6,906 research outputs found
q-Differential equations for q-classical polynomials and q-Jacobi-Stirling numbers
Get PDFWe introduce, characterise and provide a combinatorial interpretation for the so-called q-Jacobi–Stirling numbers.
This study is motivated by their key role in the (reciprocal) expansion of any power of a second order
q-differential operator having the q-classical polynomials as eigenfunctions in terms of other even order operators,
which we explicitly construct in this work. The results here obtained can be viewed as the q-version of
those given by Everitt et al. and by the first author, whilst the combinatorics of this new set of numbers is a
q-version of the Jacobi–Stirling numbers given by Gelineau and the second author
Tobin's Q and Financial Policy
Get PDFRecent research in macroeconomics has emphasized the importance of linking the financial and real sectors and the need for working with optimizing models. Tobin’s Q model of investment would appear to provide a framework that can satisfy these two criteria. In contrast to the original presentation of the Q model, the formal development has not recognized that the firm actively participates in a number of financial markets; in this broader context, we show that Q is likely to be an uninformative and possibly misleading signal for investment expenditures . We then endeavor to turn this negative theoretical result to positive advantage in resolving a number of empirical problems with Q models, but the modifications dictated by the theory receive little support from the data.
A Wideband 2x13-bit All-Digital I/Q RF-DAC
No full textThis paper presents a wideband 2 13-bit in-phase/quadrature-phase (I/Q) RF digital-to-analog converter-based all-digital modulator realized in 65-nm CMOS. The isolation between I and Q paths is guaranteed employing 25% duty-cycle differential quadrature clocks. With a 1.3-V supply and an on-chip power combiner, the digital I/Q transmitter provides more than 21-dBm RF output power within a frequency range of 1.36–2.51 GHz. The peak RF output power, overall system, and drain efficiencies of the modulator are 22.8 dBm, 34%, and 42%, respectively. The measured static noise floor is below 160 dBc/Hz. The digital I/Q RF modulator demonstrates an IQ image rejection and local oscillator leakage of 65 and 68 dBc, respectively. It could be linearized using either of the two digital predistortion (DPD) approaches: a memoryless polynomial or a lookup table. Its linearity is examined using single-carrier 4/16/64/256/1024 quadrature amplitude modulation (QAM), as well as multi-carrier 256-QAM orthogonal frequency-division multiplexing baseband signals while their related modulation bandwidth can be as high as 154 MHz. Employing DPD improves the third-order intermodulation product (IM3) by more than 25 dB, while the measured error vector magnitude for a “single-carrier 22-MHz 64-QAM” signal is better than 28 dB.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
All-Digital I/Q RF-DAC
No full textDue to the severe cost pressure of consumer electronics, a migration to an advanced nanoscale CMOS processes, which is primarily developed for fast and low-power digital circuits operating at low supply voltages, is necessary, but it forces wireless RF transceivers to exploit more and more digital circuitry. These basic CMOS properties tend to coerce the design of wireless functions towards the digital domain where transistors are utilized as switches rather than current sources. Within the past decade, there have been tremendous efforts towards implementing fully-digital or digitally-intensive RF transmitters in which they demonstrate transmitter designs that operate from baseband up to the pre-power amplifier (PA) stage entirely in the digital domain. In view of this digitalization, the RF transmitter modulator, being the nearest to the antenna as it converts digital baseband modulation samples into an RF waveform, is considered the most critical building block of the transmitter, and it can be in the form of either a polar, Cartesian (I/Q), or an outphasing topology. For wide modulation bandwidths, due to their direct linear summation of the in-phase (I) and quadrature-phase (Q) signals and thus the avoidance of the bandwidth expansion, Cartesian modulators are substantiated as the most appropriate choice over their polar or outphasing counterparts. Since the effective modulating sample resolution is the utmost important parameter as it directly impacts the achievable dynamic range, linearity, error vector magnitude (EVM), noise floor, and out-of-band spectral emission, this thesis proposes a wideband, high-resolution, all-digital orthogonal I/Q radio-frequency digital-to-analog (RF-DAC). Chapter 1 briefly provides an overview of the conventional RF radio building blocks. It is discussed that contemporary RF transceivers must support most of multi-mode/multiband communication standards such as Wi-Fi, Bluetooth, and Fourth Generation (4G) of 3GPP cellular. In Chapter 2, four types of RF transmitter architectures have been briefly described. The analog I/Q modulators are the most straightforward and widely employed RF transmitters. They are later replaced by analog polar counterparts to