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Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in power splitters remains a significant challenge. In this paper, we designed a power splitter based on a subwavelength grating (SWG) structure with tilted placement on a silicon-on-insulator (SOI) substrate. We achieve arbitrary TE0–TE9 mode-insensitive power distribution by altering the filling coefficient of the SWG. Thanks to our specific selection of cladding materials and compensatory design for the optical wave transmission and reflection shifts induced by SWG, our device demonstrates low additional loss (EL < 1.1 dB) and inter-mode crosstalk (−18.8 < CT < −60 dB) for optical modes ranging from TE0 to TE9, covering a wavelength range from 1200 nm to 1700 nm. Furthermore, our proposed device can be easily extended to higher-order modes with little loss of device performance, offering significant potential in MDM platforms. [ABSTRACT FROM AUTHOR]

The paper deals with ring extensions R ⊆ S and their lattices [R, S] of subextensions and is mainly devoted to FCP extensions (extensions whose lattices are Artinian and Noetherian). The object of the paper is the introduction and the study of elements of the lattices that split in some sense ring extensions. The reason why is that this splitting was used in earlier paper without their common nature being recognized. There are some favorable cases allowing to build splitters, mainly when we are dealing with B -extensions, for example integral extensions. Integral closures and Prüfer hulls of extensions play a dual role. The paper gives many combinatorics results with the explicit computation of the Prüfer hull of an FCP extension. We show that a split extension cannot be pinched, except trivially. [ABSTRACT FROM AUTHOR]

Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in power splitters remains a significant challenge. In this paper, we designed a power splitter based on a subwavelength grating (SWG) structure with tilted placement on a silicon-on-insulator (SOI) substrate. We achieve arbitrary TE0–TE9 mode-insensitive power distribution by altering the filling coefficient of the SWG. Thanks to our specific selection of cladding materials and compensatory design for the optical wave transmission and reflection shifts induced by SWG, our device demonstrates low additional loss (EL < 1.1 dB) and inter-mode crosstalk (−18.8 < CT < −60 dB) for optical modes ranging from TE0 to TE9, covering a wavelength range from 1200 nm to 1700 nm. Furthermore, our proposed device can be easily extended to higher-order modes with little loss of device performance, offering significant potential in MDM platforms.

One of the most effective ways to reduce the water jet erosion power during dam overflow is to use splitters on the lower side of the spillway. The dimensions of scouring holes and their location in the dam basin should be accurately determined. Experimental models and data-driven techniques can be effectively used for estimating the dimensions of scouring holes. The focus of this paper is evaluating the effects of splitters on the downstream scour hole of overflow spillways and providing an optimized splitter configuration. The Support Vector Regression (SVR) method performance in predicting the scour hole dimensions and its location downstream of the dam has been examined using 116 experimental data. In order to evaluate the efficiency of the proposed model, we used different statistical measures. The results show that the presence of splitters decreases the slope of downstream scouring in all situations. It is also shown that the SVR method can accurately estimate the dimensions of the scour hole and its location. HIGHLIGHTS Designing, constructing and equipping large-scale hydraulic models.; Development of a simulation model to predict the dimensions of the scour hole in the presence and absence of splitters.; Using the SVR method.; Presenting a new approach for designing and studying the splitters as well as the scouring phenomenon.; Finding the relationship between the scouring phenomenon and its governing parameters.;

Given an n-vertex digraph D and a non-negative integer k, the Minimum Directed Bisection problem asks if the vertices of D can be partitioned into two parts, say L and R, such that | L | and | R | differ by at most 1 and the number of arcs from R to L is at most k. This problem is known to be NP-hard even when k = 0 . We investigate the parameterized complexity of this problem on semicomplete digraphs. We show that Minimum Directed Bisection admits a sub-exponential time fixed-parameter tractable algorithm on semicomplete digraphs. We also show that Minimum Directed Bisection admits a polynomial kernel on semicomplete digraphs. To design the kernel, we use (n , k , k 2) -splitters, which, to the best of our knowledge, have never been used before in the design of kernels. We also prove that Minimum Directed Bisection is NP-hard on semicomplete digraphs, but polynomial time solvable on tournaments. [ABSTRACT FROM AUTHOR]

