrication process, in conjunction with the use of pulsed measurements to suppress device self-heating. Consistent with avalanche-dominated behavior, the measured DC reverse bias current–voltage measurements show a positive temperature coefficient of breakdown. For the high-frequency on-wafer characterization, pulsed-bias S-parameter measurements with low (0.0067%) duty cycle were used to mitigate thermal effects. The measured avalanche frequency aligns closely with theoretical predictions based on Gilden and Hines' small signal model [Gilden and Hines, IEEE Trans. Electron Devices ED-13(1), 169–175 (1966)], measured impact ionization coefficients [Cao et al., Appl. Phys. Lett. 112(26), 262103 (2018)], and experimental saturation velocity measurements [Bajaj et al., Appl. Phys. Lett. 107(15), 153504 (2015)]; this excellent agreement confirms IMPATT operation and provides insights needed to further optimize device performance.

Using $$P_\tau $$ property for designing bent functions provably outside the completed Maiorana–McFarland class

AbstractIn this article, we identify certain instances of bent functions, constructed using the so-called $$P_\tau $$ P τ property, that are provably outside the completed Maiorana–McFarland ($${\mathcal{M}\mathcal{M}}^\#$$ M M # ) class. This also partially answers an open problem in posed by Kan et al. (IEEE Trans Inf Theory, https://doi.org/10.1109/TIT.2022.3140180, 2022). We show that this design framework (using the $$P_\tau $$ P τ property), can provide instances of bent functions that are outside the known classes of bent functions, including the classes $${\mathcal{M}\mathcal{M}}^\#$$ M M # , $${{\mathcal {C}}},{{\mathcal {D}}}$$ C , D and $${{\mathcal {D}}}_0$$ D 0 , where the latter three were introduced by Carlet in the early nineties. We provide two generic methods for identifying such instances, where most notably one of these methods uses permutations that may admit linear structures. For the first time, a set of sufficient conditions for the functions of the form $$h(y,z)=Tr(y\pi (z)) + G_1(Tr_1^m(\alpha _1y),\ldots ,Tr_1^m(\alpha _ky))G_2(Tr_1^m(\beta _{k+1}z),\ldots ,Tr_1^m(\beta _{\tau }z))+ G_3(Tr_1^m(\alpha _1y),\ldots ,Tr_1^m(\alpha _ky))$$ h ( y , z ) = T r ( y π ( z ) ) + G 1 ( T r 1 m ( α 1 y ) , … , T r 1 m ( α k y ) ) G 2 ( T r 1 m ( β k + 1 z ) , … , T r 1 m ( β τ z ) ) + G 3 ( T r 1 m ( α 1 y ) , … , T r 1 m ( α k y ) ) to be bent and outside $${\mathcal{M}\mathcal{M}}^\#$$ M M # is specified without a strong assumption that the components of the permutation $$\pi $$ π do not admit linear structures.

Fast decoding of lifted interleaved linearized Reed–Solomon codes for multishot network coding

AbstractMartínez-Peñas and Kschischang (IEEE Trans. Inf. Theory 65(8):4785–4803, 2019) proposed lifted linearized Reed–Solomon codes as suitable codes for error control in multishot network coding. We show how to construct and decode lifted interleaved linearized Reed–Solomon (LILRS) codes. Compared to the construction by Martínez-Peñas–Kschischang, interleaving allows to increase the decoding region significantly and decreases the overhead due to the lifting (i.e., increases the code rate), at the cost of an increased packet size. We propose two decoding schemes for LILRS that are both capable of correcting insertions and deletions beyond half the minimum distance of the code by either allowing a list or a small decoding failure probability. We propose a probabilistic unique Loidreau–Overbeck-like decoder for LILRS codes and an efficient interpolation-based decoding scheme that can be either used as a list decoder (with exponential worst-case list size) or as a probabilistic unique decoder. We derive upper bounds on the decoding failure probability of the probabilistic-unique decoders which show that the decoding failure probability is very small for most channel realizations up to the maximal decoding radius. The tightness of the bounds is verified by Monte Carlo simulations.

