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The presence of metallic structures with array of slits, when slits have dimensions much less than the wavelength of the incident optical wave, typically causes extraordinary power transmission. This excellent power transmission indeed comes from the surface waves on the periodic structure excited by the transverse magnetic wave. Here we show that if slits are stepped, then the incident wave power is transmitted into the substrate at desired optical frequency entirely and simultaneously in terahertz frequency band by 70%, for I n 0.53 G a 0.47 A s substrate. Power transmitted through the proposed structure is derived both in a closed form by an analytical model as well as numerically by finite element method. It is found that with the increase of field intensity in the substrate, the structure with array of stepped slits (as opposed to uniform slits) favorably has no reduction of frequency range at maximum transmitted power. [ABSTRACT FROM AUTHOR]

We present a theoretical analysis of multi-photon absorption processes. We find an approximate closed-form expression of the normalized transmittance for a thin sample with two successive nonlinear absorption processes at a time (n - and (n + 1) -photon absorption) in the presence of residual linear absorption. Our approach allows for simultaneous identification and evaluation of the nonlinear absorption coefficients and Rayleigh lengths of the incident elliptic Gaussian beam by fitting the open Z -scan traces. [ABSTRACT FROM AUTHOR]

With the new IEEE 802.11ah standard aimed at improving the existing WLAN standard for the machine-to-machine applications, there is a renewed interest from the research community to analyze and suggest improvements to the standard. With thousands of smart devices and sensors involved in an internet of things network, the interference from multiuser access becomes a serious issue. This paper presents an access point (AP) coordinated multiuser access mechanism for such applications, where the strategy to improve channel usage efficiency is based on analyzing interference present in the neighborhood. Interference experienced in such a system is a function of node location, transmitted power, traffic load and resource allocation. In our proposed system, each WLAN AP from the overlapping basic service sets employs multiple frequency sub-bands and associates user nodes to these sub-bands dynamically. We show that this proposed interference-aware dynamic frequency allocation (IDFA) scheme, which is based on neighborhood contention analysis, can significantly enhance the system throughput and improve the energy efficiency by about 30%. In dense user node deployments, the channel access efficiency of the IDFA multi-band scheme is 2–3 times higher than that of the single band legacy WLAN. [ABSTRACT FROM AUTHOR]

Reflected signal levels in passive RFID require seperate TX and RX antennas to overcome the reader threshold. Using latest improvements, it is shown in this work that both the forward and backward links restrict communication distance given with equations depending upon tag power dissipation, antennas in use, type of modulation and operating environment and parameters to make both distances equal are given. Complete link budget for the forward and backward links in a RFID system are given with constituent parts in detail. After that, to further elaborate on the link budgets, reflection coefficient and power equations are obtained from a RFID front-end model with circuit theory and shown on a passive RFID system. This study shows modulation index m and antenna gain Gt for BPSK and ASK modulations to make two distances equal for the environment to be within, found from two way link equations. Also, ASK and BPSK modulations are compared on communication distance for given average backscatter difference power, minimum SNR to targeted BER on the reader by the equations obtained on the circuit model and MATLAB simulations. [ABSTRACT FROM AUTHOR]

Incident power has an important effect on the optical transmission properties of magnetic fluids. Difference in the effect of the incident power on the optical transmission properties with and without an applied magnetic field was investigated by measuring the transmitted power of the incident light through the magnetic fluid film. In the absence of an applied magnetic field, an approximately linear relationship exists between the incident power and the transmitted power of magnetic fluid films, but the relationship is nonlinear when a magnetic field is applied. Moreover, variation in the optical transmission properties under a magnetic field with various incident powers was measured in experiment. As the magnetic field is enhanced, the transmitted power of the magnetic fluid film first decreases, then increases, and finally reaches saturation. The magnitude of the change in the transmitted power, and the magnetic field range correspond to decreases, increases and saturation are related to the incident power. Therefore, for the sensing applications, depending on the measuring range of the magnetic field and the required variation range of the transmitted power, magnetic fluid film sensors exhibit different characteristics if different incident power values are selected. [ABSTRACT FROM AUTHOR]

