Passive Solutions Research Articles

Broadband sound attenuation by metaliner under grazing flow

Acoustic liners are the most effective passive solution to noise emission from ducts but still suffer from the drawbacks of narrow-band performances and thick structures for the conventional designs. Here, we present an acoustic metaliner capable of high-efficiency broadband sound attenuation under grazing flow. The metaliner is composed of a perforated plate and a metasurface consisting of a series of neck-embedded Helmholtz resonators (NEHRs). By tuning the nonlocal coupling among the NEHRs and the perforated plate, efficient broadband impedance modulation can be realized, leading to a strong dissipation of broadband sound energy under various speeds of grazing flow. We theoretically and experimentally investigate a well designed metaliner, which can strongly attenuate sound energy for a wide frequency range from 800 Hz to 3000 Hz, both in the absence of air flow and in the presence of grazing flows with speeds from 10 m/s to 60 m/s. Besides, the thickness of the metaliner is only 40.5 mm. Our work provides a route to reduce flow-related noise in a broad frequency range and may find applications in airplane propulsion systems, air-conditioning systems, and other mechanical systems with flow.

On the Efficacy of Water Transport in Leaves. A Coupled Xylem-Phloem Model of Water and Solute Transport

In this paper, we present and use a coupled xylem/phloem mathematical model of passive water and solute transport through a reticulated vascular system of an angiosperm leaf. We evaluate the effect of leaf width-to-length proportion and orientation of second-order veins on the indexes of water transport into the leaves and sucrose transport from the leaves. We found that the most important factor affecting the steady-state pattern of hydraulic pressure distribution in the xylem and solute concentration in the phloem was leaf shape: narrower/longer leaves are less efficient in convecting xylem water and phloem solutes than wider/shorter leaves under all conditions studied. The degree of efficiency of transport is greatly influenced by the orientation of second-order veins relative to the main vein for all leaf proportions considered; the dependence is non-monotonic with efficiency maximized when the angle is approximately 45° to the main vein, although the angle of peak efficiency depends on other conditions. The sensitivity of transport efficiency to vein orientation increases with increasing vein conductivity. The vein angle at which efficiency is maximum tended to be smaller (relative to the main vein direction) in narrower leaves. The results may help to explain, or at least contribute to our understanding of, the evolution of parallel vein systems in monocot leaves.

Smart Alpha: active management with unstable and latent factors

Factor investing has attracted increasing interest in the investment industry because purely active and passive solutions have underperformed. Its success depends critically on identifying the factors involved and timing this well, but this is hard to do because there is such a zoo of factors, and those factors and their loadings are time-varying. We thus propose an investment rule that we call ‘Smart Alpha’, which avoids betting on a-priori factors but focuses instead on an active approach that minimises the exposure of the portfolio to systematic sources of risk while maximising its alpha. This means our choice is to bet on alphas instead of alternative betas. We use stocks in the European STOXX 600 universe to show empirically that the Smart Alpha portfolio dominates many popular European factor investing indexes and smart beta strategies.

Solar Bridge Retrofit System: An innovative solution to renovate structural thermal bridge areas

The structural components of load-bearing concrete frame buildings, such as concrete beams and columns, are critical elements of the facades which often act as a thermal bridge. To reduce the impact of structural thermal bridge areas in non-retrofitted Portuguese residential buildings, a new innovative solar passive retrofit solution, named Solar Bridge Retrofit System (SBRS), is proposed. This concept relies on the principles of unvented Trombe wall systems and consists in using an external transparent skin in front of the structural areas of the envelope in combination with the traditional ETICS in the remaining area. Contrary to the traditional Trombe walls, this innovative design enables the heavy structure of the building to absorb solar radiation and conduct the heat slowly inward or to the adjacent structure.To evaluate the thermal performance of the SBRS, an experimental setup was developed. The field results obtained during February and March 2020 for two different configurations, showed that the double-glazing configuration in combination with ETICS has the potential to improve thermal comfort and reduce energy consumption. This paper addresses both the design of the SBRS and the obtained results from the experimental work.