Compact high-Q Ka-band sapphire distributed Bragg resonator

In a class of high quality (Q-) factor dielectric resonators with low radiative losses, including popular whispering-gallery mode (WGM) resonators with high azimuthal mode numbers, due to high confinement of modal field in dielectric, the Q-factor is limited by the value of inverse dielectric loss tangent of dielectric material. Metal enclosures necessary for device integration only marginally affect the Q-factor while eliminating the residual radiative loss and allowing the optimization of input and output coupling. While very high Q-factors ∼200000 are available in sapphire WGM resonators in X-band, at millimeter wave frequencies increasing dielectric loss limits the Q-factor to much smaller values, e.g. ∼50000 and ∼25000 for quasi-TE and quasi-TM modes, correspondingly, at 36 GHz. The use of distributed Bragg reflection (DBR) principle allows to push modal energy outside dielectric while also isolating it from Joule losses in metallic enclosure walls. Very high Q∼600000>tgδ has been demonstrated in X-band [C. A. Flory and R. C. Taber, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 44, 486–495 (1997).] at the expense of impractically large dimensions. In this work, we report on the assembly and testing of a compact Ka-band sapphire distributed Bragg reflector cavity characterized with Q-factor seven times larger than one predicted by the material’s dielectric loss at the frequency of interest. An intrinsic Q-factor of ∼200000 is demonstrated at 36 GHz for the lowest order TM-mode of a sapphire DBR. The resonator has 50 cm3 volume, smaller than previously demonstrated DBRs.

Optimized method of thermoelectric cooler-based thermal management for improving the luminous efficacy of light-emitting diodes

We experimentally performed a method of active cooling for white LED that can reduce the temperature of the LED by using TEC for reducing the temperature of the LED board. The relation of LED board and input power for TEC was investigated to find out the optimized curve of LED board temperature and input power for TEC. Also, the TEC based cooling system was applied for RGBW LEDs. The obtained result is meaningful in LED thermal management, improving the lighting quality and increases the lifespan for both middle and high-power LED types. Full Text: PDF References E.F. Schubert, J.K. Kim, "Solid-State Light Sources Getting Smart", Science, 308, 1274 ¬(2005). CrossRef Q.K. Nguyen, "Emission spectrum modeling of white LEDs light source with using Gaussian function", Photonics Lett. Pol.,15(4), 54 (2023). CrossRef C.C. Sun, S.H. Ma, Q.K. Nguyen, "Advanced LED Solid-State Lighting Optics", Crystals, 10, 758 (2020). CrossRef S.P. Ying, H.K. Fu, W.F. Tang, R.C. Hong, "The Study of Thermal Resistance Deviation of High-Power LEDs", IEEE Trans. Electron Devices, 61, 2843 (2014). CrossRef K. Górecki, P. Ptak, "Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB", Energies, 14, 1286 (2021). CrossRef C.C. Sun, Q.K. Nguyen, T.X. Lee, S.K. Lin, C.S. Wu, T.H. Yang, Y.W.Yu. "Active thermal-fuse for stopping blue light leakage of white light-emitting diodes driven by constant current", Sci. Rep. 12, 12433 (2022). CrossRef Q.K. Nguyen, B. Glorieux, G. Sebe , T.H. Yang, Y.W. Yu , C.C. Sun, "Passive anti-leakage of blue light for phosphor-converted white LEDs with crystal nanocellulose materials", Sci Rep. 13, 13039 (2023). CrossRef N. Bădălan (Drăghici), P. Svasta, C. Marghescu, "A Method for Improving an Active Cooling Solution for LEDs ", IEEE 24th International Symposium for Design and Technology in Electronic Packaging (SIITME), Iași, Romania (2018). CrossRef A. Fan, R. Bonner, S. Sharratt, Y.S. Ju, "An innovative passive cooling method for high performance light-emitting diodes", 28th Annual IEEE Semiconductor Thermal Measurement and Management Symposium (SEMI-THERM), 319-324 (2012). CrossRef D.W. Kim, E. Rahim, A. Bar-Cohen, B. Han, "Direct Submount Cooling of High-Power LEDs", Compon. Packag. Technol., 33, 698 (2010). CrossRef N. Guan, N. Amador-Mendez, A. Kunti, A. Babichev, S. Das, A. Kapoor, N. Gogneau, J. Eymery, F.H. Julien, C. Durand, M. Tchernycheva, "Heat Dissipation in Flexible Nitride Nanowire Light-Emitting Diodes", Nanomater, 10, 2271 (2020). CrossRef S. Li, J.L. Liu, L. Ding, J.X. Liu, J. Xu, Y. Peng, M.X. Chen, "Active Thermal Management of High-Power LED Through Chip on Thermoelectric Cooler", IEEE Trans. Electron Devices, 68, 1753 (2021). CrossRef G.R. Sui, J.J. Chen, H. Ni, Y.Y. Ma, X.M. Gao, N. Wang, "Improvement of LED Performance With an Integrated Thermoelectric Cooling Package", IEEE Access, 8, 116535 (2020). CrossRef