Objectives: In this article, we seek to determine how sensitive road cyclists are to vertical vibration transmitted while riding a road bicycle and to propose metrics for the evaluation of dynamic comfort.Background: Road cyclists are exposed to random-type excitation due to road roughness. Vibration transmitted affects dynamic comfort. But how sensitive are cyclists to vibration level? What are the best metrics to measure the amount of vibration transmitted to cyclists? Previous studies used sinusoidal excitation with participants on rigid seats and measured acceleration.Methods: We use a psychophysical estimation of Just Noticeable Differences in Level (JNDL) for vertical vibration transmitted to cyclists on a road simulator. In Experiment 1, we estimate the JNDL for whole-body vibration using vertical excitation on both wheels simultaneously (20 male cyclists). In Experiment 2, we estimate the JNDL at two different points of contact by applying the same signal to only the hands or the buttocks (9 male cyclists).Results: The JNDLs are expressed in terms of acceleration and power transmitted to the cyclist. We compare the JNDLs expressed with these 2 metrics and measured at different points of contact.Conclusion: Using these two metrics and at all points of contact, vibration magnitude needs to be reduced by at least 15%, for the change to be detectable by road cyclists.Application: A road bicycle needs to transmit at least 15% less vibration for male cyclists to detect an improvement in dynamic comfort. Dynamic bicycle comfort can be measured in terms of a new metric: power transmitted to the cyclist. [ABSTRACT FROM AUTHOR]

The authors present here designs for tuneable confined Tamm plasmons (CTPs) resonant at 1.3 μm, consisting of an AlAs/GaAs distributed Bragg reflector and gold disc. Using numerical methods they explored the effect of disc diameter on the CTP resonance and position of a dipole source (modelling a quantum dot) on emission through the disc. They found decreasing disc diameter resulted in a blue‐shifted fundamental mode and that a dipole positioned at the centre of the disc emitted with an angular distribution that collected 90% of the transmitted power within a numerical aperture of 0.7. They also explore the Purcell enhancement under the CTP as a function of dipole position. [ABSTRACT FROM AUTHOR]

Performance of waveguides for long-distance energy transport in microwave heating was evaluated by comparing the microwave propagation characteristics, including maximum transmitted powerPtrans, attenuation constant α and percentage of power lossplossproposed in this study, of commercially available rectangular waveguides (WRs) constructed of various metals (Ag, Cu, Ag, Al and Fe) for microwave heating at 0.915 and 2.45 GHz with those of different types of circular waveguides, namely circular waveguides with the same cut-off frequency as rectangular waveguides (denoted by WCFs), circular waveguides with the size equal to rectangular waveguide (denoted by WCDs), and circular waveguides with the same circumference as rectangular waveguides (denoted by WCCs). It is demonstrated that WCFs exhibit the highest values of maximumPtranstogether with lowest α andplossdue to their characteristics of microwave field configuration. Circular waveguides (e.g. WCF1150) made of Cu or Al with large dimensions operating at 0.915 GHz are suitable for microwave heating through long-distance microwave energy transport over the distance compared to traditional rectangular waveguides, with up to ∼50% reduction of power loss. Optimal waveguides for long-distance uses can be obtained by assessing microwave propagation characteristics together with manufacturing cost, depending on specific applications. [ABSTRACT FROM AUTHOR]

This article presents a linear power division algorithm to achieve almost constant modulated stimulated Raman scattering power. This assumes a linear variation of power in a channel with respect to another, which is a result of experimental verification. During this study, variation of signal power from 1 to 60 mW was done, and the number of channels varied from 3 to 99. [ABSTRACT FROM AUTHOR]

In this paper, we investigated specific properties and features of several kinds of Y-splitters based on gold nanorings arrays which are surrounded by SiO2 host substance, to be used at C-band spectrum (γ ~ 1550 nm). The comparison between two kinds of splitters shows that the symmetric splitter demonstrates better performance than the asymmetric splitter at given wavelength with high efficiency and transmittance (power ratio). Calculations proved that the transmitted power percentage was approximately ~47.5% in the well-organized splitter. It is shown that the offset distance plays an important role in the quality of the optical energy division and transmission through the plasmonic waveguide. The influence of increasing and decreasing in the offset distance was demonstrated numerically by snapshots. Hence, choosing and determining the appropriate value for the offset distance lead to the structure with lower losses and higher percentage in energy transmission. Ultimately, the optical behavior of an asymmetric nanostructure with unequal distances between the arms and the main array is investigated and its applications and possible purposes are introduced. [ABSTRACT FROM AUTHOR]

