Minimum Transmission Research Articles

The nexus of sustainability and damping: A quasi-zero stiffness and pseudo-piecewise inerter damper for vehicle suspension

This paper proposes a vibration control-energy harvesting damper (VCEHD) for vehicle suspension. The principles used in the proposed VCEHD include quasi-zero stiffness (QZS), mechanical motion rectifier (MMR), and semi-active control. In the dynamic analysis, the authors found that the inherent disengagement and engagement properties of the MMR can undermine the robustness of the system, that is, the inherent properties of the MMR as an energy harvesting device are not conducive to vibration isolation. Therefore, it needs to be restrained. According to the numerical simulation results, VCEHD cannot simultaneously achieve the minimum body displacement and the maximum energy harvest, and the energy harvest performance needs to be partially sacrificed. The experimental results show that the maximum energy output is 14.70 mW/kg, and the minimum displacement transmissibility is 24.32%. Combined with the numerical simulation results, VCEHD can harvest 8.82–97.79 W of power in actual vehicle running, which can provide auxiliary power for intelligent vehicles.

Hyperbranched polyborosilazanes derived SiBCN ceramic for high-temperature wave-transparent performance

Polymer-derived ceramics (PDCs) is a promising way to prepare ceramic-based electromagnetic functional materials, which can conveniently modulate the composition and dielectric properties of the ceramics. In this paper, SiBCN ceramic matrix composites with excellent high-temperature wave-transparent performance were prepared through PDC method. Three hyperbranched polyborosilazanes (PBSZs) were prepared by adjusting the type of chlorosilane monomers containing different numbers of methyl groups. The carbon element of pyrolytic ceramics was tuned by adjusting the molecular structure of the precursor and the pyrolysis temperature. The lower the methyl number and pyrolysis temperature, the lower the dielectric constant of the polymer-derived SiBCN ceramics, which is favorable for electromagnetic wave (EMW) transmittance. The average EMW transmittance of SiBCN-C pyrolyzed from hyperbranched PBSZ using trichlorosilane at 1000 °C was 90.56 % at room temperature. More excitingly, the excellent wave-transparent performance was also maintained in the temperature range of 100–800 °C. At the test temperature of 800 °C, SiBCN-C-1000 still had excellent wave-transparent performance with minimum and average EMW transmittance of 76.13 % and 88.96 %, respectively. This paper provided a new idea for the preparation of high-temperature wave-transparent SiBCN composite ceramics.

Trend analysis of malaria surveillance data in West Wallaga, West Oromia, Ethiopia: a framework for planning and elimination

BackgroundAlthough Ethiopia has made a remarkable progress towards malaria prevention and control, malaria remains one of the most devastating parasitic diseases affecting humans. However, the distribution and transmission of malaria varies across the country. The study aimed to describe 5 years of malaria distribution and magnitude within the West Wallaga Zone and its respective woredas.MethodsA retrospective cross-sectional study design was conducted from April 10, 2019 to May 2019. Surveillance data collected weekly for a 5-year (2014–2018) from health facilities and private clinics that were archived in zonal PHEM database were reviewed. The checklist contained variety of variables was developed to collect data. Descriptive analysis was conducted to determine the proportion of Plasmodium species, positivity rate, mortality and fatality rate, time trend, and admission status; and presented by text, tables and figures.ResultsOf the total of 588,119 suspected malaria cases, 78,658 (43/1000 populations) were positive with average positivity rate of 13.4%. Among confirmed cases, 59,794 (75%) of cases were attributed to Plasmodium falciparum, 16,518 (20%) were Plasmodium vivax, and 2,360 (5%) were mixed infections. The maximum (145,091) and minimum (74,420) transmissions were reported in 2014 and 2018, respectively. There was seasonal variation in transmission; spring (from May to July) and also autumn seasons (from October to November) were found as malaria transmission peaks. Although incidence rate declined throughout the study period, the average annual incidence rate was 14.38 per 1000 populations. The average case fatality rate of 5 consecutive years was 12/78,658 (15/100,000) population.ConclusionAlthough the malaria prevalence was decreased, the mortality due to malaria was increased in the 5-year study period, and malaria is still among the major public health problems. The dominant species of malaria parasites were P. falciparum and P. vivax. Attention is needed in scaling-up vector control tools in high malaria transmission periods.