Infinite families of minimal binary codes via Krawtchouk polynomials

AbstractLinear codes play a crucial role in various fields of engineering and mathematics, including data storage, communication, cryptography, and combinatorics. Minimal linear codes, a subset of linear codes, are particularly essential for designing effective secret sharing schemes. In this paper, we introduce several classes of minimal binary linear codes by carefully selecting appropriate Boolean functions. These functions belong to a renowned class of Boolean functions, namely, the general Maiorana–McFarland class. We employ a method first proposed by Ding et al. (IEEE Trans Inf Theory 64(10):6536–6545, 2018) to construct minimal codes violating the Ashikhmin–Barg bound (wide minimal codes) by using Krawtchouk polynomials. The lengths, dimensions, and weight distributions of the obtained codes are determined using the Walsh spectrum distribution of the chosen Boolean functions. Our findings demonstrate that a vast majority of the newly constructed codes are wide minimal. Furthermore, our proposed codes exhibit a significantly larger minimum distance, in some cases, compared to some existing similar constructions. Finally, we address this method, based on Krawtchouk polynomials, more generally, and highlight certain generic properties related to it. These general results offer insights into the scope of this approach.

On the Determination of Lagrange Multipliers for a Weighted LASSO Problem Using Geometric and Convex Analysis Techniques

Compressed Sensing (CS) encompasses a broad array of theoretical and applied techniques for recovering signals, given partial knowledge of their coefficients, cf. Candés (C. R. Acad. Sci. Paris, Ser. I 346, 589–592 (2008)), Candés et al. (IEEE Trans. Inf. Theo (2006)), Donoho (IEEE Trans. Inf. Theo. 52(4), (2006)), Donoho et al. (IEEE Trans. Inf. Theo. 52(1), (2006)). Its applications span various fields, including mathematics, physics, engineering, and several medical sciences, cf. Adcock and Hansen (Compressive Imaging: Structure, Sampling, Learning, p. 2021), Berk et al. (2019 13th International conference on Sampling Theory and Applications (SampTA) pp. 1-5. IEEE (2019)), Brady et al. (Opt. Express 17(15), 13040–13049 (2009)), Chan (Terahertz imaging with compressive sensing. Rice University, USA (2010)), Correa et al. (2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) pp. 7789–7793 (2014, May) IEEE), Gao et al. (Nature 516(7529), 74–77 (2014)), Liu and Kang (Opt. Express 18(21), 22010–22019 (2010)), McEwen and Wiaux (Mon. Notices Royal Astron. Soc. 413(2), 1318–1332 (2011)), Marim et al. (Opt. Lett. 35(6), 871–873 (2010)), Yu and Wang (Phys. Med. Biol. 54(9), 2791 (2009)), Yu and Wang (Phys. Med. Biol. 54(9), 2791 (2009)). Motivated by our interest in the mathematics behind Magnetic Resonance Imaging (MRI) and CS, we employ convex analysis techniques to analytically determine equivalents of Lagrange multipliers for optimization problems with inequality constraints, specifically a weighted LASSO with voxel-wise weighting. We investigate this problem under assumptions on the fidelity term Ax-b22\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left\\Vert Ax-b\\right\\Vert _2^2$$\\end{document}, either concerning the sign of its gradient or orthogonality-like conditions of its matrix. To be more precise, we either require the sign of each coordinate of 2(Ax-b)TA\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2(Ax-b)^TA$$\\end{document} to be fixed within a rectangular neighborhood of the origin, with the side lengths of the rectangle dependent on the constraints, or we assume ATA\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A^TA$$\\end{document} to be diagonal. The objective of this work is to explore the relationship between Lagrange multipliers and the constraints of a weighted variant of LASSO, specifically in the mentioned cases where this relationship can be computed explicitly. As they scale the regularization terms of the weighted LASSO, Lagrange multipliers serve as tuning parameters for the weighted LASSO, prompting the question of their potential effective use as tuning parameters in applications like MR image reconstruction and denoising. This work represents an initial step in this direction.