In turbmachinery, splitters are used to control secondary flow and to improve the aerodynamic performance of outlet guide vane (OGV) of axial fan. However, there is few information in the open literature focusing on the effect of the splitter geometry on the secondary flow control. In this work, the numerical investigations were performed for NACA 65-010 profile with different splitters. The spacing ratio of the main blade was 1, the spacing between the splitters and the main blade was 30mm. Three different splitters were compared to investigate the effect of the splitter geometry on secondary flow control. The flow structures near the end-wall, the streamlines on the suction surface of blade and the distribution of the flow losses on the trailing edge of blade was shown and discussed. The results showed the splitters can control the secondary flow and reduce the area of the high flow losses at the junction of end-wall and blade. However, the flow separation of the splitters also causes flow losses in the wake behind the splitters. Therefore, only the specific configuration of splitters can reduce the flow losses of the blade. [ABSTRACT FROM AUTHOR]

Power splitters are considered essential components in optical interconnects. In this research work, two different designs of 1×2 3-dB small-footprint high-performance plasmonic power splitters with less than 1% loss in each branch are proposed and numerically investigated using the finite-difference-time-domain method. Based on the simulation results, we show that unequal splitting ratio can be achieved by breaking the symmetry of the two plasmonic branches either by changing the width or the position of one of the splitter branches with respect to the other one. Moreover, the proposed splitters' designs have the advantage of improving the alignment tolerance of the two plasmonic branches with respect to the centre of the dielectric waveguide in addition to broadening the spectrum response of the splitter. Our proposed technique can be extended to 1×N power splitters in addition to being employed in various high density photonic integration and nano-plasmonic circuits such as directional couplers and Mach–Zehnder interferometers. [ABSTRACT FROM AUTHOR]

Turbochargers used in gasoline engines have their compressor outlet directly coupled to the engine inlet via the throttle valve. On sudden closing of the throttle, the compressor outlet is blocked, and the compressed air has no path to exit resulting in a compressor surge. Compressor recirculation valves are used to connect the outlet of the compressor to the inlet to recirculate excess air and thus reduce the compressor surge. Under normal operating conditions, when the valve is closed, the channel connecting the compressor inlet and the valve causes an inlet disturbance resulting in the reduction of compressor efficiency. Hence a steady state CFD analysis of a gasoline engine turbocharger compressor modelled with a recirculation channel at the inlet was conducted. The channel connecting the compressor inlet and the recirculation valve was observed to cause inlet aerodynamic disturbance resulting in a drop in compressor efficiency by 1%. To overcome this problem, splitters were used in recirculation channels and 80% recovery of loss was observed with the use of splitters. [ABSTRACT FROM AUTHOR]

Recent studies of passive and active flow control devices for suppressing vortex-induced vibration (VIV) of circular cylinders are reviewed extensively. The passive control devices include splitter plates, control rods, helical strakes, porous layers and rough surfaces, and the active flow control devices include jet flow, rotating cylinder, and rotating control rods. A splitter plate with a certain length can suppress VIV but very long splitter can cause galloping. One or two control rods located downstream the flow separation points can suppress VIV. VIV suppression using three to eight control rods were also studied and increasing rod number can improve suppression effectiveness. Porous layers with sufficient porosity and thickness can achieve nearly full VIV suppression and generally have better suppression effect than rough surfaces. Helical strakes can suppress VIV well when its pitch ratio is greater than 10 and height is greater than 0.2 times cylinder diameter. If sufficient external energy is used, jet control and rotating control rods can achieve nearly full VIV suppression. Rotating control rods in one direction can suppress VIV but, in another direction, can enhance VIV. Some important conclusions are highlighted in section 4 of this paper. • Passive and active control devices for vortex induced vibration are reviewed comprehensively. • Five types of passive control devices are reviewed and the effectiveness of them are discussed. • Three types of active control devices are reviewed. • The pros and cons of these devices are discussed. [ABSTRACT FROM AUTHOR]