Fair Resource Allocation in Virtualized O-RAN Platforms

O-RAN systems and their deployment in virtualized general-purpose computing platforms (O-Cloud) constitute a paradigm shift expected to bring unprecedented performance gains. However, these architectures raise new implementation challenges and threaten to worsen the already-high energy consumption of mobile networks. This paper presents first a series of experiments which assess the O-Cloud's energy costs and their dependency on the servers' hardware, capacity and data traffic properties which, typically, change over time. Next, it proposes a compute policy for assigning the base station data loads to O-Cloud servers in an energy-efficient fashion; and a radio policy that determines at near-real-time the minimum transmission block size for each user so as to avoid unnecessary energy costs. The policies balance energy savings with performance, and ensure that both of them are dispersed fairly across the servers and users, respectively. To cater for the unknown and time-varying parameters affecting the policies, we develop a novel online learning framework with fairness guarantees that apply to the entire operation horizon of the system (long-term fairness). The policies are evaluated using trace-driven simulations and are fully implemented in an O-RAN compatible system where we measure the energy costs and throughput in realistic scenarios.

Multiple ultra-narrow band-stop filters based on MIM plasmonic waveguide with nanoring cavities

In this work, multiple ultra-narrow band-stop filters based on metal–insulator–metal (MIM) plasmonic waveguide filters with high efficiency are designed and analyzed numerically. The relationship between incident radiation and transmission spectra is investigated between 0.45 μm and 1.5 μm in the electromagnetic spectrum by finite-difference time-domain (FDTD) method. The designed structures have a bus waveguide coupled with nanoring cavity resonators of different sizes. Minimum transmission is 1.3% at 622 nm. The full width at half maximum (FWHM) is 8.64 nm and the quality factor is obtained as 72.33 in this wavelength. The highest quality factor is 185.48 and the lowest FWHM is 4.2 nm at 779 nm. The designed waveguide-based filters can be used for integrated optical devices from visible to near-infrared regimes.

Effects of thickness and roughness on plasmonic characteristics of gold thin films deposited on polished optical fiber

The thickness and roughness of metal layers substantially affect the performance of surface plasmon resonance (SPR)-based sensors. The deposition methods, control parameters, and substrate characteristics influence the layer thickness and roughness. This study investigates the SPR characteristics of a polished optical fiber surface coated with gold (Au) metal of different thicknesses. The Au layer is deposited via the thermal evaporation method, and its thickness is varied by controlling the deposition time (3–6 min). A proportionality relationship between thickness and deposition time is observed. Island-shaped structures in gold (Au) morphology are formed due to low adhesion to the substrate. The shape of this island creates gaps in the layer, causing scattering. In addition, the roughness on the gold surface triggers the Localized Surface Plasmon Resonance (LSPR) phenomenon. As a result, the measured dielectric characteristics differ from the reference. The SPR curve calculation simulation was carried out based on reference optical parameters and measurement results by an ellipsometer, which were then compared with experiments. The obtained results show that the substrate roughness, morphology, and thickness of the Au layer play an essential role in determining the characteristics of the SPR curve in a fiber optic plasmonic sensor. As a result, in basic experiments, the sample with an Au thickness of 27.37 nm (deposition time = 3 min) shows better characteristics (half-maximum full width, minimum transmittance, and resonance wavelength) compared with the sample with an Au thickness of 53.97 nm (deposition time = 4 min), Although 53.97 nm is the optimal thickness from the simulation using reference optical parameters (smooth substrate surface and smooth gold layer).

An ultra-wideband plasmonic reflector based on local resonant bandgap and Bragg bandgap

Unlike previous reports that utilized periodic modulation of insulation layer thickness or dielectrics, we propose the use of split ring resonators (SRRs) and their arrays to modulate the propagation characteristics of MIM plasmon waveguides. Due to the strong resonance backscattering of SRR, resonance transmission valleys appear in the transmission spectra of MIM waveguides. Changing the size of SRR can achieve continuously adjustable positions of resonance transmission valleys. The introduction of SRRs periodic arrays will result in two bands (bandgaps) with transmission minimum in the transmission spectra. Combining the dependence of the two bandgaps on the array period and the field distribution, the two bandgaps are Bragg bandgaps and local resonance bandgaps, respectively. By modulating the local resonance bandgap, the Bragg bandgap can be tuned. The introduction of local bandgap increases the degree of freedom to modulate the transmission characteristics of MIM waveguides. Combining local resonant bandgap and Bragg bandgap can significantly increase the reflection bandwidth, achieve broadband filtering, and facilitate the miniaturization of waveguide devices.