Event‐triggered bipartite consensus for multiagent systems with general linear dynamics: An integral‐type event‐triggered control

AbstractWe fill a gap in the proofs in the previous works (Wu X, Mu, X. Int J. Robust Nonlin Control. 2020;30:3753Ű3772; Zhang Z, Lunze J, Wang L. Int J Control. 2020;93:1005‐1014; Zhang Z, Wang L. J Robust Nonlin Control. 2018;28:4175Ű4187; Dai, M‐Z, Zhang C, Leung H, Dong P, Li B. IEEE Trans Syst, Man, Cybern: Syst. doi:10.1109/TSMC.2021.3119670) for the consensus using the integral‐based event‐triggered controls. More precisely, it was inferred for a Lyapunov function that is uniformly bounded by showing that is uniformly bounded for . However, this argument may fail without further information while the boundedness of is crucially used for applying Barbalat's lemma. The consequence of Barbalat's lemma is that which corresponds to the desired consensus result. To overcome this gap, Ma and Zhao (Inform Sci. 2018;457‐458:208‐221) put an extra condition about the boundedness of measurement error functions inside the proposed integral‐based event‐triggering protocol. In this article, we propose a new integral‐based event‐triggering protocol for bipartite consensus problems of the multi‐agent systems whose dynamics are described by general linear systems without adding the uniform boundedness of measurement error functions as (Ma Y, Zhao J. Inform Sci. 2018;457‐458:208‐221) did. Via our new integral‐based integral control strategy, we prove that the system achieves the bipartite consensus in asymptotic regime, and provide a complete solution of the freeness of both chattering and genuinely Zeno behaviors. Numerical results are provided supporting the effectiveness of the proposed controller.

Selective-Fading Multiple-Access MIMO Channels: Diversity-MultiplexingTradeoff and Dominant Outage Event Regions

We establish the optimal diversity-multiplexing (DM) tradeoff for coherent selective-fading multiple-access MIMO channels and provide corresponding code design criteria. As a byproduct, on the conceptual level, we find an interesting relation between the DM tradeoff framework and the notion of dominant error event regions, first introduced in the AWGN case by Gallager, IEEE Trans. IT, 1985. This relation allows us to accurately characterize the error mechanisms in MIMO fading multiple-access channels. In particular, we find that, for a given rate tuple, the maximum achievable diversity order is determined by a single outage event that dominates the total error probability exponentially in SNR. Finally, we examine the distributed space-time code construction proposed by Badr and Belfiore, Int. Zurich Seminar on Commun., 2008, using the code design criteria derived in the present paper.

(Invited) Silicon Quantum Dot Single-Electron Pumps for the Closure of the Quantum Metrology Triangle

Si quantum dot (QD) devices fabricated by MOSFET technology are promising for future and ultimate quantum electronics such as quantum electrical standards and quantum computers. We have developed Si tunable-barrier QD devices with a quasi-gate-all-around (GAA) nanowire [1], which are designed to be used as basic elements such as single-electron (SE) transfer devices and qubits; the precise manipulation of charges and their states are realized in the QDs. The device is especially suitable for high-speed tunable-barrier SE pumps driven at GHz frequencies [2,3] which can generate an electric current via a single QD precisely equal to the elementary charge times the driving frequency and thereby are promising for quantum current standards [4].To achieve a high accuracy using tunable-barrier SE pumps [5-7], proper designs of device structures are required to secure robust charge quantization. The potential shape of the QD and the entrance tunnel barrier [8] are critical parameters to dictate the pump accuracy because they determine the charging energy and energy filtering effect during SE capture into the QD. Furthermore, deep understanding of electron dynamics such as mechanism crossover of the dynamical charge quantization process [9] and quantum nonadiabatic excitation [10]/electron-phonon relaxation inside the QD are important to get optimal accuracy and extend the frequency breakdown of SE pumps. We have recently developed a device simulator of Si GAA-nanowire SE pumps [11], which is a useful tool to find optimal design and control parameters in all the above-mentioned respects.One of the long-desired targets of SE pumps is to close the quantum metrology triangle (QMT) [12] by checking the consistency among three quantum electrical standards: the SE current standard, the quantum Hall resistance standard, and Josephson voltage standard (JVS). The Japanese QMT project [13] has aimed to conduct the QMT experiment with sub-ppm uncertainty in a single dilution refrigerator by placing all the quantum electric standards inside it. Our key approaches are to use quantum Hall array resistance (QHAR) [14] and parallelized Si SE pumps, which provide higher resistance and current respectively, making the generated voltage more easily compared to JVS. In the project we have succeeded in developing a current-reversal technique with electromechanical relays to cancel out the drift and low frequency noise from various sources in the measurement setup, and applying it to high accuracy measurement of current delivered by a Si SE pump [15]. We have also recently performed a comparison measurement of two Si SE pump operated in parallel and thereby have confirmed a sub-ppm level accuracy [16]. All these progresses will lead to a more precise closure of QMT at deep sub-ppm level in the new future. Si MOSFET technology continues to expand its versatility into quantum electronics technology. This work was supported by JSPS KAKENHI Grant Number JP18H05258. A. Fujiwara et al., Appl. Phys. Lett. 84, 1323 (2004); Appl. Phys. Lett. 88 053121 (2006).A. Fujiwara et al., Appl. Phys. Lett. 92, 042102 (2008)G. Yamahata et al., Appl. Phys. Lett. 106, 023112 (2015).N.-H. Kaneko et al., Meas. Sci. Technology 27 032001 (2016).B. Kaestner and V. Kashcheyevs, Rep. Prog. Phys. 78, 103901 (2015).G. Yamahata et al., Appl. Phys. Lett. 109, 013101 (2016).S. P. Giblin et al., Metrologia 56, 044004 (2019).N. Johnson et al., Appl. Phys. Lett. 115, 162103 (2019).G. Yamahata et al., Phys. Rev. B 103, 245306 (2021).G. Yamahata et al., Nat. Nanotechnol. 14, 1019 (2019).A. Fujiwara et al., in the Conference on Precision Electromagnetic Measurements (CPEM 2022).F. Piquemal and G. Genevès, Metrologia 37, 207 (2000).https://www.jsps.go.jp/file/storage/grants/j-grantsinaid/12_kiban/ichiran_30/e-data/h_30_eng_18h05258.pdf; http://www.brl.ntt.co.jp/people/afuji/kakenS/ (only in Japanese).T. Oe et al., IEEE Trans. Instrum. Meas. 66, 1475 (2017).S. Nakamura et al., IEEE Trans. Instrum. Meas, under review.S. Nakamura et al., in preparation.