Macro-bending effect unto polymer optical fiber (POF) based splitters study is done to analyse the performance and characterizations using several bending radii of geometrical blocks that hold a customized prepared polymer fiber splitter. A pair of etched fibers with similar core diameters are attached to the ellipse-shaped blocks built using matching refractive index material where the blocks were built with various bending radii. The tapered fibers were lapped closely with some forces exerted upon them in order to stimulate the splitting of modes between the two fibers. This study is done by experimental set-up where each of the splitter ports is connected with optical power meter to measure the power output while pressure is exerted. Characterization is executed in order to investigate and analyse which bending radius gives the most optimize splitting ratio with considerable low loss for the particular splitter prepared. As for normal force of 0.3 lbF, the optimum splitting ratio with low loss is specified having bending radius, Rc, of 13 mm whilst for external force of 3.0 lbF, bending radius is found to be 19 mm. Small bending radius stimulates the radiation of rays into the second fiber while larger Rc gives longer coupling length that optimize the splitting ratios. Efficiencies between simulated values and experimental values are also analysed.

The aim of the paper is a structural design of a cutting device with option of length adjustment of cutting material. The introductory part of the paper is devoted to an analysis of available devices standardly employed in the process of wooden substance cutting. The core of the paper contains structural design and calculation of the individual parts, disposition solution of the device and a complete visualisation in the 3D models[Krenicky 2010]. The final part of the paper points out a necessity of application of newly-designed devices intended for wooden substance cutting as such case offers an absolute waste less utilization of wooden substance. [ABSTRACT FROM AUTHOR]

In this article we study the new proof of very fundamental property of Nagel Point. [ABSTRACT FROM AUTHOR]

We present a comprehensive mathematical formalism, together with its numerical implementation, for optical time-domain reflectometry (OTDR) simulations with the ability to produce OTDR traces of passive optical point-to-multipoint networks (PONs). According to our knowledge, the proposed OTDR simulator is the first one with this feature, thus progressing beyond the existing state of the art of OTDR simulations. In our approach, the optical fiber network under test is treated as a linear time-invariant single-input/single-output system, which allows us to include the effects of the OTDR pulse shape. Furthermore, the limitations of current OTDR equipment such as (nonlinear) power saturation of the detector, limited dynamic range due to OTDR noise, and the finite bandwidth of the detector, are also incorporated into the simulation model. Our simulation results are experimentally verified with OTDR measurements, and we show an excellent agreement between the simulated traces and the measured traces. Especially, we demonstrate that the simulations properly handle PONs, that may contain a cascade of splitters, providing an important tool for telecom operators to investigate cost-effective centralized monitoring techniques in fiber-to-the-home networks. [ABSTRACT FROM PUBLISHER]

Questions In view of the predominance of clonality in aquatic plants and its likely role in plant fitness, we specifically asked whether or not clonality contributes to invasiveness of macrophytes. We also aimed to explore clonal trait diversity in alien aquatic plants and evaluate its implications in the context of species invasiveness. Location Two Ramsar sites: Hokersar Wetland and Lake Wular, Kashmir Himalaya, India. Methods Extensive field surveys were carried out in the two target Ramsar sites. The clonal growth form categorization was done using the CLO- PLA 3 (clonal plant) database of clonal growth in plants, and the relationship between clonality and invasiveness was examined. We used a stage-based hierarchical model to categorize the investigated species into different stages of invasion (Stages II, III, IVa, IVb, V) and examine proportion of clonality at various stages of invasion. Results A total of 62 wetland plant species were recorded, most of which (58) were alien invasives. We characterized the clonal growth organ ( CGO) spectra in the target plant species and categorized them into four space occupancy strategies (i.e. spreading, non-spreading, splitters and integrators). More than 90% of the studied plants were clonal with a tendency of increasing clonality in plants belonging to higher stages of invasion (Stage V). Conclusions The present study revealed a significant positive correlation between clonality and species invasiveness, thereby indicating the likely contribution of clonality to invasion success. Given the paucity of studies on the contribution of clonality in invasiveness of alien species, our results have significant implications for invasion management in wetland systems. [ABSTRACT FROM AUTHOR]