Study on the performance of a novel 1DOF isolator with QZS characteristics

A typical one-degree-of-freedom (1DOF) shock isolator that has quasi-zero stiffness (QZS) characteristics consists of two transversal springs and one portrait spring. The transversal springs can provide negative stiffness and the vertical spring is used as a load-bearing component. In this article, an improved 1DOF QZS shock isolator is obtained by utilizing the combination of lateral bars and springs. The displacement transmissibility under the harmonic excitation is obtained and the principle of minimum displacement transmissibility under the condition of system stability is proposed. Finally, numerical simulation is conducted, and the simulation results reflect that the proposed 1DOF QZS isolator significantly performs better than the previous one.

Modeling and admittance recursive simulation of anti-reflective coatings for photothermal conversion: synergy between subwavelength structures and gradient refractive index layers.

In the field of photothermal conversion, light-absorbing layers show limitations such as low solar energy utilization and excessive surface reflection. This paper proposes a new anti-reflective coating consisting of a gradient-doped fluorescent glass film covering a subwavelength structural layer for photothermal conversion. Its transmittance was simulated using equivalent medium theory and the admittance recursion method. The subwavelength structure provides a refractive index gradient, and its shape solves the problem of the sharp decrease in transmittance at high angles of incidence. Subsequently, we adjust the material parameters of the gradient refractive layers and control the thickness of each layer to minimize interlayer Fresnel reflections. Finally, the efficient light-trapping ability of the model was verified by calculating and comparing the transmittances of the optimized model and bare glass. Notably, within the visible spectrum, our model achieves an average transmittance of over 95% across wavelength and angle ranges, effectively suppressing surface reflections. At a larger light incident angle, the transmittance increases by 29.7%, and the minimum angle transmittance reaches 92.7%. This study proposes an innovative method to enhance the performance of transmission layers in photothermal conversion devices.

Extraordinary transmission of intense short laser pulse through thin foil with near- and sub-wavelength slits

To supplement our earlier study [Lu et al., AIP Adv. 10, 015209 (2020)] on the propagation of intense short laser pulse through foils with multiple sub-wavelength sized slits, here, we consider the effects of the interaction parameters on the occurrence of extremums in the light transmission. Our results suggest that for periodic slit distribution, maximum and minimum transmissions occur for L ± d = κλ and L = κλ, respectively, where L and d are the period and width of the slits, respectively, λ is the laser wavelength, and κ is a positive integer or a rational number.

Investigation on nonlinear absorption and optical limiting properties of Tm:YLF crystals

Nonlinear optical limiting has recently attracted significant attention, thanks to the continuous development of laser technology. In order to explore more potential functional materials, the spectral and nonlinear optical properties of yttrium lithium fluoride doped with thulium (Tm:YLF) crystals are reported. Absorption and emission spectra of Tm:YLF are measured, and the absorption peaks correspond to the energy transition of Tm3+. Nonlinear absorption measurements are performed on crystals with different thulium doping concentrations (2.0 %, 2.5 %, and 3.0 %). The Z-scan results indicate the presence of two-photon absorption processes at 1064 nm pulse laser. Additionally, we measured the nonlinear transmittance of Tm:YLF crystals with various thulium doping concentrations and lengths to evaluate their nonlinear optical limiting performance. For the 2.5 % doped Tm:YLF crystal with 20 mm length, the maximum transmittance at low laser intensity is 73.9 %, and the minimum transmittance at high laser intensity is 38.1 %. These experimental results suggest that Tm:YLF crystals may have potential as solid-state nonlinear optical limiting materials.

Hybrid multi-channel electrically tunable bandstop filter based on DAST electro-optical material

A voltage tunable hybrid multi-channel bandstop filter based on a metal–insulator–metal (MIM) waveguide is presented in this work, which can realize three narrowband and one broadband filtering functions simultaneously. The filter comprises two asymmetric composite cavities, which are filled with organic electro-optical material of 4-dimethylamino-N-methyl-4-toluenesulfonate (DAST). The composite cavity is composed of a rectangular cavity and an annular cavity, and the annular cavity is formed by two rectangular cavities connected with two semi-elliptical annular cavities. The transmission spectrum and magnetic field distribution of the filter are studied and analyzed by the finite element method (FEM), and the effects of the structure parameters on the transmission spectrum are discussed. Our analysis indicates that the bandstop filter has minimum transmittances of 0.02%, 0.29%, and 0.1%, minimum bandwidths of 5 nm, 9 nm, and 25 nm, and maximum quality factors (Q) of 123.7, 87.1, and 44.2, respectively, in three narrowband modes. The stopband bandwidth at the broadband mode is 70 nm, and the adjustable range is 1695–2065 nm. Additionally, the filter characteristics can be adjusted by imposing a control voltage, providing a high degree of tunability and maintaining stable filter performance. Finally, the basic structure is optimized yielding an increased bandwidth of 238 nm for the broadband mode, which does retain great electrical tuning characteristics. Consequently, the proposed structure can be applied with huge potential in high-density integrated circuits and nano-optics.

