Modal Power Research Articles

Data Structures and their Planar Graph Layouts

In a stack layout, also known as book embedding, the vertices of a graph are placed on a line and an edge is a data item that is pushed on the stack at the left vertex and removed at the right vertex. The LIFO principle of the stack is represented by a rainbow of nesting edges. We introduce linear cylindric drawings for the representation of the working principles of fundamental data structures including stack, queue, double-stack and deque. The resulting graphs are called stack (queue, double-stack, deque) graphs. We characterize the feasibility of a sequence of insertions and removals by planarity and use the graph classes to compare the relative power of these data structures. In particular, we show that the deque graphs are the linear cylindric planar graphs and are the subgraphs of the planar graphs with a Hamiltonian path. In comparison, the double-stack graphs are the graphs with a linear layout in the plane and are known as the subgraphs of the planar graphs with a Hamiltonian cycle. Hence, the power of the queue mode of a deque is expressed both by the differences between Hamiltonian path and Hamiltonian cycle and by linear layouts on the cylinder and in the plane. It is also reflected in the dual graph. Linear cylindric drawings provide an intuitive planar representation of the FIFO principle of a queue. We show that a queue graph augmented by a Hamiltonian path has a dual of the same type and that the dual has an Eulerian path. Finally, we study recognition problems.

Optical frequency comb active filtering and amplification for second cooling laser of strontium optical clock

In this paper, we propose an optical frequency comb active filtering and amplification method combined with injection-locking technique to select and amplify a single mode from a femtosecond mode-locked laser. The key concept is to optically inject an optical frequency comb into a single mode grating external cavity semiconductor laser. The optical frequency comb based on a femtosecond mode-locked laser with a narrow mode spacing of 250 MHz is used as a master laser. The center wavelength of the optical frequency comb is 689 nm with a 10 nm spectral width. A single mode grating external cavity semiconductor laser with a grating of 1800 lines/mm is used as a slave laser, and the external-cavity length from the diode surface to the grating is approximately 50 mm. The master laser is injected into the slave laser, and in order to select a single comb mode, we adjust the power of the master laser to control the locking range of the slave laser whose linewidth is smaller than the optical frequency comb repetition rate (250 MHz). While the operating current of the slave laser is set to be 55 mA and a seeding power is adopted to be 240 W, a single longitudinal mode is selected and amplified from 2.5104 longitudinal modes of the femtosecond optical comb despite the low power of the single mode. By tuning the optical frequency comb repetition frequency, the single longitudinal mode follows the teeth of the femtosecond optical comb, indicating the success in the optical frequency comb active filtering and amplification. The locking range is measured to be about 20 MHz. Meanwhile, the repetition frequency of the optical frequency comb is locked to a narrow linewidth 698 nm laser system (Hz level), thus the slave laser inherits the spectral characteristics of the 698 nm laser system. The linewidth is measured to be 280 Hz which is limited by the test beating laser. Then a continuous-wave narrow linewidth 689 nm laser source with a power of 12 mW and a side-mode suppression ratio of 100 is achieved. This narrow linewidth laser is used as a second-stage cooling laser source in the 88Sr optical clock, the cold atoms with a temperature of 3 K and a number of 5106 are obtained. This method can also be used to obtain other laser sources for atomic optical clock, and thus enabling the integrating and miniaturizing of a clock system.

Ultra-compact silicon nitride grating coupler for microscopy systems

Grating couplers have been widely used for coupling light between photonic chips and optical fibers. For various quantum-optics and bio-optics experiments, on the other hand, there is a need to achieve good light coupling between photonic chips and microscopy systems. Here, we propose an ultra-compact silicon nitride (SiN) grating coupler optimized for coupling light from a waveguide to a microscopy system. The grating coupler is about 4 by 2 μm2 in size and a 116 nm 1 dB bandwidth can be achieved theoretically. An optimized fabrication process was developed to realize suspended SiN waveguides integrated with these couplers on top of a highly reflective bottom mirror. Experimental results show that up to 53% (2.76 dB loss) of the power of the TE mode can be coupled from a suspended SiN waveguide to a microscopy system with a numerical aperture (NA) = 0.65. Simulations show this efficiency can increase up to 75% (1.25 dB loss) for NA = 0.95.