address their poor power efficiency and noise performance. On the other hand, in the analog polar RF transmitters, their related amplitude and phase signals must be aligned or spectral regrowth is inevitable. Utilizing digitally intensive polar RF transmitters mitigates the latter alignment issue. Nonetheless, polar transmitters suffer from an additional issue that is related to their nonlinear conversion of in-phase and quadrature-phase signals into the amplitude and phase representation. Therefore, the polar RF transmitters are not able to manage very large baseband bandwidth of the most stringent communication standards, therefore, reusing I/Q modulators based on digitally intensive implementation appears to be a reasonable approach to resolve this issue. The digital I/Q RF transmitters, however, suffer again from inadequate power efficiency. Moreover, the combination of in-phase and quadrature phase paths must be orthogonal to produce an undistorted-upconverted-modulated RF signal. In Chapter 3, a novel all-digital I/Q RF modulator is described. Employing an upconverting RF clock with a 25% duty cycle ensures the orthogonal summation of Ipath and Qpath, which avoids nonlinear signal distortion. It was clarified that electric summing of I and Q digital unit array switches is the most appropriate I/Q orthogonal summation approach. Moreover, to address all four quadrants of the constellation diagram, the differential quadrature upconverting RF clocks must be utilized. In addition, it was explained that employing switches instead of utilizing current sources leads to superior noise performance of the all-digital I/Q transmitter. In Chapter 4, a novel 2×3-bit all-digital I/Q (Cartesian) RF transmit modulator is implemented which operates as an RF-DAC. The modulator performs based on the concept of orthogonal summing, which is introduced and elaborated in Chapter 3. It is based on a time-division duplexing (TDD) manner of an orthogonal I/Q addition. By employing this method, a very simple and compact design featuring high-output power, power-efficiency and low-EVM has been realized. The resolution of the experimental RF-DAC presented in this work is only 3-bit (including one sign bit), but it will be demonstrated in the following chapters that the resolution can be increased to 8–12 bits in an unequivocal manner for utilization in multi-standard wireless applications. In Chapter 5, the system design considerations of the proposed high-resolution, wideband all-digital I/Q RF-DAC are discussed. It is demonstrated that the upsampling clock frequency (fCKR), DRAC resolution (Nb), and memory length (lmem) are three important parameters that affect the dynamic performance of the proposed RF-DAC. Based on system level simulation results and the limitation in implementing the RF-DAC test-chip, they are designated as fCKR=300 MHz, Nb=12 bit, and lmem=8 k-word. The effect of these parameters on the in-band as well as out-of-band performance of RF-DAC are investigated. It is concluded that exploiting 13 bits of resolution for quadrature baseband signals is sufficient to meet the most stringent communication requirements. In Chapter 6, the theory and the design procedure of an innovative, differential, orthogonal power combining network, which is employed in the proposed all-digital modulator, is thoroughly explained. It is demonstrated that, in order to maintain an orthogonal operation between the in-phase and quadrature-phase paths, the effect of the power combiner on the in-phase and quadrature-phase paths must be considered, otherwise, the linear summation will not occur. As a result, the EVM and linearity performance will diminish. The power combiner consists of a transformer balun as well as its related programmable primary and secondary shunt capacitors. In order to achieve high efficiency at full power of operation, a class-E type matching network is adopted and subsequently modified in order to obtain a minimum modulation error. A switchable cascode structure is exploited to mitigate a reliability issue as well as to perform a mixer operation. Moreover, utilizing a switchable cascode structure also improves the isolation between quadrature paths. Furthermore, it is explained that the power combiner efficiency is primarily related to the transformer balun efficiency. A procedure is introduced in order to design an efficient, compact balun transformer. Also, it is explained that the RF-DAC operates as a class-B power amplifier at the power back-off levels. As a result, its performance in the power back-off region is lowered. In Chapter 7, the implemented wideband, 2×13-bit I/Q RF-DAC-based all-digital modulator realized in 65-nm CMOS is presented. Employing the orthogonal I/Q combining approach which is proposed in Chapter 3 guarantees the isolation between in-phase and quadrature-phase paths. The 4×f0 off-chip single-ended clock is converted to a differential version employing an on-chip transformer. The wide swing, low phase noise, high-speed dividers are incorporated to translate the 4×f0 differential clock to the fundamental frequency of f0. In the meantime, the complementary quadrature sign bit is used to address four quadrants of the related constellation diagram. The 