Evaluation of Anisotropic Biaxial Stress in Extremely-Thin Body (100) Silicon-Germanium-on-Insulator p-Type Metal-Oxide-Semiconductor Field-Effect-Transistor by Oil-Immersion Raman Spectroscopy

Background and ObjectiveSilicon germanium (SiGe)-on-insulator (SGOI) p-MOSFETs are expected for obtaining low power consumption and high current drive of CMOS since SiGe has higher hole career mobility than Si and the compressive strain can be induced in the SiGe channel without complicated heterostructures. In addition, the buried oxide between the Si substrate and the SiGe layer realizes suppression of leak current, and an extremely thin body (ETB) SGOI prevents short-channel effects. Strain engineering is important for improving the performance of p-MOSFETs because the hole mobility increases due to the compressive strain in the channel region. In previous studies, we have reported that anisotropic strain in ETB GOI channels of p-MOSFET improved electrical properties [1]. However, there are few reports regarding the detailed stress evaluation in ETB SGOI p-MOSFETs. The strain state has changed complicatedly by the SiGe device process. Therefore, a detailed stress measurement is indispensable to determine career mobility enhancement in the actual channel fabrication. In this study, we evaluated the anisotropic biaxial stress in the channel region of the ETB (100) SGOI p-MOSFETs by oil-immersion Raman spectroscopy.Experiments We prepared (100) SGOI p-MOSFETs along <110> with a channel thickness of approximately 10 nm by applying the Ge condensation process with slow cooling on the 60 nm-thick Si0.75Ge0.25 films epitaxially grown on SOI substrates with 10 nm-thick superficial Si layer [2]. We used the Ge condensation process that combined oxidation and intermixing annealing in order to suppress strain relaxation in the Ge-rich region [3] and obtained Ge-rich SiGe layer (Ge fraction: from 65 to 70%). For the evaluation of anisotropic biaxial stress in the SiGe channel region, we measured longitudinal optical (LO) and transverse optical (TO) phonon modes of Raman spectra for Ge-Ge vibration mode derived from SiGe by using oil-immersion Raman spectroscopy. In the oil-immersion Raman measurements, the wavelength of the excitation light source was 532 nm, the laser power at the sample surface was less than 1 mW, and the focal length of the spectrometer was 2,000 mm. The numerical aperture of the oil-immersion lens was 1.4, and the reflective index of oil was 1.5. We measured p-MOSFETs with different channel widths to examine the channel width dependence.Results and DiscussionFigure 1(a) and (b) show the Raman spectra of the LO and TO phonon modes obtained from the SiGe channel region at channel width (Wch) = 738 nm, respectively. We observed that Raman peaks of LO phonon mode shifted toward the higher wavenumber side compared to the Raman peak of strain-free SiGe. These results suggest that the high compressive strain is induced in the SiGe channel.Figure 1(c) shows the calculated transverse stress (σxx) and longitudinal stress (σyy) of the samples using LO and TO Raman shift for four different channel widths under the assumption of the anisotropic biaxial stress and Ge fraction 68% in the SiGe layer. From Fig. 1(c), we observed transverse stress (σxx) decreases with narrowing channel width. On the other hand, the longitudinal stress (σyy) did not significantly change regardless of channel width. These results suggest that the strain states in the SiGe channel region became closer to the uniaxial strain with narrowing the channel width. These changes are in good agreement with the previous electrical characteristics studies of the GOI p-MOSFETs [1], and it is expected that the compressive strain enhances the hole mobility in the ETB SGOI p-MOSFETs as well.AcknowledgementsThis work was supported by JSPS KAKENHI Grant Number 22H00208, Japan. A part of this work was conducted at Takeda Sentanchi Supercleanroom, The University of Tokyo, supported by "Nanotechnology Platform Program" of MEXT, Japan, Grant Number JPMXP09F-20-UT-0007. Reference [1] C. -T. Chen et al., IEEE Trans. Electron Devices 69, 1 (2022).[2] C. -T. Chen et al., Proc. IEEE Symp. VLSI Technology (2021).[3] K. -W. Jo et al., Appl. Phys. Lett. 114, 062101 (2019). Figure 1

