Behavioral Measures of Cochlear Gain Reduction Depend on Precursor Frequency, Bandwidth, and Level

Sensory systems adjust to the environment to maintain sensitivity to change. In the auditory system, the medial olivocochlear reflex (MOCR) is a known physiological mechanism capable of such adjustment. The MOCR provides efferent feedback between the brainstem and cochlea, reducing cochlear gain in response to sound. The perceptual effects of the MOCR are not well understood, such as how gain reduction depends on elicitor characteristics in human listeners. Physiological and behavioral data suggest that ipsilateral MOCR tuning is only slightly broader than it is for afferent fibers, and that the fibers feed back to the frequency region of the cochlea that stimulated them. However, some otoacoustic emission (OAE) data suggest that noise is a more effective elicitor than would be consistent with sharp tuning, and that a broad region of the cochlea may be involved in elicitation. If the elicitor is processed in a cochlear channel centered at the signal frequency, the growth of gain reduction with elicitor level would be expected to depend on the frequency content of the elicitor. In the current study, the effects of the frequency content and level of a preceding sound (called a precursor) on signal threshold was examined. The results show that signal threshold increased with increasing precursor level at a shallower slope for a tonal precursor at the signal frequency than for a tonal precursor nearly an octave below the signal frequency. A broadband noise was only slightly more effective than a tone at the signal frequency, with a relatively shallow slope similar to that of the tonal precursor at the signal frequency. Overall, these results suggest that the excitation at the signal cochlear place, regardless of elicitor frequency, determines the magnitude of ipsilateral cochlear gain reduction, and that it increases with elicitor level.

Method of assessing the reduction of solar heat on window surface shaded by continuous vertically slanted shading devices

The research discusses calibration of the method used to calculate solar heat transfer through shaded windows with continuous vertical slanted shading devices (below is abbreviated as "vertical slanted fins") with any slant angle Θ through a radiation reduction coefficient - Kbt. In order to evaluate the reduction of solar heat on window surface shaded by shading devices, a designated coefficient β of solar heat gain reduction through glazed windows should be established. It is the ratio of the transmitted amount of solar heat (including direct and diffuse radiation) through windows with shading device QK to those without solar shading device QKo. The study also introduces two in-house software programs. These programs help calculating solar heat gain and coefficient β for vertically slanted fins with any slant angle θ for 16 window orientations. The results of this study will be applied to the implementation of the Vietnamese national code QCVN 09:2017/BXD towards energy efficiency in buildings.

Assessment of the energy efficiency of a window system with a shading device of the egg-crate type

Introduction. The article proposes a new energy efficiency assessment method based on a new technique used to calculate the window heat gain. The proposed method takes account of the coefficient of irradiance reduction by the sun shading device. The study was carried out for the shading device of the egg-crate type. Materials and methods. Calculations are based on the projection of a sunbeam performed for a fraction of a window area in the shade. They take account of the coefficient of irradiance reduction applied due to the presence of the sun shading device. A shading device reduces the irradiance, caused by diffused solar radiation, and coefficient Kbt is applied to demonstrate this process. This coefficient was identified in an experiment and expressed in the form of regression equations. To evaluate the energy efficiency with regard for the effectiveness of shading devices, coefficient of solar radiation gain reduction β was developed. This coefficient is described by the ratio of the value of solar radiation incoming through a glazed window in the presence of shading device QK to the value of solar radiation incoming through a glazed window that has no shading QKo. The software programme was used to verify the calculations of the heat gain from the solar radiation incoming through the window system with regard for the shading device in various geographical regions in summer (in Hanoi and Moscow). Results. The results, obtained using the proposed methodology and the observation data, show an insignificant difference in the relative value of β; and they demonstrate a major error when qwindow, or the absolute value of heat entering the room, is taken account of. The heat load, incoming through the window system, is down by 42–45 % in Moscow and by 45–53 % in Hanoi in the hottest period of the year if shading devices are used. Conclusions. The proposed methodology and computer software, used for a quick assessment of the energy efficiency of a window system equipped with shading devices, allow to design building envelopes that feature high energy efficiency in terms of air conditioning systems, given that coefficient of radiation gain reduction β is taken account of.

Circularly Polarized Dual-Band LoRa/GPS Antenna for a UAV-Assisted Hazardous Gas and Aerosol Sensor

UAV assisted wireless sensor networks play a key role in the detection of toxic gases and aerosols. UAVs can be used to remotely deploy sensor nodes and then collect gas concentration readings and GPS positioning from them to delimit an affected area. For such purpose, a dual-band communication system is required, supporting GPS reception, and sensor reading data transfer, which is chosen to be at 2.4 GHz using LoRa physical layer. In this work we propose a switched-beam antenna subsystem for the sensor nodes capable not only of satisfying the dual band requirements but also of maximizing communication range or energy consumption through a good antenna polarization match and improved antenna gain. This antenna subsystem is built using dual-port, dual-band, circularly polarized antenna elements, whose design and experimental validation is carefully detailed. A low profile microstrip stacked structure has been used to obtain return loss in both bands better than 15 dB, axial ratios below 1.5 dB, and wide −3 dB beamwidths around 90° and 75° for GPS and 2.4 GHz bands, respectively, thus limiting the gain reduction of the switched-beam system in critical sensor orientations. Special attention has been paid to reduce the coupling between both ports through the optimization of the relative placement of both patches and their feeding points. The measured coupling is below −30 dB.