25% differential quadrature clocks are generated using logic-AND operation between 2×f0 differential clock and f0 differential quadrature clocks. The 12-bit DRAC is implemented employing a segmentation approach, which consists of 256 MSB and 16 LSB thermometer unit cells. The layout arrangement of the DRAC unit cell proves to be very crucial. It was concluded that the vertical layout would be the most appropriate selection. The LO leakage and I/Q image rejection technique as well as two DPD memoryless techniques of AM-AM/AM-PM and constellation mapping are introduced, which will be extensively utilized in the measurement segment. In Chapter 8, the high-resolution wideband 2×13-bit all-digital I/Q transmitter, which was introduced in Chapter 7, is thoroughly measured. First, the chip is tested in continuouswave mode operation. It is demonstrated that, with a 1.3V supply and, of course, an on-chip power combiner, the RF-DAC chip generates more than 21dBm RF output power within a frequency range of 1.36–2.51 GHz. The peak RF output power, overall system, and drain energy efficiencies of the modulator are 22.8 dBm, 34%, and 42%, respectively. The measured static noise floor is below -160 dBc/Hz. The digital I/Q RF modulator demonstrates an IQ image rejection and LO leakage of -65 dBc and -68 dBc, respectively. The RF-DAC could be linearized employing either of the two digital predistortion (DPD) approaches: memoryless polynomial or a lookup table. Its linearity is examined utilizing 4/16/64/256/1024-QAM baseband signals while their related modulation bandwidth can be as high as 154 MHz. Using AM-AM/AM-PM DPD improves the linearity by more than 25 dB while the measured EVM is better than -28 dB. Moreover, the constellation-mapping DPD is applied to the RF-DAC which improves linearity by more than 19 dB. These numbers indicate that this innovative concept is a viable option for the next generations of multi band/multi-standard transmitters. The realized demonstrator can perform as an energy-efficient RF-DAC in a stand-alone digital transmitter directly (e.g., for WLAN) or as a pre-driver for high-power basestation PAs. Chapter 9 draws the conclusions of the this thesis work and provides recommendations for future research and directions in the field of all-digital RF transmitters for wireless communication applications.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Modification of Loop 1 Affects the Nucleotide Binding Properties of Myo1c, the Adaptation Motor in the Inner Ear
Get PDFMyo1c is one of eight members of the mammalian myosin I family of actin-associated molecular motors. In stereocilia of the hair cells in the inner ear, Myo1c presumably serves as the adaptation motor, which regulates the opening and closing of transduction channels. Although there is conservation of sequence and structure among all myosins in the N-terminal motor domain, which contains the nucleotide- and actin-binding sites, some differences include the length and composition of surface loops, including loop 1, which lies near the nucleotide-binding domain. To investigate the role of loop 1, we expressed in insect cells mutants of a truncated form of Myo1c, Myo1c1IQ, as well as chimeras of Myo1c1IQ with the analogous loop from other myosins. We found that replacement of the charged residues in loop 1 with alanines or the whole loop with a series of alanines did not alter the ATPase activity, transient kinetics properties, or Ca2+ sensitivity of Myo1c1IQ. Substitution of loop 1 with that of the corresponding region from tonic smooth muscle myosin II (Myo1c1IQ-tonic) or replacement with a single glycine (Myo1c1IQ-G) accelerated the release of ADP from A.M 2?3-fold in Ca2+, whereas substitution with loop 1 from phasic muscle myosin II (Myo1c1IQ-phasic) accelerated the release of ADP 35-fold. Motility assays with chimeras containing a single ?-helix, or SAH, domain showed that Myo1cSAH-tonic translocated actin in vitro twice as fast as Myo1cSAH-WT and 3-fold faster than Myo1cSAH-G. The studies show that changes induced in Myo1c via modification of loop 1 showed no resemblance to the behavior of the loop donor myosins or to the changes previously observed with similar Myo1b chimeras
Model predictive ship collision avoidance based on Q-learning beetle swarm antenna search and neural networks
No full textReal-time collision avoidance with full consideration of ship maneuverability, collision risks and International Regulations for Preventing Collisions at Sea (COLREGs) is difficult in multi-ship encounters. To deal with this problem, a novel method is proposed based on model predictive control (MPC), an improved Q-learning beetle swarm antenna search (I-Q-BSAS) algorithm and neural networks. The main idea of this method is to use a neural network to approximate an inverse model based on decisions made with MPC for collision avoidance. Firstly, the predictive collision avoidance strategy is established following the MPC concept incorporating an I-Q-BSAS algorithm to solve the optimization problem. Meanwhile, the relative collision motion states in typical encounters are collected for training an inverse neural network model, which is used as an approximated optimal policy of MPC. Moreover, to deal with uncertain dynamics, the obtained policy is reinforced by long-term retraining based on an aggregation of on-policy and off-policy data. Ship collision avoidance in multi-ship encounters can be achieved by weighting the outputs of the neural network model with respect to different target ships. Simulation experiments under several typical and multi-ship encounters are carried out using the KVLCC2 ship model to verify the effectiveness of the proposed method.Accepted Author ManuscriptTransport Engineering and Logistic