Design and fabrication of large-mode-area multicore chalcogenide fiber with low bending loss.

Multicore fiber (MCF) has a larger mode-area (LMA) compared to traditional single-core fiber, making it easy to get a mode area of more than 3000 µm2 with an optimized MCF structure. Here, a fine-structured 19-core fiber based on chalcogenide glass was fabricated using a combined method involving extrusion, drilling, and rod-in-tube for the first time. The fiber has a minimum transmission loss of 1.8 dB/m at 6.7 µm. When the bending radius exceeds 6 cm, a low bending loss of about 0.6 dB appears, and the experimental data are in good agreement with the simulation results. In addition, the supermode characteristics of the 19-core fiber are analyzed from both perspectives of simulation and experiment, and these results are perfectly in good agreement. We believe it opens a new way to develop high-power and bend-resisting fiber with such kind of multicore structure.

Preparation and characterization of electrospun cellulose nanocrystals-reinforced trans-1,4-polyisoprene nanocomposite elastomeric fiber membranes

To overcome the limitations of low strength of conventional electrostatic spinning trans-1,4-polyisoprene (TPI) fiber membranes, cellulose nanocrystals (CNC) were added into the TPI spinning solution as a backbone material, and CNC/TPI nanocomposite elastomeric fiber membranes were prepared using electrostatic spinning. This study examined the effect of CNC content on the morphology, mechanical properties, and hydrophilicity of the electrostatically spun CNC/TPI nanocomposite elastomeric fiber membranes. The prepared CNC/TPI nanocomposite elastomeric fiber membranes were characterized using 3D measurement laser microscopy, tensile testing, Fourier-infrared spectrometry, thermogravimetric analysis, differential scanning calorimetry, and water contact angle. With increase in CNC content, the tensile strength of the nanocomposite elastomeric fiber membrane increased from 1.79 MPa (without CNC) to 10.28 MPa (with 1 wt% CNC), the average diameter first decreased and then increased, the thermal stability and water vapor transmission rate decreased, and the water contact angle gradually increased. The maximum water contact angle was 124.27° and the minimum water vapor transmission rate was 851.41 g/m2·24 h. The proposed high-strength hydrophobic breathable fiber membrane preparation method can be used in various fields such as high-strength waterproof/breathable protective clothing and wearable electronic devices.

Low terahertz frequency on-chip multi-functional modulator with amplitude and phase modulation

Terahertz amplitude and phase modulation technologies are crucial for terahertz communication, radar, and imaging. However, most current approaches can only achieve either amplitude or phase modulation. In this paper, we present a low terahertz frequency on-chip multi-functional modulator that consists of a hybrid coupler and reflection meta-structure. High-performance amplitude modulation is achieved by combining series resonant absorption of series coupling branch with resonance enhancement of parallel coupling branch in the reflection meta-structure. Meanwhile, the enhanced resonance provides a larger range of phase shifts, enabling effective amplitude and phase modulation in two different frequency regions. Therefore, we realize an amplitude modulation in the range of 115–135 GHz with a minimum transmission loss of 4 dB and a modulation depth of over 10 dB. At the same time, we achieved a continuous phase shift in the 103–113 GHz region, as well as a 180° two-bit phase shift in the 107–109 GHz range with only 5.7 dB transmission loss. Our simple method for terahertz amplitude and phase multi-functional modulation offers the potential to construe terahertz multifunctional integrated systems.

Whole Life Cycle Cost Analysis of Transmission Lines Using the Economic Life Interval Method

With the large-scale construction and commissioning of transmission lines over the past two decades, the grid is facing a large-scale centralized decommissioning of transmission lines. The transmission line’s economic life is crucial to rationalizing its construction and reducing the grid’s development costs. Based on the minimum economic life calculation principle, the static and dynamic transmission line economic life calculation model is established, considering the whole life cycle for transmission line cost. The improved gray GM (1,1) model is applied to forecast cost data during the economic life assessment of transmission lines with fewer samples. Considering the cost uncertainty in life-cycle costing, the interval cost model based on the coefficient of variation wave amplitude is proposed to determine the economic life intervals under different guarantees by using the normal distribution probability density function, which reduces the influence of cost fluctuations on the economic life calculation error. The economic life analysis of a 500 kV transmission line is used as a case study to verify the model’s accuracy and effectiveness. The method shows the economic life intervals under different guarantee degrees based on the most probable economic life determination, which provides theoretical support for calculating the economic life elasticity of transmission lines.