Enhanced spin wave propagation in magnonic rings by bias field modulation

We simulate the spin wave (SW) dynamics in ring structures and obtain the ω − k dispersion relations corresponding to the output waveguide. Different bias field configurations affect the transfer of SW power from one arm of the structure to the other arm. To this end, we show that circular or radial bias fields are more suitable for energy transfer across the ring than the conventional horizontal bias field Hx. The SW dispersion shows that modes excited, when the bias field is along the ring radius, are almost 10 dB higher in power when compared to the modal power in the case of Hx. This is also corroborated by the SW energy density in the receiving stub.

A ps level actively mode-locked Ho:Sc2SiO5 laser at 2112.1 nm resonantly-pumped by Tm fiber laser

An actively mode-locked Ho:SSO laser was reported for the first time, which was resonantly-pumped by a Tm-doped fiber laser. Both performance of continuous wave (CW) mode and continuous wave mode-locked (CWML) were researched in this paper. For the CW mode, the maximum output power of the 2.88 W with the central wavelength of 2112.1 nm was achieved, when the absorbed pump power was 16.2 W. The optical-optical conversion efficiency was 17.8%. Compared with the CW mode, the maximum laser output power of CWML mode was a little lower, which was 2.72 W corresponding to an optical-optical conversion efficiency of 16.8%. However, the laser output wavelength of the CWML mode was the same as the CW mode focus on 2112.1 nm. The repetition rate of CWML pulse was measured to be 81.88 MHz with the single pulse energy of 33.2 nJ and pulse duration of 282.4 ps. The peak-power was 117.6 W.

The Value of Full-Duplex for Cellular Networks: A Hybrid Duplex-Based Study

Recent work has demonstrated the gain of full-duplex (FD) network over half-duplex (HD) network in bidirectional sum throughput under the assumption of symmetric uplink-downlink traffic demands and perfect self-interference suppression (SIS). In this paper, we study the performance gain of FD network over HD network under asymmetric bidirectional traffic demands and non-ideal SIS. To this end, we investigate the traditional static time division duplex (TDD) transmission mode and the advanced dynamic TDD transmission mode to obtain the performance of HD network, and investigate the pure FD transmission mode and a flexible HD-FD hybrid transmission mode, namely, XD mode, to obtain the performance of FD network. We use the number of users supported by a network as performance metric, which is defined as the minimum of the weighted numbers of users supported in uplink and downlink given random traffic demands of users. To maximize the number of users, we optimize the bidirectional transmit power for pure FD mode, bidirectional time slot configuration for dynamic TDD mode, and both for XD mode. Numerical results show an evident gain of pure FD mode and XD mode over static TDD mode for different levels of traffic asymmetry, but the gain over dynamic TDD mode is marginal, which cannot justify the application of FD technology in cellular systems without advanced interference control mechanisms.

The Post-Truth About Philosophy and Rhetoric

ABSTRACT This fiftieth anniversary reflection begins by recalling a debate on its pages about the origins of rhetoric, which queried the relationship between Plato and the Sophists. I argue that contrary to the shared assumption of the scholars in this debate, Plato and the Sophists differed less over what counts as good philosophical/rhetorical practice than over whether its access should be free or restricted. An implication of this proposed shift in interpretation is that Plato and the Sophists are both reasonably seen as “post-truth” thinkers, concerned more with the mix of chance and skill in the construction of truth than with the truth as such. Focusing on Plato's hostility to playwrights, I argue that at stake is control over “modal power,” which is ultimately about defining the sphere of what is possible in society. I end with a brief discussion of the problematic of public relations as an ongoing contemporary version of much the same story.