Electromagnetic form factors of nucleons in a light-cone diquark model
No full textWe investigate the electromagnetic form factors of nucleons within a simple relativistic quark spectator-diquark model using the light-cone formalism. Melosh rotations are applied to both quark and vector diquark. It is shown that the difference between vector and scalar spectator diquarks reproduces the right electric form factor of neutrons, and both the form factors G(E)(Q(2)) and G(M)(Q(2)) of the proton and neutron agree with experimental data well up to Q(2) = 2 GeV2 in this simple model.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000174548200084&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, NuclearSCI(E)0ARTICLE3null6
The Convergence of <i>q</I>-bernstein Polynomials (0 < <i>q</I> < 1) and Limit <i>q</I>-bernstein Operators in Complex Domains
No full textDue to the fact that the convergence properties of q-Bernstein polynomials are not similar to those in the classical case q = 1, their study has become an area of intensive research with a wide scope of open problems and unexpected results. The present paper is focused on the convergence of q-Bernstein polynomials, 0 < q < 1, and related linear operators in complex domains. An analogue of the classical result on the simultaneous approximation is presented. The approximation of analytic functions With the help of the limit q-Bernstein operator is studied.National Natural Science Foundation of China [10871132]; Beijing Natural Science Foundation [1062004]; Key Programs of Beijing Municipal Education Commission [KZ200810028013]The second author was partially supported by National Natural Science Foundation of China (Project no. 10871132), Beijing Natural Science Foundation (1062004) and by a grant from the Key Programs of Beijing Municipal Education Commission (KZ200810028013)
Alternative Exon 9-Encoded Relay Domains Affect More than One Communication Pathway in the Drosophila Myosin Head
Get PDFWe investigated the biochemical and biophysical properties of one of the four alternative regions within the Drosophila myosin catalytic domain: the relay domain encoded by exon 9. This domain of the myosin head transmits conformational changes in the nucleotide-binding pocket to the converter domain, which is crucial to coupling catalytic activity with mechanical movement of the lever arm. To study the function of this region, we used chimeric myosins (IFI-9b and EMB-9a), which were generated by exchange of the exon 9-encoded domains between the native embryonic body wall (EMB) and indirect flight muscle isoforms (IFI). Kinetic measurements show that exchange of the exon 9-encoded region alters the kinetic properties of the myosin S1 head. This is reflected in reduced values for ATP-induced actomyosin dissociation rate constant (K(1)k(+2)) and ADP affinity (K(AD)), measured for the chimeric constructs IFI-9b and EMB-9a, compared to wild-type IFI and EMB values. Homology models indicate that, in addition to affecting the communication pathway between the nucleotide-binding pocket and the converter domain, exchange of the relay domains between IFI and EMB affects the communication pathway between the nucleotide-binding pocket and the actin-binding site in the lower 50-kDa domain (loop 2). These results suggest an important role of the relay domain in the regulation of actomyosin cross-bridge kinetics
The Norm Estimates for The <i>q</I>-bernstein Operator in The Case <i>q</I> > 1
No full textThe q-Bernstein basis with 0 1, the behavior of the q-Bernstein basic polynomials on [0, 1] combines the fast increase in magnitude with sign oscillations. This seriously complicates the study of q-Bernstein polynomials in the case of q > 1. The aim of this paper is to present norm estimates in C[0, 1] for the q-Bernstein basic polynomials and the q-Bernstein operator B-n,B-q in the case q > 1. While for 0 1, the norm parallel to B-n,B-q parallel to increases rather rapidly as n -> infinity. We prove here that parallel to B-n,B-q parallel to similar to C(q)q(n(n-1)/2)/n, n -> infinity with C-q = 2 (q(-2); q(-2))(infinity)/e. Such a fast growth of norms provides an explanation for the unpredictable behavior of q-Bernstein polynomials (q > 1) with respect to convergence.National Natural Science Foundation of China [10871132]; Beijing Natural Science Foundation [1062004]; Beijing Municipal Education Commission [KZ200810028013]The first author was supported by National Natural Science Foundation of China (Project no. 10871132), Beijing Natural Science Foundation (1062004), and by a grant from the Key Programs of Beijing Municipal Education Commission (KZ200810028013)
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