Distributed soft video transmission based on hybrid digital and analog scheme

This study presents a novel distributed soft video delivery scheme using hybrid digital and analog framework, which realizes a relatively lightweight encoder as well as good robustness. Specifically, after applying scalar quantization to the interframes, the scaled analog information (quantization error) and the scaled digital information (quantized source) are superimposed and then transmitted. In this way, the proposed scheme directly delivers pseudo-analog symbols over the orthogonal frequency division multiplexing (OFDM) channels and involves no complicated digital codec. Moreover, we utilize cross-frame correlation to implement a distributed paradigm which further reduces the encoder complexity since the complex motion estimation and compensation algorithms are transferred to the decoder. Accordingly, the power distortion optimization scheme, which resolve the allocation of power and the parameters optimization to achieve minimum transmission distortion, is proposed. To solve it, first, we formulate the power distortion expressions regarding quantization parameters and power allocation coefficients. Subsequently, we divide the problem into two sub-problems based on the fast coordinate descent method and further propose a greedy iterative algorithm to optimize them. We also develop a data-driven optimization algorithm based on deep learning that reduces the additional delay brought by the iterative optimization method. At the receiver, we estimate the quantization output and quantization error by the modified linear least squares estimation with the virtual noise variance. Based on the simulation results, the proposed framework has a better performance in terms of peak signal-to-noise ratio and structural similarity than the relevant cutting-edge schemes while maintaining good robustness.

Optimization and biodynamic modelling of a 3D-printed honeycomb cushion and double-diamond seating suspension system for vibration isolation

Extended periods of driving, lasting up to 8 hours, can have a severe impact on a driver's health due to the presence of low-frequency vibrations caused by uneven road surfaces. This paper presents a novel biodynamic system modelling method for investigating how the human body responds to low-frequency vibrations. The lumped biodynamic parameter model predicts time-domain head acceleration and frequency-domain transmissibility ratio. This paper's design innovation involves a three-dimensional printed cushion composed of honeycomb cells and a seating suspension system featuring six double-diamond isolators. Using the Design of Experiments, Response Surface Method, and Genetic Algorithm methods, the structural parameters of the seating suspension system and cushion in the model are optimized for the minimum peak transmissibility ratio. The uniqueness of this paper's approach lies in its sensitivity analysis and optimization of the seat cushion and seating suspension system design parameters within a quarter-vehicle suspension system environment, which sets it apart from other literature. Furthermore, this paper explores the connection between the negative Poisson's ratio and quasi-zero stiffness as a means of reducing vibration transmission.

Strategies to enhance the attenuation band in finite beams using periodic attachments

One-dimensional waveguides, such as beams are frequently found in structural engineering applications. A finite periodic structure composed of a beam with periodically spaced vibration absorbers is considered in this work. Additionally, the behaviour of the structure when a hinge condition is imposed between adjacent cells is investigated. Based on the dynamic stiffness matrix approach, the transverse displacement transmissibility is evaluated for a single cell. The effectiveness of using appropriately tuned vibration absorbers in the formation of a smooth super attenuation band is demonstrated. Prediction of the attenuation band is also discussed for a structure with several periodic cells. In addition, the effect of hinge connections between the cells on the boundary frequencies of the attenuation band and the minimum transmissibility is presented.

Construction of a simulated dynamic model of data packet routing on a telecommunication network fragment

The object of the current research is the process of routing data packets in a telecommunications network. It was established that the state and parameters of data transmission channels and routers could have a negative impact and need to be taken into account in the process of modeling the routing of data packets in telecommunication networks. A model of simulated dynamic modeling of data packet routing in telecommunication networks has been devised and proposed. The suggested model makes it possible to establish quantitative values of the delay time of processing data packets during their routing along a separate segment of the telecommunications network, taking into account the state and parameters of the data transmission channel and routers. It has been established that the achievement of the minimum delay time of data packets during routing is achieved by choosing the path of their transmission under the condition of minimum transmission time by communication lines and the capabilities of routers in terms of their accumulation and service speed. At the same time, the reduction of packet transmission delay time relative to the average for the time network segment can reach from 21 to 38 percent. It is shown that the main factor affecting the value of the delay time is the speed of data processing along the selected path of packet transmission. The number of routing nodes in a separate data transmission path can affect the delay time only if the parameters of the routers are equal compared to others that are included in alternative routes. The model of simulated dynamic modeling of data packet routing reported in this work, unlike the existing ones, takes into account the state and parameters of data transmission channels and routers. It can be used in practical improvement of existing and development of new multi-service telecommunication communication networks