Adaptive RF Front-Ends Using Electrical-Balance Duplexers and Tuned SAW Resonators

This paper proposes an adaptive RF front-end (RFFE) architecture that uses an electrical-balance duplexer (EBD) and tuned surface acoustic wave (SAW) resonators to enable adaptive dual-frequency isolation suited for LTE’s frequency-division duplex (FDD) mode of operation. Alternatively, in the in-band full-duplex (IBFD) mode, the EBD cancels the in-band TX self-interference directly at RF for increased channel capacity. Furthermore, the EBD’s balance network is optimized to reduce the TX insertion loss (IL) below the nominal 3-dB limit in the FDD mode. A 0.18- $\mu \text{m}$ SOI CMOS prototype implements the EBD, low-noise amplifier, and SAW-tuning capacitor banks. The chip is mounted to a module substrate together with the SAWs and matching components. The RFFE achieves >50-dB dual-frequency isolation and 2.6–3.4-dB TX IL in FDD mode, has +58/+42-dBm TX/RX-path IIP3 for an increased IBFD-link budget and handles up to +27.5-dBm TX power in both modes.

Determination of temperature and residual laser energy on film fiber-optic thermal converter for diode laser surgery

Background: The diode laser was utilized in soft tissue incision of oral surgery based on the photothermic effect. The contradiction between the ablation efficiency and the thermal damage has always been in diode laser surgery, due to low absorption of its radiation in the near infrared region by biological tissues. Fiber-optic thermal converters (FOTCs) were used to improve efficiency for diode laser surgery. The purpose of this study was to determine the photothermic effect by the temperature and residual laser energy on film FOTCs.Methods: The film FOTC was made by a distal end of optical fiber impacting on paper. The external surface of the converter is covered by a film contained amorphous carbon. The diode laser with 810 nm worked at the different rated power of 1.0 W, 1.5 W, 2.0 W, 3.0 W, 4.0 W, 5.0 W, 6.0 W, 7.0 W, 8.0 W in continuous wave (CW)and pulse mode. The temperature of the distal end of optical fiber was recorded and the power of the residual laser energy from the film FOTC was measured synchronously. The temperature, residual power and the output power were analyzed by linear or exponential regression model and Pearson correlations analysis.Results: The residual power has good linearity versus output power in CW and pulse modes (R2 = 0.963, P < 0.01 for both). The temperature on film FOTCs increases exponentially with adjusted R2 = 0.959 in continuous wave mode, while in pulsed mode with adjusted R2 = 0.934. The temperature was elevated up to about 210 °C and eventually to be a stable state. Film FOTCs centralized approximately 50% of laser energy on the fiber tip both in CW and pulsed mode while limiting the ability of the laser light to interact directly with target tissue.Conclusions: Film FOTCs can concentrate part of laser energy transferred to heat on distal end of optical fiber, which have the feasibility of improving efficiency and reducing thermal damage of deep tissue.

Science Teacher Educators’ Engagement with Pedagogical Content Knowledge and Scientific Inquiry in Predominantly Paper-Based Distance Learning Programs

This article focuses on the dilemmas science educators face when having to introduce Pedagogical Content Knowledge (PCK) to science student teachers in a predominantly paper-based distance learning environment. It draws on the premise that science education is bound by the Nature of Science (NOS), and by the Nature of Scientific Inquiry (NOSI). Furthermore, science educators’ own PCK, and the limitations of a predominantly paper-based distance education (DE) model of delivery are challenges that they have to face when introducing PCK and authentic inquiry-based learning experiences. It deprives them and their students from optimal engagement in a science-oriented community of practice, and leaves little opportunity to establish flourishing communities of inquiry. This study carried out a contextual analysis of the tutorial material to assess the PCK that the student teachers had been exposed to. This comprised the ideas of a community of inquiry, a community of science, the conceptualization of PCK, scientific inquiry, and the 5E Instructional Model of the Biological Sciences Curriculum Study. The analysis confirmed that the lecturers had a good understanding of NOS, NOSI and science process skills, but found it difficult to design interventions to optimize the PCK development of students through communities of inquiry. Paper-based tutorials are ideal to share theory, policies and practices, but fail to monitor the engagement of learners in communities of inquiry. The article concludes with a number of suggestions to address the apparent lack of impact power of the paper-based mode of delivery, specifically in relation to inquiry-based teaching and learning (IBTL).

Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile

Broadband precision spectroscopy is indispensable for providing high fidelity molecular parameters for spectroscopic databases. We have recently shown that mechanical Fourier transform spectrometers based on optical frequency combs can measure broadband high-resolution molecular spectra undistorted by the instrumental line shape (ILS) and with a highly precise frequency scale provided by the comb. The accurate measurement of the power of the comb modes interacting with the molecular sample was achieved by acquiring single-burst interferograms with nominal resolution matched to the comb mode spacing. Here we describe in detail the experimental and numerical steps needed to achieve sub-nominal resolution and retrieve ILS-free molecular spectra, i.e. with ILS-induced distortion below the noise level. We investigate the accuracy of the transition line centers retrieved by fitting to the absorption lines measured using this method. We verify the performance by measuring an ILS-free cavity-enhanced low-pressure spectrum of the 3ν1 + ν3 band of CO2 around 1575 nm with line widths narrower than the nominal resolution. We observe and quantify collisional narrowing of absorption line shape, for the first time with a comb-based spectroscopic technique. Thus retrieval of line shape parameters with accuracy not limited by the Voigt profile is now possible for entire absorption bands acquired simultaneously.

Hardness variation of welded boron steel using continuous wave (CW) and pulse wave (PW) mode of fiber laser

Recent car manufacturer requirement in lightweight and optimum safety lead to utilization of boron steel with tailor welded blank approach. Laser welding process in tailor welded blank (TWB) production can be applied in continuous wave (CW) of pulse wave (PW) which produce different thermal experience in welded area. Instead of microstructure identification, hardness properties also can determine the behavior of weld area. In this paper, hardness variation of welded boron steel using PW and CW mode is investigated. Welding process is conducted using similar average power for both welding mode. Hardness variation across weld area is observed. The result shows similar hardness pattern across weld area for both welding mode. Hardness degradation at fusion zone (FZ) is due to ferrite formation existence from high heat input applied. With additional slower cooling rate for CW mode, the hardness degradation is become obvious. The normal variation of hardness behavior with PW mode might lead to good strength.

Electro-plasmonic Modal Power Shifting in Metal/Insulator/Semiconductor Structure Tailored as a CMOS-compatible Plasmonic Waveguide

In this paper, we have proposed a new npn-type design of a CMOS-compatible metal/semiconductor/insulator/metal (MSIM) plasmonic structure, to be used as a different geometry to manipulate, guide, and route surface plasmon polaritons (SPPs). Relying on the sub-wavelength diffraction-free plasmonic technology, the proposed ultra-compact structure has only a 20-nm-thick dynamic region accompanied by 1 to 2-nm thin-film HfO2 gate insulator as a distinct carrier barrier to serve both electronic and optic characteristics. The device is tailored as a mixture of MOSFET and BJT transistors in which to attain electro-plasmonic tuning goals; the npn-type structure uses rather large electron concentration densities accumulated near the oxide/semiconductor interface under 7.6-v switching voltage. This fact leads to adequate modal index variation of a doped Si, dynamic region by which routing of plasmonic traveling waves at a fiber communications wavelength of λ = 1550 nm will be possible. To investigate the optical and electronic behaviors of design, we have launched electromagnetic simulations solved on the rigorous finite element method (FEM) and also quantum mechanical (QM) included carrier transport simulations, respectively. To be reported, the estimated plasmonic modal power movement from the left-side-half-Si-core to the right-side-half-Si-core can reach to percentages of even 23.7%. This MSIM electro-plasmonic-addressed structure can be dramatically used to design specific-application routing/switching devices.