(Invited) Switching Characteristics of GaN Power Transistors

A shorter switching time is one of the key advantages of GaN power devices over Si IGBTs. [1] In this paper, we report on the simulation of GaN power transistor switching and investigate the effect on the switching time novel design approaches ranging from the gate edge engineering (beyond just using field plates [2] for optimizing the voltage distribution in the drain-to-gate spacing to using the quantum well channel designs [3] that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of high mobility in the device channel. We also report on the effect of a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges on switching time.[4] Additional contacts in the drain-to-gate spacing for the field control and variable doping implants could also decrease the switching time. Further optimization could be achieved with the perforated channel designs [5] decreasing the parasitic series resistance and improving the heat dissipation.[1] A. Tüysüz, R. Bosshard, and J. W. Kolar, erformance Comparison of a GaN GIT and a Si IGBT for High-Speed Drive Applications, Proceedings of the International Power Electronics Conference - ECCE Asia (IPEC 2014), Hiroshima, Japan, May 18-21, 2014[2] S. Karmalkar, M. S. Shur, G. Simin and M. A. Khan, Field-Plate Engineering for Heterostructure Field Effect Transistors, IEEE Trans. ED, 52, 12, pp. 2516- 2532, December (2005)[3] M. Dyakonov and M. S. Shur, Consequences of Space Dependence of Effective Mass in Heterostructures, J. Appl. Phys. Vol. 84, No. 7, pp. 3726-3730, October 1 (1998)[4] G. Simin, M. Shur and R. Gaska, SETI-0070: Semiconductor device with low-conducting field-controlling element App. No 13/396,059, November 19, 2013 as US Patent No. 8,586,997[5] G. Simin, M. Gaevski, M. Shur, R. Gaska, Perforated Channel Field Effect Transistor, US patent 9,467,105, October 11, 2016

No Eleventh Conditional Ingleton Inequality

A rational probability distribution on four binary random variables X , Y , Z , U is constructed which satisfies the conditional independence relations [ X ⊥ ⊥ Y ] , [ X ⊥ ⊥ Z | U ] , [ Y ⊥ ⊥ U | Z ] and [ Z ⊥ ⊥ U | X Y ] but whose entropy vector violates the Ingleton inequality. This settles a recent question of Studený (IEEE Trans. Inf. Theory vol. 67, no. 11) and shows that there are, up to symmetry, precisely ten inclusion-minimal sets of conditional independence assumptions on four discrete random variables which make the Ingleton inequality hold. The last case in the classification of which of these inequalities are essentially conditional is also settled.

Special issue linStat: sequential projection pursuit

Friedman and Tukey (1974, A projection pursuit algorithm for exploratory data analysis. IEEE Trans Comput. C-23:881–890), in their seminal paper, coined the term projection pursuit to denote a sequential classification method where data are projected onto the direction which best separates a cluster from the others. The detected cluster is then removed from the data and the procedure is repeated until no clusters are left. This paper implements their approach by an iterative algorithm based on kurtosis minimization and k-means clustering. The algorithm is initialized with the eigenvector associated with the smallest positive eigenvalue of the standardized fourth moment. The iterative step simplifies the multivariate minimization procedure to a bivariate one, which admits an analytical solution. The classification step is a simplified version of k-means clustering, where the data are unidimensional and only two groups are sought. The practical usefulness and the asymptotic properties of the proposed method are illustrated with simulated data.