Diffusion effect on passive solute transport inside an infinite two-dimensional array of vortices

The transport process of solute in a two-dimensional liquid flow is studied. The infinite plane is “covered” by square cells with periodic conditions at its boundaries. The flow is provided by a periodic external force. If the amplitude of the external force reaches a certain critical value, then the flow in each cell contains a pair of vortices. The analysis of the transport of a passive solute in such a flow is investigated in terms of a special flow. In the framework of this approach the transport process is described by mapping functions that determine the coordinates of the particle at the end of the unit cell and the time of passage of the cell as a function of the coordinates at the entrance to the cell. These functions are obtained numerically by the random walk method taking diffusion into account. Using the special flow approach the distribution of an initially uniform distributed ensemble of passive particles with time is calculated for the passage of a long array of the unit cells. It is shown that for tiny values of diffusivity the transport slowing down some particles regarding the ensemble is observed. The speed-up of some particles regarding the ensemble is observed for moderate values of diffusivity and for high diffusivity we obtain the standard diffusion.

RF-3DScan: RFID-based 3D Reconstruction on Tagged Packages

Currently, the logistic industry has introduced 3D reconstruction to monitor the package placement in the warehouse. Previous 3D reconstruction solutions mainly utilize computer vision or sensor-based methods, which are restricted to the line-of-sight or the battery life. Therefore, we propose a passive RFID-based solution, called RF-3DScan, to perform 3D reconstruction on tagged packages, including the package orientation and the package stacking. The basic idea is that a moving antenna can obtain RF-signals from the tags attached on packages with the 1D linear mobile scanning. Through extracting phase differences to build angle profiles for each tag, RF-3DScan derives their relative positions, further determines the package orientation and the coarse-grained package stacking. By simply performing the 2D scanning, RF-3DScan can provide the fine-grained package stacking determination. We implement a prototype system of RF-3DScan and evaluate its performance in real settings. Our experiment results show that RF-3DScan can achieve about 92.5 percent identification accuracy of the bottom face, and an average error about 4.08 $^\circ$ ∘ of the rotation angle. For the package stacking, 1D scanning can achieve the comparable performance in comparison with 2D scanning.

Umicore acquires phosphine-bearing ylide ligands from Ruhr University Bochum

Sound transmission characteristics of panels have been extensively examined which is often quantified by transmission loss. Although acoustic materials are usually applied to passive noise solutions. In the present paper, the influence of sound-absorbing materials on the transmission loss of double-walled panels has been studied theoretically. An analytical method based on statistical energy analysis technique (SEA) is employed for predicting the transmission loss of double-wall steel and aluminum panels. Three commercially available acoustic materials, ie., polyurethane, glass wool, and melamine foam are chosen for investigation.

Passive Heating and Cooling of Photovoltaic Greenhouses Including Thermochromic Materials

The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on the temperature, must be assessed in order to effectively implement this solution. In this study, experimental temperature data were obtained over two years for four structures built with different photovoltaic technologies (mono-crystalline silicon, amorphous silicon, cadmium telluride, and an organic polymeric technology) and fitted to a thermal model in order to provide a comprehensive analysis of their potential utilization as a cover material in greenhouses. Additionally, the thermal effect of color in structures composed of several common construction materials (brick, wood, plasterboard and glass) was quantified and modelled, supplementing the thermal analysis of passive solutions for this application. In all cases, inner and ambient temperature differences of up to +20 °C, created by a passive heating effect during the day, and −5 °C, created by a passive cooling effect during the night, have been observed, suggesting the use of the photovoltaic modules with different degrees of structure coverage, complemented with the color tuning of the modules themselves as passive methods to control the temperature and light spectrum of greenhouses.

A Solute Flux Near a Solid Wall as a Reason for the Observation of Anomalous Transport

The paper is devoted to the study of the reasons of anomalous transport observation in the experiments with microchannels. Usually, retardation of such transport is associated with the interaction of solute particles with channel walls. In the present paper, we have shown that the viscous interaction of the flow and solid wall can be the reason for the anomalous transport observation. It was illustrated on a specific example of a passive solute transport through the channel. The effect of diffusion on such transport was investigated numerically. The power law decline of concentration with respect to time was obtained in a wide range of parameters.