On the signatures of flare-induced global waves in the Sun: GOLF and VIRGO observations

Recently, several efforts have been made to identify the seismic signatures of flares and magnetic activity in the Sun and Sun-like stars. In this work, we have analyzed the disk-integrated velocity and intensity observations of the Sun obtained from the GOLF and VIRGO/SPM instruments, respectively, on board the SOHO space mission covering several successive flare events, for the period from 11 February 2011 to 17 February 2011, of which 11 February 2011 remained a relatively quiet day and served as a "null test" for the investigation. Application of the spectral analysis to these disk-integrated Sun-as-a-star velocity and intensity signals indicates that there is enhanced power of the global modes of oscillations in the Sun during the flares, as compared to the quiet day. The GOLF instrument obtains velocity observations using the Na I D lines which are formed in the upper solar photosphere, while the intensity data used in our analysis are obtained by VIRGO/SPM instrument at 862~nm, which is formed within the solar photosphere. Despite the fact that the two instruments sample different layers of the solar atmosphere using two different parameters (velocity v/s intensity), we have found that both these observations show the signatures of flare-induced global waves in the Sun. These results could suffice in identifying the asteroseismic signatures of stellar flares and magnetic activity in the Sun-like stars.

Transients of Modal-Power Distribution in Multimode Solid-Core W-Type Photonic Crystal Fibers

Spatial transients of the modal power distribution are reported for a varied configuration of air holes in the inner cladding of multimode solid-core photonic crystal fibers. Such inner cladding forms an intermediate fiber layer seen in W-type fibers with the layer's own effective refractive index due to the distinct size and/or spacing of air holes in it. We show how the modal distribution transients along the fiber depend on the number of rings in the inner cladding containing the distinct arrangement of air holes, and on the size and spacing of such holes in addition to the type of launch condition (excitation).

Theoretical study of laser-mode competition in quantum-dot semiconductor lasers using a self-consistent electro-opto-thermal model

We present a new model for quantum-dot (QD) semiconductor lasers which includes the self-consistent treatment of electrical, optical, and thermal interactions. The approach is developed from the energy balance equation to incorporate the carrier temperature and a three-level rate equation to describe the carrier and photon dynamics within the QD active region operating simultaneously on two longitudinal modes: via ground-state (GS) and first-excited-state (ES) transitions. Using the presented model, the steady-state, small-signal modulation response and transient device characteristics are calculated and analyzed. Similar to the situation of mode competition of laser modes, it is found that the light output power of the GS mode enters the roll-off regime, while the power of the ES mode increases. The model also predicts the negative temperature dependency of the power threshold for the ES mode, which can be understood from the negative temperature-dependent behavior of incomplete clamping of the ES population above the GS threshold. The simulated results are in good agreement with experimental data from the devices reported earlier.

Mode decomposition of structures with closely distributed modes and nonclassical damping

It is difficult to apply traditional modal analysis methods to structures with nonclassical damping or closely distributed modes, because the damping matrix is not diagonalized by the modal matrix obtained from the mass and stiffness matrices. In this paper, a new mode decomposition method for structures with nonclassical damping and very closely distributed modes is proposed. This method defines the generalized modes in state space and uses differential state variables constructed from measured acceleration responses to decompose modal responses. A Kalman filtering approach is utilized to calculate the linear transformation matrix of governing modes, and the linear transformation matrix is updated in the optimization process of the objective functions integrated with the power spectral density of a target mode. The two performance functions are proposed to maximize the energy at a certain mode and to minimize the differences between the decomposed modal power spectrum and averaged power spectrum, assuming that each mode has a monochromatic signature with one natural frequency and one damping ratio. To verify the proposed method, a numerical simulation is performed using a single degree of freedom system coupled with a tuned mass damper that represents a nonclassically damped system with closely distributed modes. The results from the simulations show that the proposed method estimates the modal responses more precisely than conventional mode decomposition methods such as the independent component analysis method.