Self-consistent calculations of the electric charge, ion drag force, and the drift velocity of spherical grains using Langevin dynamics and comparisons against canonical experiments

We present trajectory simulation-based modeling to capture the interactions between ions and charged grains in dusty or complex plasmas. Our study is motivated by the need for a self-consistent and experimentally validated approach for accurately calculating the ion drag force and grain charge that determine grain collective behavior in plasmas. We implement Langevin dynamics in a computationally efficient predictor–corrector approach to capture multiscale ion and grain dynamics. Predictions of grain velocity, grain charge, and ion drag force are compared with prior measurements to assess our approach. The comparisons reveal excellent agreement to within ±20% between predicted and measured grain velocities [Yaroshenko et al., Phys. Plasmas 12, 093503 (2005) and Khrapak et al., Europhys. Lett. 97, 35001 (2012)] for 0.64, 1.25 μm grains at ∼20−500 Pa. Comparisons with the measured grain charge [Khrapak et al., Phys. Rev. E 72, 016406 (2005)] under similar conditions reveal agreement to within ∼20% as well. Measurements of the ion drag force [Hirt et al., Phys. Plasmas 11, 5690 (2004); IEEE Trans. Plasma Sci. 32, 582 (2004)] are used to assess the viability of the presented approach to calculate the ion drag force experienced by grains exposed to ion beams of well-defined energy. Excellent agreement between calculations and measurements is obtained for beam energies &amp;gt;10 eV, and the overprediction below 10 eV is attributed to the neglect of charge exchange collisions in our modeling. Along with critical assessments of our approach, suggestions for future experimental design to probe charging of and momentum transfer onto grains that capture the effect of space charge concentration and external fields are outlined.

Gyrification abnormalities in young adult presymptomatic carriers of frontotemporal lobar degeneration mutations

AbstractBackgroundPresymptomatic C9orf72 expansion carriers show regions of low local gyrification index (lGI) as early as their thirties (Caverzasi et al. JNNP 2019) and regions of gyrification decline have been reported (van Veenhuijzen et al. Ann Neurol 2022). These findings raise the question as to whether abnormal gyrification represents a neurodevelopmental difference or early neurodegeneration in frontotemporal lobar degeneration (FTLD) mutation carriers. Yet, previous studies focusing on young adults is lacking and no study has explored gyrification in the two other common FTLD mutations, GRN and MAPT. Here, we analyzed lGI in young adult presymptomatic FTLD mutation carriers.MethodLGI quantifies buried cortex within the sulcal folds compared to the visible cortex on the outer surface, with larger values indicating more folding (Schaer et al. IEEE trans med imaging 2008). Mean lGI values, as measured by a parcel‐wise analysis implemented in FreeSurfer v.6.0, were compared between 31 presymptomatic (preSx) carriers (12 C9orf72, 13 MAPT, 6 GRN, mean age: 25.2 ± 3.91 years) and 28 demographically‐matched healthy controls (HC: mean age: 25.6 ± 3.8 years). We used ANCOVA to compare all presymptomatic carriers combined (preSxAll) and HC to identify regions with significant lGI differences regressing age, sex, education, handedness, total intracranial volume and scanner type as nuisance covariates. Significant group differences were analyzed by Dunnett’s post‐hoc tests between each mutation subgroup and HC (p&lt;0.05).ResultCompared to HC, preSxAll had higher mean gyrification in the right caudal (F = 5.07, p = 0.03) and rostral anterior cingulate (F = 6.22, p = 0.17), and lower lGI in the left middle temporal gyrus (F = 4.22, p = 0.046). Within these regions, post‐hoc analyses showed that preSx GRN had greater gyrification in the right caudal anterior cingulate (t = 2.57, p = 0.039, 95% CI = [0.005, 0.248]) and preSx C9orf72 had lower lGI in the left middle temporal gyrus (t = ‐3.14, p = 0.009, 95% CI = [‐0.37, ‐0.04]) vs. HC.ConclusionYoung adult FTLD mutation carriers displayed higher gyrification in the right anterior cingulate and lower gyrification in the left middle temporal gyrus compared to HC. Future studies in children will confirm the extent to which these gyrification abnormalities represent neurodevelopmental differences.