Abstract: Simulation results of a 863–870MHz frequency-hopped spread-spectrum (FHSS) transceiver with binary frequency shift keying (BFSK) modulation at 20kb/s for wireless sensor applications is presented. The transmit/receive RF front end contains a BFSK modulator, an upconversion mixer, a power amplifier (PA), and an 863–870MHz band pass filter (BPF) at the transmitter side and a low-noise amplifier with down conversion mixer to zero-IF, a low-pass channel-select filter, a limiter and a BFSK demodulator at the receiver side. The various block parameters of the transmit/receive RF front end like noise figure (NF), gain, 1dB compression point (P-1dB), and IIP3 are simulated and optimized to meet low power and low cost transceiver specifications. The transmitter simulations show an output ACPR (adjacent channel power ratio) of −22dBc, 3.3dBm P-1dB of PA, and transmitted power of 0dBm. The receiver simulations show 51.1dB conversion gain, −7dBm IIP3, −15dB return loss (S11), and 10dB NF. Low power arctangent-differentiated BFSK demodulator has been chosen and the BER performance has been co simulated with the analog receiver. The complete receiver achieves a BER of 10−3 at 10.5dB of EbtoNo. The transceiver simulations show an RMS frequency error of 1.45kHz. [ABSTRACT FROM AUTHOR]

Light trapping or absorption is a key concept for design and fabricating solar cells. The propagation of electromagnetic waves through a multilayered solar cell containing organic materials has theoretically investigated. In particular, the reflected, transmitted, and absorbed powers are found and defined. The main parameters of the structure and the required equations for TE polarization are presented in detail. The boundary conditions of the electric and magnetic fields of the incident waves are imposed at each interface and Snell's law is applied. Expressions for the overall reflection and transmission coefficients are provided by a recursive method. The reflected, transmitted, and absorbed powers are determined using these coefficients. In the numerical results, the mentioned powers are computed and illustrated as a function of the angle of incidence, the wavelength, and the thickness of the active layer when the extinction coefficient of the active layer changes. [ABSTRACT FROM AUTHOR]

Low delay and long lifetime are a very important issue for industrial wireless sensor networks (IWSNs) in which it require long-time monitoring of industrial sites and respond quickly to events that is monitored; therefore, high delay communications can cause serious damage to property and personnel at industrial field. Due to delay, lifetime, and other performance involved to multiple layers, it is difficult to optimize from a single layer. Therefore, a cross-layer design optimal scheme for reducing delay and maximizing lifetime (RDML) scheme is proposed for IWSNs which is from several layers such as transmitted power, duty cycle, and node deployment positions to optimize the network performance of delay and lifetime etc. Firstly, due to the node which sends a packet within a cycle, different duty cycle leads to different selection of the modulation level, resulting in different power consumption efficiency of transmitting data. Through careful analysis, the optimal value of the duty cycle is given which has the lowest energy consumption per bit. In fact, the energy consumption of the node is not balanced. Therefore, an optimization method of changing the duty cycle is proposed. In this paper, larger duty cycle is chosen for nodes with residual energy to improve the reliability of data transmission, reducing the probability of data retransmission, so that the network delay can be reduced in IWSNs. Third, based on the previous analysis, a network optimization deployment algorithm is proposed, which not only maximizes the energy efficiency of a single node but also maximizes the network lifetime and the total network energy efficiency. Both our comprehensive theoretical analysis results indicate that the performance of RDML scheme is better than the previous studies. Relative to equal distance and optimal duty cycle scheme, the RDML scheme can reduce the delay by 19-30% and increase the lifetime by more than 43%. [ABSTRACT FROM AUTHOR]