Intrinsic Mode Function Based Noise Power Estimation With Applications to Semiblind Spectrum Sensing Methods

In this letter, an algorithm is proposed to blindly estimate the noise power embedded in a received signal and use the knowledge of the noise power to upgrade semiblind spectrum sensors to blind sensors. The proposed noise estimator is based on a relationship between the noise power of a received signal and the power of the first mode of the empirical mode decomposition algorithm. Simulations and results demonstrate an enhancement of the detectors performance in contrast with their conventional semiblind versions.

SELECTION OF RATIONAL PARAMETERS OF THE NOMINAL MODE ELECTRIC TRAINS WITH ASYNCHRONOUS TRACTION DRIVE

Purpose. Parameters of the nominal mode are related to the most important performance indicators of traction means, therefore, the problems of choosing their optimal values always inevitably arise when forming technical requirements for a new rolling stock. The paper describes the features of solving the above-mentioned problems for electric trains with an asynchronous traction drive in the case of two-zone and three-zone frequency control of power. Methodology. Power of nominal mode of the rolling stock should be chosen in such a way that it would be possible to realize a predetermined travel time along in the section or the movement speed. On that basis, and also taking into account the fact that the important operational characteristics of electric trains include the acceleration value during the start-up and acceleration at the design speed, we will formulate the problem of determining the nominal power. In the task for a given range of traction, it is necessary to find such a value of the nominal mode power and the corresponding force value to ensure the ability to carry out transportations with the given level of average speed with minimal energy consumption for traction. At the same time, it is necessary to fulfill the following conditions: a) the speed of the electric train on the section does not exceed the established limits; b) it is possible to realize the given values of accelerations. A more detailed consideration of the problem shows that in real conditions, when the starting acceleration and the mass of the train are given, the problem of determining electric train power is practically reduced to determining the optimal value of the nominal mode speed. Findings. The task of choosing the optimal values of the nominal mode speed is solved by determining the electric power consumption with the variation of the possible values of starting speed. Therefore, only those values that ensure the implementation of the given starting and residual accelerations should be taken into account. The work shows that the traction force value increases with the design speed increase and other equal conditions, if the starting speed is increased. Originality. Authors developed the methodology for determining the optimal values of the nominal mode parameters of electric trains with an asynchronous traction drive, with two-zone and three-zone frequency power regulation. Practical value. The above mentioned methodology can be the basis when forming technical requirements for new rolling stock for Ukraine’s railways.

Evaluation of Modal Power Distribution of Automotive Optical Gigabit Ethernet Connections

Automotive optical gigabit Ethernet is a technology that is expected to realize autonomous driving cars with notable benefits: electromagnetic interference free, lighter weight, and higher data communication. Plastic optical fibers have been used in automotive optical networks since 1998. To secure a higher data rate, two issues must be considered: the need for modal power distribution (MPD) control and the lack of link margin. Here, we performed a combined study of MPD and the frequency characteristics of a 15-m optical fiber cable with multiple connections. The results reveal that the links have transmission directivity and the number of connections influences the bandwidth with different MPDs, as shown in encircled angular flux (EAF) profiles. We also show that automotive optical connections typically contain an air gap that generates higher mode radiation. To minimize this radiation, we filled the gap with a cured gel. We found that the EAF profile shifts from 13.8° to 15.4° at 50% EAF with a 1.75-dB insertion loss improvement based on the shift at z/a = 3.1 (where z indicates the axial misalignment at the connection, and a is the core radius). The approach presented here is an effective solution for facilitating the rapid realization of automotive optical gigabit communication.