A family of tests for trend change in failure rate function with right censored data

In this paper we extend the family of test proposed by Majumder and Mitra [Detecting trend change in failure functions-an L-statistic approach. Stat Pap. 2019;62:31–52. doi: 10.1007/s00362-018-01074-8] for testing exponentiality against bathtub (BT) failure rate (upside down bathtub (UBT)) to randomly right censored case. We derive the asymptotic distribution of the test statistic and using Monte Carlo simulation we obtain the empirical powers for certain alternative distributions. As a special case the asymptotic distribution of the test statistic proposed by Park [Testing whether failure rate changes its trend. IEEE Trans Reliab. 1988;37(4):375–378. doi: 10.1109/24.9842] is obtained. Finally some examples of real life data are given for illustrative purpose.

Physically constrained learning of MOS capacitor electrostatics

In recent years, neural networks have achieved phenomenal success across a wide range of applications. They have also proven useful for solving differential equations. The focus of this work is on the Poisson–Boltzmann equation (PBE) that governs the electrostatics of a metal–oxide–semiconductor capacitor. We were motivated by the question of whether a neural network can effectively learn the solution of PBE using the methodology pioneered by Lagaris et al. [IEEE Trans. Neural Netw. 9 (1998)]. In this method, a neural network is used to generate a set of trial solutions that adhere to the boundary conditions, which are then optimized using the governing equation. However, the challenge with this method is the lack of a generic procedure for creating trial solutions for intricate boundary conditions. We introduce a novel method for generating trial solutions that adhere to the Robin and Dirichlet boundary conditions associated with the PBE. Remarkably, by optimizing the network parameters, we can learn an optimal trial solution that accurately captures essential physical insights, such as the depletion width, the threshold voltage, and the inversion charge. Furthermore, we show that our functional solution can extend beyond the sampling domain.

Constructions and equivalence of Sidon spaces

Sidon spaces have been introduced by Bachoc et al. (in: Mathematical Proceedings of the Cambridge Philosophical Society, Cambridge University Press, 2017) as the q-analogue of Sidon sets. The interest on Sidon spaces has increased quickly, especially after the work of Roth et al. (IEEE Trans Inform Theory 64(6):4412–4422, 2017), in which they highlighted the correspondence between Sidon spaces and cyclic subspace codes. Up to now, the known constructions of Sidon Spaces may be divided in three families: the ones contained in the sum of two multiplicative cosets of a fixed subfield of mathbb {F}_{q^n}, the ones contained in the sum of more than two multiplicative cosets of a fixed subfield of mathbb {F}_{q^n} and finally the ones obtained as the kernel of subspace polynomials. In this paper, we will mainly focus on the first class of examples, for which we provide characterization results and we will show some new examples, arising also from some well-known combinatorial objects. Moreover, we will give a quite natural definition of equivalence among Sidon spaces, which relies on the notion of equivalence of cyclic subspace codes and we will discuss about the equivalence of the known examples.

Adaptive event‐triggered efficient output feedback model predictive control for networked interval type‐2 T–S fuzzy system with data loss

AbstractThis article is concerned with the adaptive event‐triggered (AET) efficient output feedback model predictive control (EOFMPC) for a set of nonlinear networked interval type‐2 Takagi–Sugeno (IT2 T–S) fuzzy control systems with data loss. For the reduction in data transmission burden and required control performance, the AET scheme and a novel dynamic triggering law are introduced jointly in this article. The efficient model predictive control approach as in Kouvaritakis et al. (IEEE Trans Automat Contr. 2000;45(8):1545–1549.), which transfers the main part of online optimization work to offline stage by incorporating an extra perturbation into the fixed feedback law, is extended to networked control systems to reduce their online computational burden. This article proposes the following: (1) an unified closed‐loop model representation of data loss process and IT2 T–S fuzzy nonlinearities is established under the framework of EOFMPC, which explicitly considers the AET condition; (2) a new design method for the state observer gain is presented based on an ellipsoidal invariant set, so that a smaller bound of estimation error can be obtained through an extra optimization problem; (3) some optimization problems are formulated to design the proposed controllers, and the corresponding EOFMPC algorithm is summarized; (4) by means of the extra matrix partition technique, the online optimization problem subject to one ellipsoidal constraint is transformed into a novel convex form to solve the uncertainty of the estimation error. A simulation example and a few comparative simulation experiments illustrate the effectiveness and availability of the aforementioned approach.