The aim of this paper is to investigate the relationship between the Abelian groups G with and those satisfying for various cardinals κ. In particular, we will give the structure of self-Ext-small groups. Our results answer several open problems, and give new proofs of known theorems concerning -splitters, tilting groups and finitely faithful S-groups. [ABSTRACT FROM AUTHOR]

Passive Optical Networks (PONs) are mostly used as modern high-speed access networks today. Typically, PONs are based mainly on tree or hybrid tree-star topologies in practice. However, these topologies are significantly vulnerable, especially in case of sophisticated attacks or global malfunctions of central optical line termination (OLT) units. Due to that, an innovative idea of forming PON with a simple ring topology by using standard passive splitters was proposed and is presented within this paper. Thanks to a ring topology, the secondary OLT unit can be placed in any potential location within the ring and this can significantly increase the vulnerability of the whole network. The article contains the description of this idea and also necessary simulations were performed. To verify these theoretical assumptions, experimental PON network with a ring topology was created and its characteristics were measured and compared with simulations and models. Moreover, the functionality of the protection mechanism was confirmed as well as the functionality of the entire ring PON network. [ABSTRACT FROM AUTHOR]

We characterize the abelian groups $G$ for which the functors $\mathrm{Ext} (G, - )$ or $\mathrm{Ext} (- , G)$ commute with or invert certain direct sums or direct products. [ABSTRACT FROM AUTHOR]

The optimal shape of a P late- P in- F in H eat S ink with P erforations and S plitters (PPFHS-PS) is designed in this work using the software package CFD-ACE+ and the Levenberg-Marquardt method (LMM) to determine the maximum thermal performance factor η under a fixed fin volume constraint. In the present work, the implementations of perforations and splitters on a pin fin are examined, and the diameter of the pin, the perforated diameter of the pin and the length of the splitter are considered as the design variables. The hydrothermal performances of a P late- P in- F in H eat S ink (PPFHS), a Plate- P in- F in H eat S ink with P erforations (PPFHS–P) and a P late- P in- F in H eat S ink with S plitters (PPFHS–S) are compared. It is found that a great enhancement in the thermal performance factor can be resulted for the PPFHS-PS. The numerical design cases indicated that when considering an incoming velocity of 5.0 m/s, the percentage improvements of η for the PPFHS-P, PPFHS-S and design #2 PPFHS-PS are 4.9%, 5.2% and 10.1% higher than that of the original PPFHS. It indicates that the individual contribution of thermal performance factor improvement of the PPFHS-P and PPFHS-S can be added if the perforations and splitters are utilized simultaneously in the PPFHS-PS design. Finally, experimental verifications are conducted on the manufactured PPFHS-P, PPFHS-S and design #2 PPFHS-PS modules, and the measurement results of the temperature distributions and pressure drops indicate that the experimental data matched quite well with the computational data for those heat sinks. [ABSTRACT FROM AUTHOR]

Low-loss air trench structures that permit reduced-size bends in low (Δ = 0.7-7%) and medium (Δ = 7-20%) index contrast waveguides are demonstrated. Local high index contrast at bends is achieved by introducing air trenches with "cladding tapers" that provide an adiabatic mode transition between low and high index contrast regions. We have fabricated and measured the performance of bends and T-splitters in silica low index contrast waveguides. Complimentary metal-oxide-semiconductor (CMOS) compatible processes are effective in processing, and measured losses are low and consistent with theoretical simulations. [ABSTRACT FROM PUBLISHER]

We explain the physical effects involved in optical coupling in periodic structures which allow for photonic band gaps. We use a simple model to do this, since this allows us to establish some general principles for the operation of such devices. Further, we investigate the choice of parameters, with respect to the band gap, which will allow the device to operate suitably, and we contrast systems with high and low index defects. [Copyright &y& Elsevier]

