Simulation of loading dynamics and hydrodynamics of drives of forest machine working bodies

The need to take into account the dynamic processes that occur when performing technological operations using the working bodies of forest machines with a hydraulic drive is due to the fact that its absence leads to a distortion of the obtained results, since the kinematic schemes do not take into account the influence of hydraulic fluid in the elements of the hydraulic system. In this regard, it became necessary to develop models that take into account the dynamics of working body loading and the hydrodynamics of its drives. It is recommended to consider the influence of the process dynamics by introducing dynamic factors. The resulting mathematical model allows you to determine the actual values of the hydraulic cylinder, taking into account the errors associated with fluid leakage. As a result of the study, it was possible to connect the pressure change in the hydraulic cylinder, the movement of the pistons in the hydraulic cylinder and the rotor of the hydraulic motor, as well as the appearance of inertial forces. The connecting component is the balance of fluid and hydraulic system volumes.

A wideband, compact, high gain, low-profile, monopole antenna using wideband artificial magnetic conductor for off-body communications

A wideband staircase pattern defected ground monopole antenna integrated with an artificial magnetic conductor (AMC) reflector has been proposed for C-band (4–8 GHz) and ITU band (8.01–8.5 GHz) applications. The integrated antenna consists of a staircase antenna at top, a 2 × 2 AMC reflector at the bottom and an air substrate as gap between them. The AMC offers 18.5% ± 90° reflection phase bandwidth from 6.10 to 7.32 GHz. The AMC layer has achieved mu-negative properties in the designated band. The AMC proffers polarization independent behavior in the respective frequency band depicting robustness in AMC reflection phase characteristics. The integrated antenna has offered a wide impedance bandwidth of 2.78 GHz (42.8% at 6.5 GHz and 34.1% at 8.15 GHz) due to the defected ground monopole. The integration of wideband AMC beneath the staircase monopole antenna alters the out of phase radiation to in-phase planer pattern which enhances the peak gain up to 9.7 dB. It reduces the 1-g averaged specific absorption rate to 0.223 and 0.324 W/kg at the two designated bands. The structure maintains almost similar bandwidth and gain due to artificial human body loading.

A Dual-band Monopole Antenna with EBG for Wearable Wireless Body Area Networks

This paper proposes a dual-band wearable monopole antenna adopting an electromagnetic bandgap (EBG) structure, which operates at 2.45 and 5.8 GHz ISM bands and is suitable for wearable applications. Both the monopole antenna and the EBG structure are fabricated on an F4B semi-flexible substrate having a dielectric constant of 2.2. The EBG structure effectively isolates the human body from the radiation of the antenna and reduces the specific absorption rate (SAR) of it by more than 97.5%. This improves the antenna gain and the peak gain reaches 9.1 dBi at 5.8 GHz. The wearable performance of the antenna showed that it can sustain good performance even under realistic human body loading. Besides, the antenna has a small size, which makes it ideal for wearable applications.

Via-less electromagnetic band-gap-enabled antenna based on textile material for wearable applications

A compact fabric antenna structure integrated with electromagnetic bandgap structures (EBGs) covering the desired frequency spectrum between 2.36 GHz and 2.40 GHz for Medical Body-Area Networks (MBANs), is introduced. The needs of flexible system applications, the antenna is preferably low-profile, compact, directive, and robust to the human body's loading effect have to be satisfied. The EBGs are attractive solutions for such requirements and provide efficient performance. In contrast to earlier documented EBG backed antenna designs, the proposed EBG behaved as shielding from the antenna to the human body, reduced the size, and acted as a radiator. The EBGs reduce the frequency detuning due to the human body and decrease the back radiation, improving the antenna efficiency. The proposed antenna system has an overall dimension of 46×46×2.4 mm3. The computed and experimental results achieved a gain of 7.2 dBi, a Front to Back Ratio (FBR) of 12.2 dB, and an efficiency of 74.8%, respectively. The Specific Absorption Rate (SAR) demonstrates a reduction of more than 95% compared to the antenna without EBGs. Moreover, the antenna performance robustness to human body loading and bending is also studied experimentally. Hence, the integrated antenna-EBG is a suitable candidate for many wearable applications, including healthcare devices and related applications.