Passive Solar Solutions for Buildings: Criteria and Guidelines for a Synergistic Design

Passive solar system design is an essential asset in a zero-energy building perspective to reduce heating, cooling, lighting, and ventilation loads. The integration of passive systems in building leads to a reduction of plant operation with considerable environmental benefits. The design can be related to intrinsic and extrinsic factors that influence the final performance in a synergistic way. The aim of this paper is to provide a comprehensive view of the elements that influence passive solar systems by means of an analysis of the theoretical background and the synergistic design of various solutions available. The paper quantifies the potential impact of influencing factors on the final performance and then investigates a case study of an existing public building, analyzing the effects of the integration of different passive systems through energy simulations. General investigation has highlighted that latitude and orientation impact energy saving on average by 3–13 and 6–11 percentage points, respectively. The case study showed that almost 20% of the building energy demand can be saved by means of passive solar systems. A higher contribution is given by mixing direct and indirect solutions, as half of the heating and around 25% of the cooling energy demand can be cut off.

Mitigation of sulfation in lead acid battery towards life time extension using ultra capacitor in hybrid electric vehicle

Batteries act as one of the primary sources of energy for high power Hybrid Electric Vehicle (HEV). The life of the battery becomes a significant constraint while building an HEV. So researchers found Lithium-ion batteries are more suitable for HEV with a better lifecycle. But the manufacturing cost of Lithium-ion batteries is expensive. Thus, while designing an economic HEV, the cost of batteries also a constraint. In subsequent years, lead-acid batteries are found one of the best alternatives for lithium-ion. Sulfation is the main problem in lead-acid batteries. So de-sulfation is a solution to recover the sulphated lead-acid battery. But de-sulfation was not found as a better solution for preventing sulfation. Hence battery management system for proper charging or discharge is found as a passive solution for the sulfation. In literature, many methods are reviewed related to proper charging and a discharging controller which may trap in sulfation problem. Hence, this paper, an Atom Search Algorithm (ASA) based Hybrid Energy Storage System (HESS) is designed to enable proper charging and discharging controller for increasing the lifecycles of the lead-acid battery by avoiding sulfation. The lead-acid battery is connected with Ultra-Capacitor (UC) through a bidirectional DC-DC converter to enable proper charging and to discharge of controller in a. The lifetime extension of lead-acid battery is attained by maintaining the proper charging and discharging through the conservation of Depth of Charge (DOC) and State of Charge (SOC). The charging and discharging controller of the lead-acid battery are enabled by a rule-based control strategy in the converter. The optimal operation of the converter is to provide essential supply to meet the load drive cycle as well as battery charging progress. To avoid battery's dry conditions, UC is playing the leading role to supply by the converter. The controller action is performed through the consumption of the Fractional-Order Proportional Integral Derivative Controller (FOPID) in the bidirectional DC-DC converter. The optimal switching operations are selected with the utilisation of the ASA algorithm. The proposed method is implemented in MATLAB/ Simulink and contrasted with existing methods. Finally, the proposed method extends the lifecycles of the battery to 7500 cycles by proper charging and discharging controller.

Comparison of Spectrophotometric Methods for Determination of Iron in Acid Cleaning, and Passivating Stainless Steel Solution by UV-VIS, ICP/MS, and FAAS

Generally, more sophisticated techniques such as, flame atomic absorption (AAS), inductively coupled plasma spectrometer (ICP-MS), and UV/Visible Spectrophotometer were used to determine trace iron metals in pickling (acid cleaning), and passivating stainless steel solutions. Simple and novel spectrophotometric methods are described for simultaneous determination of iron. While these techniques provide excellent sensitivity and selectivity. The results were found to be in satisfactory agreement (shows no significant difference) with those acquired by the flame atomic absorption spectrophotometer (FAAS), UV-Vis Spectrometer, and ICP/MS techniques. The results shows that the concentration of iron are very close each other (less than 5.0%) in the pickling and passivating solutions.