In all 245 British adults provided self- and parental estimates on a normal IQ distribution scale of the 20 second-order abilities identified by Cattell [Cattell, R. (1971). Abilities: Their structure, growth and action. New York: Houghton Mifflin] as well as their and their parents'' overall (g) IQ. After controlling for age, education, and test experience, there were a number of sex differences but only for self-estimates. Males rated their own score higher than females on 11 of the 20 abilities, the biggest differences being on mechanical ability, spatial ability, numerical ability, and originality. When the 20 estimates were regressed onto the overall estimate, the resulted showed 7 estimates predicted overall score and accounted for 77% of the variance. Exploratory and confirmatory orthogonally and obliquely rotated factor analysis was performed on the 20 self-ratings. This revealed four interpretable factors labelled cognitive, verbal, analytic, and aesthetic. Results suggests that participants are lumpers rather than splitters. There was also little evidence of attributional errors. Results are in accordance with the literature on self-rated abilities. [Copyright &y& Elsevier]

We show that the weighted sum of phase errors of modes of multimode interference (MMI) waveguide is minimum for largest access waveguide width. Also, we show the improvement in the performance of MMI couplers for their use as splitters and sum and difference units by the optimization of access waveguide widths. The optimized access waveguide widths can also be roughly estimated from the characteristic curves of the weighted sum of phase errors of the modes and coupled amplitude at nearby access waveguides by the input itself. [Copyright &y& Elsevier]

In this paper, we present a new methodology for analysis of all-optical fiber-optic code-division multiple-access (FO-CDMA) networks. In this analysis, we propose statistical models, based on photon-counting techniques, for some basic elements of the network, such as splitters, combiners, star couplers, and FO-CDMA passive encoders/decoders. By following the statistical variation of the photon-count of the string of pulses that constitutes the address sequence in an FO-CDMA network, we will be able to reveal the quantum-limited optical signal-to-noise ratio (OSNR) required at the transmitter output to meet the performance limits. Moreover, considering receiver thermal noise and source extinction ratio, we explore the role of using an optical preamplifier before the detector and the dependence of the performance on the transmitted power and the weight of the employed optical orthogonal codes (OOCs). [ABSTRACT FROM PUBLISHER]

Recent advances in low-dimensional materials and nanofabrication technologies have stimulated many breakthroughs in the field of nanophotonics such as metamaterials and plasmonics that provide efficient ways of light manipulation at a subwavelength scale. The representative structure-induced spectral engineering techniques have demonstrated superior design of freedom compared with natural materials such as pigment/dye. In particular, the emerging spectral routing scheme enables extraordinary light manipulation in both frequency-domain and spatial-domain with high-efficiency utilization of the full spectrum, which is critically important for various applications and may open up entirely new operating paradigms. In this review, a comparative introduction on the operating mechanisms of spectral routing and spectral filtering schemes is given and recent progress on various color nanorouters based on metasurfaces, plasmonics, dielectric antennas is reviewed with a focus on the potential application in high-resolution imaging. With a thorough analysis and discussion on the advanced properties and drawbacks of various techniques, this report is expected to provide an overview and vision for the future development and application of nanophotonic color (spectral) routing techniques., (© 2021 Wiley-VCH GmbH.)

The Internet carries a vast range of information resources and services among private, public, academic, business and government networks that are linked by a broad array of electronic, wireless and optical networking technologies. Its performance has become extremely important in view of their ever expanding usage, and the complexity of its functions. However, the fundamental challenges facing Nigerians while trying to access the internet is very obvious, generally to get internet access to Nigerian homes are quite expensive coupled with the problems of poor connection and frequent network breakdown. Cable TV network with the aid of broadband technology have opened up a new realm of information access, storage and delivering of information to the world, internet access inclusive. Our objective in this work is to present a system architecture of internet access via Cable TV network, and propose a mechanism that can proffer solutions to the challenges facing the home internet users in Nigeria with a feasible economic return. [ABSTRACT FROM AUTHOR]