航空多光谱相机三坐标无源定位技术

A large FOV infrared multiple spectrum camera, which contains advance infrared focal plane, acquires large FOV & high resolution multiple spectrum image toward area below the flight vehicle. It takes images on a whole day and nearly a whole whether condition. The multiple spectrum camera system configuration was proposed. Its angular measurement, three coordinate passive location key technology and solution were described in detail. The angular measure electro-circuit & clock synchronization should be finely designed. When the system had been integrated, angular error calibration and compensation, multi-sensor installation attitude calibration were proposed to improve angular measure accuracy and location accuracy. Flight tests shows that image mosaicking accuracy is 10″ which means the technic is effective.

To investigate the influence of sound-absorbing materials on the transmission loss of double-wall panel

Abstract Sound transmission characteristics of panels have been extensively examined which is often quantified by transmission loss. Although acoustic materials are usually applied to passive noise solutions. In the present paper, the influence of sound-absorbing materials on the transmission loss of double-walled panels has been studied theoretically. An analytical method based on statistical energy analysis technique (SEA) is employed for predicting the transmission loss of double-wall steel and aluminum panels. Three commercially available acoustic materials, ie., polyurethane, glass wool, and melamine foam are chosen for investigation.

Bioclimate in Built Environment

The bioclimatic aspects are associated with building environmental performance that makes a building help minimum impact on the environment, attention to human health and safety, minimum energy consumption. The ergonomic design of buildings contributes to maintaining the bioclimatic aspects of the buildings. The study reflects building structure and materials used depend on occupant choices, lifestyle, and economic viability. Therefore, the low-cost mud houses of the coastal regions often follow local practices. The dwelling pattern (two adjacent rooms opening to the corridor) was more prevalent in rural and semiurban areas. The housing exteriors are typical rural locales, commonly comprising agricultural fields, vegetation areas, and ponds. The statistical analysis covering different bioclimatic components, such as transportation availabilities, surrounding environment, and building structure, indicated a significant difference among remote rural, rural and semi-urban residences. The climatic conditions of the four village blocks covered in the study were hot and humid. The component structures provided a basis to explore further the possible influence of additional passive design options in constructing dwellings in coastal rural and semi-urban areas and enhancing thermal comfort. Selective passive design solutions indicate improvements in yearly total thermal comfort hours. Given the viability of poor residents in coastal rural and semi-urban areas, introducing interventions like passive solar direct gain, high thermal mass, night flush, natural and fan-forced ventilation, and evaporative cooling can improve the extent of ~18% in yearly thermal comfort hours. An overall bioclimatic analysis of the rural and semiurban coastal dwellings suggests that some passive design strategies can substantially enhance the thermal comfort of the inhabitants.

Effect of thermochromic coatings on the indoor thermal behavior of a case study building

Passive systems and solutions aimed at improving local thermal comfort conditions represent a cutting-edge research field in building applications. However, only a few investigations were performed by taking into account the local distribution and spatial variability of the airflow generated by the application of both traditional and innovative passive strategies. The present research work is aimed at bridging such gap by modelling the indoor thermal environment of a case study prototype building, i.e. test-room, situated in central Italy, by taking into account the indoor heat transfer phenomena. In particular, a CFD model of the building is elaborated and used to predict the indoor thermal effect of an adaptive thermochromic envelope, compared to more traditional solutions. The simulation results are post-processed in terms of (i) indoor temperature and (ii) indoor airflows. The main findings confirm a non-negligible and positive impact of the thermochromic building envelope on the local indoor thermal comfort conditions in both summer and winter conditions, due to its capability of selectively tailor the absorption of heat gains and a function of the local boundary conditions.

Passive Localization of Moving Target with Channel State Information

With the popularity of wireless networks and smart devices, wireless signal‐based passive target sensing and localization have become a hot research topic and attracted numerous researchers’ interests. The existing passive localization solutions require multiple receivers, which is not practical for real‐world applications. In response to this compelling problem, in this paper, we propose a practical single access point‐based passive moving target localization system. Concretely, it first utilizes multiple antennas of the access point to form an antenna array and extended antenna, to capture channel state information (CSI) at different spatial locations. Then, leveraging the obtained CSI, the signal parameters, including the angle of arrival (AoA) and time of flight (ToF), are estimated. Based on the estimated signal parameters and the locations of the antenna array and extended antenna, finally, the passive localization of the moving target is realized. Comprehensive experiments are conducted under the real‐world scenario with two different test platforms, and the experimental results show the proposed algorithm’s median localization can reach 1.087 m when the number of antennas is 4 and the signal bandwidth is 80 MHz, demonstrating the effectiveness of the proposed algorithm.

Energy Production in Solar Collectors in a University Building Used to Improve the Internal Thermal Conditions in Winter Conditions

In this numerical study the energy production in solar collectors in a University building used to improve the internal thermal conditions is made. Passive and active solutions, using external solar collector and internal thermo-convectors, are used. The numerical simulation, in transient conditions, is done for a winter typical day with clean sky. This numerical study was carried out using a software that simulates the Building Dynamic Response with complex topology in transient conditions. The software evaluates the human thermal comfort and indoor air quality levels that the occupants are subjected, Heated Ventilation and Air Conditioned energy consumption, indoor thermal variables and other parameters. The university building has 107 compartments and is located in a Mediterranean-type environment. External solar water collectors, placed above the building’s roof, and internal thermo-convectors of water/air type, using mixing ventilation, are used as passive and active strategies, respectively. The thermal comfort level, using the Predicted Mean Vote index, and the indoor air quality, using the carbon dioxide concentration, are evaluated. The results show that in winter conditions the solar collectors improve the thermal comfort conditions of the occupants. The indoor air quality, in all ventilated spaces, is also guaranteed.

Lessons from Sustainable and Vernacular Passive Cooling Strategies Used in Traditional Iranian Houses

Passive cooling strategies have long been used in vernacular and traditional architecture practices. Today, with the surge in energy consumption, excessive carbon emissions and lingering climate change challenges, the shift to passive solutions to heat and cool buildings is crucial. Despite this urgency, we heavily rely on electricity and gas to maintain thermal comfort inside buildings. Since heating and cooling accounts for 40% of household energy use, devising passive strategies in housing design can make a significant difference in energy consumption. This paper explores the characteristics of Iranian traditional housing that contribute to making indoor spaces thermally comfortable. The examination of sustainable strategies used in seven case studies in the hot and dry climate of Iran indicates that such measures have a significant impact on the microclimate of traditional houses and considerably reduce the need for electricity and mechanical power. The study suggests that designing tall, north-facing walls, large and shallow pools in the courtyards, multiple openings in the courtyard-facing wall in the same room, stack-cooling for instigating the convective air movement, night purge ventilation, dome ceilings, earth coupling and using thermally massive materials, as well as seasonal relocation across the courtyard are among the most important strategies for mitigating the heat in Iranian houses. Finally, this work puts forward a set of recommendations to improve the passive design of future buildings in hot and arid climates.

Experimental Validation of a Novel Extracellular-Based Source Representation of Acute Myocardial Ischemia.

Electrocardiographic imaging (ECGI) based detection of myocardial ischemia requires an accurate formulation of the source model, which includes a relationship between extracellular and transmembrane potentials (TMPs). In this study, we used high-resolution intramural experimental recordings and forward modeling to examine the relationship between extracellular potentials and TMPs during myocardial ischemia. We measured extracellular electro-grams from intramural plunge needle arrays during seven controlled ischemia episodes in an animal model. We used three TMP source representations: (1) parameterized and distance-based (defined previously), (2) extracellular-based linear transform, and (3) extracellular-based sigmoidal transform. TMPs for each source formulation were then used to compute extracellular potentials by calculating the passive bidomain forward solution throughout the myocardium. We compared measured and computed potentials. Linear and sigmoidal approaches produced improved results compared to the parameterized method. The RMSE, SC, and TC of linear, sigmoidal, and parameterized methods were 0.85 mV, 1.21 mV, and 3.37 mV; 0.91, 0.88, and 0.47; 0.90, 0.77, and 0.33 respectively. We found extracellular-based calculations of TMPs produced superior forward computations compared to parameterized zones.